Certificate Transparency: Code for unpacking EV cert hashes whitelist

chrome/browser/net/bit_stream_reader.cc

Index: chrome/browser/net/bit_stream_reader.cc
diff --git a/chrome/browser/net/bit_stream_reader.cc b/chrome/browser/net/bit_stream_reader.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9e9f0aaf8d2eccc144be12f8eafa04acbf04d7d6
--- /dev/null
+++ b/chrome/browser/net/bit_stream_reader.cc
@@ -0,0 +1,63 @@
+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/net/bit_stream_reader.h"
+
+#include "base/big_endian.h"
+#include "base/logging.h"
+#include "base/numerics/safe_conversions.h"
+
+namespace internal {
+
+BitStreamReader::BitStreamReader(const base::StringPiece& source)
+    : source_(source), current_byte_(0), current_bit_(7) {
+  DCHECK_LT(source_.length(), UINT32_MAX);
+}
+
+bool BitStreamReader::ReadUnaryEncoding(uint64_t* out) {
+  if (BitsLeft() == 0)
+    return false;
+
+  *out = 0;
+  while ((BitsLeft() > 0) && ReadBit())
+    ++(*out);
+
+  return true;
+}
+
+bool BitStreamReader::ReadBits(uint8_t num_bits, uint64_t* out) {
+  DCHECK_LE(num_bits, 64);
+
+  if (BitsLeft() < num_bits)
+    return false;
+
+  *out = 0;
+  for (uint8_t i = 0; i < num_bits; ++i)
+    (*out) |= (static_cast<uint64_t>(ReadBit()) << (num_bits - (i + 1)));
+
+  return true;
+}
+
+uint64_t BitStreamReader::BitsLeft() const {
+  if (current_byte_ == source_.length())
+    return 0;
+  DCHECK_GT(source_.length(), current_byte_);
+  return (source_.length() - (current_byte_ + 1)) * 8 + current_bit_ + 1;
+}
+
+uint8_t BitStreamReader::ReadBit() {
+  DCHECK_GT(BitsLeft(), 0u);
+  DCHECK(current_bit_ < 8 && current_bit_ >= 0);
+  uint8_t res =
+      (source_.data()[current_byte_] & (1 << current_bit_)) >> current_bit_;
+  current_bit_--;
+  if (current_bit_ < 0) {
+    current_byte_++;
+    current_bit_ = 7;
+  }
+
+  return res;
+}
+
+}  // namespace internal