bsdiff

bsdiff is a library for building and applying patches to binary files.

The original algorithm and implementation was developed by Colin Percival. The algorithm is described in his (unpublished) paper. For more information visit his website at http://www.daemonology.net/bsdiff/.

I maintain this project separately from Colin's work, with the following goals:

• Ability to easily embed the routines as a library instead of an external binary.
• Compatible with the original patch format and can easily adapt to new patch format.
• Support memory-based input/output stream.
• Self-contained 3rd-party libraries, build on Windows/Linux/OSX.

API

/**
 * @brief
 *    Generate a patch between two binary files.
 * @param ctx
 *    The context.
 * @param oldfile
 *    The stream of the old file.
 * @param newfile
 *    The stream of the new file.
 * @param packer
 *    The packer.
 * @return
 *    BSDIFF_SUCCESS if no error.
 */
BSDIFF_API
int bsdiff(
	struct bsdiff_ctx *ctx,
	struct bsdiff_stream *oldfile, 
	struct bsdiff_stream *newfile, 
	struct bsdiff_patch_packer *packer);

/**
 * @brief
 *    Apply the patch to the old file, re-create the new file.
 * @param ctx
 *    The context.
 * @param oldfile
 *    The stream of the old file.
 * @param newfile
 *    The stream of the new file.
 * @param packer
 *    The packer.
 * @return
 *    BSDIFF_SUCCESS if no error.
 */
BSDIFF_API
int bspatch(
	struct bsdiff_ctx *ctx,
	struct bsdiff_stream *oldfile, 
	struct bsdiff_stream *newfile,
	struct bsdiff_patch_packer *packer);

Demo Usage

#include <stdio.h>
#include "bsdiff.h"

static void log_error(void *opaque, const char *errmsg)
{
	(void)opaque;
	fprintf(stderr, "%s", errmsg);
}

int generate_patch(const char *oldname, const char *newname, const char *patchname)
{
	int ret = 1;
	struct bsdiff_stream oldfile = { 0 }, newfile = { 0 }, patchfile = { 0 };
	struct bsdiff_ctx ctx = { 0 };
	struct bsdiff_patch_packer packer = { 0 };

	ret = bsdiff_open_file_stream(BSDIFF_MODE_READ, oldname, &oldfile);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't open oldfile: %s\n", oldname);
		goto cleanup;
	}
	ret = bsdiff_open_file_stream(BSDIFF_MODE_READ, newname, &newfile);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't open newfile: %s\n", newname);
		goto cleanup;
	}
	ret = bsdiff_open_file_stream(BSDIFF_MODE_WRITE, patchname, &patchfile);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't open patchfile: %s\n", patchname);
		goto cleanup;
	}
	ret = bsdiff_open_bz2_patch_packer(BSDIFF_MODE_WRITE, &patchfile, &packer);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't create BZ2 patch packer\n");
		goto cleanup;
	}

	ctx.log_error = log_error;

	ret = bsdiff(&ctx, &oldfile, &newfile, &packer);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "bsdiff failed: %d\n", ret);
		goto cleanup;
	}

cleanup:
	bsdiff_close_patch_packer(&packer);
	bsdiff_close_stream(&patchfile);
	bsdiff_close_stream(&newfile);
	bsdiff_close_stream(&oldfile);

	return ret;
}

int apply_patch(const char *oldname, const char *newname, const char *patchname)
{
	int ret = 1;
	struct bsdiff_stream oldfile = { 0 }, newfile = { 0 }, patchfile = { 0 };
	struct bsdiff_ctx ctx = { 0 };
	struct bsdiff_patch_packer packer = { 0 };

	ret = bsdiff_open_file_stream(BSDIFF_MODE_READ, oldname, &oldfile);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't open oldfile: %s\n", oldname);
		goto cleanup;
	}
	ret = bsdiff_open_file_stream(BSDIFF_MODE_WRITE, newname, &newfile);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't open newfile: %s\n", newname);
		goto cleanup;
	}
	ret = bsdiff_open_file_stream(BSDIFF_MODE_READ, patchname, &patchfile);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't open patchfile: %s\n", patchname);
		goto cleanup;
	}
	ret = bsdiff_open_bz2_patch_packer(BSDIFF_MODE_READ, &patchfile, &packer);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "can't create BZ2 patch packer\n");
		goto cleanup;
	}

	ctx.log_error = log_error;
	
	ret = bspatch(&ctx, &oldfile, &newfile, &packer);
	if (ret != BSDIFF_SUCCESS) {
		fprintf(stderr, "bspatch failed: %d\n", ret);
		goto cleanup;
	}

cleanup:
	bsdiff_close_patch_packer(&packer);
	bsdiff_close_stream(&patchfile);
	bsdiff_close_stream(&newfile);
	bsdiff_close_stream(&oldfile);

	return ret;
}