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2307 lines
93 KiB
C++
2307 lines
93 KiB
C++
// Boost CRC library crc.hpp header file -----------------------------------//
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// Copyright 2001, 2004, 2011 Daryle Walker.
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// Distributed under the Boost Software License, Version 1.0. (See the
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// accompanying file LICENSE_1_0.txt or a copy at
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// <http://www.boost.org/LICENSE_1_0.txt>.)
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// See <http://www.boost.org/libs/crc/> for the library's home page.
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/** \file
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\brief A collection of function templates and class templates that compute
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various forms of Cyclic Redundancy Codes (CRCs).
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\author Daryle Walker
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\version 1.5
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\copyright Boost Software License, version 1.0
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Contains the declarations (and definitions) of various kinds of CRC
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computation functions, function object types, and encapsulated policy types.
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\warning The sample CRC-computer types were just checked against the
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<a href="http://regregex.bbcmicro.net/crc-catalogue.htm">Catalogue of
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parametrised CRC algorithms</a>. New type aliases were added where I got
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a standard wrong. However, the mistaken <code>typedef</code>s are still
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there for backwards compatibility.
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\note There are references to the <i>Rocksoft™ Model CRC
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Algorithm</i>, as described within \"A Painless Guide to CRC Error
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Detection Algorithms,\" linked from \"<a
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href="http://www.ross.net/crc/crcpaper.html">CRC: A Paper On CRCs</a>\" by
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Ross Williams. It will be abbreviated \"RMCA\" in other documentation
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blocks.
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*/
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#ifndef BOOST_CRC_HPP
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#define BOOST_CRC_HPP
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#include <boost/array.hpp> // for boost::array
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#include <boost/config.hpp> // for BOOST_STATIC_CONSTANT, etc.
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#include <boost/cstdint.hpp> // for UINTMAX_C, boost::uintmax_t
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#include <boost/integer.hpp> // for boost::uint_t
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#include <boost/type_traits/conditional.hpp>
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#include <boost/type_traits/integral_constant.hpp>
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#include <climits> // for CHAR_BIT, etc.
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#include <cstddef> // for std::size_t
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#include <boost/limits.hpp> // for std::numeric_limits
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// The type of CRC parameters that can go in a template should be related
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// on the CRC's bit count. This macro expresses that type in a compact
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// form, but also allows an alternate type for compilers that don't support
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// dependent types (in template value-parameters).
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#if !(defined(BOOST_NO_DEPENDENT_TYPES_IN_TEMPLATE_VALUE_PARAMETERS))
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#define BOOST_CRC_PARM_TYPE typename ::boost::uint_t<Bits>::fast
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#else
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#define BOOST_CRC_PARM_TYPE unsigned long
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#endif
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namespace boost
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{
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// Forward declarations ----------------------------------------------------//
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//! Bit-wise CRC computer
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template < std::size_t Bits >
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class crc_basic;
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//! Table-driven CRC computer, usable as a function object
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template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly = 0u,
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BOOST_CRC_PARM_TYPE InitRem = 0u,
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BOOST_CRC_PARM_TYPE FinalXor = 0u, bool ReflectIn = false,
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bool ReflectRem = false >
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class crc_optimal;
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//! Compute the (unaugmented) CRC of a memory block
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template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
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BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
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bool ReflectIn, bool ReflectRem >
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typename uint_t<Bits>::fast crc( void const *buffer,
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std::size_t byte_count);
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//! Compute the CRC of a memory block, with any augmentation provided by user
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template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly >
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typename uint_t<Bits>::fast augmented_crc( void const *buffer,
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std::size_t byte_count,
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typename uint_t<Bits>::fast initial_remainder = 0u);
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//! Computation type for ARC|CRC-16|CRC-IBM|CRC-16/ARC|CRC-16/LHA standard
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typedef crc_optimal<16, 0x8005, 0, 0, true, true> crc_16_type;
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//! Computation type for CRC-16/CCITT-FALSE standard
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typedef crc_optimal<16, 0x1021, 0xFFFF, 0, false, false> crc_ccitt_false_t;
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//! Computation type for the CRC mistakenly called the CCITT standard
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typedef crc_ccitt_false_t crc_ccitt_type;
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//! Computation type for the actual
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//! KERMIT|CRC-16/CCITT|CRC-16/CCITT-TRUE|CRC-CCITT standard
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typedef crc_optimal<16, 0x1021, 0, 0, true, true> crc_ccitt_true_t;
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//! Computation type that I mistakenly called the XMODEM standard; it inverts
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//! both reflection parameters and reflects the truncated divisor (Don't use?!)
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typedef crc_optimal<16, 0x8408, 0, 0, true, true> crc_xmodem_type;
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//! Computation type for the actual XMODEM|ZMODEM|CRC-16/ACORN standard
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typedef crc_optimal<16, 0x1021, 0, 0, false, false> crc_xmodem_t;
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//! Computation type for CRC-32|CRC-32/ADCCP|PKZIP standard
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typedef crc_optimal<32, 0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true, true>
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crc_32_type;
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// Forward declarations for implementation detail stuff --------------------//
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// (Just for the stuff that will be needed for the next two sections)
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//! \cond
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namespace detail
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{
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//! Mix-in class to add a possibly-reflecting member function
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template < int BitLength, bool DoIt, int Id = 0 >
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class possible_reflector;
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//! Mix-in class for byte-fed, table-driven CRC algorithms
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template < int Order, boost::uintmax_t TruncatedPolynomial, bool Reflect,
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int Id = 0 >
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class crc_driver;
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} // namespace detail
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//! \endcond
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// Simple cyclic redundancy code (CRC) class declaration -------------------//
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/** Objects of this type compute the CRC checksum of submitted data, where said
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data can be entered piecemeal through several different kinds of groupings.
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Modulo-2 polynomial division steps are always performed bit-wise, without
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the use of pre-computation tables. Said division uses the altered
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algorithm, so any data has to be unaugmented.
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\pre 0 \< \a Bits \<= \c std\::numeric_limits\<uintmax_t\>\::digits
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\tparam Bits The order of the modulo-2 polynomial divisor. (\e Width from
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the RMCA)
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*/
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template < std::size_t Bits >
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class crc_basic
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{
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public:
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// Type
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/** \brief The register type used for computations
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This type is used for CRC calculations and is the type for any returned
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checksums and returned or submitted remainders, (truncated) divisors, or
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XOR masks. It is a built-in unsigned integer type.
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*/
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typedef typename boost::uint_t<Bits>::fast value_type;
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// Constant for the template parameter
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//! A copy of \a Bits provided for meta-programming purposes
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BOOST_STATIC_CONSTANT( std::size_t, bit_count = Bits );
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// Constructor (use the automatic copy-ctr, move-ctr, and dtr)
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//! Create a computer, separately listing each needed parameter
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explicit crc_basic( value_type truncated_polynomial,
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value_type initial_remainder = 0, value_type final_xor_value = 0,
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bool reflect_input = false, bool reflect_remainder = false );
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// Internal Operations
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//! Return the (truncated) polynomial divisor
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value_type get_truncated_polynominal() const;
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//! Return what the polynomial remainder was set to during construction
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value_type get_initial_remainder() const;
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//! Return the XOR-mask used during output processing
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value_type get_final_xor_value() const;
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//! Check if input-bytes will be reflected before processing
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bool get_reflect_input() const;
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//! Check if the remainder will be reflected during output processing
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bool get_reflect_remainder() const;
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//! Return the remainder based from already-processed bits
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value_type get_interim_remainder() const;
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//! Change the interim remainder to a new value
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void reset( value_type new_rem );
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//! Change the interim remainder back to the initial value
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void reset();
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// External Operations
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//! Submit a single bit for input processing
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void process_bit( bool bit );
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//! Submit the lowest \a bit_length bits of a byte for input processing
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void process_bits( unsigned char bits, std::size_t bit_length );
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//! Submit a single byte for input processing
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void process_byte( unsigned char byte );
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//! Submit a memory block for input processing, iterator-pair style
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void process_block( void const *bytes_begin, void const *bytes_end );
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//! Submit a memory block for input processing, pointer-and-size style
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void process_bytes( void const *buffer, std::size_t byte_count );
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//! Return the checksum of the already-processed bits
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value_type checksum() const;
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private:
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// Member data
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value_type rem_;
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value_type poly_, init_, final_; // non-const to allow assignability
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bool rft_in_, rft_out_; // non-const to allow assignability
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}; // boost::crc_basic
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// Optimized cyclic redundancy code (CRC) class declaration ----------------//
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/** Objects of this type compute the CRC checksum of submitted data, where said
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data can be entered piecemeal through several different kinds of groupings.
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Modulo-2 polynomial division steps are performed byte-wise, aided by the use
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of pre-computation tables. Said division uses the altered algorithm, so any
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data has to be unaugmented.
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\pre 0 \< \a Bits \<= \c std\::numeric_limits\<uintmax_t\>\::digits
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\tparam Bits The order of the modulo-2 polynomial divisor. (\e Width from
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the RMCA)
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\tparam TruncPoly The lowest coefficients of the divisor polynomial. The
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highest-order coefficient is omitted and always assumed to be 1. Defaults
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to \c 0, i.e. the only non-zero term is the implicit one for
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x<sup><var>Bits</var></sup>. (\e Poly from the RMCA)
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\tparam InitRem The (unaugmented) initial state of the polynomial
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remainder. Defaults to \c 0 if omitted. (\e Init from the RMCA)
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\tparam FinalXor The (XOR) bit-mask to be applied to the output remainder,
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after possible reflection but before returning. Defaults to \c 0 (i.e. no
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bit changes) if omitted. (\e XorOut from the RMCA)
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\tparam ReflectIn If \c true, input bytes are read lowest-order bit first,
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otherwise highest-order bit first. Defaults to \c false if omitted.
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(\e RefIn from the RMCA)
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\tparam ReflectRem If \c true, the output remainder is reflected before the
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XOR-mask. Defaults to \c false if omitted. (\e RefOut from the RMCA)
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\todo Get rid of the default value for \a TruncPoly. Choosing a divisor is
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an important decision with many factors, so a default is never useful,
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especially a bad one.
