RtpPacket class introduced.

webrtc/modules/rtp_rtcp/source/rtp_packet.cc

+/*
+ *  Copyright (c) 2016 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.
+ */
+
+#include "webrtc/modules/rtp_rtcp/source/rtp_packet.h"
+
+#include <cstring>
+
+#include "webrtc/base/checks.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/base/random.h"
+#include "webrtc/common_types.h"
+#include "webrtc/modules/rtp_rtcp/source/rtp_header_extension.h"
+#include "webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h"
+#include "webrtc/modules/rtp_rtcp/source/byte_io.h"
+
+namespace webrtc {
+namespace rtp {
+namespace {
+const size_t kFixedHeaderSize = 12;
+const uint8_t kRtpVersion = 2;
+const uint16_t kOneByteExtensionId = 0xBEDE;
+const size_t kDefaultPacketSize = 1500;
+}  // namespace
+//  0                   1                   2                   3
+//  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |V=2|P|X|  CC   |M|     PT      |       sequence number         |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                           timestamp                           |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |           synchronization source (SSRC) identifier            |
+// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+// |            Contributing source (CSRC) identifiers             |
+// |                             ....                              |
+// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+// |One-byte eXtensions id = 0xbede|       length in 32bits        |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |                          Extensions                           |
+// |                             ....                              |
+// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
+// |                           Payload                             |
+// |             ....              :  padding...                   |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+// |               padding         | Padding size  |
+// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+Packet::Packet(const ExtensionManager* extensions)
+    : extensions_(extensions), buffer_(kDefaultPacketSize) {
+  Clear();
+}
+
+Packet::Packet(const ExtensionManager* extensions, size_t capacity)
+    : extensions_(extensions), buffer_(capacity) {
+  RTC_DCHECK_GE(capacity, kFixedHeaderSize);
+  Clear();
+}
+
+Packet::~Packet() {}
+
+void Packet::SetExtensionManager(const ExtensionManager* extensions) {
+  RTC_DCHECK(extensions);
+  extensions_ = extensions;
+  for (size_t i = 0; i < num_extensions_; ++i) {
+    uint8_t id = data()[extension_entries_[i].offset - 1] >> 4;
+    extension_entries_[i].type = extensions_->GetType(id);
+  }
+}
+
+bool Packet::Parse(const uint8_t* buffer, size_t buffer_size) {
+  if (!ParseBuffer(buffer, buffer_size)) {
+    Clear();
+    return false;
+  }
+  RTC_DCHECK_EQ(size(), buffer_size);
+  buffer_.SetData(buffer, buffer_size);
+  return true;
+}
+
+bool Packet::Parse(rtc::Buffer buffer) {
+  if (!ParseBuffer(buffer.data(), buffer.size())) {
+    Clear();
+    return false;
+  }
+  RTC_DCHECK_EQ(size(), buffer.size());
+  buffer_ = std::move(buffer);
+  return true;
+}
+
+bool Packet::Marker() const {
+  RTC_DCHECK_EQ(marker_, (data()[1] & 0x80) != 0);
+  return marker_;
+}
+
+uint8_t Packet::PayloadType() const {
+  RTC_DCHECK_EQ(payload_type_, data()[1] & 0x7f);
+  return payload_type_;
+}
+
+uint16_t Packet::SequenceNumber() const {
