Moving src/webrtc into src/.

In order to eliminate the WebRTC Subtree mirror in Chromium, 
WebRTC is moving the content of the src/webrtc directory up
to the src/ directory.

NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
TBR=tommi@webrtc.org

Bug: chromium:611808
Change-Id: Iac59c5b51b950f174119565bac87955a7994bc38
Reviewed-on: https://webrtc-review.googlesource.com/1560
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#19845}

rtc_base/bitbuffer.cc

@@ -0,0 +1,310 @@
+/*
+ *  Copyright 2015 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/rtc_base/bitbuffer.h"
+
+#include <algorithm>
+#include <limits>
+
+#include "webrtc/rtc_base/checks.h"
+
+namespace {
+
+// Returns the lowest (right-most) |bit_count| bits in |byte|.
+uint8_t LowestBits(uint8_t byte, size_t bit_count) {
+  RTC_DCHECK_LE(bit_count, 8);
+  return byte & ((1 << bit_count) - 1);
+}
+
+// Returns the highest (left-most) |bit_count| bits in |byte|, shifted to the
+// lowest bits (to the right).
+uint8_t HighestBits(uint8_t byte, size_t bit_count) {
+  RTC_DCHECK_LE(bit_count, 8);
+  uint8_t shift = 8 - static_cast<uint8_t>(bit_count);
+  uint8_t mask = 0xFF << shift;
+  return (byte & mask) >> shift;
+}
+
+// Returns the highest byte of |val| in a uint8_t.
+uint8_t HighestByte(uint64_t val) {
+  return static_cast<uint8_t>(val >> 56);
+}
+
+// Returns the result of writing partial data from |source|, of
+// |source_bit_count| size in the highest bits, to |target| at
+// |target_bit_offset| from the highest bit.
+uint8_t WritePartialByte(uint8_t source,
+                         size_t source_bit_count,
+                         uint8_t target,
+                         size_t target_bit_offset) {
+  RTC_DCHECK(target_bit_offset < 8);
+  RTC_DCHECK(source_bit_count < 9);
+  RTC_DCHECK(source_bit_count <= (8 - target_bit_offset));
+  // Generate a mask for just the bits we're going to overwrite, so:
+  uint8_t mask =
+      // The number of bits we want, in the most significant bits...
+      static_cast<uint8_t>(0xFF << (8 - source_bit_count))
+      // ...shifted over to the target offset from the most signficant bit.
+      >> target_bit_offset;
+
+  // We want the target, with the bits we'll overwrite masked off, or'ed with
+  // the bits from the source we want.
+  return (target & ~mask) | (source >> target_bit_offset);
+}
+
+// Counts the number of bits used in the binary representation of val.
+size_t CountBits(uint64_t val) {
+  size_t bit_count = 0;
+  while (val != 0) {
+    bit_count++;
+    val >>= 1;
+  }
+  return bit_count;
+}
+
+}  // namespace
+
+namespace rtc {
+
+BitBuffer::BitBuffer(const uint8_t* bytes, size_t byte_count)
+    : bytes_(bytes), byte_count_(byte_count), byte_offset_(), bit_offset_() {
+  RTC_DCHECK(static_cast<uint64_t>(byte_count_) <=
+             std::numeric_limits<uint32_t>::max());
+}
+
+uint64_t BitBuffer::RemainingBitCount() const {
+  return (static_cast<uint64_t>(byte_count_) - byte_offset_) * 8 - bit_offset_;
+}
+
+bool BitBuffer::ReadUInt8(uint8_t* val) {
+  uint32_t bit_val;
+  if (!ReadBits(&bit_val, sizeof(uint8_t) * 8)) {
+    return false;
+  }
+  RTC_DCHECK(bit_val <= std::numeric_limits<uint8_t>::max());
+  *val = static_cast<uint8_t>(bit_val);
+  return true;
+}
+
+bool BitBuffer::ReadUInt16(uint16_t* val) {
+  uint32_t bit_val;
+  if (!ReadBits(&bit_val, sizeof(uint16_t) * 8)) {
+    return false;
+  }
