Clean-room C implementation of the Windows Imaging (WIM) format. Creates, extracts, and inspects WIM archives compatible with Microsoft DISM, ImageX, and wimlib-imagex.

Not a fork of wimlib. Every component (XPRESS Huffman codec, SHA-1 deduplication, metadata serializer, bitstream encoder) was written from scratch based on format analysis alone.

cmake -B build
cmake --build build

# Capture a directory
./build/wimage capture /my/files backup.wim "My Backup" --compress=xpress --threads=4

# List contents
./build/wimage dir backup.wim

# Extract
./build/wimage apply backup.wim 1 /restore/here

# Verify integrity
./build/wimage capture /data archive.wim "Data" --check
./build/wimage verify archive.wim

wimage capture <source> <wimfile> [name] [--compress=xpress|none] [--threads=N] [--check]
wimage apply   <wimfile> [image] <target>
wimage info    <wimfile> [--header] [--xml] [--blobs]
wimage dir     <wimfile> [--detailed]
wimage verify  <wimfile>
wimage extract <wimfile> <image> [paths...] [--dest-dir=DIR]

• XPRESS Huffman compression and decompression
• SHA-1 content-addressed deduplication
• Multi-threaded compression
• Integrity table generation and verification
• Full interoperability with wimlib-imagex and Microsoft DISM

libwim/ is a self-contained pure C11 library with zero external dependencies. Copy the directory into your project and compile:

#include "wim_read.h"

WimCtx ctx;
wim_ctx_init(&ctx);
wim_open(&ctx, "image.wim");
wim_select_image(&ctx, 1);
wim_extract_tree(&ctx, wim_get_root(&ctx, 1), "/output");
wim_close(&ctx);

Designed for constrained environments: bootloaders, firmware, OS installers.

Linux x86_64, GCC -O3, OpenSSL SHA-1, SSE2 codec hot paths, 32-core host, wimlib-imagex 1.13.6. Mixed synthetic data, ~75 % compression ratio. Reproduced with scripts/test_smp_big.py.

Single-threaded wimage is within 10 % of wimlib (the 16-byte SSE2 match_len closes most of the old gap). At SMP8+ the persistent thread pool + fused XPRESS emit pass beat wimlib by ~20 %.

Wimage decompresses wimlib-compressed WIMs and vice-versa; SHA-1 of the extracted file matches bit-for-bit in both directions. The match-copy fast path uses _mm_loadu_si128/_mm_storeu_si128 when the match offset is ≥ 16 bytes (the common case), bringing decode to within 6 % of wimlib's hand-tuned decoder.

# Unit tests
cmake -B build -DENABLE_TESTS=ON && cmake --build build
./build/wimage_tests    # 118 tests

# Integration tests (requires wimlib-imagex)
cd scripts && python3 test_compare.py && python3 test_random250.py

GPL-2.0-or-later