PeerStreamer

/*

 * 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 "libavutil/crc.h"

#include "libavutil/intreadwrite.h"

#include "avformat.h"

#include "avio.h"

#include "internal.h"

#include <stdarg.h>

#define IO_BUFFER_SIZE 32768

/**

 * Do seeks within this distance ahead of the current buffer by skipping

 * data instead of calling the protocol seek function, for seekable

 * protocols.

 */

#define SHORT_SEEK_THRESHOLD 4096

static void fill_buffer(ByteIOContext *s);

#if !FF_API_URL_RESETBUF

static int url_resetbuf(ByteIOContext *s, int flags);

#endif

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),

                  int64_t (*seek)(void *opaque, int64_t offset, int whence))

{

    s->buffer = buffer;

    s->buffer_size = buffer_size;

    s->buf_ptr = buffer;

    s->opaque = opaque;

    url_resetbuf(s, write_flag ? URL_WRONLY : URL_RDONLY);

    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;

    }

    s->read_pause = NULL;

    s->read_seek  = NULL;

    return 0;

}

ByteIOContext *av_alloc_put_byte(

                  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),

                  int64_t (*seek)(void *opaque, int64_t offset, int whence))

{

    ByteIOContext *s = av_mallocz(sizeof(ByteIOContext));

    init_put_byte(s, buffer, buffer_size, write_flag, opaque,

                  read_packet, write_packet, seek);

    return s;

}

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_nbyte(ByteIOContext *s, int b, int count)

{

    while (count > 0) {

        int len = FFMIN(s->buf_end - s->buf_ptr, count);

        memset(s->buf_ptr, b, len);

        s->buf_ptr += len;

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

            flush_buffer(s);

        count -= len;

    }

}

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

{

    while (size > 0) {

        int len = FFMIN(s->buf_end - s->buf_ptr, 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;

}

int64_t url_fseek(ByteIOContext *s, int64_t offset, int whence)

{

    int64_t offset1;

    int64_t pos;

    int force = whence & AVSEEK_FORCE;

    whence &= ~AVSEEK_FORCE;

    if(!s)

        return AVERROR(EINVAL);

    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 ||

               offset1 <= s->buf_end + SHORT_SEEK_THRESHOLD - s->buffer) &&

               !s->write_flag && offset1 >= 0 &&

              (whence != SEEK_END || force)) {

        while(s->pos < offset && !s->eof_reached)

            fill_buffer(s);

        if (s->eof_reached)

            return AVERROR_EOF;

        s->buf_ptr = s->buf_end + offset - s->pos;

    } else {

        int64_t res;

#if CONFIG_MUXERS || CONFIG_NETWORK

        if (s->write_flag) {

            flush_buffer(s);

            s->must_flush = 1;

        }

#endif /* CONFIG_MUXERS || CONFIG_NETWORK */

        if (!s->seek)

            return AVERROR(EPIPE);

        if ((res = s->seek(s->opaque, offset, SEEK_SET)) < 0)

            return res;

        if (!s->write_flag)

            s->buf_end = s->buffer;

        s->buf_ptr = s->buffer;

        s->pos = offset;

    }

    s->eof_reached = 0;

    return offset;

}

int url_fskip(ByteIOContext *s, int64_t offset)

{

    int64_t ret = url_fseek(s, offset, SEEK_CUR);

    return ret < 0 ? ret : 0;

}

int64_t url_ftell(ByteIOContext *s)

{

    return url_fseek(s, 0, SEEK_CUR);

}

int64_t url_fsize(ByteIOContext *s)

{

    int64_t size;

    if(!s)

        return AVERROR(EINVAL);

    if (!s->seek)

        return AVERROR(ENOSYS);

    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)

{

    if(!s)

        return 0;

    return s->eof_reached;

}

int url_ferror(ByteIOContext *s)

{

    if(!s)

        return 0;

    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);

}

#if FF_API_OLD_AVIO

void put_strz(ByteIOContext *s, const char *str)

{

    avio_put_str(s, str);

}

#endif

int avio_put_str(ByteIOContext *s, const char *str)

{

    int len = 1;

    if (str) {

        len += strlen(str);

        put_buffer(s, (const unsigned char *) str, len);

    } else

        put_byte(s, 0);

    return len;

