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@xxxxxxx>
---
diff --git a/base85.c b/base85.c
index b97f7f9..a9e97f8 100644
--- a/base85.c
+++ b/base85.c
@@ -44,34 +44,38 @@ int decode_85(char *dst, char *buffer, i
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
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;
}
-
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