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Diffstat (limited to 'third_party/rust/minimal-lexical/src/num.rs')
| -rw-r--r-- | third_party/rust/minimal-lexical/src/num.rs | 308 |
1 files changed, 308 insertions, 0 deletions
diff --git a/third_party/rust/minimal-lexical/src/num.rs b/third_party/rust/minimal-lexical/src/num.rs new file mode 100644 index 0000000000..9f682b9cbb --- /dev/null +++ b/third_party/rust/minimal-lexical/src/num.rs @@ -0,0 +1,308 @@ +//! Utilities for Rust numbers. + +#![doc(hidden)] + +#[cfg(all(not(feature = "std"), feature = "compact"))] +use crate::libm::{powd, powf}; +#[cfg(not(feature = "compact"))] +use crate::table::{SMALL_F32_POW10, SMALL_F64_POW10, SMALL_INT_POW10, SMALL_INT_POW5}; +#[cfg(not(feature = "compact"))] +use core::hint; +use core::ops; + +/// Generic floating-point type, to be used in generic code for parsing. +/// +/// Although the trait is part of the public API, the trait provides methods +/// and constants that are effectively non-public: they may be removed +/// at any time without any breaking changes. +pub trait Float: + Sized + + Copy + + PartialEq + + PartialOrd + + Send + + Sync + + ops::Add<Output = Self> + + ops::AddAssign + + ops::Div<Output = Self> + + ops::DivAssign + + ops::Mul<Output = Self> + + ops::MulAssign + + ops::Rem<Output = Self> + + ops::RemAssign + + ops::Sub<Output = Self> + + ops::SubAssign + + ops::Neg<Output = Self> +{ + /// Maximum number of digits that can contribute in the mantissa. + /// + /// We can exactly represent a float in radix `b` from radix 2 if + /// `b` is divisible by 2. This function calculates the exact number of + /// digits required to exactly represent that float. + /// + /// According to the "Handbook of Floating Point Arithmetic", + /// for IEEE754, with emin being the min exponent, p2 being the + /// precision, and b being the radix, the number of digits follows as: + /// + /// `−emin + p2 + ⌊(emin + 1) log(2, b) − log(1 − 2^(−p2), b)⌋` + /// + /// For f32, this follows as: + /// emin = -126 + /// p2 = 24 + /// + /// For f64, this follows as: + /// emin = -1022 + /// p2 = 53 + /// + /// In Python: + /// `-emin + p2 + math.floor((emin+1)*math.log(2, b) - math.log(1-2**(-p2), b))` + /// + /// This was used to calculate the maximum number of digits for [2, 36]. + const MAX_DIGITS: usize; + + // MASKS + + /// Bitmask for the sign bit. + const SIGN_MASK: u64; + /// Bitmask for the exponent, including the hidden bit. + const EXPONENT_MASK: u64; + /// Bitmask for the hidden bit in exponent, which is an implicit 1 in the fraction. + const HIDDEN_BIT_MASK: u64; + /// Bitmask for the mantissa (fraction), excluding the hidden bit. + const MANTISSA_MASK: u64; + + // PROPERTIES + + /// Size of the significand (mantissa) without hidden bit. + const MANTISSA_SIZE: i32; + /// Bias of the exponet + const EXPONENT_BIAS: i32; + /// Exponent portion of a denormal float. + const DENORMAL_EXPONENT: i32; + /// Maximum exponent value in float. + const MAX_EXPONENT: i32; + + // ROUNDING + + /// Mask to determine if a full-carry occurred (1 in bit above hidden bit). + const CARRY_MASK: u64; + + /// Bias for marking an invalid extended float. + // Value is `i16::MIN`, using hard-coded constants for older Rustc versions. + const INVALID_FP: i32 = -0x8000; + + // Maximum mantissa for the fast-path (`1 << 