From ea536bcce2a20f39cd0e9d0243c451c03e01ac8e Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Tue, 4 Jan 2022 21:25:56 -0800
Subject: [PATCH] bt_matchfinder: remove best_len_ret parameter

It doesn't seem worthwhile to have bt_matchfinder_get_matches() return
the best_len separately anymore, especially since it doesn't work as
expected due to it not handling length 3 matches.
---
 lib/bt_matchfinder.h   | 14 --------------
 lib/deflate_compress.c |  3 ++-
 2 files changed, 2 insertions(+), 15 deletions(-)

diff --git a/lib/bt_matchfinder.h b/lib/bt_matchfinder.h
index cc21f8b..8817141 100644
--- a/lib/bt_matchfinder.h
+++ b/lib/bt_matchfinder.h
@@ -146,7 +146,6 @@ bt_matchfinder_advance_one_byte(struct bt_matchfinder * const restrict mf,
 				const u32 nice_len,
 				const u32 max_search_depth,
 				u32 * const restrict next_hashes,
-				u32 * const restrict best_len_ret,
 				struct lz_match * restrict lz_matchptr,
 				const bool record_matches)
 {
@@ -212,7 +211,6 @@ bt_matchfinder_advance_one_byte(struct bt_matchfinder * const restrict mf,
 	if (cur_node <= cutoff) {
 		*pending_lt_ptr = MATCHFINDER_INITVAL;
 		*pending_gt_ptr = MATCHFINDER_INITVAL;
-		*best_len_ret = best_len;
 		return lz_matchptr;
 	}
 
@@ -235,7 +233,6 @@ bt_matchfinder_advance_one_byte(struct bt_matchfinder * const restrict mf,
 				if (len >= nice_len) {
 					*pending_lt_ptr = *bt_left_child(mf, cur_node);
 					*pending_gt_ptr = *bt_right_child(mf, cur_node);
-					*best_len_ret = best_len;
 					return lz_matchptr;
 				}
 			}
@@ -260,7 +257,6 @@ bt_matchfinder_advance_one_byte(struct bt_matchfinder * const restrict mf,
 		if (cur_node <= cutoff || !--depth_remaining) {
 			*pending_lt_ptr = MATCHFINDER_INITVAL;
 			*pending_gt_ptr = MATCHFINDER_INITVAL;
-			*best_len_ret = best_len;
 			return lz_matchptr;
 		}
 	}
@@ -289,12 +285,6 @@ bt_matchfinder_advance_one_byte(struct bt_matchfinder * const restrict mf,
  *	The precomputed hash codes for the sequence beginning at @in_next.
  *	These will be used and then updated with the precomputed hashcodes for
  *	the sequence beginning at @in_next + 1.
- * @best_len_ret
- *	If a match of length >= 4 was found, then the length of the longest such
- *	match is written here; otherwise 3 is written here.  (Note: this is
- *	redundant with the 'struct lz_match' array, but this is easier for the
- *	compiler to optimize when inlined and the caller immediately does a
- *	check against 'best_len'.)
  * @lz_matchptr
  *	An array in which this function will record the matches.  The recorded
  *	matches will be sorted by strictly increasing length and (non-strictly)
@@ -312,7 +302,6 @@ bt_matchfinder_get_matches(struct bt_matchfinder *mf,
 			   u32 nice_len,
 			   u32 max_search_depth,
 			   u32 next_hashes[2],
-			   u32 *best_len_ret,
 			   struct lz_match *lz_matchptr)
 {
 	return bt_matchfinder_advance_one_byte(mf,
@@ -322,7 +311,6 @@ bt_matchfinder_get_matches(struct bt_matchfinder *mf,
 					       nice_len,
 					       max_search_depth,
 					       next_hashes,
-					       best_len_ret,
 					       lz_matchptr,
 					       true);
 }
@@ -341,7 +329,6 @@ bt_matchfinder_skip_byte(struct bt_matchfinder *mf,
 			 u32 max_search_depth,
 			 u32 next_hashes[2])
 {
-	u32 best_len;
 	bt_matchfinder_advance_one_byte(mf,
 					in_base,
 					cur_pos,
@@ -349,7 +336,6 @@ bt_matchfinder_skip_byte(struct bt_matchfinder *mf,
 					nice_len,
 					max_search_depth,
 					next_hashes,
-					&best_len,
 					NULL,
 					false);
 }
diff --git a/lib/deflate_compress.c b/lib/deflate_compress.c
index d225139..df08ac9 100644
--- a/lib/deflate_compress.c
+++ b/lib/deflate_compress.c
@@ -3415,8 +3415,9 @@ deflate_compress_near_optimal(struct libdeflate_compressor * restrict c,
 						nice_len,
 						c->max_search_depth,
 						next_hashes,
-						&best_len,
 						matches);
+				if (cache_ptr > matches)
+					best_len = cache_ptr[-1].length;
 			}
 			c->freqs.litlen[*in_next]++;
 			if (in_next >= next_observation) {