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MemoryPool.cpp
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MemoryPool.cpp
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#include "MemoryPool.h"
#include <malloc.h>
#include <assert.h>
#include <string.h>
namespace ace
{
void MemoryZone::clear()
{
}
ace::MemoryPool::MemoryPool()
{
zone = (MemoryZone*)calloc(MEMORYSIZ, 1);
if (zone == nullptr) {
assert(false);
return;
}
memset((char*)zone, 0, MEMORYSIZ);
zone->siz = MEMORYSIZ;
MemoryBlock* block;
zone->blocklist.next = zone->blocklist.prev
= block = (MemoryBlock*)((char*)zone + sizeof(MemoryZone));
zone->blocklist.tag = 1;
zone->blocklist.id = 0;
zone->blocklist.siz = 0;
zone->rover = block;
zone->used = 0;
block->prev = block->next = &zone->blocklist;
block->tag = 0;
block->id = ZONEID;
block->siz = MEMORYSIZ - sizeof(MemoryZone);
}
void* ace::MemoryPool::malloc(int siz)
{
if (zone == nullptr) return nullptr;
int extra, allocSize;
MemoryBlock* start, * rover, * newer, * base;
allocSize = siz;
siz += sizeof(MemoryBlock);
siz += 4;
//如果size是4的整数倍,则size不变,如果有余数,则会向上取到4的整数
siz = (siz + 3) & ~3;
base = rover = zone->rover;
start = base->prev;
do {
if (rover == start)
{
return nullptr;
}
if (rover->tag == 0 && rover->siz >= siz) {
base = rover;
break;
}
else {
rover = rover->next;
}
} while (true);
extra = base->siz - siz;
if (extra > MINFRAGMENT) {
newer = (MemoryBlock*)((char*)(base)+siz);
newer->id = ZONEID;
newer->prev = base;
newer->next = base->next;
newer->siz = extra;
newer->tag = 0;
newer->next->prev = newer;
base->next = newer;
base->siz = siz;
}
base->tag = 1;
zone->rover = base->next;
zone->used += base->siz;
base->id = ZONEID;
// marker for memory trash testing
*(int*)((char*)base + base->siz - 4) = ZONEID;
return (void*)((char*)(base)+sizeof(MemoryBlock));
}
MemoryPool::~MemoryPool()
{
::free((char*)zone);
}
void MemoryPool::free(void* ptr)
{
if (zone == nullptr || ptr == nullptr) return;
MemoryBlock* block = (MemoryBlock * )((char*)ptr - sizeof(MemoryBlock));
//安全检查
if (block->tag == 0) {
assert(false);
return;
}
if (block->id != ZONEID) {
assert(false);
return;
}
zone->used -= block->siz;
//将这块内存置为一段访问会引起错误的代码
memset(ptr, 0xaa, block->siz - sizeof(*block));
block->tag = 0;
MemoryBlock* other = block->prev;
if (!other->tag) {
other->next = block->next;
other->next->prev = other;
other->siz += block->siz;
if (zone->rover == block) {
zone->rover = other;
}
block = other;
}
other = block->next;
if (!other->tag) {
block->next = other->next;
block->next->prev = block;
block->siz += other->siz;
if (zone->rover == other)
zone->rover = block;
}
}
}