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

/*
 * Buffered I/O for ffmpeg system
 * Copyright (c) 2000,2001 Fabrice Bellard
 *
 * This file is part of FFmpeg.
 *
 * FFmpeg is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * FFmpeg is distributed in the hope that it will be useful,
 * 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
 * License along with FFmpeg; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */
#include "avformat.h"
#include "avio.h"
#include <stdarg.h>

#define IO_BUFFER_SIZE 32768

static void fill_buffer(ByteIOContext *s);

int init_put_byte(ByteIOContext *s,
                  unsigned char *buffer,
                  int buffer_size,
                  int write_flag,
                  void *opaque,
                  int (*read_packet)(void *opaque, uint8_t *buf, int buf_size),
                  int (*write_packet)(void *opaque, uint8_t *buf, int buf_size),
                  offset_t (*seek)(void *opaque, offset_t offset, int whence))
{
    s->buffer = buffer;
    s->buffer_size = buffer_size;
    s->buf_ptr = buffer;
    s->write_flag = write_flag;
    if (!s->write_flag)
        s->buf_end = buffer;
    else
        s->buf_end = buffer + buffer_size;
    s->opaque = opaque;
    s->write_packet = write_packet;
    s->read_packet = read_packet;
    s->seek = seek;
    s->pos = 0;
    s->must_flush = 0;
    s->eof_reached = 0;
    s->error = 0;
    s->is_streamed = 0;
    s->max_packet_size = 0;
    s->update_checksum= NULL;
    if(!read_packet && !write_flag){
        s->pos = buffer_size;
        s->buf_end = s->buffer + buffer_size;
    }
    return 0;
}

static void flush_buffer(ByteIOContext *s)
{
    if (s->buf_ptr > s->buffer) {
        if (s->write_packet && !s->error){
            int ret= s->write_packet(s->opaque, s->buffer, s->buf_ptr - s->buffer);
            if(ret < 0){
                s->error = ret;
            }
        }
        if(s->update_checksum){
            s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
            s->checksum_ptr= s->buffer;
        }
        s->pos += s->buf_ptr - s->buffer;
    }
    s->buf_ptr = s->buffer;
}

void put_byte(ByteIOContext *s, int b)
{
    *(s->buf_ptr)++ = b;
    if (s->buf_ptr >= s->buf_end)
        flush_buffer(s);
}

void put_buffer(ByteIOContext *s, const unsigned char *buf, int size)
{
    int len;

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

        if (s->buf_ptr >= s->buf_end)
            flush_buffer(s);

        buf += len;
        size -= len;
    }
}

void put_flush_packet(ByteIOContext *s)
{
    flush_buffer(s);
    s->must_flush = 0;
}

offset_t url_fseek(ByteIOContext *s, offset_t offset, int whence)
{
    offset_t offset1;
    offset_t pos= s->pos - (s->write_flag ? 0 : (s->buf_end - s->buffer));

    if (whence != SEEK_CUR && whence != SEEK_SET)
        return AVERROR(EINVAL);

    if (whence == SEEK_CUR) {
        offset1 = pos + (s->buf_ptr - s->buffer);
        if (offset == 0)
            return offset1;
        offset += offset1;
    }
    offset1 = offset - pos;
    if (!s->must_flush &&
        offset1 >= 0 && offset1 < (s->buf_end - s->buffer)) {
        /* can do the seek inside the buffer */
        s->buf_ptr = s->buffer + offset1;
    } else if(s->is_streamed && !s->write_flag &&
              offset1 >= 0 && offset1 < (s->buf_end - s->buffer) + (1<<16)){
        while(s->pos < offset && !s->eof_reached)
            fill_buffer(s);
        s->buf_ptr = s->buf_end + offset - s->pos;
    } else {
        offset_t res = AVERROR(EPIPE);

#if defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK)
        if (s->write_flag) {
            flush_buffer(s);
            s->must_flush = 1;
        } else
#endif /* defined(CONFIG_MUXERS) || defined(CONFIG_NETWORK) */
        {
            s->buf_end = s->buffer;
        }
        s->buf_ptr = s->buffer;
        if (!s->seek || (res = s->seek(s->opaque, offset, SEEK_SET)) < 0)
            return res;
        s->pos = offset;
    }
    s->eof_reached = 0;
    return offset;
}

void url_fskip(ByteIOContext *s, offset_t offset)
{
    url_fseek(s, offset, SEEK_CUR);
}

offset_t url_ftell(ByteIOContext *s)
{
    return url_fseek(s, 0, SEEK_CUR);
}

offset_t url_fsize(ByteIOContext *s)
{
    offset_t size;

    if (!s->seek)
        return AVERROR(EPIPE);
    size = s->seek(s->opaque, 0, AVSEEK_SIZE);
    if(size<0){
        if ((size = s->seek(s->opaque, -1, SEEK_END)) < 0)
            return size;
        size++;
        s->seek(s->opaque, s->pos, SEEK_SET);
    }
    return size;
}

