1 // Copyright 2013-2014 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 #![allow(unused_variables)]
16 use cell::{Cell, Ref, RefMut};
17 use iter::{Iterator, IteratorExt, range};
18 use kinds::{Copy, Sized};
21 use option::Option::{Some, None};
23 use result::Result::{Ok, Err};
25 use slice::SlicePrelude;
29 pub use self::num::radix;
30 pub use self::num::Radix;
31 pub use self::num::RadixFmt;
37 #[experimental = "core and I/O reconciliation may alter this definition"]
38 /// The type returned by formatter methods.
39 pub type Result = result::Result<(), Error>;
41 /// The error type which is returned from formatting a message into a stream.
43 /// This type does not support transmission of an error other than that an error
44 /// occurred. Any extra information must be arranged to be transmitted through
46 #[experimental = "core and I/O reconciliation may alter this definition"]
49 impl Copy for Error {}
51 /// A collection of methods that are required to format a message into a stream.
53 /// This trait is the type which this modules requires when formatting
54 /// information. This is similar to the standard library's `io::Writer` trait,
55 /// but it is only intended for use in libcore.
57 /// This trait should generally not be implemented by consumers of the standard
58 /// library. The `write!` macro accepts an instance of `io::Writer`, and the
59 /// `io::Writer` trait is favored over implementing this trait.
60 #[experimental = "waiting for core and I/O reconciliation"]
61 pub trait FormatWriter {
62 /// Writes a slice of bytes into this writer, returning whether the write
65 /// This method can only succeed if the entire byte slice was successfully
66 /// written, and this method will not return until all data has been
67 /// written or an error occurs.
71 /// This function will return an instance of `FormatError` on error.
72 fn write(&mut self, bytes: &[u8]) -> Result;
74 /// Glue for usage of the `write!` macro with implementers of this trait.
76 /// This method should generally not be invoked manually, but rather through
77 /// the `write!` macro itself.
78 fn write_fmt(&mut self, args: &Arguments) -> Result { write(self, args) }
81 /// A struct to represent both where to emit formatting strings to and how they
82 /// should be formatted. A mutable version of this is passed to all formatting
84 #[unstable = "name may change and implemented traits are also unstable"]
85 pub struct Formatter<'a> {
90 precision: Option<uint>,
92 buf: &'a mut (FormatWriter+'a),
93 curarg: slice::Items<'a, Argument<'a>>,
94 args: &'a [Argument<'a>],
97 // NB. Argument is essentially an optimized partially applied formatting function,
98 // equivalent to `exists T.(&T, fn(&T, &mut Formatter) -> Result`.
102 /// This struct represents the generic "argument" which is taken by the Xprintf
103 /// family of functions. It contains a function to format the given value. At
104 /// compile time it is ensured that the function and the value have the correct
105 /// types, and then this struct is used to canonicalize arguments to one type.
106 #[experimental = "implementation detail of the `format_args!` macro"]
107 pub struct Argument<'a> {
109 formatter: fn(&Void, &mut Formatter) -> Result,
112 impl<'a> Argument<'a> {
114 fn show_uint(x: &uint, f: &mut Formatter) -> Result {
118 fn new<'a, T>(x: &'a T, f: fn(&T, &mut Formatter) -> Result) -> Argument<'a> {
121 formatter: mem::transmute(f),
122 value: mem::transmute(x)
127 fn from_uint<'a>(x: &'a uint) -> Argument<'a> {
128 Argument::new(x, Argument::show_uint)
131 fn as_uint(&self) -> Option<uint> {
132 if self.formatter as uint == Argument::show_uint as uint {
133 Some(unsafe { *(self.value as *const _ as *const uint) })
140 impl<'a> Copy for Argument<'a> {}
142 impl<'a> Arguments<'a> {
143 /// When using the format_args!() macro, this function is used to generate the
144 /// Arguments structure.
145 #[doc(hidden)] #[inline]
146 #[experimental = "implementation detail of the `format_args!` macro"]
147 pub fn new<'a>(pieces: &'a [&'a str],
148 args: &'a [Argument<'a>]) -> Arguments<'a> {
156 /// This function is used to specify nonstandard formatting parameters.
157 /// The `pieces` array must be at least as long as `fmt` to construct
158 /// a valid Arguments structure. Also, any `Count` within `fmt` that is
159 /// `CountIsParam` or `CountIsNextParam` has to point to an argument
160 /// created with `argumentuint`. However, failing to do so doesn't cause
161 /// unsafety, but will ignore invalid .
