Add mbcheck.

lib/mbtiles.js

@@ -34,6 +34,17 @@ MBTiles.prototype.exists = function(table, callback) {
     }
 };
 
+// DB integrity check.
+MBTiles.prototype.integrity = function(callback) {
+    this.db.get('PRAGMA quick_check(1)', function(err, row) {
+        if (!(row && row.integrity_check && row.integrity_check === 'ok')) {
+            callback(new Error('Corrupted database.'));
+        } else {
+            callback(null, true);
+        }
+    });
+};
+
 // Setup schema, indices, views for a new mbtiles database.
 // Sets the synchronous flag to OFF for (much) faster inserts.
 // See http://www.sqlite3.org/pragma.html#pragma_synchronous