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open-vcdiff README
open-vcdiff is an encoder and decoder for the VCDIFF format, as described in RFC 3284: The VCDIFF Generic Differencing and Compression Data Format.
You will need to first synchronize gflags and gtest by running
git submodule update --init --recursive
. Or if you have system installed
gflags and/or gtest libraries you can provide -Dvcdiff_use_system_gflags=ON
and -Dvcdiff_use_system_gtest=ON
for cmake
invokation in the build
step.
A library with a simple API is included, as well as a command-line executable that can apply the encoder and decoder to source, target, and delta files. For further details, please refer to this link.
open-vcdiff comes with a CMake build script ( CMakeLists.txt) that can be used on a wide range of platforms ("C" stands for cross-platform.). If you don't have CMake installed already, you can download it for free from http://www.cmake.org/.
CMake works by generating native makefiles or build projects that can be used in the compiler environment of your choice. The typical workflow starts with:
mkdir mybuild # Create a directory to hold the build output.
cd mybuild
cmake ${OPEN_VCDIFF_DIR} # Generate native build scripts.
If you want to disable build of build tests and/or executable and build libraries only replace last command with
cmake -Dvcdiff_build_test=OFF -Dvcdiff_build_exec=OFF ${OPEN_VCDIFF_DIR}
If you are on a *nix system, you should now see a Makefile in the current directory. Just type 'make' to build gtest.
If you use Windows and have Visual Studio installed, a gtest.sln
file
and several .vcproj
files will be created. You can then build them
using Visual Studio.
On Mac OS X with Xcode installed, a .xcodeproj
file will be generated.
After compilation you should have the unit tests as well as vcdiff
, a simple
command-line utility to run the encoder and decoder. Typical usage of vcdiff is
as follows (the <
and >
are file redirect operations, not optional
arguments):
vcdiff encode -dictionary file.dict < target_file > delta_file
vcdiff decode -dictionary file.dict < delta_file > target_file
To see the command-line syntax of vcdiff, use vcdiff --help
or just vcdiff
.
To run tests just use make test
inside build directory.
To call the encoder from C++ code, assuming that dictionary, target, and delta
are all std::string
objects:
#include <google/vcencoder.h> // Read this file for interface details
// [...]
open_vcdiff::VCDiffEncoder encoder(dictionary.data(), dictionary.size());
encoder.SetFormatFlags(open_vcdiff::VCD_FORMAT_INTERLEAVED);
encoder.Encode(target.data(), target.size(), &delta);
Calling the decoder is just as simple:
#include <google/vcdecoder.h> // Read this file for interface details
// [...]
open_vcdiff::VCDiffDecoder decoder;
decoder.Decode(dictionary.data(), dictionary.size(), delta, &target);
When using the encoder, the C++ application must be linked with the library
options -lvcdcom
and -lvcdenc
; when using the decoder, it must be linked
with -lvcdcom
and -lvcddec
.
To verify that the package works on your system, especially after making
modifications to the source code, please run the unit tests using make check
.
For further details, please refer to this link.