lz4.CompressionOptions

CompressionOptions configures how data is compressed into LZ4 frames and blocks.

pub const CompressionOptions = struct {
    level: i32 = 1,
    acceleration: u32 = 1,
    blockMaxSize: BlockMaxSize = .max64KB,
    blockMode: BlockMode = .independent,
    contentChecksum: bool = true,
    blockChecksum: bool = false,
    contentSize: ?u64 = null,
    dictId: ?u32 = null,
    customDictionary: ?[]const u8 = null,
    favorDecSpeed: bool = false,
    autoFlush: bool = true,
};

---

Fields

level

• Type: i32
• Default: 1
• Description: Compression mode selector:
  • 1: Standard Fast LZ4 engine.
  • 2..12: High-Compression (HC) engine with deeper match parsing. Level 9 is the standard HC recommended setting.

acceleration

• Type: u32
• Default: 1
• Description: Speed acceleration step for level 1. Values higher than 1 (e.g., 2, 4, 8) skip search probes to increase encoding throughput at a modest cost in compression ratio.

blockMaxSize

• Type: BlockMaxSize
• Default: .max64KB
• Options:
  • .max64KB: 64 KiB blocks (low memory overhead).
  • .max256KB: 256 KiB blocks.
  • .max1MB: 1 MiB blocks.
  • .max4MB: 4 MiB blocks (higher compression on large files).

blockMode

• Type: BlockMode
• Default: .independent
• Options:
  • .independent: Each block can be parsed without state from previous blocks.
  • .linked: Blocks reference the sliding 64 KiB window of the preceding block.

contentChecksum

• Type: bool
• Default: true
• Description: Computes a 32-bit xxHash-32 checksum of the entire uncompressed stream and writes it immediately following the END_MARK.

blockChecksum

• Type: bool
• Default: false
• Description: Appends a 32-bit xxHash-32 checksum directly after each compressed block payload.

contentSize

• Type: ?u64
• Default: null (auto-populated with src.len in one-shot operations)
• Description: 8-byte original uncompressed size recorded in the frame header for verification and fast decoder pre-allocation.

dictId

• Type: ?u32
• Default: null
• Description: Optional 4-byte dictionary identifier stored in the frame descriptor.

customDictionary

• Type: ?[]const u8
• Default: null
• Description: In-memory dictionary buffer used to initialize match history.

favorDecSpeed

• Type: bool
• Default: false
• Description: Directs the HC parser to prefer match structures that maximize decompression throughput.

autoFlush

• Type: bool
• Default: true
• Description: In streaming mode, flushes blocks immediately without waiting for a full blockMaxSize buffer.