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 = "fmt_internals", 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 `Error` 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 `Error` 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 = "fmt_internals", 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 = "fmt_internals", 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 = "fmt_internals", 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 = "fmt_internals", 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 = "fmt_internals", 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.
273 /// Generally speaking, you should just `derive` a `Debug` implementation.
277 /// Deriving an implementation:
286 /// let origin = Point { x: 0, y: 0 };
288 /// println!("The origin is: {:?}", origin);
291 /// Manually implementing:
301 /// impl fmt::Debug for Point {
302 /// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
303 /// write!(f, "({}, {})", self.x, self.y)
307 /// let origin = Point { x: 0, y: 0 };
309 /// println!("The origin is: {:?}", origin);
312 /// There are a number of `debug_*` methods on `Formatter` to help you with manual
313 /// implementations, such as [`debug_struct`][debug_struct].
315 /// [debug_struct]: ../std/fmt/struct.Formatter.html#method.debug_struct
316 #[stable(feature = "rust1", since = "1.0.0")]
317 #[rustc_on_unimplemented = "`{Self}` cannot be formatted using `:?`; if it is \
318 defined in your crate, add `#[derive(Debug)]` or \
319 manually implement it"]
320 #[lang = "debug_trait"]
322 /// Formats the value using the given formatter.
323 #[stable(feature = "rust1", since = "1.0.0")]
324 fn fmt(&self, &mut Formatter
) -> Result
;
327 /// When a value can be semantically expressed as a String, this trait may be
328 /// used. It corresponds to the default format, `{}`.
329 #[rustc_on_unimplemented = "`{Self}` cannot be formatted with the default \
330 formatter; try using `:?` instead if you are using \
332 #[stable(feature = "rust1", since = "1.0.0")]
334 /// Formats the value using the given formatter.
335 #[stable(feature = "rust1", since = "1.0.0")]
336 fn fmt(&self, &mut Formatter
) -> Result
;
339 /// Format trait for the `o` character
340 #[stable(feature = "rust1", since = "1.0.0")]
342 /// Formats the value using the given formatter.
343 #[stable(feature = "rust1", since = "1.0.0")]
344 fn fmt(&self, &mut Formatter
) -> Result
;
347 /// Format trait for the `b` character
348 #[stable(feature = "rust1", since = "1.0.0")]
350 /// Formats the value using the given formatter.
351 #[stable(feature = "rust1", since = "1.0.0")]
352 fn fmt(&self, &mut Formatter
) -> Result
;
355 /// Format trait for the `x` character
356 #[stable(feature = "rust1", since = "1.0.0")]
358 /// Formats the value using the given formatter.
359 #[stable(feature = "rust1", since = "1.0.0")]
360 fn fmt(&self, &mut Formatter
) -> Result
;
363 /// Format trait for the `X` character
364 #[stable(feature = "rust1", since = "1.0.0")]
366 /// Formats the value using the given formatter.
367 #[stable(feature = "rust1", since = "1.0.0")]
368 fn fmt(&self, &mut Formatter
) -> Result
;
371 /// Format trait for the `p` character
372 #[stable(feature = "rust1", since = "1.0.0")]
374 /// Formats the value using the given formatter.
375 #[stable(feature = "rust1", since = "1.0.0")]
376 fn fmt(&self, &mut Formatter
) -> Result
;
379 /// Format trait for the `e` character
380 #[stable(feature = "rust1", since = "1.0.0")]
382 /// Formats the value using the given formatter.
383 #[stable(feature = "rust1", since = "1.0.0")]
384 fn fmt(&self, &mut Formatter
) -> Result
;
387 /// Format trait for the `E` character
388 #[stable(feature = "rust1", since = "1.0.0")]
390 /// Formats the value using the given formatter.
