bspatch.cc - platform/external/bsdiff - Git at Google

 /*-
  * Copyright 2003-2005 Colin Percival
  * All rights reserved
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted providing that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  * POSSIBILITY OF SUCH DAMAGE.
  */

 #if 0
 __FBSDID("$FreeBSD: src/usr.bin/bsdiff/bspatch/bspatch.c,v 1.1 2005/08/06 01:59:06 cperciva Exp $");
 #endif

 #include "bspatch.h"

 #include <bzlib.h>
 #include <err.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <inttypes.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/types.h>

 #include <algorithm>
 #include <memory>
 #include <limits>
 #include <vector>

 #include "extents.h"
 #include "extents_file.h"
 #include "file.h"
 #include "file_interface.h"
 #include "memory_file.h"

 namespace {

 int64_t ParseInt64(u_char* buf) {
   int64_t y;

   y = buf[7] & 0x7F;
   y = y * 256;
   y += buf[6];
   y = y * 256;
   y += buf[5];
   y = y * 256;
   y += buf[4];
   y = y * 256;
   y += buf[3];
   y = y * 256;
   y += buf[2];
   y = y * 256;
   y += buf[1];
   y = y * 256;
   y += buf[0];

   if (buf[7] & 0x80)
     y = -y;

   return y;
 }

 bool ReadBZ2(BZFILE* pfbz2, uint8_t* data, size_t size) {
   int bz2err;
   size_t lenread = BZ2_bzRead(&bz2err, pfbz2, data, size);
   if (lenread < size || (bz2err != BZ_OK && bz2err != BZ_STREAM_END))
     return false;
   return true;
 }

 bool ReadBZ2AndWriteAll(const std::unique_ptr<bsdiff::FileInterface>& file,
                         BZFILE* pfbz2,
                         size_t size,
                         uint8_t* buf,
                         size_t buf_size) {
   while (size > 0) {
     size_t bytes_to_read = std::min(size, buf_size);
     if (!ReadBZ2(pfbz2, buf, bytes_to_read))
       return false;
     if (!WriteAll(file, buf, bytes_to_read))
       return false;
     size -= bytes_to_read;
   }
   return true;
 }

 }  // namespace

 namespace bsdiff {

 bool WriteAll(const std::unique_ptr<FileInterface>& file,
               const uint8_t* data,
               size_t size) {
   size_t offset = 0, written;
   while (offset < size) {
     if (!file->Write(data + offset, size - offset, &written) || written == 0)
       return false;
     offset += written;
   }
   return true;
 }

 bool IsOverlapping(const char* old_filename,
                    const char* new_filename,
                    const std::vector<ex_t>& old_extents,
                    const std::vector<ex_t>& new_extents) {
   struct stat old_stat, new_stat;
   if (stat(new_filename, &new_stat) == -1) {
     if (errno == ENOENT)
       return false;
     err(1, "Error stat the new filename %s", new_filename);
   }
   if (stat(old_filename, &old_stat) == -1)
     err(1, "Error stat the old filename %s", old_filename);

   if (old_stat.st_dev != new_stat.st_dev || old_stat.st_ino != new_stat.st_ino)
     return false;

   if (old_extents.empty() && new_extents.empty())
     return true;

   for (ex_t old_ex : old_extents)
     for (ex_t new_ex : new_extents)
       if (static_cast<uint64_t>(old_ex.off) < new_ex.off + new_ex.len &&
           static_cast<uint64_t>(new_ex.off) < old_ex.off + old_ex.len)
         return true;

   return false;
 }

 int bspatch(
     const char* old_filename, const char* new_filename,
     const char* patch_filename,
     const char* old_extents, const char* new_extents) {
   FILE* f, *cpf, *dpf, *epf;
   BZFILE* cpfbz2, *dpfbz2, *epfbz2;
   int bz2err;
   ssize_t bzctrllen, bzdatalen;
   u_char header[32], buf[8];
   off_t ctrl[3];

   int using_extents = (old_extents != NULL || new_extents != NULL);

   // Open patch file.
   if ((f = fopen(patch_filename, "r")) == NULL)
     err(1, "fopen(%s)", patch_filename);

   // File format:
   //   0       8    "BSDIFF40"
   //   8       8    X
   //   16      8    Y
   //   24      8    sizeof(new_filename)
   //   32      X    bzip2(control block)
   //   32+X    Y    bzip2(diff block)
   //   32+X+Y  ???  bzip2(extra block)
   // with control block a set of triples (x,y,z) meaning "add x bytes
   // from oldfile to x bytes from the diff block; copy y bytes from the
   // extra block; seek forwards in oldfile by z bytes".

