Initializing and releasing the LZX compressor

The lzx_init() function takes a wsize_code to indicate the log (base 2) of the window size for compression, so 15 is 32K, 16 is 64K, on up to 21 meaning 2MB. It also takes the following callback functions and their associated arguments:

The lzx_init() function allocates an opaque structure, a pointer to which will be returned in lzxdp. A pointer to this structure may be passed to the other LZX compression functions. The function returns negative on error, 0 otherwise

The lzx_finish() function writes out any unflushed data, releases all memory held by the compressor (including the lzxd structure) and optionally fills in the lzx_results structure, a pointer to which is passed in as lzxr (NULL if results are not required)

Running the compressor

The lzx_compress_block() function takes the opaque pointer returned by lzx_init(), a block_size, and a flag which says whether or not to subdivide the block. If the subdivide flag is set, blocks may be subdivided to increase compression ratio based on the entropy of the data at a given point. Otherwise, just one block is created. Returns negative on error, 0 otherwise.

Note:

The block size must not be larger than the window size. While the compressor will create apparently-valid LZX files if this restriction is violated, some decompressors will not handle them.

The lzx_reset() function may be called after any block in order to reset all compression state except the number of compressed and uncompressed bytes processed. This forces the one-bit Intel preprocessing header to be output again, the Lempel-Ziv window to be cleared, and the Huffman tables to be reset to zero length. It should only be called on a frame boundary; the results of calling it elsewhere or during a callback are undefined.

To compress data, simply call lzx_compress_block() and optionally lzx_reset() repeatedly, handling the various callbacks described above, until your data is exhausted.