igzip: Fix bug in default histogram generation

Change-Id: Ib1976633c2fbf6f48aeb4b38e73fd75d41c62be5 Signed-off-by: Roy Oursler <[email protected]>
ibmsoe · Dec 6, 2016 · d4c6067 · d4c6067
1 parent e569ff7
commit d4c6067
Showing 1 changed file with 8 additions and 5 deletions.
diff --git a/igzip/huff_codes.c b/igzip/huff_codes.c
@@ -178,9 +178,10 @@ void isal_update_histogram_base(uint8_t * start_stream, int length,
 		literal = *(uint32_t *) current;
 		hash = compute_hash(literal) & HASH_MASK;
 		seen = last_seen[hash];
-		last_seen[hash] = (uint64_t) current & 0xFFFF;
-		dist = ((uint64_t) current - seen) & 0xFFFF;
+		last_seen[hash] = ((uint64_t) current - (uint64_t) start_stream) & 0xFFFF;
+		dist = ((uint64_t) current - (uint64_t) start_stream - seen) & 0xFFFF;
 		if (dist - 1 < D - 1) {
+			assert(start_stream <= current - dist);
 			match_length =
 			    compare258(current - dist, current, end_stream - current);
 			if (match_length >= SHORTEST_MATCH) {
@@ -196,7 +197,9 @@ void isal_update_histogram_base(uint8_t * start_stream, int length,
 				for (; next_hash < end; next_hash++) {
 					literal = *(uint32_t *) next_hash;
 					hash = compute_hash(literal) & HASH_MASK;
-					last_seen[hash] = (uint64_t) next_hash & 0xFFFF;
+					last_seen[hash] =
+					    ((uint64_t) next_hash -
+					     (uint64_t) start_stream) & 0xFFFF;
 				}
 
 				dist_histogram[convert_dist_to_dist_sym(dist)] += 1;
@@ -211,8 +214,8 @@ void isal_update_histogram_base(uint8_t * start_stream, int length,
 	literal = literal >> 8;
 	hash = compute_hash(literal) & HASH_MASK;
 	seen = last_seen[hash];
-	last_seen[hash] = (uint64_t) current & 0xFFFF;
-	dist = ((uint64_t) current - seen) & 0xFFFF;
+	last_seen[hash] = ((uint64_t) current - (uint64_t) start_stream) & 0xFFFF;
+	dist = ((uint64_t) current - (uint64_t) start_stream - seen) & 0xFFFF;
 	if (dist < D) {
 		match_length = compare258(current - dist, current, end_stream - current);
 		if (match_length >= SHORTEST_MATCH) {