src/libcore/fmt/num.rs

   1 // Copyright 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.
   4 //
   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.
  10
  11 //! Integer and floating-point number formatting
  12
  13 // FIXME: #6220 Implement floating point formatting
  14
  15 use prelude::v1::*;
  16
  17 use fmt;
  18 use num::Zero;
  19 use ops::{Div, Rem, Sub};
  20 use str;
  21 use slice;
  22 use ptr;
  23 use mem;
  24
  25 #[doc(hidden)]
  26 trait Int: Zero + PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
  27            Sub<Output=Self> + Copy {
  28     fn from_u8(u: u8) -> Self;
  29     fn to_u8(&self) -> u8;
  30     fn to_u32(&self) -> u32;
  31     fn to_u64(&self) -> u64;
  32 }
  33
  34 macro_rules! doit {
  35     ($($t:ident)*) => ($(impl Int for $t {
  36         fn from_u8(u: u8) -> $t { u as $t }
  37         fn to_u8(&self) -> u8 { *self as u8 }
  38         fn to_u32(&self) -> u32 { *self as u32 }
  39         fn to_u64(&self) -> u64 { *self as u64 }
  40     })*)
  41 }
  42 doit! { i8 i16 i32 i64 isize u8 u16 u32 u64 usize }
  43
  44 /// A type that represents a specific radix
  45 #[doc(hidden)]
  46 trait GenericRadix {
  47     /// The number of digits.
  48     fn base(&self) -> u8;
  49
  50     /// A radix-specific prefix string.
  51     fn prefix(&self) -> &'static str {
  52         ""
  53     }
  54
  55     /// Converts an integer to corresponding radix digit.
  56     fn digit(&self, x: u8) -> u8;
  57
  58     /// Format an integer using the radix using a formatter.
  59     fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
  60         // The radix can be as low as 2, so we need a buffer of at least 64
  61         // characters for a base 2 number.
  62         let zero = T::zero();
  63         let is_positive = x >= zero;
  64         let mut buf = [0; 64];
  65         let mut curr = buf.len();
  66         let base = T::from_u8(self.base());
  67         if is_positive {
  68             // Accumulate each digit of the number from the least significant
  69             // to the most significant figure.
  70             for byte in buf.iter_mut().rev() {
  71                 let n = x % base;              // Get the current place value.
  72                 x = x / base;                  // Deaccumulate the number.
  73                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
  74                 curr -= 1;
  75                 if x == zero {
  76                     // No more digits left to accumulate.
  77                     break
  78                 };
  79             }
  80         } else {
  81             // Do the same as above, but accounting for two's complement.
  82             for byte in buf.iter_mut().rev() {
  83                 let n = zero - (x % base);     // Get the current place value.
  84                 x = x / base;                  // Deaccumulate the number.
  85                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
  86                 curr -= 1;
  87                 if x == zero {
  88                     // No more digits left to accumulate.
  89                     break
  90                 };
  91             }
  92         }
  93         let buf = unsafe { str::from_utf8_unchecked(&buf[curr..]) };
  94         f.pad_integral(is_positive, self.prefix(), buf)
  95     }
  96 }
  97
  98 /// A binary (base 2) radix
  99 #[derive(Clone, PartialEq)]
 100 struct Binary;
 101
 102 /// An octal (base 8) radix
 103 #[derive(Clone, PartialEq)]
 104 struct Octal;
 105
 106 /// A decimal (base 10) radix
 107 #[derive(Clone, PartialEq)]
 108 struct Decimal;
 109
 110 /// A hexadecimal (base 16) radix, formatted with lower-case characters
 111 #[derive(Clone, PartialEq)]
 112 struct LowerHex;
 113
 114 /// A hexadecimal (base 16) radix, formatted with upper-case characters
 115 #[derive(Clone, PartialEq)]
 116 struct UpperHex;
 117
 118 macro_rules! radix {
 119     ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
 120         impl GenericRadix for $T {
 121             fn base(&self) -> u8 { $base }
 122             fn prefix(&self) -> &'static str { $prefix }
 123             fn digit(&self, x: u8) -> u8 {
 124                 match x {
 125                     $($x => $conv,)+
 126                     x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
 127                 }
 128             }
 129         }
 130     }
 131 }
 132
 133 radix! { Binary,    2, "0b", x @  0 ...  2 => b'0' + x }
 134 radix! { Octal,     8, "0o", x @  0 ...  7 => b'0' + x }
 135 radix! { Decimal,  10, "",   x @  0 ...  9 => b'0' + x }
 136 radix! { LowerHex, 16, "0x", x @  0 ...  9 => b'0' + x,
 137                              x @ 10 ... 15 => b'a' + (x - 10) }
 138 radix! { UpperHex, 16, "0x", x @  0 ...  9 => b'0' + x,
 139                              x @ 10 ... 15 => b'A' + (x - 10) }
 140
 141 /// A radix with in the range of `2..36`.