391 #[stable(feature = "rust1", since = "1.0.0")]
392 fn fmt(&self, &mut Formatter
) -> Result
;
395 /// The `write` function takes an output stream, a precompiled format string,
396 /// and a list of arguments. The arguments will be formatted according to the
397 /// specified format string into the output stream provided.
401 /// * output - the buffer to write output to
402 /// * args - the precompiled arguments generated by `format_args!`
403 #[stable(feature = "rust1", since = "1.0.0")]
404 pub fn write(output
: &mut Write
, args
: Arguments
) -> Result
{
405 let mut formatter
= Formatter
{
410 align
: Alignment
::Unknown
,
413 curarg
: args
.args
.iter(),
416 let mut pieces
= args
.pieces
.iter();
420 // We can use default formatting parameters for all arguments.
421 for (arg
, piece
) in args
.args
.iter().zip(pieces
.by_ref()) {
422 try
!(formatter
.buf
.write_str(*piece
));
423 try
!((arg
.formatter
)(arg
.value
, &mut formatter
));
427 // Every spec has a corresponding argument that is preceded by
429 for (arg
, piece
) in fmt
.iter().zip(pieces
.by_ref()) {
430 try
!(formatter
.buf
.write_str(*piece
));
431 try
!(formatter
.run(arg
));
436 // There can be only one trailing string piece left.
437 match pieces
.next() {
439 try
!(formatter
.buf
.write_str(*piece
));
447 impl<'a
> Formatter
<'a
> {
449 // First up is the collection of functions used to execute a format string
450 // at runtime. This consumes all of the compile-time statics generated by
451 // the format! syntax extension.
452 fn run(&mut self, arg
: &rt
::v1
::Argument
) -> Result
{
453 // Fill in the format parameters into the formatter
454 self.fill
= arg
.format
.fill
;
455 self.align
= arg
.format
.align
;
456 self.flags
= arg
.format
.flags
;
457 self.width
= self.getcount(&arg
.format
.width
);
458 self.precision
= self.getcount(&arg
.format
.precision
);
460 // Extract the correct argument
461 let value
= match arg
.position
{
462 rt
::v1
::Position
::Next
=> { *self.curarg.next().unwrap() }
463 rt
::v1
::Position
::At(i
) => self.args
[i
],
466 // Then actually do some printing
467 (value
.formatter
)(value
.value
, self)
470 fn getcount(&mut self, cnt
: &rt
::v1
::Count
) -> Option
<usize> {
472 rt
::v1
::Count
::Is(n
) => Some(n
),
473 rt
::v1
::Count
::Implied
=> None
,
474 rt
::v1
::Count
::Param(i
) => {
475 self.args
[i
].as_usize()
477 rt
::v1
::Count
::NextParam
=> {
478 self.curarg
.next().and_then(|arg
| arg
.as_usize())
483 // Helper methods used for padding and processing formatting arguments that
484 // all formatting traits can use.
486 /// Performs the correct padding for an integer which has already been
487 /// emitted into a str. The str should *not* contain the sign for the
488 /// integer, that will be added by this method.
492 /// * is_positive - whether the original integer was positive or not.
493 /// * prefix - if the '#' character (Alternate) is provided, this
494 /// is the prefix to put in front of the number.
495 /// * buf - the byte array that the number has been formatted into
497 /// This function will correctly account for the flags provided as well as
498 /// the minimum width. It will not take precision into account.
499 #[stable(feature = "rust1", since = "1.0.0")]
500 pub fn pad_integral(&mut self,
507 let mut width
= buf
.len();
511 sign
= Some('
-'
); width
+= 1;
512 } else if self.flags
& (1 << (FlagV1
::SignPlus
as u32)) != 0 {
513 sign
= Some('
+'
); width
+= 1;
516 let mut prefixed
= false;
517 if self.flags
& (1 << (FlagV1
::Alternate
as u32)) != 0 {
518 prefixed
= true; width
+= prefix
.char_len();
521 // Writes the sign if it exists, and then the prefix if it was requested
522 let write_prefix
= |f
: &mut Formatter
| {
523 if let Some(c
) = sign
{
525 let n
= c
.encode_utf8(&mut b
).unwrap_or(0);
526 let b
= unsafe { str::from_utf8_unchecked(&b[..n]) }
;
527 try
!(f
.buf
.write_str(b
));
529 if prefixed { f.buf.write_str(prefix) }
533 // The `width` field is more of a `min-width` parameter at this point.
