      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185
    186
    187
    188
    189
    190
    191
    192
    193
    194
    195
    196
    197
    198
    199
    200
    201
    202
    203
    204
    205
    206
    207
    208
    209
    210
    211
    212
    213
    214
    215
    216
    217
    218
    219
    220
    221
    222
    223
    224
    225
    226
    227
    228
    229
    230
    231
    232
    233
    234
    235
    236
    237
    238
    239
    240
    241
    242
    243
    244
    245
    246
    247
    248
    249
    250
    251
    252
    253
    254
    255
    256
    257
    258
    259
    260
    261
    262

    // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! Integer and floating-point number formatting

    #![allow(deprecated)]

    // FIXME: #6220 Implement floating point formatting

    use prelude::v1::*;

    use fmt;
    use num::Zero;
    use ops::{Div, Rem, Sub};
    use str;
    use slice;
    use ptr;
    use mem;

    #[doc(hidden)]
    trait Int: Zero + PartialEq + PartialOrd + Div<Output=Self> + Rem<Output=Self> +
               Sub<Output=Self> + Copy {
        fn from_u8(u: u8) -> Self;
        fn to_u8(&self) -> u8;
        fn to_u32(&self) -> u32;
        fn to_u64(&self) -> u64;
    }

    macro_rules! doit {
        ($($t:ident)*) => ($(impl Int for $t {
            fn from_u8(u: u8) -> $t { u as $t }
            fn to_u8(&self) -> u8 { *self as u8 }
            fn to_u32(&self) -> u32 { *self as u32 }
            fn to_u64(&self) -> u64 { *self as u64 }
        })*)
    }
    doit! { i8 i16 i32 i64 isize u8 u16 u32 u64 usize }

    /// A type that represents a specific radix
    #[doc(hidden)]
    trait GenericRadix {
        /// The number of digits.
        fn base(&self) -> u8;

        /// A radix-specific prefix string.
        fn prefix(&self) -> &'static str {
            ""
        }

        /// Converts an integer to corresponding radix digit.
        fn digit(&self, x: u8) -> u8;

        /// Format an integer using the radix using a formatter.
        fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter) -> fmt::Result {
            // The radix can be as low as 2, so we need a buffer of at least 64
            // characters for a base 2 number.
            let zero = T::zero();
            let is_nonnegative = x >= zero;
            let mut buf = [0; 64];
            let mut curr = buf.len();
            let base = T::from_u8(self.base());
            if is_nonnegative {
                // Accumulate each digit of the number from the least significant
                // to the most significant figure.
                for byte in buf.iter_mut().rev() {
                    let n = x % base;              // Get the current place value.
                    x = x / base;                  // Deaccumulate the number.
                    *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
                    curr -= 1;
                    if x == zero {
                        // No more digits left to accumulate.
                        break
                    };
                }
            } else {
                // Do the same as above, but accounting for two's complement.
                for byte in buf.iter_mut().rev() {
                    let n = zero - (x % base);     // Get the current place value.
                    x = x / base;                  // Deaccumulate the number.
                    *byte = self.digit(n.to_u8()); // Store the digit in the buffer.
                    curr -= 1;
                    if x == zero {
                        // No more digits left to accumulate.
                        break
                    };
                }
            }
            let buf = unsafe { str::from_utf8_unchecked(&buf[curr..]) };
            f.pad_integral(is_nonnegative, self.prefix(), buf)
        }
    }

    /// A binary (base 2) radix
    #[derive(Clone, PartialEq)]
    struct Binary;

    /// An octal (base 8) radix
    #[derive(Clone, PartialEq)]
    struct Octal;

    /// A decimal (base 10) radix
    #[derive(Clone, PartialEq)]
    struct Decimal;

    /// A hexadecimal (base 16) radix, formatted with lower-case characters
    #[derive(Clone, PartialEq)]
    struct LowerHex;

