2280 lines
70 KiB
Rust
2280 lines
70 KiB
Rust
//! Utilities for formatting and printing strings.
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#![stable(feature = "rust1", since = "1.0.0")]
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use crate::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
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use crate::char::EscapeDebugExtArgs;
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use crate::iter;
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use crate::marker::PhantomData;
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use crate::mem;
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use crate::num::flt2dec;
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use crate::ops::Deref;
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use crate::result;
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use crate::str;
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mod builders;
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mod float;
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mod num;
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#[stable(feature = "fmt_flags_align", since = "1.28.0")]
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/// Possible alignments returned by `Formatter::align`
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#[derive(Debug)]
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pub enum Alignment {
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#[stable(feature = "fmt_flags_align", since = "1.28.0")]
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/// Indication that contents should be left-aligned.
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Left,
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#[stable(feature = "fmt_flags_align", since = "1.28.0")]
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/// Indication that contents should be right-aligned.
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Right,
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#[stable(feature = "fmt_flags_align", since = "1.28.0")]
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/// Indication that contents should be center-aligned.
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Center,
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}
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#[stable(feature = "debug_builders", since = "1.2.0")]
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pub use self::builders::{DebugList, DebugMap, DebugSet, DebugStruct, DebugTuple};
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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#[doc(hidden)]
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pub mod rt {
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pub mod v1;
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}
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/// The type returned by formatter methods.
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///
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/// # Examples
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///
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/// ```
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/// use std::fmt;
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///
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/// #[derive(Debug)]
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/// struct Triangle {
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/// a: f32,
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/// b: f32,
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/// c: f32
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/// }
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///
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/// impl fmt::Display for Triangle {
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/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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/// write!(f, "({}, {}, {})", self.a, self.b, self.c)
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/// }
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/// }
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///
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/// let pythagorean_triple = Triangle { a: 3.0, b: 4.0, c: 5.0 };
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///
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/// assert_eq!(format!("{}", pythagorean_triple), "(3, 4, 5)");
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub type Result = result::Result<(), Error>;
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/// The error type which is returned from formatting a message into a stream.
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///
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/// This type does not support transmission of an error other than that an error
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/// occurred. Any extra information must be arranged to be transmitted through
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/// some other means.
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///
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/// An important thing to remember is that the type `fmt::Error` should not be
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/// confused with [`std::io::Error`] or [`std::error::Error`], which you may also
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/// have in scope.
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///
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/// [`std::io::Error`]: ../../std/io/struct.Error.html
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/// [`std::error::Error`]: ../../std/error/trait.Error.html
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///
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/// # Examples
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///
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/// ```rust
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/// use std::fmt::{self, write};
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///
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/// let mut output = String::new();
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/// if let Err(fmt::Error) = write(&mut output, format_args!("Hello {}!", "world")) {
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/// panic!("An error occurred");
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/// }
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
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pub struct Error;
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/// A trait for writing or formatting into Unicode-accepting buffers or streams.
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///
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/// This trait only accepts UTF-8–encoded data and is not [flushable]. If you only
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/// want to accept Unicode and you don't need flushing, you should implement this trait;
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/// otherwise you should implement [`std::io::Write`].
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///
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/// [`std::io::Write`]: ../../std/io/trait.Write.html
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/// [flushable]: ../../std/io/trait.Write.html#tymethod.flush
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#[stable(feature = "rust1", since = "1.0.0")]
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pub trait Write {
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/// Writes a string slice into this writer, returning whether the write
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/// succeeded.
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///
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/// This method can only succeed if the entire string slice was successfully
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/// written, and this method will not return until all data has been
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/// written or an error occurs.
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///
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/// # Errors
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///
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/// This function will return an instance of [`Error`] on error.
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///
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/// # Examples
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///
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/// ```
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/// use std::fmt::{Error, Write};
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///
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/// fn writer<W: Write>(f: &mut W, s: &str) -> Result<(), Error> {
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/// f.write_str(s)
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/// }
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///
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/// let mut buf = String::new();
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/// writer(&mut buf, "hola").unwrap();
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/// assert_eq!(&buf, "hola");
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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fn write_str(&mut self, s: &str) -> Result;
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/// Writes a [`char`] into this writer, returning whether the write succeeded.
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///
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/// A single [`char`] may be encoded as more than one byte.
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/// This method can only succeed if the entire byte sequence was successfully
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/// written, and this method will not return until all data has been
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/// written or an error occurs.
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///
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/// # Errors
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///
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/// This function will return an instance of [`Error`] on error.
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///
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/// # Examples
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///
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/// ```
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/// use std::fmt::{Error, Write};
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///
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/// fn writer<W: Write>(f: &mut W, c: char) -> Result<(), Error> {
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/// f.write_char(c)
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/// }
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///
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/// let mut buf = String::new();
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/// writer(&mut buf, 'a').unwrap();
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/// writer(&mut buf, 'b').unwrap();
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/// assert_eq!(&buf, "ab");
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/// ```
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#[stable(feature = "fmt_write_char", since = "1.1.0")]
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fn write_char(&mut self, c: char) -> Result {
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self.write_str(c.encode_utf8(&mut [0; 4]))
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}
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/// Glue for usage of the [`write!`] macro with implementors of this trait.
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///
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/// This method should generally not be invoked manually, but rather through
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/// the [`write!`] macro itself.
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///
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/// # Examples
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///
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/// ```
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/// use std::fmt::{Error, Write};
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///
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/// fn writer<W: Write>(f: &mut W, s: &str) -> Result<(), Error> {
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/// f.write_fmt(format_args!("{}", s))
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/// }
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///
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/// let mut buf = String::new();
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/// writer(&mut buf, "world").unwrap();
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/// assert_eq!(&buf, "world");
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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fn write_fmt(mut self: &mut Self, args: Arguments<'_>) -> Result {
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write(&mut self, args)
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}
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}
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#[stable(feature = "fmt_write_blanket_impl", since = "1.4.0")]
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impl<W: Write + ?Sized> Write for &mut W {
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fn write_str(&mut self, s: &str) -> Result {
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(**self).write_str(s)
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}
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fn write_char(&mut self, c: char) -> Result {
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(**self).write_char(c)
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}
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fn write_fmt(&mut self, args: Arguments<'_>) -> Result {
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(**self).write_fmt(args)
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}
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}
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/// Configuration for formatting.
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///
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/// A `Formatter` represents various options related to formatting. Users do not
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/// construct `Formatter`s directly; a mutable reference to one is passed to
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/// the `fmt` method of all formatting traits, like [`Debug`] and [`Display`].
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///
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/// To interact with a `Formatter`, you'll call various methods to change the
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/// various options related to formatting. For examples, please see the
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/// documentation of the methods defined on `Formatter` below.
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#[allow(missing_debug_implementations)]
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#[stable(feature = "rust1", since = "1.0.0")]
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pub struct Formatter<'a> {
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flags: u32,
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fill: char,
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align: rt::v1::Alignment,
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width: Option<usize>,
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precision: Option<usize>,
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buf: &'a mut (dyn Write + 'a),
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}
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// NB. Argument is essentially an optimized partially applied formatting function,
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// equivalent to `exists T.(&T, fn(&T, &mut Formatter<'_>) -> Result`.
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extern "C" {
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type Opaque;
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}
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/// This struct represents the generic "argument" which is taken by the Xprintf
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/// family of functions. It contains a function to format the given value. At
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/// compile time it is ensured that the function and the value have the correct
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/// types, and then this struct is used to canonicalize arguments to one type.
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#[derive(Copy, Clone)]
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#[allow(missing_debug_implementations)]
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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#[doc(hidden)]
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pub struct ArgumentV1<'a> {
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value: &'a Opaque,
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formatter: fn(&Opaque, &mut Formatter<'_>) -> Result,
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}
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// This guarantees a single stable value for the function pointer associated with
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// indices/counts in the formatting infrastructure.
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//
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// Note that a function defined as such would not be correct as functions are
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// always tagged unnamed_addr with the current lowering to LLVM IR, so their
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// address is not considered important to LLVM and as such the as_usize cast
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// could have been miscompiled. In practice, we never call as_usize on non-usize
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// containing data (as a matter of static generation of the formatting
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// arguments), so this is merely an additional check.
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//
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// We primarily want to ensure that the function pointer at `USIZE_MARKER` has
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// an address corresponding *only* to functions that also take `&usize` as their
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// first argument. The read_volatile here ensures that we can safely ready out a
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// usize from the passed reference and that this address does not point at a
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// non-usize taking function.
