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