/*
  * AVC helper functions for muxers
  * Copyright (c) 2006 Baptiste Coudurier <baptiste.coudurier@smartjog.com>
  *
  * 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/intreadwrite.h"

 #include "avformat.h"
 #include "avio.h"

 #include "avc.h"

 static const uint8_t *ff_avc_find_startcode_internal(const uint8_t *p, const uint8_t *end)

 {

     const uint8_t *a = p + 4 - ((intptr_t)p & 3);

     for (end -= 3; p < a && p < end; p++) {
         if (p[0] == 0 && p[1] == 0 && p[2] == 1)

             return p;
     }
 

     for (end -= 3; p < end; p += 4) {

         uint32_t x = *(const uint32_t*)p;

 //      if ((x - 0x01000100) & (~x) & 0x80008000) // little endian
 //      if ((x - 0x00010001) & (~x) & 0x00800080) // big endian
         if ((x - 0x01010101) & (~x) & 0x80808080) { // generic
             if (p[1] == 0) {
                 if (p[0] == 0 && p[2] == 1)

                     return p;

                 if (p[2] == 0 && p[3] == 1)
                     return p+1;

             }

             if (p[3] == 0) {
                 if (p[2] == 0 && p[4] == 1)

                     return p+2;

                 if (p[4] == 0 && p[5] == 1)
                     return p+3;

             }
         }
     }
 

     for (end += 3; p < end; p++) {
         if (p[0] == 0 && p[1] == 0 && p[2] == 1)

             return p;
     }
 
     return end + 3;
 }
 

 const uint8_t *ff_avc_find_startcode(const uint8_t *p, const uint8_t *end){
     const uint8_t *out= ff_avc_find_startcode_internal(p, end);
     if(p<out && out<end && !out[-1]) out--;
     return out;
 }
 

 int ff_avc_parse_nal_units(AVIOContext *pb, const uint8_t *buf_in, int size)

 {

     const uint8_t *p = buf_in;

     const uint8_t *end = p + size;

     const uint8_t *nal_start, *nal_end;

     size = 0;

     nal_start = ff_avc_find_startcode(p, end);

     for (;;) {
         while (nal_start < end && !*(nal_start++));
         if (nal_start == end)
             break;
 

         nal_end = ff_avc_find_startcode(nal_start, end);

         avio_wb32(pb, nal_end - nal_start);
         avio_write(pb, nal_start, nal_end - nal_start);

         size += 4 + nal_end - nal_start;

         nal_start = nal_end;
     }

     return size;

 }
 

 int ff_avc_parse_nal_units_buf(const uint8_t *buf_in, uint8_t **buf, int *size)

 {

     AVIOContext *pb;

     int ret = avio_open_dyn_buf(&pb);

     if(ret < 0)
         return ret;
 
     ff_avc_parse_nal_units(pb, buf_in, *size);
 

     av_freep(buf);

     *size = avio_close_dyn_buf(pb, buf);

     return 0;
 }
 

 int ff_isom_write_avcc(AVIOContext *pb, const uint8_t *data, int len)

 {
     if (len > 6) {
         /* check for h264 start code */

         if (AV_RB32(data) == 0x00000001 ||
             AV_RB24(data) == 0x000001) {

             uint8_t *buf=NULL, *end, *start;

             uint32_t sps_size=0, pps_size=0;
             uint8_t *sps=0, *pps=0;
 

             int ret = ff_avc_parse_nal_units_buf(data, &buf, &len);

             if (ret < 0)
                 return ret;

             start = buf;

             end = buf + len;
 
             /* look for sps and pps */

             while (end - buf > 4) {
                 uint32_t size;

                 uint8_t nal_type;

                 size = FFMIN(AV_RB32(buf), end - buf - 4);
                 buf += 4;
                 nal_type = buf[0] & 0x1f;
 

                 if (nal_type == 7) { /* SPS */

                     sps = buf;

                     sps_size = size;
                 } else if (nal_type == 8) { /* PPS */

                     pps = buf;

                     pps_size = size;
                 }

 
                 buf += size;

             }

 
             if (!sps || !pps || sps_size < 4 || sps_size > UINT16_MAX || pps_size > UINT16_MAX)
                 return AVERROR_INVALIDDATA;

             avio_w8(pb, 1); /* version */
             avio_w8(pb, sps[1]); /* profile */
             avio_w8(pb, sps[2]); /* profile compat */
             avio_w8(pb, sps[3]); /* level */
             avio_w8(pb, 0xff); /* 6 bits reserved (111111) + 2 bits nal size length - 1 (11) */
             avio_w8(pb, 0xe1); /* 3 bits reserved (111) + 5 bits number of sps (00001) */
 
             avio_wb16(pb, sps_size);
             avio_write(pb, sps, sps_size);
             avio_w8(pb, 1); /* number of pps */
             avio_wb16(pb, pps_size);
             avio_write(pb, pps, pps_size);

             av_free(start);

         } else {

             avio_write(pb, data, len);

         }
     }
     return 0;
 }