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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static USIZE_MARKER: fn(&usize, &mut Formatter<'_>) -> Result = |ptr, _| {
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// SAFETY: ptr is a reference
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let _v: usize = unsafe { crate::ptr::read_volatile(ptr) };
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loop {}
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};
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impl<'a> ArgumentV1<'a> {
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#[doc(hidden)]
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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pub fn new<'b, T>(x: &'b T, f: fn(&T, &mut Formatter<'_>) -> Result) -> ArgumentV1<'b> {
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// SAFETY: `mem::transmute(x)` is safe because
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// 1. `&'b T` keeps the lifetime it originated with `'b`
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// (so as to not have an unbounded lifetime)
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// 2. `&'b T` and `&'b Opaque` have the same memory layout
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// (when `T` is `Sized`, as it is here)
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// `mem::transmute(f)` is safe since `fn(&T, &mut Formatter<'_>) -> Result`
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// and `fn(&Opaque, &mut Formatter<'_>) -> Result` have the same ABI
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// (as long as `T` is `Sized`)
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unsafe { ArgumentV1 { formatter: mem::transmute(f), value: mem::transmute(x) } }
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}
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#[doc(hidden)]
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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pub fn from_usize(x: &usize) -> ArgumentV1<'_> {
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ArgumentV1::new(x, USIZE_MARKER)
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}
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fn as_usize(&self) -> Option<usize> {
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if self.formatter as usize == USIZE_MARKER as usize {
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// SAFETY: The `formatter` field is only set to USIZE_MARKER if
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// the value is a usize, so this is safe
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Some(unsafe { *(self.value as *const _ as *const usize) })
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} else {
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None
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}
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}
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}
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// flags available in the v1 format of format_args
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#[derive(Copy, Clone)]
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enum FlagV1 {
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SignPlus,
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SignMinus,
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Alternate,
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SignAwareZeroPad,
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DebugLowerHex,
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DebugUpperHex,
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}
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impl<'a> Arguments<'a> {
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/// When using the format_args!() macro, this function is used to generate the
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/// Arguments structure.
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#[doc(hidden)]
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#[inline]
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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pub fn new_v1(pieces: &'a [&'static str], args: &'a [ArgumentV1<'a>]) -> Arguments<'a> {
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Arguments { pieces, fmt: None, args }
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}
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/// This function is used to specify nonstandard formatting parameters.
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/// The `pieces` array must be at least as long as `fmt` to construct
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/// a valid Arguments structure. Also, any `Count` within `fmt` that is
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/// `CountIsParam` or `CountIsNextParam` has to point to an argument
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/// created with `argumentusize`. However, failing to do so doesn't cause
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/// unsafety, but will ignore invalid .
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#[doc(hidden)]
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#[inline]
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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pub fn new_v1_formatted(
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pieces: &'a [&'static str],
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args: &'a [ArgumentV1<'a>],
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fmt: &'a [rt::v1::Argument],
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) -> Arguments<'a> {
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Arguments { pieces, fmt: Some(fmt), args }
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}
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/// Estimates the length of the formatted text.
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///
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/// This is intended to be used for setting initial `String` capacity
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/// when using `format!`. Note: this is neither the lower nor upper bound.
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#[doc(hidden)]
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#[inline]
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#[unstable(feature = "fmt_internals", reason = "internal to format_args!", issue = "none")]
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pub fn estimated_capacity(&self) -> usize {
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let pieces_length: usize = self.pieces.iter().map(|x| x.len()).sum();
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if self.args.is_empty() {
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pieces_length
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} else if self.pieces[0] == "" && pieces_length < 16 {
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// If the format string starts with an argument,
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// don't preallocate anything, unless length
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// of pieces is significant.
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0
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} else {
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// There are some arguments, so any additional push
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// will reallocate the string. To avoid that,
|
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// we're "pre-doubling" the capacity here.
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pieces_length.checked_mul(2).unwrap_or(0)
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}
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}
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}
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|
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/// This structure represents a safely precompiled version of a format string
|
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/// and its arguments. This cannot be generated at runtime because it cannot
|
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/// safely be done, so no constructors are given and the fields are private
|
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/// to prevent modification.
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///
|
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/// The [`format_args!`] macro will safely create an instance of this structure.
|
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/// The macro validates the format string at compile-time so usage of the
|
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/// [`write()`] and [`format()`] functions can be safely performed.
|
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///
|
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/// You can use the `Arguments<'a>` that [`format_args!`] returns in `Debug`
|
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/// and `Display` contexts as seen below. The example also shows that `Debug`
|
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/// and `Display` format to the same thing: the interpolated format string
|
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/// in `format_args!`.
|
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///
|
||
/// ```rust
|
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/// let debug = format!("{:?}", format_args!("{} foo {:?}", 1, 2));
|
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/// let display = format!("{}", format_args!("{} foo {:?}", 1, 2));
|
||
/// assert_eq!("1 foo 2", display);
|
||
/// assert_eq!(display, debug);
|
||
/// ```
|
||
///
|
||
/// [`format()`]: ../../std/fmt/fn.format.html
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[derive(Copy, Clone)]
|
||
pub struct Arguments<'a> {
|
||
// Format string pieces to print.
|
||
pieces: &'a [&'static str],
|
||
|
||
// Placeholder specs, or `None` if all specs are default (as in "{}{}").
|
||
fmt: Option<&'a [rt::v1::Argument]>,
|
||
|
||
// Dynamic arguments for interpolation, to be interleaved with string
|
||
// pieces. (Every argument is preceded by a string piece.)
|
||
args: &'a [ArgumentV1<'a>],
|
||
}
|
||
|
||
impl<'a> Arguments<'a> {
|
||
/// Get the formatted string, if it has no arguments to be formatted.
|
||
///
|
||
/// This can be used to avoid allocations in the most trivial case.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt::Arguments;
|
||
///
|
||
/// fn write_str(_: &str) { /* ... */ }
|
||
///
|
||
/// fn write_fmt(args: &Arguments) {
|
||
/// if let Some(s) = args.as_str() {
|
||
/// write_str(s)
|
||
/// } else {
|
||
/// write_str(&args.to_string());
|
||
/// }
|
||
/// }
|
||
/// ```
|
||
///
|
||
/// ```rust
|
||
/// assert_eq!(format_args!("hello").as_str(), Some("hello"));
|
||
/// assert_eq!(format_args!("").as_str(), Some(""));
|
||
/// assert_eq!(format_args!("{}", 1).as_str(), None);
|
||
/// ```
|
||
#[stable(feature = "fmt_as_str", since = "1.52.0")]
|
||
#[inline]
|
||
pub fn as_str(&self) -> Option<&'static str> {
|
||
match (self.pieces, self.args) {
|
||
([], []) => Some(""),
|
||
([s], []) => Some(s),
|
||
_ => None,
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Debug for Arguments<'_> {
|
||
fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
|
||
Display::fmt(self, fmt)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Display for Arguments<'_> {
|
||
fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
|
||
write(fmt.buf, *self)
|
||
}
|
||
}
|
||
|
||
/// `?` formatting.
|
||
///
|
||
/// `Debug` should format the output in a programmer-facing, debugging context.
|
||
///
|
||
/// Generally speaking, you should just `derive` a `Debug` implementation.
|
||
///
|
||
/// When used with the alternate format specifier `#?`, the output is pretty-printed.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// This trait can be used with `#[derive]` if all fields implement `Debug`. When
|
||
/// `derive`d for structs, it will use the name of the `struct`, then `{`, then a
|
||
/// comma-separated list of each field's name and `Debug` value, then `}`. For
|
||
/// `enum`s, it will use the name of the variant and, if applicable, `(`, then the
|
||
/// `Debug` values of the fields, then `)`.
