Add a dummy utility to demonstrate the framework

Author: Mingshen Sun

Cargo.toml

@@ -60,6 +60,12 @@ sysinit = [
     "init"
 ]
 
+# a dummy utility to help people to understand the framework
+dummy = ["libmesabox/dummy"]
+other = [
+    "dummy"
+]
+
 # utilities that work on Unix
 unix = [
     "gnu",

libmesabox/Cargo.toml

@@ -58,6 +58,12 @@ sysinit = [
     "init"
 ]
 
+# a dummy utility to help people to understand the framework
+dummy = []
+other = [
+    "dummy"
+]
+
 # utilities that work on Unix
 unix = [
     "gnu",

libmesabox/src/other/dummy.rs

@@ -0,0 +1,53 @@
+//
+// Copyright (c) 2018, The MesaLock Linux Project Contributors
+// All rights reserved.
+//
+// This work is licensed under the terms of the BSD 3-Clause License.
+// For a copy, see the LICENSE file.
+//
+
+use {UtilSetup, ArgsIter, Result, UtilRead, UtilWrite};
+use std::io::{self, Write};
+
+pub const DESCRIPTION: &str = "A dummy utility to demonstrate the framework";
+
+#[derive(Fail, Debug)]
+enum DummyError {
+    #[fail(display = "something wrong")]
+    SomethingWrong
+}
+
+type DummyResult<T> = ::std::result::Result<T, DummyError>;
+
+struct Dummyer<O>
+where
+    O: Write
+{
+    output: O
+}
+
+impl<O> Dummyer<O>
+where
+    O: Write
+{
+    fn new(output: O) -> Self {
+        Dummyer { output }
+    }
+
+    fn dummy(&mut self) -> DummyResult<()> {
+        writeln!(self.output, "write something to the output");
+        Ok(())
+    }
+}
+
+pub fn execute<S, T>(setup: &mut S, _args: T) -> Result<()>
+where
+    S: UtilSetup,
+    T: ArgsIter,
+{
+    let output = setup.output();
+    let mut output = output.lock()?;
+    let mut dummyer = Dummyer::new(output);
+    dummyer.dummy()?;
+    Ok(())
+}

libmesabox/src/util_list.rs

@@ -27,5 +27,8 @@ generate_fns! {
     },
     sysinit {
         (init, "init")
+    },
+    other {
+        (dummy, "dummy")
     }
 }