   // Read header.
   if (fread(header, 1, 32, f) < 32) {
     if (feof(f))
       errx(1, "Corrupt patch\n");
     err(1, "fread(%s)", patch_filename);
   }

   // Check for appropriate magic.
   if (memcmp(header, "BSDIFF40", 8) != 0)
     errx(1, "Corrupt patch\n");

   // Read lengths from header.
   uint64_t oldsize, newsize;
   bzctrllen = ParseInt64(header + 8);
   bzdatalen = ParseInt64(header + 16);
   int64_t signed_newsize = ParseInt64(header + 24);
   newsize = signed_newsize;
   if ((bzctrllen < 0) || (bzdatalen < 0) || (signed_newsize < 0))
     errx(1, "Corrupt patch\n");

   // Close patch file and re-open it via libbzip2 at the right places.
   if (fclose(f))
     err(1, "fclose(%s)", patch_filename);
   if ((cpf = fopen(patch_filename, "r")) == NULL)
     err(1, "fopen(%s)", patch_filename);
   if (fseek(cpf, 32, SEEK_SET))
     err(1, "fseeko(%s, %lld)", patch_filename, (long long)32);
   if ((cpfbz2 = BZ2_bzReadOpen(&bz2err, cpf, 0, 0, NULL, 0)) == NULL)
     errx(1, "BZ2_bzReadOpen, bz2err = %d", bz2err);
   if ((dpf = fopen(patch_filename, "r")) == NULL)
     err(1, "fopen(%s)", patch_filename);
   if (fseek(dpf, 32 + bzctrllen, SEEK_SET))
     err(1, "fseeko(%s, %lld)", patch_filename, (long long)(32 + bzctrllen));
   if ((dpfbz2 = BZ2_bzReadOpen(&bz2err, dpf, 0, 0, NULL, 0)) == NULL)
     errx(1, "BZ2_bzReadOpen, bz2err = %d", bz2err);
   if ((epf = fopen(patch_filename, "r")) == NULL)
     err(1, "fopen(%s)", patch_filename);
   if (fseek(epf, 32 + bzctrllen + bzdatalen, SEEK_SET))
     err(1, "fseeko(%s, %lld)", patch_filename,
         (long long)(32 + bzctrllen + bzdatalen));
   if ((epfbz2 = BZ2_bzReadOpen(&bz2err, epf, 0, 0, NULL, 0)) == NULL)
     errx(1, "BZ2_bzReadOpen, bz2err = %d", bz2err);

   // Open input file for reading.
   std::unique_ptr<FileInterface> old_file = File::FOpen(old_filename, O_RDONLY);
   if (!old_file)
     err(1, "Error opening the old filename");

   std::vector<ex_t> parsed_old_extents;
   if (using_extents) {
     if (!ParseExtentStr(old_extents, &parsed_old_extents))
       errx(1, "Error parsing the old extents");
     old_file.reset(new ExtentsFile(std::move(old_file), parsed_old_extents));
   }

   if (!old_file->GetSize(&oldsize))
     err(1, "cannot obtain the size of %s", old_filename);
   uint64_t old_file_pos = 0;

   // Open output file for writing.
   std::unique_ptr<FileInterface> new_file =
       File::FOpen(new_filename, O_CREAT | O_WRONLY);
   if (!new_file)
     err(1, "Error opening the new filename %s", new_filename);

   std::vector<ex_t> parsed_new_extents;
   if (using_extents) {
     if (!ParseExtentStr(new_extents, &parsed_new_extents))
       errx(1, "Error parsing the new extents");
     new_file.reset(new ExtentsFile(std::move(new_file), parsed_new_extents));
   }

   if (IsOverlapping(old_filename, new_filename, parsed_old_extents,
                     parsed_new_extents)) {
     // New and old file is overlapping, we can not stream output to new file,
     // cache it in the memory and write to the file at the end.
     new_file.reset(new MemoryFile(std::move(new_file), newsize));
   }