535 // If there's no minimum length requirements then we can just
538 try
!(write_prefix(self)); self.buf
.write_str(buf
)
540 // Check if we're over the minimum width, if so then we can also
541 // just write the bytes.
542 Some(min
) if width
>= min
=> {
543 try
!(write_prefix(self)); self.buf
.write_str(buf
)
545 // The sign and prefix goes before the padding if the fill character
547 Some(min
) if self.flags
& (1 << (FlagV1
::SignAwareZeroPad
as u32)) != 0 => {
549 try
!(write_prefix(self));
550 self.with_padding(min
- width
, Alignment
::Right
, |f
| {
554 // Otherwise, the sign and prefix goes after the padding
556 self.with_padding(min
- width
, Alignment
::Right
, |f
| {
557 try
!(write_prefix(f
)); f
.buf
.write_str(buf
)
563 /// This function takes a string slice and emits it to the internal buffer
564 /// after applying the relevant formatting flags specified. The flags
565 /// recognized for generic strings are:
567 /// * width - the minimum width of what to emit
568 /// * fill/align - what to emit and where to emit it if the string
569 /// provided needs to be padded
570 /// * precision - the maximum length to emit, the string is truncated if it
571 /// is longer than this length
573 /// Notably this function ignored the `flag` parameters
574 #[stable(feature = "rust1", since = "1.0.0")]
575 pub fn pad(&mut self, s
: &str) -> Result
{
576 // Make sure there's a fast path up front
577 if self.width
.is_none() && self.precision
.is_none() {
578 return self.buf
.write_str(s
);
580 // The `precision` field can be interpreted as a `max-width` for the
581 // string being formatted
582 match self.precision
{
584 // If there's a maximum width and our string is longer than
585 // that, then we must always have truncation. This is the only
586 // case where the maximum length will matter.
587 let char_len
= s
.char_len();
589 let nchars
= ::cmp
::min(max
, char_len
);
590 return self.buf
.write_str(s
.slice_chars(0, nchars
));
595 // The `width` field is more of a `min-width` parameter at this point.
597 // If we're under the maximum length, and there's no minimum length
598 // requirements, then we can just emit the string
599 None
=> self.buf
.write_str(s
),
600 // If we're under the maximum width, check if we're over the minimum
601 // width, if so it's as easy as just emitting the string.
602 Some(width
) if s
.char_len() >= width
=> {
603 self.buf
.write_str(s
)
605 // If we're under both the maximum and the minimum width, then fill
606 // up the minimum width with the specified string + some alignment.
608 self.with_padding(width
- s
.char_len(), Alignment
::Left
, |me
| {
615 /// Runs a callback, emitting the correct padding either before or
616 /// afterwards depending on whether right or left alignment is requested.
617 fn with_padding
<F
>(&mut self, padding
: usize, default: Alignment
,
619 where F
: FnOnce(&mut Formatter
) -> Result
,
622 let align
= match self.align
{
623 Alignment
::Unknown
=> default,
627 let (pre_pad
, post_pad
) = match align
{
628 Alignment
::Left
=> (0, padding
),
629 Alignment
::Right
| Alignment
::Unknown
=> (padding
, 0),
630 Alignment
::Center
=> (padding
/ 2, (padding
+ 1) / 2),
633 let mut fill
= [0; 4];
634 let len
= self.fill
.encode_utf8(&mut fill
).unwrap_or(0);
635 let fill
= unsafe { str::from_utf8_unchecked(&fill[..len]) }
;
637 for _
in 0..pre_pad
{
638 try
!(self.buf
.write_str(fill
));
643 for _
in 0..post_pad
{
644 try
!(self.buf
.write_str(fill
));
650 /// Takes the formatted parts and applies the padding.
