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 #![allow(unsigned_negation)]
  16
  17 use prelude::*;
  18
  19 use fmt;
  20 use num::Zero;
  21 use ops::{Div, Rem, Sub};
  22 use str;
  23
  24 #[doc(hidden)]
  25 trait Int: Zero + PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
  26            Sub<Output=Self> + Copy {
  27     fn from_u8(u: u8) -> Self;
  28     fn to_u8(&self) -> u8;
  29 }
  30
  31 macro_rules! doit {
  32     ($($t:ident)*) => ($(impl Int for $t {
  33         fn from_u8(u: u8) -> $t { u as $t }
  34         fn to_u8(&self) -> u8 { *self as u8 }
  35     })*)
  36 }
  37 doit! { i8 i16 i32 i64 isize u8 u16 u32 u64 usize }
  38
  39 /// A type that represents a specific radix
  40 #[doc(hidden)]
  41 trait GenericRadix {
  42     /// The number of digits.
  43     fn base(&self) -> u8;
  44
  45     /// A radix-specific prefix string.
  46     fn prefix(&self) -> &'static str { "" }
  47
  48     /// Converts an integer to corresponding radix digit.
  49     fn digit(&self, x: u8) -> u8;
  50
  51     /// Format an integer using the radix using a formatter.
  52     fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
  53         // The radix can be as low as 2, so we need a buffer of at least 64
  54         // characters for a base 2 number.
  55         let zero = T::zero();
  56         let is_positive = x >= zero;
  57         let mut buf = [0; 64];
  58         let mut curr = buf.len();
  59         let base = T::from_u8(self.base());
  60         if is_positive {
  61             // Accumulate each digit of the number from the least significant
  62             // to the most significant figure.
  63             for byte in buf.iter_mut().rev() {
  64                 let n = x % base;              // Get the current place value.
  65                 x = x / base;                  // Deaccumulate the number.
  66                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
  67                 curr -= 1;
  68                 if x == zero { break };        // No more digits left to accumulate.
  69             }
  70         } else {
  71             // Do the same as above, but accounting for two's complement.
  72             for byte in buf.iter_mut().rev() {
  73                 let n = zero - (x % base);     // Get the current place value.
  74                 x = x / base;                  // Deaccumulate the number.
  75                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
  76                 curr -= 1;
  77                 if x == zero { break };        // No more digits left to accumulate.
  78             }
  79         }
  80         let buf = unsafe { str::from_utf8_unchecked(&buf[curr..]) };
  81         f.pad_integral(is_positive, self.prefix(), buf)
  82     }
  83 }
  84
  85 /// A binary (base 2) radix
  86 #[derive(Clone, PartialEq)]
  87 struct Binary;
  88
  89 /// An octal (base 8) radix
  90 #[derive(Clone, PartialEq)]
  91 struct Octal;
  92
  93 /// A decimal (base 10) radix
  94 #[derive(Clone, PartialEq)]
  95 struct Decimal;
  96
  97 /// A hexadecimal (base 16) radix, formatted with lower-case characters
  98 #[derive(Clone, PartialEq)]
  99 struct LowerHex;
 100
 101 /// A hexadecimal (base 16) radix, formatted with upper-case characters
 102 #[derive(Clone, PartialEq)]
 103 struct UpperHex;
 104
 105 macro_rules! radix {
 106     ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
 107         impl GenericRadix for $T {
 108             fn base(&self) -> u8 { $base }
 109             fn prefix(&self) -> &'static str { $prefix }
 110             fn digit(&self, x: u8) -> u8 {
 111                 match x {
 112                     $($x => $conv,)+
 113                     x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
 114                 }
 115             }
 116         }
 117     }
 118 }
 119
 120 radix! { Binary,    2, "0b", x @  0 ...  2 => b'0' + x }
 121 radix! { Octal,     8, "0o", x @  0 ...  7 => b'0' + x }
 122 radix! { Decimal,  10, "",   x @  0 ...  9 => b'0' + x }
 123 radix! { LowerHex, 16, "0x", x @  0 ...  9 => b'0' + x,
 124                              x @ 10 ... 15 => b'a' + (x - 10) }
 125 radix! { UpperHex, 16, "0x", x @  0 ...  9 => b'0' + x,
 126                              x @ 10 ... 15 => b'A' + (x - 10) }
 127
 128 /// A radix with in the range of `2..36`.