   // The oldpos can be negative, but the new pos is only incremented linearly.
   int64_t oldpos = 0;
   uint64_t newpos = 0;
   std::vector<uint8_t> old_buf(1024 * 1024), new_buf(1024 * 1024);
   while (newpos < newsize) {
     int64_t i;
     // Read control data.
     for (i = 0; i <= 2; i++) {
       if (!ReadBZ2(cpfbz2, buf, 8))
         errx(1, "Corrupt patch\n");
       ctrl[i] = ParseInt64(buf);
     }

     // Sanity-check.
     if (ctrl[0] < 0 || ctrl[1] < 0)
       errx(1, "Corrupt patch\n");

     // Sanity-check.
     if (newpos + ctrl[0] > newsize)
       errx(1, "Corrupt patch\n");

     // Add old data to diff string. It is enough to fseek once, at
     // the beginning of the sequence, to avoid unnecessary overhead.
     if ((i = oldpos) < 0) {
       // Write diff block directly to new file without adding old data,
       // because we will skip part where |oldpos| < 0.
       if (!ReadBZ2AndWriteAll(new_file, dpfbz2, -i, new_buf.data(),
                               new_buf.size()))
         errx(1, "Error during ReadBZ2AndWriteAll()");

       i = 0;
     }

     // We just checked that |i| is not negative.
     if (static_cast<uint64_t>(i) != old_file_pos && !old_file->Seek(i))
       err(1, "error seeking input file to offset %" PRId64, i);
     if ((old_file_pos = oldpos + ctrl[0]) > oldsize)
       old_file_pos = oldsize;

     size_t chunk_size = old_file_pos - i;
     while (chunk_size > 0) {
       size_t read_bytes;
       size_t bytes_to_read = std::min(chunk_size, old_buf.size());
       if (!old_file->Read(old_buf.data(), bytes_to_read, &read_bytes))
         err(1, "error reading from input file");
       if (!read_bytes)
         errx(1, "EOF reached while reading from input file");
       // Read same amount of bytes from diff block
       if (!ReadBZ2(dpfbz2, new_buf.data(), read_bytes))
         errx(1, "Corrupt patch\n");
       // new_buf already has data from diff block, adds old data to it.
       for (size_t k = 0; k < read_bytes; k++)
         new_buf[k] += old_buf[k];
       if (!WriteAll(new_file, new_buf.data(), read_bytes))
         err(1, "Error writing new file.");
       chunk_size -= read_bytes;
     }

     // Adjust pointers.
     newpos += ctrl[0];
     oldpos += ctrl[0];

     if (oldpos > static_cast<int64_t>(oldsize)) {
       // Write diff block directly to new file without adding old data,
       // because we skipped part where |oldpos| > oldsize.
       if (!ReadBZ2AndWriteAll(new_file, dpfbz2, oldpos - oldsize,
                               new_buf.data(), new_buf.size()))
         errx(1, "Error during ReadBZ2AndWriteAll()");
     }

     // Sanity-check.
     if (newpos + ctrl[1] > newsize)
       errx(1, "Corrupt patch\n");

     // Read extra block.
     if (!ReadBZ2AndWriteAll(new_file, epfbz2, ctrl[1], new_buf.data(),
                             new_buf.size()))
       errx(1, "Error during ReadBZ2AndWriteAll()");

     // Adjust pointers.
     newpos += ctrl[1];
     oldpos += ctrl[2];
   }

   // Close input file.
   old_file->Close();

   // Clean up the bzip2 reads.
   BZ2_bzReadClose(&bz2err, cpfbz2);
   BZ2_bzReadClose(&bz2err, dpfbz2);
   BZ2_bzReadClose(&bz2err, epfbz2);
   if (fclose(cpf) || fclose(dpf) || fclose(epf))
     err(1, "fclose(%s)", patch_filename);

   if (!new_file->Close())
     err(1, "Error closing new file %s", new_filename);

   return 0;
 }

 }  // namespace bsdiff
	/*-
	* Copyright 2003-2005 Colin Percival
	* All rights reserved
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted providing that the following conditions
	* are met:
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	*
	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
	* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
	* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
	* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
	* POSSIBILITY OF SUCH DAMAGE.
	*/

