src/libcore/fmt/num.rs

   1 //! Integer and floating-point number formatting
   2
   3
   4 use fmt;
   5 use ops::{Div, Rem, Sub};
   6 use str;
   7 use slice;
   8 use ptr;
   9 use mem::MaybeUninit;
  10
  11 #[doc(hidden)]
  12 trait Int: PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
  13            Sub<Output=Self> + Copy {
  14     fn zero() -> Self;
  15     fn from_u8(u: u8) -> Self;
  16     fn to_u8(&self) -> u8;
  17     fn to_u16(&self) -> u16;
  18     fn to_u32(&self) -> u32;
  19     fn to_u64(&self) -> u64;
  20     fn to_u128(&self) -> u128;
  21 }
  22
  23 macro_rules! doit {
  24     ($($t:ident)*) => ($(impl Int for $t {
  25         fn zero() -> $t { 0 }
  26         fn from_u8(u: u8) -> $t { u as $t }
  27         fn to_u8(&self) -> u8 { *self as u8 }
  28         fn to_u16(&self) -> u16 { *self as u16 }
  29         fn to_u32(&self) -> u32 { *self as u32 }
  30         fn to_u64(&self) -> u64 { *self as u64 }
  31         fn to_u128(&self) -> u128 { *self as u128 }
  32     })*)
  33 }
  34 doit! { i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize }
  35
  36 /// A type that represents a specific radix
  37 #[doc(hidden)]
  38 trait GenericRadix {
  39     /// The number of digits.
  40     const BASE: u8;
  41
  42     /// A radix-specific prefix string.
  43     const PREFIX: &'static str;
  44
  45     /// Converts an integer to corresponding radix digit.
  46     fn digit(x: u8) -> u8;
  47
  48     /// Format an integer using the radix using a formatter.
  49     fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
  50         // The radix can be as low as 2, so we need a buffer of at least 128
  51         // characters for a base 2 number.
  52         let zero = T::zero();
  53         let is_nonnegative = x >= zero;
  54         let mut buf = uninitialized_array![u8; 128];
  55         let mut curr = buf.len();
  56         let base = T::from_u8(Self::BASE);
  57         if is_nonnegative {
  58             // Accumulate each digit of the number from the least significant
  59             // to the most significant figure.
  60             for byte in buf.iter_mut().rev() {
  61                 let n = x % base;               // Get the current place value.
  62                 x = x / base;                   // Deaccumulate the number.
  63                 byte.set(Self::digit(n.to_u8())); // Store the digit in the buffer.
  64                 curr -= 1;
  65                 if x == zero {
  66                     // No more digits left to accumulate.
  67                     break
  68                 };
  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.set(Self::digit(n.to_u8())); // Store the digit in the buffer.
  76                 curr -= 1;
  77                 if x == zero {
  78                     // No more digits left to accumulate.
  79                     break
  80                 };
  81             }
  82         }
  83         let buf = &buf[curr..];
  84         let buf = unsafe { str::from_utf8_unchecked(slice::from_raw_parts(
  85             MaybeUninit::first_ptr(buf),
  86             buf.len()
  87         )) };
  88         f.pad_integral(is_nonnegative, Self::PREFIX, buf)
  89     }
  90 }
  91
  92 /// A binary (base 2) radix
  93 #[derive(Clone, PartialEq)]
  94 struct Binary;
  95
  96 /// An octal (base 8) radix
  97 #[derive(Clone, PartialEq)]
  98 struct Octal;
  99
 100 /// A hexadecimal (base 16) radix, formatted with lower-case characters
 101 #[derive(Clone, PartialEq)]
 102 struct LowerHex;
 103
 104 /// A hexadecimal (base 16) radix, formatted with upper-case characters
 105 #[derive(Clone, PartialEq)]
 106 struct UpperHex;
 107
 108 macro_rules! radix {
 109     ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
 110         impl GenericRadix for $T {
 111             const BASE: u8 = $base;
 112             const PREFIX: &'static str = $prefix;
 113             fn digit(x: u8) -> u8 {
 114                 match x {
 115                     $($x => $conv,)+
 116                     x => panic!("number not in the range 0..={}: {}", Self::BASE - 1, x),
 117                 }
 118             }
 119         }
 120     }
 121 }
 122
 123 radix! { Binary,    2, "0b", x @  0 ..=  1 => b'0' + x }
 124 radix! { Octal,     8, "0o", x @  0 ..=  7 => b'0' + x }
 125 radix! { LowerHex, 16, "0x", x @  0 ..=  9 => b'0' + x,
 126                              x @ 10 ..= 15 => b'a' + (x - 10) }
 127 radix! { UpperHex, 16, "0x", x @  0 ..=  9 => b'0' + x,
 128                              x @ 10 ..= 15 => b'A' + (x - 10) }
 129
 130 macro_rules! int_base {
 131     ($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
 132         #[stable(feature = "rust1", since = "1.0.0")]
 133         impl fmt::$Trait for $T {
 134             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 135                 $Radix.fmt_int(*self as $U, f)
 136             }
 137         }
 138     }
 139 }
 140
 141 macro_rules! debug {
 142     ($T:ident) => {
 143         #[stable(feature = "rust1", since = "1.0.0")]
 144         impl fmt::Debug for $T {
 145             #[inline]
 146             fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 147                 if f.debug_lower_hex() {
 148                     fmt::LowerHex::fmt(self, f)
