Move Source/WTF/wtf to Source/wtf

Source/WTF/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.
- */
-
-#ifndef BloomFilter_h
-#define BloomFilter_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 {
-public:
-    COMPILE_ASSERT(keyBits <= 16, bloom_filter_key_size);
-
-    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 !ASSERT_DISABLED
-    // 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);
-    ASSERT(first);
-    ASSERT(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 !ASSERT_DISABLED
-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
-
-}
-
-using WTF::BloomFilter;
-
-#endif