+  RTC_DCHECK_EQ(sequence_number_,
+                ByteReader<uint16_t>::ReadBigEndian(data() + 2));
+  return sequence_number_;
+}
+
+uint32_t Packet::Timestamp() const {
+  RTC_DCHECK_EQ(sequence_number_,
+                ByteReader<uint32_t>::ReadBigEndian(data() + 4));
+  return timestamp_;
+}
+
+uint32_t Packet::Ssrc() const {
+  RTC_DCHECK_EQ(sequence_number_,
+                ByteReader<uint32_t>::ReadBigEndian(data() + 8));
+  return ssrc_;
+}
+
+std::vector<uint32_t> Packet::Csrcs() const {
+  size_t num_csrc = data()[0] & 0x0F;
+  RTC_DCHECK_GE(capacity(), kFixedHeaderSize + num_csrc * 4);
+  std::vector<uint32_t> csrcs(num_csrc);
+  for (size_t i = 0; i < num_csrc; ++i) {
+    csrcs[i] =
+        ByteReader<uint32_t>::ReadBigEndian(&data()[kFixedHeaderSize + i * 4]);
+  }
+  return csrcs;
+}
+
+void Packet::GetHeader(RTPHeader* header) const {
+  header->markerBit = Marker();
+  header->payloadType = PayloadType();
+  header->sequenceNumber = SequenceNumber();
+  header->timestamp = Timestamp();
+  header->ssrc = Ssrc();
+  std::vector<uint32_t> csrcs = Csrcs();
+  header->numCSRCs = csrcs.size();
+  for (size_t i = 0; i < csrcs.size(); ++i) {
+    header->arrOfCSRCs[i] = csrcs[i];
+  }
+  header->paddingLength = padding_size();
+  header->headerLength = headers_size();
+  header->payload_type_frequency = 0;
+  header->extension.hasTransmissionTimeOffset =
+      GetExtension<TransmissionOffset>(
+          &header->extension.transmissionTimeOffset);
+  header->extension.hasAbsoluteSendTime =
+      GetExtension<AbsoluteSendTime>(&header->extension.absoluteSendTime);
+  header->extension.hasTransportSequenceNumber =
+      GetExtension<TransportSequenceNumber>(
+          &header->extension.transportSequenceNumber);
+  header->extension.hasAudioLevel = GetExtension<AudioLevel>(
+      &header->extension.voiceActivity, &header->extension.audioLevel);
+  header->extension.hasVideoRotation =
+      GetExtension<VideoOrientation>(&header->extension.videoRotation);
+}
+
+size_t Packet::headers_size() const {
+  return payload_offset_;
+}
+
+size_t Packet::payload_size() const {
+  return payload_size_;
+}
+
+size_t Packet::padding_size() const {
+  return padding_size_;
+}
+
+const uint8_t* Packet::payload() const {
+  return data() + payload_offset_;
+}
+
+size_t Packet::capacity() const {
+  return buffer_.capacity();
+}
+
+size_t Packet::size() const {
+  return payload_offset_ + payload_size_ + padding_size_;
+}
+
+const uint8_t* Packet::data() const {
+  return buffer_.data();
+}
+
+size_t Packet::FreeCapacity() const {
+  return capacity() - size();
+}
+
+size_t Packet::MaxPayloadSize() const {
+  return capacity() - payload_offset_;
+}
+
+void Packet::CopyHeader(const Packet& packet) {
+  RTC_DCHECK_GE(capacity(), packet.headers_size());
+
+  marker_ = packet.marker_;
+  payload_type_ = packet.payload_type_;
+  sequence_number_ = packet.sequence_number_;
+  timestamp_ = packet.timestamp_;
+  ssrc_ = packet.ssrc_;
+  payload_offset_ = packet.payload_offset_;
+  num_extensions_ = packet.num_extensions_;
+  for (size_t i = 0; i < num_extensions_; ++i) {
+    extension_entries_[i] = packet.extension_entries_[i];
+  }
+  extensions_size_ = packet.extensions_size_;
+  buffer_.SetData(packet.data(), packet.headers_size());
+  // Reset payload and padding.
+  payload_size_ = 0;
+  padding_size_ = 0;
+}
+
+void Packet::SetMarker(bool marker_bit) {
+  marker_ = marker_bit;
+  if (marker_) {
+    WriteAt(1, data()[1] | 0x80);

