From 716747787439264d92e9ba1c48bb43146a0043b0 Mon Sep 17 00:00:00 2001
From: jakcron <jkrcarr@gmail.com>
Date: Sun, 25 Mar 2018 19:52:56 +0800
Subject: [PATCH] [fnd] overloaded fnd::io::readFile to allow specifying an
 offset and size.

---
 lib/libfnd/include/fnd/io.h      |  1 +
 lib/libfnd/source/io.cpp         | 42 ++++++++++++++++++++++++++++++++
 programs/xcitool/source/main.cpp | 20 +++++----------
 3 files changed, 49 insertions(+), 14 deletions(-)

diff --git a/lib/libfnd/include/fnd/io.h b/lib/libfnd/include/fnd/io.h
index e80d5c3..7318126 100644
--- a/lib/libfnd/include/fnd/io.h
+++ b/lib/libfnd/include/fnd/io.h
@@ -7,6 +7,7 @@ namespace fnd
 	namespace io
 	{
 		void readFile(const std::string& path, MemoryBlob& blob);
+		void readFile(const std::string& path, size_t offset, size_t len, MemoryBlob& blob);
 		void writeFile(const std::string& path, const MemoryBlob& blob);
 		void writeFile(const std::string& path, const byte_t* data, size_t len);
 	}
diff --git a/lib/libfnd/source/io.cpp b/lib/libfnd/source/io.cpp
index 2f4ce8e..0c2ef08 100644
--- a/lib/libfnd/source/io.cpp
+++ b/lib/libfnd/source/io.cpp
@@ -41,6 +41,48 @@ void io::readFile(const std::string& path, MemoryBlob & blob)
 	fclose(fp);
 }
 
+void fnd::io::readFile(const std::string& path, size_t offset, size_t len, MemoryBlob& blob)
+{
+	FILE* fp;
+	size_t filesz, filepos;
+
+	if ((fp = fopen(path.c_str(), "rb")) == NULL)
+	{
+		throw Exception(kModuleName, "Failed to open \"" + path + "\": does not exist");
+	}
+
+	fseek(fp, 0, SEEK_END);
+	filesz = ftell(fp);
+	rewind(fp);
+	fseek(fp, offset, SEEK_SET);
+
+	if (filesz < len || filesz < offset || filesz < (offset + len))
+	{
+		throw Exception(kModuleName, "Failed to open \"" + path + "\": file to small");
+	}
+
+	try
+	{
+		blob.alloc(len);
+	} catch (const fnd::Exception& e)
+	{
+		fclose(fp);
+		throw fnd::Exception(kModuleName, "Failed to allocate memory for file: " + std::string(e.what()));
+	}
+
+	for (filepos = 0; len > kBlockSize; len -= kBlockSize, filepos += kBlockSize)
+	{
+		fread(blob.getBytes() + filepos, 1, kBlockSize, fp);
+	}
+
+	if (len)
+	{
+		fread(blob.getBytes() + filepos, 1, len, fp);
+	}
+
+	fclose(fp);
+}
+
 void io::writeFile(const std::string& path, const MemoryBlob & blob)
 {
 	writeFile(path, blob.getBytes(), blob.getSize());
diff --git a/programs/xcitool/source/main.cpp b/programs/xcitool/source/main.cpp
index 7d66829..6159db3 100644
--- a/programs/xcitool/source/main.cpp
+++ b/programs/xcitool/source/main.cpp
@@ -250,7 +250,7 @@ void decryptXciHeader(const byte_t* src, byte_t* dst)
 	const byte_t* src_iv = ((const sXciHeader*)src)->encryption_iv;
 	byte_t iv[crypto::aes::kAesBlockSize];
 
-	for (int i = 0; i < crypto::aes::kAesBlockSize; i++)
+	for (size_t i = 0; i < crypto::aes::kAesBlockSize; i++)
 	{
 		iv[i] = src_iv[15 - i];
 	}
@@ -270,21 +270,13 @@ int main(int argc, char** argv)
 		return 1;
 	}
 
-	FILE* fp = fopen(argv[1], "rb");
-	if (fp == nullptr)
-	{
-		printf("Failed to open file.\n");
-		return 1;
-	}
-
+	
 	fnd::MemoryBlob xciFile;
-	xciFile.alloc(0x200);
-	fread(xciFile.getBytes(), 0x200, 1, fp);
-	fclose(fp);
+	fnd::io::readFile(argv[1], 0x100, 0x100, xciFile);
 
-	sXciHeader hdr;
-	decryptXciHeader(xciFile.getBytes() + 0x100, (byte_t*)&hdr);
-	printXciHeader(hdr, true);
+	sXciHeader* hdr = (sXciHeader*)xciFile.getBytes();
+	decryptXciHeader(xciFile.getBytes(), xciFile.getBytes());
+	printXciHeader(*hdr, true);
 
 	return 0;
 }
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