int RM_FileHandle::DeleteRec(RID &rid) {
//检测错误
int index;
Bytes head = (Bytes)bpm->getPage(fileid, rid.GetPageid(), index);
Bits* slots = new Bits(head, pernum);
if (!slots->bit_get(rid.GetSlotid())) {
//cout << "[RM_FileHandle-Del]Warning: RID doesn't exist" << endl;
return 1;
}
//删除对应记录以及更新空项记录和未满数据页页码记录
int first_index;
BufType first_head = bpm->getPage(fileid, 0, first_index); //打开第一页
int empty_page = *(int*)(first_head + EMPTY_PAGE_OFFSET_4BYTE); //获取未满的最前面数据页页码
int empty_rid_offset = EMPTY_RID_OFFSET_BYTE; //获取下一可插入项的偏移
RID* current_empty_rid = (RID*)(head + empty_rid_offset); //获取下一可插入项
int next_page_offset = NEXT_EMPTY_PAGE_BYTE; //获取下一个含空项页页码的偏移
int next_page = *(int*)(head + next_page_offset); //获取下一个含空项页页码
slots->bit_setzero(rid.GetSlotid()); //删除该记录
bpm->markDirty(index); //将该页标记为脏页
if (current_empty_rid->GetSlotid() == -1) { //若之前为满页
current_empty_rid->slotid = rid.GetSlotid(); //将下一可插入记录项置成当前删除记录
*(int*)(first_head + EMPTY_PAGE_OFFSET_4BYTE) = rid.GetPageid();//则将第一页的值的页码更改为本页码
*(int*)(head + next_page_offset) = empty_page; //本页码的下一空项页改为第一页原来存的页码值
bpm->markDirty(first_index);
}
else {
if (current_empty_rid->slotid > rid.GetSlotid()) { //更新下一可插入项的偏移槽的值
current_empty_rid->slotid = rid.GetSlotid();
}
}
return 0;
}
int RM_FileHandle::GetRec(RID &rid, RM_Record &rec) {
int index;
Bytes head = (Bytes)bpm->getPage(fileid, rid.GetPageid(), index);
Bits* slots = new Bits(head, pernum); //获取slot数组，先判断获取的记录是否为空
if (!slots->bit_get(rid.GetSlotid())) {
// cout << "[RM_FileHandle]Invalid Record:Empty" << endl;
return 1;
}
int offset = PAGE_HEAD_BYTE;
offset = offset + rid.GetSlotid() * recordsize;
char* get_data = new char[recordsize];
memcpy(get_data,head + offset,recordsize);
RM_Record *newR = new RM_Record(get_data, recordsize);
rec = *newR;
return 0;
}
int RM_FileHandle::UpdateRec(RID &rid, RM_Record &rec) {
int index;
Bytes head = (Bytes)bpm->getPage(fileid, rid.GetPageid(), index);
Bits* slots = new Bits(head, pernum);
if (!slots->bit_get(rid.GetSlotid())) {
//cout << "[RM_FileHandle-Update]Warning: RID doesn't exist,Maybe need Insert" << endl;
return 1;
}
int offset = PAGE_HEAD_BYTE;
offset = offset + recordsize * rid.GetSlotid();
Bytes rlocation = (Bytes)head;
rlocation = rlocation + offset;
memcpy(rlocation, rec.GetRdata(), rec.GetSize());
slots->bit_setone(rid.GetSlotid());
bpm->markDirty(index);
return 0;
}
