diff options
| -rw-r--r-- | lib/uzlib/lz77.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/lib/uzlib/lz77.c b/lib/uzlib/lz77.c index 117ce50f7..8d6920665 100644 --- a/lib/uzlib/lz77.c +++ b/lib/uzlib/lz77.c @@ -28,13 +28,13 @@ void uzlib_lz77_init(uzlib_lz77_state_t *state, uint8_t *hist, size_t hist_max) state->hist_len = 0; } -// Push the given byte to the history. // Search back in the history for the maximum match of the given src data, // with support for searching beyond the end of the history and into the src buffer // (effectively the history and src buffer are concatenated). static size_t uzlib_lz77_search_max_match(uzlib_lz77_state_t *state, const uint8_t *src, size_t len, size_t *longest_offset) { size_t longest_len = 0; for (size_t hist_search = 0; hist_search < state->hist_len; ++hist_search) { + // Search for a match. size_t match_len; for (match_len = 0; match_len <= MATCH_LEN_MAX && match_len < len; ++match_len) { uint8_t hist; @@ -47,7 +47,11 @@ static size_t uzlib_lz77_search_max_match(uzlib_lz77_state_t *state, const uint8 break; } } - if (match_len >= MATCH_LEN_MIN && match_len > longest_len) { + + // Take this match if its length is at least the minimum, and larger than previous matches. + // If the length is the same as the previous longest then take this match as well, because + // this match will be closer (more recent in the history) and take less bits to encode. + if (match_len >= MATCH_LEN_MIN && match_len >= longest_len) { longest_len = match_len; *longest_offset = state->hist_len - hist_search; } |