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*/
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template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
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BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
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bool ReflectIn, bool ReflectRem >
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class crc_optimal
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{
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public:
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// Type
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//! \copydoc boost::crc_basic::value_type
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typedef typename boost::uint_t<Bits>::fast value_type;
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// Constants for the template parameters
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//! \copydoc boost::crc_basic::bit_count
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BOOST_STATIC_CONSTANT( std::size_t, bit_count = Bits );
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//! A copy of \a TruncPoly provided for meta-programming purposes
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BOOST_STATIC_CONSTANT( value_type, truncated_polynominal = TruncPoly );
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//! A copy of \a InitRem provided for meta-programming purposes
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BOOST_STATIC_CONSTANT( value_type, initial_remainder = InitRem );
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//! A copy of \a FinalXor provided for meta-programming purposes
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BOOST_STATIC_CONSTANT( value_type, final_xor_value = FinalXor );
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//! A copy of \a ReflectIn provided for meta-programming purposes
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BOOST_STATIC_CONSTANT( bool, reflect_input = ReflectIn );
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//! A copy of \a ReflectRem provided for meta-programming purposes
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BOOST_STATIC_CONSTANT( bool, reflect_remainder = ReflectRem );
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// Constructor (use the automatic copy-ctr, move-ctr, and dtr)
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//! Create a computer, giving an initial remainder if desired
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explicit crc_optimal( value_type init_rem = initial_remainder );
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// Internal Operations
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//! \copybrief boost::crc_basic::get_truncated_polynominal
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value_type get_truncated_polynominal() const;
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//! \copybrief boost::crc_basic::get_initial_remainder
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value_type get_initial_remainder() const;
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//! \copybrief boost::crc_basic::get_final_xor_value
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value_type get_final_xor_value() const;
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//! \copybrief boost::crc_basic::get_reflect_input
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bool get_reflect_input() const;
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//! \copybrief boost::crc_basic::get_reflect_remainder
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bool get_reflect_remainder() const;
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//! \copybrief boost::crc_basic::get_interim_remainder
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value_type get_interim_remainder() const;
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//! Change the interim remainder to either a given value or the initial one
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void reset( value_type new_rem = initial_remainder );
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// External Operations
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//! \copybrief boost::crc_basic::process_byte
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void process_byte( unsigned char byte );
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//! \copybrief boost::crc_basic::process_block
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void process_block( void const *bytes_begin, void const *bytes_end );
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//! \copybrief boost::crc_basic::process_bytes
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void process_bytes( void const *buffer, std::size_t byte_count );
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//! \copybrief boost::crc_basic::checksum
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value_type checksum() const;
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// Operators
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//! Submit a single byte for input processing, suitable for the STL
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void operator ()( unsigned char byte );
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//! Return the checksum of the already-processed bits, suitable for the STL
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value_type operator ()() const;
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private:
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// Implementation types
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// (Processing for reflected input gives reflected remainders, so you only
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// have to apply output-reflection if Reflect-Remainder doesn't match
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// Reflect-Input.)
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typedef detail::possible_reflector<Bits, ReflectIn> reflect_i_type;
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typedef detail::crc_driver<Bits, TruncPoly, ReflectIn> crc_table_type;
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typedef detail::possible_reflector<Bits, ReflectRem != ReflectIn>
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reflect_o_type;
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// Member data
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value_type rem_;
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}; // boost::crc_optimal
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// Implementation detail stuff ---------------------------------------------//
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//! \cond
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namespace detail
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{
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/** \brief Meta-programming integral constant for a single-bit bit-mask
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Generates a compile-time constant for a bit-mask that affects a single
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bit. The \c value will be 2<sup><var>BitIndex</var></sup>. The \c type
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will be the smallest built-in unsigned integer type that can contain the
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value, unless there's a built-in type that the system can handle easier,
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then the \c type will be smallest fast-handled unsigned integer type.
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\pre 0 \<= BitIndex \< \c std\::numeric_limits\<uintmax_t\>\::digits
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\tparam BitIndex The place of the sole set bit.
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*/
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template < int BitIndex >
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struct high_bit_mask_c
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: boost::integral_constant<typename boost::uint_t< BitIndex + 1 >::fast,
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( UINTMAX_C(1) << BitIndex )>
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{};
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/** \brief Meta-programming integral constant for a lowest-bits bit-mask
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Generates a compile-time constant for a bit-mask that affects the lowest
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bits. The \c value will be 2<sup><var>BitCount</var></sup> - 1. The
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\c type will be the smallest built-in unsigned integer type that can
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contain the value, unless there's a built-in type that the system can
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handle easier, then the \c type will be smallest fast-handled unsigned
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integer type.
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\pre 0 \<= BitCount \<= \c std\::numeric_limits\<uintmax_t\>\::digits
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\tparam BitCount The number of lowest-placed bits set.
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*/
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template < int BitCount >
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struct low_bits_mask_c
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: boost::integral_constant<typename boost::uint_t< BitCount >::fast, (
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BitCount ? (( (( UINTMAX_C(1) << (BitCount - 1) ) - 1u) << 1 ) |
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UINTMAX_C( 1 )) : 0u )>
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{};
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/** \brief Reflects the bits of a number
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Reverses the order of the given number of bits within a value. For
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instance, if the given reflect count is 5, then the bit values for the
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16- and 1-place will switch and the 8- and 2-place will switch, leaving
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the other bits alone. (The 4-place bit is in the middle, so it wouldn't
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change.)
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\pre \a Unsigned is a built-in unsigned integer type
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\pre 0 \< word_length \<= \c std\::numeric_limits\<Unsigned\>\::digits
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\tparam Unsigned The type of \a x.
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\param x The value to be (partially) reflected.
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\param word_length The number of low-order bits to reflect. Defaults
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to the total number of value bits in \a Unsigned.
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\return The (partially) reflected value.
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\todo Check if this is the fastest way.
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*/
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template < typename Unsigned >
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Unsigned reflect_unsigned( Unsigned x, int word_length
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= std::numeric_limits<Unsigned>::digits )
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{
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for ( Unsigned l = 1u, h = l << (word_length - 1) ; h > l ; h >>= 1, l
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<<= 1 )
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{
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Unsigned const m = h | l, t = x & m;
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if ( (t == h) || (t == l) )
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x ^= m;
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}
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return x;
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}
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/** \brief Make a byte-to-byte-reflection map
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Creates a mapping array so the results can be cached. Uses
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#reflect_unsigned to generate the element values.
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\return An array <var>a</var> such that, for a given byte value
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<var>i</var>, <code><var>a</var>[ <var>i</var> ]</code> resolves to
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the reflected value of <var>i</var>.
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*/
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boost::array< unsigned char, (UINTMAX_C( 1 ) << CHAR_BIT) >
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inline make_byte_reflection_table()
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{
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boost::array<unsigned char, ( UINTMAX_C(1) << CHAR_BIT )> result;
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unsigned char i = 0u;
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do
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result[ i ] = reflect_unsigned( i );
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while ( ++i );
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return result;
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}
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/** \brief Reflects the bits of a single byte
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Reverses the order of all the bits within a value. For instance, the
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bit values for the 2<sup><code>CHAR_BIT</code> - 1</sup>- and 1-place
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will switch and the 2<sup><code>CHAR_BIT</code> - 2</sup>- and 2-place
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will switch, etc.
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\param x The byte value to be reflected.
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\return The reflected value.
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\note Since this could be the most common type of reflection, and the
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number of states is relatively small, the implementation pre-computes
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and uses a table of all the results.
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*/
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inline unsigned char reflect_byte( unsigned char x )
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{
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static boost::array<unsigned char, ( UINTMAX_C(1) << CHAR_BIT )> const
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table = make_byte_reflection_table();
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return table[ x ];
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}
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/** \brief Reflects some bits within a single byte
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Like #reflect_unsigned, except it takes advantage of any (long-term)
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speed gains #reflect_byte may bring.
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\pre 0 \< \a word_length \<= \c CHAR_BIT
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\param x The value to be (partially) reflected.
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\param word_length The number of low-order bits to reflect.
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\return The (partially) reflected value.
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*/
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inline unsigned char reflect_sub_byte( unsigned char x, int word_length )
|
|
{ return reflect_byte(x) >> (CHAR_BIT - word_length); }
|
|
|
|
/** \brief Possibly reflects the bits of a number
|
|
|
|
Reverses the order of the given number of bits within a value. For
|
|
instance, if the given reflect count is 5, then the bit values for the
|
|
16- and 1-place will switch and the 8- and 2-place will switch, leaving
|
|
the other bits alone. (The 4-place bit is in the middle, so it wouldn't
|
|
change.) This variant function allows the reflection be controlled by
|
|
an extra parameter, in case the decision to use reflection is made at
|
|
run-time.
|
|
|
|
\pre \a Unsigned is a built-in unsigned integer type
|
|
\pre 0 \< word_length \<= \c std\::numeric_limits\<Unsigned\>\::digits
|
|
|
|
\tparam Unsigned The type of \a x.
|
|
|
|
\param x The value to be (partially) reflected.
|
|
\param reflect Controls whether \a x is actually reflected (\c true) or
|
|
left alone (\c false).
|
|
\param word_length The number of low-order bits to reflect. Defaults
|
|
to the total number of value bits in \a Unsigned.
|
|
|
|
\return The possibly (partially) reflected value.
|
|
*/
|
|
template < typename Unsigned >
|
|
inline
|
|
Unsigned reflect_optionally( Unsigned x, bool reflect, int word_length
|
|
= std::numeric_limits<Unsigned>::digits )
|
|
{ return reflect ? reflect_unsigned(x, word_length) : x; }
|
|
|
|
/** \brief Possibly reflects the bits of a single byte
|
|
|
|
Uses #reflect_byte (if \a reflect is \c true).
|
|
|
|
\param x The byte value to be (possibly) reflected.
|
|
\param reflect Whether (\c true) or not (\c false) \a x is reflected.
|
|
|
|
\return <code><var>reflect</var> ? reflect_byte(<var>x</var>) :
|
|
<var>x</var></code>
|
|
*/
|
|
inline
|
|
unsigned char reflect_byte_optionally( unsigned char x, bool reflect )
|
|
{ return reflect ? reflect_byte(x) : x; }
|
|
|
|
/** \brief Update a CRC remainder by several bits, assuming a non-augmented
|
|
message
|
|
|
|
Performs several steps of division required by the CRC algorithm, giving
|
|
a new remainder polynomial based on the divisor polynomial and the
|
|
synthesized dividend polynomial (from the old remainder and the
|
|
newly-provided input). The computations assume that the CRC is directly
|
|
exposed from the remainder, without any zero-valued bits augmented to
|
|
the message bits.
|
|
|
|
\pre \a Register and \a Word are both built-in unsigned integer types
|
|
\pre 0 \< \a register_length \<= std\::numeric_limits\<\a Register\>
|
|
\::digits
|
|
\pre 0 \< \a word_length \<= std\::numeric_limits\<\a Word\>\::digits
|
|
|
|
\tparam Register The type used for representing the remainder and
|
|
divisor modulo-2 polynomials. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i>.
|
|
\tparam Word The type used for storing the incoming terms of the
|
|
dividend modulo-2 polynomial. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i> when \a reflect is
|
|
\c false, and the coefficient of <i>x<sup><var>word_length</var> - 1 -
|
|
i</sup></i> otherwise.
|
|
|
|
\param[in] register_length The number of significant low-order bits
|
|
to be used from \a Register values. It is the order of the modulo-2
|
|
polynomial remainder and one less than the divisor's order.