[stefan-webrtc, 2016/04/14 13:00:29]

Would it make sense to instead have a Serialize function which can be called
once before we pass the packet to the network? I think the code might be cleaner
since it would isolate the serializing code into one function, instead of having
it split between all functions.

[sprang_webrtc, 2016/04/14 13:41:50]

I tried that once it quickly became difficult, especially with the way our code
currently works. We'd have to do a big-bang replacement to use this class
everywhere at once. By always writing through to the underlying buffer it's easy
to continue passing just the buffer around in places that haven't been updated
yet.

[danilchap, 2016/04/14 14:13:19]

Packet class is all about serializing/deserializing, it has no other features.

Introducing Serialize function would require to keep extension values in some
deserialized form, which is not trivial to make nice.
Neither is trivial to store payload and serialize it later without extra
memcopies.

+  } else {
+    WriteAt(1, data()[1] & 0x7F);
+  }
+}
+
+void Packet::SetPayloadType(uint8_t payload_type) {
+  RTC_DCHECK_LE(payload_type, 0x7Fu);
+  payload_type_ = payload_type;
+  WriteAt(1, (data()[1] & 0x80) | payload_type);
+}
+
+void Packet::SetSequenceNumber(uint16_t seq_no) {
+  sequence_number_ = seq_no;
+  ByteWriter<uint16_t>::WriteBigEndian(WriteAt(2), seq_no);
+}
+
+void Packet::SetTimestamp(uint32_t timestamp) {
+  timestamp_ = timestamp;
+  ByteWriter<uint32_t>::WriteBigEndian(WriteAt(4), timestamp);
+}
+
+void Packet::SetSsrc(uint32_t ssrc) {
+  ssrc_ = ssrc;
+  ByteWriter<uint32_t>::WriteBigEndian(WriteAt(8), ssrc);
+}
+
+void Packet::SetCsrcs(const std::vector<uint32_t>& csrcs) {
+  RTC_DCHECK_EQ(num_extensions_, 0u);
+  RTC_DCHECK_EQ(payload_size_, 0u);
+  RTC_DCHECK_EQ(padding_size_, 0u);
+  RTC_DCHECK_LE(csrcs.size(), 0x0fu);
+  RTC_DCHECK_LE(kFixedHeaderSize + 4 * csrcs.size(), capacity());
+  payload_offset_ = kFixedHeaderSize + 4 * csrcs.size();
+  WriteAt(0, (data()[0] & 0xF0) | csrcs.size());
+  size_t offset = kFixedHeaderSize;
+  for (uint32_t csrc : csrcs) {
+    ByteWriter<uint32_t>::WriteBigEndian(WriteAt(offset), csrc);
+    offset += 4;
+  }
+}
+
+uint8_t* Packet::AllocatePayload(size_t size_bytes) {
+  RTC_DCHECK_EQ(padding_size_, 0u);
+  if (payload_offset_ + size_bytes > capacity()) {
+    LOG(LS_WARNING) << "Cannot set payload, not enough space in buffer.";
+    return nullptr;
+  }
+  payload_size_ = size_bytes;
+  return WriteAt(payload_offset_);
+}
+
+void Packet::SetPayloadSize(size_t size_bytes) {
+  RTC_DCHECK_EQ(padding_size_, 0u);
+  RTC_DCHECK_LE(size_bytes, payload_size_);
+  payload_size_ = size_bytes;
+}
+
+bool Packet::SetPadding(uint8_t size_bytes, Random* random) {
+  RTC_DCHECK(random);
+  if (payload_offset_ + payload_size_ + size_bytes > capacity()) {
+    LOG(LS_WARNING) << "Cannot set padding size " << size_bytes << ", only "
+                    << (capacity() - payload_offset_ - payload_size_)
+                    << " bytes left in buffer.";
+    return false;
+  }
+  padding_size_ = size_bytes;
+  if (padding_size_ > 0) {
+    size_t padding_offset = payload_offset_ + payload_size_;
+    size_t padding_end = padding_offset + padding_size_;
+    for (size_t offset = padding_offset; offset < padding_end - 1; ++offset) {
+      WriteAt(offset, random->Rand<uint8_t>());
+    }
+    WriteAt(padding_end - 1, padding_size_);
+    WriteAt(0, data()[0] | 0x20);  // Set padding bit.
+  } else {
+    WriteAt(0, data()[0] & ~0x20);  // Clear padding bit.
+  }
+  return true;
+}
+
+void Packet::Clear() {
+  marker_ = false;
+  payload_type_ = 0;
+  sequence_number_ = 0;
+  timestamp_ = 0;
+  ssrc_ = 0;
+  payload_offset_ = kFixedHeaderSize;
+  payload_size_ = 0;
+  padding_size_ = 0;
+  num_extensions_ = 0;
+  extensions_size_ = 0;
+
+  memset(WriteAt(0), 0, kFixedHeaderSize);
+  WriteAt(0, kRtpVersion << 6);
+}
+
+bool Packet::ParseBuffer(const uint8_t* buffer, size_t size) {
+  if (size < kFixedHeaderSize) {
+    return false;
+  }
+  const uint8_t version = buffer[0] >> 6;
+  if (version != kRtpVersion) {
+    return false;
+  }
+  const bool has_padding = (buffer[0] & 0x20) != 0;
+  // eXtension

[sprang_webrtc, 2016/04/14 13:41:50]

remove comment

[danilchap, 2016/04/14 14:13:19]

Done.

