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
//! Rounding-scheme identifiers.
#![allow(dead_code)]
/// Rounding type for float-parsing.
///
/// Defines the IEEE754 rounding scheme to be used during float parsing.
/// In general, this should be set to `NearestTieEven`, the default
/// recommended rounding scheme by IEEE754 for binary and decimal
/// operations.
///
/// # FFI
///
/// For interfacing with FFI-code, this may be approximated by:
/// ```text
/// const int32_t NEAREST_TIE_EVEN = 0;
/// const int32_t NEAREST_TIE_AWAY_ZERO = 1;
/// const int32_t TOWARD_POSITIVE_INFINITY = 2;
/// const int32_t TOWARD_NEGATIVE_INFINITY = 3;
/// const int32_t TOWARD_ZERO = 4;
/// ```
///
/// # Safety
///
/// Assigning any value outside the range `[1-4]` to value of type
/// RoundingKind may invoke undefined-behavior.
#[repr(i32)]
#[derive(Debug, Copy, Clone, Eq, PartialEq)]
pub enum RoundingKind {
/// Round to the nearest, tie to even.
NearestTieEven = 0,
/// Round to the nearest, tie away from zero.
NearestTieAwayZero = 1,
/// Round toward positive infinity.
TowardPositiveInfinity = 2,
/// Round toward negative infinity.
TowardNegativeInfinity = 3,
/// Round toward zero.
TowardZero = 4,
// Hide the internal implementation details, for how we implement
// TowardPositiveInfinity, TowardNegativeInfinity, and TowardZero.
/// Round to increase the magnitude of the float.
/// For example, for a negative number, this rounds to negative infinity,
/// for a positive number, to positive infinity.
#[doc(hidden)]
Upward = -1,
/// Round to decrease the magnitude of the float.
/// This always rounds toward zero.
#[doc(hidden)]
Downward = -2,
}
/// Determine if we are rounding to the nearest value, then tying away.
#[inline]
pub(crate) fn is_nearest(kind: RoundingKind) -> bool {
kind == RoundingKind::NearestTieEven || kind == RoundingKind::NearestTieAwayZero
}
/// Determine if we are rounding to the nearest value, then tying away.
#[inline]
pub(crate) fn is_toward(kind: RoundingKind) -> bool {
!is_nearest(kind)
}