651 /// Assumes that the caller already has rendered the parts with required precision,
652 /// so that `self.precision` can be ignored.
653 fn pad_formatted_parts(&mut self, formatted
: &flt2dec
::Formatted
) -> Result
{
654 if let Some(mut width
) = self.width
{
655 // for the sign-aware zero padding, we render the sign first and
656 // behave as if we had no sign from the beginning.
657 let mut formatted
= formatted
.clone();
658 let mut align
= self.align
;
659 let old_fill
= self.fill
;
660 if self.flags
& (1 << (FlagV1
::SignAwareZeroPad
as u32)) != 0 {
661 // a sign always goes first
662 let sign
= unsafe { str::from_utf8_unchecked(formatted.sign) }
;
663 try
!(self.buf
.write_str(sign
));
665 // remove the sign from the formatted parts
666 formatted
.sign
= b
"";
667 width
= if width
< sign
.len() { 0 }
else { width - sign.len() }
;
668 align
= Alignment
::Right
;
672 // remaining parts go through the ordinary padding process.
673 let len
= formatted
.len();
674 let ret
= if width
<= len
{ // no padding
675 self.write_formatted_parts(&formatted
)
677 self.with_padding(width
- len
, align
, |f
| {
678 f
.write_formatted_parts(&formatted
)
681 self.fill
= old_fill
;
684 // this is the common case and we take a shortcut
685 self.write_formatted_parts(formatted
)
689 fn write_formatted_parts(&mut self, formatted
: &flt2dec
::Formatted
) -> Result
{
690 fn write_bytes(buf
: &mut Write
, s
: &[u8]) -> Result
{
691 buf
.write_str(unsafe { str::from_utf8_unchecked(s) }
)
694 if !formatted
.sign
.is_empty() {
695 try
!(write_bytes(self.buf
, formatted
.sign
));
697 for part
in formatted
.parts
{
699 flt2dec
::Part
::Zero(mut nzeroes
) => {
700 const ZEROES
: &'
static str = // 64 zeroes
701 "0000000000000000000000000000000000000000000000000000000000000000";
702 while nzeroes
> ZEROES
.len() {
703 try
!(self.buf
.write_str(ZEROES
));
704 nzeroes
-= ZEROES
.len();
707 try
!(self.buf
.write_str(&ZEROES
[..nzeroes
]));
710 flt2dec
::Part
::Num(mut v
) => {
712 let len
= part
.len();
713 for c
in s
[..len
].iter_mut().rev() {
714 *c
= b'
0'
+ (v
% 10) as u8;
717 try
!(write_bytes(self.buf
, &s
[..len
]));
719 flt2dec
::Part
::Copy(buf
) => {
720 try
!(write_bytes(self.buf
, buf
));
727 /// Writes some data to the underlying buffer contained within this
729 #[stable(feature = "rust1", since = "1.0.0")]
730 pub fn write_str(&mut self, data
: &str) -> Result
{
731 self.buf
.write_str(data
)
734 /// Writes some formatted information into this instance
735 #[stable(feature = "rust1", since = "1.0.0")]
736 pub fn write_fmt(&mut self, fmt
: Arguments
) -> Result
{
740 /// Flags for formatting (packed version of rt::Flag)
741 #[stable(feature = "rust1", since = "1.0.0")]
742 pub fn flags(&self) -> u32 { self.flags }
744 /// Character used as 'fill' whenever there is alignment
745 #[unstable(feature = "fmt_flags", reason = "method was just created")]
746 pub fn fill(&self) -> char { self.fill }
748 /// Flag indicating what form of alignment was requested
749 #[unstable(feature = "fmt_flags", reason = "method was just created")]
750 pub fn align(&self) -> Alignment { self.align }
752 /// Optionally specified integer width that the output should be
753 #[unstable(feature = "fmt_flags", reason = "method was just created")]
754 pub fn width(&self) -> Option
<usize> { self.width }
756 /// Optionally specified precision for numeric types
757 #[unstable(feature = "fmt_flags", reason = "method was just created")]
758 pub fn precision(&self) -> Option
<usize> { self.precision }
760 /// Creates a `DebugStruct` builder designed to assist with creation of
761 /// `fmt::Debug` implementations for structs.