|
||
///
|
||
/// # Stability
|
||
///
|
||
/// Derived `Debug` formats are not stable, and so may change with future Rust
|
||
/// versions. Additionally, `Debug` implementations of types provided by the
|
||
/// standard library (`libstd`, `libcore`, `liballoc`, etc.) are not stable, and
|
||
/// may also change with future Rust versions.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Deriving an implementation:
|
||
///
|
||
/// ```
|
||
/// #[derive(Debug)]
|
||
/// struct Point {
|
||
/// x: i32,
|
||
/// y: i32,
|
||
/// }
|
||
///
|
||
/// let origin = Point { x: 0, y: 0 };
|
||
///
|
||
/// assert_eq!(format!("The origin is: {:?}", origin), "The origin is: Point { x: 0, y: 0 }");
|
||
/// ```
|
||
///
|
||
/// Manually implementing:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Point {
|
||
/// x: i32,
|
||
/// y: i32,
|
||
/// }
|
||
///
|
||
/// impl fmt::Debug for Point {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// f.debug_struct("Point")
|
||
/// .field("x", &self.x)
|
||
/// .field("y", &self.y)
|
||
/// .finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let origin = Point { x: 0, y: 0 };
|
||
///
|
||
/// assert_eq!(format!("The origin is: {:?}", origin), "The origin is: Point { x: 0, y: 0 }");
|
||
/// ```
|
||
///
|
||
/// There are a number of helper methods on the [`Formatter`] struct to help you with manual
|
||
/// implementations, such as [`debug_struct`].
|
||
///
|
||
/// `Debug` implementations using either `derive` or the debug builder API
|
||
/// on [`Formatter`] support pretty-printing using the alternate flag: `{:#?}`.
|
||
///
|
||
/// [`debug_struct`]: Formatter::debug_struct
|
||
///
|
||
/// Pretty-printing with `#?`:
|
||
///
|
||
/// ```
|
||
/// #[derive(Debug)]
|
||
/// struct Point {
|
||
/// x: i32,
|
||
/// y: i32,
|
||
/// }
|
||
///
|
||
/// let origin = Point { x: 0, y: 0 };
|
||
///
|
||
/// assert_eq!(format!("The origin is: {:#?}", origin),
|
||
/// "The origin is: Point {
|
||
/// x: 0,
|
||
/// y: 0,
|
||
/// }");
|
||
/// ```
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_on_unimplemented(
|
||
on(
|
||
crate_local,
|
||
label = "`{Self}` cannot be formatted using `{{:?}}`",
|
||
note = "add `#[derive(Debug)]` or manually implement `{Debug}`"
|
||
),
|
||
message = "`{Self}` doesn't implement `{Debug}`",
|
||
label = "`{Self}` cannot be formatted using `{{:?}}` because it doesn't implement `{Debug}`"
|
||
)]
|
||
#[doc(alias = "{:?}")]
|
||
#[rustc_diagnostic_item = "debug_trait"]
|
||
pub trait Debug {
|
||
/// Formats the value using the given formatter.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Position {
|
||
/// longitude: f32,
|
||
/// latitude: f32,
|
||
/// }
|
||
///
|
||
/// impl fmt::Debug for Position {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// f.debug_tuple("")
|
||
/// .field(&self.longitude)
|
||
/// .field(&self.latitude)
|
||
/// .finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let position = Position { longitude: 1.987, latitude: 2.983 };
|
||
/// assert_eq!(format!("{:?}", position), "(1.987, 2.983)");
|
||
///
|
||
/// assert_eq!(format!("{:#?}", position), "(
|
||
/// 1.987,
|
||
/// 2.983,
|
||
/// )");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
// Separate module to reexport the macro `Debug` from prelude without the trait `Debug`.
|
||
pub(crate) mod macros {
|
||
/// Derive macro generating an impl of the trait `Debug`.
|
||
#[rustc_builtin_macro]
|
||
#[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
|
||
#[allow_internal_unstable(core_intrinsics)]
|
||
pub macro Debug($item:item) {
|
||
/* compiler built-in */
|
||
}
|
||
}
|
||
#[stable(feature = "builtin_macro_prelude", since = "1.38.0")]
|
||
#[doc(inline)]
|
||
pub use macros::Debug;
|
||
|
||
/// Format trait for an empty format, `{}`.
|
||
///
|
||
/// `Display` is similar to [`Debug`], but `Display` is for user-facing
|
||
/// output, and so cannot be derived.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Implementing `Display` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Point {
|
||
/// x: i32,
|
||
/// y: i32,
|
||
/// }
|
||
///
|
||
/// impl fmt::Display for Point {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// write!(f, "({}, {})", self.x, self.y)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let origin = Point { x: 0, y: 0 };
|
||
///
|
||
/// assert_eq!(format!("The origin is: {}", origin), "The origin is: (0, 0)");
|
||
/// ```
|
||
#[rustc_on_unimplemented(
|
||
on(
|
||
_Self = "std::path::Path",
|
||
label = "`{Self}` cannot be formatted with the default formatter; call `.display()` on it",
|
||
note = "call `.display()` or `.to_string_lossy()` to safely print paths, \
|
||
as they may contain non-Unicode data"
|
||
),
|
||
message = "`{Self}` doesn't implement `{Display}`",
|
||
label = "`{Self}` cannot be formatted with the default formatter",
|
||
note = "in format strings you may be able to use `{{:?}}` (or {{:#?}} for pretty-print) instead"
|
||
)]
|
||
#[doc(alias = "{}")]
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait Display {
|
||
/// Formats the value using the given formatter.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Position {
|
||
/// longitude: f32,
|
||
/// latitude: f32,
|
||
/// }
|
||
///
|
||
/// impl fmt::Display for Position {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// write!(f, "({}, {})", self.longitude, self.latitude)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!("(1.987, 2.983)",
|
||
/// format!("{}", Position { longitude: 1.987, latitude: 2.983, }));
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `o` formatting.
|
||
///
|
||
/// The `Octal` trait should format its output as a number in base-8.
|
||
///
|
||
/// For primitive signed integers (`i8` to `i128`, and `isize`),
|
||
/// negative values are formatted as the two’s complement representation.
|
||
///
|
||
/// The alternate flag, `#`, adds a `0o` in front of the output.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with `i32`:
|
||
///
|
||
/// ```
|
||
/// let x = 42; // 42 is '52' in octal
|
||
///
|
||
/// assert_eq!(format!("{:o}", x), "52");
|
||
/// assert_eq!(format!("{:#o}", x), "0o52");
|
||
///
|
||
/// assert_eq!(format!("{:o}", -16), "37777777760");
|
||
/// ```
|
||
///
|
||
/// Implementing `Octal` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::Octal for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// let val = self.0;
|
||
///
|
||
/// fmt::Octal::fmt(&val, f) // delegate to i32's implementation
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(9);
|
||
///
|
||
/// assert_eq!(format!("l as octal is: {:o}", l), "l as octal is: 11");
|
||
///
|
||
/// assert_eq!(format!("l as octal is: {:#06o}", l), "l as octal is: 0o0011");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait Octal {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `b` formatting.
|
||
///
|
||
/// The `Binary` trait should format its output as a number in binary.
|
||
///
|
||
/// For primitive signed integers ([`i8`] to [`i128`], and [`isize`]),
|
||
/// negative values are formatted as the two’s complement representation.
|
||
///
|
||
/// The alternate flag, `#`, adds a `0b` in front of the output.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with [`i32`]:
|
||
///
|
||
/// ```
|
||
/// let x = 42; // 42 is '101010' in binary
|
||
///
|
||
/// assert_eq!(format!("{:b}", x), "101010");
|
||
/// assert_eq!(format!("{:#b}", x), "0b101010");
|
||
///
|
||
/// assert_eq!(format!("{:b}", -16), "11111111111111111111111111110000");
|
||
/// ```
|
||
///
|
||
/// Implementing `Binary` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::Binary for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// let val = self.0;
|
||
///
|
||
/// fmt::Binary::fmt(&val, f) // delegate to i32's implementation
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(107);
|
||
///
|
||
/// assert_eq!(format!("l as binary is: {:b}", l), "l as binary is: 1101011");
|
||
///
|
||
/// assert_eq!(
|
||
/// format!("l as binary is: {:#032b}", l),
|
||
/// "l as binary is: 0b000000000000000000000001101011"
|
||
/// );
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait Binary {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `x` formatting.
|
||
///
|
||
/// The `LowerHex` trait should format its output as a number in hexadecimal, with `a` through `f`
|
||
/// in lower case.
|
||
///
|
||
/// For primitive signed integers (`i8` to `i128`, and `isize`),
|
||
/// negative values are formatted as the two’s complement representation.
|
||
///
|
||
/// The alternate flag, `#`, adds a `0x` in front of the output.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with `i32`:
|
||
///
|
||
/// ```
|
||
/// let x = 42; // 42 is '2a' in hex
|
||
///
|
||
/// assert_eq!(format!("{:x}", x), "2a");
|
||
/// assert_eq!(format!("{:#x}", x), "0x2a");
|
||
///
|
||
/// assert_eq!(format!("{:x}", -16), "fffffff0");
|
||
/// ```
|
||
///
|
||
/// Implementing `LowerHex` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::LowerHex for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// let val = self.0;
|
||
///
|
||
/// fmt::LowerHex::fmt(&val, f) // delegate to i32's implementation
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(9);
|
||
///
|
||
/// assert_eq!(format!("l as hex is: {:x}", l), "l as hex is: 9");
|
||
///
|
||
/// assert_eq!(format!("l as hex is: {:#010x}", l), "l as hex is: 0x00000009");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait LowerHex {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `X` formatting.
