Revert "Move files in wtf/ to platform/wtf/"

third_party/WebKit/Source/wtf/BloomFilter.h

Index: third_party/WebKit/Source/wtf/BloomFilter.h
diff --git a/third_party/WebKit/Source/wtf/BloomFilter.h b/third_party/WebKit/Source/wtf/BloomFilter.h
index b37327e0514a86ee69e32a1238d699d33959d7a2..4618304cfb8b56115d5f43321dfc5e2af7bcfc30 100644
--- a/third_party/WebKit/Source/wtf/BloomFilter.h
+++ b/third_party/WebKit/Source/wtf/BloomFilter.h
@@ -1,9 +1,149 @@
-// 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.
+/*
+ * 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.
+ */
 
-#include "platform/wtf/BloomFilter.h"
+#ifndef BloomFilter_h
+#define BloomFilter_h
 
-// 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
+#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