Function om_encoder_compress_chunk 

pub unsafe extern "C" fn om_encoder_compress_chunk(
    encoder: *const OmEncoder_t,
    array: *const c_void,
    arrayDimensions: *const u64,
    arrayOffset: *const u64,
    arrayCount: *const u64,
    chunkIndex: u64,
    chunkIndexOffsetInThisArray: u64,
    out: *mut u8,
    chunkBuffer: *mut u8,
) -> u64

Compress a single chunk. Chunk buffer must be of size OmEncoder_chunkBufferSize