aviobuf.c

ffmpeg的完整源代码和作者自己写的文档。不但有在Linux的工程哦

    if(size<0)
        return -1;

    len = s->buf_end - s->buf_ptr;
    if (len == 0) {
        fill_buffer(s);
        len = s->buf_end - s->buf_ptr;
    }
    if (len > size)
        len = size;
    memcpy(buf, s->buf_ptr, len);
    s->buf_ptr += len;
    return len;
}

unsigned int get_le16(ByteIOContext *s)
{
    unsigned int val;
    val = get_byte(s);
    val |= get_byte(s) << 8;
    return val;
}

unsigned int get_le24(ByteIOContext *s)
{
    unsigned int val;
    val = get_le16(s);
    val |= get_byte(s) << 16;
    return val;
}

unsigned int get_le32(ByteIOContext *s)
{
    unsigned int val;
    val = get_le16(s);
    val |= get_le16(s) << 16;
    return val;
}

uint64_t get_le64(ByteIOContext *s)
{
    uint64_t val;
    val = (uint64_t)get_le32(s);
    val |= (uint64_t)get_le32(s) << 32;
    return val;
}

unsigned int get_be16(ByteIOContext *s)
{
    unsigned int val;
    val = get_byte(s) << 8;
    val |= get_byte(s);
    return val;
}

unsigned int get_be24(ByteIOContext *s)
{
    unsigned int val;
    val = get_be16(s) << 8;
    val |= get_byte(s);
    return val;
}
unsigned int get_be32(ByteIOContext *s)
{
    unsigned int val;
    val = get_be16(s) << 16;
    val |= get_be16(s);
    return val;
}

char *get_strz(ByteIOContext *s, char *buf, int maxlen)
{
    int i = 0;
    char c;

    while ((c = get_byte(s))) {
        if (i < maxlen-1)
            buf[i++] = c;
    }

    buf[i] = 0; /* Ensure null terminated, but may be truncated */

    return buf;
}

uint64_t get_be64(ByteIOContext *s)
{
    uint64_t val;
    val = (uint64_t)get_be32(s) << 32;
    val |= (uint64_t)get_be32(s);
    return val;
}

/* link with avio functions */

#ifdef CONFIG_MUXERS
static int url_write_packet(void *opaque, uint8_t *buf, int buf_size)
{
    URLContext *h = opaque;
    return url_write(h, buf, buf_size);
}
#else
#define         url_write_packet NULL
#endif //CONFIG_MUXERS

static int url_read_packet(void *opaque, uint8_t *buf, int buf_size)
{
    URLContext *h = opaque;
    return url_read(h, buf, buf_size);
}

static offset_t url_seek_packet(void *opaque, offset_t offset, int whence)
{
    URLContext *h = opaque;
    return url_seek(h, offset, whence);
    //return 0;
}

int url_fdopen(ByteIOContext *s, URLContext *h)
{
    uint8_t *buffer;
    int buffer_size, max_packet_size;


    max_packet_size = url_get_max_packet_size(h);
    if (max_packet_size) {
        buffer_size = max_packet_size; /* no need to bufferize more than one packet */
    } else {
        buffer_size = IO_BUFFER_SIZE;
    }
    buffer = av_malloc(buffer_size);
    if (!buffer)
        return AVERROR(ENOMEM);

    if (init_put_byte(s, buffer, buffer_size,
                      (h->flags & URL_WRONLY || h->flags & URL_RDWR), h,
                      url_read_packet, url_write_packet, url_seek_packet) < 0) {
        av_free(buffer);
        return AVERROR(EIO);
    }
    s->is_streamed = h->is_streamed;
    s->max_packet_size = max_packet_size;
    return 0;
}

int url_setbufsize(ByteIOContext *s, int buf_size)
{
    uint8_t *buffer;
    buffer = av_malloc(buf_size);
    if (!buffer)
        return AVERROR(ENOMEM);

    av_free(s->buffer);
    s->buffer = buffer;
    s->buffer_size = buf_size;
    s->buf_ptr = buffer;
    if (!s->write_flag)
        s->buf_end = buffer;
    else
        s->buf_end = buffer + buf_size;
    return 0;
}

int url_fopen(ByteIOContext *s, const char *filename, int flags)
{
    URLContext *h;
    int err;

    err = url_open(&h, filename, flags);
    if (err < 0)
        return err;
    err = url_fdopen(s, h);
    if (err < 0) {
        url_close(h);
        return err;
    }
    return 0;
}

int url_fclose(ByteIOContext *s)
{
    URLContext *h = s->opaque;

    av_free(s->buffer);
    memset(s, 0, sizeof(ByteIOContext));
    return url_close(h);
}

