refactored

storage/src/disk_manager.cpp

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