1 // Copyright 2013-2015 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Utilities for formatting and printing strings.
13 #![stable(feature = "rust1", since = "1.0.0")]
17 use cell
::{UnsafeCell, Cell, RefCell, Ref, RefMut, BorrowState}
;
18 use marker
::PhantomData
;
26 #[unstable(feature = "fmt_flags_align", issue = "27726")]
27 /// Possible alignments returned by `Formatter::align`
30 /// Indication that contents should be left-aligned.
32 /// Indication that contents should be right-aligned.
34 /// Indication that contents should be center-aligned.
36 /// No alignment was requested.
40 #[stable(feature = "debug_builders", since = "1.2.0")]
41 pub use self::builders
::{DebugStruct, DebugTuple, DebugSet, DebugList, DebugMap}
;
46 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
53 #[stable(feature = "rust1", since = "1.0.0")]
54 /// The type returned by formatter methods.
55 pub type Result
= result
::Result
<(), Error
>;
57 /// The error type which is returned from formatting a message into a stream.
59 /// This type does not support transmission of an error other than that an error
60 /// occurred. Any extra information must be arranged to be transmitted through
62 #[stable(feature = "rust1", since = "1.0.0")]
63 #[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
66 /// A collection of methods that are required to format a message into a stream.
68 /// This trait is the type which this modules requires when formatting
69 /// information. This is similar to the standard library's `io::Write` trait,
70 /// but it is only intended for use in libcore.
72 /// This trait should generally not be implemented by consumers of the standard
73 /// library. The `write!` macro accepts an instance of `io::Write`, and the
74 /// `io::Write` trait is favored over implementing this trait.
75 #[stable(feature = "rust1", since = "1.0.0")]
77 /// Writes a slice of bytes into this writer, returning whether the write
80 /// This method can only succeed if the entire byte slice was successfully
81 /// written, and this method will not return until all data has been
82 /// written or an error occurs.
86 /// This function will return an instance of `Error` on error.
87 #[stable(feature = "rust1", since = "1.0.0")]
88 fn write_str(&mut self, s
: &str) -> Result
;
90 /// Writes a `char` into this writer, returning whether the write succeeded.
92 /// A single `char` may be encoded as more than one byte.
93 /// This method can only succeed if the entire byte sequence was successfully
94 /// written, and this method will not return until all data has been
95 /// written or an error occurs.
99 /// This function will return an instance of `Error` on error.
100 #[stable(feature = "fmt_write_char", since = "1.1.0")]
101 fn write_char(&mut self, c
: char) -> Result
{
102 self.write_str(unsafe {
103 str::from_utf8_unchecked(c
.encode_utf8().as_slice())
107 /// Glue for usage of the `write!` macro with implementors of this trait.
109 /// This method should generally not be invoked manually, but rather through
110 /// the `write!` macro itself.
111 #[stable(feature = "rust1", since = "1.0.0")]
112 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
113 // This Adapter is needed to allow `self` (of type `&mut
114 // Self`) to be cast to a Write (below) without
115 // requiring a `Sized` bound.
116 struct Adapter
<'a
,T
: ?Sized
+'a
>(&'a
mut T
);
118 impl<'a
, T
: ?Sized
> Write
for Adapter
<'a
, T
>
121 fn write_str(&mut self, s
: &str) -> Result
{
125 fn write_char(&mut self, c
: char) -> Result
{
129 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
130 self.0.write_fmt(args
)
134 write(&mut Adapter(self), args
)
138 #[stable(feature = "fmt_write_blanket_impl", since = "1.4.0")]
139 impl<'a
, W
: Write
+ ?Sized
> Write
for &'a
mut W
{
140 fn write_str(&mut self, s
: &str) -> Result
{
141 (**self).write_str(s
)
144 fn write_char(&mut self, c
: char) -> Result
{
145 (**self).write_char(c
)
148 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
149 (**self).write_fmt(args
)
153 /// A struct to represent both where to emit formatting strings to and how they
154 /// should be formatted. A mutable version of this is passed to all formatting
156 #[allow(missing_debug_implementations)]
157 #[stable(feature = "rust1", since = "1.0.0")]
158 pub struct Formatter
<'a
> {
161 align
: rt
::v1
::Alignment
,
162 width
: Option
<usize>,
163 precision
: Option
<usize>,
165 buf
: &'a
mut (Write
+'a
),
166 curarg
: slice
::Iter
<'a
, ArgumentV1
<'a
>>,
167 args
: &'a
[ArgumentV1
<'a
>],
170 // NB. Argument is essentially an optimized partially applied formatting function,
171 // equivalent to `exists T.(&T, fn(&T, &mut Formatter) -> Result`.
175 /// This struct represents the generic "argument" which is taken by the Xprintf
176 /// family of functions. It contains a function to format the given value. At
177 /// compile time it is ensured that the function and the value have the correct
178 /// types, and then this struct is used to canonicalize arguments to one type.
180 #[allow(missing_debug_implementations)]
181 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
184 pub struct ArgumentV1
<'a
> {
186 formatter
: fn(&Void
, &mut Formatter
) -> Result
,
189 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
191 impl<'a
> Clone
for ArgumentV1
<'a
> {
192 fn clone(&self) -> ArgumentV1
<'a
> {
197 impl<'a
> ArgumentV1
<'a
> {
199 fn show_usize(x
: &usize, f
: &mut Formatter
) -> Result
{
204 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
206 pub fn new
<'b
, T
>(x
: &'b T
,
207 f
: fn(&T
, &mut Formatter
) -> Result
) -> ArgumentV1
<'b
> {
210 formatter
: mem
::transmute(f
),
211 value
: mem
::transmute(x
)
217 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
219 pub fn from_usize(x
: &usize) -> ArgumentV1
{
220 ArgumentV1
::new(x
, ArgumentV1
::show_usize
)
223 fn as_usize(&self) -> Option
<usize> {
224 if self.formatter
as usize == ArgumentV1
::show_usize
as usize {
225 Some(unsafe { *(self.value as *const _ as *const usize) }
)
232 // flags available in the v1 format of format_args
233 #[derive(Copy, Clone)]
234 #[allow(dead_code)] // SignMinus isn't currently used
235 enum FlagV1 { SignPlus, SignMinus, Alternate, SignAwareZeroPad, }
237 impl<'a
> Arguments
<'a
> {
238 /// When using the format_args!() macro, this function is used to generate the
239 /// Arguments structure.