URLContext *url_fileno(ByteIOContext *s)
{
    return s->opaque;
}

#ifdef CONFIG_MUXERS
int url_fprintf(ByteIOContext *s, const char *fmt, ...)
{
    va_list ap;
    char buf[4096];
    int ret;

    va_start(ap, fmt);
    ret = vsnprintf(buf, sizeof(buf), fmt, ap);
    va_end(ap);
    put_buffer(s, buf, strlen(buf));
    return ret;
}
#endif //CONFIG_MUXERS

char *url_fgets(ByteIOContext *s, char *buf, int buf_size)
{
    int c;
    char *q;

    c = url_fgetc(s);
    if (c == EOF)
        return NULL;
    q = buf;
    for(;;) {
        if (c == EOF || c == '\n')
            break;
        if ((q - buf) < buf_size - 1)
            *q++ = c;
        c = url_fgetc(s);
    }
    if (buf_size > 0)
        *q = '\0';
    return buf;
}

int url_fget_max_packet_size(ByteIOContext *s)
{
    return s->max_packet_size;
}

/* url_open_dyn_buf and url_close_dyn_buf are used in rtp.c to send a response
 * back to the server even if CONFIG_MUXERS is not set. */
#if defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK)
/* buffer handling */
int url_open_buf(ByteIOContext *s, uint8_t *buf, int buf_size, int flags)
{
    return init_put_byte(s, buf, buf_size,
                         (flags & URL_WRONLY || flags & URL_RDWR),
                         NULL, NULL, NULL, NULL);
}

int url_close_buf(ByteIOContext *s)
{
    put_flush_packet(s);
    return s->buf_ptr - s->buffer;
}

/* output in a dynamic buffer */

typedef struct DynBuffer {
    int pos, size, allocated_size;
    uint8_t *buffer;
    int io_buffer_size;
    uint8_t io_buffer[1];
} DynBuffer;

static int dyn_buf_write(void *opaque, uint8_t *buf, int buf_size)
{
    DynBuffer *d = opaque;
    int new_size, new_allocated_size;

    /* reallocate buffer if needed */
    new_size = d->pos + buf_size;
    new_allocated_size = d->allocated_size;
    if(new_size < d->pos || new_size > INT_MAX/2)
        return -1;
    while (new_size > new_allocated_size) {
        if (!new_allocated_size)
            new_allocated_size = new_size;
        else
            new_allocated_size += new_allocated_size / 2 + 1;
    }

    if (new_allocated_size > d->allocated_size) {
        d->buffer = av_realloc(d->buffer, new_allocated_size);
        if(d->buffer == NULL)
             return -1234;
        d->allocated_size = new_allocated_size;
    }
    memcpy(d->buffer + d->pos, buf, buf_size);
    d->pos = new_size;
    if (d->pos > d->size)
        d->size = d->pos;
    return buf_size;
}

static int dyn_packet_buf_write(void *opaque, uint8_t *buf, int buf_size)
{
    unsigned char buf1[4];
    int ret;

    /* packetized write: output the header */
    buf1[0] = (buf_size >> 24);
    buf1[1] = (buf_size >> 16);
    buf1[2] = (buf_size >> 8);
    buf1[3] = (buf_size);
    ret= dyn_buf_write(opaque, buf1, 4);
    if(ret < 0)
        return ret;

    /* then the data */
    return dyn_buf_write(opaque, buf, buf_size);
}

static offset_t dyn_buf_seek(void *opaque, offset_t offset, int whence)
{
    DynBuffer *d = opaque;

    if (whence == SEEK_CUR)
        offset += d->pos;
    else if (whence == SEEK_END)
        offset += d->size;
    if (offset < 0 || offset > 0x7fffffffLL)
        return -1;
    d->pos = offset;
    return 0;
}

static int url_open_dyn_buf_internal(ByteIOContext *s, int max_packet_size)
{
    DynBuffer *d;
    int io_buffer_size, ret;

    if (max_packet_size)
        io_buffer_size = max_packet_size;
    else
        io_buffer_size = 1024;

    if(sizeof(DynBuffer) + io_buffer_size < io_buffer_size)
        return -1;
    d = av_malloc(sizeof(DynBuffer) + io_buffer_size);
    if (!d)
        return -1;
    d->io_buffer_size = io_buffer_size;
    d->buffer = NULL;
    d->pos = 0;
    d->size = 0;
    d->allocated_size = 0;
    ret = init_put_byte(s, d->io_buffer, io_buffer_size,
                        1, d, NULL,
                        max_packet_size ? dyn_packet_buf_write : dyn_buf_write,
                        max_packet_size ? NULL : dyn_buf_seek);
    if (ret == 0) {
        s->max_packet_size = max_packet_size;
    }
    return ret;
}

int url_open_dyn_buf(ByteIOContext *s)
{
    return url_open_dyn_buf_internal(s, 0);
}

int url_open_dyn_packet_buf(ByteIOContext *s, int max_packet_size)
{
    if (max_packet_size <= 0)
        return -1;
    return url_open_dyn_buf_internal(s, max_packet_size);
}

int url_close_dyn_buf(ByteIOContext *s, uint8_t **pbuffer)
{
    DynBuffer *d = s->opaque;
    int size;

    put_flush_packet(s);

    *pbuffer = d->buffer;
    size = d->size;
    av_free(d);
    return size;
}
#endif /* CONFIG_MUXERS || CONFIG_NETWORK */