feat: expose user-friendly version of read_value!

proconio/src/lib.rs

@@ -682,18 +682,18 @@ macro_rules! input {
     };
 }
 
-/// read input from stdin interactively.
+/// Read input from specified source interactively.
 ///
-/// this macro is alias of:
+/// This macro is an alias of:
 /// ```text
-/// let source = procontio::source::line::LineSource::new(BufReader::new(std::io::stdin()))
+/// let source = procontio::source::line::LineSource::new(BufReader::new(std::io::stdin()));
 /// input! {
 ///     from &mut source,
 ///     (mut) variable: type,
 ///     ...
 /// }
 /// ```
-/// read the documet of [input!](input) for further information.
+/// read the document of [input!](input) for further information.
 #[macro_export]
 macro_rules! input_interactive {
     ($($rest:tt)*) => {
@@ -782,6 +782,38 @@ macro_rules! read_value {
     };
 }
 
+/// Interactive version of `read_value!` macro.
+///
+/// This macro is equivalent to do the following:
+///
+/// ```text
+/// let source = procontio::source::line::LineSource::new(BufReader::new(std::io::stdin()));
+/// let variable = read_value!(from &mut source, type);
+/// ```
+///
+/// Read the document of [read_value!](read_value) for further information.
+#[macro_export]
+macro_rules! read_value_interactive {
+    ($($rest:tt)*) => {
+        let mut locked_stdin = $crate::STDIN_SOURCE
+            .get_or_init(|| {
+                std::sync::Mutex::new($crate::StdinSource::Interactive(
+                    $crate::source::line::LineSource::new(std::io::BufReader::new(std::io::stdin())),
+                ))
+            })
+            .lock()
+            .expect(concat!(
+                "failed to lock the stdin; please re-run this program.  ",
+                "If this issue repeatedly occur, this is a bug in `proconio`.  ",
+                "Please report this issue from ",
+                "<https://github.com/statiolake/proconio-rs/issues>."
+            ));
+        let __res = $crate::read_value!(from &mut *locked_stdin, $($rest)*);
+        drop(locked_stdin); // release the lock
+        __res
+    };
+}
+
 /// Checks if some of tokens are left on stdin.
 ///
 /// This is useful when the number of test cases is not specified like ICPC problems.