diff options
Diffstat (limited to 'third_party/rust/itoa/src')
| -rw-r--r-- | third_party/rust/itoa/src/lib.rs | 290 | ||||
| -rw-r--r-- | third_party/rust/itoa/src/udiv128.rs | 48 |
2 files changed, 338 insertions, 0 deletions
diff --git a/third_party/rust/itoa/src/lib.rs b/third_party/rust/itoa/src/lib.rs new file mode 100644 index 0000000000..168407f061 --- /dev/null +++ b/third_party/rust/itoa/src/lib.rs @@ -0,0 +1,290 @@ +//! [![github]](https://github.com/dtolnay/itoa) [![crates-io]](https://crates.io/crates/itoa) [![docs-rs]](https://docs.rs/itoa) +//! +//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github +//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust +//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs +//! +//! <br> +//! +//! This crate provides a fast conversion of integer primitives to decimal +//! strings. The implementation comes straight from [libcore] but avoids the +//! performance penalty of going through [`core::fmt::Formatter`]. +//! +//! See also [`ryu`] for printing floating point primitives. +//! +//! [libcore]: https://github.com/rust-lang/rust/blob/b8214dc6c6fc20d0a660fb5700dca9ebf51ebe89/src/libcore/fmt/num.rs#L201-L254 +//! [`core::fmt::Formatter`]: https://doc.rust-lang.org/std/fmt/struct.Formatter.html +//! [`ryu`]: https://github.com/dtolnay/ryu +//! +//! # Example +//! +//! ``` +//! fn main() { +//! let mut buffer = itoa::Buffer::new(); +//! let printed = buffer.format(128u64); +//! assert_eq!(printed, "128"); +//! } +//! ``` +//! +//! # Performance (lower is better) +//! +//!  + +#![doc(html_root_url = "https://docs.rs/itoa/1.0.5")] +#![no_std] +#![allow( + clippy::cast_lossless, + clippy::cast_possible_truncation, + clippy::must_use_candidate, + clippy::unreadable_literal +)] + +mod udiv128; + +use core::mem::{self, MaybeUninit}; +use core::{ptr, slice, str}; +#[cfg(feature = "no-panic")] +use no_panic::no_panic; + +/// A correctly sized stack allocation for the formatted integer to be written +/// into. +/// +/// # Example +/// +/// ``` +/// let mut buffer = itoa::Buffer::new(); +/// let printed = buffer.format(1234); +/// assert_eq!(printed, "1234"); +/// ``` +pub struct Buffer { + bytes: [MaybeUninit<u8>; I128_MAX_LEN], +} + +impl Default for Buffer { + #[inline] + fn default() -> Buffer { + Buffer::new() + } +} + +impl Clone for Buffer { + #[inline] + fn clone(&self) -> Self { + Buffer::new() + } +} + +impl Buffer { + /// This is a cheap operation; you don't need to worry about reusing buffers + /// for efficiency. + #[inline] + #[cfg_attr(feature = "no-panic", no_panic)] + pub fn new() -> Buffer { + let bytes = [MaybeUninit::<u8>::uninit(); I128_MAX_LEN]; + Buffer { bytes } + } + + /// Print an integer into this buffer and return a reference to its string + /// representation within the buffer. + #[cfg_attr(feature = "no-panic", no_panic)] + pub fn format<I: Integer>(&mut self, i: I) -> &str { + i.write(unsafe { + &mut *(&mut self.bytes as *mut [MaybeUninit<u8>; I128_MAX_LEN] + as *mut <I as private::Sealed>::Buffer) + }) + } +} + +/// An integer that can be written into an [`itoa::Buffer`][Buffer]. +/// +/// This trait is sealed and cannot be implemented for types outside of itoa. +pub trait Integer: private::Sealed {} + +// Seal to prevent downstream implementations of the Integer trait. +mod private { + pub trait Sealed: Copy { + type Buffer: 'static; + fn write(self, buf: &mut Self::Buffer) -> &str; + } +} + +const DEC_DIGITS_LUT: &[u8] = b"\ + 0001020304050607080910111213141516171819\ + 2021222324252627282930313233343536373839\ + 4041424344454647484950515253545556575859\ + 6061626364656667686970717273747576777879\ + 8081828384858687888990919293949596979899"; + +// Adaptation of the original implementation at +// https://github.com/rust-lang/rust/blob/b8214dc6c6fc20d0a660fb5700dca9ebf51ebe89/src/libcore/fmt/num.rs#L188-L266 +macro_rules! impl_Integer { + ($($max_len:expr => $t:ident),* as $conv_fn:ident) => {$( + impl Integer for $t {} + + impl private::Sealed for $t { + type Buffer = [MaybeUninit<u8>; $max_len]; + + #[allow(unused_comparisons)] + #[inline] + #[cfg_attr(feature = "no-panic", no_panic)] + fn write(self, buf: &mut [MaybeUninit<u8>; $max_len]) -> &str { + let is_nonnegative = self >= 0; + let mut n = if is_nonnegative { + self as $conv_fn + } else { + // convert the negative num to positive by summing 1 to it's 2 complement + (!(self as $conv_fn)).wrapping_add(1) + }; + let mut curr = buf.len() as isize; + let buf_ptr = buf.as_mut_ptr() as *mut u8; + let lut_ptr = DEC_DIGITS_LUT.as_ptr(); + + unsafe { + // need at least 16 bits for the 4-characters-at-a-time to work. + if mem::size_of::<$t>() >= 2 { + // eagerly decode 4 characters at a time + while n >= 10000 { + let rem = (n % 10000) as isize; + n /= 10000; + + let d1 = (rem / 100) << 1; + let d2 = (rem % 100) << 1; + curr -= 4; + ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2); + ptr::copy_nonoverlapping(lut_ptr.offset(d2), buf_ptr.offset(curr + 2), 2); + } + } + + // if we reach here numbers are <= 9999, so at most 4 chars long + let mut n = n as isize; // possibly reduce 64bit math + + // decode 2 more chars, if > 2 chars + if n >= 100 { + let d1 = (n % 100) << 1; + n /= 100; + curr -= 2; + ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2); + } + + // decode last 1 or 2 chars + if n < 10 { + curr -= 1; + *buf_ptr.offset(curr) = (n as u8) + b'0'; + } else { + let d1 = n << 1; + curr -= 2; + ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2); + } + + if !is_nonnegative { + curr -= 1; + *buf_ptr.offset(curr) = b'-'; + } + } + + let len = buf.len() - curr as usize; + let bytes = unsafe { slice::from_raw_parts(buf_ptr.offset(curr), len) }; + unsafe { str::from_utf8_unchecked(bytes) } + } + } + )*}; +} + +const I8_MAX_LEN: usize = 4; +const U8_MAX_LEN: usize = 3; +const I16_MAX_LEN: usize = 6; +const U16_MAX_LEN: usize = 5; +const I32_MAX_LEN: usize = 11; +const U32_MAX_LEN: usize = 10; +const I64_MAX_LEN: usize = 20; +const U64_MAX_LEN: usize = 20; + +impl_Integer!( + I8_MAX_LEN => i8, + U8_MAX_LEN => u8, + I16_MAX_LEN => i16, + U16_MAX_LEN => u16, + I32_MAX_LEN => i32, + U32_MAX_LEN => u32 + as u32); + +impl_Integer!(I64_MAX_LEN => i64, U64_MAX_LEN => u64 as u64); + +#[cfg(target_pointer_width = "16")] +impl_Integer!(I16_MAX_LEN => isize, U16_MAX_LEN => usize as u16); + +#[cfg(target_pointer_width = "32")] +impl_Integer!(I32_MAX_LEN => isize, U32_MAX_LEN => usize as u32); + +#[cfg(target_pointer_width = "64")] +impl_Integer!(I64_MAX_LEN => isize, U64_MAX_LEN => usize as u64); + +macro_rules! impl_Integer128 { + ($($max_len:expr => $t:ident),*) => {$( + impl Integer for $t {} + + impl private::Sealed for $t { + type Buffer = [MaybeUninit<u8>; $max_len]; + + #[allow(unused_comparisons)] + #[inline] + #[cfg_attr(feature = "no-panic", no_panic)] + fn write(self, buf: &mut [MaybeUninit<u8>; $max_len]) -> &str { + let is_nonnegative = self >= 0; + let n = if is_nonnegative { + self as u128 + } else { + // convert the negative num to positive by summing 1 to it's 2 complement + (!