162 #[doc(hidden)] #[inline]
163 #[experimental = "implementation detail of the `format_args!` macro"]
164 pub fn with_placeholders<'a>(pieces: &'a [&'a str],
165 fmt: &'a [rt::Argument<'a>],
166 args: &'a [Argument<'a>]) -> Arguments<'a> {
175 /// This structure represents a safely precompiled version of a format string
176 /// and its arguments. This cannot be generated at runtime because it cannot
177 /// safely be done so, so no constructors are given and the fields are private
178 /// to prevent modification.
180 /// The `format_args!` macro will safely create an instance of this structure
181 /// and pass it to a function or closure, passed as the first argument. The
182 /// macro validates the format string at compile-time so usage of the `write`
183 /// and `format` functions can be safely performed.
185 pub struct Arguments<'a> {
186 // Format string pieces to print.
187 pieces: &'a [&'a str],
189 // Placeholder specs, or `None` if all specs are default (as in "{}{}").
190 fmt: Option<&'a [rt::Argument<'a>]>,
192 // Dynamic arguments for interpolation, to be interleaved with string
193 // pieces. (Every argument is preceded by a string piece.)
194 args: &'a [Argument<'a>],
197 impl<'a> Show for Arguments<'a> {
198 fn fmt(&self, fmt: &mut Formatter) -> Result {
203 /// When a format is not otherwise specified, types are formatted by ascribing
204 /// to this trait. There is not an explicit way of selecting this trait to be
205 /// used for formatting, it is only if no other format is specified.
206 #[unstable = "I/O and core have yet to be reconciled"]
207 pub trait Show for Sized? {
208 /// Formats the value using the given formatter.
209 fn fmt(&self, &mut Formatter) -> Result;
213 /// Format trait for the `o` character
214 #[unstable = "I/O and core have yet to be reconciled"]
215 pub trait Octal for Sized? {
216 /// Formats the value using the given formatter.
217 fn fmt(&self, &mut Formatter) -> Result;
220 /// Format trait for the `b` character
221 #[unstable = "I/O and core have yet to be reconciled"]
222 pub trait Binary for Sized? {
223 /// Formats the value using the given formatter.
224 fn fmt(&self, &mut Formatter) -> Result;
227 /// Format trait for the `x` character
228 #[unstable = "I/O and core have yet to be reconciled"]
229 pub trait LowerHex for Sized? {
230 /// Formats the value using the given formatter.
231 fn fmt(&self, &mut Formatter) -> Result;
234 /// Format trait for the `X` character
235 #[unstable = "I/O and core have yet to be reconciled"]
236 pub trait UpperHex for Sized? {
237 /// Formats the value using the given formatter.
238 fn fmt(&self, &mut Formatter) -> Result;
241 /// Format trait for the `p` character
242 #[unstable = "I/O and core have yet to be reconciled"]
243 pub trait Pointer for Sized? {
244 /// Formats the value using the given formatter.
245 fn fmt(&self, &mut Formatter) -> Result;
248 /// Format trait for the `e` character
249 #[unstable = "I/O and core have yet to be reconciled"]
250 pub trait LowerExp for Sized? {
251 /// Formats the value using the given formatter.
252 fn fmt(&self, &mut Formatter) -> Result;
255 /// Format trait for the `E` character
256 #[unstable = "I/O and core have yet to be reconciled"]
257 pub trait UpperExp for Sized? {
258 /// Formats the value using the given formatter.
259 fn fmt(&self, &mut Formatter) -> Result;
262 static DEFAULT_ARGUMENT: rt::Argument<'static> = rt::Argument {
263 position: rt::ArgumentNext,
264 format: rt::FormatSpec {
266 align: rt::AlignUnknown,
268 precision: rt::CountImplied,
269 width: rt::CountImplied,
273 /// The `write` function takes an output stream, a precompiled format string,
274 /// and a list of arguments. The arguments will be formatted according to the
275 /// specified format string into the output stream provided.
279 /// * output - the buffer to write output to
280 /// * args - the precompiled arguments generated by `format_args!`
281 #[experimental = "libcore and I/O have yet to be reconciled, and this is an \
282 implementation detail which should not otherwise be exported"]
283 pub fn write(output: &mut FormatWriter, args: &Arguments) -> Result {
284 let mut formatter = Formatter {
289 align: rt::AlignUnknown,
292 curarg: args.args.iter(),
295 let mut pieces = args.pieces.iter();
299 // We can use default formatting parameters for all arguments.
