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};
22 use ops::{Deref, FnOnce};
23 use result::Result::{Ok, Err};
27 use str::{StrExt, Utf8Error};
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"]
50 /// A collection of methods that are required to format a message into a stream.
52 /// This trait is the type which this modules requires when formatting
53 /// information. This is similar to the standard library's `io::Writer` trait,
54 /// but it is only intended for use in libcore.
56 /// This trait should generally not be implemented by consumers of the standard
57 /// library. The `write!` macro accepts an instance of `io::Writer`, and the
58 /// `io::Writer` trait is favored over implementing this trait.
59 #[experimental = "waiting for core and I/O reconciliation"]
60 pub trait FormatWriter {
61 /// Writes a slice of bytes into this writer, returning whether the write
64 /// This method can only succeed if the entire byte slice was successfully
65 /// written, and this method will not return until all data has been
66 /// written or an error occurs.
70 /// This function will return an instance of `FormatError` on error.
71 fn write(&mut self, bytes: &[u8]) -> Result;
73 /// Glue for usage of the `write!` macro with implementers of this trait.
75 /// This method should generally not be invoked manually, but rather through
76 /// the `write!` macro itself.
77 fn write_fmt(&mut self, args: Arguments) -> Result { write(self, args) }
80 /// A struct to represent both where to emit formatting strings to and how they
81 /// should be formatted. A mutable version of this is passed to all formatting
83 #[unstable = "name may change and implemented traits are also unstable"]
84 pub struct Formatter<'a> {
89 precision: Option<uint>,
91 buf: &'a mut (FormatWriter+'a),
92 curarg: slice::Iter<'a, Argument<'a>>,
93 args: &'a [Argument<'a>],
96 // NB. Argument is essentially an optimized partially applied formatting function,
97 // equivalent to `exists T.(&T, fn(&T, &mut Formatter) -> Result`.
101 /// This struct represents the generic "argument" which is taken by the Xprintf
102 /// family of functions. It contains a function to format the given value. At
103 /// compile time it is ensured that the function and the value have the correct
104 /// types, and then this struct is used to canonicalize arguments to one type.
105 #[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<'b, T>(x: &'b T, f: fn(&T, &mut Formatter) -> Result) -> Argument<'b> {
121 formatter: mem::transmute(f),
122 value: mem::transmute(x)
127 fn from_uint(x: &uint) -> Argument {
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> Arguments<'a> {
141 /// When using the format_args!() macro, this function is used to generate the
142 /// Arguments structure.
143 #[doc(hidden)] #[inline]
144 #[experimental = "implementation detail of the `format_args!` macro"]
145 pub fn new(pieces: &'a [&'a str],
146 args: &'a [Argument<'a>]) -> Arguments<'a> {
154 /// This function is used to specify nonstandard formatting parameters.
155 /// The `pieces` array must be at least as long as `fmt` to construct
156 /// a valid Arguments structure. Also, any `Count` within `fmt` that is
157 /// `CountIsParam` or `CountIsNextParam` has to point to an argument
158 /// created with `argumentuint`. However, failing to do so doesn't cause
159 /// unsafety, but will ignore invalid .
160 #[doc(hidden)] #[inline]
161 #[experimental = "implementation detail of the `format_args!` macro"]
162 pub fn with_placeholders(pieces: &'a [&'a str],
163 fmt: &'a [rt::Argument<'a>],
164 args: &'a [Argument<'a>]) -> Arguments<'a> {
173 /// This structure represents a safely precompiled version of a format string
174 /// and its arguments. This cannot be generated at runtime because it cannot
175 /// safely be done so, so no constructors are given and the fields are private
176 /// to prevent modification.
178 /// The `format_args!` macro will safely create an instance of this structure
179 /// and pass it to a function or closure, passed as the first argument. The
180 /// macro validates the format string at compile-time so usage of the `write`
181 /// and `format` functions can be safely performed.
184 pub struct Arguments<'a> {
185 // Format string pieces to print.
186 pieces: &'a [&'a str],
188 // Placeholder specs, or `None` if all specs are default (as in "{}{}").