	#if 0
	__FBSDID("$FreeBSD: src/usr.bin/bsdiff/bspatch/bspatch.c,v 1.1 2005/08/06 01:59:06 cperciva Exp $");
	#endif

	#include "bspatch.h"

	#include <bzlib.h>
	#include <err.h>
	#include <errno.h>
	#include <fcntl.h>
	#include <inttypes.h>
	#include <stdlib.h>
	#include <string.h>
	#include <unistd.h>
	#include <sys/stat.h>
	#include <sys/types.h>

	#include <algorithm>
	#include <memory>
	#include <limits>
	#include <vector>

	#include "extents.h"
	#include "extents_file.h"
	#include "file.h"
	#include "file_interface.h"
	#include "memory_file.h"

	namespace {

	int64_t ParseInt64(u_char* buf) {
	int64_t y;

	y = buf[7] & 0x7F;
	y = y * 256;
	y += buf[6];
	y = y * 256;
	y += buf[5];
	y = y * 256;
	y += buf[4];
	y = y * 256;
	y += buf[3];
	y = y * 256;
	y += buf[2];
	y = y * 256;
	y += buf[1];
	y = y * 256;
	y += buf[0];

	if (buf[7] & 0x80)
	y = -y;

	return y;
	}

	bool ReadBZ2(BZFILE* pfbz2, uint8_t* data, size_t size) {
	int bz2err;
	size_t lenread = BZ2_bzRead(&bz2err, pfbz2, data, size);
	if (lenread < size \|\| (bz2err != BZ_OK && bz2err != BZ_STREAM_END))
	return false;
	return true;
	}

	bool ReadBZ2AndWriteAll(const std::unique_ptr<bsdiff::FileInterface>& file,
	BZFILE* pfbz2,
	size_t size,
	uint8_t* buf,
	size_t buf_size) {
	while (size > 0) {
	size_t bytes_to_read = std::min(size, buf_size);
	if (!ReadBZ2(pfbz2, buf, bytes_to_read))
	return false;
	if (!WriteAll(file, buf, bytes_to_read))
	return false;
	size -= bytes_to_read;
	}
	return true;
	}

	} // namespace

	namespace bsdiff {

	bool WriteAll(const std::unique_ptr<FileInterface>& file,
	const uint8_t* data,
	size_t size) {
	size_t offset = 0, written;
	while (offset < size) {
	if (!file->Write(data + offset, size - offset, &written) \|\| written == 0)
	return false;
	offset += written;
	}
	return true;
	}

	bool IsOverlapping(const char* old_filename,
	const char* new_filename,
	const std::vector<ex_t>& old_extents,
	const std::vector<ex_t>& new_extents) {
	struct stat old_stat, new_stat;
	if (stat(new_filename, &new_stat) == -1) {
	if (errno == ENOENT)
	return false;
	err(1, "Error stat the new filename %s", new_filename);
	}
	if (stat(old_filename, &old_stat) == -1)
	err(1, "Error stat the old filename %s", old_filename);

	if (old_stat.st_dev != new_stat.st_dev \|\| old_stat.st_ino != new_stat.st_ino)
	return false;

	if (old_extents.empty() && new_extents.empty())
	return true;

	for (ex_t old_ex : old_extents)
	for (ex_t new_ex : new_extents)
	if (static_cast<uint64_t>(old_ex.off) < new_ex.off + new_ex.len &&
	static_cast<uint64_t>(new_ex.off) < old_ex.off + old_ex.len)
	return true;

	return false;
	}

	int bspatch(
	const char* old_filename, const char* new_filename,
	const char* patch_filename,
	const char* old_extents, const char* new_extents) {
	FILE* f, cpf, dpf, *epf;
	BZFILE* cpfbz2, dpfbz2, epfbz2;
	int bz2err;
	ssize_t bzctrllen, bzdatalen;
	u_char header[32], buf[8];
	off_t ctrl[3];

	int using_extents = (old_extents != NULL \|\| new_extents != NULL);

	// Open patch file.
	if ((f = fopen(patch_filename, "r")) == NULL)
	err(1, "fopen(%s)", patch_filename);

	// File format:
	// 0 8 "BSDIFF40"
	// 8 8 X
	// 16 8 Y
	// 24 8 sizeof(new_filename)
	// 32 X bzip2(control block)
	// 32+X Y bzip2(diff block)
	// 32+X+Y ??? bzip2(extra block)
	// with control block a set of triples (x,y,z) meaning "add x bytes
	// from oldfile to x bytes from the diff block; copy y bytes from the
	// extra block; seek forwards in oldfile by z bytes".

