XCompressAnalyzer

A Windows-only C# console application that analyzes Xbox 360 XMemCompress LZXNATIVE compressed blobs (the "Manual Decompression" format produced by xbcompress /n). It parses the file header, prints all codec parameters and size information, enumerates compressed blocks, and optionally validates the decompression context using xcompress.dll.

Features

• Pure analysis — no extraction or compression performed
• Loads xcompress.dll via P/Invoke
• Parses LZXNATIVE format (magic 0x0FF512EE, version 1.3)
• Prints all header fields: magic, version, context flags, codec params, sizes, block config
• Enumerates compressed blocks with sizes and offsets (-v / --verbose)
• Validates decompression context against xcompress.dll (--validate)

Requirements

• Windows x64 (the P/Invoke target is xcompress.dll)
• xcompress.dll (x64) must be present in the same directory as the executable, or in a x64/ subdirectory

Building

dotnet publish -c Release -r win-x64 -p:PublishSingleFile=true

Output: bin/Release/net8.0-windows/win-x64/publish/XCompressAnalyzer.exe

Usage

XCompressAnalyzer.exe <file> [options]

Options:
  -v, --verbose     Show detailed block information
  --validate        Validate decompression context creation with xcompress.dll

Example

XCompressAnalyzer.exe compressed.dat --verbose --validate

Output Format

=== XCompress LZXNATIVE Analysis: compressed.dat ===
File size: 67,584 bytes (66.00 KB)
Endianness: Big-Endian (Xbox 360 native)

--- File Header (XCOMPRESS_FILE_HEADER_LZXNATIVE) ---
  Magic (Identifier):     0x0FF512EE (LZXNATIVE Big-Endian, Xbox 360 native)
  Version:                0x01030000 (Major: 1, Minor: 3)
  Reserved:               0x00000000
  ContextFlags:           0x00000000 (None (standard))

--- Codec Parameters (XMEMCODEC_PARAMETERS_LZX) ---
  WindowSize:             262,144 bytes (256 KB)  <-- xbcompress /w flag
  CompressionPartitionSize: 524,288 bytes (512 KB)  <-- xbcompress /p flag

--- Size Information ---
  UncompressedSize:       8,388,616 bytes (8.00 MB)
  CompressedSize:         66,000 bytes (0.06 MB)
  Compression Ratio:      0.8% of original (99.2% reduction)

--- Block Configuration ---
  UncompressedBlockSize:  1,048,576 bytes (1024 KB)  <-- xbcompress /n flag
  CompressedBlockSizeMax: 31,204 bytes (30.5 KB)

Version 1.3: Standard LZXNATIVE format (Xbox 360 File Compression Tool)
--- Compressed Blocks ---
  Block 0: CompressedSize=4,554 bytes, Offset=0x00000034
  Block 1: CompressedSize=1,382 bytes, Offset=0x00001202
  ...
  Total blocks: 9

--- Decompression Context Validation ---
  XMemGetDecompressionContextSize failed: 0x0003315D
  XMemCreateDecompressionContext: SUCCESS
  Context handle: 0x1037A10

File Format

The tool expects the Xbcompress LZXNATIVE header layout (48 bytes), which is the format produced by xbcompress /n:1024 /w:256:

XCOMPRESS_FILE_HEADER (12 bytes):
  Identifier (4)   = 0x0FF512EE
  Version (4)      = 0x01030000
  Reserved (4)     = 0

ContextFlags (4)   = 0

Codec Parameters (8 bytes):
  WindowSize (4)              = xbcompress /w value in KB * 1024
  CompressionPartitionSize (4)= xbcompress /p value in KB * 1024

Size Fields (16 bytes):
  UncompressedSizeHigh (4)
  UncompressedSizeLow  (4)
  CompressedSizeHigh   (4)
  CompressedSizeLow    (4)

Block Config (8 bytes):
  UncompressedBlockSize (4)   = xbcompress /n value in KB * 1024
  CompressedBlockSizeMax (4)

Followed by a sequence of compressed blocks:

[BlockSize:4 (BE)] [CompressedData:BlockSize] ...

Note

• OpenCode's Zen models were used during the development and testing phase for this project.

License

• FreeMote License for the FreeMote.XMemCompress package. Anything else is under the MIT License.