Add static domain security state generator tool.

net/tools/domain_security_preload_generator/trie/trie_bit_buffer.cc

+// Copyright (c) 2016 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 "net/tools/domain_security_preload_generator/trie/trie_bit_buffer.h"
+
+#include "base/logging.h"
+#include "net/tools/domain_security_preload_generator/bit_writer.h"
+
+namespace net {
+
+namespace transport_security_state {
+
+TrieBitBuffer::TrieBitBuffer() {}
+
+TrieBitBuffer::~TrieBitBuffer() {}
+
+void TrieBitBuffer::WriteBit(uint8_t bit) {
+  current_byte_ |= bit << (7 - used_);
+  used_++;
+
+  if (used_ == 8) {
+    Flush();
+  }
+}
+
+void TrieBitBuffer::WriteBits(uint32_t bits, uint8_t number_of_bits) {
+  DCHECK(number_of_bits <= 32);
+  for (uint8_t i = 1; i <= number_of_bits; i++) {
+    uint8_t bit = 1 & (bits >> (number_of_bits - i));
+    WriteBit(bit);
+  }
+}
+
+void TrieBitBuffer::WritePosition(uint32_t position, int32_t* last_position) {
+  if (*last_position != -1) {
+    int32_t delta = position - *last_position;
+    DCHECK(delta > 0) << "delta position is not positive.";
+
+    uint8_t number_of_bits = BitLength(delta);
+    DCHECK(number_of_bits <= 7 + 15) << "positive position delta too large.";
+
+    if (number_of_bits <= 7) {
+      WriteBits(0, 1);
+      WriteBits(delta, 7);
+    } else {
+      WriteBits(1, 1);
+      WriteBits(number_of_bits - 8, 4);
+      WriteBits(delta, number_of_bits);
+    }
+
+    *last_position = position;
+    return;
+  }
+
+  if (used_ != 0) {
+    Flush();
+  }
+
+  AppendPositionElement(position);
+
+  *last_position = position;
+}
+
+uint8_t TrieBitBuffer::BitLength(uint32_t input) const {
+  uint8_t number_of_bits = 0;
+  while (input != 0) {
+    number_of_bits++;
+    input >>= 1;
+  }
+  return number_of_bits;
+}
+
+void TrieBitBuffer::WriteChar(uint8_t byte,
+                              const HuffmanRepresentationTable& table,
+                              HuffmanFrequencyTracker* tracker) {
+  HuffmanRepresentationTable::const_iterator item;
+  item = table.find(byte);
+  DCHECK(item != table.end());
+  if (tracker) {
+    tracker->RecordUsage(byte);
+  }
+  WriteBits(item->second.bits, item->second.number_of_bits);
+}
+
+void TrieBitBuffer::AppendBitsElement(uint8_t bits, uint8_t number_of_bits) {
+  BitsOrPosition element;
+  element.bits = current_byte_;
+  element.number_of_bits = used_;
+  elements_.push_back(element);
+}
+
+void TrieBitBuffer::AppendPositionElement(uint32_t position) {
+  BitsOrPosition element;
+  element.position = position;
+  element.number_of_bits = 0;
+  elements_.push_back(element);
+}
+
+uint32_t TrieBitBuffer::WriteToBitWriter(BitWriter* writer) {
+  Flush();
+
+  uint32_t old_position = writer->position();
+  for (auto const& element : elements_) {
+    if (element.number_of_bits) {
+      writer->WriteBits(element.bits >> (8 - element.number_of_bits),
+                        element.number_of_bits);
+    } else {
+      uint32_t current = old_position;
+      uint32_t target = element.position;
+      DCHECK(target < current) << "Reference is not backwards";
+      uint32_t delta = current - target;
+      uint8_t delta_number_of_bits = BitLength(delta);
+      DCHECK(delta_number_of_bits < 32) << "Delta to large";
+      writer->WriteBits(delta_number_of_bits, 5);
+      writer->WriteBits(delta, delta_number_of_bits);
+    }
+  }
+  return old_position;
+}
+
+void TrieBitBuffer::Flush() {
+  if (used_) {
+    AppendBitsElement(current_byte_, used_);
+
+    used_ = 0;
+    current_byte_ = 0;
+  }
+}
+
+}  // namespace transport_security_state
+
+}  // namespace net