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improve base85 generated assembly code

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This code is arguably pretty hot, if you use binary patches of course.
This patch helps gcc generate both smaller and faster code especially in
the error free path.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Nicolas Pitre 2006-05-08 11:31:11 -04:00 committed by Junio C Hamano
parent 42d0ee8302
commit addaacab07
1 changed files with 35 additions and 29 deletions
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64
base85.c
View File

@ -44,34 +44,38 @@ int decode_85(char *dst, char *buffer, int len)
say2("decode 85 <%.*s>", len/4*5, buffer); say2("decode 85 <%.*s>", len/4*5, buffer);
while (len) { while (len) {
unsigned acc = 0; unsigned acc = 0;
int cnt; int de, cnt = 4;
for (cnt = 0; cnt < 5; cnt++, buffer++) { unsigned char ch;
int ch = *((unsigned char *)buffer); do {
int de = de85[ch]; ch = *buffer++;
if (!de) de = de85[ch];
if (--de < 0)
return error("invalid base85 alphabet %c", ch); return error("invalid base85 alphabet %c", ch);
de--;
if (cnt == 4) {
/*
* Detect overflow. The largest
* 5-letter possible is "|NsC0" to
* encode 0xffffffff, and "|NsC" gives
* 0x03030303 at this point (i.e.
* 0xffffffff = 0x03030303 * 85).
*/
if (0x03030303 < acc ||
(0x03030303 == acc && de))
error("invalid base85 sequence %.5s",
buffer-3);
}
acc = acc * 85 + de; acc = acc * 85 + de;
say1(" <%08x>", acc); } while (--cnt);
} ch = *buffer++;
de = de85[ch];
if (--de < 0)
return error("invalid base85 alphabet %c", ch);
/*
* Detect overflow. The largest
* 5-letter possible is "|NsC0" to
* encode 0xffffffff, and "|NsC" gives
* 0x03030303 at this point (i.e.
* 0xffffffff = 0x03030303 * 85).
*/
if (0x03030303 < acc ||
0xffffffff - de < (acc *= 85))
error("invalid base85 sequence %.5s", buffer-5);
acc += de;
say1(" %08x", acc); say1(" %08x", acc);
for (cnt = 0; cnt < 4 && len; cnt++, len--) {
*dst++ = (acc >> 24) & 0xff; cnt = (len < 4) ? len : 4;
acc = acc << 8; len -= cnt;
} do {
acc = (acc << 8) | (acc >> 24);
*dst++ = acc;
} while (--cnt);
} }
say("\n"); say("\n");
@ -86,15 +90,17 @@ void encode_85(char *buf, unsigned char *data, int bytes)
while (bytes) { while (bytes) {
unsigned acc = 0; unsigned acc = 0;
int cnt; int cnt;
for (cnt = 0; cnt < 4 && bytes; cnt++, bytes--) { for (cnt = 24; cnt >= 0; cnt -= 8) {
int ch = *data++; int ch = *data++;
acc |= ch << ((3-cnt)*8); acc |= ch << cnt;
if (--bytes == 0)
break;
} }
say1(" %08x", acc); say1(" %08x", acc);
for (cnt = 0; cnt < 5; cnt++) { for (cnt = 4; cnt >= 0; cnt--) {
int val = acc % 85; int val = acc % 85;
acc /= 85; acc /= 85;
buf[4-cnt] = en85[val]; buf[cnt] = en85[val];
} }
buf += 5; buf += 5;
} }