add io::stdio

Signed-off-by: Yoshua Wuyts <yoshuawuyts@gmail.com>

src/io/mod.rs

@@ -55,5 +55,6 @@ mod repeat;
 mod sink;
 mod stderr;
 mod stdin;
+mod stdio;
 mod stdout;
 mod timeout;

src/io/stdio.rs

@@ -0,0 +1,29 @@
+//! Internal types for stdio.
+//!
+//! This module is a port of `libstd/io/stdio.rs`,and contains internal types for `print`/`eprint`.
+
+use crate::io::{stderr, stdout, Write};
+use std::fmt;
+
+/// Write `args` `global_s`. `label` identifies the stream in a panic message.
+async fn print_to<T>(
+    args: fmt::Arguments<'_>,
+    global_s: fn() -> T,
+    label: &str,
+) where
+    T: Write,
+{
+    if let Err(e) = global_s().write_fmt(args).await {
+        panic!("failed printing to {}: {}", label, e);
+    }
+}
+
+#[doc(hidden)]
+pub async fn _print(args: fmt::Arguments<'_>) {
+    print_to(args, stdout, "stdout");
+}
+
+#[doc(hidden)]
+pub async fn _eprint(args: fmt::Arguments<'_>) {
+    print_to(args, stderr, "stderr");
+}

src/lib.rs

@@ -76,6 +76,7 @@ cfg_if! {
     }
 }
 
+mod macros;
 pub(crate) mod utils;
 
 #[doc(inline)]

src/macros.rs

@@ -0,0 +1,43 @@
+/// Prints to the standard output.
+///
+/// Equivalent to the [`println!`] macro except that a newline is not printed at
+/// the end of the message.
+///
+/// Note that stdout is frequently line-buffered by default so it may be
+/// necessary to use [`io::stdout().flush()`][flush] to ensure the output is emitted
+/// immediately.
+///
+/// Use `print!` only for the primary output of your program. Use
+/// [`eprint!`] instead to print error and progress messages.
+///
+/// [`println!`]: macro.println.html
+/// [flush]: io/trait.Write.html#tymethod.flush
+/// [`eprint!`]: macro.eprint.html
+///
+/// # Panics
+///
+/// Panics if writing to `io::stdout()` fails.
+///
+/// # Examples
+///
+/// ```
+/// use std::io::{self, Write};
+///
+/// print!("this ");
+/// print!("will ");
+/// print!("be ");
+/// print!("on ");
+/// print!("the ");
+/// print!("same ");
+/// print!("line ");
+///
+/// io::stdout().flush().unwrap();
+///
+/// print!("this string has a newline, why not choose println! instead?\n");
+///
+/// io::stdout().flush().unwrap();
+/// ```
+#[macro_export]
+macro_rules! print {
+    ($($arg:tt)*) => ($crate::io::_print(format_args!($($arg)*)));
+}