|
|
\param[in,out] remainder The upper part of the dividend polynomial
|
|
before division, and the remainder polynomial after.
|
|
\param[in] new_dividend_bits The coefficients for the next
|
|
\a word_length lowest terms of the dividend polynomial.
|
|
\param[in] truncated_divisor The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\param[in] word_length The number of lowest-order bits to read from
|
|
\a new_dividend_bits.
|
|
\param[in] reflect If \c false, read from the highest-order marked
|
|
bit from \a new_dividend_bits and go down, as normal. Otherwise,
|
|
proceed from the lowest-order bit and go up.
|
|
|
|
\note This routine performs a modulo-2 polynomial division variant.
|
|
The exclusive-or operations are applied in a different order, since
|
|
that kind of operation is commutative and associative. It also
|
|
assumes that the zero-valued augment string was applied before this
|
|
step, which means that the updated remainder can be directly used as
|
|
the final CRC.
|
|
*/
|
|
template < typename Register, typename Word >
|
|
void crc_modulo_word_update( int register_length, Register &remainder, Word
|
|
new_dividend_bits, Register truncated_divisor, int word_length, bool
|
|
reflect )
|
|
{
|
|
// Create this masking constant outside the loop.
|
|
Register const high_bit_mask = UINTMAX_C(1) << (register_length - 1);
|
|
|
|
// The natural reading order for division is highest digit/bit first.
|
|
// The "reflect" parameter switches this. However, building a bit mask
|
|
// for the lowest bit is the easiest....
|
|
new_dividend_bits = reflect_optionally( new_dividend_bits, !reflect,
|
|
word_length );
|
|
|
|
// Perform modulo-2 division for each new dividend input bit
|
|
for ( int i = word_length ; i ; --i, new_dividend_bits >>= 1 )
|
|
{
|
|
// compare the new bit with the remainder's highest
|
|
remainder ^= ( new_dividend_bits & 1u ) ? high_bit_mask : 0u;
|
|
|
|
// perform modulo-2 division
|
|
bool const quotient = remainder & high_bit_mask;
|
|
|
|
remainder <<= 1;
|
|
remainder ^= quotient ? truncated_divisor : 0u;
|
|
|
|
// The quotient isn't used for anything, so don't keep it.
|
|
}
|
|
}
|
|
|
|
/** \brief Update a CRC remainder by a single bit, assuming a non-augmented
|
|
message
|
|
|
|
Performs the next step of division required by the CRC algorithm, giving
|
|
a new remainder polynomial based on the divisor polynomial and the
|
|
synthesized dividend polynomial (from the old remainder and the
|
|
newly-provided input). The computations assume that the CRC is directly
|
|
exposed from the remainder, without any zero-valued bits augmented to
|
|
the message bits.
|
|
|
|
\pre \a Register is a built-in unsigned integer type
|
|
\pre 0 \< \a register_length \<= std\::numeric_limits\<\a Register\>
|
|
\::digits
|
|
|
|
\tparam Register The type used for representing the remainder and
|
|
divisor modulo-2 polynomials. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i>.
|
|
|
|
\param[in] register_length The number of significant low-order bits
|
|
to be used from \a Register values. It is the order of the modulo-2
|
|
polynomial remainder and one less than the divisor's order.
|
|
\param[in,out] remainder The upper part of the dividend polynomial
|
|
before division, and the remainder polynomial after.
|
|
\param[in] new_dividend_bit The coefficient for the constant term
|
|
of the dividend polynomial.
|
|
\param[in] truncated_divisor The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
|
|
\note This routine performs a modulo-2 polynomial division variant.
|
|
The exclusive-or operations are applied in a different order, since
|
|
that kind of operation is commutative and associative. It also
|
|
assumes that the zero-valued augment string was applied before this
|
|
step, which means that the updated remainder can be directly used as
|
|
the final CRC.
|
|
*/
|
|
template < typename Register >
|
|
inline void crc_modulo_update( int register_length, Register &remainder,
|
|
bool new_dividend_bit, Register truncated_divisor )
|
|
{
|
|
crc_modulo_word_update( register_length, remainder,
|
|
static_cast<unsigned>(new_dividend_bit), truncated_divisor, 1, false );
|
|
}
|
|
|
|
/** \brief Update a CRC remainder by several bits, assuming an augmented
|
|
message
|
|
|
|
Performs several steps of division required by the CRC algorithm, giving
|
|
a new remainder polynomial based on the divisor polynomial and the
|
|
synthesized dividend polynomial (from the old remainder and the
|
|
newly-provided input). The computations assume that a zero-valued
|
|
string of bits will be appended to the message before extracting the
|
|
CRC.
|
|
|
|
\pre \a Register and \a Word are both built-in unsigned integer types
|
|
\pre 0 \< \a register_length \<= std\::numeric_limits\<\a Register\>
|
|
\::digits
|
|
\pre 0 \< \a word_length \<= std\::numeric_limits\<\a Word\>\::digits
|
|
|
|
\tparam Register The type used for representing the remainder and
|
|
divisor modulo-2 polynomials. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i>.
|
|
\tparam Word The type used for storing the incoming terms of the
|
|
dividend modulo-2 polynomial. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i> when \a reflect is
|
|
\c false, and the coefficient of <i>x<sup><var>word_length</var> - 1 -
|
|
i</sup></i> otherwise.
|
|
|
|
\param[in] register_length The number of significant low-order bits
|
|
to be used from \a Register values. It is the order of the modulo-2
|
|
polynomial remainder and one less than the divisor's order.
|
|
\param[in,out] remainder The upper part of the dividend polynomial
|
|
before division, and the remainder polynomial after.
|
|
\param[in] new_dividend_bits The coefficients for the next
|
|
\a word_length lowest terms of the dividend polynomial.
|
|
\param[in] truncated_divisor The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\param[in] word_length The number of lowest-order bits to read from
|
|
\a new_dividend_bits.
|
|
\param[in] reflect If \c false, read from the highest-order marked
|
|
bit from \a new_dividend_bits and go down, as normal. Otherwise,
|
|
proceed from the lowest-order bit and go up.
|
|
|
|
\note This routine performs straight-forward modulo-2 polynomial
|
|
division. It assumes that an augment string will be processed at the
|
|
end of the message bits before doing CRC analysis.
|
|
\todo Use this function somewhere so I can test it.
|
|
*/
|
|
template < typename Register, typename Word >
|
|
void augmented_crc_modulo_word_update( int register_length, Register
|
|
&remainder, Word new_dividend_bits, Register truncated_divisor, int
|
|
word_length, bool reflect )
|
|
{
|
|
// Create this masking constant outside the loop.
|
|
Register const high_bit_mask = UINTMAX_C(1) << (register_length - 1);
|
|
|
|
// The natural reading order for division is highest digit/bit first.
|
|
// The "reflect" parameter switches this. However, building a bit mask
|
|
// for the lowest bit is the easiest....
|
|
new_dividend_bits = reflect_optionally( new_dividend_bits, not reflect,
|
|
word_length );
|
|
|
|
// Perform modulo-2 division for each new dividend input bit
|
|
for ( int i = word_length ; i ; --i, new_dividend_bits >>= 1 )
|
|
{
|
|
bool const quotient = remainder & high_bit_mask;
|
|
|
|
remainder <<= 1;
|
|
remainder |= new_dividend_bits & 1u;
|
|
remainder ^= quotient ? truncated_divisor : 0u;
|
|
|
|
// The quotient isn't used for anything, so don't keep it.
|
|
}
|
|
}
|
|
|
|
/** \brief Update a CRC remainder by a single bit, assuming an augmented
|
|
message
|
|
|
|
Performs the next step of division required by the CRC algorithm, giving
|
|
a new remainder polynomial based on the divisor polynomial and the
|
|
synthesized dividend polynomial (from the old remainder and the
|
|
newly-provided input). The computations assume that a zero-valued
|
|
string of bits will be appended to the message before extracting the
|
|
CRC.
|
|
|
|
\pre \a Register is a built-in unsigned integer type
|
|
\pre 0 \< \a register_length \<= std\::numeric_limits\<\a Register\>
|
|
\::digits
|
|
|
|
\tparam Register The type used for representing the remainder and
|
|
divisor modulo-2 polynomials. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i>.
|
|
|
|
\param[in] register_length The number of significant low-order bits
|
|
to be used from \a Register values. It is the order of the modulo-2
|
|
polynomial remainder and one less than the divisor's order.
|
|
\param[in,out] remainder The upper part of the dividend polynomial
|
|
before division, and the remainder polynomial after.
|
|
\param[in] new_dividend_bit The coefficient for the constant term
|
|
of the dividend polynomial.
|
|
\param[in] truncated_divisor The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
|
|
\note This routine performs straight-forward modulo-2 polynomial
|
|
division. It assumes that an augment string will be processed at the
|
|
end of the message bits before doing CRC analysis.
|
|
\todo Use this function somewhere so I can test it.
|
|
*/
|
|
template < typename Register >
|
|
inline void augmented_crc_modulo_update( int register_length, Register
|
|
&remainder, bool new_dividend_bit, Register truncated_divisor )
|
|
{
|
|
augmented_crc_modulo_word_update( register_length, remainder,
|
|
static_cast<unsigned>(new_dividend_bit), truncated_divisor, 1, false );
|
|
}
|
|
|
|
/** \brief A mix-in class that returns its argument
|
|
|
|
This class template makes a function object that returns its argument
|
|
as-is. It's one case for #possible_reflector.
|
|
|
|
\pre 0 \< \a BitLength \<= \c std\::numeric_limits\<uintmax_t\>
|
|
\::digits
|
|
|
|
\tparam BitLength How many significant bits arguments have.
|
|
*/
|
|
template < int BitLength >
|
|
class non_reflector
|
|
{
|
|
public:
|
|
/** \brief The type to check for specialization
|
|
|
|
This is a Boost integral constant indicating that this class
|
|
does not reflect its input values.
|
|
*/
|
|
typedef boost::false_type is_reflecting_type;
|
|
/** \brief The type to check for register bit length
|
|
|
|
This is a Boost integral constant indicating how many
|
|
significant bits won't actually be reflected.
|
|
*/
|
|
typedef boost::integral_constant< int, BitLength > width_c;
|
|
/** \brief The type of (not-)reflected values
|
|
|
|
This type is the input and output type for the (possible-)
|
|
reflection function, which does nothing here.
|
|
*/
|
|
typedef typename boost::uint_t< BitLength >::fast value_type;
|
|
|
|
/** \brief Does nothing
|
|
|
|
Returns the given value, not reflecting any part of it.
|
|
|
|
\param x The value to not be reflected.