53` for f64). + const MAX_MANTISSA_FAST_PATH: u64 = 2_u64 << Self::MANTISSA_SIZE; + + // Largest exponent value `(1 << EXP_BITS) - 1`. + const INFINITE_POWER: i32 = Self::MAX_EXPONENT + Self::EXPONENT_BIAS; + + // Round-to-even only happens for negative values of q + // when q ≥ −4 in the 64-bit case and when q ≥ −17 in + // the 32-bitcase. + // + // When q ≥ 0,we have that 5^q ≤ 2m+1. In the 64-bit case,we + // have 5^q ≤ 2m+1 ≤ 2^54 or q ≤ 23. In the 32-bit case,we have + // 5^q ≤ 2m+1 ≤ 2^25 or q ≤ 10. + // + // When q < 0, we have w ≥ (2m+1)×5^−q. We must have that w < 2^64 + // so (2m+1)×5^−q < 2^64. We have that 2m+1 > 2^53 (64-bit case) + // or 2m+1 > 2^24 (32-bit case). Hence,we must have 2^53×5^−q < 2^64 + // (64-bit) and 2^24×5^−q < 2^64 (32-bit). Hence we have 5^−q < 2^11 + // or q ≥ −4 (64-bit case) and 5^−q < 2^40 or q ≥ −17 (32-bitcase). + // + // Thus we have that we only need to round ties to even when + // we have that q ∈ [−4,23](in the 64-bit case) or q∈[−17,10] + // (in the 32-bit case). In both cases,the power of five(5^|q|) + // fits in a 64-bit word. + const MIN_EXPONENT_ROUND_TO_EVEN: i32; + const MAX_EXPONENT_ROUND_TO_EVEN: i32; + + /// Minimum normal exponent value `-(1 << (EXPONENT_SIZE - 1)) + 1`. + const MINIMUM_EXPONENT: i32; + + /// Smallest decimal exponent for a non-zero value. + const SMALLEST_POWER_OF_TEN: i32; + + /// Largest decimal exponent for a non-infinite value. + const LARGEST_POWER_OF_TEN: i32; + + /// Minimum exponent that for a fast path case, or `-⌊(MANTISSA_SIZE+1)/log2(10)⌋` + const MIN_EXPONENT_FAST_PATH: i32; + + /// Maximum exponent that for a fast path case, or `⌊(MANTISSA_SIZE+1)/log2(5)⌋` + const MAX_EXPONENT_FAST_PATH: i32; + + /// Maximum exponent that can be represented for a disguised-fast path case. + /// This is `MAX_EXPONENT_FAST_PATH + ⌊(MANTISSA_SIZE+1)/log2(10)⌋` + const MAX_EXPONENT_DISGUISED_FAST_PATH: i32; + + /// Convert 64-bit integer to float. + fn from_u64(u: u64) -> Self; + + // Re-exported methods from std. + fn from_bits(u: u64) -> Self; + fn to_bits(self) -> u64; + + /// Get a small power-of-radix for fast-path multiplication. + /// + /// # Safety + /// + /// Safe as long as the exponent is smaller than the table size. + unsafe fn pow_fast_path(exponent: usize) -> Self; + + /// Get a small, integral power-of-radix for fast-path multiplication. + /// + /// # Safety + /// + /// Safe as long as the exponent is smaller than the table size. + #[inline(always)] + unsafe fn int_pow_fast_path(exponent: usize, radix: u32) -> u64 { + // SAFETY: safe as long as the exponent is smaller than the radix table. + #[cfg(not(feature = "compact"))] + return match radix { + 5 => unsafe { *SMALL_INT_POW5.get_unchecked(exponent) }, + 10 => unsafe { *SMALL_INT_POW10.get_unchecked(exponent) }, + _ => unsafe { hint::unreachable_unchecked() }, + }; + + #[cfg(feature = "compact")] + return (radix as u64).pow(exponent as u32); + } + + /// Returns true if the float is a denormal. + #[inline] + fn is_denormal(self) -> bool { + self.to_bits() & Self::EXPONENT_MASK == 0 + } + + /// Get exponent component from the float. + #[inline] + fn exponent(self) -> i32 { + if self.is_denormal() { + return Self::DENORMAL_EXPONENT; + } + + let bits = self.to_bits(); + let biased_e: i32 = ((bits & Self::EXPONENT_MASK) >> Self::MANTISSA_SIZE) as