heap.hpp

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#ifndef OT_HEAP_HPP_
#define OT_HEAP_HPP_

#include "openthread-core-config.h"

#include <stddef.h>

#include "utils/wrap_stdint.h"

namespace ot {
namespace Crypto {


class Block
{
    friend class Heap;

public:
    uint16_t GetSize(void) const {
        return mSize;
    }

    void SetSize(uint16_t aSize) {
        mSize = aSize;
    }

    uint16_t GetNext(void) const {
        return *reinterpret_cast<const uint16_t *>(reinterpret_cast<const uint8_t *>(this) + sizeof(mSize) + mSize);
    }

    void SetNext(uint16_t aNext) {
        *reinterpret_cast<uint16_t *>(reinterpret_cast<uint8_t *>(this) + sizeof(mSize) + mSize) = aNext;
    }

    void *GetPointer(void) {
        return &mMemory;
    }

    uint16_t GetLeftNext(void) const {
        return *(&mSize - 1);
    }

    bool IsLeftFree(void) const {
        return GetLeftNext() != 0;
    }

    bool IsFree(void) const {
        return mSize != kGuardBlockSize && GetNext() != 0;
    }

private:
    enum
    {
        kGuardBlockSize = 0xffff, 
    };

    uint16_t mSize; 

    uint8_t  mMemory[sizeof(uint16_t)];
};

class Heap
{
public:
    Heap(void);

    void *CAlloc(size_t aCount, size_t aSize);

    void Free(void *aPointer);

    bool IsClean(void) {
        const Block &super = BlockSuper();
        const Block &first = BlockRight(super);
        return super.GetNext() == BlockOffset(first) && first.GetSize() == kFirstBlockSize;
    }

    size_t GetCapacity(void) const {
        return kFirstBlockSize;
    }

private:
    enum
    {
#if OPENTHREAD_ENABLE_DTLS
        kMemorySize = OPENTHREAD_CONFIG_MBEDTLS_HEAP_SIZE,          
#else
        kMemorySize = OPENTHREAD_CONFIG_MBEDTLS_HEAP_SIZE_NO_DTLS,  
#endif
        kAlignSize = sizeof(long),                                  
        kBlockRemainderSize = kAlignSize - sizeof(uint16_t) * 2,    
        kSuperBlockSize = kAlignSize - sizeof(Block),               
        kFirstBlockSize = kMemorySize - kAlignSize * 3 +
                          kBlockRemainderSize,                      
        kSuperBlockOffset = kAlignSize - sizeof(uint16_t),          
        kFirstBlockOffset = kAlignSize * 2 - sizeof(uint16_t),      
        kGuardBlockOffset = kMemorySize - sizeof(uint16_t),         
    };

    Block &BlockAt(uint16_t aOffset) {
        return *reinterpret_cast<Block *>(&mMemory.m16[aOffset / 2]);
    }

    Block &BlockOf(void *aPointer) {
        uint16_t offset = static_cast<uint16_t>(reinterpret_cast<uint8_t *>(aPointer) - mMemory.m8);
        offset -= sizeof(uint16_t);
        return BlockAt(offset);
    }

    Block &BlockSuper(void) {
        return BlockAt(kSuperBlockOffset);
    }

    Block &BlockNext(const Block &aBlock) {
        return BlockAt(aBlock.GetNext());
    }

    Block &BlockRight(const Block &aBlock) {
        return BlockAt(BlockOffset(aBlock) + sizeof(Block) + aBlock.GetSize());
    }

    Block &BlockPrev(const Block &aBlock);

    bool IsLeftFree(const Block &aBlock) {
        return (BlockOffset(aBlock) != kFirstBlockOffset && aBlock.IsLeftFree());
    }

    uint16_t BlockOffset(const Block &aBlock) {
        return static_cast<uint16_t>(reinterpret_cast<const uint8_t *>(&aBlock) - mMemory.m8);
    }

    void BlockInsert(Block &aPrev, Block &aBlock);

    union
    {
        // Make sure memory is long aligned.
        long mLong[kMemorySize / sizeof(long)];
        uint8_t m8[kMemorySize];
        uint16_t m16[kMemorySize / sizeof(uint16_t)];
    } mMemory;
};

}  // namespace Crypto
}  // namespace ot

#endif // OT_HEAP_HPP_