write SwitchToSnapShot

dataguard/include/dataguard/snapshot.h

@@ -1,12 +1,19 @@
 #ifndef SNAP_SHOT_H
 #define SNAP_SHOT_H
+#include <spdlog/async.h>
+#include <spdlog/sinks/basic_file_sink.h>
+#include <spdlog/sinks/stdout_color_sinks.h>
+#include <spdlog/spdlog.h>
+#include <fstream>
 #include <string>
+#include "list.hpp"
 #include "map.hpp"
 #include "storage/driver.h"
 #include "vector.hpp"
 void GenerateDiff(const std::string &old_file, const std::string &new_file, const std::string &diff_file);
 void ApplyPatch(const std::string &old_file, const std::string &diff_file, const std::string &new_file,
                 bool is_reverse);
+void CopyFile(const std::string &src, const std::string &dst);
 /**
  * @brief SnapShotManager is a class to manage the snapshot of the data drivers.
  */
@@ -22,6 +29,87 @@ class SnapShotManager {
   bool has_set_meta_file = false;
   sjtu::vector<DataDriverBase *> drivers;
   std::string meta_file;
+  std::shared_ptr<spdlog::logger> logger_ptr;
+  struct WayEntry {
+    std::string snap_ID;
+    std::string diff_ID;
+    bool is_reverse;
+  };
+  friend void ApplyLongChange(const std::string &old_file, const std::string &new_file,
+                              const sjtu::vector<SnapShotManager::WayEntry> &way);
+  inline sjtu::vector<WayEntry> FindWay(std::string dest) {
+    if (!has_set_meta_file) {
+      throw std::runtime_error("SnapShotManager has not set the meta file");
+    }
+    if (!has_connected) {
+      throw std::runtime_error("SnapShotManager has not connected to the data drivers");
+    }
+    std::fstream fs(meta_file, std::ios::in);
+    std::string HEAD;
+    fs >> HEAD;
+    std::string cur, anc;
+    sjtu::map<std::string, sjtu::vector<std::string>> son_list;
+    sjtu::map<std::string, std::string> get_anc;
+    while (fs >> cur >> anc) {
+      son_list[anc].push_back(cur);
+      get_anc[cur] = anc;
+    }
+    if (son_list.find(dest) == son_list.end() && get_anc.find(dest) == get_anc.end()) {
+      throw std::runtime_error("unable to find destination");
+    }
+    sjtu::vector<WayEntry> res;
+    if (HEAD == dest) return res;
+    sjtu::list<std::string> Q;
+    sjtu::map<std::string, WayEntry> visit_record;
+    Q.push_back(dest);
+    while (!Q.empty()) {
+      std::string cur = Q.front();
+      Q.pop_front();
+      if (get_anc.find(cur) != get_anc.end()) {
+        std::string v = get_anc[cur];
+        if (visit_record.find(v) == visit_record.end()) {
+          visit_record[v] = {cur, cur, false};
+          if (v == HEAD) goto ed;
+          Q.push_back(v);
+        }
+      }
+      if (son_list.find(cur) != son_list.end()) {
+        auto &s_l = son_list[cur];
+        for (size_t j = 0; j < s_l.size(); j++) {
+          std::string v = s_l[j];
+          if (visit_record.find(v) == visit_record.end()) {
+            visit_record[v] = {cur, v, true};
+            if (v == HEAD) goto ed;
+            Q.push_back(v);
+          }
+        }
+      }
+    }
+  ed:;
+    std::string tmp = HEAD;
+    while (tmp != dest) {
+      res.push_back(visit_record[tmp]);
+      tmp = visit_record[tmp].snap_ID;
+    }
+    return res;
+  }
+  inline void ApplyLongChange(const std::string &old_file, const std::string &new_file,
+                              const sjtu::vector<SnapShotManager::WayEntry> &way, const std::string &file_name_base) {
+    CopyFile(old_file, new_file);
+    for (size_t i = 0; i < way.size(); i++) {
+      if (logger_ptr) {
+        logger_ptr->info("Applying diff {} to {} with inverse mark {}", file_name_base + "." + way[i].diff_ID + ".diff",
+                         new_file, way[i].is_reverse);
+      }
+      ApplyPatch(new_file, file_name_base + "." + way[i].diff_ID + ".diff", new_file + ".tmp", way[i].is_reverse);
+      remove(new_file.c_str());
+      rename((new_file + ".tmp").c_str(), new_file.c_str());
+      if (logger_ptr) {
+        logger_ptr->info("Applied diff {} to {} with inverse mark {}", file_name_base + "." + way[i].diff_ID + ".diff",
+                         new_file, way[i].is_reverse);
+      }
+    }
+  }
 
  public:
   // For safety and simplicity, we delete all the copy/move constructor and copy/move assignment operator. Please
@@ -42,6 +130,7 @@ class SnapShotManager {
     drivers = std::move(drivers_);
     has_connected = true;
   }
+  inline void SetLogger(const std::shared_ptr<spdlog::logger> &logger_ptr_) { logger_ptr = logger_ptr_; }
   inline void SetMetaFile(const std::string &meta_file_) {
     if (has_set_meta_file) throw std::runtime_error("SnapShotManager has already set the meta file");
     has_set_meta_file = true;
@@ -59,6 +148,7 @@ class SnapShotManager {
   }
   void InitializeRepository();
   void CreateSnapShot(const std::string &snap_shot_ID);
+  void CheckOutFrontier();
   void SwitchToSnapShot(const std::string &snap_shot_ID);
   void RemoveSnapShot(const std::string &snap_shot_ID);
 };