|
||
///
|
||
/// The `UpperHex` trait should format its output as a number in hexadecimal, with `A` through `F`
|
||
/// in upper case.
|
||
///
|
||
/// For primitive signed integers (`i8` to `i128`, and `isize`),
|
||
/// negative values are formatted as the two’s complement representation.
|
||
///
|
||
/// The alternate flag, `#`, adds a `0x` in front of the output.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with `i32`:
|
||
///
|
||
/// ```
|
||
/// let x = 42; // 42 is '2A' in hex
|
||
///
|
||
/// assert_eq!(format!("{:X}", x), "2A");
|
||
/// assert_eq!(format!("{:#X}", x), "0x2A");
|
||
///
|
||
/// assert_eq!(format!("{:X}", -16), "FFFFFFF0");
|
||
/// ```
|
||
///
|
||
/// Implementing `UpperHex` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::UpperHex for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// let val = self.0;
|
||
///
|
||
/// fmt::UpperHex::fmt(&val, f) // delegate to i32's implementation
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(i32::MAX);
|
||
///
|
||
/// assert_eq!(format!("l as hex is: {:X}", l), "l as hex is: 7FFFFFFF");
|
||
///
|
||
/// assert_eq!(format!("l as hex is: {:#010X}", l), "l as hex is: 0x7FFFFFFF");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait UpperHex {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `p` formatting.
|
||
///
|
||
/// The `Pointer` trait should format its output as a memory location. This is commonly presented
|
||
/// as hexadecimal.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with `&i32`:
|
||
///
|
||
/// ```
|
||
/// let x = &42;
|
||
///
|
||
/// let address = format!("{:p}", x); // this produces something like '0x7f06092ac6d0'
|
||
/// ```
|
||
///
|
||
/// Implementing `Pointer` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::Pointer for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// // use `as` to convert to a `*const T`, which implements Pointer, which we can use
|
||
///
|
||
/// let ptr = self as *const Self;
|
||
/// fmt::Pointer::fmt(&ptr, f)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(42);
|
||
///
|
||
/// println!("l is in memory here: {:p}", l);
|
||
///
|
||
/// let l_ptr = format!("{:018p}", l);
|
||
/// assert_eq!(l_ptr.len(), 18);
|
||
/// assert_eq!(&l_ptr[..2], "0x");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_diagnostic_item = "pointer_trait"]
|
||
pub trait Pointer {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_diagnostic_item = "pointer_trait_fmt"]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `e` formatting.
|
||
///
|
||
/// The `LowerExp` trait should format its output in scientific notation with a lower-case `e`.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with `f64`:
|
||
///
|
||
/// ```
|
||
/// let x = 42.0; // 42.0 is '4.2e1' in scientific notation
|
||
///
|
||
/// assert_eq!(format!("{:e}", x), "4.2e1");
|
||
/// ```
|
||
///
|
||
/// Implementing `LowerExp` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::LowerExp for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// let val = f64::from(self.0);
|
||
/// fmt::LowerExp::fmt(&val, f) // delegate to f64's implementation
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(100);
|
||
///
|
||
/// assert_eq!(
|
||
/// format!("l in scientific notation is: {:e}", l),
|
||
/// "l in scientific notation is: 1e2"
|
||
/// );
|
||
///
|
||
/// assert_eq!(
|
||
/// format!("l in scientific notation is: {:05e}", l),
|
||
/// "l in scientific notation is: 001e2"
|
||
/// );
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait LowerExp {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// `E` formatting.
|
||
///
|
||
/// The `UpperExp` trait should format its output in scientific notation with an upper-case `E`.
|
||
///
|
||
/// For more information on formatters, see [the module-level documentation][module].
|
||
///
|
||
/// [module]: ../../std/fmt/index.html
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage with `f64`:
|
||
///
|
||
/// ```
|
||
/// let x = 42.0; // 42.0 is '4.2E1' in scientific notation
|
||
///
|
||
/// assert_eq!(format!("{:E}", x), "4.2E1");
|
||
/// ```
|
||
///
|
||
/// Implementing `UpperExp` on a type:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Length(i32);
|
||
///
|
||
/// impl fmt::UpperExp for Length {
|
||
/// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
|
||
/// let val = f64::from(self.0);
|
||
/// fmt::UpperExp::fmt(&val, f) // delegate to f64's implementation
|
||
/// }
|
||
/// }
|
||
///
|
||
/// let l = Length(100);
|
||
///
|
||
/// assert_eq!(
|
||
/// format!("l in scientific notation is: {:E}", l),
|
||
/// "l in scientific notation is: 1E2"
|
||
/// );
|
||
///
|
||
/// assert_eq!(
|
||
/// format!("l in scientific notation is: {:05E}", l),
|
||
/// "l in scientific notation is: 001E2"
|
||
/// );
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub trait UpperExp {
|
||
/// Formats the value using the given formatter.
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result;
|
||
}
|
||
|
||
/// The `write` function takes an output stream, and an `Arguments` struct
|
||
/// that can be precompiled with the `format_args!` macro.
|
||
///
|
||
/// The arguments will be formatted according to the specified format string
|
||
/// into the output stream provided.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// Basic usage:
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// let mut output = String::new();
|
||
/// fmt::write(&mut output, format_args!("Hello {}!", "world"))
|
||
/// .expect("Error occurred while trying to write in String");
|
||
/// assert_eq!(output, "Hello world!");
|
||
/// ```
|
||
///
|
||
/// Please note that using [`write!`] might be preferable. Example:
|
||
///
|
||
/// ```
|
||
/// use std::fmt::Write;
|
||
///
|
||
/// let mut output = String::new();
|
||
/// write!(&mut output, "Hello {}!", "world")
|
||
/// .expect("Error occurred while trying to write in String");
|
||
/// assert_eq!(output, "Hello world!");
|
||
/// ```
|
||
///
|
||
/// [`write!`]: crate::write!
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn write(output: &mut dyn Write, args: Arguments<'_>) -> Result {
|
||
let mut formatter = Formatter {
|
||
flags: 0,
|
||
width: None,
|
||
precision: None,
|
||
buf: output,
|
||
align: rt::v1::Alignment::Unknown,
|
||
fill: ' ',
|
||
};
|
||
|
||
let mut idx = 0;
|
||
|
||
match args.fmt {
|
||
None => {
|
||
// We can use default formatting parameters for all arguments.
|
||
for (arg, piece) in iter::zip(args.args, args.pieces) {
|
||
formatter.buf.write_str(*piece)?;
|
||
(arg.formatter)(arg.value, &mut formatter)?;
|
||
idx += 1;
|
||
}
|
||
}
|
||
Some(fmt) => {
|
||
// Every spec has a corresponding argument that is preceded by
|
||
// a string piece.
|
||
for (arg, piece) in iter::zip(fmt, args.pieces) {
|
||
formatter.buf.write_str(*piece)?;
|
||
// SAFETY: arg and args.args come from the same Arguments,
|
||
// which guarantees the indexes are always within bounds.
|
||
unsafe { run(&mut formatter, arg, &args.args) }?;
|
||
idx += 1;
|
||
}
|
||
}
|
||
}
|
||
|
||
// There can be only one trailing string piece left.
|
||
if let Some(piece) = args.pieces.get(idx) {
|
||
formatter.buf.write_str(*piece)?;
|
||
}
|
||
|
||
Ok(())
|
||
}
|
||
|
||
unsafe fn run(fmt: &mut Formatter<'_>, arg: &rt::v1::Argument, args: &[ArgumentV1<'_>]) -> Result {
|
||
fmt.fill = arg.format.fill;
|
||
fmt.align = arg.format.align;
|
||
fmt.flags = arg.format.flags;
|
||
// SAFETY: arg and args come from the same Arguments,
|
||
// which guarantees the indexes are always within bounds.
|
||
unsafe {
|
||
fmt.width = getcount(args, &arg.format.width);
|
||
fmt.precision = getcount(args, &arg.format.precision);
|
||
}
|
||
|
||
// Extract the correct argument
|
||
debug_assert!(arg.position < args.len());
|
||
// SAFETY: arg and args come from the same Arguments,
|
||
// which guarantees its index is always within bounds.
