third_party/WebKit/Source/wtf/text/AtomicStringTable.h

// Copyright 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.

#ifndef WTF_AtomicStringTable_h
#define WTF_AtomicStringTable_h

#include "wtf/Allocator.h"
#include "wtf/HashSet.h"
#include "wtf/WTFExport.h"
#include "wtf/WTFThreadData.h"
#include "wtf/text/StringHash.h"
#include "wtf/text/StringImpl.h"

namespace WTF {

// The underlying storage that keeps the map of unique AtomicStrings. This is
// not thread safe and each WTFThreadData has one.
class WTF_EXPORT AtomicStringTable final {
    USING_FAST_MALLOC(AtomicStringTable);
    WTF_MAKE_NONCOPYABLE(AtomicStringTable);
public:
    AtomicStringTable();
    ~AtomicStringTable();

    // Gets the shared table for the current thread.
    static AtomicStringTable& instance()
    {
        return wtfThreadData().getAtomicStringTable();
    }

    // Used by system initialization to preallocate enough storage for all of
    // the static strings.
    void reserveCapacity(unsigned size);

    // Inserting strings into the table. Note that the return value from adding
    // a UChar string may be an LChar string as the table will attempt to
    // convert the string to save memory if possible.
    StringImpl* add(StringImpl*);
    PassRefPtr<StringImpl> add(const LChar* chars, unsigned length);
    PassRefPtr<StringImpl> add(const UChar* chars, unsigned length);

    // Adding UTF8.
    // Returns null if the characters contain invalid utf8 sequences.
    // Pass null for the charactersEnd to automatically detect the length.
    PassRefPtr<StringImpl> addUTF8(const char* charactersStart, const char* charactersEnd);

    // This is for ~StringImpl to unregister a string before destruction since
    // the table is holding weak pointers. It should not be used directly.
    void remove(StringImpl*);

private:
    template<typename T, typename HashTranslator>
    inline PassRefPtr<StringImpl> addToStringTable(const T& value);

    HashSet<StringImpl*> m_table;
};

} // namespace WTF

using WTF::AtomicStringTable;

#endif