300 for _ in range(0, args.args.len()) {
301 try!(formatter.buf.write(pieces.next().unwrap().as_bytes()));
302 try!(formatter.run(&DEFAULT_ARGUMENT));
306 // Every spec has a corresponding argument that is preceded by
308 for (arg, piece) in fmt.iter().zip(pieces.by_ref()) {
309 try!(formatter.buf.write(piece.as_bytes()));
310 try!(formatter.run(arg));
315 // There can be only one trailing string piece left.
316 match pieces.next() {
318 try!(formatter.buf.write(piece.as_bytes()));
326 impl<'a> Formatter<'a> {
328 // First up is the collection of functions used to execute a format string
329 // at runtime. This consumes all of the compile-time statics generated by
330 // the format! syntax extension.
331 fn run(&mut self, arg: &rt::Argument) -> Result {
332 // Fill in the format parameters into the formatter
333 self.fill = arg.format.fill;
334 self.align = arg.format.align;
335 self.flags = arg.format.flags;
336 self.width = self.getcount(&arg.format.width);
337 self.precision = self.getcount(&arg.format.precision);
339 // Extract the correct argument
340 let value = match arg.position {
341 rt::ArgumentNext => { *self.curarg.next().unwrap() }
342 rt::ArgumentIs(i) => self.args[i],
345 // Then actually do some printing
346 (value.formatter)(value.value, self)
349 fn getcount(&mut self, cnt: &rt::Count) -> Option<uint> {
351 rt::CountIs(n) => Some(n),
352 rt::CountImplied => None,
353 rt::CountIsParam(i) => {
354 self.args[i].as_uint()
356 rt::CountIsNextParam => {
357 self.curarg.next().and_then(|arg| arg.as_uint())
362 // Helper methods used for padding and processing formatting arguments that
363 // all formatting traits can use.
365 /// Performs the correct padding for an integer which has already been
366 /// emitted into a byte-array. The byte-array should *not* contain the sign
367 /// for the integer, that will be added by this method.
371 /// * is_positive - whether the original integer was positive or not.
372 /// * prefix - if the '#' character (FlagAlternate) is provided, this
373 /// is the prefix to put in front of the number.
374 /// * buf - the byte array that the number has been formatted into
376 /// This function will correctly account for the flags provided as well as
377 /// the minimum width. It will not take precision into account.
378 #[unstable = "definition may change slightly over time"]
379 pub fn pad_integral(&mut self,
385 use fmt::rt::{FlagAlternate, FlagSignPlus, FlagSignAwareZeroPad};
387 let mut width = buf.len();
391 sign = Some('-'); width += 1;
392 } else if self.flags & (1 << (FlagSignPlus as uint)) != 0 {
393 sign = Some('+'); width += 1;
396 let mut prefixed = false;
397 if self.flags & (1 << (FlagAlternate as uint)) != 0 {
398 prefixed = true; width += prefix.char_len();
401 // Writes the sign if it exists, and then the prefix if it was requested
402 let write_prefix = |f: &mut Formatter| {
403 for c in sign.into_iter() {
404 let mut b = [0, ..4];
405 let n = c.encode_utf8(&mut b).unwrap_or(0);
406 try!(f.buf.write(b[..n]));
408 if prefixed { f.buf.write(prefix.as_bytes()) }
412 // The `width` field is more of a `min-width` parameter at this point.
414 // If there's no minimum length requirements then we can just
417 try!(write_prefix(self)); self.buf.write(buf)
419 // Check if we're over the minimum width, if so then we can also
420 // just write the bytes.
421 Some(min) if width >= min => {
422 try!(write_prefix(self)); self.buf.write(buf)
424 // The sign and prefix goes before the padding if the fill character
426 Some(min) if self.flags & (1 << (FlagSignAwareZeroPad as uint)) != 0 => {
428 try!(write_prefix(self));
429 self.with_padding(min - width, rt::AlignRight, |f| f.buf.write(buf))
431 // Otherwise, the sign and prefix goes after the padding
433 self.with_padding(min - width, rt::AlignRight, |f| {
434 try!(write_prefix(f)); f.buf.write(buf)
440 /// This function takes a string slice and emits it to the internal buffer
441 /// after applying the relevant formatting flags specified. The flags
442 /// recognized for generic strings are:
444 /// * width - the minimum width of what to emit
445 /// * fill/align - what to emit and where to emit it if the string
446 /// provided needs to be padded
447 /// * precision - the maximum length to emit, the string is truncated if it
448 /// is longer than this length
450 /// Notably this function ignored the `flag` parameters
451 #[unstable = "definition may change slightly over time"]
452 pub fn pad(&mut self, s: &str) -> Result {
453 // Make sure there's a fast path up front
454 if self.width.is_none() && self.precision.is_none() {
455 return self.buf.write(s.as_bytes());
457 // The `precision` field can be interpreted as a `max-width` for the
458 // string being formatted
459 match self.precision {
461 // If there's a maximum width and our string is longer than
462 // that, then we must always have truncation. This is the only
463 // case where the maximum length will matter.