|
||
let value = unsafe { args.get_unchecked(arg.position) };
|
||
|
||
// Then actually do some printing
|
||
(value.formatter)(value.value, fmt)
|
||
}
|
||
|
||
unsafe fn getcount(args: &[ArgumentV1<'_>], cnt: &rt::v1::Count) -> Option<usize> {
|
||
match *cnt {
|
||
rt::v1::Count::Is(n) => Some(n),
|
||
rt::v1::Count::Implied => None,
|
||
rt::v1::Count::Param(i) => {
|
||
debug_assert!(i < args.len());
|
||
// SAFETY: cnt and args come from the same Arguments,
|
||
// which guarantees this index is always within bounds.
|
||
unsafe { args.get_unchecked(i).as_usize() }
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Padding after the end of something. Returned by `Formatter::padding`.
|
||
#[must_use = "don't forget to write the post padding"]
|
||
struct PostPadding {
|
||
fill: char,
|
||
padding: usize,
|
||
}
|
||
|
||
impl PostPadding {
|
||
fn new(fill: char, padding: usize) -> PostPadding {
|
||
PostPadding { fill, padding }
|
||
}
|
||
|
||
/// Write this post padding.
|
||
fn write(self, buf: &mut dyn Write) -> Result {
|
||
for _ in 0..self.padding {
|
||
buf.write_char(self.fill)?;
|
||
}
|
||
Ok(())
|
||
}
|
||
}
|
||
|
||
impl<'a> Formatter<'a> {
|
||
fn wrap_buf<'b, 'c, F>(&'b mut self, wrap: F) -> Formatter<'c>
|
||
where
|
||
'b: 'c,
|
||
F: FnOnce(&'b mut (dyn Write + 'b)) -> &'c mut (dyn Write + 'c),
|
||
{
|
||
Formatter {
|
||
// We want to change this
|
||
buf: wrap(self.buf),
|
||
|
||
// And preserve these
|
||
flags: self.flags,
|
||
fill: self.fill,
|
||
align: self.align,
|
||
width: self.width,
|
||
precision: self.precision,
|
||
}
|
||
}
|
||
|
||
// Helper methods used for padding and processing formatting arguments that
|
||
// all formatting traits can use.
|
||
|
||
/// Performs the correct padding for an integer which has already been
|
||
/// emitted into a str. The str should *not* contain the sign for the
|
||
/// integer, that will be added by this method.
|
||
///
|
||
/// # Arguments
|
||
///
|
||
/// * is_nonnegative - whether the original integer was either positive or zero.
|
||
/// * prefix - if the '#' character (Alternate) is provided, this
|
||
/// is the prefix to put in front of the number.
|
||
/// * buf - the byte array that the number has been formatted into
|
||
///
|
||
/// This function will correctly account for the flags provided as well as
|
||
/// the minimum width. It will not take precision into account.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo { nb: i32 }
|
||
///
|
||
/// impl Foo {
|
||
/// fn new(nb: i32) -> Foo {
|
||
/// Foo {
|
||
/// nb,
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// // We need to remove "-" from the number output.
|
||
/// let tmp = self.nb.abs().to_string();
|
||
///
|
||
/// formatter.pad_integral(self.nb > 0, "Foo ", &tmp)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{}", Foo::new(2)), "2");
|
||
/// assert_eq!(&format!("{}", Foo::new(-1)), "-1");
|
||
/// assert_eq!(&format!("{:#}", Foo::new(-1)), "-Foo 1");
|
||
/// assert_eq!(&format!("{:0>#8}", Foo::new(-1)), "00-Foo 1");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn pad_integral(&mut self, is_nonnegative: bool, prefix: &str, buf: &str) -> Result {
|
||
let mut width = buf.len();
|
||
|
||
let mut sign = None;
|
||
if !is_nonnegative {
|
||
sign = Some('-');
|
||
width += 1;
|
||
} else if self.sign_plus() {
|
||
sign = Some('+');
|
||
width += 1;
|
||
}
|
||
|
||
let prefix = if self.alternate() {
|
||
width += prefix.chars().count();
|
||
Some(prefix)
|
||
} else {
|
||
None
|
||
};
|
||
|
||
// Writes the sign if it exists, and then the prefix if it was requested
|
||
#[inline(never)]
|
||
fn write_prefix(f: &mut Formatter<'_>, sign: Option<char>, prefix: Option<&str>) -> Result {
|
||
if let Some(c) = sign {
|
||
f.buf.write_char(c)?;
|
||
}
|
||
if let Some(prefix) = prefix { f.buf.write_str(prefix) } else { Ok(()) }
|
||
}
|
||
|
||
// The `width` field is more of a `min-width` parameter at this point.
|
||
match self.width {
|
||
// If there's no minimum length requirements then we can just
|
||
// write the bytes.
|
||
None => {
|
||
write_prefix(self, sign, prefix)?;
|
||
self.buf.write_str(buf)
|
||
}
|
||
// Check if we're over the minimum width, if so then we can also
|
||
// just write the bytes.
|
||
Some(min) if width >= min => {
|
||
write_prefix(self, sign, prefix)?;
|
||
self.buf.write_str(buf)
|
||
}
|
||
// The sign and prefix goes before the padding if the fill character
|
||
// is zero
|
||
Some(min) if self.sign_aware_zero_pad() => {
|
||
let old_fill = crate::mem::replace(&mut self.fill, '0');
|
||
let old_align = crate::mem::replace(&mut self.align, rt::v1::Alignment::Right);
|
||
write_prefix(self, sign, prefix)?;
|
||
let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
|
||
self.buf.write_str(buf)?;
|
||
post_padding.write(self.buf)?;
|
||
self.fill = old_fill;
|
||
self.align = old_align;
|
||
Ok(())
|
||
}
|
||
// Otherwise, the sign and prefix goes after the padding
|
||
Some(min) => {
|
||
let post_padding = self.padding(min - width, rt::v1::Alignment::Right)?;
|
||
write_prefix(self, sign, prefix)?;
|
||
self.buf.write_str(buf)?;
|
||
post_padding.write(self.buf)
|
||
}
|
||
}
|
||
}
|
||
|
||
/// This function takes a string slice and emits it to the internal buffer
|
||
/// after applying the relevant formatting flags specified. The flags
|
||
/// recognized for generic strings are:
|
||
///
|
||
/// * width - the minimum width of what to emit
|
||
/// * fill/align - what to emit and where to emit it if the string
|
||
/// provided needs to be padded
|
||
/// * precision - the maximum length to emit, the string is truncated if it
|
||
/// is longer than this length
|
||
///
|
||
/// Notably this function ignores the `flag` parameters.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo;
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// formatter.pad("Foo")
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:<4}", Foo), "Foo ");
|
||
/// assert_eq!(&format!("{:0>4}", Foo), "0Foo");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn pad(&mut self, s: &str) -> Result {
|
||
// Make sure there's a fast path up front
|
||
if self.width.is_none() && self.precision.is_none() {
|
||
return self.buf.write_str(s);
|
||
}
|
||
// The `precision` field can be interpreted as a `max-width` for the
|
||
// string being formatted.
|
||
let s = if let Some(max) = self.precision {
|
||
// If our string is longer that the precision, then we must have
|
||
// truncation. However other flags like `fill`, `width` and `align`
|
||
// must act as always.
|
||
if let Some((i, _)) = s.char_indices().nth(max) {
|
||
// LLVM here can't prove that `..i` won't panic `&s[..i]`, but
|
||
// we know that it can't panic. Use `get` + `unwrap_or` to avoid
|
||
// `unsafe` and otherwise don't emit any panic-related code
|
||
// here.
|
||
s.get(..i).unwrap_or(&s)
|
||
} else {
|
||
&s
|
||
}
|
||
} else {
|
||
&s
|
||
};
|
||
// The `width` field is more of a `min-width` parameter at this point.
|
||
match self.width {
|
||
// If we're under the maximum length, and there's no minimum length
|
||
// requirements, then we can just emit the string
|
||
None => self.buf.write_str(s),
|
||
// If we're under the maximum width, check if we're over the minimum
|
||
// width, if so it's as easy as just emitting the string.
|
||
Some(width) if s.chars().count() >= width => self.buf.write_str(s),
|
||
// If we're under both the maximum and the minimum width, then fill
|
||
// up the minimum width with the specified string + some alignment.
