RentACodec: New class that takes over part of ACMCodecDB's job

webrtc/modules/audio_coding/main/acm2/acm_codec_database.cc

 /*
  *  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 205 matching lines @@
     , kDecoderAVT
 #ifdef WEBRTC_CODEC_RED
     , kDecoderRED
 #endif
 };
 
 // Get codec information from database.
 // TODO(tlegrand): replace memcpy with a pointer to the data base memory.
 int ACMCodecDB::Codec(int codec_id, CodecInst* codec_inst) {
   // Error check to see that codec_id is not out of bounds.
-  if ((codec_id < 0) || (codec_id >= kNumCodecs)) {
+  if (static_cast<size_t>(codec_id) >= RentACodec::NumberOfCodecs()) {
     return -1;
   }
 
   // Copy database information for the codec to the output.
   memcpy(codec_inst, &database_[codec_id], sizeof(CodecInst));
 
   return 0;
 }
 
 // Enumerator for error codes when asking for codec database id.
@@ skipping 74 matching lines @@
 // codec list. Need to check all three since some codecs have several codec
 // entries with different frequencies and/or channels.
 // Does not check other codec settings, such as payload type and packet size.
 // Returns the id of the codec, or -1 if no match is found.
 int ACMCodecDB::CodecId(const CodecInst& codec_inst) {
   return (CodecId(codec_inst.plname, codec_inst.plfreq,
                   codec_inst.channels));
 }
 
 int ACMCodecDB::CodecId(const char* payload_name, int frequency, int channels) {
-  for (int id = 0; id < kNumCodecs; id++) {
+  for (const CodecInst& ci : RentACodec::Database()) {
     bool name_match = false;
     bool frequency_match = false;
     bool channels_match = false;
 
     // Payload name, sampling frequency and number of channels need to match.
     // NOTE! If |frequency| is -1, the frequency is not applicable, and is
     // always treated as true, like for RED.
-    name_match = (STR_CASE_CMP(database_[id].plname, payload_name) == 0);
-    frequency_match = (frequency == database_[id].plfreq) || (frequency == -1);
+    name_match = (STR_CASE_CMP(ci.plname, payload_name) == 0);
+    frequency_match = (frequency == ci.plfreq) || (frequency == -1);
     // The number of channels must match for all codecs but Opus.
     if (STR_CASE_CMP(payload_name, "opus") != 0) {
-      channels_match = (channels == database_[id].channels);
+      channels_match = (channels == ci.channels);
     } else {
       // For opus we just check that number of channels is valid.
       channels_match = (channels == 1 || channels == 2);
     }
 
     if (name_match && frequency_match && channels_match) {
       // We have found a matching codec in the list.
-      return id;
+      return &ci - RentACodec::Database().data();
     }
   }
 
   // We didn't find a matching codec.
   return -1;
 }
 // Gets codec id number from database for the receiver.
 int ACMCodecDB::ReceiverCodecNumber(const CodecInst& codec_inst) {
   // Look for a matching codec in the database.
   return CodecId(codec_inst);
 }
 
 // Returns the codec sampling frequency for codec with id = "codec_id" in
 // database.
 int ACMCodecDB::CodecFreq(int codec_id) {

[the sun, 2015/10/27 11:56:43]

const?

[kwiberg-webrtc, 2015/10/27 12:16:46]

Where?

[the sun, 2015/10/27 12:27:40]

On the method

[kwiberg-webrtc, 2015/10/27 12:33:17]

It's static.

-  // Error check to see that codec_id is not out of bounds.
-  if (codec_id < 0 || codec_id >= kNumCodecs) {
-    return -1;
-  }
-
-  return database_[codec_id].plfreq;
+  const size_t i = static_cast<size_t>(codec_id);
+  auto db = RentACodec::Database();

[the sun, 2015/10/27 11:56:43]

const auto?

[kwiberg-webrtc, 2015/10/27 12:16:46]

Sure, it might be worth it even though it's easy to see that we don't assign to
db below. (Assignment to db is the only thing const protects against; mutation
of the pointed-to array is regulated by the ArrayView's element type.)

[the sun, 2015/10/27 12:27:40]

Good. Thing is though, when I read this I don't see that the type is ArrayView.
std::vector would be a more common assumption when reading C++.

[kwiberg-webrtc, 2015/10/27 12:33:17]

Ah, good point.

+  return i < db.size() ? db[i].plfreq : -1;
 }
 
 // Checks if the payload type is in the valid range.
 bool ACMCodecDB::ValidPayloadType(int payload_type) {
   return (payload_type >= 0) && (payload_type <= 127);
 }
 
 }  // namespace acm2
 
 }  // namespace webrtc