float.rs.html -- source
Description: Source to the Rust file `libcore/fmt/float.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright 2017 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.

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

    // 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: [u8; 1024] = mem::uninitialized(); // enough for f32 and f64
            let mut parts: [flt2dec::Part; 4] = mem::uninitialized();
            let formatted = flt2dec::to_exact_fixed_str(flt2dec::strategy::grisu::format_exact,
                                                        *num, sign, precision,
                                                        false, &mut buf, &mut parts);
            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: [u8; flt2dec::MAX_SIG_DIGITS] = mem::uninitialized();
            let mut parts: [flt2dec::Part; 4] = mem::uninitialized();
            let formatted = flt2dec::to_shortest_str(flt2dec::strategy::grisu::format_shortest, *num,
                                                     sign, precision, false, &mut buf, &mut parts);
            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: [u8; 1024] = mem::uninitialized(); // enough for f32 and f64
            let mut parts: [flt2dec::Part; 6] = mem::uninitialized();
            let formatted = flt2dec::to_exact_exp_str(flt2dec::strategy::grisu::format_exact,
                                                      *num, sign, precision,
                                                      upper, &mut buf, &mut parts);
            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: [u8; flt2dec::MAX_SIG_DIGITS] = mem::uninitialized();
            let mut parts: [flt2dec::Part; 6] = mem::uninitialized();
            let formatted = flt2dec::to_shortest_exp_str(flt2dec::strategy::grisu::format_shortest,
                                                         *num, sign, (0, 0), upper,
                                                         &mut buf, &mut parts);
            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 }

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