189 fmt: Option<&'a [rt::Argument<'a>]>,
191 // Dynamic arguments for interpolation, to be interleaved with string
192 // pieces. (Every argument is preceded by a string piece.)
193 args: &'a [Argument<'a>],
196 impl<'a> Show for Arguments<'a> {
197 fn fmt(&self, fmt: &mut Formatter) -> Result {
198 write(fmt.buf, *self)
202 /// When a format is not otherwise specified, types are formatted by ascribing
203 /// to this trait. There is not an explicit way of selecting this trait to be
204 /// used for formatting, it is only if no other format is specified.
205 #[unstable = "I/O and core have yet to be reconciled"]
206 pub trait Show for Sized? {
207 /// Formats the value using the given formatter.
208 fn fmt(&self, &mut Formatter) -> Result;
212 /// Format trait for the `o` character
213 #[unstable = "I/O and core have yet to be reconciled"]
214 pub trait Octal for Sized? {
215 /// Formats the value using the given formatter.
216 fn fmt(&self, &mut Formatter) -> Result;
219 /// Format trait for the `b` character
220 #[unstable = "I/O and core have yet to be reconciled"]
221 pub trait Binary for Sized? {
222 /// Formats the value using the given formatter.
223 fn fmt(&self, &mut Formatter) -> Result;
226 /// Format trait for the `x` character
227 #[unstable = "I/O and core have yet to be reconciled"]
228 pub trait LowerHex for Sized? {
229 /// Formats the value using the given formatter.
230 fn fmt(&self, &mut Formatter) -> Result;
233 /// Format trait for the `X` character
234 #[unstable = "I/O and core have yet to be reconciled"]
235 pub trait UpperHex for Sized? {
236 /// Formats the value using the given formatter.
237 fn fmt(&self, &mut Formatter) -> Result;
240 /// Format trait for the `p` character
241 #[unstable = "I/O and core have yet to be reconciled"]
242 pub trait Pointer for Sized? {
243 /// Formats the value using the given formatter.
244 fn fmt(&self, &mut Formatter) -> Result;
247 /// Format trait for the `e` character
248 #[unstable = "I/O and core have yet to be reconciled"]
249 pub trait LowerExp for Sized? {
250 /// Formats the value using the given formatter.
251 fn fmt(&self, &mut Formatter) -> Result;
254 /// Format trait for the `E` character
255 #[unstable = "I/O and core have yet to be reconciled"]
256 pub trait UpperExp for Sized? {
257 /// Formats the value using the given formatter.
258 fn fmt(&self, &mut Formatter) -> Result;
261 static DEFAULT_ARGUMENT: rt::Argument<'static> = rt::Argument {
262 position: rt::ArgumentNext,
263 format: rt::FormatSpec {
265 align: rt::AlignUnknown,
267 precision: rt::CountImplied,
268 width: rt::CountImplied,
272 /// The `write` function takes an output stream, a precompiled format string,
273 /// and a list of arguments. The arguments will be formatted according to the
274 /// specified format string into the output stream provided.
278 /// * output - the buffer to write output to
279 /// * args - the precompiled arguments generated by `format_args!`
280 #[experimental = "libcore and I/O have yet to be reconciled, and this is an \
281 implementation detail which should not otherwise be exported"]
282 pub fn write(output: &mut FormatWriter, args: Arguments) -> Result {
283 let mut formatter = Formatter {
288 align: rt::AlignUnknown,
291 curarg: args.args.iter(),
294 let mut pieces = args.pieces.iter();
298 // We can use default formatting parameters for all arguments.
299 for _ in range(0, args.args.len()) {
300 try!(formatter.buf.write(pieces.next().unwrap().as_bytes()));
301 try!(formatter.run(&DEFAULT_ARGUMENT));
305 // Every spec has a corresponding argument that is preceded by
307 for (arg, piece) in fmt.iter().zip(pieces.by_ref()) {
308 try!(formatter.buf.write(piece.as_bytes()));
309 try!(formatter.run(arg));
314 // There can be only one trailing string piece left.