+  const bool has_extension = (buffer[0] & 0x10) != 0;
+  const uint8_t number_of_crcs = buffer[0] & 0x0f;
+  marker_ = (buffer[1] & 0x80) != 0;
+  payload_type_ = buffer[1] & 0x7f;
+
+  sequence_number_ = ByteReader<uint16_t>::ReadBigEndian(&buffer[2]);
+  timestamp_ = ByteReader<uint32_t>::ReadBigEndian(&buffer[4]);
+  ssrc_ = ByteReader<uint32_t>::ReadBigEndian(&buffer[8]);
+  if (size < kFixedHeaderSize + number_of_crcs * 4) {
+    return false;
+  }
+  payload_offset_ = kFixedHeaderSize + number_of_crcs * 4;
+
+  if (has_padding) {
+    padding_size_ = buffer[size - 1];
+    if (padding_size_ == 0) {
+      LOG(LS_WARNING) << "Padding was set, but padding size is zero";
+      return false;
+    }
+  } else {
+    padding_size_ = 0;
+  }
+
+  num_extensions_ = 0;
+  extensions_size_ = 0;
+  if (has_extension) {
+    /* RTP header extension, RFC 3550.
+     0                   1                   2                   3
+     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |      defined by profile       |           length              |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |                        header extension                       |
+    |                             ....                              |
+    */
+    size_t extension_offset = payload_offset_ + 4;
+    if (extension_offset > size) {
+      return false;
+    }
+    uint16_t profile =
+        ByteReader<uint16_t>::ReadBigEndian(&buffer[payload_offset_]);
+    size_t extensions_capacity =
+        ByteReader<uint16_t>::ReadBigEndian(&buffer[payload_offset_ + 2]);
+    extensions_capacity *= 4;
+    if (extension_offset + extensions_capacity > size) {
+      return false;
+    }
+    if (profile == kOneByteExtensionId) {
+      const size_t kOneByteHeaderSize = 1;
+      const uint8_t kPaddingId = 0;
+      const uint8_t kReservedId = 15;
+      while (extensions_size_ + kOneByteHeaderSize < extensions_capacity) {
+        uint8_t id = buffer[extension_offset + extensions_size_] >> 4;
+        if (id == kReservedId) {
+          break;
+        } else if (id == kPaddingId) {
+          extensions_size_++;
+          continue;
+        }
+        uint8_t length =
+            1 + (buffer[extension_offset + extensions_size_] & 0xf);
+        extensions_size_ += kOneByteHeaderSize;
+        if (num_extensions_ >= kMaxExtensionHeaders)

[philipel, 2016/04/14 11:15:16]

{} :)

[sprang_webrtc, 2016/04/14 13:41:50]

Should we really silently ignore this?
maybe log warning and/or return false?

[danilchap, 2016/04/14 14:13:19]

Done: so many extensions means packet is invalid, returning false now.

+          break;
+        extension_entries_[num_extensions_].type =
+            extensions_ ? extensions_->GetType(id)
+                        : ExtensionManager::kInvalidType;
+        extension_entries_[num_extensions_].length = length;
+        extension_entries_[num_extensions_].offset =
+            extension_offset + extensions_size_;
+        num_extensions_++;
+        extensions_size_ += length;
+      }
+    }

[sprang_webrtc, 2016/04/14 13:41:50]

Log warning if profile isn't one byte extension header?

[danilchap, 2016/04/14 14:13:19]

Done.