240 #[doc(hidden)] #[inline]
241 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
243 pub fn new_v1(pieces
: &'a
[&'a
str],
244 args
: &'a
[ArgumentV1
<'a
>]) -> Arguments
<'a
> {
252 /// This function is used to specify nonstandard formatting parameters.
253 /// The `pieces` array must be at least as long as `fmt` to construct
254 /// a valid Arguments structure. Also, any `Count` within `fmt` that is
255 /// `CountIsParam` or `CountIsNextParam` has to point to an argument
256 /// created with `argumentusize`. However, failing to do so doesn't cause
257 /// unsafety, but will ignore invalid .
258 #[doc(hidden)] #[inline]
259 #[unstable(feature = "fmt_internals", reason = "internal to format_args!",
261 pub fn new_v1_formatted(pieces
: &'a
[&'a
str],
262 args
: &'a
[ArgumentV1
<'a
>],
263 fmt
: &'a
[rt
::v1
::Argument
]) -> Arguments
<'a
> {
272 /// This structure represents a safely precompiled version of a format string
273 /// and its arguments. This cannot be generated at runtime because it cannot
274 /// safely be done so, so no constructors are given and the fields are private
275 /// to prevent modification.
277 /// The `format_args!` macro will safely create an instance of this structure
278 /// and pass it to a function or closure, passed as the first argument. The
279 /// macro validates the format string at compile-time so usage of the `write`
280 /// and `format` functions can be safely performed.
281 #[stable(feature = "rust1", since = "1.0.0")]
282 #[derive(Copy, Clone)]
283 pub struct Arguments
<'a
> {
284 // Format string pieces to print.
285 pieces
: &'a
[&'a
str],
287 // Placeholder specs, or `None` if all specs are default (as in "{}{}").
288 fmt
: Option
<&'a
[rt
::v1
::Argument
]>,
290 // Dynamic arguments for interpolation, to be interleaved with string
291 // pieces. (Every argument is preceded by a string piece.)
292 args
: &'a
[ArgumentV1
<'a
>],
295 #[stable(feature = "rust1", since = "1.0.0")]
296 impl<'a
> Debug
for Arguments
<'a
> {
297 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
298 Display
::fmt(self, fmt
)
302 #[stable(feature = "rust1", since = "1.0.0")]
303 impl<'a
> Display
for Arguments
<'a
> {
304 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
305 write(fmt
.buf
, *self)
309 /// Format trait for the `?` character.
311 /// `Debug` should format the output in a programmer-facing, debugging context.
313 /// Generally speaking, you should just `derive` a `Debug` implementation.
315 /// When used with the alternate format specifier `#?`, the output is pretty-printed.
317 /// For more information on formatters, see [the module-level documentation][module].
319 /// [module]: ../../std/fmt/index.html
321 /// This trait can be used with `#[derive]` if all fields implement `Debug`. When
322 /// `derive`d for structs, it will use the name of the `struct`, then `{`, then a
323 /// comma-separated list of each field's name and `Debug` value, then `}`. For
324 /// `enum`s, it will use the name of the variant and, if applicable, `(`, then the
325 /// `Debug` values of the fields, then `)`.
329 /// Deriving an implementation:
338 /// let origin = Point { x: 0, y: 0 };
340 /// println!("The origin is: {:?}", origin);
343 /// Manually implementing:
353 /// impl fmt::Debug for Point {
354 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
355 /// write!(f, "Point {{ x: {}, y: {} }}", self.x, self.y)
359 /// let origin = Point { x: 0, y: 0 };
361 /// println!("The origin is: {:?}", origin);
367 /// The origin is: Point { x: 0, y: 0 }
370 /// There are a number of `debug_*` methods on `Formatter` to help you with manual
371 /// implementations, such as [`debug_struct`][debug_struct].
373 /// `Debug` implementations using either `derive` or the debug builder API
374 /// on `Formatter` support pretty printing using the alternate flag: `{:#?}`.
376 /// [debug_struct]: ../../std/fmt/struct.Formatter.html#method.debug_struct
378 /// Pretty printing with `#?`:
387 /// let origin = Point { x: 0, y: 0 };
389 /// println!("The origin is: {:#?}", origin);
395 /// The origin is: Point {
400 #[stable(feature = "rust1", since = "1.0.0")]
401 #[rustc_on_unimplemented = "`{Self}` cannot be formatted using `:?`; if it is \
402 defined in your crate, add `#[derive(Debug)]` or \
403 manually implement it"]
404 #[lang = "debug_trait"]
406 /// Formats the value using the given formatter.
407 #[stable(feature = "rust1", since = "1.0.0")]
408 fn fmt(&self, &mut Formatter
) -> Result
;
411 /// Format trait for an empty format, `{}`.
413 /// `Display` is similar to [`Debug`][debug], but `Display` is for user-facing
414 /// output, and so cannot be derived.
416 /// [debug]: trait.Debug.html
418 /// For more information on formatters, see [the module-level documentation][module].
420 /// [module]: ../../std/fmt/index.html
424 /// Implementing `Display` on a type:
434 /// impl fmt::Display for Point {
435 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
436 /// write!(f, "({}, {})", self.x, self.y)
440 /// let origin = Point { x: 0, y: 0 };
442 /// println!("The origin is: {}", origin);
444 #[rustc_on_unimplemented = "`{Self}` cannot be formatted with the default \
445 formatter; try using `:?` instead if you are using \
447 #[stable(feature = "rust1", since = "1.0.0")]
449 /// Formats the value using the given formatter.
