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LZO optimization: check input buffer bounds less frequently if padded

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Originally committed as revision 7747 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Reimar Döffinger 2007-01-28 16:49:51 +00:00
parent 910c62e1fc
commit a737f1dfdb
2 changed files with 23 additions and 13 deletions
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34
libavcodec/lzo.c
View File

@ -26,7 +26,7 @@
//! define if we may write up to 12 bytes beyond the output buffer
#define OUTBUF_PADDED 1
//! define if we may read up to 4 bytes beyond the input buffer
//! define if we may read up to 8 bytes beyond the input buffer
#define INBUF_PADDED 1
typedef struct LZOContext {
uint8_t *in, *in_end;
@ -45,6 +45,12 @@ static inline int get_byte(LZOContext *c) {
return 1;
}
#ifdef INBUF_PADDED
#define GETB(c) (*(c).in++)
#else
#define GETB(c) get_byte(&(c))
#endif
/**
* \brief decode a length value in the coding used by lzo
* \param x previous byte value
@ -170,10 +176,10 @@ int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
c.out = c.out_start = out;
c.out_end = (uint8_t *)out + * outlen;
c.error = 0;
x = get_byte(&c);
x = GETB(c);
if (x > 17) {
copy(&c, x - 17);
x = get_byte(&c);
x = GETB(c);
if (x < 16) c.error |= LZO_ERROR;
}
while (!c.error) {
@ -181,16 +187,16 @@ int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
if (x >> 4) {
if (x >> 6) {
cnt = (x >> 5) - 1;
back = (get_byte(&c) << 3) + ((x >> 2) & 7) + 1;
back = (GETB(c) << 3) + ((x >> 2) & 7) + 1;
} else if (x >> 5) {
cnt = get_len(&c, x, 31);
x = get_byte(&c);
back = (get_byte(&c) << 6) + (x >> 2) + 1;
x = GETB(c);
back = (GETB(c) << 6) + (x >> 2) + 1;
} else {
cnt = get_len(&c, x, 7);
back = (1 << 14) + ((x & 8) << 11);
x = get_byte(&c);
back += (get_byte(&c) << 6) + (x >> 2);
x = GETB(c);
back += (GETB(c) << 6) + (x >> 2);
if (back == (1 << 14)) {
if (cnt != 1)
c.error |= LZO_ERROR;
@ -202,15 +208,15 @@ int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
case COPY:
cnt = get_len(&c, x, 15);
copy(&c, cnt + 3);
x = get_byte(&c);
x = GETB(c);
if (x >> 4)
continue;
cnt = 1;
back = (1 << 11) + (get_byte(&c) << 2) + (x >> 2) + 1;
back = (1 << 11) + (GETB(c) << 2) + (x >> 2) + 1;
break;
case BACKPTR:
cnt = 0;
back = (get_byte(&c) << 2) + (x >> 2) + 1;
back = (GETB(c) << 2) + (x >> 2) + 1;
break;
}
copy_backptr(&c, back, cnt + 2);
@ -218,9 +224,13 @@ int lzo1x_decode(void *out, int *outlen, void *in, int *inlen) {
state = cnt ? BACKPTR : COPY;
if (cnt)
copy(&c, cnt);
x = get_byte(&c);
x = GETB(c);
if (c.in > c.in_end)
c.error |= LZO_INPUT_DEPLETED;
}
*inlen = c.in_end - c.in;
if (c.in > c.in_end)
*inlen = 0;
*outlen = c.out_end - c.out;
return c.error;
}

2
libavcodec/lzo.h
View File

@ -27,7 +27,7 @@
#define LZO_INVALID_BACKPTR 4
#define LZO_ERROR 8
#define LZO_INPUT_PADDING 4
#define LZO_INPUT_PADDING 8
#define LZO_OUTPUT_PADDING 12
int lzo1x_decode(void *out, int *outlen, void *in, int *inlen);