PX4-Autopilot/libuavcan/include/uavcan/dynamic_memory.hpp

/*
 * Copyright (C) 2014 Pavel Kirienko <pavel.kirienko@gmail.com>
 */

#pragma once

#include <cassert>
#include <cstdlib>
#include <cstring>
#include <uavcan/stdint.hpp>
#include <uavcan/util/templates.hpp>
#include <uavcan/util/placement_new.hpp>
#include <uavcan/build_config.hpp>

namespace uavcan
{
/**
 * This interface is used by other library components that need dynamic memory.
 */
class UAVCAN_EXPORT IPoolAllocator
{
public:
    virtual ~IPoolAllocator() { }

    virtual void* allocate(std::size_t size) = 0;
    virtual void deallocate(const void* ptr) = 0;

    virtual bool isInPool(const void* ptr) const = 0;

    virtual std::size_t getBlockSize() const = 0;
    virtual std::size_t getNumBlocks() const = 0;
};

/**
 * Pool manager contains multiple pool allocators of different block sizes and
 * finds the most suitable allocator for every allocation request.
 */
template <unsigned MaxPools>
class UAVCAN_EXPORT PoolManager : public IPoolAllocator, Noncopyable
{
    IPoolAllocator* pools_[MaxPools];

    static int qsortComparePoolAllocators(const void* raw_a, const void* raw_b)
    {
        const IPoolAllocator* const a = *static_cast<const IPoolAllocator* const*>(raw_a);
        const IPoolAllocator* const b = *static_cast<const IPoolAllocator* const*>(raw_b);
        const std::size_t a_size = a ? a->getBlockSize() : NumericTraits<std::size_t>::max();
        const std::size_t b_size = b ? b->getBlockSize() : NumericTraits<std::size_t>::max();
        if (a_size != b_size)
        {
            return (a_size > b_size) ? 1 : -1;
        }
        return 0;
    }

public:
    PoolManager()
    {
        (void)std::memset(pools_, 0, sizeof(pools_));
    }

    bool addPool(IPoolAllocator* pool);

    virtual void* allocate(std::size_t size);
    virtual void deallocate(const void* ptr);

    virtual bool isInPool(const void* ptr) const;

    virtual std::size_t getBlockSize() const;
    virtual std::size_t getNumBlocks() const;
};

/**
 * Classic implementation of a pool allocator (Meyers).
 */
template <std::size_t PoolSize, std::size_t BlockSize>
class UAVCAN_EXPORT PoolAllocator : public IPoolAllocator, Noncopyable
{
    union Node
    {
        uint8_t data[BlockSize];
        Node* next;
    };

    Node* free_list_;
    union
    {
         uint8_t bytes[PoolSize];
         long double _aligner1;
         long long _aligner2;
         Node _aligner3;
    } pool_;

public:
    static const unsigned NumBlocks = unsigned(PoolSize / BlockSize);

    PoolAllocator();

    virtual void* allocate(std::size_t size);
    virtual void deallocate(const void* ptr);

    virtual bool isInPool(const void* ptr) const;

    virtual std::size_t getBlockSize() const { return BlockSize; }
    virtual std::size_t getNumBlocks() const { return NumBlocks; }

    unsigned getNumFreeBlocks() const;
    unsigned getNumUsedBlocks() const { return NumBlocks - getNumFreeBlocks(); }
};

/**
 * Limits the maximum number of blocks that can be allocated in a given allocator.
 */
class LimitedPoolAllocator : public IPoolAllocator
{
    IPoolAllocator& allocator_;
    const std::size_t max_blocks_;
    std::size_t used_blocks_;

public:
    LimitedPoolAllocator(IPoolAllocator& allocator, std::size_t max_blocks)
        : allocator_(allocator)
        , max_blocks_(max_blocks)
        , used_blocks_(0)
    {
        UAVCAN_ASSERT(max_blocks_ > 0);
    }

    virtual void* allocate(std::size_t size);
    virtual void deallocate(const void* ptr);

    virtual bool isInPool(const void* ptr) const;

    virtual std::size_t getBlockSize() const;
    virtual std::size_t getNumBlocks() const;
};

