use crate::raw;

#[cfg(maybe_uninit)]

use core::mem::MaybeUninit;

use core::{mem, slice, str};

#[cfg(feature = "no-panic")]

use no_panic::no_panic;

const NAN: &'static str = "NaN";

const INFINITY: &'static str = "inf";

const NEG_INFINITY: &'static str = "-inf";

/// Safe API for formatting floating point numbers to text.

///

/// ## Example

///

/// ```

/// let mut buffer = ryu::Buffer::new();

/// let printed = buffer.format_finite(1.234);

/// assert_eq!(printed, "1.234");

/// ```

pub struct Buffer {

    #[cfg(maybe_uninit)]

    bytes: [MaybeUninit<u8>; 24],

    #[cfg(not(maybe_uninit))]

    bytes: [u8; 24],

}

impl Buffer {

    /// This is a cheap operation; you don't need to worry about reusing buffers

    /// for efficiency.

    #[inline]

    #[cfg_attr(feature = "no-panic", no_panic)]

    pub fn new() -> Self {

        // assume_init is safe here, since this is an array of MaybeUninit, which does not need

        // to be initialized.

        #[cfg(maybe_uninit)]

        let bytes = [MaybeUninit::<u8>::uninit(); 24];

        #[cfg(not(maybe_uninit))]

        let bytes = unsafe { mem::uninitialized() };

        Buffer { bytes: bytes }

    }

    /// Print a floating point number into this buffer and return a reference to

    /// its string representation within the buffer.

    ///

    /// # Special cases

    ///

    /// This function formats NaN as the string "NaN", positive infinity as

    /// "inf", and negative infinity as "-inf" to match std::fmt.

    ///

    /// If your input is known to be finite, you may get better performance by

    /// calling the `format_finite` method instead of `format` to avoid the

    /// checks for special cases.

    #[cfg_attr(feature = "no-panic", inline)]

    #[cfg_attr(feature = "no-panic", no_panic)]

    pub fn format<F: Float>(&mut self, f: F) -> &str {

        if f.is_nonfinite() {

            f.format_nonfinite()

        } else {

            self.format_finite(f)

        }

    }

    /// Print a floating point number into this buffer and return a reference to

    /// its string representation within the buffer.

    ///

    /// # Special cases

    ///

    /// This function **does not** check for NaN or infinity. If the input

    /// number is not a finite float, the printed representation will be some

    /// correctly formatted but unspecified numerical value.

    ///

    /// Please check [`is_finite`] yourself before calling this function, or

    /// check [`is_nan`] and [`is_infinite`] and handle those cases yourself.

    ///

    /// [`is_finite`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_finite

    /// [`is_nan`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_nan

    /// [`is_infinite`]: https://doc.rust-lang.org/std/primitive.f64.html#method.is_infinite

    #[inline]

    #[cfg_attr(feature = "no-panic", no_panic)]

    pub fn format_finite<F: Float>(&mut self, f: F) -> &str {

        unsafe {

            let n = f.write_to_ryu_buffer(self.bytes.as_mut_ptr() as *mut u8);

            debug_assert!(n <= self.bytes.len());

            let slice = slice::from_raw_parts(self.bytes.as_ptr() as *const u8, n);

            str::from_utf8_unchecked(slice)

        }

    }

Unexecuted instantiation: <ryu::buffer::Buffer>::format_finite::<_>

Unexecuted instantiation: <ryu::buffer::Buffer>::format_finite::<f64>

}

impl Copy for Buffer {}

impl Clone for Buffer {

    #[inline]

    fn clone(&self) -> Self {

        Buffer::new()

    }

}

impl Default for Buffer {

    #[inline]

    #[cfg_attr(feature = "no-panic", no_panic)]

    fn default() -> Self {

        Buffer::new()

    }

}

/// A floating point number, f32 or f64, that can be written into a

/// [`ryu::Buffer`][Buffer].

///

/// This trait is sealed and cannot be implemented for types outside of the

/// `ryu` crate.

pub trait Float: Sealed {}

impl Float for f32 {}

impl Float for f64 {}

pub trait Sealed: Copy {

    fn is_nonfinite(self) -> bool;

    fn format_nonfinite(self) -> &'static str;

    unsafe fn write_to_ryu_buffer(self, result: *mut u8) -> usize;

}

impl Sealed for f32 {

    #[inline]

    fn is_nonfinite(self) -> bool {

        const EXP_MASK: u32 = 0x7f800000;

        let bits = unsafe { mem::transmute::<f32, u32>(self) };

        bits & EXP_MASK == EXP_MASK

    }

    #[cold]

    #[cfg_attr(feature = "no-panic", inline)]

    fn format_nonfinite(self) -> &'static str {

        const MANTISSA_MASK: u32 = 0x007fffff;

        const SIGN_MASK: u32 = 0x80000000;

        let bits = unsafe { mem::transmute::<f32, u32>(self) };

        if bits & MANTISSA_MASK != 0 {

            NAN

        } else if bits & SIGN_MASK != 0 {

            NEG_INFINITY

        } else {

            INFINITY

        }

    }

    #[inline]

    unsafe fn write_to_ryu_buffer(self, result: *mut u8) -> usize {

        raw::format32(self, result)

    }

}

impl Sealed for f64 {

    #[inline]

    fn is_nonfinite(self) -> bool {

        const EXP_MASK: u64 = 0x7ff0000000000000;

        let bits = unsafe { mem::transmute::<f64, u64>(self) };

        bits & EXP_MASK == EXP_MASK

    }

    #[cold]

    #[cfg_attr(feature = "no-panic", inline)]

    fn format_nonfinite(self) -> &'static str {

        const MANTISSA_MASK: u64 = 0x000fffffffffffff;

        const SIGN_MASK: u64 = 0x8000000000000000;

        let bits = unsafe { mem::transmute::<f64, u64>(self) };

        if bits & MANTISSA_MASK != 0 {

            NAN

        } else if bits & SIGN_MASK != 0 {

            NEG_INFINITY

        } else {

            INFINITY

        }

    }

    #[inline]

    unsafe fn write_to_ryu_buffer(self, result: *mut u8) -> usize {

        raw::format64(self, result)

    }

}