|
|
|
|
\return \a x
|
|
*/
|
|
inline static value_type reflect_q( value_type x )
|
|
{ return x; }
|
|
};
|
|
|
|
/** \brief A mix-in class that reflects (the lower part of) its argument,
|
|
generally for types larger than a byte
|
|
|
|
This class template makes a function object that returns its argument
|
|
after reflecting its lower-order bits. It's one sub-case for
|
|
#possible_reflector.
|
|
|
|
\pre \c CHAR_BIT \< \a BitLength \<= \c std\::numeric_limits\<uintmax_t
|
|
\>\::digits
|
|
|
|
\tparam BitLength How many significant bits arguments have.
|
|
*/
|
|
template < int BitLength >
|
|
class super_byte_reflector
|
|
{
|
|
public:
|
|
/** \brief The type to check for specialization
|
|
|
|
This is a Boost integral constant indicating that this class
|
|
does reflect its input values.
|
|
*/
|
|
typedef boost::true_type is_reflecting_type;
|
|
/** \brief The type to check for register bit length
|
|
|
|
This is a Boost integral constant indicating how many
|
|
significant bits will be reflected.
|
|
*/
|
|
typedef boost::integral_constant< int, BitLength > width_c;
|
|
/** \brief The type of reflected values
|
|
|
|
This is both the input and output type for the reflection function.
|
|
*/
|
|
typedef typename boost::uint_t< BitLength >::fast value_type;
|
|
|
|
/** \brief Reflect (part of) the given value
|
|
|
|
Reverses the order of the given number of bits within a value,
|
|
using #reflect_unsigned.
|
|
|
|
\param x The value to be (partially) reflected.
|
|
|
|
\return ( <var>x</var> &
|
|
~(2<sup><var>width_c</var>\::value</sup> - 1) ) | REFLECT(
|
|
<var>x</var> & (2<sup><var>width_c</var>\::value</sup> -
|
|
1) )
|
|
*/
|
|
inline static value_type reflect_q( value_type x )
|
|
{ return reflect_unsigned(x, width_c::value); }
|
|
};
|
|
|
|
/** \brief A mix-in class that reflects (the lower part of) its argument,
|
|
generally for bytes
|
|
|
|
This class template makes a function object that returns its argument
|
|
after reflecting its lower-order bits. It's one sub-case for
|
|
#possible_reflector.
|
|
|
|
\pre 0 \< \a BitLength \<= \c CHAR_BIT
|
|
|
|
\tparam BitLength How many significant bits arguments have.
|
|
*/
|
|
template < int BitLength >
|
|
class sub_type_reflector
|
|
{
|
|
public:
|
|
/** \brief The type to check for specialization
|
|
|
|
This is a Boost integral constant indicating that this class
|
|
does reflect its input values.
|
|
*/
|
|
typedef boost::true_type is_reflecting_type;
|
|
/** \brief The type to check for register bit length
|
|
|
|
This is a Boost integral constant indicating how many
|
|
significant bits will be reflected.
|
|
*/
|
|
typedef boost::integral_constant< int, BitLength > width_c;
|
|
/** \brief The type of reflected values
|
|
|
|
This is both the input and output type for the reflection function.
|
|
*/
|
|
typedef unsigned char value_type;
|
|
|
|
/** \brief Reflect (part of) the given value
|
|
|
|
Reverses the order of the given number of bits within a value,
|
|
using #reflect_sub_byte.
|
|
|
|
\param x The value to be (partially) reflected.
|
|
|
|
\return ( <var>x</var> &
|
|
~(2<sup><var>width_c</var>\::value</sup> - 1) ) | REFLECT(
|
|
<var>x</var> & (2<sup><var>width_c</var>\::value</sup> -
|
|
1) )
|
|
*/
|
|
inline static value_type reflect_q( value_type x )
|
|
{ return reflect_sub_byte(x, width_c::value); }
|
|
};
|
|
|
|
/** \brief A mix-in class that reflects (the lower part of) its argument
|
|
|
|
This class template makes a function object that returns its argument
|
|
after reflecting its lower-order bits. It's one case for
|
|
#possible_reflector.
|
|
|
|
\pre 0 \< \a BitLength \<= \c std\::numeric_limits\<uintmax_t\>
|
|
\::digits
|
|
|
|
\tparam BitLength How many significant bits arguments have.
|
|
*/
|
|
template < int BitLength >
|
|
class reflector
|
|
: public boost::conditional< (BitLength > CHAR_BIT),
|
|
super_byte_reflector<BitLength>, sub_type_reflector<BitLength> >::type
|
|
{ };
|
|
|
|
/** This class template adds a member function #reflect_q that will
|
|
conditionally reflect its first argument, controlled by a compile-time
|
|
parameter.
|
|
|
|
\pre 0 \< \a BitLength \<= \c std\::numeric_limits\<uintmax_t\>
|
|
\::digits
|
|
|
|
\tparam BitLength How many significant bits arguments have.
|
|
\tparam DoIt \c true if #reflect_q will reflect, \c false if it should
|
|
return its argument unchanged.
|
|
\tparam Id An extra differentiator if multiple copies of this class
|
|
template are mixed-in as base classes. Defaults to 0 if omitted.
|
|
*/
|
|
template < int BitLength, bool DoIt, int Id >
|
|
class possible_reflector
|
|
: public boost::conditional< DoIt, reflector<BitLength>,
|
|
non_reflector<BitLength> >::type
|
|
{
|
|
public:
|
|
/** \brief The type to check for ID
|
|
|
|
This is a Boost integral constant indicating what ID number this
|
|
instantiation used.
|
|
*/
|
|
typedef boost::integral_constant<int, Id> id_type;
|
|
};
|
|
|
|
/** \brief Find the composite remainder update effect from a fixed bit
|
|
sequence, for each potential sequence combination.
|
|
|
|
For each value between 0 and 2<sup><var>SubOrder</var></sup> - 1,
|
|
computes the XOR mask corresponding to the composite effect they update
|
|
the incoming remainder, which is the upper part of the dividend that
|
|
gets (partially) pushed out of its register by the incoming value's
|
|
bits. The composite value merges the \"partial products\" from each bit
|
|
of the value being updated individually.
|
|
|
|
\pre \a Register is a built-in unsigned integer type
|
|
\pre 0 \< \a SubOrder \<= \a register_length \<=
|
|
std\::numeric_limits\<\a Register\>\::digits
|
|
|
|
\tparam SubOrder The number of low-order significant bits of the trial
|
|
new dividends.
|
|
\tparam Register The type used for representing the remainder and
|
|
divisor modulo-2 polynomials. The bit at <code>2<sup>i</sup></code>
|
|
is used as the coefficient of <i>x<sup>i</sup></i>.
|
|
|
|
\param[in] register_length The number of significant low-order bits
|
|
to be used from \a Register values. It is the order of the modulo-2
|
|
polynomial remainder and one less than the divisor's order.
|
|
\param[in] truncated_divisor The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\param[in] reflect If \c false, read from the highest-order marked
|
|
bit from a new dividend's bits and go down, as normal. Otherwise,
|
|
proceed from the lowest-order bit and go up.
|
|
|
|
\return An array such that the element at index <var>i</var> is the
|
|
composite effect XOR mask for value <var>i</var>.
|
|
|
|
\note This routine performs a modulo-2 polynomial division variant.
|
|
The exclusive-or operations are applied in a different order, since
|
|
that kind of operation is commutative and associative. It also
|
|
assumes that the zero-valued augment string was applied before this
|
|
step, which means that the updated remainder can be directly used as
|
|
the final CRC.
|
|
\todo Check that using the unaugmented-CRC division routines give the
|
|
same composite mask table as using augmented-CRC routines.
|
|
*/
|
|
template < int SubOrder, typename Register >
|
|
boost::array< Register, (UINTMAX_C( 1 ) << SubOrder) >
|
|
make_partial_xor_products_table( int register_length, Register
|
|
truncated_divisor, bool reflect )
|
|
{
|
|
boost::array<Register, ( UINTMAX_C(1) << SubOrder )> result;
|
|
|
|
// Loop over every possible dividend value
|
|
for ( typename boost::uint_t<SubOrder + 1>::fast dividend = 0u;
|
|
dividend < result.size() ; ++dividend )
|
|
{
|
|
Register remainder = 0u;
|
|
|
|
crc_modulo_word_update( register_length, remainder, dividend,
|
|
truncated_divisor, SubOrder, false );
|
|
result[ reflect_optionally(dividend, reflect, SubOrder) ] =
|
|
reflect_optionally( remainder, reflect, register_length );
|
|
}
|
|
return result;
|
|
}
|
|
|
|
/** \brief A mix-in class for the table of table-driven CRC algorithms
|
|
|
|
Encapsulates the parameters need to make a global (technically,
|
|
class-static) table usuable in CRC algorithms, and generates said
|
|
table.
|
|
|
|
\pre 0 \< \a SubOrder \<= Order \<=
|
|
std\::numeric_limits\<uintmax_t\>\::digits
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam SubOrder The number of low-order significant bits of the trial
|
|
new dividends.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\tparam Reflect If \c false, read from the highest-order marked
|
|
bit from a new dividend's bits and go down, as normal. Otherwise,
|
|
proceed from the lowest-order bit and go up.
|
|
*/
|
|
template < int Order, int SubOrder, boost::uintmax_t TruncatedPolynomial,
|
|
bool Reflect >
|
|
class crc_table_t
|
|
{
|
|
public:
|
|
/** \brief The type to check for register bit length
|
|
|
|
This is a Boost integral constant indicating how many
|
|
significant bits are in the remainder and (truncated) divisor.
|
|
*/
|
|
typedef boost::integral_constant< int, Order > width_c;
|
|
/** \brief The type to check for index-unit bit length
|
|
|
|
This is a Boost integral constant indicating how many
|
|
significant bits are in the trial new dividends.
|
|
*/
|
|
typedef boost::integral_constant< int, SubOrder > unit_width_c;
|
|
/** \brief The type of registers
|
|
|
|
This is the output type for the partial-product map.
|
|
*/
|
|
typedef typename boost::uint_t< Order >::fast value_type;
|
|
/** \brief The type to check the divisor
|
|
|
|
This is a Boost integral constant representing the (truncated)
|
|
divisor.
|
|
*/
|
|
typedef boost::integral_constant< value_type, TruncatedPolynomial >
|
|
poly_c;
|
|
/** \brief The type to check for reflection
|
|
|
|
This is a Boost integral constant representing whether input
|
|
units should be read in reverse order.
|
|
*/
|
|
typedef boost::integral_constant< bool, Reflect > refin_c;
|
|
/** \brief The type to check for map size
|
|
|
|
This is a Boost integral constant representing the number of
|
|
elements in the partial-product map, based on the unit size.
|
|
*/
|
|
typedef high_bit_mask_c< SubOrder > table_size_c;
|
|
/** \brief The type of the unit TO partial-product map
|
|
|
|
This is the array type that takes units as the index and said unit's
|
|
composite partial-product mask as the element.
