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Use a full table for base64 decode.

Browse Source 
Also encodes error or end marker into table.
About 20% faster.
decode:       466491 -> 374139 decicycles
syntax check: 236955 -> 161182 decicycles

Signed-off-by: Reimar Döffinger <Reimar.Doeffinger@gmx.de>
This commit is contained in:
Reimar Döffinger 2012-01-21 12:22:19 +01:00
parent d41c824b23
commit 523f676b51
1 changed files with 35 additions and 8 deletions
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43
libavutil/base64.c
View File

@ -30,32 +30,59 @@
#include "intreadwrite.h"
/* ---------------- private code */
static const uint8_t map2[] =
static const uint8_t map2[256] =
{
0xfe, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff,
0x3e, 0xff, 0xff, 0xff, 0x3f, 0x34, 0x35, 0x36,
0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x01,
0xff, 0xff, 0xfe, 0xff, 0xff, 0xff, 0x00, 0x01,
0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,
0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11,
0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x1a, 0x1b,
0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23,
0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,
0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33
0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33,
0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
};
int av_base64_decode(uint8_t *out, const char *in, int out_size)
int av_base64_decode(uint8_t *out, const char *in_str, int out_size)
{
int i, v;
uint8_t *dst = out;
uint8_t *end = out + out_size;
// no sign extension
const uint8_t *in = in_str;
v = 0;
for (i = 0; ; i++) {
unsigned int index= in[i]-43;
if (index>=FF_ARRAY_ELEMS(map2) || map2[index] == 0xff)
return in[i] && in[i] != '=' ? -1 : dst - out;
v = (v << 6) + map2[index];
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));