130 lines
4.9 KiB
Markdown
130 lines
4.9 KiB
Markdown
bsdiff/bspatch
|
|
==============
|
|
bsdiff and bspatch are libraries for building and applying patches to binary
|
|
files.
|
|
|
|
The original algorithm and implementation was developed by Colin Percival. The
|
|
algorithm is detailed in his (unpublished) paper, [Naïve Differences of Executable Code](http://www.daemonology.net/papers/bsdiff.pdf). For more information, visit his
|
|
website at <http://www.daemonology.net/bsdiff/>.
|
|
|
|
I maintain this project seperately from Colin's work, with the goal of making
|
|
the core functionality easily embedable in existing projects.
|
|
|
|
Contact
|
|
-------
|
|
[@MatthewEndsley](https://twitter.com/#!/MatthewEndsley)
|
|
<https://github.com/mendsley/bsdiff>
|
|
|
|
License
|
|
-------
|
|
Copyright 2003-2005 Colin Percival
|
|
Copyright 2012 Matthew Endsley
|
|
|
|
This project is governed by the BSD 2-clause license. For details see the file
|
|
titled LICENSE in the project root folder.
|
|
|
|
Overview
|
|
--------
|
|
There are two separate libraries in the project, bsdiff and bspatch. Each are
|
|
self contained in bsdiff.c and bspatch.c The easiest way to integrate is to
|
|
simply copy the c file to your source folder and build it.
|
|
|
|
The overarching goal was to modify the original bsdiff/bspatch code from Colin
|
|
and eliminate external dependencies and provide a simple interface to the core
|
|
functionality.
|
|
|
|
I've exposed relevant functions via the `_stream` classes. The only external
|
|
dependency not exposed is `memcmp` in `bsdiff`.
|
|
|
|
This library generates patches that are not compatible with the original bsdiff
|
|
tool. The impompatibilities were motivated by the patching needs for the game
|
|
AirMech <https://www.carbongames.com> and the following requirements:
|
|
|
|
* Eliminate/minimize any seek operations when applying patches
|
|
* Eliminate any required disk I/O and support embedded streams
|
|
* Ability to easily embed the routines as a library instead of an external binary
|
|
* Compile+run on all platforms we use to build the game (Windows, Linux, NaCl, OSX)
|
|
|
|
Compiling
|
|
---------
|
|
The libraries should compile warning free in any moderately recent version of
|
|
gcc. The project uses `<stdint.h>` which is technically a C99 file and not
|
|
available in Microsoft Visual Studio. The easiest solution here is to use the
|
|
msinttypes version of stdint.h from <https://code.google.com/p/msinttypes/>.
|
|
The direct link for the lazy people is:
|
|
<https://msinttypes.googlecode.com/svn/trunk/stdint.h>.
|
|
|
|
If your compiler does not provide an implementation of `<stdint.h>` you can
|
|
remove the header from the bsdiff/bspatch files and provide your own typedefs
|
|
for the following symbols: `uint8_t`, `uint64_t` and `int64_t`.
|
|
|
|
Examples
|
|
--------
|
|
Each project has an optional main function that serves as an example for using
|
|
the library. Simply defined `BSDIFF_EXECUTABLE` or `BSPATCH_EXECUTABLE` to
|
|
enable building the standalone tools.
|
|
|
|
Reference
|
|
---------
|
|
### bsdiff
|
|
|
|
struct bsdiff_stream
|
|
{
|
|
void* opaque;
|
|
void* (*malloc)(size_t size);
|
|
void (*free)(void* ptr);
|
|
int (*write)(struct bsdiff_stream* stream,
|
|
const void* buffer, int size);
|
|
};
|
|
|
|
int bsdiff(const uint8_t* old, int64_t oldsize, const uint8_t* new,
|
|
int64_t newsize, struct bsdiff_stream* stream);
|
|
|
|
|
|
In order to use `bsdiff`, you need to define functions for allocating memory and
|
|
writing binary data. This behavior is controlled by the `stream` parameted
|
|
passed to to `bsdiff(...)`.
|
|
|
|
The `opaque` field is never read or modified from within the `bsdiff` function.
|
|
The caller can use this field to store custom state data needed for the callback
|
|
functions.
|
|
|
|
The `malloc` and `free` members should point to functions that behave like the
|
|
standard `malloc` and `free` C functions.
|
|
|
|
The `write` function is called by bsdiff to write a block of binary data to the
|
|
stream. The return value for `write` should be `0` on success and non-zero if
|
|
the callback failed to write all data. In the default example, bzip2 is used to
|
|
compress output data.
|
|
|
|
`bsdiff` returns `0` on success and `-1` on failure.
|
|
|
|
### bspatch
|
|
|
|
struct bspatch_stream
|
|
{
|
|
void* opaque;
|
|
int (*read)(const struct bspatch_stream* stream,
|
|
void* buffer, int length);
|
|
};
|
|
|
|
int bspatch(const uint8_t* old, int64_t oldsize, uint8_t* new,
|
|
int64_t newsize, struct bspatch_stream* stream);
|
|
|
|
The `bspatch` function transforms the data for a file using data generated from
|
|
`bsdiff`. The caller takes care of loading the old file and allocating space for
|
|
new file data. The `stream` parameter controls the process for reading binary
|
|
patch data.
|
|
|
|
The `opaque` field is never read or modified from within the bspatch function.
|
|
The caller can use this field to store custom state data needed for the read
|
|
function.
|
|
|
|
The `read` function is called by `bspatch` to read a block of binary data from
|
|
the stream. The return value for `read` should be `0` on success and non-zero
|
|
if the callback failed to read the requested amount of data. In the default
|
|
example, bzip2 is used to decompress input data.
|
|
|
|
`bspatch` returns `0` on success and `-1` on failure. On success, `new` contains
|
|
the data for the patched file.
|