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use rustc_ast::ast::{LitFloatType, LitIntType, LitKind};
use std::iter;
#[derive(Debug, PartialEq, Eq, Copy, Clone)]
pub enum Radix {
Binary,
Octal,
Decimal,
Hexadecimal,
}
impl Radix {
#[must_use]
fn suggest_grouping(self) -> usize {
match self {
Self::Binary | Self::Hexadecimal => 4,
Self::Octal | Self::Decimal => 3,
}
}
}
pub fn format(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
NumericLiteral::new(lit, type_suffix, float).format()
}
#[derive(Debug)]
pub struct NumericLiteral<'a> {
pub radix: Radix,
pub prefix: Option<&'a str>,
pub integer: &'a str,
pub fraction: Option<&'a str>,
pub exponent: Option<(&'a str, &'a str)>,
pub suffix: Option<&'a str>,
}
impl<'a> NumericLiteral<'a> {
pub fn from_lit_kind(src: &'a str, lit_kind: &LitKind) -> Option<NumericLiteral<'a>> {
let unsigned_src = src.strip_prefix('-').map_or(src, |s| s);
if lit_kind.is_numeric()
&& unsigned_src
.trim_start()
.chars()
.next()
.map_or(false, |c| c.is_ascii_digit())
{
let (unsuffixed, suffix) = split_suffix(src, lit_kind);
let float = matches!(lit_kind, LitKind::Float(..));
Some(NumericLiteral::new(unsuffixed, suffix, float))
} else {
None
}
}
#[must_use]
pub fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
let unsigned_lit = lit.trim_start_matches('-');
let radix = if unsigned_lit.starts_with("0x") {
Radix::Hexadecimal
} else if unsigned_lit.starts_with("0b") {
Radix::Binary
} else if unsigned_lit.starts_with("0o") {
Radix::Octal
} else {
Radix::Decimal
};
let (prefix, mut sans_prefix) = if radix == Radix::Decimal {
(None, lit)
} else {
let (p, s) = lit.split_at(2);
(Some(p), s)
};
if suffix.is_some() && sans_prefix.ends_with('_') {
sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
}
let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
Self {
radix,
prefix,
integer,
fraction,
exponent,
suffix,
}
}
pub fn is_decimal(&self) -> bool {
self.radix == Radix::Decimal
}
pub fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(&str, &str)>) {
let mut integer = digits;
let mut fraction = None;
let mut exponent = None;
if float {
for (i, c) in digits.char_indices() {
match c {
'.' => {
integer = &digits[..i];
fraction = Some(&digits[i + 1..]);
},
'e' | 'E' => {
let exp_start = if digits[..i].ends_with('_') { i - 1 } else { i };
if integer.len() > exp_start {
integer = &digits[..exp_start];
} else {
fraction = Some(&digits[integer.len() + 1..exp_start]);
};
exponent = Some((&digits[exp_start..=i], &digits[i + 1..]));
break;
},
_ => {},
}
}
}
(integer, fraction, exponent)
}
pub fn format(&self) -> String {
let mut output = String::new();
if let Some(prefix) = self.prefix {
output.push_str(prefix);
}
let group_size = self.radix.suggest_grouping();
Self::group_digits(
&mut output,
self.integer,
group_size,
true,
self.radix == Radix::Hexadecimal,
);
if let Some(fraction) = self.fraction {
output.push('.');
Self::group_digits(&mut output, fraction, group_size, false, false);
}
if let Some((separator, exponent)) = self.exponent {
if exponent != "0" {
output.push_str(separator);
Self::group_digits(&mut output, exponent, group_size, true, false);
}
}
if let Some(suffix) = self.suffix {
if output.ends_with('.') {
output.push('0');
}
output.push('_');
output.push_str(suffix);
}
output
}
pub fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
debug_assert!(group_size > 0);
let mut digits = input.chars().filter(|&c| c != '_');
if digits.clone().next() == Some('-') {
let _ = digits.next();
output.push('-');
}
let first_group_size;
if partial_group_first {
first_group_size = (digits.clone().count() - 1) % group_size + 1;
if pad {
for _ in 0..group_size - first_group_size {
output.push('0');
}
}
} else {
first_group_size = group_size;
}
for _ in 0..first_group_size {
if let Some(digit) = digits.next() {
output.push(digit);
}
}
for (c, i) in iter::zip(digits, (0..group_size).cycle()) {
if i == 0 {
output.push('_');
}
output.push(c);
}
}
}
fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
debug_assert!(lit_kind.is_numeric());
lit_suffix_length(lit_kind)
.and_then(|suffix_length| src.len().checked_sub(suffix_length))
.map_or((src, None), |split_pos| {
let (unsuffixed, suffix) = src.split_at(split_pos);
(unsuffixed, Some(suffix))
})
}
fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
debug_assert!(lit_kind.is_numeric());
let suffix = match lit_kind {
LitKind::Int(_, int_lit_kind) => match int_lit_kind {
LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
LitIntType::Unsuffixed => None,
},
LitKind::Float(_, float_lit_kind) => match float_lit_kind {
LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
LitFloatType::Unsuffixed => None,
},
_ => None,
};
suffix.map(str::len)
}