Factor out .test-reading capability

The capability for reading MySQL/MariaDB .test-files has now been
factored out from the compare.cc test program. That way, the
functionality can be used from other test programs as well.

query_classifier/test/testreader.hh

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl.
+ *
+ * Change Date: 2019-07-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/cppdefs.hh>
+#include <istream>
+
+namespace maxscale
+{
+
+/**
+ * @class TestReader
+ *
+ * The TestReader class is capable of reading a MySQL/MariaDB test file,
+ * such like the ones in [MySQL|MariaDB]/server/mysql-test/t, and return
+ * the SQL statements one by one. It does this by skipping test commands
+ * and by coalescing lines to obtain a full statement.
+ */
+class TestReader
+{
+public:
+    enum result_t
+    {
+        RESULT_ERROR, /*< The input is probably not a test file. */
+        RESULT_EOF,   /*< End of file was reached. */
+        RESULT_STMT,  /*< A statement was returned. */
+    };
+
+    /**
+     * Initialize internal shared tables. This will automatically be called
+     * by the TestReader constructor, but if multiple threads are used it
+     * is adviseable to call this function explicitly from the main thread.
+     */
+    static void init();
+
+
+    /**
+     * Creates a TestReader instance.
+     *
+     * @param in    An input stream.
+     * @param line  Optionally specify the initial line number.
+     */
+    TestReader(std::istream& in,
+               size_t        line = 0);
+
+    /**
+     * @return The current line number.
+     */
+    size_t line() const { return m_line; }
+
+    /**
+     * Get next full SQL statement.
+     *
+     * @param stmt  String where statement will be stored.
+     *
+     * @return RESULT_STMT if a statement was returned in @c stmt.
+     */
+    result_t get_statement(std::string& stmt);
+
+private:
+    void skip_block();
+
+private:
+    TestReader(const TestReader&);
+    TestReader& operator = (const TestReader&);
+
+private:
+    std::istream& m_in;        /*< The stream we are using. */
+    size_t        m_line;      /*< The current line. */
+    char          m_delimiter; /*< The current delimiter. */
+};
+
+};