//
// getRcd - 获取一条记录
//
RC RMFileHandle::getRcd(const RID &rid, RMRecord &rcd)
{
if (!isValidRID(rid)) return RM_BAD_RID;
Page num = rid.page();
Slot pos = rid.slot();
PFPageHandle page = PFGetPage(pffile_, num);
Ptr addr = page.rawPtr();
RMPageHdr hdr(capacity_, addr);
if (hdr.map.available(pos)) return RM_NORECATRID; // 该pos必定不会空闲
addr = addr + hdr.lenOfHdr() + pos * rcdlen_;
rcd.set(addr, rmhdr_.rcdlen, rid); // 设定记录
return 0;
}
RC RMFileHandle::deleteRcd(const RID &rid)
{
if (!isValidRID(rid)) return RM_BAD_RID;
Page num = rid.page();
Slot pos = rid.slot();
PFPageHandle page = PFGetPage(pffile_, num); // 获取对应的页面
Ptr addr = page.rawPtr();
RMPageHdr hdr(capacity_, addr);
if (hdr.map.available(pos)) return RM_NORECATRID; // 早已经为free
hdr.map.set(pos); // 将对应的pos设置为0
int remain = hdr.remain();
if (hdr.remain() == 0) {
hdr.setNext(rmhdr_.free);
rmhdr_.free = num;
}
hdr.setRemain(hdr.remain() + 1);
page.setDirty();
return 0;
}
//
// updateRcd 更新一条记录, rcd中记录了记录在磁盘中的位置
//
RC RMFileHandle::updateRcd(const RMRecord &rcd)
{
RID rid;
rcd.getRid(rid);
if (!isValidRID(rid)) return RM_BAD_RID;
Page num = rid.page();
Slot pos = rid.slot();
Ptr src;
PFPageHandle page = PFGetPage(pffile_, num);
Ptr dst = page.rawPtr();
RMPageHdr hdr(capacity_, dst);
if (hdr.map.available(pos)) return RM_NORECATRID;
rcd.getData(src);
dst = dst + hdr.lenOfHdr() + pos * rcdlen_;
memcpy(dst, src, rcdlen_);
page.setDirty();
return 0;
}
bool RMFileHandle::isValidRID(const RID& rid) const
{
Slot slot = rid.slot();
return isValidPage(rid.page()) && slot >= 0;
}