773 /// impl fmt::Debug for Foo {
774 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
775 /// fmt.debug_struct("Foo")
776 /// .field("bar", &self.bar)
777 /// .field("baz", &self.baz)
782 /// // prints "Foo { bar: 10, baz: "Hello World" }"
783 /// println!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() });
785 #[stable(feature = "debug_builders", since = "1.2.0")]
787 pub fn debug_struct
<'b
>(&'b
mut self, name
: &str) -> DebugStruct
<'b
, 'a
> {
788 builders
::debug_struct_new(self, name
)
791 /// Creates a `DebugTuple` builder designed to assist with creation of
792 /// `fmt::Debug` implementations for tuple structs.
799 /// struct Foo(i32, String);
801 /// impl fmt::Debug for Foo {
802 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
803 /// fmt.debug_tuple("Foo")
810 /// // prints "Foo(10, "Hello World")"
811 /// println!("{:?}", Foo(10, "Hello World".to_string()));
813 #[stable(feature = "debug_builders", since = "1.2.0")]
815 pub fn debug_tuple
<'b
>(&'b
mut self, name
: &str) -> DebugTuple
<'b
, 'a
> {
816 builders
::debug_tuple_new(self, name
)
819 /// Creates a `DebugList` builder designed to assist with creation of
820 /// `fmt::Debug` implementations for list-like structures.
827 /// struct Foo(Vec<i32>);
829 /// impl fmt::Debug for Foo {
830 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
831 /// fmt.debug_list().entries(self.0.iter()).finish()
835 /// // prints "[10, 11]"
836 /// println!("{:?}", Foo(vec![10, 11]));
838 #[stable(feature = "debug_builders", since = "1.2.0")]
840 pub fn debug_list
<'b
>(&'b
mut self) -> DebugList
<'b
, 'a
> {
841 builders
::debug_list_new(self)
844 /// Creates a `DebugSet` builder designed to assist with creation of
845 /// `fmt::Debug` implementations for set-like structures.
852 /// struct Foo(Vec<i32>);
854 /// impl fmt::Debug for Foo {
855 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
856 /// fmt.debug_set().entries(self.0.iter()).finish()
860 /// // prints "{10, 11}"
861 /// println!("{:?}", Foo(vec![10, 11]));
863 #[stable(feature = "debug_builders", since = "1.2.0")]
865 pub fn debug_set
<'b
>(&'b
mut self) -> DebugSet
<'b
, 'a
> {
866 builders
::debug_set_new(self)
869 /// Creates a `DebugMap` builder designed to assist with creation of
870 /// `fmt::Debug` implementations for map-like structures.
