145 lines
4.0 KiB
C++
145 lines
4.0 KiB
C++
#include "Kernel\Sys.h"
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#include "Interrupt.h"
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#include "Heap.h"
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#include "TTime.h"
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#define MEMORY_ALIGN 4
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// 当前堆
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const Heap* Heap::Current = nullptr;
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/*
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堆分配原理：
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1，使用内存块，记录当前块已使用大小以及下一块地址，形成内存块链表
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2，每个内存块剩余空间是下一块指针减去当前块指针再减去已用大小
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3，初始化第一个内存块，已使用0
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4，申请内存时，从第一块开始找空余空间大于等于目标大小的内存块，割下来作为链表新节点
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5，释放内存时，找到所在块，然后当前块上一块的Next指针直接指向当前块的下一块地址，移除当前节点
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*/
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/******************************** MemoryBlock ********************************/
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// 内存块。大小和下一块地址
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typedef struct MemoryBlock_
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{
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int Used;
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struct MemoryBlock_* Next;
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} MemoryBlock;
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/******************************** Heap ********************************/
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Heap::Heap(uint addr, int size)
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{
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Current = this;
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// 地址对齐
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uint end = addr + size;
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addr = (addr + MEMORY_ALIGN - 1) & (~(MEMORY_ALIGN - 1));
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end = end & (~(MEMORY_ALIGN - 1));
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Address = addr;
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Size = end - addr;
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// 第一块内存块
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auto mb = (MemoryBlock*)addr;
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mb->Used = sizeof(MemoryBlock);
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mb->Next = (MemoryBlock*)(end - sizeof(MemoryBlock));
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mb->Next->Used = sizeof(MemoryBlock);
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mb->Next->Next = nullptr;
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_Used = sizeof(MemoryBlock) << 1;
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_Count = 0;
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// 记录第一个有空闲内存的块，减少内存分配时的查找次数
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_First = mb;
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debug_printf("Heap::Init(0x%p, %d) Free=%d \r\n", Address, Size, FreeSize());
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}
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int Heap::Used() const { return _Used; }
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int Heap::Count() const { return _Count; }
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int Heap::FreeSize() const { return Size - _Used; }
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void* Heap::Alloc(int size)
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{
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// 要申请的内存大小需要对齐
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size = (size + MEMORY_ALIGN - 1) & (~(MEMORY_ALIGN - 1));
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//debug_printf("Address=%p Size=%d ", Address, Size);
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int remain = Size - _Used;
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if (size > remain)
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{
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debug_printf("Heap::Alloc %d > %d (0x%p) 失败！Size=%d Used=%d First=%p \r\n", size, remain, remain, Size, _Used, _First);
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return nullptr;
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}
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#if DEBUG
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// 检查头部完整性
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auto head = (MemoryBlock*)Address;
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//assert(_First >= head && head->Used <= Size && (byte*)head + head->Used <= (byte*)head->Next, "堆头被破坏！");
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assert(head->Used <= Size && (byte*)head + head->Used <= (byte*)head->Next, "堆头被破坏！");
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assert(_Used <= Size, "Heap::Used异常！");
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#endif
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void* ret = nullptr;
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int need = size + sizeof(MemoryBlock);
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SmartIRQ irq;
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for (auto mcb = (MemoryBlock*)_First; mcb->Next != nullptr; mcb = mcb->Next)
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{
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// 找到一块满足大小的内存块。计算当前块剩余长度
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int free = (byte*)mcb->Next - (byte*)mcb - mcb->Used;
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if (free >= need)
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{
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// 割一块出来
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auto tmp = (MemoryBlock*)((byte*)mcb + mcb->Used);
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tmp->Next = mcb->Next;
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tmp->Used = need;
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mcb->Next = tmp;
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// 记录第一个有空闲内存的块，减少内存分配时的查找次数
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_First = tmp;
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ret = (byte*)(tmp + 1);
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_Used += need;
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_Count++;
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//debug_printf("Heap::Alloc (%p, %d) First=%p Used=%d Count=%d \r\n", ret, need, _First, _Used, _Count);
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return ret;
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}
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}
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if (!ret) debug_printf("Heap::Alloc %d 失败！Count=%d Used=%d Free=%d First=%p \r\n", size, _Count, _Used, FreeSize(), _First);
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return ret;
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}
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void Heap::Free(void* ptr)
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{
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auto prev = (MemoryBlock*)Address;
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auto cur = (MemoryBlock*)ptr - 1;
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SmartIRQ irq;
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for (auto mcb = prev->Next; mcb->Next != nullptr; mcb = mcb->Next)
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{
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// 找到内存块
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if (mcb == cur)
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{
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_Used -= cur->Used;
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_Count--;
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// 前面有空闲位置
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if (cur <= _First) _First = prev;
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//debug_printf("Heap::Free (%p, %d) First=%p Used=%d Count=%d \r\n", ptr, cur->Used, _First, _Used, _Count);
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prev->Next = cur->Next;
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return;
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}
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prev = mcb;
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}
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debug_printf("正在释放不是本系统申请的内存 0x%p \r\n", ptr);
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}
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