Reland: Move files in wtf/ to platform/wtf/ (Part 12).

third_party/WebKit/Source/wtf/BloomFilter.h

-/*
- * Copyright (C) 2011 Apple Inc. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in the
- *    documentation and/or other materials provided with the distribution.
- *
- * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
- * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
- * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
- * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
- * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
- * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
- * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
- * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
- * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
- * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
- * THE POSSIBILITY OF SUCH DAMAGE.
- */
+// Copyright 2017 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.
 
-#ifndef BloomFilter_h
-#define BloomFilter_h
+#include "platform/wtf/BloomFilter.h"
 
-#include "wtf/Allocator.h"
-#include "wtf/Compiler.h"
-#include "wtf/text/AtomicString.h"
-
-namespace WTF {
-
-// Counting bloom filter with k=2 and 8 bit counters. Uses 2^keyBits bytes of
-// memory.  False positive rate is approximately (1-e^(-2n/m))^2, where n is
-// the number of unique keys and m is the table size (==2^keyBits).
-template <unsigned keyBits>
-class BloomFilter {
-  USING_FAST_MALLOC(BloomFilter);
-
- public:
-  static_assert(keyBits <= 16, "bloom filter key size check");
-
-  static const size_t tableSize = 1 << keyBits;
-  static const unsigned keyMask = (1 << keyBits) - 1;
-  static uint8_t maximumCount() { return std::numeric_limits<uint8_t>::max(); }
-
-  BloomFilter() { clear(); }
-
-  void add(unsigned hash);
-  void remove(unsigned hash);
-
-  // The filter may give false positives (claim it may contain a key it doesn't)
-  // but never false negatives (claim it doesn't contain a key it does).
-  bool mayContain(unsigned hash) const {
-    return firstSlot(hash) && secondSlot(hash);
-  }
-
-  // The filter must be cleared before reuse even if all keys are removed.
-  // Otherwise overflowed keys will stick around.
-  void clear();
-
-  void add(const AtomicString& string) { add(string.impl()->existingHash()); }
-  void add(const String& string) { add(string.impl()->hash()); }
-  void remove(const AtomicString& string) {
-    remove(string.impl()->existingHash());
-  }
-  void remove(const String& string) { remove(string.impl()->hash()); }
-
-  bool mayContain(const AtomicString& string) const {
-    return mayContain(string.impl()->existingHash());
-  }
-  bool mayContain(const String& string) const {
-    return mayContain(string.impl()->hash());
-  }
-
-#if DCHECK_IS_ON()
-  // Slow.
-  bool likelyEmpty() const;
-  bool isClear() const;
-#endif
-
- private:
-  uint8_t& firstSlot(unsigned hash) { return m_table[hash & keyMask]; }
-  uint8_t& secondSlot(unsigned hash) { return m_table[(hash >> 16) & keyMask]; }
-  const uint8_t& firstSlot(unsigned hash) const {
-    return m_table[hash & keyMask];
-  }
-  const uint8_t& secondSlot(unsigned hash) const {
-    return m_table[(hash >> 16) & keyMask];
-  }
-
-  uint8_t m_table[tableSize];
-};
-
-template <unsigned keyBits>
-inline void BloomFilter<keyBits>::add(unsigned hash) {
-  uint8_t& first = firstSlot(hash);
-  uint8_t& second = secondSlot(hash);
-  if (LIKELY(first < maximumCount()))
-    ++first;
-  if (LIKELY(second < maximumCount()))
-    ++second;
-}
-
-template <unsigned keyBits>
-inline void BloomFilter<keyBits>::remove(unsigned hash) {
-  uint8_t& first = firstSlot(hash);
-  uint8_t& second = secondSlot(hash);
-  DCHECK(first);
-  DCHECK(second);
-  // In case of an overflow, the slot sticks in the table until clear().
-  if (LIKELY(first < maximumCount()))
-    --first;
-  if (LIKELY(second < maximumCount()))
-    --second;
-}
-
-template <unsigned keyBits>
-inline void BloomFilter<keyBits>::clear() {
-  memset(m_table, 0, tableSize);
-}
-
-#if DCHECK_IS_ON()
-template <unsigned keyBits>
-bool BloomFilter<keyBits>::likelyEmpty() const {
-  for (size_t n = 0; n < tableSize; ++n) {
-    if (m_table[n] && m_table[n] != maximumCount())
-      return false;
-  }
-  return true;
-}
-
-template <unsigned keyBits>
-bool BloomFilter<keyBits>::isClear() const {
-  for (size_t n = 0; n < tableSize; ++n) {
-    if (m_table[n])
-      return false;
-  }
-  return true;
-}
-#endif
-
-}  // namespace WTF
-
-using WTF::BloomFilter;
-
-#endif
+// The contents of this header was moved to platform/wtf as part of
+// WTF migration project. See the following post for details:
+// https://groups.google.com/a/chromium.org/d/msg/blink-dev/tLdAZCTlcAA/bYXVT8gYCAAJ