 149                 } else if f.debug_upper_hex() {
 150                     fmt::UpperHex::fmt(self, f)
 151                 } else {
 152                     fmt::Display::fmt(self, f)
 153                 }
 154             }
 155         }
 156     }
 157 }
 158
 159 macro_rules! integer {
 160     ($Int:ident, $Uint:ident) => {
 161         int_base! { Binary   for $Int as $Uint  -> Binary }
 162         int_base! { Octal    for $Int as $Uint  -> Octal }
 163         int_base! { LowerHex for $Int as $Uint  -> LowerHex }
 164         int_base! { UpperHex for $Int as $Uint  -> UpperHex }
 165         debug! { $Int }
 166
 167         int_base! { Binary   for $Uint as $Uint -> Binary }
 168         int_base! { Octal    for $Uint as $Uint -> Octal }
 169         int_base! { LowerHex for $Uint as $Uint -> LowerHex }
 170         int_base! { UpperHex for $Uint as $Uint -> UpperHex }
 171         debug! { $Uint }
 172     }
 173 }
 174 integer! { isize, usize }
 175 integer! { i8, u8 }
 176 integer! { i16, u16 }
 177 integer! { i32, u32 }
 178 integer! { i64, u64 }
 179 integer! { i128, u128 }
 180
 181
 182 static DEC_DIGITS_LUT: &[u8; 200] =
 183     b"0001020304050607080910111213141516171819\
 184       2021222324252627282930313233343536373839\
 185       4041424344454647484950515253545556575859\
 186       6061626364656667686970717273747576777879\
 187       8081828384858687888990919293949596979899";
 188
 189 macro_rules! impl_Display {
 190     ($($t:ident),* as $u:ident via $conv_fn:ident named $name:ident) => {
 191         fn $name(mut n: $u, is_nonnegative: bool, f: &mut fmt::Formatter) -> fmt::Result {
 192             let mut buf = uninitialized_array![u8; 39];
 193             let mut curr = buf.len() as isize;
 194             let buf_ptr = MaybeUninit::first_ptr_mut(&mut buf);
 195             let lut_ptr = DEC_DIGITS_LUT.as_ptr();
 196
 197             unsafe {
 198                 // need at least 16 bits for the 4-characters-at-a-time to work.
 199                 assert!(::mem::size_of::<$u>() >= 2);
 200
 201                 // eagerly decode 4 characters at a time
 202                 while n >= 10000 {
 203                     let rem = (n % 10000) as isize;
 204                     n /= 10000;
 205
 206                     let d1 = (rem / 100) << 1;
 207                     let d2 = (rem % 100) << 1;
 208                     curr -= 4;
 209                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 210                     ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
 211                 }
 212
 213                 // if we reach here numbers are <= 9999, so at most 4 chars long
 214                 let mut n = n as isize; // possibly reduce 64bit math
 215
 216                 // decode 2 more chars, if > 2 chars
 217                 if n >= 100 {
 218                     let d1 = (n % 100) << 1;
 219                     n /= 100;
 220                     curr -= 2;
 221                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 222                 }
 223
 224                 // decode last 1 or 2 chars
 225                 if n < 10 {
 226                     curr -= 1;
 227                     *buf_ptr.offset(curr) = (n as u8) + b'0';
 228                 } else {
 229                     let d1 = n << 1;
 230                     curr -= 2;
 231                     ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
 232                 }
 233             }
 234
 235             let buf_slice = unsafe {
 236                 str::from_utf8_unchecked(
 237                     slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
 238             };
 239             f.pad_integral(is_nonnegative, "", buf_slice)
 240         }
 241
 242         $(
 243             #[stable(feature = "rust1", since = "1.0.0")]
 244             impl fmt::Display for $t {
 245                 #[allow(unused_comparisons)]
 246                 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 247                     let is_nonnegative = *self >= 0;
 248                     let n = if is_nonnegative {
 249                         self.$conv_fn()
 250                     } else {
 251                         // convert the negative num to positive by summing 1 to it's 2 complement
 252                         (!self.$conv_fn()).wrapping_add(1)
 253                     };
 254                     $name(n, is_nonnegative, f)
 255                 }
 256             })*
 257     };
 258 }
 259
 260 // Include wasm32 in here since it doesn't reflect the native pointer size, and
 261 // often cares strongly about getting a smaller code size.
 262 #[cfg(any(target_pointer_width = "64", target_arch = "wasm32"))]
 263 mod imp {
 264     use super::*;
 265     impl_Display!(
 266         i8, u8, i16, u16, i32, u32, i64, u64, usize, isize
 267             as u64 via to_u64 named fmt_u64
 268     );
 269 }
 270
 271 #[cfg(not(any(target_pointer_width = "64", target_arch = "wasm32")))]
 272 mod imp {
 273     use super::*;
 274     impl_Display!(i8, u8, i16, u16, i32, u32, isize, usize as u32 via to_u32 named fmt_u32);
 275     impl_Display!(i64, u64 as u64 via to_u64 named fmt_u64);
 276 }
 277
 278 impl_Display!(i128, u128 as u128 via to_u128 named fmt_u128);