pressed block
           or 0 if there is an error (typically, cannot fit into 'dst').

  Note 1 : Each invocation to LZ4_compress_fast_continue() generates a new block.
           Each block has precise boundaries.
           It's not possible to append blocks together and expect a single invocation of LZ4_decompress_*() to decompress them together.
           Each block must be decompressed separately, calling LZ4_decompress_*() with associated metadata.

  Note 2 : The previous 64KB of source data is __a