|
||
Some(width) => {
|
||
let align = rt::v1::Alignment::Left;
|
||
let post_padding = self.padding(width - s.chars().count(), align)?;
|
||
self.buf.write_str(s)?;
|
||
post_padding.write(self.buf)
|
||
}
|
||
}
|
||
}
|
||
|
||
/// Write the pre-padding and return the unwritten post-padding. Callers are
|
||
/// responsible for ensuring post-padding is written after the thing that is
|
||
/// being padded.
|
||
fn padding(
|
||
&mut self,
|
||
padding: usize,
|
||
default: rt::v1::Alignment,
|
||
) -> result::Result<PostPadding, Error> {
|
||
let align = match self.align {
|
||
rt::v1::Alignment::Unknown => default,
|
||
_ => self.align,
|
||
};
|
||
|
||
let (pre_pad, post_pad) = match align {
|
||
rt::v1::Alignment::Left => (0, padding),
|
||
rt::v1::Alignment::Right | rt::v1::Alignment::Unknown => (padding, 0),
|
||
rt::v1::Alignment::Center => (padding / 2, (padding + 1) / 2),
|
||
};
|
||
|
||
for _ in 0..pre_pad {
|
||
self.buf.write_char(self.fill)?;
|
||
}
|
||
|
||
Ok(PostPadding::new(self.fill, post_pad))
|
||
}
|
||
|
||
/// Takes the formatted parts and applies the padding.
|
||
/// Assumes that the caller already has rendered the parts with required precision,
|
||
/// so that `self.precision` can be ignored.
|
||
fn pad_formatted_parts(&mut self, formatted: &flt2dec::Formatted<'_>) -> Result {
|
||
if let Some(mut width) = self.width {
|
||
// for the sign-aware zero padding, we render the sign first and
|
||
// behave as if we had no sign from the beginning.
|
||
let mut formatted = formatted.clone();
|
||
let old_fill = self.fill;
|
||
let old_align = self.align;
|
||
let mut align = old_align;
|
||
if self.sign_aware_zero_pad() {
|
||
// a sign always goes first
|
||
let sign = formatted.sign;
|
||
self.buf.write_str(sign)?;
|
||
|
||
// remove the sign from the formatted parts
|
||
formatted.sign = "";
|
||
width = width.saturating_sub(sign.len());
|
||
align = rt::v1::Alignment::Right;
|
||
self.fill = '0';
|
||
self.align = rt::v1::Alignment::Right;
|
||
}
|
||
|
||
// remaining parts go through the ordinary padding process.
|
||
let len = formatted.len();
|
||
let ret = if width <= len {
|
||
// no padding
|
||
self.write_formatted_parts(&formatted)
|
||
} else {
|
||
let post_padding = self.padding(width - len, align)?;
|
||
self.write_formatted_parts(&formatted)?;
|
||
post_padding.write(self.buf)
|
||
};
|
||
self.fill = old_fill;
|
||
self.align = old_align;
|
||
ret
|
||
} else {
|
||
// this is the common case and we take a shortcut
|
||
self.write_formatted_parts(formatted)
|
||
}
|
||
}
|
||
|
||
fn write_formatted_parts(&mut self, formatted: &flt2dec::Formatted<'_>) -> Result {
|
||
fn write_bytes(buf: &mut dyn Write, s: &[u8]) -> Result {
|
||
// SAFETY: This is used for `flt2dec::Part::Num` and `flt2dec::Part::Copy`.
|
||
// It's safe to use for `flt2dec::Part::Num` since every char `c` is between
|
||
// `b'0'` and `b'9'`, which means `s` is valid UTF-8.
|
||
// It's also probably safe in practice to use for `flt2dec::Part::Copy(buf)`
|
||
// since `buf` should be plain ASCII, but it's possible for someone to pass
|
||
// in a bad value for `buf` into `flt2dec::to_shortest_str` since it is a
|
||
// public function.
|
||
// FIXME: Determine whether this could result in UB.
|
||
buf.write_str(unsafe { str::from_utf8_unchecked(s) })
|
||
}
|
||
|
||
if !formatted.sign.is_empty() {
|
||
self.buf.write_str(formatted.sign)?;
|
||
}
|
||
for part in formatted.parts {
|
||
match *part {
|
||
flt2dec::Part::Zero(mut nzeroes) => {
|
||
const ZEROES: &str = // 64 zeroes
|
||
"0000000000000000000000000000000000000000000000000000000000000000";
|
||
while nzeroes > ZEROES.len() {
|
||
self.buf.write_str(ZEROES)?;
|
||
nzeroes -= ZEROES.len();
|
||
}
|
||
if nzeroes > 0 {
|
||
self.buf.write_str(&ZEROES[..nzeroes])?;
|
||
}
|
||
}
|
||
flt2dec::Part::Num(mut v) => {
|
||
let mut s = [0; 5];
|
||
let len = part.len();
|
||
for c in s[..len].iter_mut().rev() {
|
||
*c = b'0' + (v % 10) as u8;
|
||
v /= 10;
|
||
}
|
||
write_bytes(self.buf, &s[..len])?;
|
||
}
|
||
flt2dec::Part::Copy(buf) => {
|
||
write_bytes(self.buf, buf)?;
|
||
}
|
||
}
|
||
}
|
||
Ok(())
|
||
}
|
||
|
||
/// Writes some data to the underlying buffer contained within this
|
||
/// formatter.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo;
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// formatter.write_str("Foo")
|
||
/// // This is equivalent to:
|
||
/// // write!(formatter, "Foo")
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{}", Foo), "Foo");
|
||
/// assert_eq!(&format!("{:0>8}", Foo), "Foo");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn write_str(&mut self, data: &str) -> Result {
|
||
self.buf.write_str(data)
|
||
}
|
||
|
||
/// Writes some formatted information into this instance.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(i32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// formatter.write_fmt(format_args!("Foo {}", self.0))
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{}", Foo(-1)), "Foo -1");
|
||
/// assert_eq!(&format!("{:0>8}", Foo(2)), "Foo 2");
|
||
/// ```
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
pub fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result {
|
||
write(self.buf, fmt)
|
||
}
|
||
|
||
/// Flags for formatting
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
#[rustc_deprecated(
|
||
since = "1.24.0",
|
||
reason = "use the `sign_plus`, `sign_minus`, `alternate`, \
|
||
or `sign_aware_zero_pad` methods instead"
|
||
)]
|
||
pub fn flags(&self) -> u32 {
|
||
self.flags
|
||
}
|
||
|
||
/// Character used as 'fill' whenever there is alignment.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo;
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// let c = formatter.fill();
|
||
/// if let Some(width) = formatter.width() {
|
||
/// for _ in 0..width {
|
||
/// write!(formatter, "{}", c)?;
|
||
/// }
|
||
/// Ok(())
|
||
/// } else {
|
||
/// write!(formatter, "{}", c)
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// // We set alignment to the right with ">".
|
||
/// assert_eq!(&format!("{:G>3}", Foo), "GGG");
|
||
/// assert_eq!(&format!("{:t>6}", Foo), "tttttt");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn fill(&self) -> char {
|
||
self.fill
|
||
}
|
||
|
||
/// Flag indicating what form of alignment was requested.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// extern crate core;
|
||
///
|
||
/// use std::fmt::{self, Alignment};
|
||
///
|
||
/// struct Foo;
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// let s = if let Some(s) = formatter.align() {
|
||
/// match s {
|
||
/// Alignment::Left => "left",
|
||
/// Alignment::Right => "right",
|
||
/// Alignment::Center => "center",
|
||
/// }
|
||
/// } else {
|
||
/// "into the void"
|
||
/// };
|
||
/// write!(formatter, "{}", s)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:<}", Foo), "left");
|
||
/// assert_eq!(&format!("{:>}", Foo), "right");
|
||
/// assert_eq!(&format!("{:^}", Foo), "center");
|
||
/// assert_eq!(&format!("{}", Foo), "into the void");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags_align", since = "1.28.0")]
|
||
pub fn align(&self) -> Option<Alignment> {
|
||
match self.align {
|
||
rt::v1::Alignment::Left => Some(Alignment::Left),
|
||
rt::v1::Alignment::Right => Some(Alignment::Right),
|
||
rt::v1::Alignment::Center => Some(Alignment::Center),
|
||
rt::v1::Alignment::Unknown => None,
|
||
}
|
||
}
|
||
|
||
/// Optionally specified integer width that the output should be.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(i32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// if let Some(width) = formatter.width() {
|
||
/// // If we received a width, we use it
|
||
/// write!(formatter, "{:width$}", &format!("Foo({})", self.0), width = width)
|
||
/// } else {
|
||
/// // Otherwise we do nothing special
|
||
/// write!(formatter, "Foo({})", self.0)
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:10}", Foo(23)), "Foo(23) ");
|
||
/// assert_eq!(&format!("{}", Foo(23)), "Foo(23)");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn width(&self) -> Option<usize> {
|
||
self.width
|
||
}
|
||
|
||
/// Optionally specified precision for numeric types. Alternatively, the
|
||
/// maximum width for string types.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(f32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// if let Some(precision) = formatter.precision() {
|
||
/// // If we received a precision, we use it.
