/*
  * RTMP network protocol
  * Copyright (c) 2009 Konstantin Shishkov
  *

  * 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
  */
 
 /**
  * @file
  * RTMP protocol digest
  */
 
 #include <stdint.h>
 
 #include "libavutil/error.h"
 #include "libavutil/hmac.h"
 
 #include "rtmp.h"
 
 int ff_rtmp_calc_digest(const uint8_t *src, int len, int gap,
                         const uint8_t *key, int keylen, uint8_t *dst)
 {
     AVHMAC *hmac;
 
     hmac = av_hmac_alloc(AV_HMAC_SHA256);
     if (!hmac)
         return AVERROR(ENOMEM);
 
     av_hmac_init(hmac, key, keylen);
     if (gap <= 0) {
         av_hmac_update(hmac, src, len);
     } else { //skip 32 bytes used for storing digest
         av_hmac_update(hmac, src, gap);
         av_hmac_update(hmac, src + gap + 32, len - gap - 32);
     }
     av_hmac_final(hmac, dst, 32);
 
     av_hmac_free(hmac);
 
     return 0;
 }
 
 int ff_rtmp_calc_digest_pos(const uint8_t *buf, int off, int mod_val,
                             int add_val)
 {
     int i, digest_pos = 0;
 
     for (i = 0; i < 4; i++)
         digest_pos += buf[i + off];
     digest_pos = digest_pos % mod_val + add_val;
 
     return digest_pos;
 }