103 lines
2.5 KiB
C++
103 lines
2.5 KiB
C++
#include "Kernel\Sys.h"
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#include "Interrupt.h"
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#include "Heap.h"
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#define MEMORY_ALIGN 4
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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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uint 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, uint size)
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{
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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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}
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uint Heap::Used() const { return _Used; }
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uint Heap::Count() const { return _Count; }
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void* Heap::Alloc(uint 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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void* ret = nullptr;
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auto need = size + sizeof(MemoryBlock);
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SmartIRQ irq;
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for(auto mcb=(MemoryBlock*)Address; 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
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auto free = (uint)mcb->Next - (uint)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*)((uint)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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ret = (void*)((uint)(tmp+1));
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_Used += need;
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_Count++;
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break;
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}
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}
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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 mcb = (MemoryBlock*)ptr - 1;
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SmartIRQ irq;
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for(auto find=prev->Next; find->Next!=nullptr; find=find->Next)
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{
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if(find == mcb)
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{
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_Used -= (uint)find->Next - (uint)prev->Next;
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_Count--;
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prev->Next = find->Next;
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break;
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}
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prev = find;
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}
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}
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