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use std::fmt;
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
parse::{end_dec_digits, first_byte_or_empty},
};
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct FloatLit<B: Buffer> {
number_part: B,
end_integer_part: usize,
end_fractional_part: usize,
type_suffix: Option<FloatType>,
}
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum FloatType {
F32,
F64,
}
impl<B: Buffer> FloatLit<B> {
pub fn parse(s: B) -> Result<Self, ParseError> {
match first_byte_or_empty(&s)? {
b'0'..=b'9' => Self::parse_impl(s),
_ => Err(perr(0, DoesNotStartWithDigit)),
}
}
pub fn number_part(&self) -> &str {
&self.number_part
}
pub fn integer_part(&self) -> &str {
&(*self.number_part)[..self.end_integer_part]
}
pub fn fractional_part(&self) -> Option<&str> {
if self.end_integer_part == self.end_fractional_part {
None
} else {
Some(&(*self.number_part)[self.end_integer_part + 1..self.end_fractional_part])
}
}
pub fn exponent_part(&self) -> &str {
&(*self.number_part)[self.end_fractional_part..]
}
pub fn type_suffix(&self) -> Option<FloatType> {
self.type_suffix
}
pub(crate) fn parse_impl(input: B) -> Result<Self, ParseError> {
let end_integer_part = end_dec_digits(&input);
let rest = &input[end_integer_part..];
let end_fractional_part = if rest.as_bytes().get(0) == Some(&b'.') {
if rest.as_bytes().get(1) == Some(&b'_') {
return Err(perr(end_integer_part + 1, UnexpectedChar));
}
end_dec_digits(&rest[1..]) + 1 + end_integer_part
} else {
end_integer_part
};
let rest = &input[end_fractional_part..];
if end_integer_part + 1 == end_fractional_part && !rest.is_empty() {
return Err(perr(end_integer_part + 1, UnexpectedChar));
}
let end_number_part = if rest.starts_with('e') || rest.starts_with('E') {
let exp_number_start = match rest.as_bytes().get(1) {
Some(b'-') | Some(b'+') => 2,
_ => 1,
};
let end_exponent = end_dec_digits(&rest[exp_number_start..]) + exp_number_start;
if !rest[exp_number_start..end_exponent].bytes().any(|b| matches!(b, b'0'..=b'9')) {
return Err(perr(
end_fractional_part..end_fractional_part + end_exponent,
NoExponentDigits,
));
}
end_exponent + end_fractional_part
} else {
end_fractional_part
};
let type_suffix = match &input[end_number_part..] {
"" => None,
"f32" => Some(FloatType::F32),
"f64" => Some(FloatType::F64),
_ => return Err(perr(end_number_part..input.len(), InvalidFloatTypeSuffix)),
};
Ok(Self {
number_part: input.cut(0..end_number_part),
end_integer_part,
end_fractional_part,
type_suffix,
})
}
}
impl FloatLit<&str> {
pub fn to_owned(&self) -> FloatLit<String> {
FloatLit {
number_part: self.number_part.to_owned(),
end_integer_part: self.end_integer_part,
end_fractional_part: self.end_fractional_part,
type_suffix: self.type_suffix,
}
}
}
impl<B: Buffer> fmt::Display for FloatLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let suffix = match self.type_suffix {
None => "",
Some(FloatType::F32) => "f32",
Some(FloatType::F64) => "f64",
};
write!(f, "{}{}", self.number_part(), suffix)
}
}
#[cfg(test)]
mod tests;