}

int ff_get_v_length(uint64_t val){

    int i=1;

    while(val>>=7)

        i++;

    return i;

}

void ff_put_v(ByteIOContext *bc, uint64_t val){

    int i= ff_get_v_length(val);

    while(--i>0)

        put_byte(bc, 128 | (val>>(7*i)));

    put_byte(bc, val&127);

}

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)

{

    uint8_t *dst= !s->max_packet_size && s->buf_end - s->buffer < s->buffer_size ? s->buf_ptr : s->buffer;

    int len= s->buffer_size - (dst - s->buffer);

    int max_buffer_size = s->max_packet_size ? s->max_packet_size : IO_BUFFER_SIZE;

    /* no need to do anything if EOF already reached */

    if (s->eof_reached)

        return;

    if(s->update_checksum && dst == s->buffer){

        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;

    }

    /* make buffer smaller in case it ended up large after probing */

    if (s->buffer_size > max_buffer_size) {

        url_setbufsize(s, max_buffer_size);

        s->checksum_ptr = dst = s->buffer;

        len = s->buffer_size;

    }

    if(s->read_packet)

        len = s->read_packet(s->opaque, dst, len);

    else

        len = 0;

    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 = dst;

        s->buf_end = dst + len;

    }

}

unsigned long ff_crc04C11DB7_update(unsigned long checksum, const uint8_t *buf,

                                    unsigned int len)

{

    return av_crc(av_crc_get_table(AV_CRC_32_IEEE), checksum, buf, 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)

        fill_buffer(s);

    if (s->buf_ptr < s->buf_end)

        return *s->buf_ptr++;

    return 0;

}

int url_fgetc(ByteIOContext *s)

{

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

        fill_buffer(s);

    if (s->buf_ptr < s->buf_end)

        return *s->buf_ptr++;

    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;

        }

    }

    if (size1 == size) {

        if (url_ferror(s)) return url_ferror(s);

        if (url_feof(s))   return AVERROR_EOF;

    }

    return size1 - size;

}

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

{

    int len;

    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;

    if (!len) {

        if (url_ferror(s)) return url_ferror(s);

        if (url_feof(s))   return AVERROR_EOF;

    }

    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;

}

int ff_get_line(ByteIOContext *s, char *buf, int maxlen)

{

    int i = 0;

    char c;

    do {

        c = get_byte(s);

        if (c && i < maxlen-1)

            buf[i++] = c;

    } while (c != '\n' && c);

    buf[i] = 0;

    return i;

}

uint64_t get_be64(ByteIOContext *s)

{

    uint64_t val;

    val = (uint64_t)get_be32(s) << 32;

    val |= (uint64_t)get_be32(s);

    return val;

}

uint64_t ff_get_v(ByteIOContext *bc){

    uint64_t val = 0;

    int tmp;

    do{

        tmp = get_byte(bc);

        val= (val<<7) + (tmp&127);

    }while(tmp&128);

    return val;

}

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);

    *s = av_mallocz(sizeof(ByteIOContext));

    if(!*s) {

        av_free(buffer);

        return AVERROR(ENOMEM);

    }

    if (init_put_byte(*s, buffer, buffer_size,

                      (h->flags & URL_WRONLY || h->flags & URL_RDWR), h,

                      url_read, url_write, url_seek) < 0) {

        av_free(buffer);

        av_freep(s);

        return AVERROR(EIO);

    }

    (*s)->is_streamed = h->is_streamed;

    (*s)->max_packet_size = max_packet_size;

    if(h->prot) {

        (*s)->read_pause = (int (*)(void *, int))h->prot->url_read_pause;

        (*s)->read_seek  = (int64_t (*)(void *, int, int64_t, int))h->prot->url_read_seek;

    }

    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;

    url_resetbuf(s, s->write_flag ? URL_WRONLY : URL_RDONLY);

    return 0;

}

#if FF_API_URL_RESETBUF

int url_resetbuf(ByteIOContext *s, int flags)

#else

static int url_resetbuf(ByteIOContext *s, int flags)

#endif

{

#if FF_API_URL_RESETBUF

    if (flags & URL_RDWR)

        return AVERROR(EINVAL);

#else

    assert(flags == URL_WRONLY || flags == URL_RDONLY);

#endif

    if (flags & URL_WRONLY) {

        s->buf_end = s->buffer + s->buffer_size;

        s->write_flag = 1;