877 /// struct Foo(Vec<(String, i32)>);
879 /// impl fmt::Debug for Foo {
880 /// fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
881 /// fmt.debug_map().entries(self.0.iter().map(|&(ref k, ref v)| (k, v))).finish()
885 /// // prints "{"A": 10, "B": 11}"
886 /// println!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)]));
888 #[stable(feature = "debug_builders", since = "1.2.0")]
890 pub fn debug_map
<'b
>(&'b
mut self) -> DebugMap
<'b
, 'a
> {
891 builders
::debug_map_new(self)
895 #[stable(since = "1.2.0", feature = "formatter_write")]
896 impl<'a
> Write
for Formatter
<'a
> {
897 fn write_str(&mut self, s
: &str) -> Result
{
898 self.buf
.write_str(s
)
901 fn write_char(&mut self, c
: char) -> Result
{
902 self.buf
.write_char(c
)
905 fn write_fmt(&mut self, args
: Arguments
) -> Result
{
906 write(self.buf
, args
)
910 #[stable(feature = "rust1", since = "1.0.0")]
911 impl Display
for Error
{
912 fn fmt(&self, f
: &mut Formatter
) -> Result
{
913 Display
::fmt("an error occurred when formatting an argument", f
)
917 // Implementations of the core formatting traits
919 macro_rules
! fmt_refs
{
920 ($
($tr
:ident
),*) => {
922 #[stable(feature = "rust1", since = "1.0.0")]
923 impl<'a
, T
: ?Sized
+ $tr
> $tr
for &'a T
{
924 fn fmt(&self, f
: &mut Formatter
) -> Result { $tr::fmt(&**self, f) }
926 #[stable(feature = "rust1", since = "1.0.0")]
927 impl<'a
, T
: ?Sized
+ $tr
> $tr
for &'a
mut T
{
928 fn fmt(&self, f
: &mut Formatter
) -> Result { $tr::fmt(&**self, f) }
934 fmt_refs
! { Debug, Display, Octal, Binary, LowerHex, UpperHex, LowerExp, UpperExp }
936 #[stable(feature = "rust1", since = "1.0.0")]
937 impl Debug
for bool
{
938 fn fmt(&self, f
: &mut Formatter
) -> Result
{
939 Display
::fmt(self, f
)
943 #[stable(feature = "rust1", since = "1.0.0")]
944 impl Display
for bool
{
945 fn fmt(&self, f
: &mut Formatter
) -> Result
{
946 Display
::fmt(if *self { "true" }
else { "false" }
, f
)
950 #[stable(feature = "rust1", since = "1.0.0")]
952 fn fmt(&self, f
: &mut Formatter
) -> Result
{
953 try
!(write
!(f
, "\""));
954 for c
in self.chars().flat_map(|c
| c
.escape_default()) {
955 try
!(write
!(f
, "{}", c
));
961 #[stable(feature = "rust1", since = "1.0.0")]
962 impl Display
for str {
963 fn fmt(&self, f
: &mut Formatter
) -> Result
{
968 #[stable(feature = "rust1", since = "1.0.0")]
969 impl Debug
for char {
970 fn fmt(&self, f
: &mut Formatter
) -> Result
{
972 try
!(write
!(f
, "'"));
973 for c
in self.escape_default() {
974 try
!(write
!(f
, "{}", c
));
980 #[stable(feature = "rust1", since = "1.0.0")]
981 impl Display
for char {
982 fn fmt(&self, f
: &mut Formatter
) -> Result
{
983 if f
.width
.is_none() && f
.precision
.is_none() {
986 let mut utf8
= [0; 4];
987 let amt
= self.encode_utf8(&mut utf8
).unwrap_or(0);
988 let s
: &str = unsafe { mem::transmute(&utf8[..amt]) }
;
994 #[stable(feature = "rust1", since = "1.0.0")]
995 impl<T
> Pointer
for *const T
{
996 fn fmt(&self, f
: &mut Formatter
) -> Result
{
997 let old_width
= f
.width
;
998 let old_flags
= f
.flags
;
1000 // The alternate flag is already treated by LowerHex as being special-
1001 // it denotes whether to prefix with 0x. We use it to work out whether
1002 // or not to zero extend, and then unconditionally set it to get the
1004 if f
.flags
& 1 << (FlagV1
::Alternate
as u32) > 0 {
1005 f
.flags
|= 1 << (FlagV1
::SignAwareZeroPad
as u32);
1007 if let None
= f
.width
{
1008 // The formats need two extra bytes, for the 0x
1009 if cfg
!(target_pointer_width
= "32") {
1016 f
.flags
|= 1 << (FlagV1
::Alternate
as u32);
1018 let ret
= LowerHex
::fmt(&(*self as usize), f
);
1020 f
.width
= old_width
;
1021 f
.flags
= old_flags
;
1027 #[stable(feature = "rust1", since = "1.0.0")]
1028 impl<T
> Pointer
for *mut T
{
1029 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1030 // FIXME(#23542) Replace with type ascription.
