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;
}
int RM_FileHandle::InsertRec(RID &rid, RM_Record &rec) { //这里的RID是插入后返回一个RID，其余成员函数都是需要一个RID
int first_index;
BufType first_head = bpm->getPage(fileid, 0, first_index);
int empty_rid_offset = EMPTY_RID_OFFSET_BYTE; //获取下一可插入项的偏移
int next_page_offset = NEXT_EMPTY_PAGE_BYTE; //获取下一个含空项页页码的偏移
int slots_offset = SLOT_OFFSET_BYTE; //获取slot偏移位置
if (*(int*)(first_head + EMPTY_PAGE_OFFSET_4BYTE) != -1) { //存在下一个空记录
int insert_page_index;
Bytes insert_page_head = (Bytes)bpm->getPage(fileid, first_head[EMPTY_PAGE_OFFSET_4BYTE], insert_page_index);
bpm->markDirty(insert_page_index); //肯定要修改，所以提前标记为脏页
RID* current_empty_rid = (RID*)(insert_page_head + empty_rid_offset); //下一可插入项
int next_page = *(int*)(insert_page_head + next_page_offset); //下一个含空项页页码
Bits* slots = new Bits(insert_page_head + slots_offset, pernum); //slots
int offset = PAGE_HEAD_BYTE;
offset = offset + recordsize * current_empty_rid->GetSlotid();
Bytes rlocation = insert_page_head + offset; //获取相应偏移后的地址
memcpy(rlocation, rec.GetRdata(), rec.GetSize()); //插入该记录
slots->bit_setone(current_empty_rid->GetSlotid()); //slot相应位子置1
rid = *current_empty_rid; //rid返回
bool isfull = true; //标记用，true表示当前页满
for (int current_slot = current_empty_rid->GetSlotid() + 1; current_slot < pernum; current_slot++) {
if (!slots->bit_get(current_slot)) { //寻找下一个current_empty_rid,当slots[i]为0时说明该位为空
isfull = false;
current_empty_rid->SetSlotid(current_slot); //修改下一个空项的位置
break;
}
}
if (isfull) { //如果页满了
first_head[EMPTY_PAGE_OFFSET_4BYTE] = next_page; //当前数据页的下一页给第一页的含空项页
bpm->markDirty(first_index); //标记脏页
current_empty_rid->SetSlotid(-1); //slotid为-1表示没有下一项
*(int*)(insert_page_head + next_page_offset) = -1; //下一个含空项页页码表示当前页为满页
}
} else { //均为满页，新建一页
pagesum++; //总页数新增一页
first_head[PSIZE_OFFSET_4BYTE] = pagesum; //修改总页数
bpm->markDirty(first_index); //标记为脏页
int new_index; //新建一个页，并将slot清零
Bytes new_head = (Bytes)bpm->getPage(fileid, pagesum - 1, new_index);
Bits* new_slots = new Bits(new_head + slots_offset, pernum);
new_slots->all_zero();
int new_offset = PAGE_HEAD_BYTE; //slot[0]即为第一条记录，存储insert的记录
Bytes rlocation = new_head + new_offset;
memcpy(rlocation, rec.GetRdata(), rec.GetSize());
new_slots->bit_setone(0);
bpm->markDirty(new_index); //标记为脏页
RID new_rid;
new_rid.SetFileid(-1);
new_rid.SetPageid(pagesum - 1);
new_rid.SetSlotid(1);
*(RID*)(new_head + empty_rid_offset) = new_rid; //下一可插入项更新为第1项
rid = new_rid;
rid.SetSlotid(0);
first_head[EMPTY_PAGE_OFFSET_4BYTE] = pagesum - 1; //第一页的含空项页设为当下的新增页
*(int*)(new_head + next_page_offset) = -1; //由于之前都是满页，这页显然没有后继页面，设为-1
}
return 0;
}