+  RTC_DCHECK(bit_val <= std::numeric_limits<uint16_t>::max());
+  *val = static_cast<uint16_t>(bit_val);
+  return true;
+}
+
+bool BitBuffer::ReadUInt32(uint32_t* val) {
+  return ReadBits(val, sizeof(uint32_t) * 8);
+}
+
+bool BitBuffer::PeekBits(uint32_t* val, size_t bit_count) {
+  if (!val || bit_count > RemainingBitCount() || bit_count > 32) {
+    return false;
+  }
+  const uint8_t* bytes = bytes_ + byte_offset_;
+  size_t remaining_bits_in_current_byte = 8 - bit_offset_;
+  uint32_t bits = LowestBits(*bytes++, remaining_bits_in_current_byte);
+  // If we're reading fewer bits than what's left in the current byte, just
+  // return the portion of this byte that we need.
+  if (bit_count < remaining_bits_in_current_byte) {
+    *val = HighestBits(bits, bit_offset_ + bit_count);
+    return true;
+  }
+  // Otherwise, subtract what we've read from the bit count and read as many
+  // full bytes as we can into bits.
+  bit_count -= remaining_bits_in_current_byte;
+  while (bit_count >= 8) {
+    bits = (bits << 8) | *bytes++;
+    bit_count -= 8;
+  }
+  // Whatever we have left is smaller than a byte, so grab just the bits we need
+  // and shift them into the lowest bits.
+  if (bit_count > 0) {
+    bits <<= bit_count;
+    bits |= HighestBits(*bytes, bit_count);
+  }
+  *val = bits;
+  return true;
+}
+
+bool BitBuffer::ReadBits(uint32_t* val, size_t bit_count) {
+  return PeekBits(val, bit_count) && ConsumeBits(bit_count);
+}
+
+bool BitBuffer::ConsumeBytes(size_t byte_count) {
+  return ConsumeBits(byte_count * 8);
+}
+
+bool BitBuffer::ConsumeBits(size_t bit_count) {
+  if (bit_count > RemainingBitCount()) {
+    return false;
+  }
+
+  byte_offset_ += (bit_offset_ + bit_count) / 8;
+  bit_offset_ = (bit_offset_ + bit_count) % 8;
+  return true;
+}
+
+bool BitBuffer::ReadExponentialGolomb(uint32_t* val) {
+  if (!val) {
+    return false;
+  }
+  // Store off the current byte/bit offset, in case we want to restore them due
+  // to a failed parse.
+  size_t original_byte_offset = byte_offset_;
+  size_t original_bit_offset = bit_offset_;
+
+  // Count the number of leading 0 bits by peeking/consuming them one at a time.
+  size_t zero_bit_count = 0;
+  uint32_t peeked_bit;
+  while (PeekBits(&peeked_bit, 1) && peeked_bit == 0) {
+    zero_bit_count++;
+    ConsumeBits(1);
+  }
+
+  // We should either be at the end of the stream, or the next bit should be 1.
+  RTC_DCHECK(!PeekBits(&peeked_bit, 1) || peeked_bit == 1);
+
+  // The bit count of the value is the number of zeros + 1. Make sure that many
+  // bits fits in a uint32_t and that we have enough bits left for it, and then
+  // read the value.
+  size_t value_bit_count = zero_bit_count + 1;
+  if (value_bit_count > 32 || !ReadBits(val, value_bit_count)) {
+    RTC_CHECK(Seek(original_byte_offset, original_bit_offset));
+    return false;
+  }
+  *val -= 1;
+  return true;
+}
+
+bool BitBuffer::ReadSignedExponentialGolomb(int32_t* val) {
+  uint32_t unsigned_val;
+  if (!ReadExponentialGolomb(&unsigned_val)) {
+    return false;
+  }
+  if ((unsigned_val & 1) == 0) {
+    *val = -static_cast<int32_t>(unsigned_val / 2);
+  } else {
+    *val = (unsigned_val + 1) / 2;
+  }
+  return true;
+}
+
+void BitBuffer::GetCurrentOffset(
+    size_t* out_byte_offset, size_t* out_bit_offset) {
+  RTC_CHECK(out_byte_offset != nullptr);
+  RTC_CHECK(out_bit_offset != nullptr);
+  *out_byte_offset = byte_offset_;