450 #[stable(feature = "rust1", since = "1.0.0")]
451 fn fmt(&self, &mut Formatter
) -> Result
;
454 /// Format trait for the `o` character.
456 /// The `Octal` trait should format its output as a number in base-8.
458 /// The alternate flag, `#`, adds a `0o` in front of the output.
460 /// For more information on formatters, see [the module-level documentation][module].
462 /// [module]: ../../std/fmt/index.html
466 /// Basic usage with `i32`:
469 /// let x = 42; // 42 is '52' in octal
471 /// assert_eq!(format!("{:o}", x), "52");
472 /// assert_eq!(format!("{:#o}", x), "0o52");
475 /// Implementing `Octal` on a type:
480 /// struct Length(i32);
482 /// impl fmt::Octal for Length {
483 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
484 /// let val = self.0;
486 /// write!(f, "{:o}", val) // delegate to i32's implementation
490 /// let l = Length(9);
492 /// println!("l as octal is: {:o}", l);
494 #[stable(feature = "rust1", since = "1.0.0")]
496 /// Formats the value using the given formatter.
497 #[stable(feature = "rust1", since = "1.0.0")]
498 fn fmt(&self, &mut Formatter
) -> Result
;
501 /// Format trait for the `b` character.
503 /// The `Binary` trait should format its output as a number in binary.
505 /// The alternate flag, `#`, adds a `0b` in front of the output.
507 /// For more information on formatters, see [the module-level documentation][module].
509 /// [module]: ../../std/fmt/index.html
513 /// Basic usage with `i32`:
516 /// let x = 42; // 42 is '101010' in binary
518 /// assert_eq!(format!("{:b}", x), "101010");
519 /// assert_eq!(format!("{:#b}", x), "0b101010");
522 /// Implementing `Binary` on a type:
527 /// struct Length(i32);
529 /// impl fmt::Binary for Length {
530 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
531 /// let val = self.0;
533 /// write!(f, "{:b}", val) // delegate to i32's implementation
537 /// let l = Length(107);
539 /// println!("l as binary is: {:b}", l);
541 #[stable(feature = "rust1", since = "1.0.0")]
543 /// Formats the value using the given formatter.
544 #[stable(feature = "rust1", since = "1.0.0")]
545 fn fmt(&self, &mut Formatter
) -> Result
;
548 /// Format trait for the `x` character.
550 /// The `LowerHex` trait should format its output as a number in hexadecimal, with `a` through `f`
553 /// The alternate flag, `#`, adds a `0x` in front of the output.
555 /// For more information on formatters, see [the module-level documentation][module].
557 /// [module]: ../../std/fmt/index.html
561 /// Basic usage with `i32`:
564 /// let x = 42; // 42 is '2a' in hex
566 /// assert_eq!(format!("{:x}", x), "2a");
567 /// assert_eq!(format!("{:#x}", x), "0x2a");
570 /// Implementing `LowerHex` on a type:
575 /// struct Length(i32);
577 /// impl fmt::LowerHex for Length {
578 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
579 /// let val = self.0;
581 /// write!(f, "{:x}", val) // delegate to i32's implementation
585 /// let l = Length(9);
587 /// println!("l as hex is: {:x}", l);
589 #[stable(feature = "rust1", since = "1.0.0")]
591 /// Formats the value using the given formatter.
592 #[stable(feature = "rust1", since = "1.0.0")]
593 fn fmt(&self, &mut Formatter
) -> Result
;
596 /// Format trait for the `X` character.
598 /// The `UpperHex` trait should format its output as a number in hexadecimal, with `A` through `F`
601 /// The alternate flag, `#`, adds a `0x` in front of the output.
603 /// For more information on formatters, see [the module-level documentation][module].
605 /// [module]: ../../std/fmt/index.html
609 /// Basic usage with `i32`:
612 /// let x = 42; // 42 is '2A' in hex
614 /// assert_eq!(format!("{:X}", x), "2A");
615 /// assert_eq!(format!("{:#X}", x), "0x2A");
618 /// Implementing `UpperHex` on a type:
623 /// struct Length(i32);
625 /// impl fmt::UpperHex for Length {
626 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
627 /// let val = self.0;
629 /// write!(f, "{:X}", val) // delegate to i32's implementation
633 /// let l = Length(9);
635 /// println!("l as hex is: {:X}", l);
637 #[stable(feature = "rust1", since = "1.0.0")]
639 /// Formats the value using the given formatter.
640 #[stable(feature = "rust1", since = "1.0.0")]
641 fn fmt(&self, &mut Formatter
) -> Result
;
644 /// Format trait for the `p` character.
646 /// The `Pointer` trait should format its output as a memory location. This is commonly presented
649 /// For more information on formatters, see [the module-level documentation][module].
651 /// [module]: ../../std/fmt/index.html
655 /// Basic usage with `&i32`:
660 /// let address = format!("{:p}", x); // this produces something like '0x7f06092ac6d0'
663 /// Implementing `Pointer` on a type:
668 /// struct Length(i32);
670 /// impl fmt::Pointer for Length {
671 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
672 /// // use `as` to convert to a `*const T`, which implements Pointer, which we can use
674 /// write!(f, "{:p}", self as *const Length)
678 /// let l = Length(42);
680 /// println!("l is in memory here: {:p}", l);
682 #[stable(feature = "rust1", since = "1.0.0")]
684 /// Formats the value using the given formatter.
685 #[stable(feature = "rust1", since = "1.0.0")]
686 fn fmt(&self, &mut Formatter
) -> Result
;
689 /// Format trait for the `e` character.
691 /// The `LowerExp` trait should format its output in scientific notation with a lower-case `e`.
693 /// For more information on formatters, see [the module-level documentation][module].
695 /// [module]: ../../std/fmt/index.html
699 /// Basic usage with `i32`:
702 /// let x = 42.0; // 42.0 is '4.2e1' in scientific notation
704 /// assert_eq!(format!("{:e}", x), "4.2e1");
707 /// Implementing `LowerExp` on a type:
712 /// struct Length(i32);
714 /// impl fmt::LowerExp for Length {
715 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
716 /// let val = self.0;
717 /// write!(f, "{}e1", val / 10)
721 /// let l = Length(100);
723 /// println!("l in scientific notation is: {:e}", l);
725 #[stable(feature = "rust1", since = "1.0.0")]
727 /// Formats the value using the given formatter.
728 #[stable(feature = "rust1", since = "1.0.0")]
729 fn fmt(&self, &mut Formatter
) -> Result
;
732 /// Format trait for the `E` character.
734 /// The `UpperExp` trait should format its output in scientific notation with an upper-case `E`.
736 /// For more information on formatters, see [the module-level documentation][module].
738 /// [module]: ../../std/fmt/index.html
742 /// Basic usage with `f32`:
745 /// let x = 42.0; // 42.0 is '4.2E1' in scientific notation
747 /// assert_eq!(format!("{:E}", x), "4.2E1");
750 /// Implementing `UpperExp` on a type:
755 /// struct Length(i32);
757 /// impl fmt::UpperExp for Length {
758 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
759 /// let val = self.0;
760 /// write!(f, "{}E1", val / 10)
764 /// let l = Length(100);
766 /// println!("l in scientific notation is: {:E}", l);
768 #[stable(feature = "rust1", since = "1.0.0")]
770 /// Formats the value using the given formatter.
771 #[stable(feature = "rust1", since = "1.0.0")]
772 fn fmt(&self, &mut Formatter
) -> Result
;
775 /// The `write` function takes an output stream, a precompiled format string,
776 /// and a list of arguments. The arguments will be formatted according to the
777 /// specified format string into the output stream provided.
781 /// * output - the buffer to write output to
782 /// * args - the precompiled arguments generated by `format_args!`
791 /// let mut output = String::new();
792 /// fmt::write(&mut output, format_args!("Hello {}!", "world"))
793 /// .expect("Error occurred while trying to write in String");
794 /// assert_eq!(output, "Hello world!");
797 /// Please note that using [`write!`][write_macro] might be preferrable. Example:
800 /// use std::fmt::Write;
802 /// let mut output = String::new();
803 /// write!(&mut output, "Hello {}!", "world")
804 /// .expect("Error occurred while trying to write in String");
805 /// assert_eq!(output, "Hello world!");
808 /// [write_macro]: ../../std/macro.write!.html
809 #[stable(feature = "rust1", since = "1.0.0")]
810 pub fn write(output
: &mut Write
, args
: Arguments
) -> Result
{
811 let mut formatter
= Formatter
{
816 align
: rt
::v1
::Alignment
::Unknown
,
819 curarg
: args
.args
.iter(),
822 let mut pieces
= args
.pieces
.iter();
826 // We can use default formatting parameters for all arguments.
827 for (arg
, piece
) in args
.args
.iter().zip(pieces
.by_ref()) {
828 formatter
.buf
.write_str(*piece
)?
;
829 (arg
.formatter
)(arg
.value
, &mut formatter
)?
;
833 // Every spec has a corresponding argument that is preceded by
835 for (arg
, piece
) in fmt
.iter().zip(pieces
.by_ref()) {
836 formatter
.buf
.write_str(*piece
)?
;
842 // There can be only one trailing string piece left.
843 if let Some(piece
) = pieces
.next() {
844 formatter
.buf
.write_str(*piece
)?
;
850 impl<'a
> Formatter
<'a
> {
852 // First up is the collection of functions used to execute a format string
853 // at runtime. This consumes all of the compile-time statics generated by
854 // the format! syntax extension.
855 fn run(&mut self, arg
: &rt
::v1
::Argument
) -> Result
{
856 // Fill in the format parameters into the formatter
857 self.fill
= arg
.format
.fill
;
858 self.align
= arg
.format
.align
;
859 self.flags
= arg
.format
.flags
;
860 self.width
= self.getcount(&arg
.format
.width
);
861 self.precision
= self.getcount(&arg
.format
.precision
);
863 // Extract the correct argument
864 let value
= match arg
.position
{
865 rt
::v1
::Position
::Next
=> { *self.curarg.next().unwrap() }
866 rt
::v1
::Position
::At(i
) => self.args
[i
],
869 // Then actually do some printing
870 (value
.formatter
)(value
.value
, self)
873 fn getcount(&mut self, cnt
: &rt
::v1
::Count
) -> Option
<usize> {
875 rt
::v1
::Count
::Is(n
) => Some(n
),
876 rt
::v1
::Count
::Implied
=> None
,
877 rt
::v1
::Count
::Param(i
) => {
878 self.args
[i
].as_usize()
880 rt
::v1
::Count
::NextParam
=> {
881 self.curarg
.next().and_then(|arg
| arg
.as_usize())
886 // Helper methods used for padding and processing formatting arguments that
887 // all formatting traits can use.
889 /// Performs the correct padding for an integer which has already been
890 /// emitted into a str. The str should *not* contain the sign for the
891 /// integer, that will be added by this method.
895 /// * is_nonnegative - whether the original integer was either positive or zero.
896 /// * prefix - if the '#' character (Alternate) is provided, this
897 /// is the prefix to put in front of the number.
898 /// * buf - the byte array that the number has been formatted into
900 /// This function will correctly account for the flags provided as well as
901 /// the minimum width. It will not take precision into account.
902 #[stable(feature = "rust1", since = "1.0.0")]
903 pub fn pad_integral(&mut self,
904 is_nonnegative
: bool
,
910 let mut width
= buf
.len();
914 sign
= Some('
-'
); width
+= 1;
915 } else if self.sign_plus() {
916 sign
= Some('
+'
); width
+= 1;
919 let mut prefixed
= false;
920 if self.alternate() {
921 prefixed
= true; width
+= prefix
.chars().count();
924 // Writes the sign if it exists, and then the prefix if it was requested
925 let write_prefix
= |f
: &mut Formatter
| {
926 if let Some(c
) = sign
{
927 f
.buf
.write_str(unsafe {
928 str::from_utf8_unchecked(c
.encode_utf8().as_slice())
931 if prefixed { f.buf.write_str(prefix) }
935 // The `width` field is more of a `min-width` parameter at this point.
937 // If there's no minimum length requirements then we can just
940 write_prefix(self)?
; self.buf
.write_str(buf
)
942 // Check if we're over the minimum width, if so then we can also
943 // just write the bytes.
944 Some(min
) if width
>= min
=> {
945 write_prefix(self)?
; self.buf
.write_str(buf
)
947 // The sign and prefix goes before the padding if the fill character
949 Some(min
) if self.sign_aware_zero_pad() => {
952 self.with_padding(min
- width
, rt
::v1
::Alignment
::Right
, |f
| {
956 // Otherwise, the sign and prefix goes after the padding
958 self.with_padding(min
- width
, rt
::v1
::Alignment
::Right
, |f
| {
959 write_prefix(f
)?
; f
.buf
.write_str(buf
)
965 /// This function takes a string slice and emits it to the internal buffer
966 /// after applying the relevant formatting flags specified. The flags
967 /// recognized for generic strings are:
969 /// * width - the minimum width of what to emit
970 /// * fill/align - what to emit and where to emit it if the string
971 /// provided needs to be padded
972 /// * precision - the maximum length to emit, the string is truncated if it
973 /// is longer than this length
975 /// Notably this function ignored the `flag` parameters
976 #[stable(feature = "rust1", since = "1.0.0")]
977 pub fn pad(&mut self, s
: &str) -> Result
{
978 // Make sure there's a fast path up front
979 if self.width
.is_none() && self.precision
.is_none() {
980 return self.buf
.write_str(s
);
982 // The `precision` field can be interpreted as a `max-width` for the
983 // string being formatted.
984 let s
= if let Some(max
) = self.precision
{
985 // If our string is longer that the precision, then we must have
986 // truncation. However other flags like `fill`, `width` and `align`
987 // must act as always.
988 if let Some((i
, _
)) = s
.char_indices().skip(max
).next() {
996 // The `width` field is more of a `min-width` parameter at this point.
998 // If we're under the maximum length, and there's no minimum length
999 // requirements, then we can just emit the string
1000 None
=> self.buf
.write_str(s
),
1001 // If we're under the maximum width, check if we're over the minimum
1002 // width, if so it's as easy as just emitting the string.
1003 Some(width
) if s
.chars().count() >= width
=> {
1004 self.buf
.write_str(s
)
1006 // If we're under both the maximum and the minimum width, then fill
1007 // up the minimum width with the specified string + some alignment.
1009 let align
= rt
::v1
::Alignment
::Left
;
1010 self.with_padding(width
- s
.chars().count(), align
, |me
| {
1017 /// Runs a callback, emitting the correct padding either before or
1018 /// afterwards depending on whether right or left alignment is requested.
1019 fn with_padding
<F
>(&mut self, padding
: usize, default: rt
::v1
::Alignment
,
1021 where F
: FnOnce(&mut Formatter
) -> Result
,
1024 let align
= match self.align
{
1025 rt
::v1
::Alignment
::Unknown
=> default,
1029 let (pre_pad
, post_pad
) = match align
{
1030 rt
::v1
::Alignment
::Left
=> (0, padding
),
1031 rt
::v1
::Alignment
::Right
|
1032 rt
::v1
::Alignment
::Unknown
=> (padding
, 0),
1033 rt
::v1
::Alignment
::Center
=> (padding
/ 2, (padding
+ 1) / 2),
1036 let fill
= self.fill
.encode_utf8();
1038 str::from_utf8_unchecked(fill
.as_slice())
1041 for _
in 0..pre_pad
{
1042 self.buf
.write_str(fill
)?
;
1047 for _
in 0..post_pad
{
1048 self.buf
.write_str(fill
)?
;
1054 /// Takes the formatted parts and applies the padding.
1055 /// Assumes that the caller already has rendered the parts with required precision,
1056 /// so that `self.precision` can be ignored.
1057 fn pad_formatted_parts(&mut self, formatted
: &flt2dec
::Formatted
) -> Result
{
1058 if let Some(mut width
) = self.width
{
1059 // for the sign-aware zero padding, we render the sign first and
1060 // behave as if we had no sign from the beginning.
1061 let mut formatted
= formatted
.clone();
1062 let mut align
= self.align
;
1063 let old_fill
= self.fill
;
1064 if self.sign_aware_zero_pad() {
1065 // a sign always goes first
1066 let sign
= unsafe { str::from_utf8_unchecked(formatted.sign) }
;
1067 self.buf
.write_str(sign
)?
;
1069 // remove the sign from the formatted parts
1070 formatted
.sign
= b
"";
1071 width
= if width
< sign
.len() { 0 }
else { width - sign.len() }
;
1072 align
= rt
::v1
::Alignment
::Right
;
1076 // remaining parts go through the ordinary padding process.
1077 let len
= formatted
.len();
1078 let ret
= if width
<= len
{ // no padding
1079 self.write_formatted_parts(&formatted
)
1081 self.with_padding(width
- len
, align
, |f
| {
1082 f
.write_formatted_parts(&formatted
)
1085 self.fill
= old_fill
;
1088 // this is the common case and we take a shortcut
1089 self.write_formatted_parts(formatted
)
1093 fn write_formatted_parts(&mut self, formatted
: &flt2dec
::Formatted
) -> Result
{
1094 fn write_bytes(buf
: &mut Write
, s
: &[u8]) -> Result
{
1095 buf
.write_str(unsafe { str::from_utf8_unchecked(s) }
)
1098 if !formatted
.sign
.is_empty() {
1099 write_bytes(self.buf
, formatted
.sign
)?
;
1101 for part
in formatted
.parts
{
1103 flt2dec
::Part
::Zero(mut nzeroes
) => {
1104 const ZEROES
: &'
static str = // 64 zeroes
1105 "0000000000000000000000000000000000000000000000000000000000000000";
1106 while nzeroes
> ZEROES
.len() {
1107 self.buf
.write_str(ZEROES
)?
;
1108 nzeroes
-= ZEROES
.len();
1111 self.buf
.write_str(&ZEROES
[..nzeroes
])?
;
1114 flt2dec
::Part
::Num(mut v
) => {
1116 let len
= part
.len();
1117 for c
in s
[..len
].iter_mut().rev() {
1118 *c
= b'
0'
+ (v
% 10) as u8;
1121 write_bytes(self.buf
, &s
[..len
])?
;
1123 flt2dec
::Part
::Copy(buf
) => {
1124 write_bytes(self.buf
, buf
)?
;
1131 /// Writes some data to the underlying buffer contained within this
1133 #[stable(feature = "rust1", since = "1.0.0")]
1134 pub fn write_str(&mut self, data
: &str) -> Result
{
1135 self.buf
.write_str(data
)
1138 /// Writes some formatted information into this instance
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 pub fn write_fmt(&mut self, fmt
: Arguments
) -> Result
{
1141 write(self.buf
, fmt
)
1144 /// Flags for formatting (packed version of rt::Flag)
1145 #[stable(feature = "rust1", since = "1.0.0")]
1146 pub fn flags(&self) -> u32 { self.flags }
1148 /// Character used as 'fill' whenever there is alignment
1149 #[stable(feature = "fmt_flags", since = "1.5.0")]
1150 pub fn fill(&self) -> char { self.fill }
1152 /// Flag indicating what form of alignment was requested
1153 #[unstable(feature = "fmt_flags_align", reason = "method was just created",
1155 pub fn align(&self) -> Alignment
{
1157 rt
::v1
::Alignment
::Left
=> Alignment
::Left
,
1158 rt
::v1
::Alignment
::Right
=> Alignment
::Right
,
1159 rt
::v1
::Alignment
::Center
=> Alignment
::Center
,
1160 rt
::v1
::Alignment
::Unknown
=> Alignment
::Unknown
,
1164 /// Optionally specified integer width that the output should be
1165 #[stable(feature = "fmt_flags", since = "1.5.0")]
1166 pub fn width(&self) -> Option
<usize> { self.width }
1168 /// Optionally specified precision for numeric types
1169 #[stable(feature = "fmt_flags", since = "1.5.0")]
1170 pub fn precision(&self) -> Option
<usize> { self.precision }
1172 /// Determines if the `+` flag was specified.
1173 #[stable(feature = "fmt_flags", since = "1.5.0")]
1174 pub fn sign_plus(&self) -> bool { self.flags & (1 << FlagV1::SignPlus as u32) != 0 }
1176 /// Determines if the `-` flag was specified.
1177 #[stable(feature = "fmt_flags", since = "1.5.0")]
1178 pub fn sign_minus(&self) -> bool { self.flags & (1 << FlagV1::SignMinus as u32) != 0 }
1180 /// Determines if the `#` flag was specified.
1181 #[stable(feature = "fmt_flags", since = "1.5.0")]
1182 pub fn alternate(&self) -> bool { self.flags & (1 << FlagV1::Alternate as u32) != 0 }
1184 /// Determines if the `0` flag was specified.
1185 #[stable(feature = "fmt_flags", since = "1.5.0")]
1186 pub fn sign_aware_zero_pad(&self) -> bool
{
1187 self.flags
& (1 << FlagV1
::SignAwareZeroPad
as u32) != 0
1190 /// Creates a `DebugStruct` builder designed to assist with creation of
1191 /// `fmt::Debug` implementations for structs.
1203 /// impl fmt::Debug for Foo {
1204 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
1205 /// fmt.debug_struct("Foo")
1206 /// .field("bar", &self.bar)
1207 /// .field("baz", &self.baz)
1212 /// // prints "Foo { bar: 10, baz: "Hello World" }"
1213 /// println!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() });
1215 #[stable(feature = "debug_builders", since = "1.2.0")]
1217 pub fn debug_struct
<'b
>(&'b
mut self, name
: &str) -> DebugStruct
<'b
, 'a
> {
1218 builders
::debug_struct_new(self, name
)
1221 /// Creates a `DebugTuple` builder designed to assist with creation of
1222 /// `fmt::Debug` implementations for tuple structs.
1229 /// struct Foo(i32, String);
1231 /// impl fmt::Debug for Foo {
1232 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
1233 /// fmt.debug_tuple("Foo")
1240 /// // prints "Foo(10, "Hello World")"
1241 /// println!("{:?}", Foo(10, "Hello World".to_string()));
1243 #[stable(feature = "debug_builders", since = "1.2.0")]
1245 pub fn debug_tuple
<'b
>(&'b
mut self, name
: &str) -> DebugTuple
<'b
, 'a
> {
1246 builders
::debug_tuple_new(self, name
)
1249 /// Creates a `DebugList` builder designed to assist with creation of
1250 /// `fmt::Debug` implementations for list-like structures.
1257 /// struct Foo(Vec<i32>);
1259 /// impl fmt::Debug for Foo {
1260 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
1261 /// fmt.debug_list().entries(self.0.iter()).finish()
1265 /// // prints "[10, 11]"
1266 /// println!("{:?}", Foo(vec![10, 11]));
1268 #[stable(feature = "debug_builders", since = "1.2.0")]
1270 pub fn debug_list
<'b
>(&'b
mut self) -> DebugList
<'b
, 'a
> {
1271 builders
::debug_list_new(self)
1274 /// Creates a `DebugSet` builder designed to assist with creation of
1275 /// `fmt::Debug` implementations for set-like structures.
1282 /// struct Foo(Vec<i32>);
1284 /// impl fmt::Debug for Foo {
1285 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
1286 /// fmt.debug_set().entries(self.0.iter()).finish()
1290 /// // prints "{10, 11}"
1291 /// println!("{:?}", Foo(vec![10, 11]));
1293 #[stable(feature = "debug_builders", since = "1.2.0")]
1295 pub fn debug_set
<'b
>(&'b
mut self) -> DebugSet
<'b
, 'a
> {
1296 builders
::debug_set_new(self)
1299 /// Creates a `DebugMap` builder designed to assist with creation of
1300 /// `fmt::Debug` implementations for map-like structures.
1307 /// struct Foo(Vec<(String, i32)>);
1309 /// impl fmt::Debug for Foo {
1310 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
1311 /// fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
1315 /// // prints "{"A": 10, "B": 11}"
1316 /// println!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)]));
1318 #[stable(feature = "debug_builders", since = "1.2.0")]
1320 pub fn debug_map
<'b
>(&'b
mut self) -> DebugMap
<'b
, 'a
> {
1321 builders
::debug_map_new(self)
1325 #[stable(since = "1.2.0", feature = "formatter_write")]
1326 impl<'a
> Write
for Formatter
<'a
> {
1327 fn write_str(&mut self, s
: &str) -> Result
{
1328 self.buf
.write_str(s
)
1331 fn write_char(&mut self, c
: char) -> Result
{
1332 self.buf
.write_char(c
)
1335 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
1336 write(self.buf
, args
)
1340 #[stable(feature = "rust1", since = "1.0.0")]
1341 impl Display
for Error
{
1342 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1343 Display
::fmt("an error occurred when formatting an argument", f
)
1347 // Implementations of the core formatting traits
1349 macro_rules
! fmt_refs
{
1350 ($
($tr
:ident
),*) => {
1352 #[stable(feature = "rust1", since = "1.0.0")]
1353 impl<'a
, T
: ?Sized
+ $tr
> $tr
for &'a T
{
1354 fn fmt(&self, f
: &mut Formatter
) -> Result { $tr::fmt(&**self, f) }
1356 #[stable(feature = "rust1", since = "1.0.0")]
1357 impl<'a
, T
: ?Sized
+ $tr
> $tr
for &'a
mut T
{
1358 fn fmt(&self, f
: &mut Formatter
) -> Result { $tr::fmt(&**self, f) }
1364 fmt_refs
! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperExp }
1366 // Note: This macro is a temporary hack that can be remove once we are building with a compiler
1367 // that supports `!`
1368 macro_rules
! not_stage0
{
1370 #[unstable(feature = "never_type", issue = "35121")]
1372 fn fmt(&self, _
: &mut Formatter
) -> Result
{
1377 #[unstable(feature = "never_type", issue = "35121")]
1378 impl Display
for ! {
1379 fn fmt(&self, _
: &mut Formatter
) -> Result
{
1389 #[stable(feature = "rust1", since = "1.0.0")]
1390 impl Debug
for bool
{
1391 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1392 Display
::fmt(self, f
)
1396 #[stable(feature = "rust1", since = "1.0.0")]
1397 impl Display
for bool
{
1398 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1399 Display
::fmt(if *self { "true" }
else { "false" }
, f
)
1403 #[stable(feature = "rust1", since = "1.0.0")]
1404 impl Debug
for str {
1405 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1408 for (i, c) in self.char_indices() {
1409 let esc = c.escape_debug();
1410 // If char needs escaping, flush backlog so far and write, else skip
1412 f.write_str(&self[from..i])?;
1416 from = i + c.len_utf8();
1419 f.write_str(&self[from..])?;
1424 #[stable(feature = "rust1", since = "1.0.0")]
1425 impl Display
for str {
1426 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1431 #[stable(feature = "rust1", since = "1.0.0")]
1432 impl Debug
for char {
1433 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1434 f
.write_char('
\''
)?
;
1435 for c
in self.escape_debug() {
1442 #[stable(feature = "rust1", since = "1.0.0")]
1443 impl Display
for char {
1444 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1445 if f
.width
.is_none() && f
.precision
.is_none() {
1449 str::from_utf8_unchecked(self.encode_utf8().as_slice())
1455 #[stable(feature = "rust1", since = "1.0.0")]
1456 impl<T
: ?Sized
> Pointer
for *const T
{
1457 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1458 let old_width
= f
.width
;
1459 let old_flags
= f
.flags
;
1461 // The alternate flag is already treated by LowerHex as being special-
1462 // it denotes whether to prefix with 0x. We use it to work out whether
1463 // or not to zero extend, and then unconditionally set it to get the
1466 f
.flags
|= 1 << (FlagV1
::SignAwareZeroPad
as u32);
1468 if let None
= f
.width
{
1469 f
.width
= Some(((mem
::size_of
::<usize>() * 8) / 4) + 2);
1472 f
.flags
|= 1 << (FlagV1
::Alternate
as u32);
1474 let ret
= LowerHex
::fmt(&(*self as *const () as usize), f
);
1476 f
.width
= old_width
;
1477 f
.flags
= old_flags
;
1483 #[stable(feature = "rust1", since = "1.0.0")]
1484 impl<T
: ?Sized
> Pointer
for *mut T
{
1485 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1486 Pointer
::fmt(&(*self as *const T
), f
)
1490 #[stable(feature = "rust1", since = "1.0.0")]
1491 impl<'a
, T
: ?Sized
> Pointer
for &'a T
{
1492 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1493 Pointer
::fmt(&(*self as *const T
), f
)
1497 #[stable(feature = "rust1", since = "1.0.0")]
1498 impl<'a
, T
: ?Sized
> Pointer
for &'a
mut T
{
1499 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1500 Pointer
::fmt(&(&**self as *const T
), f
)
1504 // Common code of floating point Debug and Display.
1505 fn float_to_decimal_common
<T
>(fmt
: &mut Formatter
, num
: &T
, negative_zero
: bool
) -> Result
1506 where T
: flt2dec
::DecodableFloat
1508 let force_sign
= fmt
.sign_plus();
1509 let sign
= match (force_sign
, negative_zero
) {
1510 (false, false) => flt2dec
::Sign
::Minus
,
1511 (false, true) => flt2dec
::Sign
::MinusRaw
,
1512 (true, false) => flt2dec
::Sign
::MinusPlus
,
1513 (true, true) => flt2dec
::Sign
::MinusPlusRaw
,
1516 let mut buf
= [0; 1024]; // enough for f32 and f64
1517 let mut parts
= [flt2dec
::Part
::Zero(0); 16];
1518 let formatted
= if let Some(precision
) = fmt
.precision
{
1519 flt2dec
::to_exact_fixed_str(flt2dec
::strategy
::grisu
::format_exact
, *num
, sign
,
1520 precision
, false, &mut buf
, &mut parts
)
1522 flt2dec
::to_shortest_str(flt2dec
::strategy
::grisu
::format_shortest
, *num
, sign
,
1523 0, false, &mut buf
, &mut parts
)
1525 fmt
.pad_formatted_parts(&formatted
)
1528 // Common code of floating point LowerExp and UpperExp.
1529 fn float_to_exponential_common
<T
>(fmt
: &mut Formatter
, num
: &T
, upper
: bool
) -> Result
1530 where T
: flt2dec
::DecodableFloat
1532 let force_sign
= fmt
.sign_plus();
1533 let sign
= match force_sign
{
1534 false => flt2dec
::Sign
::Minus
,
1535 true => flt2dec
::Sign
::MinusPlus
,
1538 let mut buf
= [0; 1024]; // enough for f32 and f64
1539 let mut parts
= [flt2dec
::Part
::Zero(0); 16];
1540 let formatted
= if let Some(precision
) = fmt
.precision
{
1541 // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
1542 flt2dec
::to_exact_exp_str(flt2dec
::strategy
::grisu
::format_exact
, *num
, sign
,
1543 precision
+ 1, upper
, &mut buf
, &mut parts
)
1545 flt2dec
::to_shortest_exp_str(flt2dec
::strategy
::grisu
::format_shortest
, *num
, sign
,
1546 (0, 0), upper
, &mut buf
, &mut parts
)
1548 fmt
.pad_formatted_parts(&formatted
)
1551 macro_rules
! floating
{ ($ty
:ident
) => {
1553 #[stable(feature = "rust1", since = "1.0.0")]
1554 impl Debug
for $ty
{
1555 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1556 float_to_decimal_common(fmt
, self, true)
1560 #[stable(feature = "rust1", since = "1.0.0")]
1561 impl Display
for $ty
{
1562 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1563 float_to_decimal_common(fmt
, self, false)
1567 #[stable(feature = "rust1", since = "1.0.0")]
1568 impl LowerExp
for $ty
{
1569 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1570 float_to_exponential_common(fmt
, self, false)
1574 #[stable(feature = "rust1", since = "1.0.0")]
1575 impl UpperExp
for $ty
{
1576 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1577 float_to_exponential_common(fmt
, self, true)
1584 // Implementation of Display/Debug for various core types
1586 #[stable(feature = "rust1", since = "1.0.0")]
1587 impl<T
> Debug
for *const T
{
1588 fn fmt(&self, f
: &mut Formatter
) -> Result { Pointer::fmt(self, f) }
1590 #[stable(feature = "rust1", since = "1.0.0")]
1591 impl<T
> Debug
for *mut T
{
1592 fn fmt(&self, f
: &mut Formatter
) -> Result { Pointer::fmt(self, f) }
1596 ($name
:ident
, $
($other
:ident
,)*) => (tuple
! { $($other,)* }
)
1599 macro_rules
! tuple
{
1601 ( $
($name
:ident
,)+ ) => (
1602 #[stable(feature = "rust1", since = "1.0.0")]
1603 impl<$
($name
:Debug
),*> Debug
for ($
($name
,)*) {
1604 #[allow(non_snake_case, unused_assignments, deprecated)]
1605 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1606 let mut builder
= f
.debug_tuple("");
1607 let ($
(ref $name
,)*) = *self;
1609 builder
.field($name
);
1615 peel
! { $($name,)* }
1619 tuple
! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
1621 #[stable(feature = "rust1", since = "1.0.0")]
1622 impl<T
: Debug
> Debug
for [T
] {
1623 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1624 f
.debug_list().entries(self.iter()).finish()
1628 #[stable(feature = "rust1", since = "1.0.0")]
1630 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1634 #[stable(feature = "rust1", since = "1.0.0")]
1635 impl<T
: ?Sized
> Debug
for PhantomData
<T
> {
1636 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1637 f
.pad("PhantomData")
1641 #[stable(feature = "rust1", since = "1.0.0")]
1642 impl<T
: Copy
+ Debug
> Debug
for Cell
<T
> {
1643 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1644 f
.debug_struct("Cell")
1645 .field("value", &self.get())
1650 #[stable(feature = "rust1", since = "1.0.0")]
1651 impl<T
: ?Sized
+ Debug
> Debug
for RefCell
<T
> {
1652 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1653 match self.borrow_state() {
1654 BorrowState
::Unused
| BorrowState
::Reading
=> {
1655 f
.debug_struct("RefCell")
1656 .field("value", &self.borrow())
1659 BorrowState
::Writing
=> {
1660 f
.debug_struct("RefCell")
1661 .field("value", &"<borrowed>")
1668 #[stable(feature = "rust1", since = "1.0.0")]
1669 impl<'b
, T
: ?Sized
+ Debug
> Debug
for Ref
<'b
, T
> {
1670 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1671 Debug
::fmt(&**self, f
)
1675 #[stable(feature = "rust1", since = "1.0.0")]
1676 impl<'b
, T
: ?Sized
+ Debug
> Debug
for RefMut
<'b
, T
> {
1677 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1678 Debug
::fmt(&*(self.deref()), f
)
1682 #[stable(feature = "core_impl_debug", since = "1.9.0")]
1683 impl<T
: ?Sized
+ Debug
> Debug
for UnsafeCell
<T
> {
1684 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1689 // If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
1690 // it's a lot easier than creating all of the rt::Piece structures here.