 129 #[derive(Clone, Copy, PartialEq)]
 130 #[unstable(feature = "fmt_radix",
 131            reason = "may be renamed or move to a different module")]
 132 pub struct Radix {
 133     base: u8,
 134 }
 135
 136 impl Radix {
 137     fn new(base: u8) -> Radix {
 138         assert!(2 <= base && base <= 36, "the base must be in the range of 2..36: {}", base);
 139         Radix { base: base }
 140     }
 141 }
 142
 143 impl GenericRadix for Radix {
 144     fn base(&self) -> u8 { self.base }
 145     fn digit(&self, x: u8) -> u8 {
 146         match x {
 147             x @  0 ... 9 => b'0' + x,
 148             x if x < self.base() => b'a' + (x - 10),
 149             x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
 150         }
 151     }
 152 }
 153
 154 /// A helper type for formatting radixes.
 155 #[unstable(feature = "fmt_radix",
 156            reason = "may be renamed or move to a different module")]
 157 #[derive(Copy, Clone)]
 158 pub struct RadixFmt<T, R>(T, R);
 159
 160 /// Constructs a radix formatter in the range of `2..36`.
 161 ///
 162 /// # Examples
 163 ///
 164 /// ```
 165 /// # #![feature(fmt_radix)]
 166 /// use std::fmt::radix;
 167 /// assert_eq!(format!("{}", radix(55, 36)), "1j".to_string());
 168 /// ```
 169 #[unstable(feature = "fmt_radix",
 170            reason = "may be renamed or move to a different module")]
 171 pub fn radix<T>(x: T, base: u8) -> RadixFmt<T, Radix> {
 172     RadixFmt(x, Radix::new(base))
 173 }
 174
 175 macro_rules! radix_fmt {
 176     ($T:ty as $U:ty, $fmt:ident) => {
 177         #[stable(feature = "rust1", since = "1.0.0")]
 178         impl fmt::Debug for RadixFmt<$T, Radix> {
 179             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 180                 fmt::Display::fmt(self, f)
 181             }
 182         }
 183         #[stable(feature = "rust1", since = "1.0.0")]
 184         impl fmt::Display for RadixFmt<$T, Radix> {
 185             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 186                 match *self { RadixFmt(ref x, radix) => radix.$fmt(*x as $U, f) }
 187             }
 188         }
 189     }
 190 }
 191 macro_rules! int_base {
 192     ($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
 193         #[stable(feature = "rust1", since = "1.0.0")]
 194         impl fmt::$Trait for $T {
 195             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 196                 $Radix.fmt_int(*self as $U, f)
 197             }
 198         }
 199     }
 200 }
 201
 202 macro_rules! debug {
 203     ($T:ident) => {
 204         #[stable(feature = "rust1", since = "1.0.0")]
 205         impl fmt::Debug for $T {
 206             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 207                 fmt::Display::fmt(self, f)
 208             }
 209         }
 210     }
 211 }
 212 macro_rules! integer {
 213     ($Int:ident, $Uint:ident) => {
 214         int_base! { Display  for $Int as $Int   -> Decimal }
 215         int_base! { Binary   for $Int as $Uint  -> Binary }
 216         int_base! { Octal    for $Int as $Uint  -> Octal }
 217         int_base! { LowerHex for $Int as $Uint  -> LowerHex }
 218         int_base! { UpperHex for $Int as $Uint  -> UpperHex }
 219         radix_fmt! { $Int as $Int, fmt_int }
 220         debug! { $Int }
 221
 222         int_base! { Display  for $Uint as $Uint -> Decimal }
 223         int_base! { Binary   for $Uint as $Uint -> Binary }
 224         int_base! { Octal    for $Uint as $Uint -> Octal }
 225         int_base! { LowerHex for $Uint as $Uint -> LowerHex }
 226         int_base! { UpperHex for $Uint as $Uint -> UpperHex }
 227         radix_fmt! { $Uint as $Uint, fmt_int }
 228         debug! { $Uint }
 229     }
 230 }
 231 integer! { isize, usize }
 232 integer! { i8, u8 }
 233 integer! { i16, u16 }
 234 integer! { i32, u32 }
 235 integer! { i64, u64 }