Merge pull request #10 from henninglive/i128
Add support for 128-bit integers
This commit is contained in:
commit
f05d2d62c3
17
.travis.yml
17
.travis.yml
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@ -1,6 +1,17 @@
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sudo: false
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language: rust
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rust:
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- nightly
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matrix:
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include:
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- rust: stable
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- rust: beta
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- rust: nightly
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env:
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- FEATURES="i128"
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- BUILD_BENCH="true"
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script:
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- cargo build --verbose --features "$FEATURES"
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- cargo test --verbose --features "$FEATURES"
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- if [ "$BUILD_BENCH" == "true" ]; then cargo bench --verbose --no-run --features "$FEATURES"; fi
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@ -9,3 +9,6 @@ documentation = "https://github.com/dtolnay/itoa"
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categories = ["value-formatting"]
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readme = "README.md"
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exclude = ["performance.png"]
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[features]
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i128 = []
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@ -41,8 +41,9 @@ fn write<W: io::Write, V: itoa::Integer>(writer: W, value: V) -> io::Result<usiz
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```
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where `itoa::Integer` is implemented for `i8`, `u8`, `i16`, `u16`, `i32`, `u32`,
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`i64`, `u64`, `isize` and `usize`. The return value gives the number of bytes
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written.
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`i64`, `u64`, `i128`, `u128`, `isize` and `usize`. 128-bit integer support is
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only available with the nightly compiler when the `i128` feature is enabled for
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this crate. The return value gives the number of bytes written.
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## Dependency
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@ -1,3 +1,4 @@
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#![cfg_attr(feature = "i128", feature(i128_type, i128))]
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#![feature(test)]
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#![allow(non_snake_case)]
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@ -5,15 +6,21 @@ extern crate itoa;
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extern crate test;
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macro_rules! benches {
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($($name:ident($value:expr),)*) => {
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(
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$(
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$(#[$attr:meta])*
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$name:ident($value:expr)
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),*
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) => {
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mod bench_itoa {
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use test::{Bencher, black_box};
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$(
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$(#[$attr])*
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#[bench]
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fn $name(b: &mut Bencher) {
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use itoa;
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let mut buf = Vec::with_capacity(20);
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let mut buf = Vec::with_capacity(40);
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b.iter(|| {
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buf.clear();
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@ -26,11 +33,12 @@ macro_rules! benches {
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mod bench_fmt {
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use test::{Bencher, black_box};
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$(
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$(#[$attr])*
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#[bench]
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fn $name(b: &mut Bencher) {
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use std::io::Write;
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let mut buf = Vec::with_capacity(20);
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let mut buf = Vec::with_capacity(40);
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b.iter(|| {
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buf.clear();
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@ -42,11 +50,16 @@ macro_rules! benches {
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}
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}
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benches!(
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bench_0u64(0u64),
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bench_HALFu64(<u32>::max_value() as u64),
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bench_MAXu64(<u64>::max_value()),
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benches!{
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bench_u64_0(0u64),
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bench_u64_half(<u32>::max_value() as u64),
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bench_u64_max(<u64>::max_value()),
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bench_0i16(0i16),
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bench_MINi16(<i16>::min_value()),
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);
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bench_i16_0(0i16),
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bench_i16_min(<i16>::min_value()),
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#[cfg(feature = "i128")]
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bench_u128_0(0u128),
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#[cfg(feature = "i128")]
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bench_u128_max(<u128>::max_value())
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}
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33
src/lib.rs
33
src/lib.rs
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@ -8,6 +8,11 @@
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#![doc(html_root_url = "https://docs.rs/itoa/0.3.3")]
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#![cfg_attr(feature = "i128", feature(i128_type, i128))]
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#[cfg(feature = "i128")]
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mod udiv128;
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use std::{io, mem, ptr, slice};
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#[inline]
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@ -30,12 +35,24 @@ const DEC_DIGITS_LUT: &'static[u8] =
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6061626364656667686970717273747576777879\
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8081828384858687888990919293949596979899";
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const MAX_LEN: usize = 20; // Tie between i64::MIN (including minus sign) and u64::MAX
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const MAX_LEN: usize = 40; // i128::MIN (including minus sign)
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// Adaptation of the original implementation at
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// https://github.com/rust-lang/rust/blob/b8214dc6c6fc20d0a660fb5700dca9ebf51ebe89/src/libcore/fmt/num.rs#L188-L266
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macro_rules! impl_Integer {
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($($t:ident),* as $conv_fn:ident) => ($(
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($($t:ident),* as $conv_fn:ident) =>
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(impl_Integer!(
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$($t),* as $conv_fn,
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(|n:$conv_fn, d:$conv_fn, rem:Option<&mut $conv_fn>| {
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match rem {
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Some(rem) => *rem = n % d,
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_ => {},
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}
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n / d
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})
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););
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($($t:ident),* as $conv_fn:ident, $divmod:expr) => ($(
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impl Integer for $t {
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fn write<W: io::Write>(self, mut wr: W) -> io::Result<usize> {
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let mut buf = unsafe { mem::uninitialized() };
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@ -63,11 +80,13 @@ macro_rules! impl_Integer {
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// eagerly decode 4 characters at a time
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if <$t>::max_value() as u64 >= 10000 {
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while n >= 10000 {
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let rem = (n % 10000) as isize;
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n /= 10000;
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let mut rem = 0;
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// division with remainder on u128 is badly optimized by LLVM.
