mirror of
https://github.com/yuzu-emu/mbedtls.git
synced 2024-10-18 15:21:03 +00:00
Added integer divide by as separate function
Added 64bit integer divided by 32bit integer, with remainder
This commit is contained in:
Simon Butcher
parent
3134ef0504
commit
15b15d1361
186
library/bignum.c
186
library/bignum.c
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@ -18,13 +18,22 @@
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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/*
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* This MPI implementation is based on:
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* The following sources were referenced in the design of this Multi-precision
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* Integer library:
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*
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* http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf
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* http://www.stillhq.com/extracted/gnupg-api/mpi/
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* http://math.libtomcrypt.com/files/tommath.pdf
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*/
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* [1] Handbook of Applied Cryptography - 1997
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* Menezes, van Oorschot and Vanstone
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*
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* [2] Multi-Precision Math
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* Tom St Denis
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* https://github.com/libtom/libtommath/blob/develop/tommath.pdf
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*
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* [3] GNU Multi-Precision Arithmetic Library
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* https://gmplib.org/manual/index.html
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*
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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@ -347,6 +356,24 @@ size_t mbedtls_mpi_lsb( const mbedtls_mpi *X )
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return( 0 );
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}
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/*
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* Count leading zero bits in a given integer
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*/
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static size_t mbedtls_clz( const mbedtls_mpi_uint x )
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{
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size_t j;
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mbedtls_mpi_uint mask = 1 << (biL - 1);
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for( j = 0; j < biL; j++ )
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{
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if( x & mask ) break;
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mask >>= 1;
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}
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return j;
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}
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/*
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* Return the number of bits
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*/
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@ -361,9 +388,7 @@ size_t mbedtls_mpi_bitlen( const mbedtls_mpi *X )
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if( X->p[i] != 0 )
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break;
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for( j = biL; j > 0; j-- )
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if( ( ( X->p[i] >> ( j - 1 ) ) & 1 ) != 0 )
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break;
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j = biL - mbedtls_clz( X->p[i] );
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return( ( i * biL ) + j );
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}
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@ -1186,6 +1211,98 @@ int mbedtls_mpi_mul_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_uint
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return( mbedtls_mpi_mul_mpi( X, A, &_B ) );
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}
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/*
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* Unsigned integer divide - 64bit dividend and 32bit divisor
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*/
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static mbedtls_mpi_uint mbedtls_int_div_int(mbedtls_mpi_uint u1,
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mbedtls_mpi_uint u0, mbedtls_mpi_uint d, mbedtls_mpi_uint *r)
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{
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/*
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* Check for overflow
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*/
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if(( 0 == d ) || ( u1 >= d ))
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{
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if (r != NULL) *r = (~0);
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return (~0);
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}
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#if defined(MBEDTLS_HAVE_UDBL)
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mbedtls_t_udbl dividend;
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mbedtls_mpi_uint quotient;
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dividend = (mbedtls_t_udbl) u1 << biL;
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dividend |= (mbedtls_t_udbl) u0;
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quotient = dividend / d;
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if( quotient > ( (mbedtls_t_udbl) 1 << biL ) - 1 )
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quotient = ( (mbedtls_t_udbl) 1 << biL ) - 1;
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if( r != NULL )
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*r = dividend - (quotient * d);
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return (mbedtls_mpi_uint) quotient;
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#else
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const mbedtls_mpi_uint radix = 1 << biH;
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mbedtls_mpi_uint d0, d1, q0, q1, rAX, r0, quotient;
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mbedtls_mpi_uint u0_msw, u0_lsw;
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int s;
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/*
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* Algorithm D, Section 4.3.1 - The Art of Computer Programming
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* Vol. 2 - Seminumerical Algorithms, Knuth
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*/
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/*
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* Normalize the divisor, d, and dividend, u0, u1
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*/
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s = mbedtls_clz( d );
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d = d << s;
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u1 = u1 << s;
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u1 |= (u0 >> (32 - s)) & ( (-s) >> 31);
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u0 = u0 << s;
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d1 = d >> biH;
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d0 = d & 0xffff;
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u0_msw = u0 >> biH;
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u0_lsw = u0 & 0xffff;
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/*
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* Find the first quotient and remainder
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*/
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q1 = u1 / d1;
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r0 = u1 - d1 * q1;
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while( q1 >= radix || ( q1 * d0 > radix * r0 + u0_msw ) )
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{
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q1 -= 1;
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r0 += d1;
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if ( r0 >= radix ) break;
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}
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rAX = (u1 * radix) + (u0_msw - q1 * d);
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q0 = rAX / d1;
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r0 = rAX - q0 * d1;
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while( q0 >= radix || ( q0 * d0 > radix * r0 + u0_lsw ) )
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{
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q0 -= 1;
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r0 += d1;
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if ( r0 >= radix ) break;
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}
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if (r != NULL)
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*r = (rAX * radix + u0_lsw - q0 * d) >> s;
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quotient = q1 * radix + q0;
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return quotient;
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#endif
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}
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/*
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* Division by mbedtls_mpi: A = Q * B + R (HAC 14.20)
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*/
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@ -1243,57 +1360,8 @@ int mbedtls_mpi_div_mpi( mbedtls_mpi *Q, mbedtls_mpi *R, const mbedtls_mpi *A, c
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Z.p[i - t - 1] = ~0;
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else
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{
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#if defined(MBEDTLS_HAVE_UDBL)
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mbedtls_t_udbl r;
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r = (mbedtls_t_udbl) X.p[i] << biL;
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r |= (mbedtls_t_udbl) X.p[i - 1];
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r /= Y.p[t];
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if( r > ( (mbedtls_t_udbl) 1 << biL ) - 1 )
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r = ( (mbedtls_t_udbl) 1 << biL ) - 1;
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Z.p[i - t - 1] = (mbedtls_mpi_uint) r;
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#else
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/*
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* __udiv_qrnnd_c, from gmp/longlong.h
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*/
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mbedtls_mpi_uint q0, q1, r0, r1;
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mbedtls_mpi_uint d0, d1, d, m;
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d = Y.p[t];
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d0 = ( d << biH ) >> biH;
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d1 = ( d >> biH );
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q1 = X.p[i] / d1;
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r1 = X.p[i] - d1 * q1;
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r1 <<= biH;
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r1 |= ( X.p[i - 1] >> biH );
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m = q1 * d0;
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if( r1 < m )
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{
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q1--, r1 += d;
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while( r1 >= d && r1 < m )
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q1--, r1 += d;
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}
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r1 -= m;
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q0 = r1 / d1;
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r0 = r1 - d1 * q0;
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r0 <<= biH;
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r0 |= ( X.p[i - 1] << biH ) >> biH;
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m = q0 * d0;
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if( r0 < m )
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{
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q0--, r0 += d;
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while( r0 >= d && r0 < m )
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q0--, r0 += d;
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}
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r0 -= m;
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Z.p[i - t - 1] = ( q1 << biH ) | q0;
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#endif /* MBEDTLS_HAVE_UDBL && !64-bit Apple with Clang 5.0 */
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Z.p[i - t - 1] = mbedtls_int_div_int( X.p[i], X.p[i - 1],
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Y.p[t], NULL);
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}
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Z.p[i - t - 1]++;
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