      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

    use crate::fmt::{Debug, Display, Formatter, LowerExp, Result, UpperExp};
    use crate::mem::MaybeUninit;
    use crate::num::flt2dec;

    // ignore-tidy-undocumented-unsafe

    // Don't inline this so callers don't use the stack space this function
    // requires unless they have to.
    #[inline(never)]
    fn float_to_decimal_common_exact<T>(
        fmt: &mut Formatter<'_>,
        num: &T,
        sign: flt2dec::Sign,
        precision: usize,
    ) -> Result
    where
        T: flt2dec::DecodableFloat,
    {
        unsafe {
            let mut buf = MaybeUninit::<[u8; 1024]>::uninit(); // enough for f32 and f64
            let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 4]>::uninit();
            // FIXME(#53491): This is calling `get_mut` on an uninitialized
            // `MaybeUninit` (here and elsewhere in this file). Revisit this once
            // we decided whether that is valid or not.
            // We can do this only because we are libstd and coupled to the compiler.
            // (FWIW, using `freeze` would not be enough; `flt2dec::Part` is an enum!)
            let formatted = flt2dec::to_exact_fixed_str(
                flt2dec::strategy::grisu::format_exact,
                *num,
                sign,
                precision,
                false,
                buf.get_mut(),
                parts.get_mut(),
            );
            fmt.pad_formatted_parts(&formatted)
        }
    }

    // Don't inline this so callers that call both this and the above won't wind
    // up using the combined stack space of both functions in some cases.
    #[inline(never)]
    fn float_to_decimal_common_shortest<T>(
        fmt: &mut Formatter<'_>,
        num: &T,
        sign: flt2dec::Sign,
        precision: usize,
    ) -> Result
    where
        T: flt2dec::DecodableFloat,
    {
        unsafe {
            // enough for f32 and f64
            let mut buf = MaybeUninit::<[u8; flt2dec::MAX_SIG_DIGITS]>::uninit();
            let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 4]>::uninit();
            // FIXME(#53491)
            let formatted = flt2dec::to_shortest_str(
                flt2dec::strategy::grisu::format_shortest,
                *num,
                sign,
                precision,
                false,
                buf.get_mut(),
                parts.get_mut(),
            );
            fmt.pad_formatted_parts(&formatted)
        }
    }

    // Common code of floating point Debug and Display.
    fn float_to_decimal_common<T>(
        fmt: &mut Formatter<'_>,
        num: &T,
        negative_zero: bool,
        min_precision: usize,
    ) -> Result
    where
        T: flt2dec::DecodableFloat,
    {
        let force_sign = fmt.sign_plus();
        let sign = match (force_sign, negative_zero) {
            (false, false) => flt2dec::Sign::Minus,
            (false, true) => flt2dec::Sign::MinusRaw,
            (true, false) => flt2dec::Sign::MinusPlus,
            (true, true) => flt2dec::Sign::MinusPlusRaw,
        };

        if let Some(precision) = fmt.precision {
            float_to_decimal_common_exact(fmt, num, sign, precision)
        } else {
            float_to_decimal_common_shortest(fmt, num, sign, min_precision)
        }
    }

    // Don't inline this so callers don't use the stack space this function
    // requires unless they have to.
    #[inline(never)]
    fn float_to_exponential_common_exact<T>(
        fmt: &mut Formatter<'_>,
        num: &T,
        sign: flt2dec::Sign,
        precision: usize,
        upper: bool,
    ) -> Result
    where
        T: flt2dec::DecodableFloat,
    {
        unsafe {
            let mut buf = MaybeUninit::<[u8; 1024]>::uninit(); // enough for f32 and f64
            let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 6]>::uninit();
            // FIXME(#53491)
            let formatted = flt2dec::to_exact_exp_str(
                flt2dec::strategy::grisu::format_exact,
                *num,
                sign,
                precision,
                upper,
                buf.get_mut(),
                parts.get_mut(),
            );
            fmt.pad_formatted_parts(&formatted)
        }
    }

    // Don't inline this so callers that call both this and the above won't wind
    // up using the combined stack space of both functions in some cases.
    #[inline(never)]
    fn float_to_exponential_common_shortest<T>(
        fmt: &mut Formatter<'_>,
        num: &T,
        sign: flt2dec::Sign,
        upper: bool,
    ) -> Result
    where
        T: flt2dec::DecodableFloat,
    {
        unsafe {
            // enough for f32 and f64
            let mut buf = MaybeUninit::<[u8; flt2dec::MAX_SIG_DIGITS]>::uninit();
            let mut parts = MaybeUninit::<[flt2dec::Part<'_>; 6]>::uninit();
            // FIXME(#53491)
            let formatted = flt2dec::to_shortest_exp_str(
                flt2dec::strategy::grisu::format_shortest,
                *num,
                sign,
                (0, 0),
                upper,
                buf.get_mut(),
                parts.get_mut(),
            );
            fmt.pad_formatted_parts(&formatted)
        }
    }

    // Common code of floating point LowerExp and UpperExp.
    fn float_to_exponential_common<T>(fmt: &mut Formatter<'_>, num: &T, upper: bool) -> Result
    where
        T: flt2dec::DecodableFloat,
    {
        let force_sign = fmt.sign_plus();
        let sign = match force_sign {
            false => flt2dec::Sign::Minus,
            true => flt2dec::Sign::MinusPlus,
        };

        if let Some(precision) = fmt.precision {
            // 1 integral digit + `precision` fractional digits = `precision + 1` total digits
            float_to_exponential_common_exact(fmt, num, sign, precision + 1, upper)
        } else {
            float_to_exponential_common_shortest(fmt, num, sign, upper)
        }
    }

    macro_rules! floating {
        ($ty:ident) => {
            #[stable(feature = "rust1", since = "1.0.0")]
            impl Debug for $ty {
                fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
                    float_to_decimal_common(fmt, self, true, 1)
                }
            }

            #[stable(feature = "rust1", since = "1.0.0")]
            impl Display for $ty {
                fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
                    float_to_decimal_common(fmt, self, false, 0)
                }
            }

            #[stable(feature = "rust1", since = "1.0.0")]
            impl LowerExp for $ty {
                fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
                    float_to_exponential_common(fmt, self, false)
                }
            }

            #[stable(feature = "rust1", since = "1.0.0")]
            impl UpperExp for $ty {
                fn fmt(&self, fmt: &mut Formatter<'_>) -> Result {
                    float_to_exponential_common(fmt, self, true)
                }
            }
        };
    }

    floating! { f32 }
    floating! { f64 }