|
|
*/
|
|
typedef boost::array<value_type, table_size_c::value> array_type;
|
|
/** \brief Create a global array for the mapping table
|
|
|
|
Creates an instance of a partial-product array with this class's
|
|
parameters.
|
|
|
|
\return A reference to a immutable array giving the partial-product
|
|
update XOR map for each potential sub-unit value.
|
|
*/
|
|
static array_type const & get_table()
|
|
{
|
|
static array_type const table =
|
|
make_partial_xor_products_table<unit_width_c::value>(
|
|
width_c::value, poly_c::value, refin_c::value );
|
|
|
|
return table;
|
|
}
|
|
};
|
|
|
|
/** \brief A mix-in class that handles direct (i.e. non-reflected) byte-fed
|
|
table-driven CRC algorithms
|
|
|
|
This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes aren't
|
|
reflected before processing.
|
|
|
|
\pre \c CHAR_BIT \<= \a Order \<= \c std\::numeric_limits\<uintmax_t\>
|
|
\::digits
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial >
|
|
class direct_byte_table_driven_crcs
|
|
: public crc_table_t<Order, CHAR_BIT, TruncatedPolynomial, false>
|
|
{
|
|
typedef crc_table_t<Order, CHAR_BIT, TruncatedPolynomial, false>
|
|
base_type;
|
|
|
|
public:
|
|
typedef typename base_type::value_type value_type;
|
|
typedef typename base_type::array_type array_type;
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
augmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated remainder
|
|
*/
|
|
static value_type augmented_crc_update( value_type remainder, unsigned
|
|
char const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
static array_type const & table = base_type::get_table();
|
|
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Locates the merged partial product based on the leading byte
|
|
unsigned char const index = ( remainder >> (Order - CHAR_BIT) )
|
|
& UCHAR_MAX;
|
|
|
|
// Complete the multi-bit modulo-2 polynomial division
|
|
remainder <<= CHAR_BIT;
|
|
remainder |= *new_dividend_bytes++;
|
|
remainder ^= table.elems[ index ];
|
|
}
|
|
|
|
return remainder;
|
|
}
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
unaugmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated remainder
|
|
*/
|
|
static value_type crc_update( value_type remainder, unsigned char
|
|
const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
static array_type const & table = base_type::get_table();
|
|
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Locates the merged partial product based on comparing the
|
|
// leading and incoming bytes
|
|
unsigned char const index = ( (remainder >> ( Order - CHAR_BIT
|
|
)) & UCHAR_MAX ) ^ *new_dividend_bytes++;
|
|
|
|
// Complete the multi-bit altered modulo-2 polynomial division
|
|
remainder <<= CHAR_BIT;
|
|
remainder ^= table.elems[ index ];
|
|
}
|
|
|
|
return remainder;
|
|
}
|
|
};
|
|
|
|
/** \brief A mix-in class that handles reflected byte-fed, table-driven CRC
|
|
algorithms
|
|
|
|
This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes are
|
|
reflected before processing.
|
|
|
|
\pre \c CHAR_BIT \<= \a Order \<= \c std\::numeric_limits\<uintmax_t\>
|
|
\::digits
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial >
|
|
class reflected_byte_table_driven_crcs
|
|
: public crc_table_t<Order, CHAR_BIT, TruncatedPolynomial, true>
|
|
{
|
|
typedef crc_table_t<Order, CHAR_BIT, TruncatedPolynomial, true>
|
|
base_type;
|
|
|
|
public:
|
|
typedef typename base_type::value_type value_type;
|
|
typedef typename base_type::array_type array_type;
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
reflecting augmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder; since the bytes are
|
|
being reflected, this remainder also has to be reflected
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated, reflected remainder
|
|
*/
|
|
static value_type augmented_crc_update( value_type remainder, unsigned
|
|
char const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
static array_type const & table = base_type::get_table();
|
|
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Locates the merged partial product based on the leading byte
|
|
// (which is at the low-order end for reflected remainders)
|
|
unsigned char const index = remainder & UCHAR_MAX;
|
|
|
|
// Complete the multi-bit reflected modulo-2 polynomial division
|
|
remainder >>= CHAR_BIT;
|
|
remainder |= static_cast<value_type>( *new_dividend_bytes++ )
|
|
<< ( Order - CHAR_BIT );
|
|
remainder ^= table.elems[ index ];
|
|
}
|
|
|
|
return remainder;
|
|
}
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
reflected unaugmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder; since the bytes are
|
|
being reflected, this remainder also has to be reflected
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated, reflected remainder
|
|
*/
|
|
static value_type crc_update( value_type remainder, unsigned char
|
|
const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
static array_type const & table = base_type::get_table();
|
|
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Locates the merged partial product based on comparing the
|
|
// leading and incoming bytes
|
|
unsigned char const index = ( remainder & UCHAR_MAX ) ^
|
|
*new_dividend_bytes++;
|
|
|
|
// Complete the multi-bit reflected altered modulo-2 polynomial
|
|
// division
|
|
remainder >>= CHAR_BIT;
|
|
remainder ^= table.elems[ index ];
|
|
}
|
|
|
|
return remainder;
|
|
}
|
|
};
|
|
|
|
/** \brief Mix-in class for byte-fed, table-driven CRC algorithms with
|
|
parameter values at least a byte in width
|
|
|
|
This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes may be
|
|
reflected before processing, controlled by a compile-time parameter.
|
|
|
|
\pre \c CHAR_BIT \<= \a Order \<= \c std\::numeric_limits\<uintmax_t\>
|
|
\::digits
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\tparam Reflect If \c false, read from the highest-order bit from a new
|
|
input byte and go down, as normal. Otherwise, proceed from the
|
|
lowest-order bit and go up.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial, bool Reflect >
|
|
class byte_table_driven_crcs
|
|
: public boost::conditional< Reflect,
|
|
reflected_byte_table_driven_crcs<Order, TruncatedPolynomial>,
|
|
direct_byte_table_driven_crcs<Order, TruncatedPolynomial> >::type
|
|
{ };
|
|
|
|
/** \brief A mix-in class that handles direct (i.e. non-reflected) byte-fed
|
|
CRC algorithms for sub-byte parameters
|
|
|
|
This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes aren't
|
|
reflected before processing.
|
|
|
|
\pre 0 \< \a Order \< \c CHAR_BIT
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial >
|
|
class direct_sub_byte_crcs
|
|
: public crc_table_t<Order, Order, TruncatedPolynomial, false>
|
|
{
|
|
typedef crc_table_t<Order, Order, TruncatedPolynomial, false>
|
|
base_type;
|
|
|
|
public:
|
|
typedef typename base_type::width_c width_c;
|
|
typedef typename base_type::value_type value_type;
|
|
typedef typename base_type::poly_c poly_c;
|
|
typedef typename base_type::array_type array_type;
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
augmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated remainder
|
|
|
|
\todo Use this function somewhere so I can test it.
|
|
*/
|
|
static value_type augmented_crc_update( value_type remainder, unsigned
|
|
char const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
//static array_type const & table = base_type::get_table();
|
|
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Without a table, process each byte explicitly
|
|
augmented_crc_modulo_word_update( width_c::value, remainder,
|
|
*new_dividend_bytes++, poly_c::value, CHAR_BIT, false );
|
|
}
|
|
|
|
return remainder;
|
|
}
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
unaugmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated remainder
|
|
*/
|
|
static value_type crc_update( value_type remainder, unsigned char
|
|
const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
//static array_type const & table = base_type::get_table();
|
|
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Without a table, process each byte explicitly
|
|
crc_modulo_word_update( width_c::value, remainder,
|
|
*new_dividend_bytes++, poly_c::value, CHAR_BIT, false );
|
|
}
|
|
|
|
return remainder;
|
|
}
|
|
};
|
|
|
|
/** \brief A mix-in class that handles reflected byte-fed, CRC algorithms
|
|
for sub-byte parameters
|
|
|
|
This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes are
|
|
reflected before processing.
|
|
|
|
\pre 0 \< \a Order \< \c CHAR_BIT
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial >
|
|
class reflected_sub_byte_crcs
|
|
: public crc_table_t<Order, Order, TruncatedPolynomial, true>
|
|
{
|
|
typedef crc_table_t<Order, Order, TruncatedPolynomial, true>
|
|
base_type;
|
|
|
|
public:
|
|
typedef typename base_type::width_c width_c;
|
|
typedef typename base_type::value_type value_type;
|
|
typedef typename base_type::poly_c poly_c;
|
|
typedef typename base_type::array_type array_type;
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
reflecting augmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder; since the bytes are
|
|
being reflected, this remainder also has to be reflected
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated, reflected remainder
|
|
|
|
\todo Use this function somewhere so I can test it.
|
|
*/
|
|
static value_type augmented_crc_update( value_type remainder, unsigned
|
|
char const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
//static array_type const & table = base_type::get_table();
|
|
|
|
remainder = reflect_sub_byte( remainder, width_c::value );
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Without a table, process each byte explicitly
|
|
augmented_crc_modulo_word_update( width_c::value, remainder,
|
|
*new_dividend_bytes++, poly_c::value, CHAR_BIT, true );
|
|
}
|
|
remainder = reflect_sub_byte( remainder, width_c::value );
|
|
|
|
return remainder;
|
|
}
|
|
|
|
/** \brief Compute the updated remainder after reading some bytes
|
|
|
|
The implementation reads from a table to speed-up applying
|
|
reflected unaugmented-CRC updates byte-wise.
|
|
|
|
\param remainder The pre-update remainder; since the bytes are
|
|
being reflected, this remainder also has to be reflected
|
|
\param new_dividend_bytes The address where the new bytes start
|
|
\param new_dividend_byte_count The number of new bytes to read
|
|
|
|
\return The updated, reflected remainder
|
|
*/
|
|
static value_type crc_update( value_type remainder, unsigned char
|
|
const *new_dividend_bytes, std::size_t new_dividend_byte_count)
|
|
{
|
|
//static array_type const & table = base_type::get_table();
|
|
|
|
remainder = reflect_sub_byte( remainder, width_c::value );
|
|
while ( new_dividend_byte_count-- )
|
|
{
|
|
// Without a table, process each byte explicitly
|
|
crc_modulo_word_update( width_c::value, remainder,
|
|
*new_dividend_bytes++, poly_c::value, CHAR_BIT, true );
|
|
}
|
|
remainder = reflect_sub_byte( remainder, width_c::value );
|
|
|
|
return remainder;
|
|
}
|
|
};
|
|
|
|
/** \brief Mix-in class for byte-fed, table-driven CRC algorithms with
|
|
sub-byte parameters
|
|
|
|
This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes may be
|
|
reflected before processing, controlled by a compile-time parameter.
