Add comment regarding long match distance bit costs.

diff --git a/deflate_medium.c b/deflate_medium.c
index 8283a08a042ed5a704070bce0a4fc2d370a60423..07ce71fe3376c15547547b9e623f0e3371383e93 100644 (file)
--- a/deflate_medium.c
+++ b/deflate_medium.c
@@ -292,6 +292,7 @@ ZLIB_INTERNAL block_state deflate_medium(deflate_state *s, int flush) {
             }
 
             /* short matches with a very long distance are rarely a good idea encoding wise */
+            /* distances 8193–16384 take 12 extra bits, distances 16385–32768 take 13 extra bits */
             if (next_match.match_length == 3 && (next_match.strstart - next_match.match_start) > 12000)
                     next_match.match_length = 1;
             s->strstart = current_match.strstart;