rune/runtime/
fmt.rs

1use core::ptr::NonNull;
2
3use crate::alloc::fmt::TryWrite;
4use crate::alloc::{self, String};
5use crate::Any;
6
7/// A formatter for the rune virtual machine.
8///
9/// This is used as a receiver to functions implementing the [`DEBUG_FMT`]
10/// and [`DISPLAY_FMT`] protocols.
11///
12/// [`DEBUG_FMT`]: crate::runtime::Protocol::DEBUG_FMT
13/// [`DISPLAY_FMT`]: crate::runtime::Protocol::DISPLAY_FMT
14#[derive(Any)]
15#[rune(crate, item = ::std::fmt)]
16pub struct Formatter {
17    pub(crate) out: NonNull<dyn TryWrite>,
18    pub(crate) buf: String,
19}
20
21impl Formatter {
22    /// Format onto the given trywrite.
23    pub(crate) fn format_with<E>(
24        out: &mut String,
25        f: impl FnOnce(&mut Self) -> Result<(), E>,
26    ) -> Result<(), E> {
27        // SAFETY: Call to this function ensures that the formatter does not
28        // outlive the passed in reference.
29        let mut fmt = Formatter {
30            out: NonNull::from(out),
31            buf: String::new(),
32        };
33        f(&mut fmt)
34    }
35
36    #[inline]
37    pub(crate) fn parts_mut(&mut self) -> (&mut dyn TryWrite, &str) {
38        // SAFETY: Formatter constrution requires `out` to be valid.
39        (unsafe { self.out.as_mut() }, &self.buf)
40    }
41
42    #[inline]
43    pub(crate) fn buf_mut(&mut self) -> &mut String {
44        &mut self.buf
45    }
46}
47
48impl TryWrite for Formatter {
49    #[inline]
50    fn try_write_str(&mut self, s: &str) -> alloc::Result<()> {
51        // SAFETY: Formatter constrution requires `out` to be valid.
52        unsafe { self.out.as_mut().try_write_str(s) }
53    }
54
55    #[inline]
56    fn try_write_char(&mut self, c: char) -> alloc::Result<()> {
57        // SAFETY: Formatter constrution requires `out` to be valid.
58        unsafe { self.out.as_mut().try_write_char(c) }
59    }
60}
rune/runtime/fmt.rs

rune/runtime/
fmt.rs