|
|
|
|
\pre 0 \< \a Order \< \c CHAR_BIT
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\tparam Reflect If \c false, read from the highest-order bit from a new
|
|
input byte and go down, as normal. Otherwise, proceed from the
|
|
lowest-order bit and go up.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial, bool Reflect >
|
|
class sub_byte_crcs
|
|
: public boost::conditional< Reflect,
|
|
reflected_sub_byte_crcs<Order, TruncatedPolynomial>,
|
|
direct_sub_byte_crcs<Order, TruncatedPolynomial> >::type
|
|
{ };
|
|
|
|
/** This class template adds member functions #augmented_crc_update and
|
|
#crc_update to update remainders from new input bytes. The bytes may be
|
|
reflected before processing, controlled by a compile-time parameter.
|
|
|
|
\pre 0 \< \a Order \<= \c std\::numeric_limits\<uintmax_t\>\::digits
|
|
|
|
\tparam Order The order of the modulo-2 polynomial remainder and one
|
|
less than the divisor's order.
|
|
\tparam TruncatedPolynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always
|
|
assumed to be 1.
|
|
\tparam Reflect If \c false, read from the highest-order bit from a new
|
|
input byte and go down, as normal. Otherwise, proceed from the
|
|
lowest-order bit and go up.
|
|
\tparam Id An extra differentiator if multiple copies of this class
|
|
template are mixed-in as base classes. Defaults to 0 if omitted.
|
|
*/
|
|
template < int Order, boost::uintmax_t TruncatedPolynomial, bool Reflect,
|
|
int Id >
|
|
class crc_driver
|
|
: public boost::conditional< (Order < CHAR_BIT), sub_byte_crcs<Order,
|
|
TruncatedPolynomial, Reflect>, byte_table_driven_crcs<Order,
|
|
TruncatedPolynomial, Reflect> >::type
|
|
{
|
|
public:
|
|
/** \brief The type to check for ID
|
|
|
|
This is a Boost integral constant indicating what ID number this
|
|
instantiation used.
|
|
*/
|
|
typedef boost::integral_constant<int, Id> id_type;
|
|
};
|
|
|
|
|
|
} // namespace detail
|
|
//! \endcond
|
|
|
|
|
|
// Simple CRC class function definitions -----------------------------------//
|
|
|
|
/** Constructs a \c crc_basic object with at least the required parameters to a
|
|
particular CRC formula to be processed upon receiving input.
|
|
|
|
\param[in] truncated_polynomial The lowest coefficients of the divisor
|
|
polynomial. The highest-order coefficient is omitted and always assumed
|
|
to be 1. (\e Poly from the RMCA)
|
|
\param[in] initial_remainder The (unaugmented) initial state of the
|
|
polynomial remainder. Defaults to \c 0 if omitted. (\e Init from the
|
|
RMCA)
|
|
\param[in] final_xor_value The (XOR) bit-mask to be applied to the output
|
|
remainder, after possible reflection but before returning. Defaults to
|
|
\c 0 (i.e. no bit changes) if omitted. (\e XorOut from the RMCA)
|
|
\param[in] reflect_input If \c true, input bytes are read lowest-order bit
|
|
first, otherwise highest-order bit first. Defaults to \c false if
|
|
omitted. (\e RefIn from the RMCA)
|
|
\param[in] reflect_remainder If \c true, the output remainder is reflected
|
|
before the XOR-mask. Defaults to \c false if omitted. (\e RefOut from
|
|
the RMCA)
|
|
|
|
\post <code><var>truncated_polynomial</var> ==
|
|
this->get_truncated_polynominal()</code>
|
|
\post <code><var>initial_remainder</var> ==
|
|
this->get_initial_remainder()</code>
|
|
\post <code><var>final_xor_value</var> ==
|
|
this->get_final_xor_value()</code>
|
|
\post <code><var>reflect_input</var> ==
|
|
this->get_reflect_input()</code>
|
|
\post <code><var>reflect_remainder</var> ==
|
|
this->get_reflect_remainder()</code>
|
|
\post <code><var>initial_remainder</var> ==
|
|
this->get_interim_remainder()</code>
|
|
\post <code>(<var>reflect_remainder</var> ?
|
|
REFLECT(<var>initial_remainder</var>) : <var>initial_remainder</var>) ^
|
|
<var>final_xor_value</var> == this->checksum()</code>
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
crc_basic<Bits>::crc_basic
|
|
(
|
|
value_type truncated_polynomial,
|
|
value_type initial_remainder, // = 0
|
|
value_type final_xor_value, // = 0
|
|
bool reflect_input, // = false
|
|
bool reflect_remainder // = false
|
|
)
|
|
: rem_( initial_remainder ), poly_( truncated_polynomial )
|
|
, init_( initial_remainder ), final_( final_xor_value )
|
|
, rft_in_( reflect_input ), rft_out_( reflect_remainder )
|
|
{
|
|
}
|
|
|
|
/** Returns a representation of the polynomial divisor. The value of the
|
|
2<sup>i</sup> bit is the value of the coefficient of the polynomial's
|
|
x<sup>i</sup> term. The omitted bit for x<sup>(#bit_count)</sup> term is
|
|
always 1.
|
|
|
|
\return The bit-packed list of coefficients. If the bit-length of
|
|
#value_type exceeds #bit_count, the values of higher-placed bits should be
|
|
ignored (even any for x<sup>(#bit_count)</sup>) since they're unregulated.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
typename crc_basic<Bits>::value_type
|
|
crc_basic<Bits>::get_truncated_polynominal
|
|
(
|
|
) const
|
|
{
|
|
return poly_;
|
|
}
|
|
|
|
/** Returns a representation of the polynomial remainder before any input has
|
|
been submitted. The value of the 2<sup>i</sup> bit is the value of the
|
|
coefficient of the polynomial's x<sup>i</sup> term.
|
|
|
|
\return The bit-packed list of coefficients. If the bit-length of
|
|
#value_type exceeds #bit_count, the values of higher-placed bits should be
|
|
ignored since they're unregulated.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
typename crc_basic<Bits>::value_type
|
|
crc_basic<Bits>::get_initial_remainder
|
|
(
|
|
) const
|
|
{
|
|
return init_;
|
|
}
|
|
|
|
/** Returns the mask to be used during creation of a checksum. The mask is used
|
|
for an exclusive-or (XOR) operation applied bit-wise to the interim
|
|
remainder representation (after any reflection, if #get_reflect_remainder()
|
|
returns \c true).
|
|
|
|
\return The bit-mask. If the bit-length of #value_type exceeds #bit_count,
|
|
the values of higher-placed bits should be ignored since they're
|
|
unregulated.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
typename crc_basic<Bits>::value_type
|
|
crc_basic<Bits>::get_final_xor_value
|
|
(
|
|
) const
|
|
{
|
|
return final_;
|
|
}
|
|
|
|
/** Returns a whether or not a submitted byte will be \"reflected\" before it is
|
|
used to update the interim remainder. Only the byte-wise operations
|
|
#process_byte, #process_block, and #process_bytes are affected.
|
|
|
|
\retval true Input bytes will be read starting from the lowest-order bit.
|
|
\retval false Input bytes will be read starting from the highest-order bit.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
bool
|
|
crc_basic<Bits>::get_reflect_input
|
|
(
|
|
) const
|
|
{
|
|
return rft_in_;
|
|
}
|
|
|
|
/** Indicates if the interim remainder will be \"reflected\" before it is passed
|
|
to the XOR-mask stage when returning a checksum.
|
|
|
|
\retval true The interim remainder is reflected before further work.
|
|
\retval false The interim remainder is applied to the XOR-mask as-is.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
bool
|
|
crc_basic<Bits>::get_reflect_remainder
|
|
(
|
|
) const
|
|
{
|
|
return rft_out_;
|
|
}
|
|
|
|
/** Returns a representation of the polynomial remainder after all the input
|
|
submissions since construction or the last #reset call. The value of the
|
|
2<sup>i</sup> bit is the value of the coefficient of the polynomial's
|
|
x<sup>i</sup> term. If CRC processing gets interrupted here, retain the
|
|
value returned, and use it to start up the next CRC computer where you left
|
|
off (with #reset(value_type) or construction). The next computer has to
|
|
have its other parameters compatible with this computer.
|
|
|
|
\return The bit-packed list of coefficients. If the bit-length of
|
|
#value_type exceeds #bit_count, the values of higher-placed bits should be
|
|
ignored since they're unregulated. No output processing (reflection or
|
|
XOR mask) has been applied to the value.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
typename crc_basic<Bits>::value_type
|
|
crc_basic<Bits>::get_interim_remainder
|
|
(
|
|
) const
|
|
{
|
|
return rem_ & detail::low_bits_mask_c<bit_count>::value;
|
|
}
|
|
|
|
/** Changes the interim polynomial remainder to \a new_rem, purging any
|
|
influence previously submitted input has had. The value of the
|
|
2<sup>i</sup> bit is the value of the coefficient of the polynomial's
|
|
x<sup>i</sup> term.
|
|
|
|
\param[in] new_rem The (unaugmented) state of the polynomial remainder
|
|
starting from this point, with no output processing applied.
|
|
|
|
\post <code><var>new_rem</var> == this->get_interim_remainder()</code>
|
|
\post <code>((this->get_reflect_remainder() ?
|
|
REFLECT(<var>new_rem</var>) : <var>new_rem</var>) ^
|
|
this->get_final_xor_value()) == this->checksum()</code>
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
void
|
|
crc_basic<Bits>::reset
|
|
(
|
|
value_type new_rem
|
|
)
|
|
{
|
|
rem_ = new_rem;
|
|
}
|
|
|
|
/** Changes the interim polynomial remainder to the initial remainder given
|
|
during construction, purging any influence previously submitted input has
|
|
had. The value of the 2<sup>i</sup> bit is the value of the coefficient of
|
|
the polynomial's x<sup>i</sup> term.
|
|
|
|
\post <code>this->get_initial_remainder() ==
|
|
this->get_interim_remainder()</code>
|
|
\post <code>((this->get_reflect_remainder() ?
|
|
REFLECT(this->get_initial_remainder()) :
|
|
this->get_initial_remainder()) ^ this->get_final_xor_value())
|
|
== this->checksum()</code>
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
void
|
|
crc_basic<Bits>::reset
|
|
(
|
|
)
|
|
{
|
|
this->reset( this->get_initial_remainder() );
|
|
}
|
|
|
|
/** Updates the interim remainder with a single altered-CRC-division step.
|
|
|
|
\param[in] bit The new input bit.
|
|
|
|
\post The interim remainder is updated though a modulo-2 polynomial
|
|
division, where the division steps are altered for unaugmented CRCs.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
void
|
|
crc_basic<Bits>::process_bit
|
|
(
|
|
bool bit
|
|
)
|
|
{
|
|
detail::crc_modulo_update( bit_count, rem_, bit, poly_ );
|
|
}
|
|
|
|
/** Updates the interim remainder with several altered-CRC-division steps. Each
|
|
bit is processed separately, starting from the one at the
|
|
2<sup><var>bit_length</var> - 1</sup> place, then proceeding down to the
|
|
lowest-placed bit. Any order imposed by
|
|
<code>this->get_reflect_input()</code> is ignored.