	// Read header.
	if (fread(header, 1, 32, f) < 32) {
	if (feof(f))
	errx(1, "Corrupt patch\n");
	err(1, "fread(%s)", patch_filename);
	}

	// Check for appropriate magic.
	if (memcmp(header, "BSDIFF40", 8) != 0)
	errx(1, "Corrupt patch\n");

	// Read lengths from header.
	uint64_t oldsize, newsize;
	bzctrllen = ParseInt64(header + 8);
	bzdatalen = ParseInt64(header + 16);
	int64_t signed_newsize = ParseInt64(header + 24);
	newsize = signed_newsize;
	if ((bzctrllen < 0) \|\| (bzdatalen < 0) \|\| (signed_newsize < 0))
	errx(1, "Corrupt patch\n");

	// Close patch file and re-open it via libbzip2 at the right places.
	if (fclose(f))
	err(1, "fclose(%s)", patch_filename);
	if ((cpf = fopen(patch_filename, "r")) == NULL)
	err(1, "fopen(%s)", patch_filename);
	if (fseek(cpf, 32, SEEK_SET))
	err(1, "fseeko(%s, %lld)", patch_filename, (long long)32);
	if ((cpfbz2 = BZ2_bzReadOpen(&bz2err, cpf, 0, 0, NULL, 0)) == NULL)
	errx(1, "BZ2_bzReadOpen, bz2err = %d", bz2err);
	if ((dpf = fopen(patch_filename, "r")) == NULL)
	err(1, "fopen(%s)", patch_filename);
	if (fseek(dpf, 32 + bzctrllen, SEEK_SET))
	err(1, "fseeko(%s, %lld)", patch_filename, (long long)(32 + bzctrllen));
	if ((dpfbz2 = BZ2_bzReadOpen(&bz2err, dpf, 0, 0, NULL, 0)) == NULL)
	errx(1, "BZ2_bzReadOpen, bz2err = %d", bz2err);
	if ((epf = fopen(patch_filename, "r")) == NULL)
	err(1, "fopen(%s)", patch_filename);
	if (fseek(epf, 32 + bzctrllen + bzdatalen, SEEK_SET))
	err(1, "fseeko(%s, %lld)", patch_filename,
	(long long)(32 + bzctrllen + bzdatalen));
	if ((epfbz2 = BZ2_bzReadOpen(&bz2err, epf, 0, 0, NULL, 0)) == NULL)
	errx(1, "BZ2_bzReadOpen, bz2err = %d", bz2err);

	// Open input file for reading.
	std::unique_ptr<FileInterface> old_file = File::FOpen(old_filename, O_RDONLY);
	if (!old_file)
	err(1, "Error opening the old filename");

	std::vector<ex_t> parsed_old_extents;
	if (using_extents) {
	if (!ParseExtentStr(old_extents, &parsed_old_extents))
	errx(1, "Error parsing the old extents");
	old_file.reset(new ExtentsFile(std::move(old_file), parsed_old_extents));
	}

	if (!old_file->GetSize(&oldsize))
	err(1, "cannot obtain the size of %s", old_filename);
	uint64_t old_file_pos = 0;

	// Open output file for writing.
	std::unique_ptr<FileInterface> new_file =
	File::FOpen(new_filename, O_CREAT \| O_WRONLY);
	if (!new_file)
	err(1, "Error opening the new filename %s", new_filename);

	std::vector<ex_t> parsed_new_extents;
	if (using_extents) {
	if (!ParseExtentStr(new_extents, &parsed_new_extents))
	errx(1, "Error parsing the new extents");
	new_file.reset(new ExtentsFile(std::move(new_file), parsed_new_extents));
	}

	if (IsOverlapping(old_filename, new_filename, parsed_old_extents,
	parsed_new_extents)) {
	// New and old file is overlapping, we can not stream output to new file,
	// cache it in the memory and write to the file at the end.
	new_file.reset(new MemoryFile(std::move(new_file), newsize));
	}

