feat: add mysql svr

__database/mysqlsvr/src/backend.rs

@@ -0,0 +1,49 @@
+use std::io;
+use msql_srv::*;
+
+pub struct Backend;
+impl<W: io::Write> MysqlShim<W> for Backend {
+    type Error = io::Error;
+
+    fn on_prepare(&mut self, query: &str, info: StatementMetaWriter<W>) -> io::Result<()> {
+        println!("Backend on prepare, query: {}", query);
+        info.reply(42, &[], &[])
+    }
+
+    fn on_execute(&mut self, id: u32, _params: ParamParser, results: QueryResultWriter<W>, ) -> io::Result<()> {
+        println!("Backend on execute, id: {}", id);
+        results.completed(0, 0)
+    }
+
+    fn on_close(&mut self, stmt: u32) {
+        println!("Backend on close, stmt: {}", stmt);
+    }
+
+    fn on_init(&mut self, _unknown: &str, _writer: InitWriter<W>) -> io::Result<()> {
+        println!("Backend on init, param2: {}", _unknown);
+        Ok(())
+    }
+
+    fn on_query(&mut self, query: &str, results: QueryResultWriter<W>) -> io::Result<()> {
+        println!("Backend on query, query: {}", query);
+        let cols = [
+            Column {
+                table: "foo".to_string(),
+                column: "a".to_string(),
+                coltype: ColumnType::MYSQL_TYPE_LONGLONG,
+                colflags: ColumnFlags::empty(),
+            },
+            Column {
+                table: "foo".to_string(),
+                column: "b".to_string(),
+                coltype: ColumnType::MYSQL_TYPE_STRING,
+                colflags: ColumnFlags::empty(),
+            },
+        ];
+
+        let mut rw = results.start(&cols)?;
+        rw.write_col(42)?;
+        rw.write_col("b's value")?;
+        rw.finish()
+    }
+}