Add 'third_party/nix/' from commit 'be66c7a6b24e3c3c6157fd37b86c7203d14acf10'

git-subtree-dir: third_party/nix
git-subtree-mainline: cf8cd640c1
git-subtree-split: be66c7a6b24e3c3c6157fd37b86c7203d14acf10

third_party/nix/src/libstore/sqlite.hh

@@ -0,0 +1,114 @@
+#pragma once
+
+#include <functional>
+#include <string>
+
+#include "types.hh"
+
+class sqlite3;
+class sqlite3_stmt;
+
+namespace nix {
+
+/* RAII wrapper to close a SQLite database automatically. */
+struct SQLite
+{
+    sqlite3 * db = 0;
+    SQLite() { }
+    SQLite(const Path & path);
+    SQLite(const SQLite & from) = delete;
+    SQLite& operator = (const SQLite & from) = delete;
+    SQLite& operator = (SQLite && from) { db = from.db; from.db = 0; return *this; }
+    ~SQLite();
+    operator sqlite3 * () { return db; }
+
+    void exec(const std::string & stmt);
+};
+
+/* RAII wrapper to create and destroy SQLite prepared statements. */
+struct SQLiteStmt
+{
+    sqlite3 * db = 0;
+    sqlite3_stmt * stmt = 0;
+    std::string sql;
+    SQLiteStmt() { }
+    SQLiteStmt(sqlite3 * db, const std::string & sql) { create(db, sql); }
+    void create(sqlite3 * db, const std::string & s);
+    ~SQLiteStmt();
+    operator sqlite3_stmt * () { return stmt; }
+
+    /* Helper for binding / executing statements. */
+    class Use
+    {
+        friend struct SQLiteStmt;
+    private:
+        SQLiteStmt & stmt;
+        unsigned int curArg = 1;
+        Use(SQLiteStmt & stmt);
+
+    public:
+
+        ~Use();
+
+        /* Bind the next parameter. */
+        Use & operator () (const std::string & value, bool notNull = true);
+        Use & operator () (int64_t value, bool notNull = true);
+        Use & bind(); // null
+
+        int step();
+
+        /* Execute a statement that does not return rows. */
+        void exec();
+
+        /* For statements that return 0 or more rows. Returns true iff
+           a row is available. */
+        bool next();
+
+        std::string getStr(int col);
+        int64_t getInt(int col);
+        bool isNull(int col);
+    };
+
+    Use use()
+    {
+        return Use(*this);
+    }
+};
+
+/* RAII helper that ensures transactions are aborted unless explicitly
+   committed. */
+struct SQLiteTxn
+{
+    bool active = false;
+    sqlite3 * db;
+
+    SQLiteTxn(sqlite3 * db);
+
+    void commit();
+
+    ~SQLiteTxn();
+};
+
+
+MakeError(SQLiteError, Error);
+MakeError(SQLiteBusy, SQLiteError);
+
+[[noreturn]] void throwSQLiteError(sqlite3 * db, const FormatOrString & fs);
+
+void handleSQLiteBusy(const SQLiteBusy & e);
+
+/* Convenience function for retrying a SQLite transaction when the
+   database is busy. */
+template<typename T>
+T retrySQLite(std::function<T()> fun)
+{
+    while (true) {
+        try {
+            return fun();
+        } catch (SQLiteBusy & e) {
+            handleSQLiteBusy(e);
+        }
+    }
+}
+
+}