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diff --git a/third_party/libwebrtc/rtc_base/byte_buffer.h b/third_party/libwebrtc/rtc_base/byte_buffer.h
new file mode 100644
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+++ b/third_party/libwebrtc/rtc_base/byte_buffer.h
@@ -0,0 +1,173 @@
+/*
+ *  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.
+ */
+
+#ifndef RTC_BASE_BYTE_BUFFER_H_
+#define RTC_BASE_BYTE_BUFFER_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <string>
+
+#include "absl/strings/string_view.h"
+#include "rtc_base/buffer.h"
+#include "rtc_base/byte_order.h"
+
+// Reads/Writes from/to buffer using network byte order (big endian)
+namespace rtc {
+
+template <class BufferClassT>
+class ByteBufferWriterT {
+ public:
+  ByteBufferWriterT() { Construct(nullptr, kDefaultCapacity); }
+  ByteBufferWriterT(const char* bytes, size_t len) { Construct(bytes, len); }
+
+  ByteBufferWriterT(const ByteBufferWriterT&) = delete;
+  ByteBufferWriterT& operator=(const ByteBufferWriterT&) = delete;
+
+  const char* Data() const { return buffer_.data(); }
+  size_t Length() const { return buffer_.size(); }
+  size_t Capacity() const { return buffer_.capacity(); }
+
+  // Write value to the buffer. Resizes the buffer when it is
+  // neccessary.
+  void WriteUInt8(uint8_t val) {
+    WriteBytes(reinterpret_cast<const char*>(&val), 1);
+  }
+  void WriteUInt16(uint16_t val) {
+    uint16_t v = HostToNetwork16(val);
+    WriteBytes(reinterpret_cast<const char*>(&v), 2);
+  }
+  void WriteUInt24(uint32_t val) {
+    uint32_t v = HostToNetwork32(val);
+    char* start = reinterpret_cast<char*>(&v);
+    ++start;
+    WriteBytes(start, 3);
+  }
+  void WriteUInt32(uint32_t val) {
+    uint32_t v = HostToNetwork32(val);
+    WriteBytes(reinterpret_cast<const char*>(&v), 4);
+  }
+  void WriteUInt64(uint64_t val) {
+    uint64_t v = HostToNetwork64(val);
+    WriteBytes(reinterpret_cast<const char*>(&v), 8);
+  }
+  // Serializes an unsigned varint in the format described by
+  // https://developers.google.com/protocol-buffers/docs/encoding#varints
+  // with the caveat that integers are 64-bit, not 128-bit.
+  void WriteUVarint(uint64_t val) {
+    while (val >= 0x80) {
+      // Write 7 bits at a time, then set the msb to a continuation byte
+      // (msb=1).
+      char byte = static_cast<char>(val) | 0x80;
+      WriteBytes(&byte, 1);
+      val >>= 7;
+    }
+    char last_byte = static_cast<char>(val);
+    WriteBytes(&last_byte, 1);
+  }
+  void WriteString(absl::string_view val) {
+    WriteBytes(val.data(), val.size());
+  }
+  void WriteBytes(const char* val, size_t len) { buffer_.AppendData(val, len); }
+
+  // Reserves the given number of bytes and returns a char* that can be written
+  // into. Useful for functions that require a char* buffer and not a
+  // ByteBufferWriter.
+  char* ReserveWriteBuffer(size_t len) {
+    buffer_.SetSize(buffer_.size() + len);
+    return buffer_.data();
+  }
+
+  // Resize the buffer to the specified `size`.
+  void Resize(size_t size) { buffer_.SetSize(size); }
+
+  // Clears the contents of the buffer. After this, Length() will be 0.
+  void Clear() { buffer_.Clear(); }
+
+ private:
+  static constexpr size_t kDefaultCapacity = 4096;
+
+  void Construct(const char* bytes, size_t size) {
+    if (bytes) {
+      buffer_.AppendData(bytes, size);
+    } else {
+      buffer_.EnsureCapacity(size);
+    }
+  }
+
+  BufferClassT buffer_;
+
+  // There are sensible ways to define these, but they aren't needed in our code
+  // base.
+};
+
+class ByteBufferWriter : public ByteBufferWriterT<BufferT<char>> {
+ public:
+  ByteBufferWriter();
+  ByteBufferWriter(const char* bytes, size_t len);
+
+  ByteBufferWriter(const ByteBufferWriter&) = delete;
+  ByteBufferWriter& operator=(const ByteBufferWriter&) = delete;
+};
+
+// The ByteBufferReader references the passed data, i.e. the pointer must be
+// valid during the lifetime of the reader.
+class ByteBufferReader {
+ public:
+  ByteBufferReader(const char* bytes, size_t len);
+
+  // Initializes buffer from a zero-terminated string.
+  explicit ByteBufferReader(const char* bytes);
+
+  explicit ByteBufferReader(const Buffer& buf);
+
+  explicit ByteBufferReader(const ByteBufferWriter& buf);
+
+  ByteBufferReader(const ByteBufferReader&) = delete;
+  ByteBufferReader& operator=(const ByteBufferReader&) = delete;
+
+  // Returns start of unprocessed data.
+  const char* Data() const { return bytes_ + start_; }
+  // Returns number of unprocessed bytes.
+  size_t Length() const { return end_ - start_; }
+
+  // Read a next value from the buffer. Return false if there isn't
+  // enough data left for the specified type.
+  bool ReadUInt8(uint8_t* val);
+  bool ReadUInt16(uint16_t* val);
+  bool ReadUInt24(uint32_t* val);
+  bool ReadUInt32(uint32_t* val);
+  bool ReadUInt64(uint64_t* val);
+  bool ReadUVarint(uint64_t* val);
+  bool ReadBytes(char* val, size_t len);
+
+  // Appends next `len` bytes from the buffer to `val`. Returns false
+  // if there is less than `len` bytes left.
+  bool ReadString(std::string* val, size_t len);
+
+  // Moves current position `size` bytes forward. Returns false if
+  // there is less than `size` bytes left in the buffer. Consume doesn't
+  // permanently remove data, so remembered read positions are still valid
+  // after this call.
+  bool Consume(size_t size);
+
+ protected:
+  void Construct(const char* bytes, size_t size);
+
+  const char* bytes_;
+  size_t size_;
+  size_t start_;
+  size_t end_;
+};
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_BYTE_BUFFER_H_