`StackString<SIZE>`: Added `fmt::Write`, `io::Write` impls

`StackString<SIZE>`: Added `fmt::Display` impl

Fortune for stack-str's current commit: Middle blessing − 中吉

src/lib.rs

@@ -283,3 +283,57 @@ impl<const SIZE: usize> TryFrom<[u8; SIZE]> for StackString<SIZE>
 	Self::try_from_utf8_array(from)
     }
 }
+
+impl<const SIZE: usize> fmt::Display for StackString<SIZE>
+{
+    #[inline] 
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result
+    {
+	f.write_str(self.as_str())
+    }
+}
+
+
+impl<const SIZE: usize> fmt::Write for StackString<SIZE>
+{
+    #[inline] 
+    fn write_str(&mut self, s: &str) -> fmt::Result {
+	self.try_append_whole_str(s).map_err(|_| fmt::Error::default())?;
+	Ok(())
+    }
+    #[inline] 
+    fn write_char(&mut self, c: char) -> fmt::Result {
+	let l = c.len_utf8();
+	if l > self.available() {
+	    Err(fmt::Error::default())
+	} else {
+	    let end = self.fill_ptr;
+	    let end = c.encode_utf8(&mut (self.as_raw_buf_mut())[end..]).len();
+	    self.fill_ptr += end;
+	    Ok(())
+	}
+    }
+}
+
+const _: () = {
+    use std::io::{
+	self,Write
+    };
+    impl<const SIZE: usize> Write for StackString<SIZE>
+    {
+	#[inline] 
+	fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
+	    let buf = std::str::from_utf8(buf).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+	    Ok(self.append_from_str(buf))
+	}
+	#[inline] 
+	fn flush(&mut self) -> io::Result<()> {
+	    Ok(())
+	}
+	#[inline] 
+	fn write_all(&mut self, buf: &[u8]) -> io::Result<()> {
+	    let buf = std::str::from_utf8(buf).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))?;
+	    self.try_append_whole_str(buf).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e)).map(|_| ())
+	}
+    }
+};