LZ4 library decompressed data upper bound size estimation

Question

I\'m using LZ4 library and when decompressing data with

int LZ4_decompress_safe (const char* source, char* dest, int compressedSize, int maxDecompressedSize)         


        

Answer 1

Just for reference, n bytes of LZ4 compressed data can represent up to 24 + 255(n - 10) uncompressed bytes, which is the case of a run of that many bytes. n must be at least ten to make a valid stream that includes a literal, a match, and then five literals at the end per the specification. So the decompress bound function could be something like (n << 8) - n - 2526.

The maximum compression ratio is then: 255 - 2526 / n, which asymptotically approaches 255 for arbitrarily large n.