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A much simpler version of write
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nyurik committed Feb 20, 2024
1 parent 8362b30 commit 1eee9f5
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Showing 2 changed files with 10 additions and 28 deletions.
37 changes: 10 additions & 27 deletions library/core/src/fmt/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -201,22 +201,14 @@ pub trait Write {
impl<W: Write + ?Sized> SpecWriteFmt for &mut W {
#[inline]
default fn spec_write_fmt(mut self, args: Arguments<'_>) -> Result {
if let Some(s) = args.as_const_str() {
self.write_str(s)
} else {
write(&mut self, args)
}
write(&mut self, args)
}
}

impl<W: Write> SpecWriteFmt for &mut W {
#[inline]
fn spec_write_fmt(self, args: Arguments<'_>) -> Result {
if let Some(s) = args.as_const_str() {
self.write_str(s)
} else {
write(self, args)
}
write(self, args)
}
}

Expand Down Expand Up @@ -438,15 +430,6 @@ impl<'a> Arguments<'a> {
_ => None,
}
}

/// Same as [`Arguments::as_str`], but will only return `Some(s)` if it can be determined at compile time.
#[must_use]
#[inline]
fn as_const_str(&self) -> Option<&'static str> {
let s = self.as_str();
// SAFETY: both cases are valid as the result
if unsafe { core::intrinsics::is_val_statically_known(s.is_some()) } { s } else { None }
}
}

#[stable(feature = "rust1", since = "1.0.0")]
Expand Down Expand Up @@ -1119,8 +1102,14 @@ pub trait UpperExp {
/// ```
///
/// [`write!`]: crate::write!
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
if let Some(s) = args.as_str() { output.write_str(s) } else { write_internal(output, args) }
}

/// Actual implementation of the [`write`], but without the simple string optimization.
fn write_internal(output: &mut dyn Write, args: Arguments<'_>) -> Result {
let mut formatter = Formatter::new(output);
let mut idx = 0;

Expand Down Expand Up @@ -1599,9 +1588,8 @@ impl<'a> Formatter<'a> {
/// assert_eq!(format!("{:0>8}", Foo(2)), "Foo 2");
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result {
if let Some(s) = fmt.as_const_str() { self.buf.write_str(s) } else { write(self.buf, fmt) }
write(self.buf, fmt)
}

/// Flags for formatting
Expand Down Expand Up @@ -2290,13 +2278,8 @@ impl Write for Formatter<'_> {
self.buf.write_char(c)
}

#[inline]
fn write_fmt(&mut self, args: Arguments<'_>) -> Result {
if let Some(s) = args.as_const_str() {
self.buf.write_str(s)
} else {
write(self.buf, args)
}
write(self.buf, args)
}
}

Expand Down
1 change: 0 additions & 1 deletion library/core/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -176,7 +176,6 @@
#![feature(ip)]
#![feature(ip_bits)]
#![feature(is_ascii_octdigit)]
#![feature(is_val_statically_known)]
#![feature(isqrt)]
#![feature(maybe_uninit_uninit_array)]
#![feature(non_null_convenience)]
Expand Down

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