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// see “udiv128.rs” for more info.
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n = $divmod(n, 10000, Some(&mut rem));
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let d1 = (rem / 100) << 1;
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let d2 = (rem % 100) << 1;
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let d1 = (rem as isize / 100) << 1;
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let d2 = (rem as isize % 100) << 1;
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curr -= 4;
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ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
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ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2);
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@ -115,3 +134,5 @@ impl_Integer!(isize, usize as u16);
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impl_Integer!(isize, usize as u32);
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#[cfg(target_pointer_width = "64")]
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impl_Integer!(isize, usize as u64);
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#[cfg(all(feature = "i128"))]
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impl_Integer!(i128, u128 as u128, udiv128::udivmodti4);
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@ -0,0 +1,225 @@
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// Copyright 2009-2016 compiler-builtins Developers
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//
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// The compiler-builtins crate is dual licensed under both the University of
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// Illinois "BSD-Like" license and the MIT license. As a user of this code you may
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// choose to use it under either license. As a contributor, you agree to allow
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// your code to be used under both.
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//
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// Full text of the relevant licenses is found here:
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// https://github.com/rust-lang-nursery/compiler-builtins/blob/master/LICENSE.TXT
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//
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//
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//
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// The following code is based on Rust’s [compiler-builtins crate]
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// (https://github.com/rust-lang-nursery/compiler-builtins) which
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// provides runtime functions for the Rust programs. The Rust
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// compiler will automatically link your programs against this crate.
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//
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// We copied the implementation of '__udivmodti4()' which is an intrinsic
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// implementing division with remainder for architectures without 128-bit integer support.
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// We have done this two reasons, to work around [bad optimization by LLVM]
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// (https://github.com/rust-lang/rust/issues/44545) and to allow function
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// inlining which doesn’t happen with the intrinsic.
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const BITS: u32 = 128;
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const BITS_HALF: u32 = 64;
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trait LargeInt {
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fn low(self) -> u64;
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fn high(self) -> u64;
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fn from_parts(low: u64, high: u64) -> Self;
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}
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trait Int {
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fn aborting_div(self, other: Self) -> Self;
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fn aborting_rem(self, other: Self) -> Self;
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}
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impl LargeInt for u128 {
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fn low(self) -> u64 {
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self as u64
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}
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fn high(self) -> u64 {
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(self >> 64) as u64
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}
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fn from_parts(low: u64, high: u64) -> u128 {
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low as u128 | ((high as u128) << 64)
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}
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}
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impl Int for u64 {
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fn aborting_div(self, other: u64) -> u64 {
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<u64>::checked_div(self, other).unwrap()
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}
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fn aborting_rem(self, other: u64) -> u64 {
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<u64>::checked_rem(self, other).unwrap()
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}
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}
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pub fn udivmodti4(n: u128, d: u128, rem: Option<&mut u128>) -> u128 {
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// NOTE X is unknown, K != 0
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if n.high() == 0 {
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if d.high() == 0 {
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// 0 X
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// ---
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// 0 X
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if let Some(rem) = rem {
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*rem = <u128>::from(n.low().aborting_rem(d.low()));
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}
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return <u128>::from(n.low().aborting_div(d.low()))
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} else {
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// 0 X
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// ---
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// K X
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if let Some(rem) = rem {
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*rem = n;
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}
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return 0;
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};
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}
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let mut sr;
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let mut q;
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let mut r;
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if d.low() == 0 {
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if d.high() == 0 {
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// K X
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// ---
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// 0 0
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// NOTE This should be unreachable in safe Rust because the program will panic before
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// this intrinsic is called
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unreachable!();
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}
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if n.low() == 0 {
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// K 0
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// ---
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// K 0
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if let Some(rem) = rem {
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*rem = <u128>::from_parts(0, n.high().aborting_rem(d.high()));
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}
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return <u128>::from(n.high().aborting_div(d.high()))
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}
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// K K
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// ---
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// K 0
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if d.high().is_power_of_two() {
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if let Some(rem) = rem {
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*rem = <u128>::from_parts(n.low(), n.high() & (d.high() - 1));
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}
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return <u128>::from(n.high() >> d.high().trailing_zeros());
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}
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sr = d.high().leading_zeros().wrapping_sub(n.high().leading_zeros());
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// D > N
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if sr > BITS_HALF - 2 {
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if let Some(rem) = rem {
