/
num.rs
440 lines (400 loc) · 15.5 KB
/
num.rs
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//! Integer and floating-point number formatting
// ignore-tidy-undocumented-unsafe
use crate::fmt;
use crate::mem::MaybeUninit;
use crate::num::flt2dec;
use crate::ops::{Div, Rem, Sub};
use crate::ptr;
use crate::slice;
use crate::str;
#[doc(hidden)]
trait Int:
PartialEq + PartialOrd + Div<Output = Self> + Rem<Output = Self> + Sub<Output = Self> + Copy
{
fn zero() -> Self;
fn from_u8(u: u8) -> Self;
fn to_u8(&self) -> u8;
fn to_u16(&self) -> u16;
fn to_u32(&self) -> u32;
fn to_u64(&self) -> u64;
fn to_u128(&self) -> u128;
}
macro_rules! doit {
($($t:ident)*) => ($(impl Int for $t {
fn zero() -> Self { 0 }
fn from_u8(u: u8) -> Self { u as Self }
fn to_u8(&self) -> u8 { *self as u8 }
fn to_u16(&self) -> u16 { *self as u16 }
fn to_u32(&self) -> u32 { *self as u32 }
fn to_u64(&self) -> u64 { *self as u64 }
fn to_u128(&self) -> u128 { *self as u128 }
})*)
}
doit! { i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize }
/// A type that represents a specific radix
#[doc(hidden)]
trait GenericRadix {
/// The number of digits.
const BASE: u8;
/// A radix-specific prefix string.
const PREFIX: &'static str;
/// Converts an integer to corresponding radix digit.
fn digit(x: u8) -> u8;
/// Format an integer using the radix using a formatter.
fn fmt_int<T: Int>(&self, mut x: T, f: &mut fmt::Formatter<'_>) -> fmt::Result {
// The radix can be as low as 2, so we need a buffer of at least 128
// characters for a base 2 number.
let zero = T::zero();
let is_nonnegative = x >= zero;
let mut buf = [MaybeUninit::<u8>::uninit(); 128];
let mut curr = buf.len();
let base = T::from_u8(Self::BASE);
if is_nonnegative {
// Accumulate each digit of the number from the least significant
// to the most significant figure.
for byte in buf.iter_mut().rev() {
let n = x % base; // Get the current place value.
x = x / base; // Deaccumulate the number.
byte.write(Self::digit(n.to_u8())); // Store the digit in the buffer.
curr -= 1;
if x == zero {
// No more digits left to accumulate.
break;
};
}
} else {
// Do the same as above, but accounting for two's complement.
for byte in buf.iter_mut().rev() {
let n = zero - (x % base); // Get the current place value.
x = x / base; // Deaccumulate the number.
byte.write(Self::digit(n.to_u8())); // Store the digit in the buffer.
curr -= 1;
if x == zero {
// No more digits left to accumulate.
break;
};
}
}
let buf = &buf[curr..];
let buf = unsafe {
str::from_utf8_unchecked(slice::from_raw_parts(MaybeUninit::first_ptr(buf), buf.len()))
};
f.pad_integral(is_nonnegative, Self::PREFIX, buf)
}
}
/// A binary (base 2) radix
#[derive(Clone, PartialEq)]
struct Binary;
/// An octal (base 8) radix
#[derive(Clone, PartialEq)]
struct Octal;
/// A hexadecimal (base 16) radix, formatted with lower-case characters
#[derive(Clone, PartialEq)]
struct LowerHex;
/// A hexadecimal (base 16) radix, formatted with upper-case characters
#[derive(Clone, PartialEq)]
struct UpperHex;
macro_rules! radix {
($T:ident, $base:expr, $prefix:expr, $($x:pat => $conv:expr),+) => {
impl GenericRadix for $T {
const BASE: u8 = $base;
const PREFIX: &'static str = $prefix;
fn digit(x: u8) -> u8 {
match x {
$($x => $conv,)+
x => panic!("number not in the range 0..={}: {}", Self::BASE - 1, x),
}
}
}
}
}
radix! { Binary, 2, "0b", x @ 0 ..= 1 => b'0' + x }
radix! { Octal, 8, "0o", x @ 0 ..= 7 => b'0' + x }
radix! { LowerHex, 16, "0x", x @ 0 ..= 9 => b'0' + x,
x @ 10 ..= 15 => b'a' + (x - 10) }
