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#![deny( missing_docs, missing_copy_implementations, trivial_casts, trivial_numeric_casts, unsafe_code, unstable_features, unused_import_braces, unused_qualifications )] #![cfg_attr(not(feature = "std"), no_std)] #![cfg_attr(feature = "std", deny(missing_debug_implementations))] //! A Rust library for [IBM floating point //! numbers](https://en.wikipedia.org/wiki/IBM_hexadecimal_floating_point), specifically focused on //! converting them to IEEE-754 floating point values. //! //! See [`F32`](struct.F32.html) for 32-bit floats and [`F64`](struct.F64.html) for 64-bit floats. #[cfg(feature = "std")] use std::{cmp, fmt}; #[cfg(not(feature = "std"))] use core::cmp; mod convert; /// A 32-bit IBM floating point number. /// /// This type supports the conversions: /// /// * Transmuting to/from a `u32` via `from_bits()`, `to_bits()` /// * Transmuting to/from a big-endian `[u8; 4]` via `from_be_bytes()`/`to_be_bytes()` /// * Lossily converting to an `f32` via `From`/`Into` /// * Losslessly converting to an `f64` via `From`/`Into` /// /// IBM `F32` floats have slightly less precision than IEEE-754 `f32` floats, but it covers a /// slightly larger domain. `F32`s of typical magnitude can be converted to `f32` without rounding /// or other loss of precision. Converting `F32`s of large magnitude to `f32` will cause rounding; /// `F32`s of extreme magnitude can also cause overflow and underflow to occur. /// /// Every `F32` can be precisely represented as an `f64`, without rounding, overflow, or underflow. /// Those seeking a lossless path to IEEE-754 should convert `F32` to `f64`. /// /// ``` /// // Use the example -118.625: /// // https://en.wikipedia.org/wiki/IBM_hexadecimal_floating_point#Example /// let foreign_float = ibmfloat::F32::from_bits(0b1_1000010_0111_0110_1010_0000_0000_0000); /// /// let native_float = f32::from(foreign_float); /// assert_eq!(native_float, -118.625f32); /// /// let native_float: f32 = foreign_float.into(); /// assert_eq!(native_float, -118.625f32); /// ``` #[derive(Copy, Clone)] #[repr(transparent)] pub struct F32(u32); impl F32 { /// Transmute a native-endian `u64` into an `F64`. /// /// ``` /// let foreign_float = ibmfloat::F32::from_bits(0x46000001); /// /// let native_float = f32::from(foreign_float); // potential loss of precision /// assert_eq!(native_float, 1.0f32); /// /// let native_float = f64::from(foreign_float); // always exact /// assert_eq!(native_float, 1.0f64); /// ``` #[inline] pub fn from_bits(value: u32) -> Self { Self(value) } /// Transmute this `F32` to a native-endian `u32`. /// /// ``` /// let foreign_float = ibmfloat::F32::from_bits(0x46000001); /// /// assert_eq!(foreign_float.to_bits(), 0x46000001); /// ``` #[inline] pub fn to_bits(self) -> u32 { self.0 } /// Create a floating point value from its representation as a byte array in big endian. /// /// ``` /// let foreign_float = ibmfloat::F32::from_be_bytes([0x46, 0, 0, 1]); /// /// assert_eq!(foreign_float.to_bits(), 0x46000001); /// /// let native_float = f32::from(foreign_float); /// assert_eq!(native_float, 1.0f32); /// ``` #[inline] pub fn from_be_bytes(bytes: [u8; 4]) -> Self { Self(u32::from_be_bytes(bytes)) } /// Return the memory representation of this floating point number as a byte array in big-endian /// (network) byte order. /// /// ``` /// let foreign_float = ibmfloat::F32::from_bits(0x46000001); /// /// assert_eq!