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*rem = n;
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}
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return 0;
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}
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sr += 1;
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// 1 <= sr <= BITS_HALF - 1
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q = n << (BITS - sr);
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r = n >> sr;
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} else if d.high() == 0 {
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// K X
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// ---
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// 0 K
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if d.low().is_power_of_two() {
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if let Some(rem) = rem {
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*rem = <u128>::from(n.low() & (d.low() - 1));
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}
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if d.low() == 1 {
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return n;
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} else {
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let sr = d.low().trailing_zeros();
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return n >> sr;
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};
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}
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sr = 1 + BITS_HALF + d.low().leading_zeros() - n.high().leading_zeros();
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// 2 <= sr <= u64::BITS - 1
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q = n << (BITS - sr);
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r = n >> sr;
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} else {
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// K X
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// ---
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// K K
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sr = d.high().leading_zeros().wrapping_sub(n.high().leading_zeros());
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// D > N
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if sr > BITS_HALF - 1 {
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if let Some(rem) = rem {
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*rem = n;
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}
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return 0;
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}
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sr += 1;
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// 1 <= sr <= BITS_HALF
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q = n << (BITS - sr);
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r = n >> sr;
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}
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// Not a special case
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// q and r are initialized with
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// q = n << (u64::BITS - sr)
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// r = n >> sr
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// 1 <= sr <= u64::BITS - 1
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let mut carry = 0;
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// Don't use a range because they may generate references to memcpy in unoptimized code
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let mut i = 0;
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while i < sr {
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i += 1;
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// r:q = ((r:q) << 1) | carry
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r = (r << 1) | (q >> (BITS - 1));
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q = (q << 1) | carry as u128;
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// carry = 0
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// if r >= d {
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// r -= d;
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// carry = 1;
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// }
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let s = (d.wrapping_sub(r).wrapping_sub(1)) as i128 >> (BITS - 1);
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carry = (s & 1) as u64;
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r -= d & s as u128;
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}
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if let Some(rem) = rem {
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*rem = r;
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}
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(q << 1) | carry as u128
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}
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#[cfg(test)]
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#[test]
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fn test_udivmodti4() {
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let primes = [
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3, 7, 31, 73, 127, 179, 233, 283, 353,
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419, 467, 547, 607, 661, 739, 811, 877, 947,
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];
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for (i, d) in (0..128).cycle().zip(primes.iter().cycle()).take(1_000) {
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let n = 1u128 << i;
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let mut rem = 0;
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let q = udivmodti4(n, *d, Some(&mut rem));
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assert_eq!(q, n / d);
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assert_eq!(rem, n % d);
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}
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}
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@ -1,13 +1,20 @@
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#![cfg_attr(feature = "i128", feature(i128_type, i128))]
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#![allow(non_snake_case)]
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extern crate itoa;
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macro_rules! test {
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($($name:ident($value:expr, $expected:expr),)*) => {
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(
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$(
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$(#[$attr:meta])*
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$name:ident($value:expr, $expected:expr)
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),*
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) => {
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$(
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$(#[$attr])*
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#[test]
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fn $name() {
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let mut buf = [b'\0'; 20];
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let mut buf = [b'\0'; 40];
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let len = itoa::write(&mut buf[..], $value).unwrap();
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assert_eq!(&buf[0..len], $expected.as_bytes());
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}
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|
@ -15,12 +22,19 @@ macro_rules! test {
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}
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}
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test!(
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test_0u64(0u64, "0"),
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test_HALFu64(<u32>::max_value() as u64, "4294967295"),
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test_MAXu64(<u64>::max_value(), "18446744073709551615"),
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test_MINi64(<i64>::min_value(), "-9223372036854775808"),
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test!{
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test_u64_0(0u64, "0"),
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test_u64_half(<u32>::max_value() as u64, "4294967295"),
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test_u64_max(<u64>::max_value(), "18446744073709551615"),
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test_i64_min(<i64>::min_value(), "-9223372036854775808"),
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test_0i16(0i16, "0"),
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test_MINi16(<i16>::min_value(), "-32768"),
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);
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test_i16_0(0i16, "0"),
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test_i16_min(<i16>::min_value(), "-32768"),
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#[cfg(feature = "i128")]
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test_u128_0(0u128, "0"),
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#[cfg(feature = "i128")]
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test_u128_max(<u128>::max_value(), "340282366920938463463374607431768211455"),
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#[cfg(feature = "i128")]
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test_i128_min(<i128>::min_value(), "-170141183460469231731687303715884105728")
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}
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