464 let char_len = s.char_len();
466 let nchars = ::cmp::min(max, char_len);
467 return self.buf.write(s.slice_chars(0, nchars).as_bytes());
472 // The `width` field is more of a `min-width` parameter at this point.
474 // If we're under the maximum length, and there's no minimum length
475 // requirements, then we can just emit the string
476 None => self.buf.write(s.as_bytes()),
477 // If we're under the maximum width, check if we're over the minimum
478 // width, if so it's as easy as just emitting the string.
479 Some(width) if s.char_len() >= width => {
480 self.buf.write(s.as_bytes())
482 // If we're under both the maximum and the minimum width, then fill
483 // up the minimum width with the specified string + some alignment.
485 self.with_padding(width - s.char_len(), rt::AlignLeft, |me| {
486 me.buf.write(s.as_bytes())
492 /// Runs a callback, emitting the correct padding either before or
493 /// afterwards depending on whether right or left alignment is requested.
494 fn with_padding(&mut self,
496 default: rt::Alignment,
497 f: |&mut Formatter| -> Result) -> Result {
499 let align = match self.align {
500 rt::AlignUnknown => default,
504 let (pre_pad, post_pad) = match align {
505 rt::AlignLeft => (0u, padding),
506 rt::AlignRight | rt::AlignUnknown => (padding, 0u),
507 rt::AlignCenter => (padding / 2, (padding + 1) / 2),
510 let mut fill = [0u8, ..4];
511 let len = self.fill.encode_utf8(&mut fill).unwrap_or(0);
513 for _ in range(0, pre_pad) {
514 try!(self.buf.write(fill[..len]));
519 for _ in range(0, post_pad) {
520 try!(self.buf.write(fill[..len]));
526 /// Writes some data to the underlying buffer contained within this
528 #[unstable = "reconciling core and I/O may alter this definition"]
529 pub fn write(&mut self, data: &[u8]) -> Result {
533 /// Writes some formatted information into this instance
534 #[unstable = "reconciling core and I/O may alter this definition"]
535 pub fn write_fmt(&mut self, fmt: &Arguments) -> Result {
539 /// Flags for formatting (packed version of rt::Flag)
540 #[experimental = "return type may change and method was just created"]
541 pub fn flags(&self) -> uint { self.flags }
543 /// Character used as 'fill' whenever there is alignment
544 #[unstable = "method was just created"]
545 pub fn fill(&self) -> char { self.fill }
547 /// Flag indicating what form of alignment was requested
548 #[unstable = "method was just created"]
549 pub fn align(&self) -> rt::Alignment { self.align }
551 /// Optionally specified integer width that the output should be
552 #[unstable = "method was just created"]
553 pub fn width(&self) -> Option<uint> { self.width }
555 /// Optionally specified precision for numeric types
556 #[unstable = "method was just created"]
557 pub fn precision(&self) -> Option<uint> { self.precision }
560 impl Show for Error {
561 fn fmt(&self, f: &mut Formatter) -> Result {
562 "an error occurred when formatting an argument".fmt(f)
566 /// This is a function which calls are emitted to by the compiler itself to
567 /// create the Argument structures that are passed into the `format` function.
568 #[doc(hidden)] #[inline]
569 #[experimental = "implementation detail of the `format_args!` macro"]
570 pub fn argument<'a, T>(f: fn(&T, &mut Formatter) -> Result,
571 t: &'a T) -> Argument<'a> {
575 /// When the compiler determines that the type of an argument *must* be a uint
576 /// (such as for width and precision), then it invokes this method.