1031 #![allow(trivial_casts)]
1032 Pointer
::fmt(&(*self as *const T
), f
)
1036 #[stable(feature = "rust1", since = "1.0.0")]
1037 impl<'a
, T
> Pointer
for &'a T
{
1038 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1039 // FIXME(#23542) Replace with type ascription.
1040 #![allow(trivial_casts)]
1041 Pointer
::fmt(&(*self as *const T
), f
)
1045 #[stable(feature = "rust1", since = "1.0.0")]
1046 impl<'a
, T
> Pointer
for &'a
mut T
{
1047 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1048 // FIXME(#23542) Replace with type ascription.
1049 #![allow(trivial_casts)]
1050 Pointer
::fmt(&(&**self as *const T
), f
)
1054 // Common code of floating point Debug and Display.
1055 fn float_to_decimal_common
<T
>(fmt
: &mut Formatter
, num
: &T
, negative_zero
: bool
) -> Result
1056 where T
: flt2dec
::DecodableFloat
1058 let force_sign
= fmt
.flags
& (1 << (FlagV1
::SignPlus
as u32)) != 0;
1059 let sign
= match (force_sign
, negative_zero
) {
1060 (false, false) => flt2dec
::Sign
::Minus
,
1061 (false, true) => flt2dec
::Sign
::MinusRaw
,
1062 (true, false) => flt2dec
::Sign
::MinusPlus
,
1063 (true, true) => flt2dec
::Sign
::MinusPlusRaw
,
1066 let mut buf
= [0; 1024]; // enough for f32 and f64
1067 let mut parts
= [flt2dec
::Part
::Zero(0); 16];
1068 let formatted
= if let Some(precision
) = fmt
.precision
{
1069 flt2dec
::to_exact_fixed_str(flt2dec
::strategy
::grisu
::format_exact
, *num
, sign
,
1070 precision
, false, &mut buf
, &mut parts
)
1072 flt2dec
::to_shortest_str(flt2dec
::strategy
::grisu
::format_shortest
, *num
, sign
,
1073 0, false, &mut buf
, &mut parts
)
1075 fmt
.pad_formatted_parts(&formatted
)
1078 // Common code of floating point LowerExp and UpperExp.
1079 fn float_to_exponential_common
<T
>(fmt
: &mut Formatter
, num
: &T
, upper
: bool
) -> Result
1080 where T
: flt2dec
::DecodableFloat
1082 let force_sign
= fmt
.flags
& (1 << (FlagV1
::SignPlus
as u32)) != 0;
1083 let sign
= match force_sign
{
1084 false => flt2dec
::Sign
::Minus
,
1085 true => flt2dec
::Sign
::MinusPlus
,
1088 let mut buf
= [0; 1024]; // enough for f32 and f64
1089 let mut parts
= [flt2dec
::Part
::Zero(0); 16];
1090 let formatted
= if let Some(precision
) = fmt
.precision
{
1091 // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
1092 flt2dec
::to_exact_exp_str(flt2dec
::strategy
::grisu
::format_exact
, *num
, sign
,
1093 precision
+ 1, upper
, &mut buf
, &mut parts
)
1095 flt2dec
::to_shortest_exp_str(flt2dec
::strategy
::grisu
::format_shortest
, *num
, sign
,
1096 (0, 0), upper
, &mut buf
, &mut parts
)
1098 fmt
.pad_formatted_parts(&formatted
)
1101 macro_rules
! floating
{ ($ty
:ident
) => {
1103 #[stable(feature = "rust1", since = "1.0.0")]
1104 impl Debug
for $ty
{
1105 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1106 float_to_decimal_common(fmt
, self, true)
1110 #[stable(feature = "rust1", since = "1.0.0")]
1111 impl Display
for $ty
{
1112 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1113 float_to_decimal_common(fmt
