fifo.c 4.23 KB
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/*
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 * a very simple circular buffer FIFO implementation
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 * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
 * Copyright (c) 2006 Roman Shaposhnik
 *
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 * This file is part of Libav.
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 *
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 * Libav is free software; you can redistribute it and/or
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 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
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 * version 2.1 of the License, or (at your option) any later version.
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 *
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 * Libav is distributed in the hope that it will be useful,
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 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
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 * License along with Libav; if not, write to the Free Software
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 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
#include "common.h"
#include "fifo.h"

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AVFifoBuffer *av_fifo_alloc(unsigned int size)
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{
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    AVFifoBuffer *f = av_mallocz(sizeof(AVFifoBuffer));
    if (!f)
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        return NULL;
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    f->buffer = av_malloc(size);
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    f->end    = f->buffer + size;
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    av_fifo_reset(f);
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    if (!f->buffer)
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        av_freep(&f);
    return f;
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}

void av_fifo_free(AVFifoBuffer *f)
{
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    if (f) {
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        av_free(f->buffer);
        av_free(f);
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    }
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}

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void av_fifo_reset(AVFifoBuffer *f)
{
    f->wptr = f->rptr = f->buffer;
    f->wndx = f->rndx = 0;
}

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int av_fifo_size(AVFifoBuffer *f)
{
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    return (uint32_t)(f->wndx - f->rndx);
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}

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int av_fifo_space(AVFifoBuffer *f)
{
    return f->end - f->buffer - av_fifo_size(f);
}

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int av_fifo_realloc2(AVFifoBuffer *f, unsigned int new_size)
{
    unsigned int old_size = f->end - f->buffer;
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    if (old_size < new_size) {
        int len          = av_fifo_size(f);
        AVFifoBuffer *f2 = av_fifo_alloc(new_size);
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        if (!f2)
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            return -1;
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        av_fifo_generic_read(f, f2->buffer, len, NULL);
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        f2->wptr += len;
        f2->wndx += len;
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        av_free(f->buffer);
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        *f = *f2;
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        av_free(f2);
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    }
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    return 0;
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}

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/* src must NOT be const as it can be a context for func that may need
 * updating (like a pointer or byte counter) */
int av_fifo_generic_write(AVFifoBuffer *f, void *src, int size,
                          int (*func)(void *, void *, int))
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{
    int total = size;
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    do {
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        int len = FFMIN(f->end - f->wptr, size);
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        if (func) {
            if (func(src, f->wptr, len) <= 0)
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                break;
        } else {
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            memcpy(f->wptr, src, len);
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            src = (uint8_t *)src + len;
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        }
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// Write memory barrier needed for SMP here in theory
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        f->wptr += len;
        if (f->wptr >= f->end)
            f->wptr = f->buffer;
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        f->wndx += len;
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        size    -= len;
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    } while (size > 0);
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    return total - size;
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}

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int av_fifo_generic_read(AVFifoBuffer *f, void *dest, int buf_size,
                         void (*func)(void *, void *, int))
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{
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// Read memory barrier needed for SMP here in theory
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    do {
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        int len = FFMIN(f->end - f->rptr, buf_size);
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        if (func)
            func(dest, f->rptr, len);
        else {
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            memcpy(dest, f->rptr, len);
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            dest = (uint8_t *)dest + len;
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        }
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// memory barrier needed for SMP here in theory
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        av_fifo_drain(f, len);
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        buf_size -= len;
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    } while (buf_size > 0);
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    return 0;
}

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/** Discard data from the FIFO. */
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void av_fifo_drain(AVFifoBuffer *f, int size)
{
    f->rptr += size;
    if (f->rptr >= f->end)
        f->rptr -= f->end - f->buffer;
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    f->rndx += size;
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}
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#ifdef TEST

int main(void)
{
    /* create a FIFO buffer */
    AVFifoBuffer *fifo = av_fifo_alloc(13 * sizeof(int));
    int i, j, n;

    /* fill data */
    for (i = 0; av_fifo_space(fifo) >= sizeof(int); i++)
        av_fifo_generic_write(fifo, &i, sizeof(int), NULL);

    /* peek at FIFO */
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    n = av_fifo_size(fifo) / sizeof(int);
    for (i = -n + 1; i < n; i++) {
        int *v = (int *)av_fifo_peek2(fifo, i * sizeof(int));
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        printf("%d: %d\n", i, *v);
    }
    printf("\n");

    /* read data */
    for (i = 0; av_fifo_size(fifo) >= sizeof(int); i++) {
        av_fifo_generic_read(fifo, &j, sizeof(int), NULL);
        printf("%d ", j);
    }
    printf("\n");

    av_fifo_free(fifo);

    return 0;
}

#endif