    /// A hexadecimal (base 16) radix, formatted with upper-case characters
    #[derive(Clone, PartialEq)]
    struct UpperHex;

    macro_rules! radix {
        ($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
            impl GenericRadix for $T {
                fn base(&self) -> u8 { $base }
                fn prefix(&self) -> &'static str { $prefix }
                fn digit(&self, x: u8) -> u8 {
                    match x {
                        $($x => $conv,)+
                        x => panic!("number not in the range 0..{}: {}", self.base() - 1, x),
                    }
                }
            }
        }
    }

    radix! { Binary,    2, "0b", x @  0 ...  2 => b'0' + x }
    radix! { Octal,     8, "0o", x @  0 ...  7 => b'0' + x }
    radix! { Decimal,  10, "",   x @  0 ...  9 => b'0' + x }
    radix! { LowerHex, 16, "0x", x @  0 ...  9 => b'0' + x,
                                 x @ 10 ... 15 => b'a' + (x - 10) }
    radix! { UpperHex, 16, "0x", x @  0 ...  9 => b'0' + x,
                                 x @ 10 ... 15 => b'A' + (x - 10) }

    macro_rules! int_base {
        ($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
            #[stable(feature = "rust1", since = "1.0.0")]
            impl fmt::$Trait for $T {
                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                    $Radix.fmt_int(*self as $U, f)
                }
            }
        }
    }

    macro_rules! debug {
        ($T:ident) => {
            #[stable(feature = "rust1", since = "1.0.0")]
            impl fmt::Debug for $T {
                fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                    fmt::Display::fmt(self, f)
                }
            }
        }
    }

    macro_rules! integer {
        ($Int:ident, $Uint:ident) => {
            int_base! { Binary   for $Int as $Uint  -> Binary }
            int_base! { Octal    for $Int as $Uint  -> Octal }
            int_base! { LowerHex for $Int as $Uint  -> LowerHex }
            int_base! { UpperHex for $Int as $Uint  -> UpperHex }
            debug! { $Int }

            int_base! { Binary   for $Uint as $Uint -> Binary }
            int_base! { Octal    for $Uint as $Uint -> Octal }
            int_base! { LowerHex for $Uint as $Uint -> LowerHex }
            int_base! { UpperHex for $Uint as $Uint -> UpperHex }
            debug! { $Uint }
        }
    }
    integer! { isize, usize }
    integer! { i8, u8 }
    integer! { i16, u16 }
    integer! { i32, u32 }
    integer! { i64, u64 }

    const DEC_DIGITS_LUT: &'static[u8] =
        b"0001020304050607080910111213141516171819\
          2021222324252627282930313233343536373839\
          4041424344454647484950515253545556575859\
          6061626364656667686970717273747576777879\
          8081828384858687888990919293949596979899";

    macro_rules! impl_Display {
        ($($t:ident),*: $conv_fn:ident) => ($(
        #[stable(feature = "rust1", since = "1.0.0")]
        impl fmt::Display for $t {
            #[allow(unused_comparisons)]
            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
                let is_nonnegative = *self >= 0;
                let mut n = if is_nonnegative {
                    self.$conv_fn()
                } else {
                    // convert the negative num to positive by summing 1 to it's 2 complement
                    (!self.$conv_fn()).wrapping_add(1)
                };
                let mut buf: [u8; 20] = unsafe { mem::uninitialized() };
                let mut curr = buf.len() as isize;
                let buf_ptr = buf.as_mut_ptr();
                let lut_ptr = DEC_DIGITS_LUT.as_ptr();

                unsafe {
                    // eagerly decode 4 characters at a time
                    if <$t>::max_value() as u64 >= 10000 {
                        while n >= 10000 {
                            let rem = (n % 10000) as isize;
                            n /= 10000;

                            let d1 = (rem / 100) << 1;
                            let d2 = (rem % 100) << 1;
                            curr -= 4;
                            ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
                            ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
                        }
                    }

                    // if we reach here numbers are <= 9999, so at most 4 chars long
                    let mut n = n as isize; // possibly reduce 64bit math

                    // decode 2 more chars, if > 2 chars
                    if n >= 100 {
                        let d1 = (n % 100) << 1;
                        n /= 100;
                        curr -= 2;
                        ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
                    }

                    // decode last 1 or 2 chars
                    if n < 10 {
                        curr -= 1;
                        *buf_ptr.offset(curr) = (n as u8) + 48;
                    } else {
                        let d1 = n << 1;
                        curr -= 2;
                        ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
                    }
                }

                let buf_slice = unsafe {
                    str::from_utf8_unchecked(
                        slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
                };
                f.pad_integral(is_nonnegative, "", buf_slice)
            }
        })*);
    }

    impl_Display!(i8, u8, i16, u16, i32, u32: to_u32);
    impl_Display!(i64, u64: to_u64);
    #[cfg(target_pointer_width = "32")]
    impl_Display!(isize, usize: to_u32);
    #[cfg(target_pointer_width = "64")]
    impl_Display!(isize, usize: to_u64);

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)