|
||
/// write!(formatter, "Foo({1:.*})", precision, self.0)
|
||
/// } else {
|
||
/// // Otherwise we default to 2.
|
||
/// write!(formatter, "Foo({:.2})", self.0)
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:.4}", Foo(23.2)), "Foo(23.2000)");
|
||
/// assert_eq!(&format!("{}", Foo(23.2)), "Foo(23.20)");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn precision(&self) -> Option<usize> {
|
||
self.precision
|
||
}
|
||
|
||
/// Determines if the `+` flag was specified.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(i32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// if formatter.sign_plus() {
|
||
/// write!(formatter,
|
||
/// "Foo({}{})",
|
||
/// if self.0 < 0 { '-' } else { '+' },
|
||
/// self.0)
|
||
/// } else {
|
||
/// write!(formatter, "Foo({})", self.0)
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:+}", Foo(23)), "Foo(+23)");
|
||
/// assert_eq!(&format!("{}", Foo(23)), "Foo(23)");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn sign_plus(&self) -> bool {
|
||
self.flags & (1 << FlagV1::SignPlus as u32) != 0
|
||
}
|
||
|
||
/// Determines if the `-` flag was specified.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(i32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// if formatter.sign_minus() {
|
||
/// // You want a minus sign? Have one!
|
||
/// write!(formatter, "-Foo({})", self.0)
|
||
/// } else {
|
||
/// write!(formatter, "Foo({})", self.0)
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:-}", Foo(23)), "-Foo(23)");
|
||
/// assert_eq!(&format!("{}", Foo(23)), "Foo(23)");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn sign_minus(&self) -> bool {
|
||
self.flags & (1 << FlagV1::SignMinus as u32) != 0
|
||
}
|
||
|
||
/// Determines if the `#` flag was specified.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(i32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// if formatter.alternate() {
|
||
/// write!(formatter, "Foo({})", self.0)
|
||
/// } else {
|
||
/// write!(formatter, "{}", self.0)
|
||
/// }
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:#}", Foo(23)), "Foo(23)");
|
||
/// assert_eq!(&format!("{}", Foo(23)), "23");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn alternate(&self) -> bool {
|
||
self.flags & (1 << FlagV1::Alternate as u32) != 0
|
||
}
|
||
|
||
/// Determines if the `0` flag was specified.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(i32);
|
||
///
|
||
/// impl fmt::Display for Foo {
|
||
/// fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
||
/// assert!(formatter.sign_aware_zero_pad());
|
||
/// assert_eq!(formatter.width(), Some(4));
|
||
/// // We ignore the formatter's options.
|
||
/// write!(formatter, "{}", self.0)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(&format!("{:04}", Foo(23)), "23");
|
||
/// ```
|
||
#[stable(feature = "fmt_flags", since = "1.5.0")]
|
||
pub fn sign_aware_zero_pad(&self) -> bool {
|
||
self.flags & (1 << FlagV1::SignAwareZeroPad as u32) != 0
|
||
}
|
||
|
||
// FIXME: Decide what public API we want for these two flags.
|
||
// https://github.com/rust-lang/rust/issues/48584
|
||
fn debug_lower_hex(&self) -> bool {
|
||
self.flags & (1 << FlagV1::DebugLowerHex as u32) != 0
|
||
}
|
||
|
||
fn debug_upper_hex(&self) -> bool {
|
||
self.flags & (1 << FlagV1::DebugUpperHex as u32) != 0
|
||
}
|
||
|
||
/// Creates a [`DebugStruct`] builder designed to assist with creation of
|
||
/// [`fmt::Debug`] implementations for structs.
|
||
///
|
||
/// [`fmt::Debug`]: self::Debug
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt;
|
||
/// use std::net::Ipv4Addr;
|
||
///
|
||
/// struct Foo {
|
||
/// bar: i32,
|
||
/// baz: String,
|
||
/// addr: Ipv4Addr,
|
||
/// }
|
||
///
|
||
/// impl fmt::Debug for Foo {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// fmt.debug_struct("Foo")
|
||
/// .field("bar", &self.bar)
|
||
/// .field("baz", &self.baz)
|
||
/// .field("addr", &format_args!("{}", self.addr))
|
||
/// .finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(
|
||
/// "Foo { bar: 10, baz: \"Hello World\", addr: 127.0.0.1 }",
|
||
/// format!("{:?}", Foo {
|
||
/// bar: 10,
|
||
/// baz: "Hello World".to_string(),
|
||
/// addr: Ipv4Addr::new(127, 0, 0, 1),
|
||
/// })
|
||
/// );
|
||
/// ```
|
||
#[stable(feature = "debug_builders", since = "1.2.0")]
|
||
pub fn debug_struct<'b>(&'b mut self, name: &str) -> DebugStruct<'b, 'a> {
|
||
builders::debug_struct_new(self, name)
|
||
}
|
||
|
||
/// Creates a `DebugTuple` builder designed to assist with creation of
|
||
/// `fmt::Debug` implementations for tuple structs.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt;
|
||
/// use std::marker::PhantomData;
|
||
///
|
||
/// struct Foo<T>(i32, String, PhantomData<T>);
|
||
///
|
||
/// impl<T> fmt::Debug for Foo<T> {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// fmt.debug_tuple("Foo")
|
||
/// .field(&self.0)
|
||
/// .field(&self.1)
|
||
/// .field(&format_args!("_"))
|
||
/// .finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(
|
||
/// "Foo(10, \"Hello\", _)",
|
||
/// format!("{:?}", Foo(10, "Hello".to_string(), PhantomData::<u8>))
|
||
/// );
|
||
/// ```
|
||
#[stable(feature = "debug_builders", since = "1.2.0")]
|
||
pub fn debug_tuple<'b>(&'b mut self, name: &str) -> DebugTuple<'b, 'a> {
|
||
builders::debug_tuple_new(self, name)
|
||
}
|
||
|
||
/// Creates a `DebugList` builder designed to assist with creation of
|
||
/// `fmt::Debug` implementations for list-like structures.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(Vec<i32>);
|
||
///
|
||
/// impl fmt::Debug for Foo {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// fmt.debug_list().entries(self.0.iter()).finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(format!("{:?}", Foo(vec![10, 11])), "[10, 11]");
|
||
/// ```
|
||
#[stable(feature = "debug_builders", since = "1.2.0")]
|
||
pub fn debug_list<'b>(&'b mut self) -> DebugList<'b, 'a> {
|
||
builders::debug_list_new(self)
|
||
}
|
||
|
||
/// Creates a `DebugSet` builder designed to assist with creation of
|
||
/// `fmt::Debug` implementations for set-like structures.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(Vec<i32>);
|
||
///
|
||
/// impl fmt::Debug for Foo {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// fmt.debug_set().entries(self.0.iter()).finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(format!("{:?}", Foo(vec![10, 11])), "{10, 11}");
|
||
/// ```
|
||
///
|
||
/// [`format_args!`]: crate::format_args
|
||
///
|
||
/// In this more complex example, we use [`format_args!`] and `.debug_set()`
|
||
/// to build a list of match arms:
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Arm<'a, L: 'a, R: 'a>(&'a (L, R));
|
||
/// struct Table<'a, K: 'a, V: 'a>(&'a [(K, V)], V);
|
||
///
|
||
/// impl<'a, L, R> fmt::Debug for Arm<'a, L, R>
|
||
/// where
|
||
/// L: 'a + fmt::Debug, R: 'a + fmt::Debug
|
||
/// {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// L::fmt(&(self.0).0, fmt)?;
|
||
/// fmt.write_str(" => ")?;
|
||
/// R::fmt(&(self.0).1, fmt)
|
||
/// }
|
||
/// }
|
||
///
|
||
/// impl<'a, K, V> fmt::Debug for Table<'a, K, V>
|
||
/// where
|
||
/// K: 'a + fmt::Debug, V: 'a + fmt::Debug
|
||
/// {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// fmt.debug_set()
|
||
/// .entries(self.0.iter().map(Arm))
|
||
/// .entry(&Arm(&(format_args!("_"), &self.1)))
|
||
/// .finish()
|
||
/// }
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "debug_builders", since = "1.2.0")]
|
||
pub fn debug_set<'b>(&'b mut self) -> DebugSet<'b, 'a> {
|
||
builders::debug_set_new(self)
|
||
}
|
||
|
||
/// Creates a `DebugMap` builder designed to assist with creation of
|
||
/// `fmt::Debug` implementations for map-like structures.