315 match pieces.next() {
317 try!(formatter.buf.write(piece.as_bytes()));
325 impl<'a> Formatter<'a> {
327 // First up is the collection of functions used to execute a format string
328 // at runtime. This consumes all of the compile-time statics generated by
329 // the format! syntax extension.
330 fn run(&mut self, arg: &rt::Argument) -> Result {
331 // Fill in the format parameters into the formatter
332 self.fill = arg.format.fill;
333 self.align = arg.format.align;
334 self.flags = arg.format.flags;
335 self.width = self.getcount(&arg.format.width);
336 self.precision = self.getcount(&arg.format.precision);
338 // Extract the correct argument
339 let value = match arg.position {
340 rt::ArgumentNext => { *self.curarg.next().unwrap() }
341 rt::ArgumentIs(i) => self.args[i],
344 // Then actually do some printing
345 (value.formatter)(value.value, self)
348 fn getcount(&mut self, cnt: &rt::Count) -> Option<uint> {
350 rt::CountIs(n) => Some(n),
351 rt::CountImplied => None,
352 rt::CountIsParam(i) => {
353 self.args[i].as_uint()
355 rt::CountIsNextParam => {
356 self.curarg.next().and_then(|arg| arg.as_uint())
361 // Helper methods used for padding and processing formatting arguments that
362 // all formatting traits can use.
364 /// Performs the correct padding for an integer which has already been
365 /// emitted into a byte-array. The byte-array should *not* contain the sign
366 /// for the integer, that will be added by this method.
370 /// * is_positive - whether the original integer was positive or not.
371 /// * prefix - if the '#' character (FlagAlternate) is provided, this
372 /// is the prefix to put in front of the number.
373 /// * buf - the byte array that the number has been formatted into
375 /// This function will correctly account for the flags provided as well as
376 /// the minimum width. It will not take precision into account.
377 #[unstable = "definition may change slightly over time"]
378 pub fn pad_integral(&mut self,
384 use fmt::rt::{FlagAlternate, FlagSignPlus, FlagSignAwareZeroPad};
386 let mut width = buf.len();
390 sign = Some('-'); width += 1;
391 } else if self.flags & (1 << (FlagSignPlus as uint)) != 0 {
392 sign = Some('+'); width += 1;
395 let mut prefixed = false;
396 if self.flags & (1 << (FlagAlternate as uint)) != 0 {
397 prefixed = true; width += prefix.char_len();
400 // Writes the sign if it exists, and then the prefix if it was requested
401 let write_prefix = |&: f: &mut Formatter| {
402 for c in sign.into_iter() {
404 let n = c.encode_utf8(&mut b).unwrap_or(0);
405 try!(f.buf.write(b[..n]));
407 if prefixed { f.buf.write(prefix.as_bytes()) }
411 // The `width` field is more of a `min-width` parameter at this point.
413 // If there's no minimum length requirements then we can just
416 try!(write_prefix(self)); self.buf.write(buf)
418 // Check if we're over the minimum width, if so then we can also
419 // just write the bytes.
420 Some(min) if width >= min => {
421 try!(write_prefix(self)); self.buf.write(buf)
423 // The sign and prefix goes before the padding if the fill character
425 Some(min) if self.flags & (1 << (FlagSignAwareZeroPad as uint)) != 0 => {
427 try!(write_prefix(self));
428 self.with_padding(min - width, rt::AlignRight, |f| f.buf.write(buf))
430 // Otherwise, the sign and prefix goes after the padding
432 self.with_padding(min - width, rt::AlignRight, |f| {
433 try!(write_prefix(f)); f.buf.write(buf)
439 /// This function takes a string slice and emits it to the internal buffer
440 /// after applying the relevant formatting flags specified. The flags
441 /// recognized for generic strings are:
443 /// * width - the minimum width of what to emit
444 /// * fill/align - what to emit and where to emit it if the string
445 /// provided needs to be padded
446 /// * precision - the maximum length to emit, the string is truncated if it
447 /// is longer than this length
449 /// Notably this function ignored the `flag` parameters
450 #[unstable = "definition may change slightly over time"]
451 pub fn pad(&mut self, s: &str) -> Result {
452 // Make sure there's a fast path up front
453 if self.width.is_none() && self.precision.is_none() {
454 return self.buf.write(s.as_bytes());
456 // The `precision` field can be interpreted as a `max-width` for the
457 // string being formatted
458 match self.precision {
460 // If there's a maximum width and our string is longer than
461 // that, then we must always have truncation. This is the only
462 // case where the maximum length will matter.
