MXS-2544 Add utility class for handling SQLite

Preparation and cleanup for adding more data to handle user roles in PAM
authenticator.

server/modules/authenticator/PAM/PAMAuth/pam_auth.cc

@@ -15,6 +15,7 @@
 #include <string>
 #include <maxscale/authenticator.hh>
 #include <maxscale/users.h>
+#include <maxbase/format.hh>
 
 #include "pam_instance.hh"
 #include "pam_client_session.hh"
@@ -32,6 +33,79 @@ const int NUM_FIELDS = 6;
 const char* SQLITE_OPEN_FAIL = "Failed to open SQLite3 handle for file '%s': '%s'";
 const char* SQLITE_OPEN_OOM = "Failed to allocate memory for SQLite3 handle for file '%s'.";
 
+using SSQLite = SQLite::SSQLite;
+
+SSQLite SQLite::create(const string& filename, int flags, string* error_out)
+{
+    SSQLite rval;
+    sqlite3* dbhandle = nullptr;
+    const char* zFilename = filename.c_str();
+    int ret = sqlite3_open_v2(zFilename, &dbhandle, flags, NULL);
+    string error_msg;
+    if (ret == SQLITE_OK)
+    {
+        rval.reset(new SQLite(dbhandle));
+    }
+    // Even if the open failed, the handle may exist and an error message can be read.
+    else if (dbhandle)
+    {
+        error_msg = mxb::string_printf(SQLITE_OPEN_FAIL, zFilename, sqlite3_errmsg(dbhandle));
+        sqlite3_close_v2(dbhandle);
+    }
+    else
+    {
+        error_msg = mxb::string_printf(SQLITE_OPEN_OOM, zFilename);
+    }
+
+    if (!error_msg.empty() && error_out)
+    {
+        *error_out = error_msg;
+    }
+    return rval;
+}
+
+SQLite::SQLite(sqlite3* handle)
+    : m_dbhandle(handle)
+{
+    mxb_assert(handle);
+}
+
+SQLite::~SQLite()
+{
+    sqlite3_close_v2(m_dbhandle);
+}
+
+bool SQLite::exec(const std::string& sql)
+{
+    return exec_impl(sql, nullptr, nullptr);
+}
+
+bool SQLite::exec_impl(const std::string& sql, CallbackVoid cb, void* cb_data)
+{
+    char* err = nullptr;
+    bool success = (sqlite3_exec(m_dbhandle, sql.c_str(), cb, cb_data, &err) == SQLITE_OK);
+    if (success)
+    {
+        m_errormsg.clear();
+    }
+    else
+    {
+        m_errormsg = err;
+        sqlite3_free(err);
+    }
+    return success;
+}
+
+void SQLite::set_timeout(int ms)
+{
+    sqlite3_busy_timeout(m_dbhandle, ms);
+}
+
+const char* SQLite::error() const
+{
+    return m_errormsg.c_str();
+}
+
 /**
  * Initialize PAM authenticator
  *