 142 #[derive(Clone, Copy, PartialEq)]
 143 #[unstable(feature = "fmt_radix",
 144            reason = "may be renamed or move to a different module",
 145            issue = "27728")]
 146 pub struct Radix {
 147     base: u8,
 148 }
 149
 150 impl Radix {
 151     fn new(base: u8) -> Radix {
 152         assert!(2 <= base && base <= 36,
 153                 "the base must be in the range of 2..36: {}",
 154                 base);
 155         Radix { base: base }
 156     }
 157 }
 158
 159 impl GenericRadix for Radix {
 160     fn base(&self) -> u8 {
 161         self.base
 162     }
 163     fn digit(&self, x: u8) -> u8 {
 164         match x {
 165             x @  0 ... 9 => b'0' + x,
 166             x if x < self.base() => b'a' + (x - 10),
 167             x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
 168         }
 169     }
 170 }
 171
 172 /// A helper type for formatting radixes.
 173 #[unstable(feature = "fmt_radix",
 174            reason = "may be renamed or move to a different module",
 175            issue = "27728")]
 176 #[derive(Copy, Clone)]
 177 pub struct RadixFmt<T, R>(T, R);
 178
 179 /// Constructs a radix formatter in the range of `2..36`.
 180 ///
 181 /// # Examples
 182 ///
 183 /// ```
 184 /// #![feature(fmt_radix)]
 185 ///
 186 /// use std::fmt::radix;
 187 /// assert_eq!(format!("{}", radix(55, 36)), "1j".to_string());
 188 /// ```
 189 #[unstable(feature = "fmt_radix",
 190            reason = "may be renamed or move to a different module",
 191            issue = "27728")]
 192 pub fn radix<T>(x: T, base: u8) -> RadixFmt<T, Radix> {
 193     RadixFmt(x, Radix::new(base))
 194 }
 195
 196 macro_rules! radix_fmt {
 197     ($T:ty as $U:ty, $fmt:ident) => {
 198         #[stable(feature = "rust1", since = "1.0.0")]
 199         impl fmt::Debug for RadixFmt<$T, Radix> {
 200             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 201                 fmt::Display::fmt(self, f)
 202             }
 203         }
 204         #[stable(feature = "rust1", since = "1.0.0")]
 205         impl fmt::Display for RadixFmt<$T, Radix> {
 206             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 207                 match *self { RadixFmt(ref x, radix) => radix.$fmt(*x as $U, f) }
 208             }
 209         }
 210     }
 211 }
 212
 213 macro_rules! int_base {
 214     ($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
 215         #[stable(feature = "rust1", since = "1.0.0")]
 216         impl fmt::$Trait for $T {
 217             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 218                 $Radix.fmt_int(*self as $U, f)
 219             }
 220         }
 221     }
 222 }
 223
 224 macro_rules! debug {
 225     ($T:ident) => {
 226         #[stable(feature = "rust1", since = "1.0.0")]
 227         impl fmt::Debug for $T {
 228             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 229                 fmt::Display::fmt(self, f)
 230             }
 231         }
 232     }
 233 }
 234
 235 macro_rules! integer {
 236     ($Int:ident, $Uint:ident) => {
 237         int_base! { Binary   for $Int as $Uint  -> Binary }
 238         int_base! { Octal    for $Int as $Uint  -> Octal }
 239         int_base! { LowerHex for $Int as $Uint  -> LowerHex }
 240         int_base! { UpperHex for $Int as $Uint  -> UpperHex }
 241         radix_fmt! { $Int as $Int, fmt_int }
 242         debug! { $Int }
 243
 244         int_base! { Binary   for $Uint as $Uint -> Binary }
 245         int_base! { Octal    for $Uint as $Uint -> Octal }
 246         int_base! { LowerHex for $Uint as $Uint -> LowerHex }