|
|
|
|
\pre 0 \< \a bit_length \<= \c CHAR_BIT
|
|
|
|
\param[in] bits The byte containing the new input bits.
|
|
\param[in] bit_length The number of bits in the byte to be read.
|
|
|
|
\post The interim remainder is updated though \a bit_length modulo-2
|
|
polynomial divisions, where the division steps are altered for unaugmented
|
|
CRCs.
|
|
*/
|
|
template < std::size_t Bits >
|
|
void
|
|
crc_basic<Bits>::process_bits
|
|
(
|
|
unsigned char bits,
|
|
std::size_t bit_length
|
|
)
|
|
{
|
|
// ignore the bits above the ones we want
|
|
bits <<= CHAR_BIT - bit_length;
|
|
|
|
// compute the CRC for each bit, starting with the upper ones
|
|
unsigned char const high_bit_mask = 1u << ( CHAR_BIT - 1u );
|
|
for ( std::size_t i = bit_length ; i > 0u ; --i, bits <<= 1u )
|
|
{
|
|
process_bit( static_cast<bool>(bits & high_bit_mask) );
|
|
}
|
|
}
|
|
|
|
/** Updates the interim remainder with a byte's worth of altered-CRC-division
|
|
steps. The bits within the byte are processed from the highest place down
|
|
if <code>this->get_reflect_input()</code> is \c false, and lowest place
|
|
up otherwise.
|
|
|
|
\param[in] byte The new input byte.
|
|
|
|
\post The interim remainder is updated though \c CHAR_BIT modulo-2
|
|
polynomial divisions, where the division steps are altered for unaugmented
|
|
CRCs.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
void
|
|
crc_basic<Bits>::process_byte
|
|
(
|
|
unsigned char byte
|
|
)
|
|
{
|
|
process_bits( (rft_in_ ? detail::reflect_byte( byte ) : byte), CHAR_BIT );
|
|
}
|
|
|
|
/** Updates the interim remainder with several bytes' worth of
|
|
altered-CRC-division steps. The bits within each byte are processed from
|
|
the highest place down if <code>this->get_reflect_input()</code> is
|
|
\c false, and lowest place up otherwise. The bytes themselves are processed
|
|
starting from the one pointed by \a bytes_begin until \a bytes_end is
|
|
reached through forward iteration, treating the two pointers as if they
|
|
point to <code>unsigned char</code> objects.
|
|
|
|
\pre \a bytes_end has to equal \a bytes_begin if the latter is \c NULL or
|
|
otherwise doesn't point to a valid buffer.
|
|
\pre \a bytes_end, if not equal to \a bytes_begin, has to point within or
|
|
one-byte-past the same buffer \a bytes_begin points into.
|
|
\pre \a bytes_end has to be reachable from \a bytes_begin through a finite
|
|
number of forward byte-pointer increments.
|
|
|
|
\param[in] bytes_begin The address where the memory block begins.
|
|
\param[in] bytes_end Points to one-byte past the address of the memory
|
|
block's last byte, or \a bytes_begin if no bytes are to be read.
|
|
|
|
\post The interim remainder is updated though <code>CHAR_BIT * (((unsigned
|
|
char const *) bytes_end) - ((unsigned char const *) bytes_begin))</code>
|
|
modulo-2 polynomial divisions, where the division steps are altered for
|
|
unaugmented CRCs.
|
|
*/
|
|
template < std::size_t Bits >
|
|
void
|
|
crc_basic<Bits>::process_block
|
|
(
|
|
void const * bytes_begin,
|
|
void const * bytes_end
|
|
)
|
|
{
|
|
for ( unsigned char const * p
|
|
= static_cast<unsigned char const *>(bytes_begin) ; p < bytes_end ; ++p )
|
|
{
|
|
process_byte( *p );
|
|
}
|
|
}
|
|
|
|
/** Updates the interim remainder with several bytes' worth of
|
|
altered-CRC-division steps. The bits within each byte are processed from
|
|
the highest place down if <code>this->get_reflect_input()</code> is
|
|
\c false, and lowest place up otherwise. The bytes themselves are processed
|
|
starting from the one pointed by \a buffer, forward-iterated (as if the
|
|
pointed-to objects were of <code>unsigned char</code>) until \a byte_count
|
|
bytes are read.
|
|
|
|
\pre \a byte_count has to equal 0 if \a buffer is \c NULL or otherwise
|
|
doesn't point to valid memory.
|
|
\pre If \a buffer points within valid memory, then that block has to have
|
|
at least \a byte_count more valid bytes allocated from that point.
|
|
|
|
\param[in] buffer The address where the memory block begins.
|
|
\param[in] byte_count The number of bytes in the memory block.
|
|
|
|
\post The interim remainder is updated though <code>CHAR_BIT *
|
|
<var>byte_count</var></code> modulo-2 polynomial divisions, where the
|
|
division steps are altered for unaugmented CRCs.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
void
|
|
crc_basic<Bits>::process_bytes
|
|
(
|
|
void const * buffer,
|
|
std::size_t byte_count
|
|
)
|
|
{
|
|
unsigned char const * const b = static_cast<unsigned char const *>(
|
|
buffer );
|
|
|
|
process_block( b, b + byte_count );
|
|
}
|
|
|
|
/** Computes the checksum of all the submitted bits since construction or the
|
|
last call to #reset. The checksum will be the raw checksum, i.e. the
|
|
(interim) remainder after all the modulo-2 polynomial division, plus any
|
|
output processing.
|
|
|
|
\return <code>(this->get_reflect_remainder() ?
|
|
REFLECT(this->get_interim_remainder()) :
|
|
this->get_interim_remainder()) ^ this->get_final_xor_value()</code>
|
|
|
|
\note Since checksums are meant to be compared, any higher-placed bits
|
|
(when the bit-length of #value_type exceeds #bit_count) will be set to 0.
|
|
*/
|
|
template < std::size_t Bits >
|
|
inline
|
|
typename crc_basic<Bits>::value_type
|
|
crc_basic<Bits>::checksum
|
|
(
|
|
) const
|
|
{
|
|
return ( (rft_out_ ? detail::reflect_unsigned( rem_, bit_count ) :
|
|
rem_) ^ final_ ) & detail::low_bits_mask_c<bit_count>::value;
|
|
}
|
|
|
|
|
|
// Optimized CRC class function definitions --------------------------------//
|
|
|
|
// Macro to compact code
|
|
#define BOOST_CRC_OPTIMAL_NAME crc_optimal<Bits, TruncPoly, InitRem, \
|
|
FinalXor, ReflectIn, ReflectRem>
|
|
|
|
/** Constructs a \c crc_optimal object with a particular CRC formula to be
|
|
processed upon receiving input. The initial remainder may be overridden.
|
|
|
|
\param[in] init_rem The (unaugmented) initial state of the polynomial
|
|
remainder. Defaults to #initial_remainder if omitted.
|
|
|
|
\post <code>#truncated_polynominal ==
|
|
this->get_truncated_polynominal()</code>
|
|
\post <code>#initial_remainder == this->get_initial_remainder()</code>
|
|
\post <code>#final_xor_value == this->get_final_xor_value()</code>
|
|
\post <code>#reflect_input == this->get_reflect_input()</code>
|
|
\post <code>#reflect_remainder == this->get_reflect_remainder()</code>
|
|
\post <code><var>init_rem</var> == this->get_interim_remainder()</code>
|
|
\post <code>(#reflect_remainder ? REFLECT(<var>init_rem</var>) :
|
|
<var>init_rem</var>) ^ #final_xor_value == this->checksum()</code>
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
BOOST_CRC_OPTIMAL_NAME::crc_optimal
|
|
(
|
|
value_type init_rem // = initial_remainder
|
|
)
|
|
: rem_( reflect_i_type::reflect_q(init_rem) )
|
|
{
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::get_truncated_polynominal
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename BOOST_CRC_OPTIMAL_NAME::value_type
|
|
BOOST_CRC_OPTIMAL_NAME::get_truncated_polynominal
|
|
(
|
|
) const
|
|
{
|
|
return truncated_polynominal;
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::get_initial_remainder
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename BOOST_CRC_OPTIMAL_NAME::value_type
|
|
BOOST_CRC_OPTIMAL_NAME::get_initial_remainder
|
|
(
|
|
) const
|
|
{
|
|
return initial_remainder;
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::get_final_xor_value
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename BOOST_CRC_OPTIMAL_NAME::value_type
|
|
BOOST_CRC_OPTIMAL_NAME::get_final_xor_value
|
|
(
|
|
) const
|
|
{
|
|
return final_xor_value;
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::get_reflect_input
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
bool
|
|
BOOST_CRC_OPTIMAL_NAME::get_reflect_input
|
|
(
|
|
) const
|
|
{
|
|
return reflect_input;
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::get_reflect_remainder
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
bool
|
|
BOOST_CRC_OPTIMAL_NAME::get_reflect_remainder
|
|
(
|
|
) const
|
|
{
|
|
return reflect_remainder;
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::get_interim_remainder
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename BOOST_CRC_OPTIMAL_NAME::value_type
|
|
BOOST_CRC_OPTIMAL_NAME::get_interim_remainder
|
|
(
|
|
) const
|
|
{
|
|
// Interim remainder should be _un_-reflected, so we have to undo it.
|
|
return reflect_i_type::reflect_q( rem_ ) &
|
|
detail::low_bits_mask_c<bit_count>::value;
|
|
}
|
|
|
|
/** Changes the interim polynomial remainder to \a new_rem, purging any
|
|
influence previously submitted input has had. The value of the
|
|
2<sup>i</sup> bit is the value of the coefficient of the polynomial's
|
|
x<sup>i</sup> term.
|
|
|
|
\param[in] new_rem The (unaugmented) state of the polynomial remainder
|
|
starting from this point, with no output processing applied. Defaults to
|
|
<code>this->get_initial_remainder()</code> if omitted.
|
|
|
|
\post <code><var>new_rem</var> == this->get_interim_remainder()</code>
|
|
\post <code>((this->get_reflect_remainder() ?
|
|
REFLECT(<var>new_rem</var>) : <var>new_rem</var>) ^
|
|
this->get_final_xor_value()) == this->checksum()</code>
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
void
|
|
BOOST_CRC_OPTIMAL_NAME::reset
|
|
(
|
|
value_type new_rem // = initial_remainder
|
|
)
|
|
{
|
|
rem_ = reflect_i_type::reflect_q( new_rem );
|
|
}
|
|
|
|
/** \copydetails boost::crc_basic::process_byte
|
|
|
|
\note Any modulo-2 polynomial divisions may use a table of pre-computed
|
|
remainder changes (as XOR masks) to speed computation when reading data
|
|
byte-wise.