i32; + biased_e - Self::EXPONENT_BIAS + } + + /// Get mantissa (significand) component from float. + #[inline] + fn mantissa(self) -> u64 { + let bits = self.to_bits(); + let s = bits & Self::MANTISSA_MASK; + if !self.is_denormal() { + s + Self::HIDDEN_BIT_MASK + } else { + s + } + } +} + +impl Float for f32 { + const MAX_DIGITS: usize = 114; + const SIGN_MASK: u64 = 0x80000000; + const EXPONENT_MASK: u64 = 0x7F800000; + const HIDDEN_BIT_MASK: u64 = 0x00800000; + const MANTISSA_MASK: u64 = 0x007FFFFF; + const MANTISSA_SIZE: i32 = 23; + const EXPONENT_BIAS: i32 = 127 + Self::MANTISSA_SIZE; + const DENORMAL_EXPONENT: i32 = 1 - Self::EXPONENT_BIAS; + const MAX_EXPONENT: i32 = 0xFF - Self::EXPONENT_BIAS; + const CARRY_MASK: u64 = 0x1000000; + const MIN_EXPONENT_ROUND_TO_EVEN: i32 = -17; + const MAX_EXPONENT_ROUND_TO_EVEN: i32 = 10; + const MINIMUM_EXPONENT: i32 = -127; + const SMALLEST_POWER_OF_TEN: i32 = -65; + const LARGEST_POWER_OF_TEN: i32 = 38; + const MIN_EXPONENT_FAST_PATH: i32 = -10; + const MAX_EXPONENT_FAST_PATH: i32 = 10; + const MAX_EXPONENT_DISGUISED_FAST_PATH: i32 = 17; + + #[inline(always)] + unsafe fn pow_fast_path(exponent: usize) -> Self { + // SAFETY: safe as long as the exponent is smaller than the radix table. + #[cfg(not(feature = "compact"))] + return unsafe { *SMALL_F32_POW10.get_unchecked(exponent) }; + + #[cfg(feature = "compact")] + return powf(10.0f32, exponent as f32); + } + + #[inline] + fn from_u64(u: u64) -> f32 { + u as _ + } + + #[inline] + fn from_bits(u: u64) -> f32 { + // Constant is `u32::MAX` for older Rustc versions. + debug_assert!(u <= 0xffff_ffff); + f32::from_bits(u as u32) + } + + #[inline] + fn to_bits(self) -> u64 { + f32::to_bits(self) as u64 + } +} + +impl Float for f64 { + const MAX_DIGITS: usize = 769; + const SIGN_MASK: u64 = 0x8000000000000000; + const EXPONENT_MASK: u64 = 0x7FF0000000000000; + const HIDDEN_BIT_MASK: u64 = 0x0010000000000000; + const MANTISSA_MASK: u64 = 0x000FFFFFFFFFFFFF; + const MANTISSA_SIZE: i32 = 52; + const EXPONENT_BIAS: i32 = 1023 + Self::MANTISSA_SIZE; + const DENORMAL_EXPONENT: i32 = 1 - Self::EXPONENT_BIAS; + const MAX_EXPONENT: i32 = 0x7FF - Self::EXPONENT_BIAS; + const CARRY_MASK: u64 = 0x20000000000000; + const MIN_EXPONENT_ROUND_TO_EVEN: i32 = -4; + const MAX_EXPONENT_ROUND_TO_EVEN: i32 = 23; + const MINIMUM_EXPONENT: i32 = -1023; + const SMALLEST_POWER_OF_TEN: i32 = -342; + const LARGEST_POWER_OF_TEN: i32 = 308; + const MIN_EXPONENT_FAST_PATH: i32 = -22; + const MAX_EXPONENT_FAST_PATH: i32 = 22; + const MAX_EXPONENT_DISGUISED_FAST_PATH: i32 = 37; + + #[inline(always)] + unsafe fn pow_fast_path(exponent: usize) -> Self { + // SAFETY: safe as long as the exponent is smaller than the radix table. + #[cfg(not(feature = "compact"))] + return unsafe { *SMALL_F64_POW10.get_unchecked(exponent) }; + + #[cfg(feature = "compact")] + return powd(10.0f64, exponent as f64); + } + + #[inline] + fn from_u64(u: u64) -> f64 { + u as _ + } + + #[inline] + fn from_bits(u: u64) -> f64 { + f64::from_bits(u) + } + + #[inline] + fn to_bits(self) -> u64 { + f64::to_bits(self) + } +} + +#[inline(always)] +#[cfg(all(feature = "std", feature = "compact"))] +pub fn powf(x: f32, y: f32) -> f32 { + x.powf(y) +} + +#[inline(always)] +#[cfg(all(feature = "std", feature = "compact"))] +pub fn powd(x: f64, y: f64) -> f64 { + x.powf(y) +} |