    } else {

        s->buf_end = s->buffer;

        s->write_flag = 0;

    }

    return 0;

}

int ff_rewind_with_probe_data(ByteIOContext *s, unsigned char *buf, int buf_size)

{

    int64_t buffer_start;

    int buffer_size;

    int overlap, new_size, alloc_size;

    if (s->write_flag)

        return AVERROR(EINVAL);

    buffer_size = s->buf_end - s->buffer;

    /* the buffers must touch or overlap */

    if ((buffer_start = s->pos - buffer_size) > buf_size)

        return AVERROR(EINVAL);

    overlap = buf_size - buffer_start;

    new_size = buf_size + buffer_size - overlap;

    alloc_size = FFMAX(s->buffer_size, new_size);

    if (alloc_size > buf_size)

        if (!(buf = av_realloc(buf, alloc_size)))

            return AVERROR(ENOMEM);

    if (new_size > buf_size) {

        memcpy(buf + buf_size, s->buffer + overlap, buffer_size - overlap);

        buf_size = new_size;

    }

    av_free(s->buffer);

    s->buf_ptr = s->buffer = buf;

    s->buffer_size = alloc_size;

    s->pos = buf_size;

    s->buf_end = s->buf_ptr + buf_size;

    s->eof_reached = 0;

    s->must_flush = 0;

    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);

    av_free(s);

    return url_close(h);

}

URLContext *url_fileno(ByteIOContext *s)

{

    return s->opaque;

}

#if 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;

}

int av_url_read_fpause(ByteIOContext *s, int pause)

{

    if (!s->read_pause)

        return AVERROR(ENOSYS);

    return s->read_pause(s->opaque, pause);

}

int64_t av_url_read_fseek(ByteIOContext *s, int stream_index,

                          int64_t timestamp, int flags)

{

    URLContext *h = s->opaque;

    int64_t ret;

    if (!s->read_seek)

        return AVERROR(ENOSYS);

    ret = s->read_seek(h, stream_index, timestamp, flags);

    if(ret >= 0) {

        int64_t pos;

        s->buf_ptr = s->buf_end; // Flush buffer

        pos = s->seek(h, 0, SEEK_CUR);

        if (pos >= 0)

            s->pos = pos;

        else if (pos != AVERROR(ENOSYS))

            ret = pos;

    }

    return ret;

}

/* 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 false. */

#if CONFIG_MUXERS || CONFIG_NETWORK

/* buffer handling */

int url_open_buf(ByteIOContext **s, uint8_t *buf, int buf_size, int flags)

{

    int ret;

    *s = av_mallocz(sizeof(ByteIOContext));

    if(!*s)

        return AVERROR(ENOMEM);

    ret = init_put_byte(*s, buf, buf_size,

                        (flags & URL_WRONLY || flags & URL_RDWR),

                        NULL, NULL, NULL, NULL);

    if(ret != 0)

        av_freep(s);

    return ret;

}

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;

    unsigned 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 AVERROR(ENOMEM);

        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 */

    AV_WB32(buf1, 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 int64_t dyn_buf_seek(void *opaque, int64_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 ret;

    unsigned io_buffer_size = max_packet_size ? max_packet_size : 1024;

    if(sizeof(DynBuffer) + io_buffer_size < io_buffer_size)

        return -1;

    d = av_mallocz(sizeof(DynBuffer) + io_buffer_size);

    if (!d)

        return AVERROR(ENOMEM);

    *s = av_mallocz(sizeof(ByteIOContext));

    if(!*s) {

        av_free(d);

        return AVERROR(ENOMEM);

    }

    d->io_buffer_size = io_buffer_size;

    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;

    } else {

        av_free(d);

        av_freep(s);

    }

    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;

    static const char padbuf[FF_INPUT_BUFFER_PADDING_SIZE] = {0};

    int padding = 0;

    /* don't attempt to pad fixed-size packet buffers */

    if (!s->max_packet_size) {

        put_buffer(s, padbuf, sizeof(padbuf));

        padding = FF_INPUT_BUFFER_PADDING_SIZE;

    }

    put_flush_packet(s);

    *pbuffer = d->buffer;

    size = d->size;

    av_free(d);

    av_free(s);

    return size - padding;

}

#endif /* CONFIG_MUXERS || CONFIG_NETWORK */