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// Translated from C to Rust. The original C code can be found at
//
// Copyright 2018 Ulf Adams
//
// The contents of this file may be used under the terms of the Apache License,
// Version 2.0.
//
// (See accompanying file LICENSE-Apache or copy at
//
// Alternatively, the contents of this file may be used under the terms of
// the Boost Software License, Version 1.0.
// (See accompanying file LICENSE-Boost or copy at
//
// Unless required by applicable law or agreed to in writing, this software
// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.
use crate::d2s;
pub const FLOAT_POW5_INV_BITCOUNT: i32 = d2s::DOUBLE_POW5_INV_BITCOUNT - 64;
pub const FLOAT_POW5_BITCOUNT: i32 = d2s::DOUBLE_POW5_BITCOUNT - 64;
#[cfg_attr(feature = "no-panic", inline)]
fn pow5factor_32(mut value: u32) -> u32 {
let mut count = 0u32;
loop {
debug_assert!(value != 0);
let q = value / 5;
let r = value % 5;
if r != 0 {
break;
}
value = q;
count += 1;
}
count
}
// Returns true if value is divisible by 5^p.
#[cfg_attr(feature = "no-panic", inline)]
pub fn multiple_of_power_of_5_32(value: u32, p: u32) -> bool {
pow5factor_32(value) >= p
}
// Returns true if value is divisible by 2^p.
#[cfg_attr(feature = "no-panic", inline)]
pub fn multiple_of_power_of_2_32(value: u32, p: u32) -> bool {
// __builtin_ctz doesn't appear to be faster here.
(value & ((1u32 << p) - 1)) == 0
}
// It seems to be slightly faster to avoid uint128_t here, although the
// generated code for uint128_t looks slightly nicer.
#[cfg_attr(feature = "no-panic", inline)]
fn mul_shift_32(m: u32, factor: u64, shift: i32) -> u32 {
debug_assert!(shift > 32);
// The casts here help MSVC to avoid calls to the __allmul library
// function.
let factor_lo = factor as u32;
let factor_hi = (factor >> 32) as u32;
let bits0 = m as u64 * factor_lo as u64;
let bits1 = m as u64 * factor_hi as u64;
let sum = (bits0 >> 32) + bits1;
let shifted_sum = sum >> (shift - 32);
debug_assert!(shifted_sum <= u32::max_value() as u64);
shifted_sum as u32
}
#[cfg_attr(feature = "no-panic", inline)]
pub fn mul_pow5_inv_div_pow2(m: u32, q: u32, j: i32) -> u32 {
#[cfg(feature = "small")]
{
// The inverse multipliers are defined as [2^x / 5^y] + 1; the upper 64
// bits from the double lookup table are the correct bits for [2^x /
// 5^y], so we have to add 1 here. Note that we rely on the fact that
// the added 1 that's already stored in the table never overflows into
// the upper 64 bits.
let pow5 = unsafe { d2s::compute_inv_pow5(q) };
mul_shift_32(m, pow5.1 + 1, j)
}
#[cfg(not(feature = "small"))]
{
debug_assert!(q < d2s::DOUBLE_POW5_INV_SPLIT.len() as u32);
unsafe {
mul_shift_32(
m,
d2s::DOUBLE_POW5_INV_SPLIT.get_unchecked(q as usize).1 + 1,
j,
)
}
}
}
#[cfg_attr(feature = "no-panic", inline)]
pub fn mul_pow5_div_pow2(m: u32, i: u32, j: i32) -> u32 {
#[cfg(feature = "small")]
{
let pow5 = unsafe { d2s::compute_pow5(i) };
mul_shift_32(m, pow5.1, j)
}
#[cfg(not(feature = "small"))]
{
debug_assert!(i < d2s::DOUBLE_POW5_SPLIT.len() as u32);
unsafe { mul_shift_32(m, d2s::DOUBLE_POW5_SPLIT.get_unchecked(i as usize).1, j) }
}
}