463 let char_len = s.char_len();
465 let nchars = ::cmp::min(max, char_len);
466 return self.buf.write(s.slice_chars(0, nchars).as_bytes());
471 // The `width` field is more of a `min-width` parameter at this point.
473 // If we're under the maximum length, and there's no minimum length
474 // requirements, then we can just emit the string
475 None => self.buf.write(s.as_bytes()),
476 // If we're under the maximum width, check if we're over the minimum
477 // width, if so it's as easy as just emitting the string.
478 Some(width) if s.char_len() >= width => {
479 self.buf.write(s.as_bytes())
481 // If we're under both the maximum and the minimum width, then fill
482 // up the minimum width with the specified string + some alignment.
484 self.with_padding(width - s.char_len(), rt::AlignLeft, |me| {
485 me.buf.write(s.as_bytes())
491 /// Runs a callback, emitting the correct padding either before or
492 /// afterwards depending on whether right or left alignment is requested.
493 fn with_padding<F>(&mut self, padding: uint, default: rt::Alignment, f: F) -> Result where
494 F: FnOnce(&mut Formatter) -> Result,
497 let align = match self.align {
498 rt::AlignUnknown => default,
502 let (pre_pad, post_pad) = match align {
503 rt::AlignLeft => (0u, padding),
504 rt::AlignRight | rt::AlignUnknown => (padding, 0u),
505 rt::AlignCenter => (padding / 2, (padding + 1) / 2),
508 let mut fill = [0u8; 4];
509 let len = self.fill.encode_utf8(&mut fill).unwrap_or(0);
511 for _ in range(0, pre_pad) {
512 try!(self.buf.write(fill[..len]));
517 for _ in range(0, post_pad) {
518 try!(self.buf.write(fill[..len]));
524 /// Writes some data to the underlying buffer contained within this
526 #[unstable = "reconciling core and I/O may alter this definition"]
527 pub fn write(&mut self, data: &[u8]) -> Result {
531 /// Writes some formatted information into this instance
532 #[unstable = "reconciling core and I/O may alter this definition"]
533 pub fn write_fmt(&mut self, fmt: Arguments) -> Result {
537 /// Flags for formatting (packed version of rt::Flag)
538 #[experimental = "return type may change and method was just created"]
539 pub fn flags(&self) -> uint { self.flags }
541 /// Character used as 'fill' whenever there is alignment
542 #[unstable = "method was just created"]
543 pub fn fill(&self) -> char { self.fill }
545 /// Flag indicating what form of alignment was requested
546 #[unstable = "method was just created"]
547 pub fn align(&self) -> rt::Alignment { self.align }
549 /// Optionally specified integer width that the output should be
550 #[unstable = "method was just created"]
551 pub fn width(&self) -> Option<uint> { self.width }
553 /// Optionally specified precision for numeric types
554 #[unstable = "method was just created"]
555 pub fn precision(&self) -> Option<uint> { self.precision }
558 impl Show for Error {
559 fn fmt(&self, f: &mut Formatter) -> Result {
560 "an error occurred when formatting an argument".fmt(f)
564 /// This is a function which calls are emitted to by the compiler itself to
565 /// create the Argument structures that are passed into the `format` function.
566 #[doc(hidden)] #[inline]
567 #[experimental = "implementation detail of the `format_args!` macro"]
568 pub fn argument<'a, T>(f: fn(&T, &mut Formatter) -> Result,
569 t: &'a T) -> Argument<'a> {
573 /// When the compiler determines that the type of an argument *must* be a uint
574 /// (such as for width and precision), then it invokes this method.
