lockedpool.h

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// Copyright (c) 2016-2020 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#ifndef BITCOIN_SUPPORT_LOCKEDPOOL_H
#define BITCOIN_SUPPORT_LOCKEDPOOL_H
 
#include <cstddef>
#include <list>
#include <map>
#include <memory>
#include <mutex>
#include <unordered_map>
 
class LockedPageAllocator
{
public:
    virtual ~LockedPageAllocator() = default;
    virtual void* AllocateLocked(size_t len, bool *lockingSuccess) = 0;
 
    virtual void FreeLocked(void* addr, size_t len) = 0;
 
    virtual size_t GetLimit() = 0;
};
 
/* An arena manages a contiguous region of memory by dividing it into
 * chunks.
 */
class Arena
{
public:
    Arena(void *base, size_t size, size_t alignment);
    virtual ~Arena();
 
    Arena(const Arena& other) = delete; // non construction-copyable
    Arena& operator=(const Arena&) = delete; // non copyable
 
    struct Stats
    {
        size_t used;
        size_t free;
        size_t total;
        size_t chunks_used;
        size_t chunks_free;
    };
 
    void* alloc(size_t size);
 
    void free(void *ptr);
 
    Stats stats() const;
 
#ifdef ARENA_DEBUG
    void walk() const;
#endif
 
    bool addressInArena(void *ptr) const { return ptr >= base && ptr < end; }
private:
    typedef std::multimap<size_t, void*> SizeToChunkSortedMap;
    SizeToChunkSortedMap size_to_free_chunk;
 
    typedef std::unordered_map<void*, SizeToChunkSortedMap::const_iterator> ChunkToSizeMap;
    ChunkToSizeMap chunks_free;
    ChunkToSizeMap chunks_free_end;
 
    std::unordered_map<void*, size_t> chunks_used;
 
    void* base;
    void* end;
    size_t alignment;
};
 
class LockedPool
{
public:
    static const size_t ARENA_SIZE = 256*1024;
    static const size_t ARENA_ALIGN = 16;
 
    typedef bool (*LockingFailed_Callback)();
 
    struct Stats
    {
        size_t used;
        size_t free;
        size_t total;
        size_t locked;
        size_t chunks_used;
        size_t chunks_free;
    };
 
    explicit LockedPool(std::unique_ptr<LockedPageAllocator> allocator, LockingFailed_Callback lf_cb_in = nullptr);
    ~LockedPool();
 
    LockedPool(const LockedPool& other) = delete; // non construction-copyable
    LockedPool& operator=(const LockedPool&) = delete; // non copyable
 
    void* alloc(size_t size);
 
    void free(void *ptr);
 
    Stats stats() const;
private:
    std::unique_ptr<LockedPageAllocator> allocator;
 
    class LockedPageArena: public Arena
    {
    public:
        LockedPageArena(LockedPageAllocator *alloc_in, void *base_in, size_t size, size_t align);
        ~LockedPageArena();
    private:
        void *base;
        size_t size;
        LockedPageAllocator *allocator;
    };
 
    bool new_arena(size_t size, size_t align);
 
    std::list<LockedPageArena> arenas;
    LockingFailed_Callback lf_cb;
    size_t cumulative_bytes_locked{0};
    mutable std::mutex mutex;
};
 
class LockedPoolManager : public LockedPool
{
public:
    static LockedPoolManager& Instance()
    {
        static std::once_flag init_flag;
        std::call_once(init_flag, LockedPoolManager::CreateInstance);
        return *LockedPoolManager::_instance;
    }
 
private:
    explicit LockedPoolManager(std::unique_ptr<LockedPageAllocator> allocator);
 
    static void CreateInstance();
    static bool LockingFailed();
 
    static LockedPoolManager* _instance;
};
 
#endif // BITCOIN_SUPPORT_LOCKEDPOOL_H