Adding the ability to create an RtpSender without a track.

webrtc/base/helpers.cc

 /*
  *  Copyright 2004 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 146 matching lines @@
     return true;
   }
 
  private:
   int GetRandom() {
     return ((seed_ = seed_ * 214013L + 2531011L) >> 16) & 0x7fff;
   }
   int seed_;
 };
 
-// TODO: Use Base64::Base64Table instead.
-static const char BASE64[64] = {
-  'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
-  'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
-  'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
-  'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
-  '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'
-};
-
 namespace {
 
+// TODO: Use Base64::Base64Table instead.
+static const char kBase64[64] = {
+    'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
+    'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
+    'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
+    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
+    '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'};
+
+static const char kHex[16] = {'0', '1', '2', '3', '4', '5', '6', '7',
+                              '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
 // This round about way of creating a global RNG is to safe-guard against
 // indeterminant static initialization order.
 scoped_ptr<RandomGenerator>& GetGlobalRng() {
   RTC_DEFINE_STATIC_LOCAL(scoped_ptr<RandomGenerator>, global_rng,
                           (new SecureRandomGenerator()));
   return global_rng;
 }
 
 RandomGenerator& Rng() {
   return *GetGlobalRng();
@@ skipping 37 matching lines @@
     return false;
   }
   str->reserve(len);
   for (size_t i = 0; i < len; ++i) {
     str->push_back(table[bytes[i] % table_size]);
   }
   return true;
 }
 
 bool CreateRandomString(size_t len, std::string* str) {
-  return CreateRandomString(len, BASE64, 64, str);
+  return CreateRandomString(len, kBase64, 64, str);
 }
 
 bool CreateRandomString(size_t len, const std::string& table,
                         std::string* str) {
   return CreateRandomString(len, table.c_str(),
                             static_cast<int>(table.size()), str);
 }
 
+// Version 4 UUID is of the form:
+// xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx
+// Where 'x' is a hex digit, and 'y' is 8, 9, a or b.
+std::string CreateRandomUuid() {
+  std::string str;
+  scoped_ptr<uint8_t[]> bytes(new uint8_t[31]);
+  if (!Rng().Generate(bytes.get(), 31)) {
+    LOG(LS_ERROR) << "Failed to generate random string!";
+    return str;
+  }
+  str.reserve(36);
+  for (size_t i = 0; i < 8; ++i) {
+    str.push_back(kHex[bytes[i] % 16]);
+  }
+  str.push_back('-');
+  for (size_t i = 8; i < 12; ++i) {
+    str.push_back(kHex[bytes[i] % 16]);
+  }
+  str.push_back('-');
+  str.push_back('4');
+  for (size_t i = 12; i < 15; ++i) {
+    str.push_back(kHex[bytes[i] % 16]);
+  }
+  str.push_back('-');
+  str.push_back(kHex[((bytes[15] & ~0x4) | 0x8) % 16]);

[pthatcher1, 2015/10/20 17:42:50]

Could you make a table with 8, 9, a, and b and then use kFoo[bytes[i] & 4]? 
That would be a bit more readable.

[Taylor Brandstetter, 2015/10/21 00:22:09]

Done.

+  for (size_t i = 16; i < 19; ++i) {
+    str.push_back(kHex[bytes[i] % 16]);
+  }
+  str.push_back('-');
+  for (size_t i = 19; i < 31; ++i) {
+    str.push_back(kHex[bytes[i] % 16]);
+  }
+  return str;
+}
+
 uint32_t CreateRandomId() {
   uint32_t id;
   if (!Rng().Generate(&id, sizeof(id))) {
     LOG(LS_ERROR) << "Failed to generate random id!";
   }
   return id;
 }
 
 uint64_t CreateRandomId64() {
   return static_cast<uint64_t>(CreateRandomId()) << 32 | CreateRandomId();
 }
 
 uint32_t CreateRandomNonZeroId() {
   uint32_t id;
   do {
     id = CreateRandomId();
   } while (id == 0);
   return id;
 }
 
 double CreateRandomDouble() {
   return CreateRandomId() / (std::numeric_limits<uint32_t>::max() +
                              std::numeric_limits<double>::epsilon());
 }
 
 }  // namespace rtc