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 #![allow(deprecated)]
  14
  15
  16 use fmt;
  17 use ops::{Div, Rem, Sub};
  18 use str;
  19 use slice;
  20 use ptr;
  21 use mem;
  22
  23 #[doc(hidden)]
  24 trait Int: PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
  25            Sub<Output=Self> + Copy {
  26     fn zero() -> Self;
  27     fn from_u8(u: u8) -> Self;
  28     fn to_u8(&self) -> u8;
  29     fn to_u16(&self) -> u16;
  30     fn to_u32(&self) -> u32;
  31     fn to_u64(&self) -> u64;
  32     fn to_u128(&self) -> u128;
  33 }
  34
  35 macro_rules! doit {
  36     ($($t:ident)*) => ($(impl Int for $t {
  37         fn zero() -> $t { 0 }
  38         fn from_u8(u: u8) -> $t { u as $t }
  39         fn to_u8(&self) -> u8 { *self as u8 }
  40         fn to_u16(&self) -> u16 { *self as u16 }
  41         fn to_u32(&self) -> u32 { *self as u32 }
  42         fn to_u64(&self) -> u64 { *self as u64 }
  43         fn to_u128(&self) -> u128 { *self as u128 }
  44     })*)
  45 }
  46 doit! { i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize }
  47
  48 /// A type that represents a specific radix
  49 #[doc(hidden)]
  50 trait GenericRadix {
  51     /// The number of digits.
  52     fn base(&self) -> u8;
  53
  54     /// A radix-specific prefix string.
  55     fn prefix(&self) -> &'static str {
  56         ""
  57     }
  58
  59     /// Converts an integer to corresponding radix digit.
  60     fn digit(&self, x: u8) -> u8;
  61
  62     /// Format an integer using the radix using a formatter.
  63     fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
  64         // The radix can be as low as 2, so we need a buffer of at least 128
  65         // characters for a base 2 number.
  66         let zero = T::zero();
  67         let is_nonnegative = x >= zero;
  68         let mut buf = [0; 128];
  69         let mut curr = buf.len();
  70         let base = T::from_u8(self.base());
  71         if is_nonnegative {
  72             // Accumulate each digit of the number from the least significant
  73             // to the most significant figure.
  74             for byte in buf.iter_mut().rev() {
  75                 let n = x % base;              // Get the current place value.
  76                 x = x / base;                  // Deaccumulate the number.
  77                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
  78                 curr -= 1;
  79                 if x == zero {
  80                     // No more digits left to accumulate.
  81                     break
  82                 };
  83             }
  84         } else {
  85             // Do the same as above, but accounting for two's complement.
  86             for byte in buf.iter_mut().rev() {
  87                 let n = zero - (x % base);     // Get the current place value.
  88                 x = x / base;                  // Deaccumulate the number.
  89                 *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
  90                 curr -= 1;
  91                 if x == zero {
  92                     // No more digits left to accumulate.
  93                     break
  94                 };
  95             }
  96         }
  97         let buf = unsafe { str::from_utf8_unchecked(&buf[curr..]) };
  98         f.pad_integral(is_nonnegative, self.prefix(), buf)
  99     }
 100 }
 101
 102 /// A binary (base 2) radix
 103 #[derive(Clone, PartialEq)]
 104 struct Binary;
 105
 106 /// An octal (base 8) radix
 107 #[derive(Clone, PartialEq)]
 108 struct Octal;
 109
 110 /// A decimal (base 10) radix
 111 #[derive(Clone, PartialEq)]
 112 struct Decimal;
 113
 114 /// A hexadecimal (base 16) radix, formatted with lower-case characters
 115 #[derive(Clone, PartialEq)]
 116 struct LowerHex;
 117
 118 /// A hexadecimal (base 16) radix, formatted with upper-case characters
 119 #[derive(Clone, PartialEq)]
 120 struct UpperHex;
 121
 122 macro_rules! radix {
 123     ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
 124         impl GenericRadix for $T {
 125             fn base(&self) -> u8 { $base }
 126             fn prefix(&self) -> &'static str { $prefix }
 127             fn digit(&self, x: u8) -> u8 {
 128                 match x {
 129                     $($x => $conv,)+
 130                     x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
 131                 }
 132             }
 133         }
 134     }
 135 }
 136
 137 radix! { Binary,    2, "0b", x @  0 ...  2 => b'0' + x }
 138 radix! { Octal,     8, "0o", x @  0 ...  7 => b'0' + x }
 139 radix! { Decimal,  10, "",   x @  0 ...  9 => b'0' + x }
 140 radix! { LowerHex, 16, "0x", x @  0 ...  9 => b'0' + x,
 141                              x @ 10 ... 15 => b'a' + (x - 10) }
 142 radix! { UpperHex, 16, "0x", x @  0 ...  9 => b'0' + x,
 143                              x @ 10 ... 15 => b'A' + (x - 10) }
 144
 145 macro_rules! int_base {
