//中心控制缓存：承上启下，调度内存
#pragma once
#include"CentralControlCache.h"
#include"PageCache.h"
//类内声明，类外初始化
CentralControlCache CentralControlCache::_sInst;
size_t CentralControlCache::GetRangeMem(void*& start, void*& end, size_t expectedNum, size_t memSize)
{
//计算memSize大小的内存对象在SpanList的索引
size_t index = SizeCalculation::Index(memSize);
std::lock_guard lock(_spanlists[index]._mtx);
//在SpanList中获取还有内存的内存的Span
Span* sp = GetOneSpan(_spanlists[index], memSize);
// 找到一个有对象的span，有多少给多少
size_t j = 1;
start = sp->_list;
void* cur = start;
void* prev = start;
while (j <= expectedNum && cur != nullptr)
{
prev = cur;
cur = Next(cur);
++j;
//使用数量+1，方便归还内存时判断是否全部归还
sp->_usecount++;
}
sp->_list = cur;
end = prev;
Next(prev) = nullptr;
//实际申请的对象个数为j-1个
return j - 1;
}
//在SpanList中获取还有内存的内存的Span
Span* CentralControlCache::GetOneSpan(SpanList& list, size_t memSize)
{
//遍历SpanList，判断是否有内存
Span* cur = list.Begin();
while (cur != list.End())
{
if (cur->_list == nullptr)
cur = cur->_next;
else
return cur;
}
//走到这里证明没有有内存的Span,找pagecache申请内存
Span* span = PageCache::GetInstance()->NewSpan(SizeCalculation::NumMovePage(memSize));
//将申请到的Span切割好挂在SpanList中
//根据页号计算其实地址
char* start = (char*)(span->_pageId << PAGE_SHIFT);
//根据开始地址和页数计算最后一页的二地址
char* end = start + (span->_n << PAGE_SHIFT);
while (start < end)
{
char* next = start + memSize;
// 头插
Next(start) = span->_list;
span->_list = start;
start = next;
}
//设置单个对象的大小
span->_objsize = memSize;
//将申请到的span链接到spanlist中
list.PushFront(span);
return span;
}
void CentralControlCache::ReleaseListToSpans(void* start, size_t memSize)
{
size_t index = SizeCalculation::Index(memSize);
std::lock_guard lock(_spanlists[index]._mtx);
//将一个个对象还给_spanlist中对应的span
while (start)
{
void* next = Next(start);
// 找start内存块属于哪个span
Span* span = PageCache::GetInstance()->GetSpanToMap(start);
// 把对象插入到span管理的list中
Next(start) = span->_list;
span->_list = start;
span->_usecount--;
// _usecount == 0说明这个span中切出去的大块内存都还回来了
if (span->_usecount == 0)
{
//将这个span还给pagecache
_spanlists[index].Erase(span);
span->_list = nullptr;
PageCache::GetInstance()->ReleaseSpanToPageCache(span);
}
start = next;
}
}