From 265a7cc3bde71bf34f6b2cfea6353ede20bfd7a5 Mon Sep 17 00:00:00 2001 From: Simon Sapin Date: Tue, 21 Apr 2015 14:51:28 +0200 Subject: [PATCH] Add a `write_char` method to `std::fmt::Write` as accepted in [RFC 526](https://github.com/rust-lang/rfcs/blob/master/text/0526-fmt-text-writer.md). --- src/libcollections/string.rs | 6 ++++++ src/libcore/fmt/mod.rs | 17 +++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/src/libcollections/string.rs b/src/libcollections/string.rs index 81710286fde2..11d32dbd94a9 100644 --- a/src/libcollections/string.rs +++ b/src/libcollections/string.rs @@ -1084,4 +1084,10 @@ impl fmt::Write for String { self.push_str(s); Ok(()) } + + #[inline] + fn write_char(&mut self, c: char) -> fmt::Result { + self.push(c); + Ok(()) + } } diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs index 80c661b260cb..85226444e841 100644 --- a/src/libcore/fmt/mod.rs +++ b/src/libcore/fmt/mod.rs @@ -83,6 +83,23 @@ pub trait Write { #[stable(feature = "rust1", since = "1.0.0")] fn write_str(&mut self, s: &str) -> Result; + /// Writes a `char` into this writer, returning whether the write succeeded. + /// + /// A single `char` may be encoded as more than one byte. + /// This method can only succeed if the entire byte sequence was successfully + /// written, and this method will not return until all data has been + /// written or an error occurs. + /// + /// # Errors + /// + /// This function will return an instance of `FormatError` on error. + #[stable(feature = "rust1", since = "1.0.0")] + fn write_char(&mut self, c: char) -> Result { + let mut utf_8 = [0u8; 4]; + let bytes_written = c.encode_utf8(&mut utf_8).unwrap_or(0); + self.write_str(unsafe { mem::transmute(&utf_8[..bytes_written]) }) + } + /// Glue for usage of the `write!` macro with implementers of this trait. /// /// This method should generally not be invoked manually, but rather through