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Minimal LZMA Project (minlzma)

<img align="left" src="minlzma.png" width="72"/> The Minimal LZMA (minlzma) project aims to provide a minimalistic, cross-platform, highly commented, standards-compliant C library (minlzlib) for decompressing LZMA2-encapsulated compressed data in LZMA format within an XZ container, as can be generated with Python 3.6, 7-zip, and xzutils. Additionally, a simple, portable, command-line tool (minlzdec) is provided for excercising the functionality on a provided input file.

External Interface

/*!
 * @brief          Decompresses an XZ stream from InputBuffer into OutputBuffer.
 *
 * @detail         The XZ stream must contain a single block with an LZMA2 filter
 *                 and no BJC2 filters, using default LZMA properties, and using
 *                 either CRC-64, CRC-32, or None as the checksum type (unknown
 *                 checksum algorithms will be safely ignored, however).
 *
 * @param[in]      InputBuffer - A fully formed buffer containing the XZ stream.
 * @param[in]      InputSize - The size of the input buffer.
 * @param[in]      OutputBuffer - A fully allocated buffer to receive the output.
 *                 Callers can pass in NULL if they do not intend to decompress,
 *                 in combination with setting OutputSize to 0, in order to query
 *                 the final expected size of the decompressed buffer.
 * @param[in,out]  OutputSize - On input, the size of the buffer. On output, the
 *                 size of the decompressed result.
 *
 * @return         true - The input buffer was fully decompressed in OutputBuffer,
 *                 or no decompression was requested, the size of the decompressed
 *                 buffer was returned in OutputSIze.
 *                 false - A failure occurred during the decompression process.
 */
bool
XzDecode (
    const uint8_t* InputBuffer,
    uint32_t InputSize,
    uint8_t* OutputBuffer,
    uint32_t* OutputSize
    );

/*!
 * @brief          Returns if the last call to XzDecode resulted in an integrity
 *                 error.
 *
 * @detail         Checksum errors can indicate either the uncompressed block's
 *                 CRC-32 or CRC-64 checksum being corrupt, or any of the meta-
 *                 data CRC-32 checksums in the header, footer, or index.
 *
 * @return         true - A checksum error was encountered at some point.
 *                 false - No error was encountered or integrity checks are not
 *                 enabled.
 */
bool
XzChecksumError (
    void
    );

Limitations and Restrictions

In order to provide its vast simplicity, fast performance, minimal source, and small compiled size, minlzlib makes certain assumptions about the input file and has certain restrictions or limitations:

Note that while these assumptions may seem overly restrictive, they correspond to the usual files produced by xzutils, 7-zip when choosing XZ as the format, and the Python LZMA module. Most encoders do not support the vast majority of XZ/LZMA2's purported capabilities such as multiple blocks, streaming, or multi-threading.

Testing (Linux)

Testing (Windows)

Compile-time Options

Usage

minlzdec v.1.1.5 -- http://ionescu007.github.io/minlzma
Copyright(c) 2020-2021 Alex Ionescu (@aionescu)

Usage: minlzdec [INPUT FILE] [OUTPUT FILE]
Decompress INPUT FILE in the .xz format into OUTPUT FILE.

Build Instructions

Within Visual Studio 2019, you can use File->Open->CMake and point it at the top-level CMakeFiles.txt, and choose either the win-amd64 target or the win-release-amd64 target. The former builds a binary with no optimizations, the later builds a fully optimized binary (for speed) with debug symbols.

If you use WSL, ...

For Linux native builds, ...

Acknowledgments

The author would like to thank the shoulders of the following giants, whose code, documentation, and writing was monumental in this effort:

The author would also like to thank the following reviwers for identifying various bugs, typos, and other improvements: