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
::{Cell, RefCell, Ref, RefMut, BorrowState}
;
18 use marker
::PhantomData
;
25 use self::rt
::v1
::Alignment
;
27 pub use self::num
::radix
;
28 pub use self::num
::Radix
;
29 pub use self::num
::RadixFmt
;
31 pub use self::builders
::{DebugStruct, DebugTuple, DebugSet, DebugList, DebugMap}
;
36 #[unstable(feature = "core", reason = "internal to format_args!")]
42 #[stable(feature = "rust1", since = "1.0.0")]
43 /// The type returned by formatter methods.
44 pub type Result
= result
::Result
<(), Error
>;
46 /// The error type which is returned from formatting a message into a stream.
48 /// This type does not support transmission of an error other than that an error
49 /// occurred. Any extra information must be arranged to be transmitted through
51 #[stable(feature = "rust1", since = "1.0.0")]
52 #[derive(Copy, Clone, Debug)]
55 /// A collection of methods that are required to format a message into a stream.
57 /// This trait is the type which this modules requires when formatting
58 /// information. This is similar to the standard library's `io::Write` trait,
59 /// but it is only intended for use in libcore.
61 /// This trait should generally not be implemented by consumers of the standard
62 /// library. The `write!` macro accepts an instance of `io::Write`, and the
63 /// `io::Write` trait is favored over implementing this trait.
64 #[stable(feature = "rust1", since = "1.0.0")]
66 /// Writes a slice of bytes into this writer, returning whether the write
69 /// This method can only succeed if the entire byte slice was successfully
70 /// written, and this method will not return until all data has been
71 /// written or an error occurs.
75 /// This function will return an instance of `FormatError` on error.
76 #[stable(feature = "rust1", since = "1.0.0")]
77 fn write_str(&mut self, s
: &str) -> Result
;
79 /// Writes a `char` into this writer, returning whether the write succeeded.
81 /// A single `char` may be encoded as more than one byte.
82 /// This method can only succeed if the entire byte sequence was successfully
83 /// written, and this method will not return until all data has been
84 /// written or an error occurs.
88 /// This function will return an instance of `FormatError` on error.
89 #[stable(feature = "fmt_write_char", since = "1.1.0")]
90 fn write_char(&mut self, c
: char) -> Result
{
91 let mut utf_8
= [0u8; 4];
92 let bytes_written
= c
.encode_utf8(&mut utf_8
).unwrap_or(0);
93 self.write_str(unsafe { mem::transmute(&utf_8[..bytes_written]) }
)
96 /// Glue for usage of the `write!` macro with implementers of this trait.
98 /// This method should generally not be invoked manually, but rather through
99 /// the `write!` macro itself.
100 #[stable(feature = "rust1", since = "1.0.0")]
101 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
102 // This Adapter is needed to allow `self` (of type `&mut
103 // Self`) to be cast to a Write (below) without
104 // requiring a `Sized` bound.
105 struct Adapter
<'a
,T
: ?Sized
+'a
>(&'a
mut T
);
107 impl<'a
, T
: ?Sized
> Write
for Adapter
<'a
, T
>
110 fn write_str(&mut self, s
: &str) -> Result
{
114 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
115 self.0.write_fmt(args
)
119 write(&mut Adapter(self), args
)
123 /// A struct to represent both where to emit formatting strings to and how they
124 /// should be formatted. A mutable version of this is passed to all formatting
126 #[stable(feature = "rust1", since = "1.0.0")]
127 pub struct Formatter
<'a
> {
130 align
: rt
::v1
::Alignment
,
131 width
: Option
<usize>,
132 precision
: Option
<usize>,
134 buf
: &'a
mut (Write
+'a
),
135 curarg
: slice
::Iter
<'a
, ArgumentV1
<'a
>>,
136 args
: &'a
[ArgumentV1
<'a
>],
139 // NB. Argument is essentially an optimized partially applied formatting function,
140 // equivalent to `exists T.(&T, fn(&T, &mut Formatter) -> Result`.
144 /// This struct represents the generic "argument" which is taken by the Xprintf
145 /// family of functions. It contains a function to format the given value. At
146 /// compile time it is ensured that the function and the value have the correct
147 /// types, and then this struct is used to canonicalize arguments to one type.
149 #[unstable(feature = "core", reason = "internal to format_args!")]
151 pub struct ArgumentV1
<'a
> {
153 formatter
: fn(&Void
, &mut Formatter
) -> Result
,
156 impl<'a
> Clone
for ArgumentV1
<'a
> {
157 fn clone(&self) -> ArgumentV1
<'a
> {
162 impl<'a
> ArgumentV1
<'a
> {
164 fn show_usize(x
: &usize, f
: &mut Formatter
) -> Result
{
169 #[unstable(feature = "core", reason = "internal to format_args!")]
170 pub fn new
<'b
, T
>(x
: &'b T
,
171 f
: fn(&T
, &mut Formatter
) -> Result
) -> ArgumentV1
<'b
> {
174 formatter
: mem
::transmute(f
),
175 value
: mem
::transmute(x
)
181 #[unstable(feature = "core", reason = "internal to format_args!")]
182 pub fn from_usize(x
: &usize) -> ArgumentV1
{
183 ArgumentV1
::new(x
, ArgumentV1
::show_usize
)
186 fn as_usize(&self) -> Option
<usize> {
187 if self.formatter
as usize == ArgumentV1
::show_usize
as usize {
188 Some(unsafe { *(self.value as *const _ as *const usize) }
)
195 // flags available in the v1 format of format_args
196 #[derive(Copy, Clone)]
197 #[allow(dead_code)] // SignMinus isn't currently used
198 enum FlagV1 { SignPlus, SignMinus, Alternate, SignAwareZeroPad, }
200 impl<'a
> Arguments
<'a
> {
201 /// When using the format_args!() macro, this function is used to generate the
202 /// Arguments structure.
203 #[doc(hidden)] #[inline]
204 #[unstable(feature = "core", reason = "internal to format_args!")]
205 pub fn new_v1(pieces
: &'a
[&'a
str],
206 args
: &'a
[ArgumentV1
<'a
>]) -> Arguments
<'a
> {
214 /// This function is used to specify nonstandard formatting parameters.
215 /// The `pieces` array must be at least as long as `fmt` to construct
216 /// a valid Arguments structure. Also, any `Count` within `fmt` that is
217 /// `CountIsParam` or `CountIsNextParam` has to point to an argument
218 /// created with `argumentusize`. However, failing to do so doesn't cause
219 /// unsafety, but will ignore invalid .
220 #[doc(hidden)] #[inline]
221 #[unstable(feature = "core", reason = "internal to format_args!")]
222 pub fn new_v1_formatted(pieces
: &'a
[&'a
str],
223 args
: &'a
[ArgumentV1
<'a
>],
224 fmt
: &'a
[rt
::v1
::Argument
]) -> Arguments
<'a
> {
233 /// This structure represents a safely precompiled version of a format string
234 /// and its arguments. This cannot be generated at runtime because it cannot
235 /// safely be done so, so no constructors are given and the fields are private
236 /// to prevent modification.
238 /// The `format_args!` macro will safely create an instance of this structure
239 /// and pass it to a function or closure, passed as the first argument. The
240 /// macro validates the format string at compile-time so usage of the `write`
241 /// and `format` functions can be safely performed.
242 #[stable(feature = "rust1", since = "1.0.0")]
243 #[derive(Copy, Clone)]
244 pub struct Arguments
<'a
> {
245 // Format string pieces to print.
246 pieces
: &'a
[&'a
str],
248 // Placeholder specs, or `None` if all specs are default (as in "{}{}").
249 fmt
: Option
<&'a
[rt
::v1
::Argument
]>,
251 // Dynamic arguments for interpolation, to be interleaved with string
252 // pieces. (Every argument is preceded by a string piece.)
253 args
: &'a
[ArgumentV1
<'a
>],
256 #[stable(feature = "rust1", since = "1.0.0")]
257 impl<'a
> Debug
for Arguments
<'a
> {
258 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
259 Display
::fmt(self, fmt
)
263 #[stable(feature = "rust1", since = "1.0.0")]
264 impl<'a
> Display
for Arguments
<'a
> {
265 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
266 write(fmt
.buf
, *self)
270 /// Format trait for the `:?` format. Useful for debugging, all types
271 /// should implement this.
272 #[stable(feature = "rust1", since = "1.0.0")]
273 #[rustc_on_unimplemented = "`{Self}` cannot be formatted using `:?`; if it is \
274 defined in your crate, add `#[derive(Debug)]` or \
275 manually implement it"]
276 #[lang = "debug_trait"]
278 /// Formats the value using the given formatter.
279 #[stable(feature = "rust1", since = "1.0.0")]
280 fn fmt(&self, &mut Formatter
) -> Result
;
283 /// When a value can be semantically expressed as a String, this trait may be
284 /// used. It corresponds to the default format, `{}`.
285 #[rustc_on_unimplemented = "`{Self}` cannot be formatted with the default \
286 formatter; try using `:?` instead if you are using \
288 #[stable(feature = "rust1", since = "1.0.0")]
290 /// Formats the value using the given formatter.
291 #[stable(feature = "rust1", since = "1.0.0")]
292 fn fmt(&self, &mut Formatter
) -> Result
;
295 /// Format trait for the `o` character
296 #[stable(feature = "rust1", since = "1.0.0")]
298 /// Formats the value using the given formatter.
299 #[stable(feature = "rust1", since = "1.0.0")]
300 fn fmt(&self, &mut Formatter
) -> Result
;
303 /// Format trait for the `b` character
304 #[stable(feature = "rust1", since = "1.0.0")]
306 /// Formats the value using the given formatter.
307 #[stable(feature = "rust1", since = "1.0.0")]
308 fn fmt(&self, &mut Formatter
) -> Result
;
311 /// Format trait for the `x` character
312 #[stable(feature = "rust1", since = "1.0.0")]
314 /// Formats the value using the given formatter.
315 #[stable(feature = "rust1", since = "1.0.0")]
316 fn fmt(&self, &mut Formatter
) -> Result
;
319 /// Format trait for the `X` character
320 #[stable(feature = "rust1", since = "1.0.0")]
322 /// Formats the value using the given formatter.
323 #[stable(feature = "rust1", since = "1.0.0")]
324 fn fmt(&self, &mut Formatter
) -> Result
;
327 /// Format trait for the `p` character
328 #[stable(feature = "rust1", since = "1.0.0")]
330 /// Formats the value using the given formatter.
331 #[stable(feature = "rust1", since = "1.0.0")]
332 fn fmt(&self, &mut Formatter
) -> Result
;
335 /// Format trait for the `e` character
336 #[stable(feature = "rust1", since = "1.0.0")]
338 /// Formats the value using the given formatter.
339 #[stable(feature = "rust1", since = "1.0.0")]
340 fn fmt(&self, &mut Formatter
) -> Result
;
343 /// Format trait for the `E` character
344 #[stable(feature = "rust1", since = "1.0.0")]
346 /// Formats the value using the given formatter.
347 #[stable(feature = "rust1", since = "1.0.0")]
348 fn fmt(&self, &mut Formatter
) -> Result
;
351 /// The `write` function takes an output stream, a precompiled format string,
352 /// and a list of arguments. The arguments will be formatted according to the
353 /// specified format string into the output stream provided.
357 /// * output - the buffer to write output to
358 /// * args - the precompiled arguments generated by `format_args!`
359 #[stable(feature = "rust1", since = "1.0.0")]
360 pub fn write(output
: &mut Write
, args
: Arguments
) -> Result
{
361 let mut formatter
= Formatter
{
366 align
: Alignment
::Unknown
,
369 curarg
: args
.args
.iter(),
372 let mut pieces
= args
.pieces
.iter();
376 // We can use default formatting parameters for all arguments.
377 for (arg
, piece
) in args
.args
.iter().zip(pieces
.by_ref()) {
378 try
!(formatter
.buf
.write_str(*piece
));
379 try
!((arg
.formatter
)(arg
.value
, &mut formatter
));
383 // Every spec has a corresponding argument that is preceded by
385 for (arg
, piece
) in fmt
.iter().zip(pieces
.by_ref()) {
386 try
!(formatter
.buf
.write_str(*piece
));
387 try
!(formatter
.run(arg
));
392 // There can be only one trailing string piece left.
393 match pieces
.next() {
395 try
!(formatter
.buf
.write_str(*piece
));
403 impl<'a
> Formatter
<'a
> {
405 // First up is the collection of functions used to execute a format string
406 // at runtime. This consumes all of the compile-time statics generated by
407 // the format! syntax extension.
408 fn run(&mut self, arg
: &rt
::v1
::Argument
) -> Result
{
409 // Fill in the format parameters into the formatter
410 self.fill
= arg
.format
.fill
;
411 self.align
= arg
.format
.align
;
412 self.flags
= arg
.format
.flags
;
413 self.width
= self.getcount(&arg
.format
.width
);
414 self.precision
= self.getcount(&arg
.format
.precision
);
416 // Extract the correct argument
417 let value
= match arg
.position
{
418 rt
::v1
::Position
::Next
=> { *self.curarg.next().unwrap() }
419 rt
::v1
::Position
::At(i
) => self.args
[i
],
422 // Then actually do some printing
423 (value
.formatter
)(value
.value
, self)
426 fn getcount(&mut self, cnt
: &rt
::v1
::Count
) -> Option
<usize> {
428 rt
::v1
::Count
::Is(n
) => Some(n
),
429 rt
::v1
::Count
::Implied
=> None
,
430 rt
::v1
::Count
::Param(i
) => {
431 self.args
[i
].as_usize()
433 rt
::v1
::Count
::NextParam
=> {
434 self.curarg
.next().and_then(|arg
| arg
.as_usize())
439 // Helper methods used for padding and processing formatting arguments that
440 // all formatting traits can use.
442 /// Performs the correct padding for an integer which has already been
443 /// emitted into a str. The str should *not* contain the sign for the
444 /// integer, that will be added by this method.
448 /// * is_positive - whether the original integer was positive or not.
449 /// * prefix - if the '#' character (Alternate) is provided, this
450 /// is the prefix to put in front of the number.
451 /// * buf - the byte array that the number has been formatted into
453 /// This function will correctly account for the flags provided as well as
454 /// the minimum width. It will not take precision into account.
455 #[stable(feature = "rust1", since = "1.0.0")]
456 pub fn pad_integral(&mut self,
463 let mut width
= buf
.len();
467 sign
= Some('
-'
); width
+= 1;
468 } else if self.flags
& (1 << (FlagV1
::SignPlus
as u32)) != 0 {
469 sign
= Some('
+'
); width
+= 1;
472 let mut prefixed
= false;
473 if self.flags
& (1 << (FlagV1
::Alternate
as u32)) != 0 {
474 prefixed
= true; width
+= prefix
.char_len();
477 // Writes the sign if it exists, and then the prefix if it was requested
478 let write_prefix
= |f
: &mut Formatter
| {
479 if let Some(c
) = sign
{
481 let n
= c
.encode_utf8(&mut b
).unwrap_or(0);
482 let b
= unsafe { str::from_utf8_unchecked(&b[..n]) }
;
483 try
!(f
.buf
.write_str(b
));
485 if prefixed { f.buf.write_str(prefix) }
489 // The `width` field is more of a `min-width` parameter at this point.
491 // If there's no minimum length requirements then we can just
494 try
!(write_prefix(self)); self.buf
.write_str(buf
)
496 // Check if we're over the minimum width, if so then we can also
497 // just write the bytes.
498 Some(min
) if width
>= min
=> {
499 try
!(write_prefix(self)); self.buf
.write_str(buf
)
501 // The sign and prefix goes before the padding if the fill character
503 Some(min
) if self.flags
& (1 << (FlagV1
::SignAwareZeroPad
as u32)) != 0 => {
505 try
!(write_prefix(self));
506 self.with_padding(min
- width
, Alignment
::Right
, |f
| {
510 // Otherwise, the sign and prefix goes after the padding
512 self.with_padding(min
- width
, Alignment
::Right
, |f
| {
513 try
!(write_prefix(f
)); f
.buf
.write_str(buf
)
519 /// This function takes a string slice and emits it to the internal buffer
520 /// after applying the relevant formatting flags specified. The flags
521 /// recognized for generic strings are:
523 /// * width - the minimum width of what to emit
524 /// * fill/align - what to emit and where to emit it if the string
525 /// provided needs to be padded
526 /// * precision - the maximum length to emit, the string is truncated if it
527 /// is longer than this length
529 /// Notably this function ignored the `flag` parameters
530 #[stable(feature = "rust1", since = "1.0.0")]
531 pub fn pad(&mut self, s
: &str) -> Result
{
532 // Make sure there's a fast path up front
533 if self.width
.is_none() && self.precision
.is_none() {
534 return self.buf
.write_str(s
);
536 // The `precision` field can be interpreted as a `max-width` for the
537 // string being formatted
538 match self.precision
{
540 // If there's a maximum width and our string is longer than
541 // that, then we must always have truncation. This is the only
542 // case where the maximum length will matter.
543 let char_len
= s
.char_len();
545 let nchars
= ::cmp
::min(max
, char_len
);
546 return self.buf
.write_str(s
.slice_chars(0, nchars
));
551 // The `width` field is more of a `min-width` parameter at this point.
553 // If we're under the maximum length, and there's no minimum length
554 // requirements, then we can just emit the string
555 None
=> self.buf
.write_str(s
),
556 // If we're under the maximum width, check if we're over the minimum
557 // width, if so it's as easy as just emitting the string.
558 Some(width
) if s
.char_len() >= width
=> {
559 self.buf
.write_str(s
)
561 // If we're under both the maximum and the minimum width, then fill
562 // up the minimum width with the specified string + some alignment.
564 self.with_padding(width
- s
.char_len(), Alignment
::Left
, |me
| {
571 /// Runs a callback, emitting the correct padding either before or
572 /// afterwards depending on whether right or left alignment is requested.
573 fn with_padding
<F
>(&mut self, padding
: usize, default: Alignment
,
575 where F
: FnOnce(&mut Formatter
) -> Result
,
578 let align
= match self.align
{
579 Alignment
::Unknown
=> default,
583 let (pre_pad
, post_pad
) = match align
{
584 Alignment
::Left
=> (0, padding
),
585 Alignment
::Right
| Alignment
::Unknown
=> (padding
, 0),
586 Alignment
::Center
=> (padding
/ 2, (padding
+ 1) / 2),
589 let mut fill
= [0; 4];
590 let len
= self.fill
.encode_utf8(&mut fill
).unwrap_or(0);
591 let fill
= unsafe { str::from_utf8_unchecked(&fill[..len]) }
;
593 for _
in 0..pre_pad
{
594 try
!(self.buf
.write_str(fill
));
599 for _
in 0..post_pad
{
600 try
!(self.buf
.write_str(fill
));
606 /// Takes the formatted parts and applies the padding.
607 /// Assumes that the caller already has rendered the parts with required precision,
608 /// so that `self.precision` can be ignored.
609 fn pad_formatted_parts(&mut self, formatted
: &flt2dec
::Formatted
) -> Result
{
610 if let Some(mut width
) = self.width
{
611 // for the sign-aware zero padding, we render the sign first and
612 // behave as if we had no sign from the beginning.
613 let mut formatted
= formatted
.clone();
614 let mut align
= self.align
;
615 let old_fill
= self.fill
;
616 if self.flags
& (1 << (FlagV1
::SignAwareZeroPad
as u32)) != 0 {
617 // a sign always goes first
618 let sign
= unsafe { str::from_utf8_unchecked(formatted.sign) }
;
619 try
!(self.buf
.write_str(sign
));
621 // remove the sign from the formatted parts
622 formatted
.sign
= b
"";
623 width
= if width
< sign
.len() { 0 }
else { width - sign.len() }
;
624 align
= Alignment
::Right
;
628 // remaining parts go through the ordinary padding process.
629 let len
= formatted
.len();
630 let ret
= if width
<= len
{ // no padding
631 self.write_formatted_parts(&formatted
)
633 self.with_padding(width
- len
, align
, |f
| {
634 f
.write_formatted_parts(&formatted
)
637 self.fill
= old_fill
;
640 // this is the common case and we take a shortcut
641 self.write_formatted_parts(formatted
)
645 fn write_formatted_parts(&mut self, formatted
: &flt2dec
::Formatted
) -> Result
{
646 fn write_bytes(buf
: &mut Write
, s
: &[u8]) -> Result
{
647 buf
.write_str(unsafe { str::from_utf8_unchecked(s) }
)
650 if !formatted
.sign
.is_empty() {
651 try
!(write_bytes(self.buf
, formatted
.sign
));
653 for part
in formatted
.parts
{
655 flt2dec
::Part
::Zero(mut nzeroes
) => {
656 const ZEROES
: &'
static str = // 64 zeroes
657 "0000000000000000000000000000000000000000000000000000000000000000";
658 while nzeroes
> ZEROES
.len() {
659 try
!(self.buf
.write_str(ZEROES
));
660 nzeroes
-= ZEROES
.len();
663 try
!(self.buf
.write_str(&ZEROES
[..nzeroes
]));
666 flt2dec
::Part
::Num(mut v
) => {
668 let len
= part
.len();
669 for c
in s
[..len
].iter_mut().rev() {
670 *c
= b'
0'
+ (v
% 10) as u8;
673 try
!(write_bytes(self.buf
, &s
[..len
]));
675 flt2dec
::Part
::Copy(buf
) => {
676 try
!(write_bytes(self.buf
, buf
));
683 /// Writes some data to the underlying buffer contained within this
685 #[stable(feature = "rust1", since = "1.0.0")]
686 pub fn write_str(&mut self, data
: &str) -> Result
{
687 self.buf
.write_str(data
)
690 /// Writes some formatted information into this instance
691 #[stable(feature = "rust1", since = "1.0.0")]
692 pub fn write_fmt(&mut self, fmt
: Arguments
) -> Result
{
696 /// Flags for formatting (packed version of rt::Flag)
697 #[stable(feature = "rust1", since = "1.0.0")]
698 pub fn flags(&self) -> u32 { self.flags }
700 /// Character used as 'fill' whenever there is alignment
701 #[unstable(feature = "core", reason = "method was just created")]
702 pub fn fill(&self) -> char { self.fill }
704 /// Flag indicating what form of alignment was requested
705 #[unstable(feature = "core", reason = "method was just created")]
706 pub fn align(&self) -> Alignment { self.align }
708 /// Optionally specified integer width that the output should be
709 #[unstable(feature = "core", reason = "method was just created")]
710 pub fn width(&self) -> Option
<usize> { self.width }
712 /// Optionally specified precision for numeric types
713 #[unstable(feature = "core", reason = "method was just created")]
714 pub fn precision(&self) -> Option
<usize> { self.precision }
716 /// Creates a `DebugStruct` builder designed to assist with creation of
717 /// `fmt::Debug` implementations for structs.
722 /// # #![feature(debug_builders, core)]
730 /// impl fmt::Debug for Foo {
731 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
732 /// fmt.debug_struct("Foo")
733 /// .field("bar", &self.bar)
734 /// .field("baz", &self.baz)
739 /// // prints "Foo { bar: 10, baz: "Hello World" }"
740 /// println!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() });
742 #[unstable(feature = "debug_builders", reason = "method was just created")]
744 pub fn debug_struct
<'b
>(&'b
mut self, name
: &str) -> DebugStruct
<'b
, 'a
> {
745 builders
::debug_struct_new(self, name
)
748 /// Creates a `DebugTuple` builder designed to assist with creation of
749 /// `fmt::Debug` implementations for tuple structs.
754 /// # #![feature(debug_builders, core)]
757 /// struct Foo(i32, String);
759 /// impl fmt::Debug for Foo {
760 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
761 /// fmt.debug_tuple("Foo")
768 /// // prints "Foo(10, "Hello World")"
769 /// println!("{:?}", Foo(10, "Hello World".to_string()));
771 #[unstable(feature = "debug_builders", reason = "method was just created")]
773 pub fn debug_tuple
<'b
>(&'b
mut self, name
: &str) -> DebugTuple
<'b
, 'a
> {
774 builders
::debug_tuple_new(self, name
)
777 /// Creates a `DebugList` builder designed to assist with creation of
778 /// `fmt::Debug` implementations for list-like structures.
783 /// # #![feature(debug_builders, core)]
786 /// struct Foo(Vec<i32>);
788 /// impl fmt::Debug for Foo {
789 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
790 /// self.0.iter().fold(fmt.debug_list(), |b, e| b.entry(e)).finish()
794 /// // prints "[10, 11]"
795 /// println!("{:?}", Foo(vec![10, 11]));
797 #[unstable(feature = "debug_builders", reason = "method was just created")]
799 pub fn debug_list
<'b
>(&'b
mut self) -> DebugList
<'b
, 'a
> {
800 builders
::debug_list_new(self)
803 /// Creates a `DebugSet` builder designed to assist with creation of
804 /// `fmt::Debug` implementations for set-like structures.
809 /// # #![feature(debug_builders, core)]
812 /// struct Foo(Vec<i32>);
814 /// impl fmt::Debug for Foo {
815 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
816 /// self.0.iter().fold(fmt.debug_set(), |b, e| b.entry(e)).finish()
820 /// // prints "{10, 11}"
821 /// println!("{:?}", Foo(vec![10, 11]));
823 #[unstable(feature = "debug_builders", reason = "method was just created")]
825 pub fn debug_set
<'b
>(&'b
mut self) -> DebugSet
<'b
, 'a
> {
826 builders
::debug_set_new(self)
829 /// Creates a `DebugMap` builder designed to assist with creation of
830 /// `fmt::Debug` implementations for map-like structures.
835 /// # #![feature(debug_builders, core)]
838 /// struct Foo(Vec<(String, i32)>);
840 /// impl fmt::Debug for Foo {
841 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
842 /// self.0.iter().fold(fmt.debug_map(), |b, &(ref k, ref v)| b.entry(k, v)).finish()
846 /// // prints "{"A": 10, "B": 11}"
847 /// println!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)]));
849 #[unstable(feature = "debug_builders", reason = "method was just created")]
851 pub fn debug_map
<'b
>(&'b
mut self) -> DebugMap
<'b
, 'a
> {
852 builders
::debug_map_new(self)
856 #[stable(feature = "rust1", since = "1.0.0")]
857 impl Display
for Error
{
858 fn fmt(&self, f
: &mut Formatter
) -> Result
{
859 Display
::fmt("an error occurred when formatting an argument", f
)
863 // Implementations of the core formatting traits
865 macro_rules
! fmt_refs
{
866 ($
($tr
:ident
),*) => {
868 #[stable(feature = "rust1", since = "1.0.0")]
869 impl<'a
, T
: ?Sized
+ $tr
> $tr
for &'a T
{
870 fn fmt(&self, f
: &mut Formatter
) -> Result { $tr::fmt(&**self, f) }
872 #[stable(feature = "rust1", since = "1.0.0")]
873 impl<'a
, T
: ?Sized
+ $tr
> $tr
for &'a
mut T
{
874 fn fmt(&self, f
: &mut Formatter
) -> Result { $tr::fmt(&**self, f) }
880 fmt_refs
! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperExp }
882 #[stable(feature = "rust1", since = "1.0.0")]
883 impl Debug
for bool
{
884 fn fmt(&self, f
: &mut Formatter
) -> Result
{
885 Display
::fmt(self, f
)
889 #[stable(feature = "rust1", since = "1.0.0")]
890 impl Display
for bool
{
891 fn fmt(&self, f
: &mut Formatter
) -> Result
{
892 Display
::fmt(if *self { "true" }
else { "false" }
, f
)
896 #[stable(feature = "rust1", since = "1.0.0")]
898 fn fmt(&self, f
: &mut Formatter
) -> Result
{
899 try
!(write
!(f
, "\""));
900 for c
in self.chars().flat_map(|c
| c
.escape_default()) {
901 try
!(write
!(f
, "{}", c
));
907 #[stable(feature = "rust1", since = "1.0.0")]
908 impl Display
for str {
909 fn fmt(&self, f
: &mut Formatter
) -> Result
{
914 #[stable(feature = "rust1", since = "1.0.0")]
915 impl Debug
for char {
916 fn fmt(&self, f
: &mut Formatter
) -> Result
{
918 try
!(write
!(f
, "'"));
919 for c
in self.escape_default() {
920 try
!(write
!(f
, "{}", c
));
926 #[stable(feature = "rust1", since = "1.0.0")]
927 impl Display
for char {
928 fn fmt(&self, f
: &mut Formatter
) -> Result
{
929 let mut utf8
= [0; 4];
930 let amt
= self.encode_utf8(&mut utf8
).unwrap_or(0);
931 let s
: &str = unsafe { mem::transmute(&utf8[..amt]) }
;
936 #[stable(feature = "rust1", since = "1.0.0")]
937 impl<T
> Pointer
for *const T
{
938 fn fmt(&self, f
: &mut Formatter
) -> Result
{
939 let old_width
= f
.width
;
940 let old_flags
= f
.flags
;
942 // The alternate flag is already treated by LowerHex as being special-
943 // it denotes whether to prefix with 0x. We use it to work out whether
944 // or not to zero extend, and then unconditionally set it to get the
946 if f
.flags
& 1 << (FlagV1
::Alternate
as u32) > 0 {
947 f
.flags
|= 1 << (FlagV1
::SignAwareZeroPad
as u32);
949 if let None
= f
.width
{
950 // The formats need two extra bytes, for the 0x
951 if cfg
!(target_pointer_width
= "32") {
958 f
.flags
|= 1 << (FlagV1
::Alternate
as u32);
960 let ret
= LowerHex
::fmt(&(*self as usize), f
);
969 #[stable(feature = "rust1", since = "1.0.0")]
970 impl<T
> Pointer
for *mut T
{
971 fn fmt(&self, f
: &mut Formatter
) -> Result
{
972 // FIXME(#23542) Replace with type ascription.
973 #![allow(trivial_casts)]
974 Pointer
::fmt(&(*self as *const T
), f
)
978 #[stable(feature = "rust1", since = "1.0.0")]
979 impl<'a
, T
> Pointer
for &'a T
{
980 fn fmt(&self, f
: &mut Formatter
) -> Result
{
981 // FIXME(#23542) Replace with type ascription.
982 #![allow(trivial_casts)]
983 Pointer
::fmt(&(*self as *const T
), f
)
987 #[stable(feature = "rust1", since = "1.0.0")]
988 impl<'a
, T
> Pointer
for &'a
mut T
{
989 fn fmt(&self, f
: &mut Formatter
) -> Result
{
990 // FIXME(#23542) Replace with type ascription.
991 #![allow(trivial_casts)]
992 Pointer
::fmt(&(&**self as *const T
), f
)
996 // Common code of floating point Debug and Display.
997 fn float_to_decimal_common
<T
>(fmt
: &mut Formatter
, num
: &T
, negative_zero
: bool
) -> Result
998 where T
: flt2dec
::DecodableFloat
1000 let force_sign
= fmt
.flags
& (1 << (FlagV1
::SignPlus
as u32)) != 0;
1001 let sign
= match (force_sign
, negative_zero
) {
1002 (false, false) => flt2dec
::Sign
::Minus
,
1003 (false, true) => flt2dec
::Sign
::MinusRaw
,
1004 (true, false) => flt2dec
::Sign
::MinusPlus
,
1005 (true, true) => flt2dec
::Sign
::MinusPlusRaw
,
1008 let mut buf
= [0; 1024]; // enough for f32 and f64
1009 let mut parts
= [flt2dec
::Part
::Zero(0); 16];
1010 let formatted
= if let Some(precision
) = fmt
.precision
{
1011 flt2dec
::to_exact_fixed_str(flt2dec
::strategy
::grisu
::format_exact
, *num
, sign
,
1012 precision
, false, &mut buf
, &mut parts
)
1014 flt2dec
::to_shortest_str(flt2dec
::strategy
::grisu
::format_shortest
, *num
, sign
,
1015 0, false, &mut buf
, &mut parts
)
1017 fmt
.pad_formatted_parts(&formatted
)
1020 // Common code of floating point LowerExp and UpperExp.
1021 fn float_to_exponential_common
<T
>(fmt
: &mut Formatter
, num
: &T
, upper
: bool
) -> Result
1022 where T
: flt2dec
::DecodableFloat
1024 let force_sign
= fmt
.flags
& (1 << (FlagV1
::SignPlus
as u32)) != 0;
1025 let sign
= match force_sign
{
1026 false => flt2dec
::Sign
::Minus
,
1027 true => flt2dec
::Sign
::MinusPlus
,
1030 let mut buf
= [0; 1024]; // enough for f32 and f64
1031 let mut parts
= [flt2dec
::Part
::Zero(0); 16];
1032 let formatted
= if let Some(precision
) = fmt
.precision
{
1033 // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
1034 flt2dec
::to_exact_exp_str(flt2dec
::strategy
::grisu
::format_exact
, *num
, sign
,
1035 precision
+ 1, upper
, &mut buf
, &mut parts
)
1037 flt2dec
::to_shortest_exp_str(flt2dec
::strategy
::grisu
::format_shortest
, *num
, sign
,
1038 (0, 0), upper
, &mut buf
, &mut parts
)
1040 fmt
.pad_formatted_parts(&formatted
)
1043 macro_rules
! floating
{ ($ty
:ident
) => {
1045 #[stable(feature = "rust1", since = "1.0.0")]
1046 impl Debug
for $ty
{
1047 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1048 float_to_decimal_common(fmt
, self, true)
1052 #[stable(feature = "rust1", since = "1.0.0")]
1053 impl Display
for $ty
{
1054 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1055 float_to_decimal_common(fmt
, self, false)
1059 #[stable(feature = "rust1", since = "1.0.0")]
1060 impl LowerExp
for $ty
{
1061 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1062 float_to_exponential_common(fmt
, self, false)
1066 #[stable(feature = "rust1", since = "1.0.0")]
1067 impl UpperExp
for $ty
{
1068 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1069 float_to_exponential_common(fmt
, self, true)
1076 // Implementation of Display/Debug for various core types
1078 #[stable(feature = "rust1", since = "1.0.0")]
1079 impl<T
> Debug
for *const T
{
1080 fn fmt(&self, f
: &mut Formatter
) -> Result { Pointer::fmt(self, f) }
1082 #[stable(feature = "rust1", since = "1.0.0")]
1083 impl<T
> Debug
for *mut T
{
1084 fn fmt(&self, f
: &mut Formatter
) -> Result { Pointer::fmt(self, f) }
1088 ($name
:ident
, $
($other
:ident
,)*) => (tuple
! { $($other,)* }
)
1091 macro_rules
! tuple
{
1093 ( $
($name
:ident
,)+ ) => (
1094 #[stable(feature = "rust1", since = "1.0.0")]
1095 impl<$
($name
:Debug
),*> Debug
for ($
($name
,)*) {
1096 #[allow(non_snake_case, unused_assignments)]
1097 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1098 try
!(write
!(f
, "("));
1099 let ($
(ref $name
,)*) = *self;
1103 try
!(write
!(f
, ", "));
1105 try
!(write
!(f
, "{:?}", *$name
));
1109 try
!(write
!(f
, ","));
1114 peel
! { $($name,)* }
1118 tuple
! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
1120 #[stable(feature = "rust1", since = "1.0.0")]
1121 impl<T
: Debug
> Debug
for [T
] {
1122 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1123 self.iter().fold(f
.debug_list(), |b
, e
| b
.entry(e
)).finish()
1127 #[stable(feature = "rust1", since = "1.0.0")]
1129 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1133 impl<T
> Debug
for PhantomData
<T
> {
1134 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1135 f
.pad("PhantomData")
1139 #[stable(feature = "rust1", since = "1.0.0")]
1140 impl<T
: Copy
+ Debug
> Debug
for Cell
<T
> {
1141 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1142 write
!(f
, "Cell {{ value: {:?} }}", self.get())
1146 #[stable(feature = "rust1", since = "1.0.0")]
1147 impl<T
: ?Sized
+ Debug
> Debug
for RefCell
<T
> {
1148 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1149 match self.borrow_state() {
1150 BorrowState
::Unused
| BorrowState
::Reading
=> {
1151 write
!(f
, "RefCell {{ value: {:?} }}", self.borrow())
1153 BorrowState
::Writing
=> write
!(f
, "RefCell {{ <borrowed> }}"),
1158 #[stable(feature = "rust1", since = "1.0.0")]
1159 impl<'b
, T
: ?Sized
+ Debug
> Debug
for Ref
<'b
, T
> {
1160 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1161 Debug
::fmt(&**self, f
)
1165 #[stable(feature = "rust1", since = "1.0.0")]
1166 impl<'b
, T
: ?Sized
+ Debug
> Debug
for RefMut
<'b
, T
> {
1167 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1168 Debug
::fmt(&*(self.deref()), f
)
1172 // If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
1173 // it's a lot easier than creating all of the rt::Piece structures here.