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Unroll base64 decode loop.

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Around 50% faster.
decode:       374139 -> 248852 decicycles
syntax check: 236955 -> 123854 decicycles

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
This commit is contained in:
Reimar Döffinger 2012-01-21 12:43:42 +01:00
parent 523f676b51
commit def19c9036
1 changed files with 36 additions and 13 deletions
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49
libavutil/base64.c
View File

@ -26,7 +26,6 @@
#include "common.h"
#include "base64.h"
#include "avassert.h"
#include "intreadwrite.h"
/* ---------------- private code */
@ -69,29 +68,53 @@ static const uint8_t map2[256] =
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
};
#define BASE64_DEC_STEP(i) \
bits = map2[in[i]]; \
if (bits & 0x80) \
goto out; \
v = (v << 6) + bits; \
if (i & 3) \
*dst++ = v >> (6 - 2 * (i & 3)); \
int av_base64_decode(uint8_t *out, const char *in_str, int out_size)
{
int i, v;
int v;
uint8_t *dst = out;
uint8_t *end = out + out_size;
// no sign extension
const uint8_t *in = in_str;
unsigned bits = 0xff;
v = 0;
for (i = 0; ; i++) {
unsigned bits = map2[in[i]];
if (bits & 0x80)
return bits & 1 ? -1 : dst - out;
v = (v << 6) + bits;
if (i & 3) {
if (dst < end) {
*dst++ = v >> (6 - 2 * (i & 3));
}
while (end - dst > 2) {
BASE64_DEC_STEP(0)
BASE64_DEC_STEP(1)
BASE64_DEC_STEP(2)
BASE64_DEC_STEP(3)
in += 4;
}
if (end - dst) {
BASE64_DEC_STEP(0)
BASE64_DEC_STEP(1)
if (end - dst) {
BASE64_DEC_STEP(2)
in++;
}
in += 2;
}
while (1) {
BASE64_DEC_STEP(0)
in++;
BASE64_DEC_STEP(0)
in++;
BASE64_DEC_STEP(0)
in++;
BASE64_DEC_STEP(0)
in++;
}
av_assert1(0);
return 0;
out:
return bits & 1 ? -1 : dst - out;
}
/*****************************************************************************