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```rust
|
||
/// use std::fmt;
|
||
///
|
||
/// struct Foo(Vec<(String, i32)>);
|
||
///
|
||
/// impl fmt::Debug for Foo {
|
||
/// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
|
||
/// fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
|
||
/// }
|
||
/// }
|
||
///
|
||
/// assert_eq!(
|
||
/// format!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)])),
|
||
/// r#"{"A": 10, "B": 11}"#
|
||
/// );
|
||
/// ```
|
||
#[stable(feature = "debug_builders", since = "1.2.0")]
|
||
pub fn debug_map<'b>(&'b mut self) -> DebugMap<'b, 'a> {
|
||
builders::debug_map_new(self)
|
||
}
|
||
}
|
||
|
||
#[stable(since = "1.2.0", feature = "formatter_write")]
|
||
impl Write for Formatter<'_> {
|
||
fn write_str(&mut self, s: &str) -> Result {
|
||
self.buf.write_str(s)
|
||
}
|
||
|
||
fn write_char(&mut self, c: char) -> Result {
|
||
self.buf.write_char(c)
|
||
}
|
||
|
||
fn write_fmt(&mut self, args: Arguments<'_>) -> Result {
|
||
write(self.buf, args)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Display for Error {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Display::fmt("an error occurred when formatting an argument", f)
|
||
}
|
||
}
|
||
|
||
// Implementations of the core formatting traits
|
||
|
||
macro_rules! fmt_refs {
|
||
($($tr:ident),*) => {
|
||
$(
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + $tr> $tr for &T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result { $tr::fmt(&**self, f) }
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + $tr> $tr for &mut T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result { $tr::fmt(&**self, f) }
|
||
}
|
||
)*
|
||
}
|
||
}
|
||
|
||
fmt_refs! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperExp }
|
||
|
||
#[unstable(feature = "never_type", issue = "35121")]
|
||
impl Debug for ! {
|
||
fn fmt(&self, _: &mut Formatter<'_>) -> Result {
|
||
*self
|
||
}
|
||
}
|
||
|
||
#[unstable(feature = "never_type", issue = "35121")]
|
||
impl Display for ! {
|
||
fn fmt(&self, _: &mut Formatter<'_>) -> Result {
|
||
*self
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Debug for bool {
|
||
#[inline]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Display::fmt(self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Display for bool {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Display::fmt(if *self { "true" } else { "false" }, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Debug for str {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.write_char('"')?;
|
||
let mut from = 0;
|
||
for (i, c) in self.char_indices() {
|
||
let esc = c.escape_debug_ext(EscapeDebugExtArgs {
|
||
escape_grapheme_extended: true,
|
||
escape_single_quote: false,
|
||
escape_double_quote: true,
|
||
});
|
||
// If char needs escaping, flush backlog so far and write, else skip
|
||
if esc.len() != 1 {
|
||
f.write_str(&self[from..i])?;
|
||
for c in esc {
|
||
f.write_char(c)?;
|
||
}
|
||
from = i + c.len_utf8();
|
||
}
|
||
}
|
||
f.write_str(&self[from..])?;
|
||
f.write_char('"')
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Display for str {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.pad(self)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Debug for char {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.write_char('\'')?;
|
||
for c in self.escape_debug_ext(EscapeDebugExtArgs {
|
||
escape_grapheme_extended: true,
|
||
escape_single_quote: true,
|
||
escape_double_quote: false,
|
||
}) {
|
||
f.write_char(c)?
|
||
}
|
||
f.write_char('\'')
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Display for char {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
if f.width.is_none() && f.precision.is_none() {
|
||
f.write_char(*self)
|
||
} else {
|
||
f.pad(self.encode_utf8(&mut [0; 4]))
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Pointer for *const T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
let old_width = f.width;
|
||
let old_flags = f.flags;
|
||
|
||
// The alternate flag is already treated by LowerHex as being special-
|
||
// it denotes whether to prefix with 0x. We use it to work out whether
|
||
// or not to zero extend, and then unconditionally set it to get the
|
||
// prefix.
|
||
if f.alternate() {
|
||
f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
|
||
|
||
if f.width.is_none() {
|
||
f.width = Some((usize::BITS / 4) as usize + 2);
|
||
}
|
||
}
|
||
f.flags |= 1 << (FlagV1::Alternate as u32);
|
||
|
||
let ret = LowerHex::fmt(&(*self as *const () as usize), f);
|
||
|
||
f.width = old_width;
|
||
f.flags = old_flags;
|
||
|
||
ret
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Pointer for *mut T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Pointer::fmt(&(*self as *const T), f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Pointer for &T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Pointer::fmt(&(*self as *const T), f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Pointer for &mut T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Pointer::fmt(&(&**self as *const T), f)
|
||
}
|
||
}
|
||
|
||
// Implementation of Display/Debug for various core types
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Debug for *const T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Pointer::fmt(self, f)
|
||
}
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Debug for *mut T {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Pointer::fmt(self, f)
|
||
}
|
||
}
|
||
|
||
macro_rules! peel {
|
||
($name:ident, $($other:ident,)*) => (tuple! { $($other,)* })
|
||
}
|
||
|
||
macro_rules! tuple {
|
||
() => ();
|
||
( $($name:ident,)+ ) => (
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<$($name:Debug),+> Debug for ($($name,)+) where last_type!($($name,)+): ?Sized {
|
||
#[allow(non_snake_case, unused_assignments)]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
let mut builder = f.debug_tuple("");
|
||
let ($(ref $name,)+) = *self;
|
||
$(
|
||
builder.field(&$name);
|
||
)+
|
||
|
||
builder.finish()
|
||
}
|
||
}
|
||
peel! { $($name,)+ }
|
||
)
|
||
}
|
||
|
||
macro_rules! last_type {
|
||
($a:ident,) => { $a };
|
||
($a:ident, $($rest_a:ident,)+) => { last_type!($($rest_a,)+) };
|
||
}
|
||
|
||
tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Debug> Debug for [T] {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.debug_list().entries(self.iter()).finish()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl Debug for () {
|
||
#[inline]
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.pad("()")
|
||
}
|
||
}
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized> Debug for PhantomData<T> {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.pad("PhantomData")
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: Copy + Debug> Debug for Cell<T> {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.debug_struct("Cell").field("value", &self.get()).finish()
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + Debug> Debug for RefCell<T> {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
match self.try_borrow() {
|
||
Ok(borrow) => f.debug_struct("RefCell").field("value", &borrow).finish(),
|
||
Err(_) => {
|
||
// The RefCell is mutably borrowed so we can't look at its value
|
||
// here. Show a placeholder instead.
|
||
struct BorrowedPlaceholder;
|
||
|
||
impl Debug for BorrowedPlaceholder {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.write_str("<borrowed>")
|
||
}
|
||
}
|
||
|
||
f.debug_struct("RefCell").field("value", &BorrowedPlaceholder).finish()
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + Debug> Debug for Ref<'_, T> {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Debug::fmt(&**self, f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "rust1", since = "1.0.0")]
|
||
impl<T: ?Sized + Debug> Debug for RefMut<'_, T> {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
Debug::fmt(&*(self.deref()), f)
|
||
}
|
||
}
|
||
|
||
#[stable(feature = "core_impl_debug", since = "1.9.0")]
|
||
impl<T: ?Sized + Debug> Debug for UnsafeCell<T> {
|
||
fn fmt(&self, f: &mut Formatter<'_>) -> Result {
|
||
f.pad("UnsafeCell")
|
||
}
|
||
}
|
||
|
||
// If you expected tests to be here, look instead at the core/tests/fmt.rs file,
|
||
// it's a lot easier than creating all of the rt::Piece structures here.
|
||
// There are also tests in the alloc crate, for those that need allocations.
|