, self, false)
1117 #[stable(feature = "rust1", since = "1.0.0")]
1118 impl LowerExp
for $ty
{
1119 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1120 float_to_exponential_common(fmt
, self, false)
1124 #[stable(feature = "rust1", since = "1.0.0")]
1125 impl UpperExp
for $ty
{
1126 fn fmt(&self, fmt
: &mut Formatter
) -> Result
{
1127 float_to_exponential_common(fmt
, self, true)
1134 // Implementation of Display/Debug for various core types
1136 #[stable(feature = "rust1", since = "1.0.0")]
1137 impl<T
> Debug
for *const T
{
1138 fn fmt(&self, f
: &mut Formatter
) -> Result { Pointer::fmt(self, f) }
1140 #[stable(feature = "rust1", since = "1.0.0")]
1141 impl<T
> Debug
for *mut T
{
1142 fn fmt(&self, f
: &mut Formatter
) -> Result { Pointer::fmt(self, f) }
1146 ($name
:ident
, $
($other
:ident
,)*) => (tuple
! { $($other,)* }
)
1149 macro_rules
! tuple
{
1151 ( $
($name
:ident
,)+ ) => (
1152 #[stable(feature = "rust1", since = "1.0.0")]
1153 impl<$
($name
:Debug
),*> Debug
for ($
($name
,)*) {
1154 #[allow(non_snake_case, unused_assignments)]
1155 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1156 try
!(write
!(f
, "("));
1157 let ($
(ref $name
,)*) = *self;
1161 try
!(write
!(f
, ", "));
1163 try
!(write
!(f
, "{:?}", *$name
));
1167 try
!(write
!(f
, ","));
1172 peel
! { $($name,)* }
1176 tuple
! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
1178 #[stable(feature = "rust1", since = "1.0.0")]
1179 impl<T
: Debug
> Debug
for [T
] {
1180 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1181 f
.debug_list().entries(self.iter()).finish()
1185 #[stable(feature = "rust1", since = "1.0.0")]
1187 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1191 impl<T
> Debug
for PhantomData
<T
> {
1192 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1193 f
.pad("PhantomData")
1197 #[stable(feature = "rust1", since = "1.0.0")]
1198 impl<T
: Copy
+ Debug
> Debug
for Cell
<T
> {
1199 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1200 write
!(f
, "Cell {{ value: {:?} }}", self.get())
1204 #[stable(feature = "rust1", since = "1.0.0")]
1205 impl<T
: ?Sized
+ Debug
> Debug
for RefCell
<T
> {
1206 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1207 match self.borrow_state() {
1208 BorrowState
::Unused
| BorrowState
::Reading
=> {
1209 write
!(f
, "RefCell {{ value: {:?} }}", self.borrow())
1211 BorrowState
::Writing
=> write
!(f
, "RefCell {{ <borrowed> }}"),
1216 #[stable(feature = "rust1", since = "1.0.0")]
1217 impl<'b
, T
: ?Sized
+ Debug
> Debug
for Ref
<'b
, T
> {
1218 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1219 Debug
::fmt(&**self, f
)
1223 #[stable(feature = "rust1", since = "1.0.0")]
1224 impl<'b
, T
: ?Sized
+ Debug
> Debug
for RefMut
<'b
, T
> {
1225 fn fmt(&self, f
: &mut Formatter
) -> Result
{
1226 Debug
::fmt(&*(self.deref()), f
)
1230 // If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
1231 // it's a lot easier than creating all of the rt::Piece structures here.