// ----------------------------------------------------------------------------

/*
 * PoolManager<>
 */
template <unsigned MaxPools>
bool PoolManager<MaxPools>::addPool(IPoolAllocator* pool)
{
    UAVCAN_ASSERT(pool);
    bool retval = false;
    for (unsigned i = 0; i < MaxPools; i++)
    {
        UAVCAN_ASSERT(pools_[i] != pool);
        if (pools_[i] == NULL || pools_[i] == pool)
        {
            pools_[i] = pool;
            retval = true;
            break;
        }
    }
    // We need to keep the pools in order, so that smallest blocks go first
    using namespace std; // for qsort()
    qsort(pools_, MaxPools, sizeof(IPoolAllocator*), &PoolManager::qsortComparePoolAllocators);
    return retval;
}

template <unsigned MaxPools>
void* PoolManager<MaxPools>::allocate(std::size_t size)
{
    for (unsigned i = 0; i < MaxPools; i++)
    {
        if (pools_[i] == NULL)
        {
            break;
        }
        void* const pmem = pools_[i]->allocate(size);
        if (pmem != NULL)
        {
            return pmem;
        }
    }
    return NULL;
}

template <unsigned MaxPools>
void PoolManager<MaxPools>::deallocate(const void* ptr)
{
    for (unsigned i = 0; i < MaxPools; i++)
    {
        if (pools_[i] == NULL)
        {
            UAVCAN_ASSERT(0);
            break;
        }
        if (pools_[i]->isInPool(ptr))
        {
            pools_[i]->deallocate(ptr);
            break;
        }
    }
}

template <unsigned MaxPools>
bool PoolManager<MaxPools>::isInPool(const void* ptr) const
{
    for (unsigned i = 0; i < MaxPools; i++)
    {
        if (pools_[i] == NULL)
        {
            break;
        }
        if (pools_[i]->isInPool(ptr))
        {
            return true;
        }
    }
    return false;
}

template <unsigned MaxPools>
std::size_t PoolManager<MaxPools>::getBlockSize() const
{
    return 0;
}

template <unsigned MaxPools>
std::size_t PoolManager<MaxPools>::getNumBlocks() const
{
    std::size_t ret = 0;
    for (unsigned i = 0; i < MaxPools; i++)
    {
        if (pools_[i] == NULL)
        {
            break;
        }
        ret += pools_[i]->getNumBlocks();
    }
    return ret;
}

/*
 * PoolAllocator<>
 */
template <std::size_t PoolSize, std::size_t BlockSize>
PoolAllocator<PoolSize, BlockSize>::PoolAllocator()
    : free_list_(reinterpret_cast<Node*>(pool_.bytes))
{
    (void)std::memset(pool_.bytes, 0, PoolSize);
    for (unsigned i = 0; (i + 1) < (NumBlocks - 1 + 1); i++) // -Werror=type-limits
    {
        // coverity[dead_error_line : FALSE]
        free_list_[i].next = free_list_ + i + 1;
    }
    free_list_[NumBlocks - 1].next = NULL;
}

template <std::size_t PoolSize, std::size_t BlockSize>
void* PoolAllocator<PoolSize, BlockSize>::allocate(std::size_t size)
{
    if (free_list_ == NULL || size > BlockSize)
    {
        return NULL;
    }
    void* pmem = free_list_;
    free_list_ = free_list_->next;
    return pmem;
}

template <std::size_t PoolSize, std::size_t BlockSize>
void PoolAllocator<PoolSize, BlockSize>::deallocate(const void* ptr)
{
    if (ptr == NULL)
    {
        return;
    }
    Node* p = static_cast<Node*>(const_cast<void*>(ptr));
    p->next = free_list_;
    free_list_ = p;
}

template <std::size_t PoolSize, std::size_t BlockSize>
bool PoolAllocator<PoolSize, BlockSize>::isInPool(const void* ptr) const
{
    return ptr >= pool_.bytes &&
           ptr < (pool_.bytes + PoolSize);
}

template <std::size_t PoolSize, std::size_t BlockSize>
unsigned PoolAllocator<PoolSize, BlockSize>::getNumFreeBlocks() const
{
    unsigned num = 0;
    Node* p = free_list_;
    while (p)
    {
        num++;
        UAVCAN_ASSERT(num <= NumBlocks);
        p = p->next;
    }
    return num;
}

}