qqmljsmemorypool_p.h

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// Copyright (C) 2021 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
#ifndef QQMLJSMEMORYPOOL_P_H
#define QQMLJSMEMORYPOOL_P_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
#include <QtCore/private/qglobal_p.h>
#include <QtCore/qstring.h>
#include <QtCore/qvector.h>
 
#include <cstdlib>
 
QT_BEGIN_NAMESPACE
 
namespace QQmlJS {
 
class Managed;
 
class MemoryPool
{
    Q_DISABLE_COPY_MOVE(MemoryPool);
 
public:
    MemoryPool() = default;
    ~MemoryPool()
    {
        if (_blocks) {
            for (int i = 0; i < _allocatedBlocks; ++i) {
                if (char *b = _blocks[i])
                    free(b);
            }
 
            free(_blocks);
        }
    }
 
    inline void *allocate(size_t size)
    {
        size = (size + 7) & ~size_t(7);
        if (Q_LIKELY(_ptr && size < size_t(_end - _ptr))) {
            void *addr = _ptr;
            _ptr += size;
            return addr;
        }
        return allocate_helper(size);
    }
 
    void reset()
    {
        _blockCount = -1;
        _ptr = _end = nullptr;
    }
 
    template <typename Tp> Tp *New() { return new (this->allocate(sizeof(Tp))) Tp(); }
    template <typename Tp, typename... Ta> Tp *New(Ta... args)
    { return new (this->allocate(sizeof(Tp))) Tp(args...); }
 
    QStringView newString(QString string) {
        return strings.emplace_back(std::move(string));
    }
 
private:
    Q_NEVER_INLINE void *allocate_helper(size_t size)
    {
        size_t currentBlockSize = DEFAULT_BLOCK_SIZE;
        while (Q_UNLIKELY(size >= currentBlockSize))
            currentBlockSize *= 2;
 
        if (++_blockCount == _allocatedBlocks) {
            if (! _allocatedBlocks)
                _allocatedBlocks = DEFAULT_BLOCK_COUNT;
            else
                _allocatedBlocks *= 2;
 
            _blocks = reinterpret_cast<char **>(realloc(_blocks, sizeof(char *) * size_t(_allocatedBlocks)));
            Q_CHECK_PTR(_blocks);
 
            for (int index = _blockCount; index < _allocatedBlocks; ++index)
                _blocks[index] = nullptr;
        }
 
        char *&block = _blocks[_blockCount];
 
        if (! block) {
            block = reinterpret_cast<char *>(malloc(currentBlockSize));
            Q_CHECK_PTR(block);
        }
 
        _ptr = block;
        _end = _ptr + currentBlockSize;
 
        void *addr = _ptr;
        _ptr += size;
        return addr;
    }
 
private:
    char **_blocks = nullptr;
    int _allocatedBlocks = 0;
    int _blockCount = -1;
    char *_ptr = nullptr;
    char *_end = nullptr;
    QStringList strings;
 
    enum
    {
        DEFAULT_BLOCK_SIZE = 8 * 1024,
        DEFAULT_BLOCK_COUNT = 8
    };
};
 
class Managed
{
    Q_DISABLE_COPY(Managed)
public:
    Managed() = default;
    ~Managed() = default;
 
    void *operator new(size_t size, MemoryPool *pool) { return pool->allocate(size); }
    void operator delete(void *) {}
    void operator delete(void *, MemoryPool *) {}
};
 
} // namespace QQmlJS
 
QT_END_NAMESPACE
 
#endif