(foreign_float.to_be_bytes(), [0x46, 0, 0, 1]); /// ``` #[inline] pub fn to_be_bytes(self) -> [u8; 4] { self.0.to_be_bytes() } } /// A 64-bit IBM floating point number. /// /// This type supports the conversions: /// /// * Transmuting to/from a `u64` via `from_bits()`, `to_bits()` /// * Transmuting to/from a big-endian `[u8; 8]` via `from_be_bytes()`/`to_be_bytes()` /// * Lossily converting to an `f32` via `From`/`Into` /// * Lossily converting to an `f64` via `From`/`Into` /// /// IBM `F64` floats have slightly more precision than IEEE-754 `f64` floats, but they cover a /// slightly smaller domain. Most conversions will require rounding, but there is no risk of /// overflow or underflow. /// /// ``` /// let foreign_float = ibmfloat::F64::from_bits(0x4110000000000000); /// /// let native_float = f64::from(foreign_float); /// assert_eq!(native_float, 1.0f64); /// /// let native_float: f64 = foreign_float.into(); /// assert_eq!(native_float, 1.0f64); /// ``` #[derive(Copy, Clone)] #[repr(transparent)] pub struct F64(u64); impl F64 { /// Transmute a native-endian `u64` into an `F64`. /// /// ``` /// let foreign_float = ibmfloat::F64::from_bits(0x4110000000000000); /// /// let native_float = f64::from(foreign_float); /// assert_eq!(native_float, 1.0f64); /// ``` #[inline] pub fn from_bits(value: u64) -> Self { Self(value) } /// Transmute this `F64` to a native-endian `u64`. /// /// ``` /// let foreign_float = ibmfloat::F64::from_bits(0x4110000000000000); /// /// assert_eq!(foreign_float.to_bits(), 0x4110000000000000); /// ``` #[inline] pub fn to_bits(self) -> u64 { self.0 } /// Create a floating point value from its representation as a byte array in big endian. /// /// ``` /// let foreign_float = ibmfloat::F64::from_be_bytes([0x41, 0x10, 0, 0, 0, 0, 0, 0]); /// /// assert_eq!(foreign_float.to_bits(), 0x4110000000000000); /// /// let native_float = f64::from(foreign_float); /// assert_eq!(native_float, 1.0f64); /// ``` #[inline] pub fn from_be_bytes(bytes: [u8; 8]) -> Self { Self(u64::from_be_bytes(bytes)) } /// Return the memory representation of this floating point number as a byte array in big-endian /// (network) byte order. /// /// ``` /// let foreign_float = ibmfloat::F64::from_bits(0x4110000000000000); /// /// assert_eq!(foreign_float.to_be_bytes(), [0x41, 0x10, 0, 0, 0, 0, 0, 0]); /// ``` #[inline] pub fn to_be_bytes(self) -> [u8; 8] { self.0.to_be_bytes() } } macro_rules! float { ($t:ty) => { // Convert everything to an f64 and implement Debug, PartialEq, PartialOrd over top #[cfg(feature = "std")] impl fmt::Debug for $t { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { f64::from(*self).fmt(f) } } impl PartialEq for $t { fn eq(&self, other: &Self) -> bool { f64::from(*self).eq(&f64::from(*other)) } } impl PartialOrd for $t { fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> { f64::from(*self).partial_cmp(&f64::from(*other)) } } }; } float!(F32); float!(F64); impl From<F32> for f32 { #[inline] fn from(v: F32) -> Self { f32::from_bits(convert::ibm32ieee32(v.0)) } } impl From<F32> for f64 { #[inline] fn from(v: F32) -> Self { f64::from_bits(convert::ibm32ieee64(v.0)) } } impl From<F64> for f32 { #[inline] fn from(v: F64) -> Self { f32::from_bits(convert::ibm64ieee32(v.0)) } } impl From<F64> for f64 { #[inline] fn from(v: F64) -> Self { f64::from_bits(convert::ibm64ieee64(v.0)) } }