radix! { UpperHex, 16, "0x", x @ 0 ..= 9 => b'0' + x,
x @ 10 ..= 15 => b'A' + (x - 10) }
macro_rules! int_base {
($Trait:ident for $T:ident as $U:ident -> $Radix:ident) => {
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::$Trait for $T {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
$Radix.fmt_int(*self as $U, f)
}
}
};
}
macro_rules! debug {
($T:ident) => {
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Debug for $T {
#[inline]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
if f.debug_lower_hex() {
fmt::LowerHex::fmt(self, f)
} else if f.debug_upper_hex() {
fmt::UpperHex::fmt(self, f)
} else {
fmt::Display::fmt(self, f)
}
}
}
};
}
macro_rules! integer {
($Int:ident, $Uint:ident) => {
int_base! { Binary for $Int as $Uint -> Binary }
int_base! { Octal for $Int as $Uint -> Octal }
int_base! { LowerHex for $Int as $Uint -> LowerHex }
int_base! { UpperHex for $Int as $Uint -> UpperHex }
debug! { $Int }
int_base! { Binary for $Uint as $Uint -> Binary }
int_base! { Octal for $Uint as $Uint -> Octal }
int_base! { LowerHex for $Uint as $Uint -> LowerHex }
int_base! { UpperHex for $Uint as $Uint -> UpperHex }
debug! { $Uint }
};
}
integer! { isize, usize }
integer! { i8, u8 }
integer! { i16, u16 }
integer! { i32, u32 }
integer! { i64, u64 }
integer! { i128, u128 }
static DEC_DIGITS_LUT: &[u8; 200] = b"0001020304050607080910111213141516171819\
2021222324252627282930313233343536373839\
4041424344454647484950515253545556575859\
6061626364656667686970717273747576777879\
8081828384858687888990919293949596979899";
macro_rules! impl_Display {
($($t:ident),* as $u:ident via $conv_fn:ident named $name:ident) => {
fn $name(mut n: $u, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let mut buf = [MaybeUninit::<u8>::uninit(); 39];
let mut curr = buf.len() as isize;
let buf_ptr = MaybeUninit::first_ptr_mut(&mut buf);
let lut_ptr = DEC_DIGITS_LUT.as_ptr();
unsafe {
// need at least 16 bits for the 4-characters-at-a-time to work.
assert!(crate::mem::size_of::<$u>() >= 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);
}
}
let buf_slice = unsafe {
str::from_utf8_unchecked(
slice::from_raw_parts(buf_ptr.offset(curr), buf.len() - curr as usize))
};
f.pad_integral(is_nonnegative, "", buf_slice)
}
$(
#[stable(feature = "rust1", since = "1.0.0")]
impl fmt::Display for $t {
#[allow(unused_comparisons)]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let is_nonnegative = *self >= 0;
let n = if is_nonnegative {
self.$conv_fn()
} else {
// convert the negative num to positive by summing 1 to it's 2 complement
(!self.$conv_fn()).wrapping_add(1)
};
$name(n, is_nonnegative, f)
}
})*
};
}
macro_rules! impl_Exp {
($($t:ident),* as $u:ident via $conv_fn:ident named $name:ident) => {
fn $name(
mut n: $u,
is_nonnegative: bool,
upper: bool,
f: &mut fmt::Formatter<'_>
) -> fmt::Result {
let (mut n, mut exponent, trailing_zeros, added_precision) = {
let mut exponent = 0;
// count and remove trailing decimal zeroes
while n % 10 == 0 && n >= 10 {
n /= 10;
exponent += 1;
}
let trailing_zeros = exponent;
let (added_precision, subtracted_precision) = match f.precision() {
Some(fmt_prec) => {
// number of decimal digits minus 1
let mut tmp = n;
let mut prec = 0;
while tmp >= 10 {
tmp /= 10;
prec += 1;
}
(fmt_prec.saturating_sub(prec), prec.saturating_sub(fmt_prec))
}
None => (0,0)
};
for _ in 1..subtracted_precision {
n/=10;
exponent += 1;
}
if subtracted_precision != 0 {
let rem = n % 10;
n /= 10;
exponent += 1;
// round up last digit
if rem >= 5 {
n += 1;
}
}
(n, exponent, trailing_zeros, added_precision)
