X-Git-Url: https://wimlib.net/git/?p=wimlib;a=blobdiff_plain;f=src%2Flzx_compress.c;h=c682e7e9a1f26562f9c7fe63249f08d8f7217112;hp=33943af7fa41d1e4d4cb3f4a66bdbc4acd27e93e;hb=558155a9524277661e15a030648c62b32be1cdb6;hpb=7ea97f5338e7fd6b19dbb7df4e8e333d286d8ac2

diff --git a/src/lzx_compress.c b/src/lzx_compress.c
index 33943af7..c682e7e9 100644
--- a/src/lzx_compress.c
+++ b/src/lzx_compress.c
@@ -410,8 +410,10 @@ struct lzx_compressor {
 
 	/* The matches and literals that the parser has chosen for the current
 	 * block.  The required length of this array is limited by the maximum
-	 * number of matches that can ever be chosen for a single block.  */
-	struct lzx_sequence chosen_sequences[DIV_ROUND_UP(LZX_DIV_BLOCK_SIZE, LZX_MIN_MATCH_LEN)];
+	 * number of matches that can ever be chosen for a single block, plus
+	 * one for the special entry at the end.  */
+	struct lzx_sequence chosen_sequences[
+		       DIV_ROUND_UP(LZX_DIV_BLOCK_SIZE, LZX_MIN_MATCH_LEN) + 1];
 
 	/* Tables for mapping adjusted offsets to offset slots  */
 
@@ -548,7 +550,7 @@ struct lzx_output_bitstream {
 
 /* Can the specified number of bits always be added to 'bitbuf' after any
  * pending 16-bit coding units have been flushed?  */
-#define CAN_BUFFER(n)	((n) <= (8 * sizeof(machine_word_t)) - 16)
+#define CAN_BUFFER(n)	((n) <= (8 * sizeof(machine_word_t)) - 15)
 
 /*
  * Initialize the output bitstream.
@@ -585,13 +587,21 @@ lzx_add_bits(struct lzx_output_bitstream *os, u32 bits, unsigned num_bits)
 static inline void
 lzx_flush_bits(struct lzx_output_bitstream *os, unsigned max_num_bits)
 {
+	/* Masking the number of bits to shift is only needed to avoid undefined
+	 * behavior; we don't actually care about the results of bad shifts.  On
+	 * x86, the explicit masking generates no extra code.  */
+	const u32 shift_mask = 8 * sizeof(os->bitbuf) - 1;
+
 	if (os->end - os->next < 6)
 		return;
-	put_unaligned_u16_le(os->bitbuf >> (os->bitcount - 16), os->next + 0);
+	put_unaligned_u16_le(os->bitbuf >> ((os->bitcount - 16) &
+					    shift_mask), os->next + 0);
 	if (max_num_bits > 16)
-		put_unaligned_u16_le(os->bitbuf >> (os->bitcount - 32), os->next + 2);
+		put_unaligned_u16_le(os->bitbuf >> ((os->bitcount - 32) &
+						shift_mask), os->next + 2);
 	if (max_num_bits > 32)
-		put_unaligned_u16_le(os->bitbuf >> (os->bitcount - 48), os->next + 4);
+		put_unaligned_u16_le(os->bitbuf >> ((os->bitcount - 48) &
+						shift_mask), os->next + 4);
 	os->next += (os->bitcount >> 4) << 1;
 	os->bitcount &= 15;
 }
@@ -634,7 +644,7 @@ lzx_make_huffman_codes(struct lzx_compressor *c)
 
 	STATIC_ASSERT(MAIN_CODEWORD_LIMIT >= 9 &&
 		      MAIN_CODEWORD_LIMIT <= LZX_MAX_MAIN_CODEWORD_LEN);
-	STATIC_ASSERT(LENGTH_CODEWORD_LIMIT >= 9 &&
+	STATIC_ASSERT(LENGTH_CODEWORD_LIMIT >= 8 &&
 		      LENGTH_CODEWORD_LIMIT <= LZX_MAX_LEN_CODEWORD_LEN);
 	STATIC_ASSERT(ALIGNED_CODEWORD_LIMIT >= LZX_NUM_ALIGNED_OFFSET_BITS &&
 		      ALIGNED_CODEWORD_LIMIT <= LZX_MAX_ALIGNED_CODEWORD_LEN);
@@ -994,6 +1004,8 @@ lzx_write_sequences(struct lzx_output_bitstream *os, int block_type,
 			if (!CAN_BUFFER(MAX_MATCH_BITS))
 				lzx_flush_bits(os, ALIGNED_CODEWORD_LIMIT);
 		} else {
+			STATIC_ASSERT(CAN_BUFFER(17));
+
 			lzx_add_bits(os, extra_bits, num_extra_bits);
 			if (!CAN_BUFFER(MAX_MATCH_BITS))
 				lzx_flush_bits(os, 17);
@@ -1809,7 +1821,7 @@ lzx_compress_near_optimal(struct lzx_compressor *c,
 			if (unlikely(max_len > in_end - in_next)) {
 				max_len = in_end - in_next;
 				nice_len = min(max_len, nice_len);
-				if (unlikely(max_len < 5)) {
+				if (unlikely(max_len < BT_MATCHFINDER_REQUIRED_NBYTES)) {
 					in_next++;
 					cache_ptr->length = 0;
 					cache_ptr++;
@@ -1849,7 +1861,7 @@ lzx_compress_near_optimal(struct lzx_compressor *c,
 					if (unlikely(max_len > in_end - in_next)) {
 						max_len = in_end - in_next;
 						nice_len = min(max_len, nice_len);
-						if (unlikely(max_len < 5)) {
+						if (unlikely(max_len < BT_MATCHFINDER_REQUIRED_NBYTES)) {
 							in_next++;
 							cache_ptr->length = 0;
 							cache_ptr++;