 247         int_base! { UpperHex for $Uint as $Uint -> UpperHex }
 248         radix_fmt! { $Uint as $Uint, fmt_int }
 249         debug! { $Uint }
 250     }
 251 }
 252 integer! { isize, usize }
 253 integer! { i8, u8 }
 254 integer! { i16, u16 }
 255 integer! { i32, u32 }
 256 integer! { i64, u64 }
 257
 258 const DEC_DIGITS_LUT: &'static[u8] =
 259     b"0001020304050607080910111213141516171819\
 260       2021222324252627282930313233343536373839\
 261       4041424344454647484950515253545556575859\
 262       6061626364656667686970717273747576777879\
 263       8081828384858687888990919293949596979899";
 264
 265 macro_rules! impl_Display {
 266     ($($t:ident),*: $conv_fn:ident) => ($(
 267     #[stable(feature = "rust1", since = "1.0.0")]
 268     impl fmt::Display for $t {
 269         #[allow(unused_comparisons)]
 270         fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 271             let is_positive = *self >= 0;
 272             let mut n = if is_positive {
 273                 self.$conv_fn()
 274             } else {
 275                 // convert the negative num to positive by summing 1 to it's 2 complement
 276                 (!self.$conv_fn()).wrapping_add(1)
 277             };
 278             let mut buf: [u8; 20] = unsafe { mem::uninitialized() };
 279             let mut curr = buf.len() as isize;
 280             let buf_ptr = buf.as_mut_ptr();
 281             let lut_ptr = DEC_DIGITS_LUT.as_ptr();
 282
 283             unsafe {
 284                 // eagerly decode 4 characters at a time
 285                 if <$t>::max_value() as u64 >= 10000 {
 286                     while n >= 10000 {
 287                         let rem = (n % 10000) as isize;
 288                         n /= 10000;
 289
 290                         let d1 = (rem / 100) << 1;
 291                         let d2 = (rem % 100) << 1;
 292                         curr -= 4;
 293                         ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 294                         ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
 295                     }
 296                 }
 297
 298                 // if we reach here numbers are <= 9999, so at most 4 chars long
 299                 let mut n = n as isize; // possibly reduce 64bit math
 300
 301                 // decode 2 more chars, if > 2 chars
 302                 if n >= 100 {
 303                     let d1 = (n % 100) << 1;
 304                     n /= 100;
 305                     curr -= 2;
 306                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 307                 }
 308
 309                 // decode last 1 or 2 chars
 310                 if n < 10 {
 311                     curr -= 1;
 312                     *buf_ptr.offset(curr) = (n as u8) + 48;
 313                 } else {
 314                     let d1 = n << 1;
 315                     curr -= 2;
 316                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 317                 }
 318             }
 319
 320             let buf_slice = unsafe {
 321                 str::from_utf8_unchecked(
 322                     slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
 323             };
 324             f.pad_integral(is_positive, "", buf_slice)
 325         }
 326     })*);
 327 }
 328
 329 impl_Display!(i8, u8, i16, u16, i32, u32: to_u32);
 330 impl_Display!(i64, u64: to_u64);
 331 #[cfg(target_pointer_width = "32")]
 332 impl_Display!(isize, usize: to_u32);
 333 #[cfg(target_pointer_width = "64")]
 334 impl_Display!(isize, usize: to_u64);