 146     ($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
 147         #[stable(feature = "rust1", since = "1.0.0")]
 148         impl fmt::$Trait for $T {
 149             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 150                 $Radix.fmt_int(*self as $U, f)
 151             }
 152         }
 153     }
 154 }
 155
 156 macro_rules! debug {
 157     ($T:ident) => {
 158         #[stable(feature = "rust1", since = "1.0.0")]
 159         impl fmt::Debug for $T {
 160             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 161                 fmt::Display::fmt(self, f)
 162             }
 163         }
 164     }
 165 }
 166
 167 macro_rules! integer {
 168     ($Int:ident, $Uint:ident) => {
 169         int_base! { Binary   for $Int as $Uint  -> Binary }
 170         int_base! { Octal    for $Int as $Uint  -> Octal }
 171         int_base! { LowerHex for $Int as $Uint  -> LowerHex }
 172         int_base! { UpperHex for $Int as $Uint  -> UpperHex }
 173         debug! { $Int }
 174
 175         int_base! { Binary   for $Uint as $Uint -> Binary }
 176         int_base! { Octal    for $Uint as $Uint -> Octal }
 177         int_base! { LowerHex for $Uint as $Uint -> LowerHex }
 178         int_base! { UpperHex for $Uint as $Uint -> UpperHex }
 179         debug! { $Uint }
 180     }
 181 }
 182 integer! { isize, usize }
 183 integer! { i8, u8 }
 184 integer! { i16, u16 }
 185 integer! { i32, u32 }
 186 integer! { i64, u64 }
 187 integer! { i128, u128 }
 188
 189 const DEC_DIGITS_LUT: &'static[u8] =
 190     b"0001020304050607080910111213141516171819\
 191       2021222324252627282930313233343536373839\
 192       4041424344454647484950515253545556575859\
 193       6061626364656667686970717273747576777879\
 194       8081828384858687888990919293949596979899";
 195
 196 macro_rules! impl_Display {
 197     ($($t:ident),*: $conv_fn:ident) => ($(
 198     #[stable(feature = "rust1", since = "1.0.0")]
 199     impl fmt::Display for $t {
 200         #[allow(unused_comparisons)]
 201         fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 202             let is_nonnegative = *self >= 0;
 203             let mut n = if is_nonnegative {
 204                 self.$conv_fn()
 205             } else {
 206                 // convert the negative num to positive by summing 1 to it's 2 complement
 207                 (!self.$conv_fn()).wrapping_add(1)
 208             };
 209             let mut buf: [u8; 39] = unsafe { mem::uninitialized() };
 210             let mut curr = buf.len() as isize;
 211             let buf_ptr = buf.as_mut_ptr();
 212             let lut_ptr = DEC_DIGITS_LUT.as_ptr();
 213
 214             unsafe {
 215                 // need at least 16 bits for the 4-characters-at-a-time to work.
 216                 if ::mem::size_of::<$t>() >= 2 {
 217                     // eagerly decode 4 characters at a time
 218                     while n >= 10000 {
 219                         let rem = (n % 10000) as isize;
 220                         n /= 10000;
 221
 222                         let d1 = (rem / 100) << 1;
 223                         let d2 = (rem % 100) << 1;
 224                         curr -= 4;
 225                         ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 226                         ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
 227                     }
 228                 }
 229
 230                 // if we reach here numbers are <= 9999, so at most 4 chars long
 231                 let mut n = n as isize; // possibly reduce 64bit math
 232
 233                 // decode 2 more chars, if > 2 chars
 234                 if n >= 100 {
 235                     let d1 = (n % 100) << 1;
 236                     n /= 100;
 237                     curr -= 2;
 238                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 239                 }
 240
 241                 // decode last 1 or 2 chars
 242                 if n < 10 {
 243                     curr -= 1;
 244                     *buf_ptr.offset(curr) = (n as u8) + b'0';
 245                 } else {
 246                     let d1 = n << 1;
 247                     curr -= 2;
 248                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 249                 }
 250             }
 251
 252             let buf_slice = unsafe {
 253                 str::from_utf8_unchecked(
 254                     slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
 255             };
 256             f.pad_integral(is_nonnegative, "", buf_slice)
 257         }
 258     })*);
 259 }
 260
 261 impl_Display!(i8, u8, i16, u16, i32, u32: to_u32);
 262 impl_Display!(i64, u64: to_u64);
 263 impl_Display!(i128, u128: to_u128);
 264 #[cfg(target_pointer_width = "16")]
 265 impl_Display!(isize, usize: to_u16);
 266 #[cfg(target_pointer_width = "32")]
 267 impl_Display!(isize, usize: to_u32);
 268 #[cfg(target_pointer_width = "64")]
 269 impl_Display!(isize, usize: to_u64);