LZ4 binding for Lua

LZ4 is a very fast compression and decompression algorithm. This Lua binding is in conformance with the LZ4 block and frame specifications and also support streaming.

Example usage

Simple frame compression/decompression

local lz4 = require("lz4")
local s = "LZ4 is a very fast compression and decompression algorithm."
assert(lz4.decompress(lz4.compress(s)) == s)

Build/Install Instructions

With luarocks:

luarocks install lua-lz4

With make:

export LUA_INCDIR=/path/to/lua_header
export LUA_LIBDIR=/path/to/liblua
make

Documentations

Frame

Easy to use and compressed data contain meta data such as checksum, decompress size, etc. The compressed/decompressed data in frame format can be exchange with other programs.

lz4.compress(input[, options])

Compress input and return compressed data.

• input: input string to be compressed.
• options: optional table that can be contains
  • compression_level: integer between 0 to 16
  • auto_flush: boolean
  • block_size: maximum block size can be lz4.block_64KB, lz4.block_256KB., lz4.block_1MB, lz4.block_4MB
  • block_independent: boolean
  • content_checksum: boolean

lz4.decompress(input)

Decompress input and return decompressed data.

• input: input string to be decompressed.

Block

Basic compression/decompression in plain block format. Require decompress_length to decompress data.

Example:

local lz4 = require("lz4")
local s = "LZ4 is a very fast compression and decompression algorithm."
assert(lz4.block_decompress_safe(lz4.block_compress(s), #s) == s)

lz4.block_compress(input[, accelerate])

Compress input and return compressed data.

• input: input string to be compressed.
• accelerate: optional integer

lz4.block_compress_hc(input[, compression_level])

Compress input in high compression mode and return compressed data.

• input: input string to be compressed.
• compression_level: optional integer

lz4.block_decompress_safe(input, decompress_length)

Decompress input and return decompressed data. This function is protected against buffer overflow exploits, including malicious data packets.

• input: input string to be decompressed.
• decompress_length: length of decompressed data (integer)

lz4.block_decompress_fast(input, decompress_length)

Decompress input and return decompressed data. It does not provide any protection against intentionally modified data stream (malicious input). Use this function in trusted environment only (data to decode comes from a trusted source).

• input: input string to be decompressed.
• decompress_length: length of decompressed data (integer)

Stream

Use streaming to compress/decompress multiple blocks. The compressing blocks can be use content in previous blocks therefore more compression ratio. Decoding buffer should be either to get good performance.

• Exactly same size as encoding buffer, with same update rule (block boundaries at same positions) In which case, the decoding & encoding ring buffer can have any size, including very small ones ( < 64 KB).
• Larger than encoding buffer, by a minimum of maxBlockSize more bytes. maxBlockSize is implementation dependent. It's the maximum size you intend to compress into a single block. In which case, encoding and decoding buffers do not need to be synchronized, and encoding ring buffer can have any size, including small ones ( < 64 KB).
• At least 64 KB + 8 bytes + maxBlockSize. In which case, encoding and decoding buffers do not need to be synchronized, and encoding ring buffer can have any size, including larger than decoding buffer.

Example:

local lz4 = require("lz4")
local s1 = "LZ4 is a very fast compression and decompression algorithm."
local s2 = "lua-lz4 - LZ4 binding for Lua"
local com = lz4.new_compression_stream()
local dec = lz4.new_decompression_stream()
assert(dec:decompress_safe(com:compress(s1), #s1) == s1)
assert(dec:decompress_safe(com:compress(s2), #s2) == s2)

lz4.new_compression_stream([ring_buffer_size[, accelerate]])

New a lz4.compression_stream object.

• ring_buffer_size: integer
• accelerate: integer

lz4.compression_stream methods

• reset([dictionary]) forget internal dictionary or reset to new dictionary
• compress(input)

lz4.new_compression_stream_hc([ring_buffer_size[, compression_level]])

New a lz4.compression_stream_hc object.

• ring_buffer_size: integer
• compression_level: integer

lz4.compression_stream_hc methods

• reset([dictionary]) forget internal dictionary or reset to new dictionary
• compress(input)

lz4.new_decompression_stream([ring_buffer_size])

New a lz4.decompression_stream object.

• ring_buffer_size: integer

lz4.decompression_stream methods

• reset([dictionary]) forget internal dictionary or reset to new dictionary
• decompress_safe(input, decompress_length)
• decompress_fast(input, decompress_length)