+    payload_offset_ = extension_offset + extensions_capacity;
+  }
+
+  if (payload_offset_ + padding_size_ > size) {
+    return false;
+  }
+  payload_size_ = size - payload_offset_ - padding_size_;
+  return true;
+}
+
+bool Packet::FindExtension(ExtensionType type,
+                           uint8_t length,
+                           uint16_t* offset) const {
+  RTC_DCHECK(offset);
+  for (size_t i = 0; i < num_extensions_; ++i) {
+    if (extension_entries_[i].type == type) {
+      RTC_CHECK_EQ(length, extension_entries_[i].length)
+          << "Length mismatch for extension '" << type << "'"
+          << "should be " << length << ", received "
+          << extension_entries_[i].length;
+      *offset = extension_entries_[i].offset;
+      return true;
+    }
+  }
+  return false;
+}
+
+bool Packet::AllocateExtension(ExtensionType type,
+                               uint8_t length,
+                               uint16_t* offset) {
+  if (!extensions_) {
+    return false;
+  }
+  if (FindExtension(type, length, offset)) {
+    return true;
+  }
+
+  // Can't add new extension after payload/padding was set.
+  if (payload_size_ > 0) {
+    return false;
+  }
+  if (padding_size_ > 0) {
+    return false;
+  }
+
+  uint8_t extension_id = extensions_->GetId(type);
+  if (extension_id == ExtensionManager::kInvalidId) {
+    return false;
+  }
+  RTC_DCHECK_GT(length, 0u);
+  RTC_DCHECK_LE(length, 16u);
+
+  size_t num_csrc = data()[0] & 0x0F;
+  size_t extensions_offset = kFixedHeaderSize + (num_csrc * 4) + 4;
+  const uint8_t kExtensionHeaderSize = 1;  // Using one-byte extensions only.
+  if (extensions_offset + extensions_size_ + kExtensionHeaderSize + length >
+      capacity()) {
+    LOG(LS_WARNING) << "Extension cannot be registered: "
+                       "Not enough space left in buffer.";
+    return false;
+  }
+
+  uint16_t new_extensions_size =
+      extensions_size_ + kExtensionHeaderSize + length;
+  uint16_t extensions_words =
+      (new_extensions_size + 3) / 4;  // Wrap up to 32bit.
+  if (extensions_words > 0xFFFF) {
+    LOG(LS_WARNING) << "Too much extension header data, exceeds 2^16 DWORDS.";
+    return false;
+  }
+
+  // All checks passed, write down the extension.
+  if (num_extensions_ == 0) {
+    RTC_DCHECK_EQ(payload_offset_, kFixedHeaderSize + (num_csrc * 4));
+    RTC_DCHECK_EQ(extensions_size_, 0);
+    WriteAt(0, data()[0] | 0x10);  // Set extension bit.
+    // Profile specific ID always set to OneByteExtensionHeader.
+    ByteWriter<uint16_t>::WriteBigEndian(WriteAt(extensions_offset - 4),
+                                         kOneByteExtensionId);
+  }
+
+  WriteAt(extensions_offset + extensions_size_,
+          (extension_id << 4) | (length - 1));
+  RTC_DCHECK_LT(num_extensions_, kMaxExtensionHeaders);
+  extension_entries_[num_extensions_].type = type;
+  extension_entries_[num_extensions_].length = length;
+  *offset = extensions_offset + kExtensionHeaderSize + extensions_size_;
+  extension_entries_[num_extensions_].offset = *offset;
+  ++num_extensions_;
+  extensions_size_ = new_extensions_size;
+
+  // Update header length field.
+  ByteWriter<uint16_t>::WriteBigEndian(WriteAt(extensions_offset - 2),
+                                       extensions_words);
+  // Fill extension padding place with zeroes.
+  size_t extension_padding_size = 4 * extensions_words - extensions_size_;
+  memset(WriteAt(extensions_offset + extensions_size_), 0,
+         extension_padding_size);
+  payload_offset_ = extensions_offset + 4 * extensions_words;
+  return true;
+}
+
+uint8_t* Packet::WriteAt(size_t offset) {
+  return buffer_.data() + offset;
+}
+
+void Packet::WriteAt(size_t offset, uint8_t byte) {
+  buffer_.data()[offset] = byte;
+}
+
+}  // namespace rtp
+}  // namespace webrtc