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use core::ptr::NonNull;
use crate::alloc::fmt::TryWrite;
use crate::alloc::{self, String};
use crate::runtime::VmResult;
use crate::Any;
/// A formatter for the rune virtual machine.
///
/// This is used as a receiver to functions implementing the [`DEBUG_FMT`]
/// and [`DISPLAY_FMT`] protocols.
///
/// [`DEBUG_FMT`]: crate::runtime::Protocol::DEBUG_FMT
/// [`DISPLAY_FMT`]: crate::runtime::Protocol::DISPLAY_FMT
#[derive(Any)]
#[rune(crate, item = ::std::fmt)]
pub struct Formatter {
pub(crate) out: NonNull<dyn TryWrite>,
pub(crate) buf: String,
}
impl Formatter {
/// Format onto the given trywrite.
pub(crate) fn format_with(
out: &mut String,
f: impl FnOnce(&mut Self) -> VmResult<()>,
) -> VmResult<()> {
// SAFETY: Call to this function ensures that the formatter does not
// outlive the passed in reference.
let mut fmt = Formatter {
out: NonNull::from(out),
buf: String::new(),
};
f(&mut fmt)
}
#[inline]
pub(crate) fn parts_mut(&mut self) -> (&mut dyn TryWrite, &str) {
// SAFETY: Formatter constrution requires `out` to be valid.
(unsafe { self.out.as_mut() }, &self.buf)
}
#[inline]
pub(crate) fn buf_mut(&mut self) -> &mut String {
&mut self.buf
}
}
impl TryWrite for Formatter {
#[inline]
fn try_write_str(&mut self, s: &str) -> alloc::Result<()> {
// SAFETY: Formatter constrution requires `out` to be valid.
unsafe { self.out.as_mut().try_write_str(s) }
}
#[inline]
fn try_write_char(&mut self, c: char) -> alloc::Result<()> {
// SAFETY: Formatter constrution requires `out` to be valid.
unsafe { self.out.as_mut().try_write_char(c) }
}
}