575 #[doc(hidden)] #[inline]
576 #[experimental = "implementation detail of the `format_args!` macro"]
577 pub fn argumentuint<'a>(s: &'a uint) -> Argument<'a> {
578 Argument::from_uint(s)
581 // Implementations of the core formatting traits
583 impl<'a, Sized? T: Show> Show for &'a T {
584 fn fmt(&self, f: &mut Formatter) -> Result { (**self).fmt(f) }
586 impl<'a, Sized? T: Show> Show for &'a mut T {
587 fn fmt(&self, f: &mut Formatter) -> Result { (**self).fmt(f) }
589 impl<'a> Show for &'a (Show+'a) {
590 fn fmt(&self, f: &mut Formatter) -> Result { (*self).fmt(f) }
594 fn fmt(&self, f: &mut Formatter) -> Result {
595 Show::fmt(if *self { "true" } else { "false" }, f)
600 fn fmt(&self, f: &mut Formatter) -> Result {
606 fn fmt(&self, f: &mut Formatter) -> Result {
609 let mut utf8 = [0u8; 4];
610 let amt = self.encode_utf8(&mut utf8).unwrap_or(0);
611 let s: &str = unsafe { mem::transmute(utf8[..amt]) };
616 impl<T> Pointer for *const T {
617 fn fmt(&self, f: &mut Formatter) -> Result {
618 f.flags |= 1 << (rt::FlagAlternate as uint);
619 LowerHex::fmt(&(*self as uint), f)
623 impl<T> Pointer for *mut T {
624 fn fmt(&self, f: &mut Formatter) -> Result {
625 Pointer::fmt(&(*self as *const T), f)
629 impl<'a, T> Pointer for &'a T {
630 fn fmt(&self, f: &mut Formatter) -> Result {
631 Pointer::fmt(&(*self as *const T), f)
635 impl<'a, T> Pointer for &'a mut T {
636 fn fmt(&self, f: &mut Formatter) -> Result {
637 Pointer::fmt(&(&**self as *const T), f)
641 macro_rules! floating { ($ty:ident) => {
643 fn fmt(&self, fmt: &mut Formatter) -> Result {
646 let digits = match fmt.precision {
647 Some(i) => float::DigExact(i),
648 None => float::DigMax(6),
650 float::float_to_str_bytes_common(self.abs(),
658 fmt.pad_integral(self.is_nan() || *self >= 0.0, "", bytes)
663 impl LowerExp for $ty {
664 fn fmt(&self, fmt: &mut Formatter) -> Result {
667 let digits = match fmt.precision {
668 Some(i) => float::DigExact(i),
669 None => float::DigMax(6),
671 float::float_to_str_bytes_common(self.abs(),
679 fmt.pad_integral(self.is_nan() || *self >= 0.0, "", bytes)
684 impl UpperExp for $ty {
685 fn fmt(&self, fmt: &mut Formatter) -> Result {
688 let digits = match fmt.precision {
689 Some(i) => float::DigExact(i),
690 None => float::DigMax(6),
692 float::float_to_str_bytes_common(self.abs(),
700 fmt.pad_integral(self.is_nan() || *self >= 0.0, "", bytes)
708 // Implementation of Show for various core types
710 impl<T> Show for *const T {
711 fn fmt(&self, f: &mut Formatter) -> Result { Pointer::fmt(self, f) }
714 impl<T> Show for *mut T {
715 fn fmt(&self, f: &mut Formatter) -> Result { Pointer::fmt(self, f) }
719 ($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 impl Show for Utf8Error {
800 fn fmt(&self, f: &mut Formatter) -> Result {
802 Utf8Error::InvalidByte(n) => {
803 write!(f, "invalid utf-8: invalid byte at index {}", n)
805 Utf8Error::TooShort => {
806 write!(f, "invalid utf-8: byte slice too short")
812 // If you expected tests to be here, look instead at the run-pass/ifmt.rs test,
813 // it's a lot easier than creating all of the rt::Piece structures here.