mmaparena.h

/*
 * Copyright (c) 2018-2026 Heng Yuan
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#ifndef COOK_MMAP_MEM_ARENA_H
#define COOK_MMAP_MEM_ARENA_H
 
#ifdef _WIN32
#include <windows.h>
#else   // _WIN32
#include <sys/mman.h>
#endif  // _WIN32
 
#include "config.h"
#include "arena.h"
 
namespace cookmem
{
 
#ifdef _WIN32
class MmapArena
{
public:
    MmapArena (std::size_t minSize = DEFAULT_MIN_SEGMENT_SIZE, DWORD prot = PAGE_READWRITE, DWORD type = ( MEM_RESERVE | MEM_COMMIT ))
      : m_minSize (minSize),
        m_prot (prot),
        m_type (type)
    {
    }
 
    void*
    getSegment(std::size_t& size)
    {
        if (size < m_minSize)
        {
            size = m_minSize;
        }
        return VirtualAlloc (nullptr, size, m_type, m_prot);
    }
 
    bool
    freeSegment (void* ptr, std::size_t)
    {
        return VirtualFree (ptr, 0, MEM_RELEASE) == 0;
    }
 
    void
    releaseAll ()
    {
    }
 
private:
    std::size_t m_minSize;
    DWORD       m_prot;
    DWORD       m_type;
};
#else   // _WIN32
class MmapArena
{
public:
    MmapArena(std::size_t minSize = DEFAULT_MIN_SEGMENT_SIZE, int prot = ( PROT_READ | PROT_WRITE ), int flag = ( MAP_PRIVATE | MAP_ANONYMOUS ))
      : m_minSize (minSize),
        m_prot (prot),
        m_flag (flag)
    {
    }
 
    void*
    getSegment (std::size_t& size)
    {
        if (size < m_minSize)
        {
            size = m_minSize;
        }
        void* ptr = mmap(nullptr, size, m_prot, m_flag, -1, 0);
        if (ptr == MAP_FAILED)
        {
            return nullptr;
        }
        return ptr;
    }
 
    bool
    freeSegment (void* ptr, std::size_t size)
    {
        return munmap (ptr, size) != 0;
    }
 
    void
    releaseAll ()
    {
    }
 
private:
    std::size_t m_minSize;
    int         m_prot;
    int         m_flag;
};
#endif  // _WIN32
 
}   // namespace cookmem
 
#endif  // COOK_MMAP_MEM_ARENA_H