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authorNicolas Pitre <nico@cam.org>2006-05-08 11:31:11 -0400
committerJunio C Hamano <junkio@cox.net>2006-05-08 11:05:01 -0700
commitaddaacab07d91e5ff1f06ada31c9e96c0edd31cd (patch)
tree5e7bd56a743fb95944b1513ca3b08be35c3fc23e /base85.c
parent42d0ee8302c361a0e3bde7bc59858eda94bc13a4 (diff)
downloadgit-addaacab07d91e5ff1f06ada31c9e96c0edd31cd.tar.gz
improve base85 generated assembly code
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>
Diffstat (limited to 'base85.c')
-rw-r--r--base85.c64
1 files changed, 35 insertions, 29 deletions
diff --git a/base85.c b/base85.c
index b97f7f933a..a9e97f89d9 100644
--- a/base85.c
+++ b/base85.c
@@ -44,34 +44,38 @@ int decode_85(char *dst, char *buffer, int len)
say2("decode 85 <%.*s>", len/4*5, buffer);
while (len) {
unsigned acc = 0;
- int cnt;
- for (cnt = 0; cnt < 5; cnt++, buffer++) {
- int ch = *((unsigned char *)buffer);
- int de = de85[ch];
- if (!de)
+ int de, cnt = 4;
+ unsigned char ch;
+ do {
+ ch = *buffer++;
+ de = de85[ch];
+ if (--de < 0)
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;
- 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);
- for (cnt = 0; cnt < 4 && len; cnt++, len--) {
- *dst++ = (acc >> 24) & 0xff;
- acc = acc << 8;
- }
+
+ cnt = (len < 4) ? len : 4;
+ len -= cnt;
+ do {
+ acc = (acc << 8) | (acc >> 24);
+ *dst++ = acc;
+ } while (--cnt);
}
say("\n");
@@ -86,15 +90,17 @@ void encode_85(char *buf, unsigned char *data, int bytes)
while (bytes) {
unsigned acc = 0;
int cnt;
- for (cnt = 0; cnt < 4 && bytes; cnt++, bytes--) {
+ for (cnt = 24; cnt >= 0; cnt -= 8) {
int ch = *data++;
- acc |= ch << ((3-cnt)*8);
+ acc |= ch << cnt;
+ if (--bytes == 0)
+ break;
}
say1(" %08x", acc);
- for (cnt = 0; cnt < 5; cnt++) {
+ for (cnt = 4; cnt >= 0; cnt--) {
int val = acc % 85;
acc /= 85;
- buf[4-cnt] = en85[val];
+ buf[cnt] = en85[val];
}
buf += 5;
}