108 lines
3.3 KiB
C++
108 lines
3.3 KiB
C++
#include "storage/disk_manager.h"
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#include <cstring>
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#include <exception>
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#include <stdexcept>
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const size_t kPageSize = 4096;
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DiskManager::DiskManager(const std::string &file_path_, bool renew)
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: file_path(file_path_),
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first_empty_page_id(0),
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current_total_page_count(0),
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current_none_empty_page_count(0),
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raw_data_memory(nullptr),
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fp(nullptr) {
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if (renew) remove(file_path.c_str());
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fp = fopen(file_path.c_str(), "r+b");
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if (fp == nullptr) {
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// File doesn't exist, create a new one
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fp = fopen(file_path.c_str(), "w+b");
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// Initialize internal page
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first_empty_page_id = 0;
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current_total_page_count = 0;
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current_none_empty_page_count = 0;
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raw_data_memory = new char[kPageSize - meta_data_size];
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memset(raw_data_memory, 0, kPageSize - meta_data_size);
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FullyFlush();
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is_new = true;
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} else {
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// File exists, read metadata from internal page
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fseek(fp, 0, SEEK_SET);
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fread(&first_empty_page_id, sizeof(page_id_t), 1, fp);
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fread(¤t_total_page_count, sizeof(size_t), 1, fp);
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fread(¤t_none_empty_page_count, sizeof(size_t), 1, fp);
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raw_data_memory = new char[kPageSize - meta_data_size];
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fread(raw_data_memory, kPageSize - meta_data_size, 1, fp);
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is_new = false;
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}
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page_buf = new char[kPageSize];
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}
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DiskManager::~DiskManager() {
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Close();
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delete[] raw_data_memory;
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delete[] page_buf;
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}
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char *DiskManager::RawDataMemory() { return raw_data_memory; }
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size_t DiskManager::RawDatMemorySize() { return kPageSize - meta_data_size; }
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void DiskManager::FullyFlush() {
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if (fp == nullptr) return;
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fseek(fp, 0, SEEK_SET);
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fwrite(&first_empty_page_id, sizeof(page_id_t), 1, fp);
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fwrite(¤t_total_page_count, sizeof(size_t), 1, fp);
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fwrite(¤t_none_empty_page_count, sizeof(size_t), 1, fp);
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fwrite(raw_data_memory, kPageSize - meta_data_size, 1, fp);
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fflush(fp);
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}
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void DiskManager::Close() {
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if (fp != nullptr) {
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FullyFlush();
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fclose(fp);
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fp = nullptr;
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}
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}
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void DiskManager::ReadPage(page_id_t page_id, char *page_data_ptr) {
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if (fp == nullptr) return;
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fseek(fp, page_id * kPageSize, SEEK_SET);
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fread(page_data_ptr, kPageSize, 1, fp);
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}
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void DiskManager::WritePage(page_id_t page_id, const char *page_data_ptr) {
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if (fp == nullptr) return;
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fseek(fp, page_id * kPageSize, SEEK_SET);
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fwrite(page_data_ptr, kPageSize, 1, fp);
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}
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bool DiskManager::CurrentFileIsNew() { return is_new; }
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page_id_t DiskManager::AllocNewEmptyPageId() {
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page_id_t new_page_id;
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if (first_empty_page_id == 0) {
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// No empty page available, append a new page
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current_total_page_count++;
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new_page_id = current_total_page_count;
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fseek(fp, 0, SEEK_END);
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fwrite(page_buf, kPageSize, 1, fp);
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} else {
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new_page_id = first_empty_page_id;
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ReadPage(new_page_id, page_buf);
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memcpy(&first_empty_page_id, page_buf, sizeof(page_id_t));
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}
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current_none_empty_page_count++;
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return new_page_id;
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}
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void DiskManager::DeallocatePage(page_id_t page_id) {
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// Add the deallocated page to the head of the empty list
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memcpy(page_buf, &first_empty_page_id, sizeof(page_id_t));
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WritePage(page_id, page_buf);
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first_empty_page_id = page_id;
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current_none_empty_page_count--;
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}
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size_t DiskManager::CurrentTotalPageCount() { return current_total_page_count; }
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size_t DiskManager::CurrentNoneEmptyPageCount() { return current_none_empty_page_count; } |