	// The oldpos can be negative, but the new pos is only incremented linearly.
	int64_t oldpos = 0;
	uint64_t newpos = 0;
	std::vector<uint8_t> old_buf(1024 * 1024), new_buf(1024 * 1024);
	while (newpos < newsize) {
	int64_t i;
	// Read control data.
	for (i = 0; i <= 2; i++) {
	if (!ReadBZ2(cpfbz2, buf, 8))
	errx(1, "Corrupt patch\n");
	ctrl[i] = ParseInt64(buf);
	}

	// Sanity-check.
	if (ctrl[0] < 0 \|\| ctrl[1] < 0)
	errx(1, "Corrupt patch\n");

	// Sanity-check.
	if (newpos + ctrl[0] > newsize)
	errx(1, "Corrupt patch\n");

	// Add old data to diff string. It is enough to fseek once, at
	// the beginning of the sequence, to avoid unnecessary overhead.
	if ((i = oldpos) < 0) {
	// Write diff block directly to new file without adding old data,
	// because we will skip part where \|oldpos\| < 0.
	if (!ReadBZ2AndWriteAll(new_file, dpfbz2, -i, new_buf.data(),
	new_buf.size()))
	errx(1, "Error during ReadBZ2AndWriteAll()");

	i = 0;
	}

	// We just checked that \|i\| is not negative.
	if (static_cast<uint64_t>(i) != old_file_pos && !old_file->Seek(i))
	err(1, "error seeking input file to offset %" PRId64, i);
	if ((old_file_pos = oldpos + ctrl[0]) > oldsize)
	old_file_pos = oldsize;

	size_t chunk_size = old_file_pos - i;
	while (chunk_size > 0) {
	size_t read_bytes;
	size_t bytes_to_read = std::min(chunk_size, old_buf.size());
	if (!old_file->Read(old_buf.data(), bytes_to_read, &read_bytes))
	err(1, "error reading from input file");
	if (!read_bytes)
	errx(1, "EOF reached while reading from input file");
	// Read same amount of bytes from diff block
	if (!ReadBZ2(dpfbz2, new_buf.data(), read_bytes))
	errx(1, "Corrupt patch\n");
	// new_buf already has data from diff block, adds old data to it.
	for (size_t k = 0; k < read_bytes; k++)
	new_buf[k] += old_buf[k];
	if (!WriteAll(new_file, new_buf.data(), read_bytes))
	err(1, "Error writing new file.");
	chunk_size -= read_bytes;
	}

	// Adjust pointers.
	newpos += ctrl[0];
	oldpos += ctrl[0];

	if (oldpos > static_cast<int64_t>(oldsize)) {
	// Write diff block directly to new file without adding old data,
	// because we skipped part where \|oldpos\| > oldsize.
	if (!ReadBZ2AndWriteAll(new_file, dpfbz2, oldpos - oldsize,
	new_buf.data(), new_buf.size()))
	errx(1, "Error during ReadBZ2AndWriteAll()");
	}

	// Sanity-check.
	if (newpos + ctrl[1] > newsize)
	errx(1, "Corrupt patch\n");

	// Read extra block.
	if (!ReadBZ2AndWriteAll(new_file, epfbz2, ctrl[1], new_buf.data(),
	new_buf.size()))
	errx(1, "Error during ReadBZ2AndWriteAll()");

	// Adjust pointers.
	newpos += ctrl[1];
	oldpos += ctrl[2];
	}

	// Close input file.
	old_file->Close();

	// Clean up the bzip2 reads.
	BZ2_bzReadClose(&bz2err, cpfbz2);
	BZ2_bzReadClose(&bz2err, dpfbz2);
	BZ2_bzReadClose(&bz2err, epfbz2);
	if (fclose(cpf) \|\| fclose(dpf) \|\| fclose(epf))
	err(1, "fclose(%s)", patch_filename);

	if (!new_file->Close())
	err(1, "Error closing new file %s", new_filename);

	return 0;
	}

	} // namespace bsdiff