};
// 39 digits (worst case u128) + . = 40
let mut buf = [MaybeUninit::<u8>::uninit(); 40];
let mut curr = buf.len() as isize; //index for buf
let buf_ptr = MaybeUninit::first_ptr_mut(&mut buf);
let lut_ptr = DEC_DIGITS_LUT.as_ptr();
// decode 2 chars at a time
while n >= 100 {
let d1 = ((n % 100) as isize) << 1;
curr -= 2;
unsafe {
ptr::copy_nonoverlapping(lut_ptr.offset(d1), buf_ptr.offset(curr), 2);
}
n /= 100;
exponent += 2;
}
// n is <= 99, so at most 2 chars long
let mut n = n as isize; // possibly reduce 64bit math
// decode second-to-last character
if n >= 10 {
curr -= 1;
unsafe {
*buf_ptr.offset(curr) = (n as u8 % 10_u8) + b'0';
}
n /= 10;
exponent += 1;
}
// add decimal point iff >1 mantissa digit will be printed
if exponent != trailing_zeros || added_precision != 0 {
curr -= 1;
unsafe {
*buf_ptr.offset(curr) = b'.';
}
}
let buf_slice = unsafe {
// decode last character
curr -= 1;
*buf_ptr.offset(curr) = (n as u8) + b'0';
let len = buf.len() - curr as usize;
slice::from_raw_parts(buf_ptr.offset(curr), len)
};
// stores 'e' (or 'E') and the up to 2-digit exponent
let mut exp_buf = [MaybeUninit::<u8>::uninit(); 3];
let exp_ptr = MaybeUninit::first_ptr_mut(&mut exp_buf);
let exp_slice = unsafe {
*exp_ptr.offset(0) = if upper {b'E'} else {b'e'};
let len = if exponent < 10 {
*exp_ptr.offset(1) = (exponent as u8) + b'0';
2
} else {
let off = exponent << 1;
ptr::copy_nonoverlapping(lut_ptr.offset(off), exp_ptr.offset(1), 2);
3
};
slice::from_raw_parts(exp_ptr, len)
};
let parts = &[
flt2dec::Part::Copy(buf_slice),
flt2dec::Part::Zero(added_precision),
flt2dec::Part::Copy(exp_slice)
];
let sign = if !is_nonnegative {
"-"
} else if f.sign_plus() {
"+"
} else {
""
};
let formatted = flt2dec::Formatted{sign, parts};
f.pad_formatted_parts(&formatted)
}
$(
#[stable(feature = "integer_exp_format", since = "1.42.0")]
impl fmt::LowerExp for $t {
#[allow(unused_comparisons)]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let is_nonnegative = *self >= 0;
let n = if is_nonnegative {
self.$conv_fn()
} else {
// convert the negative num to positive by summing 1 to it's 2 complement
(!self.$conv_fn()).wrapping_add(1)
};
$name(n, is_nonnegative, false, f)
}
})*
$(
#[stable(feature = "integer_exp_format", since = "1.42.0")]
impl fmt::UpperExp for $t {
#[allow(unused_comparisons)]
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let is_nonnegative = *self >= 0;
let n = if is_nonnegative {
self.$conv_fn()
} else {
// convert the negative num to positive by summing 1 to it's 2 complement
(!self.$conv_fn()).wrapping_add(1)
};
$name(n, is_nonnegative, true, f)
}
})*
};
}
// Include wasm32 in here since it doesn't reflect the native pointer size, and
// often cares strongly about getting a smaller code size.
#[cfg(any(target_pointer_width = "64", target_arch = "wasm32"))]
mod imp {
use super::*;
impl_Display!(
i8, u8, i16, u16, i32, u32, i64, u64, usize, isize
as u64 via to_u64 named fmt_u64
);
impl_Exp!(
i8, u8, i16, u16, i32, u32, i64, u64, usize, isize
as u64 via to_u64 named exp_u64
);
}
#[cfg(not(any(target_pointer_width = "64", target_arch = "wasm32")))]
mod imp {
use super::*;
impl_Display!(i8, u8, i16, u16, i32, u32, isize, usize as u32 via to_u32 named fmt_u32);
impl_Display!(i64, u64 as u64 via to_u64 named fmt_u64);
impl_Exp!(i8, u8, i16, u16, i32, u32, isize, usize as u32 via to_u32 named exp_u32);
impl_Exp!(i64, u64 as u64 via to_u64 named exp_u64);
}
impl_Display!(i128, u128 as u128 via to_u128 named fmt_u128);
impl_Exp!(i128, u128 as u128 via to_u128 named exp_u128);