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authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-01-30 23:47:45 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-01-30 23:47:45 +0100
commit6ba6a6f28e456c0148abece678eab1c1194632f2 (patch)
tree8451e69dfeea79cdc9bbc481ecf54ca3fff198c1 /archival/gzip.c
parente4c4e6ddc365d8e9b5409e2f929116624c932c1d (diff)
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gzip: use wider (32-bit, not 16) bi_buf
function old new delta bi_windup 76 74 -2 send_bits 70 62 -8 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'archival/gzip.c')
-rw-r--r--archival/gzip.c33
1 files changed, 22 insertions, 11 deletions
diff --git a/archival/gzip.c b/archival/gzip.c
index efc5a0eea..4a3fe976a 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -355,7 +355,7 @@ struct globals {
/* Output buffer. bits are inserted starting at the bottom (least significant
* bits).
*/
- unsigned short bi_buf;
+ unsigned bi_buf; /* was unsigned short */
#undef BUF_SIZE
#define BUF_SIZE (int)(8 * sizeof(G1.bi_buf))
@@ -530,17 +530,25 @@ static void send_bits(int value, int length)
Assert(length > 0 && length <= 15, "invalid length");
G1.bits_sent += length;
#endif
+ BUILD_BUG_ON(BUF_SIZE != 32 && BUF_SIZE != 16);
new_buf = G1.bi_buf | (value << G1.bi_valid);
+ /* NB: the above may sometimes do "<< 32" shift (undefined)
+ * if check below is changed to "length > remain" instead of >= */
remain = BUF_SIZE - G1.bi_valid;
- /* If not enough room in bi_buf */
- if (length > remain) {
+
+ /* If bi_buf is full */
+ if (length >= remain) {
/* ...use (valid) bits from bi_buf and
- * (16 - bi_valid) bits from value,
- * leaving (width - (16-bi_valid)) unused bits in value.
+ * (BUF_SIZE - bi_valid) bits from value,
+ * leaving (width - (BUF_SIZE-bi_valid)) unused bits in value.
*/
- put_16bit(new_buf);
- new_buf = (ush) value >> remain;
+ if (BUF_SIZE == 32) {
+ put_32bit(new_buf); /* maybe unroll to 2*put_16bit()? */
+ } else { /* 16 */
+ put_16bit(new_buf);
+ }
+ new_buf = (unsigned) value >> remain;
length -= BUF_SIZE;
}
G1.bi_buf = new_buf;
@@ -571,10 +579,13 @@ static unsigned bi_reverse(unsigned code, int len)
*/
static void bi_windup(void)
{
- if (G1.bi_valid > 8) {
- put_16bit(G1.bi_buf);
- } else if (G1.bi_valid > 0) {
- put_8bit(G1.bi_buf);
+ unsigned bits = G1.bi_buf;
+ int cnt = G1.bi_valid;
+
+ while (cnt > 0) {
+ put_8bit(bits);
+ bits >>= 8;
+ cnt -= 8;
}
G1.bi_buf = 0;
G1.bi_valid = 0;