int url_feof(ByteIOContext *s)
{
    return s->eof_reached;
}

int url_ferror(ByteIOContext *s)
{
    return s->error;
}

void put_le32(ByteIOContext *s, unsigned int val)
{
    put_byte(s, val);
    put_byte(s, val >> 8);
    put_byte(s, val >> 16);
    put_byte(s, val >> 24);
}

void put_be32(ByteIOContext *s, unsigned int val)
{
    put_byte(s, val >> 24);
    put_byte(s, val >> 16);
    put_byte(s, val >> 8);
    put_byte(s, val);
}

void put_strz(ByteIOContext *s, const char *str)
{
    if (str)
        put_buffer(s, (const unsigned char *) str, strlen(str) + 1);
    else
        put_byte(s, 0);
}

void put_le64(ByteIOContext *s, uint64_t val)
{
    put_le32(s, (uint32_t)(val & 0xffffffff));
    put_le32(s, (uint32_t)(val >> 32));
}

void put_be64(ByteIOContext *s, uint64_t val)
{
    put_be32(s, (uint32_t)(val >> 32));
    put_be32(s, (uint32_t)(val & 0xffffffff));
}

void put_le16(ByteIOContext *s, unsigned int val)
{
    put_byte(s, val);
    put_byte(s, val >> 8);
}

void put_be16(ByteIOContext *s, unsigned int val)
{
    put_byte(s, val >> 8);
    put_byte(s, val);
}

void put_le24(ByteIOContext *s, unsigned int val)
{
    put_le16(s, val & 0xffff);
    put_byte(s, val >> 16);
}

void put_be24(ByteIOContext *s, unsigned int val)
{
    put_be16(s, val >> 8);
    put_byte(s, val);
}

void put_tag(ByteIOContext *s, const char *tag)
{
    while (*tag) {
        put_byte(s, *tag++);
    }
}

/* Input stream */

static void fill_buffer(ByteIOContext *s)
{
    int len=0;

    /* no need to do anything if EOF already reached */
    if (s->eof_reached)
        return;

    if(s->update_checksum){
        if(s->buf_end > s->checksum_ptr)
            s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_end - s->checksum_ptr);
        s->checksum_ptr= s->buffer;
    }

    if(s->read_packet)
        len = s->read_packet(s->opaque, s->buffer, s->buffer_size);
    if (len <= 0) {
        /* do not modify buffer if EOF reached so that a seek back can
           be done without rereading data */
        s->eof_reached = 1;
        if(len<0)
            s->error= len;
    } else {
        s->pos += len;
        s->buf_ptr = s->buffer;
        s->buf_end = s->buffer + len;
    }
}

unsigned long get_checksum(ByteIOContext *s){
    s->checksum= s->update_checksum(s->checksum, s->checksum_ptr, s->buf_ptr - s->checksum_ptr);
    s->update_checksum= NULL;
    return s->checksum;
}

void init_checksum(ByteIOContext *s, unsigned long (*update_checksum)(unsigned long c, const uint8_t *p, unsigned int len), unsigned long checksum){
    s->update_checksum= update_checksum;
    if(s->update_checksum){
        s->checksum= checksum;
        s->checksum_ptr= s->buf_ptr;
    }
}

/* XXX: put an inline version */
int get_byte(ByteIOContext *s)
{
    if (s->buf_ptr < s->buf_end) {
        return *s->buf_ptr++;
    } else {
        fill_buffer(s);
        if (s->buf_ptr < s->buf_end)
            return *s->buf_ptr++;
        else
            return 0;
    }
}

int url_fgetc(ByteIOContext *s)
{
    if (s->buf_ptr < s->buf_end) {
        return *s->buf_ptr++;
    } else {
        fill_buffer(s);
        if (s->buf_ptr < s->buf_end)
            return *s->buf_ptr++;
        else
            return URL_EOF;
    }
}

int get_buffer(ByteIOContext *s, unsigned char *buf, int size)
{
    int len, size1;

    size1 = size;
    while (size > 0) {
        len = s->buf_end - s->buf_ptr;
        if (len > size)
            len = size;
        if (len == 0) {
            if(size > s->buffer_size && !s->update_checksum){
                if(s->read_packet)
                    len = s->read_packet(s->opaque, buf, size);
                if (len <= 0) {
                    /* do not modify buffer if EOF reached so that a seek back can
                    be done without rereading data */
                    s->eof_reached = 1;
                    if(len<0)
                        s->error= len;
                    break;
                } else {
                    s->pos += len;
                    size -= len;
                    buf += len;
                    s->buf_ptr = s->buffer;
                    s->buf_end = s->buffer/* + len*/;
                }
            }else{
                fill_buffer(s);
                len = s->buf_end - s->buf_ptr;
                if (len == 0)
                    break;
            }
        } else {
            memcpy(buf, s->buf_ptr, len);
            buf += len;
            s->buf_ptr += len;
            size -= len;
        }
    }
    return size1 - size;
}

int get_partial_buffer(ByteIOContext *s, unsigned char *buf, int size)
{
    int len;