aboutsummaryrefslogtreecommitdiff
path: root/archival/gzip.c
diff options
context:
space:
mode:
authorGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-01-31 00:01:06 +0100
committerGravatar Denys Vlasenko <vda.linux@googlemail.com>2018-01-31 00:01:06 +0100
commitb7dfbbcdaaae5267259e2272b1cdfde6daad44a0 (patch)
treeb5b5eb2808e08e4730c944e3407fb3100cae4f82 /archival/gzip.c
parentd7500f856d856716fd228935bb5e84c897c9daa8 (diff)
downloadbusybox-b7dfbbcdaaae5267259e2272b1cdfde6daad44a0.tar.gz
busybox-b7dfbbcdaaae5267259e2272b1cdfde6daad44a0.tar.bz2
gzip: speed up send_bits()
Replace one RMW op with store. This speeds up gzip of a png file by ~2%. function old new delta send_bits 62 66 +4 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'archival/gzip.c')
-rw-r--r--archival/gzip.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/archival/gzip.c b/archival/gzip.c
index f253a217a..08633d667 100644
--- a/archival/gzip.c
+++ b/archival/gzip.c
@@ -523,7 +523,6 @@ static unsigned file_read(void *buf, unsigned size)
static void send_bits(unsigned value, unsigned length)
{
unsigned new_buf;
- unsigned remain;
#ifdef DEBUG
Tracev((stderr, " l %2d v %4x ", length, value));
@@ -534,25 +533,26 @@ static void send_bits(unsigned value, unsigned length)
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 check below is changed to "length > BUF_SIZE" instead of >= */
+ length += G1.bi_valid;
/* If bi_buf is full */
- if (length >= remain) {
+ if (length >= BUF_SIZE) {
/* ...use (valid) bits from bi_buf and
* (BUF_SIZE - bi_valid) bits from value,
* leaving (width - (BUF_SIZE-bi_valid)) unused bits in value.
*/
+ value >>= (BUF_SIZE - G1.bi_valid);
if (BUF_SIZE == 32) {
put_32bit(new_buf); /* maybe unroll to 2*put_16bit()? */
} else { /* 16 */
put_16bit(new_buf);
}
- new_buf = value >> remain;
+ new_buf = value;
length -= BUF_SIZE;
}
G1.bi_buf = new_buf;
- G1.bi_valid += length;
+ G1.bi_valid = length;
}