(self as u128)).wrapping_add(1) + }; + let mut curr = buf.len() as isize; + let buf_ptr = buf.as_mut_ptr() as *mut u8; + + unsafe { + // Divide by 10^19 which is the highest power less than 2^64. + let (n, rem) = udiv128::udivmod_1e19(n); + let buf1 = buf_ptr.offset(curr - U64_MAX_LEN as isize) as *mut [MaybeUninit<u8>; U64_MAX_LEN]; + curr -= rem.write(&mut *buf1).len() as isize; + + if n != 0 { + // Memset the base10 leading zeros of rem. + let target = buf.len() as isize - 19; + ptr::write_bytes(buf_ptr.offset(target), b'0', (curr - target) as usize); + curr = target; + + // Divide by 10^19 again. + let (n, rem) = udiv128::udivmod_1e19(n); + let buf2 = buf_ptr.offset(curr - U64_MAX_LEN as isize) as *mut [MaybeUninit<u8>; U64_MAX_LEN]; + curr -= rem.write(&mut *buf2).len() as isize; + + if n != 0 { + // Memset the leading zeros. + let target = buf.len() as isize - 38; + ptr::write_bytes(buf_ptr.offset(target), b'0', (curr - target) as usize); + curr = target; + + // There is at most one digit left + // because u128::max / 10^19 / 10^19 is 3. + curr -= 1; + *buf_ptr.offset(curr) = (n as u8) + b'0'; + } + } + + if !is_nonnegative { + curr -= 1; + *buf_ptr.offset(curr) = b'-'; + } + + let len = buf.len() - curr as usize; + let bytes = slice::from_raw_parts(buf_ptr.offset(curr), len); + str::from_utf8_unchecked(bytes) + } + } + } + )*}; +} + +const U128_MAX_LEN: usize = 39; +const I128_MAX_LEN: usize = 40; + +impl_Integer128!(I128_MAX_LEN => i128, U128_MAX_LEN => u128); diff --git a/third_party/rust/itoa/src/udiv128.rs b/third_party/rust/itoa/src/udiv128.rs new file mode 100644 index 0000000000..0587047a77 --- /dev/null +++ b/third_party/rust/itoa/src/udiv128.rs @@ -0,0 +1,48 @@ +#[cfg(feature = "no-panic")] +use no_panic::no_panic; + +/// Multiply unsigned 128 bit integers, return upper 128 bits of the result +#[inline] +#[cfg_attr(feature = "no-panic", no_panic)] +fn u128_mulhi(x: u128, y: u128) -> u128 { + let x_lo = x as u64; + let x_hi = (x >> 64) as u64; + let y_lo = y as u64; + let y_hi = (y >> 64) as u64; + + // handle possibility of overflow + let carry = (x_lo as u128 * y_lo as u128) >> 64; + let m = x_lo as u128 * y_hi as u128 + carry; + let high1 = m >> 64; + + let m_lo = m as u64; + let high2 = (x_hi as u128 * y_lo as u128 + m_lo as u128) >> 64; + + x_hi as u128 * y_hi as u128 + high1 + high2 +} + +/// Divide `n` by 1e19 and return quotient and remainder +/// +/// Integer division algorithm is based on the following paper: +/// +/// T. Granlund and P. Montgomery, “Division by Invariant Integers Using Multiplication” +/// in Proc. of the SIGPLAN94 Conference on Programming Language Design and +/// Implementation, 1994, pp. 61–72 +/// +#[inline] +#[cfg_attr(feature = "no-panic", no_panic)] +pub fn udivmod_1e19(n: u128) -> (u128, u64) { + let d = 10_000_000_000_000_000_000_u64; // 10^19 + + let quot = if n < 1 << 83 { + ((n >> 19) as u64 / (d >> 19)) as u128 + } else { + u128_mulhi(n, 156927543384667019095894735580191660403) >> 62 + }; + + let rem = (n - quot * d as u128) as u64; + debug_assert_eq!(quot, n / d as u128); + debug_assert_eq!(rem as u128, n % d as u128); + + (quot, rem) +} |