+  *out_bit_offset = bit_offset_;
+}
+
+bool BitBuffer::Seek(size_t byte_offset, size_t bit_offset) {
+  if (byte_offset > byte_count_ || bit_offset > 7 ||
+      (byte_offset == byte_count_ && bit_offset > 0)) {
+    return false;
+  }
+  byte_offset_ = byte_offset;
+  bit_offset_ = bit_offset;
+  return true;
+}
+
+BitBufferWriter::BitBufferWriter(uint8_t* bytes, size_t byte_count)
+    : BitBuffer(bytes, byte_count), writable_bytes_(bytes) {
+}
+
+bool BitBufferWriter::WriteUInt8(uint8_t val) {
+  return WriteBits(val, sizeof(uint8_t) * 8);
+}
+
+bool BitBufferWriter::WriteUInt16(uint16_t val) {
+  return WriteBits(val, sizeof(uint16_t) * 8);
+}
+
+bool BitBufferWriter::WriteUInt32(uint32_t val) {
+  return WriteBits(val, sizeof(uint32_t) * 8);
+}
+
+bool BitBufferWriter::WriteBits(uint64_t val, size_t bit_count) {
+  if (bit_count > RemainingBitCount()) {
+    return false;
+  }
+  size_t total_bits = bit_count;
+
+  // For simplicity, push the bits we want to read from val to the highest bits.
+  val <<= (sizeof(uint64_t) * 8 - bit_count);
+
+  uint8_t* bytes = writable_bytes_ + byte_offset_;
+
+  // The first byte is relatively special; the bit offset to write to may put us
+  // in the middle of the byte, and the total bit count to write may require we
+  // save the bits at the end of the byte.
+  size_t remaining_bits_in_current_byte = 8 - bit_offset_;
+  size_t bits_in_first_byte =
+      std::min(bit_count, remaining_bits_in_current_byte);
+  *bytes = WritePartialByte(
+      HighestByte(val), bits_in_first_byte, *bytes, bit_offset_);
+  if (bit_count <= remaining_bits_in_current_byte) {
+    // Nothing left to write, so quit early.
+    return ConsumeBits(total_bits);
+  }
+
+  // Subtract what we've written from the bit count, shift it off the value, and
+  // write the remaining full bytes.
+  val <<= bits_in_first_byte;
+  bytes++;
+  bit_count -= bits_in_first_byte;
+  while (bit_count >= 8) {
+    *bytes++ = HighestByte(val);
+    val <<= 8;
+    bit_count -= 8;
+  }
+
+  // Last byte may also be partial, so write the remaining bits from the top of
+  // val.
+  if (bit_count > 0) {
+    *bytes = WritePartialByte(HighestByte(val), bit_count, *bytes, 0);
+  }
+
+  // All done! Consume the bits we've written.
+  return ConsumeBits(total_bits);
+}
+
+bool BitBufferWriter::WriteExponentialGolomb(uint32_t val) {
+  // We don't support reading UINT32_MAX, because it doesn't fit in a uint32_t
+  // when encoded, so don't support writing it either.
+  if (val == std::numeric_limits<uint32_t>::max()) {
+    return false;
+  }
+  uint64_t val_to_encode = static_cast<uint64_t>(val) + 1;
+
+  // We need to write CountBits(val+1) 0s and then val+1. Since val (as a
+  // uint64_t) has leading zeros, we can just write the total golomb encoded
+  // size worth of bits, knowing the value will appear last.
+  return WriteBits(val_to_encode, CountBits(val_to_encode) * 2 - 1);
+}
+
+bool BitBufferWriter::WriteSignedExponentialGolomb(int32_t val) {
+  if (val == 0) {
+    return WriteExponentialGolomb(0);
+  } else if (val > 0) {
+    uint32_t signed_val = val;
+    return WriteExponentialGolomb((signed_val * 2) - 1);
+  } else {
+    if (val == std::numeric_limits<int32_t>::min())
+      return false;  // Not supported, would cause overflow.
+    uint32_t signed_val = -val;
+    return WriteExponentialGolomb(signed_val * 2);
+  }
+}
+
+}  // namespace rtc