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avutil/fifo: add function av_fifo_generic_peek_at()

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Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
This commit is contained in:
Zhang Rui
2015-10-14 14:20:07 +08:00
committed by Michael Niedermayer
parent 55d3e97970
commit 87ff61b9ab
3 changed files with 99 additions and 0 deletions
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61
libavutil/fifo.c
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@@ -148,6 +148,44 @@ int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size,
return total - size;
}
int av_fifo_generic_peek_at(AVFifoBuffer *f, void *dest, int offset, int buf_size, void (*func)(void*, void*, int))
{
uint8_t *rptr = f->rptr;
av_assert2(offset >= 0);
/*
* *ndx are indexes modulo 2^32, they are intended to overflow,
* to handle *ndx greater than 4gb.
*/
av_assert2(buf_size + (unsigned)offset <= f->wndx - f->rndx);
if (offset >= f->end - rptr)
rptr += offset - (f->end - f->buffer);
else
rptr += offset;
while (buf_size > 0) {
int len;
if (rptr >= f->end)
rptr -= f->end - f->buffer;
len = FFMIN(f->end - rptr, buf_size);
if (func)
func(dest, rptr, len);
else {
memcpy(dest, rptr, len);
dest = (uint8_t *)dest + len;
}
buf_size -= len;
rptr += len;
}
return 0;
}
int av_fifo_generic_peek(AVFifoBuffer *f, void *dest, int buf_size,
void (*func)(void *, void *, int))
{
@@ -221,6 +259,14 @@ int main(void)
}
printf("\n");
/* peek_at at FIFO */
n = av_fifo_size(fifo) / sizeof(int);
for (i = 0; i < n; i++) {
av_fifo_generic_peek_at(fifo, &j, i * sizeof(int), sizeof(j), NULL);
printf("%d: %d\n", i, j);
}
printf("\n");
/* read data */
for (i = 0; av_fifo_size(fifo) >= sizeof(int); i++) {
av_fifo_generic_read(fifo, &j, sizeof(int), NULL);
@@ -228,6 +274,21 @@ int main(void)
}
printf("\n");
/* test *ndx overflow */
av_fifo_reset(fifo);
fifo->rndx = fifo->wndx = ~(uint32_t)0 - 5;
/* fill data */
for (i = 0; av_fifo_space(fifo) >= sizeof(int); i++)
av_fifo_generic_write(fifo, &i, sizeof(int), NULL);
/* peek_at at FIFO */
n = av_fifo_size(fifo) / sizeof(int);
for (i = 0; i < n; i++) {
av_fifo_generic_peek_at(fifo, &j, i * sizeof(int), sizeof(j), NULL);
printf("%d: %d\n", i, j);
}
av_fifo_free(fifo);
return 0;