577 #[doc(hidden)] #[inline]
578 #[experimental = "implementation detail of the `format_args!` macro"]
579 pub fn argumentuint<'a>(s: &'a uint) -> Argument<'a> {
580 Argument::from_uint(s)
583 // Implementations of the core formatting traits
585 impl<'a, Sized? T: Show> Show for &'a T {
586 fn fmt(&self, f: &mut Formatter) -> Result { (**self).fmt(f) }
588 impl<'a, Sized? T: Show> Show for &'a mut T {
589 fn fmt(&self, f: &mut Formatter) -> Result { (**self).fmt(f) }
591 impl<'a> Show for &'a (Show+'a) {
592 fn fmt(&self, f: &mut Formatter) -> Result { (*self).fmt(f) }
596 fn fmt(&self, f: &mut Formatter) -> Result {
597 Show::fmt(if *self { "true" } else { "false" }, f)
602 fn fmt(&self, f: &mut Formatter) -> Result {
608 fn fmt(&self, f: &mut Formatter) -> Result {
611 let mut utf8 = [0u8, ..4];
612 let amt = self.encode_utf8(&mut utf8).unwrap_or(0);
613 let s: &str = unsafe { mem::transmute(utf8[..amt]) };
618 impl<T> Pointer for *const T {
619 fn fmt(&self, f: &mut Formatter) -> Result {
620 f.flags |= 1 << (rt::FlagAlternate as uint);
621 LowerHex::fmt(&(*self as uint), f)
625 impl<T> Pointer for *mut T {
626 fn fmt(&self, f: &mut Formatter) -> Result {
627 Pointer::fmt(&(*self as *const T), f)
631 impl<'a, T> Pointer for &'a T {
632 fn fmt(&self, f: &mut Formatter) -> Result {
633 Pointer::fmt(&(*self as *const T), f)
637 impl<'a, T> Pointer for &'a mut T {
638 fn fmt(&self, f: &mut Formatter) -> Result {
639 Pointer::fmt(&(&**self as *const T), f)
643 macro_rules! floating(($ty:ident) => {
645 fn fmt(&self, fmt: &mut Formatter) -> Result {
648 let digits = match fmt.precision {
649 Some(i) => float::DigExact(i),
650 None => float::DigMax(6),
652 float::float_to_str_bytes_common(self.abs(),
660 fmt.pad_integral(self.is_nan() || *self >= 0.0, "", bytes)
665 impl LowerExp for $ty {
666 fn fmt(&self, fmt: &mut Formatter) -> Result {
669 let digits = match fmt.precision {
670 Some(i) => float::DigExact(i),
671 None => float::DigMax(6),
673 float::float_to_str_bytes_common(self.abs(),
681 fmt.pad_integral(self.is_nan() || *self >= 0.0, "", bytes)
686 impl UpperExp for $ty {
687 fn fmt(&self, fmt: &mut Formatter) -> Result {
690 let digits = match fmt.precision {
691 Some(i) => float::DigExact(i),
692 None => float::DigMax(6),
694 float::float_to_str_bytes_common(self.abs(),
702 fmt.pad_integral(self.is_nan() || *self >= 0.0, "", bytes)
710 // Implementation of Show for various core types
712 impl<T> Show for *const T {
713 fn fmt(&self, f: &mut Formatter) -> Result { Pointer::fmt(self, f) }
716 impl<T> Show for *mut T {
717 fn fmt(&self, f: &mut Formatter) -> Result { Pointer::fmt(self, f) }
720 macro_rules! peel(($name:ident, $($other:ident,)*) => (tuple!($($other,)*)))
724 ( $($name:ident,)+ ) => (
725 impl<$($name:Show),*> Show for ($($name,)*) {
726 #[allow(non_snake_case, unused_assignments)]
727 fn fmt(&self, f: &mut Formatter) -> Result {
728 try!(write!(f, "("));
729 let ($(ref $name,)*) = *self;
733 try!(write!(f, ", "));
735 try!(write!(f, "{}", *$name));
739 try!(write!(f, ","));
748 tuple! { T0, T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, }
750 impl<'a> Show for &'a (any::Any+'a) {
751 fn fmt(&self, f: &mut Formatter) -> Result { f.pad("&Any") }
754 impl<T: Show> Show for [T] {
755 fn fmt(&self, f: &mut Formatter) -> Result {
756 if f.flags & (1 << (rt::FlagAlternate as uint)) == 0 {
757 try!(write!(f, "["));
759 let mut is_first = true;
760 for x in self.iter() {
764 try!(write!(f, ", "));
766 try!(write!(f, "{}", *x))
768 if f.flags & (1 << (rt::FlagAlternate as uint)) == 0 {
769 try!(write!(f, "]"));
776 fn fmt(&self, f: &mut Formatter) -> Result {
781 impl<T: Copy + Show> Show for Cell<T> {
782 fn fmt(&self, f: &mut Formatter) -> Result {
783 write!(f, "Cell {{ value: {} }}", self.get())
787 impl<'b, T: Show> Show for Ref<'b, T> {
788 fn fmt(&self, f: &mut Formatter) -> Result {
793 impl<'b, T: Show> Show for RefMut<'b, T> {
794 fn fmt(&self, f: &mut Formatter) -> Result {
795 (*(self.deref())).fmt(f)
799 // If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
800 // it's a lot easier than creating all of the rt::Piece structures here.