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
void
|
|
BOOST_CRC_OPTIMAL_NAME::process_byte
|
|
(
|
|
unsigned char byte
|
|
)
|
|
{
|
|
process_bytes( &byte, sizeof(byte) );
|
|
}
|
|
|
|
/** \copydetails boost::crc_basic::process_block
|
|
|
|
\note Any modulo-2 polynomial divisions may use a table of pre-computed
|
|
remainder changes (as XOR masks) to speed computation when reading data
|
|
byte-wise.
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
void
|
|
BOOST_CRC_OPTIMAL_NAME::process_block
|
|
(
|
|
void const * bytes_begin,
|
|
void const * bytes_end
|
|
)
|
|
{
|
|
process_bytes( bytes_begin, static_cast<unsigned char const *>(bytes_end) -
|
|
static_cast<unsigned char const *>(bytes_begin) );
|
|
}
|
|
|
|
/** \copydetails boost::crc_basic::process_bytes
|
|
|
|
\note Any modulo-2 polynomial divisions may use a table of pre-computed
|
|
remainder changes (as XOR masks) to speed computation when reading data
|
|
byte-wise.
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
void
|
|
BOOST_CRC_OPTIMAL_NAME::process_bytes
|
|
(
|
|
void const * buffer,
|
|
std::size_t byte_count
|
|
)
|
|
{
|
|
rem_ = crc_table_type::crc_update( rem_, static_cast<unsigned char const
|
|
*>(buffer), byte_count );
|
|
}
|
|
|
|
//! \copydetails boost::crc_basic::checksum
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename BOOST_CRC_OPTIMAL_NAME::value_type
|
|
BOOST_CRC_OPTIMAL_NAME::checksum
|
|
(
|
|
) const
|
|
{
|
|
return ( reflect_o_type::reflect_q(rem_) ^ get_final_xor_value() )
|
|
& detail::low_bits_mask_c<bit_count>::value;
|
|
}
|
|
|
|
/** Updates the interim remainder with a byte's worth of altered-CRC-division
|
|
steps. The bits within the byte are processed from the highest place down
|
|
if <code>this->get_reflect_input()</code> is \c false, and lowest place
|
|
up otherwise. This function is meant to present a function-object interface
|
|
to code that wants to process a stream of bytes with
|
|
<code>std::for_each</code> or similar range-processing algorithms. Since
|
|
some of these algorithms takes their function object by value, make sure to
|
|
copy back the result to this object so the updates can be remembered.
|
|
|
|
\param[in] byte The new input byte.
|
|
|
|
\post The interim remainder is updated though \c CHAR_BIT modulo-2
|
|
polynomial divisions, where the division steps are altered for unaugmented
|
|
CRCs.
|
|
|
|
\note Any modulo-2 polynomial divisions may use a table of pre-computed
|
|
remainder changes (as XOR masks) to speed computation when reading data
|
|
byte-wise.
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
void
|
|
BOOST_CRC_OPTIMAL_NAME::operator ()
|
|
(
|
|
unsigned char byte
|
|
)
|
|
{
|
|
process_byte( byte );
|
|
}
|
|
|
|
/** Computes the checksum of all the submitted bits since construction or the
|
|
last call to #reset. The checksum will be the raw checksum, i.e. the
|
|
(interim) remainder after all the modulo-2 polynomial division, plus any
|
|
output processing. This function is meant to present a function-object
|
|
interface to code that wants to receive data like
|
|
<code>std::generate_n</code> or similar data-processing algorithms. Note
|
|
that if this object is used as a generator multiple times without an
|
|
intervening mutating operation, the same value will always be returned.
|
|
|
|
\return <code>(this->get_reflect_remainder() ?
|
|
REFLECT(this->get_interim_remainder()) :
|
|
this->get_interim_remainder()) ^ this->get_final_xor_value()</code>
|
|
|
|
\note Since checksums are meant to be compared, any higher-placed bits
|
|
(when the bit-length of #value_type exceeds #bit_count) will be set to 0.
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename BOOST_CRC_OPTIMAL_NAME::value_type
|
|
BOOST_CRC_OPTIMAL_NAME::operator ()
|
|
(
|
|
) const
|
|
{
|
|
return checksum();
|
|
}
|
|
|
|
|
|
// CRC computation function definition -------------------------------------//
|
|
|
|
/** Computes the polynomial remainder of a CRC run, assuming that \a buffer and
|
|
\a byte_count describe a memory block representing the polynomial dividend.
|
|
The division steps are altered so the result directly gives a checksum,
|
|
without need to augment the memory block with scratch-space bytes. The
|
|
first byte is considered the highest order, going down for subsequent bytes.
|
|
|
|
\pre 0 \< \a Bits \<= \c std\::numeric_limits\<uintmax_t\>\::digits
|
|
|
|
\tparam Bits The order of the modulo-2 polynomial divisor. (\e Width from
|
|
the RMCA)
|
|
\tparam TruncPoly The lowest coefficients of the divisor polynomial. The
|
|
highest-order coefficient is omitted and always assumed to be 1.
|
|
(\e Poly from the RMCA)
|
|
\tparam InitRem The (unaugmented) initial state of the polynomial
|
|
remainder. (\e Init from the RMCA)
|
|
\tparam FinalXor The (XOR) bit-mask to be applied to the output remainder,
|
|
after possible reflection but before returning. (\e XorOut from the RMCA)
|
|
\tparam ReflectIn If \c True, input bytes are read lowest-order bit first,
|
|
otherwise highest-order bit first. (\e RefIn from the RMCA)
|
|
\tparam ReflectRem If \c True, the output remainder is reflected before the
|
|
XOR-mask. (\e RefOut from the RMCA)
|
|
|
|
\param[in] buffer The address where the memory block begins.
|
|
\param[in] byte_count The number of bytes in the memory block.
|
|
|
|
\return The checksum, which is the last (interim) remainder plus any output
|
|
processing.
|
|
|
|
\note Unaugmented-style CRC runs perform modulo-2 polynomial division in
|
|
an altered order. The trailing \a Bits number of zero-valued bits needed
|
|
to extracted an (unprocessed) checksum is virtually moved to near the
|
|
beginning of the message. This is OK since the XOR operation is
|
|
commutative and associative. It also means that you can get a checksum
|
|
anytime. Since data is being read byte-wise, a table of pre-computed
|
|
remainder changes (as XOR masks) can be used to speed computation.
|
|
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly,
|
|
BOOST_CRC_PARM_TYPE InitRem, BOOST_CRC_PARM_TYPE FinalXor,
|
|
bool ReflectIn, bool ReflectRem >
|
|
inline
|
|
typename uint_t<Bits>::fast
|
|
crc
|
|
(
|
|
void const * buffer,
|
|
std::size_t byte_count
|
|
)
|
|
{
|
|
BOOST_CRC_OPTIMAL_NAME computer;
|
|
computer.process_bytes( buffer, byte_count );
|
|
return computer.checksum();
|
|
}
|
|
|
|
|
|
// Augmented-message CRC computation function definition -------------------//
|
|
|
|
/** Computes the polynomial remainder of a CRC run, assuming that \a buffer and
|
|
\a byte_count describe a memory block representing the polynomial dividend.
|
|
The first byte is considered the highest order, going down for subsequent
|
|
bytes. Within a byte, the highest-order bit is read first (corresponding to
|
|
\e RefIn = \c False in the RMCA). Check the other parts of this function's
|
|
documentation to see how a checksum can be gained and/or used.
|
|
|
|
\pre 0 \< \a Bits \<= \c std\::numeric_limit\<uintmax_t\>\::digits
|
|
|
|
\tparam Bits The order of the modulo-2 polynomial divisor. (\e Width from
|
|
the RMCA)
|
|
\tparam TruncPoly The lowest coefficients of the divisor polynomial. The
|
|
highest-order coefficient is omitted and always assumed to be 1.
|
|
(\e Poly from the RMCA)
|
|
|
|
\param[in] buffer The address where the memory block begins.
|
|
\param[in] byte_count The number of bytes in the memory block.
|
|
\param[in] initial_remainder The initial state of the polynomial
|
|
remainder, defaulting to zero if omitted. If you are reading a memory
|
|
block in multiple runs, put the return value of the previous run here.
|
|
(Note that initial-remainders given by RMCA parameter lists, as
|
|
\e Init, assume that the initial remainder is in its \b unaugmented state,
|
|
so you would need to convert the value to make it suitable for this
|
|
function. I currently don't provide a conversion routine.)
|
|
|
|
\return The interim remainder, if no augmentation is used. A special value
|
|
if augmentation is used (see the notes). No output processing is done on
|
|
the value. (In RMCA terms, \e RefOut is \c False and \e XorOut is \c 0.)
|
|
|
|
\note Augmented-style CRC runs use straight-up modulo-2 polynomial
|
|
division. Since data is being read byte-wise, a table of pre-computed
|
|
remainder changes (as XOR masks) can be used to speed computation.
|
|
\note Reading just a memory block will yield an interim remainder, and not
|
|
the final checksum. To get that checksum, allocate \a Bits / \c CHAR_BIT
|
|
bytes directly after the block and fill them with zero values, then extend
|
|
\a byte_count to include those extra bytes. A data block is corrupt if
|
|
the return value doesn't equal your separately given checksum.
|
|
\note Another way to perform a check is use the zero-byte extension method,
|
|
but replace the zero values with your separately-given checksum. The
|
|
checksum must be loaded in big-endian order. Here corruption, in either
|
|
the data block or the given checksum, is confirmed if the return value is
|
|
not zero.
|
|
\note The two checksum techniques assume the CRC-run is performed bit-wise,
|
|
while this function works byte-wise. That means that the techniques can
|
|
be used only if \c CHAR_BIT divides \a Bits evenly!
|
|
*/
|
|
template < std::size_t Bits, BOOST_CRC_PARM_TYPE TruncPoly >
|
|
typename uint_t<Bits>::fast
|
|
augmented_crc
|
|
(
|
|
void const * buffer,
|
|
std::size_t byte_count,
|
|
typename uint_t<Bits>::fast initial_remainder // = 0u
|
|
)
|
|
{
|
|
return detail::low_bits_mask_c<Bits>::value &
|
|
detail::byte_table_driven_crcs<Bits, TruncPoly, false>::
|
|
augmented_crc_update( initial_remainder, static_cast<unsigned char const
|
|
*>(buffer), byte_count );
|
|
}
|
|
|
|
|
|
} // namespace boost
|
|
|
|
|
|
// Undo header-private macros
|
|
#undef BOOST_CRC_OPTIMAL_NAME
|
|
#undef BOOST_CRC_PARM_TYPE
|
|
|
|
|
|
#endif // BOOST_CRC_HPP
|
|
|