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Code Issues Releases Activity

lavu/fifo: do not copy the whole fifo when reallocating

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av_realloc() the buffer and only move the part of the ring buffer that
needs it. Also avoids allocating a temporary fifo.
This commit is contained in:
Anton Khirnov 2021-12-30 15:06:15 +01:00
parent 5010c481d1
commit 549ccea54e
1 changed files with 24 additions and 10 deletions
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34
libavutil/fifo.c
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@ -27,7 +27,7 @@
AVFifoBuffer *av_fifo_alloc_array(size_t nmemb, size_t size)
{
AVFifoBuffer *f;
void *buffer = av_malloc_array(nmemb, size);
void *buffer = av_realloc_array(NULL, nmemb, size);
if (!buffer)
return NULL;
f = av_mallocz(sizeof(AVFifoBuffer));
@ -83,17 +83,31 @@ int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
unsigned int old_size = f->end - f->buffer;
if (old_size < new_size) {
int len = av_fifo_size(f);
AVFifoBuffer *f2 = av_fifo_alloc(new_size);
size_t offset_r = f->rptr - f->buffer;
size_t offset_w = f->wptr - f->buffer;
uint8_t *tmp;
if (!f2)
tmp = av_realloc(f->buffer, new_size);
if (!tmp)
return AVERROR(ENOMEM);
av_fifo_generic_read(f, f2->buffer, len, NULL);
f2->wptr += len;
f2->wndx += len;
av_free(f->buffer);
*f = *f2;
av_free(f2);
// move the data from the beginning of the ring buffer
// to the newly allocated space
// the second condition distinguishes full vs empty fifo
if (offset_w <= offset_r && av_fifo_size(f)) {
const size_t copy = FFMIN(new_size - old_size, offset_w);
memcpy(tmp + old_size, tmp, copy);
if (copy < offset_w) {
memmove(tmp, tmp + copy , offset_w - copy);
offset_w -= copy;
} else
offset_w = old_size + copy;
}
f->buffer = tmp;
f->end = f->buffer + new_size;
f->rptr = f->buffer + offset_r;
f->wptr = f->buffer + offset_w;
}
return 0;
}