iSAC: Pad with zeros instead of random data, to make testing easier

webrtc/modules/audio_coding/codecs/isac/main/source/isac.c

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 697 matching lines @@
       ptrGarbage = &encoded[streamLenLB + 1 + streamLenUB];
       limit = streamLen + (255 - encoded[streamLenLB]);
     }
     minBytes = (minBytes > limit) ? limit : minBytes;
 
     garbageLen = (minBytes > streamLen) ? (uint8_t)(minBytes - streamLen) : 0;
 
     /* Save data for creation of multiple bit-streams. */
     /* If bit-stream too short then add garbage at the end. */
     if (garbageLen > 0) {
-      for (k = 0; k < garbageLen; k++) {
-        ptrGarbage[k] = (uint8_t)(rand() & 0xFF);
-      }
+      /* Overwrite the garbage area to avoid leaking possibly sensitive data
+         over the network. This also makes the output deterministic. */
+      memset(ptrGarbage, 0, garbageLen);
+
       /* For a correct length of the upper-band bit-stream together
        * with the garbage. Garbage is embeded in upper-band bit-stream.
        * That is the only way to preserve backward compatibility. */
       if ((instISAC->bandwidthKHz == isac8kHz) ||
           (streamLenUB == 0)) {
         encoded[streamLenLB] = garbageLen;
       } else {
         encoded[streamLenLB] += garbageLen;
         /* Write the length of the garbage at the end of the upper-band
          *  bit-stream, if exists. This helps for sanity check. */
@@ skipping 1645 matching lines @@
  *        - ISAC_main_inst    : iSAC instance
  *
  * Return value               : sampling rate in Hertz. Decoder output is
  *                              sampled at this rate.
  *
  */
 uint16_t WebRtcIsac_DecSampRate(ISACStruct* ISAC_main_inst) {
   ISACMainStruct* instISAC = (ISACMainStruct*)ISAC_main_inst;
   return instISAC->decoderSamplingRateKHz == kIsacWideband ? 16000 : 32000;
 }