nix/libstore/sqlite.hh

   1 #pragma once
   2
   3 #include <functional>
   4 #include <string>
   5
   6 #include "types.hh"
   7
   8 class sqlite3;
   9 class sqlite3_stmt;
  10
  11 namespace nix {
  12
  13 /* RAII wrapper to close a SQLite database automatically. */
  14 struct SQLite
  15 {
  16     sqlite3 * db;
  17     SQLite() { db = 0; }
  18     ~SQLite();
  19     operator sqlite3 * () { return db; }
  20 };
  21
  22 /* RAII wrapper to create and destroy SQLite prepared statements. */
  23 struct SQLiteStmt
  24 {
  25     sqlite3 * db = 0;
  26     sqlite3_stmt * stmt = 0;
  27     SQLiteStmt() { }
  28     void create(sqlite3 * db, const std::string & s);
  29     ~SQLiteStmt();
  30     operator sqlite3_stmt * () { return stmt; }
  31
  32     /* Helper for binding / executing statements. */
  33     class Use
  34     {
  35         friend struct SQLiteStmt;
  36     private:
  37         SQLiteStmt & stmt;
  38         unsigned int curArg = 1;
  39         Use(SQLiteStmt & stmt);
  40
  41     public:
  42
  43         ~Use();
  44
  45         /* Bind the next parameter. */
  46         Use & operator () (const std::string & value, bool notNull = true);
  47         Use & operator () (int64_t value, bool notNull = true);
  48         Use & bind(); // null
  49
  50         int step();
  51
  52         /* Execute a statement that does not return rows. */
  53         void exec();
  54
  55         /* For statements that return 0 or more rows. Returns true iff
  56            a row is available. */
  57         bool next();
  58
  59         std::string getStr(int col);
  60         int64_t getInt(int col);
  61     };
  62
  63     Use use()
  64     {
  65         return Use(*this);
  66     }
  67 };
  68
  69 /* RAII helper that ensures transactions are aborted unless explicitly
  70    committed. */
  71 struct SQLiteTxn
  72 {
  73     bool active = false;
  74     sqlite3 * db;
  75
  76     SQLiteTxn(sqlite3 * db);
  77
  78     void commit();
  79
  80     ~SQLiteTxn();
  81 };
  82
  83
  84 MakeError(SQLiteError, Error);
  85 MakeError(SQLiteBusy, SQLiteError);
  86
  87 [[noreturn]] void throwSQLiteError(sqlite3 * db, const format & f);
  88
  89 /* Convenience function for retrying a SQLite transaction when the
  90    database is busy. */
  91 template<typename T>
  92 T retrySQLite(std::function<T()> fun)
  93 {
  94     while (true) {
  95         try {
  96             return fun();
  97         } catch (SQLiteBusy & e) {
  98         }
  99     }
 100 }
 101
 102 }