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use std::{fmt, str::FromStr};
use crate::{
Buffer, ParseError,
err::{perr, ParseErrorKind::*},
parse::{first_byte_or_empty, hex_digit_value, check_suffix},
};
/// An integer literal, e.g. `27`, `0x7F`, `0b101010u8` or `5_000_000i64`.
///
/// An integer literal consists of an optional base prefix (`0b`, `0o`, `0x`),
/// the main part (digits and underscores), and an optional type suffix
/// (e.g. `u64` or `i8`). See [the reference][ref] for more information.
///
/// Note that integer literals are always positive: the grammar does not contain
/// the minus sign at all. The minus sign is just the unary negate operator,
/// not part of the literal. Which is interesting for cases like `- 128i8`:
/// here, the literal itself would overflow the specified type (`i8` cannot
/// represent 128). That's why in rustc, the literal overflow check is
/// performed as a lint after parsing, not during the lexing stage. Similarly,
/// [`IntegerLit::parse`] does not perform an overflow check.
///
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[non_exhaustive]
pub struct IntegerLit<B: Buffer> {
/// The raw literal. Grammar: `<prefix?><main part><suffix?>`.
raw: B,
/// First index of the main number part (after the base prefix).
start_main_part: usize,
/// First index not part of the main number part.
end_main_part: usize,
/// Parsed `raw[..start_main_part]`.
base: IntegerBase,
}
impl<B: Buffer> IntegerLit<B> {
/// Parses the input as an integer literal. Returns an error if the input is
/// invalid or represents a different kind of literal.
pub fn parse(input: B) -> Result<Self, ParseError> {
match first_byte_or_empty(&input)? {
digit @ b'0'..=b'9' => {
// TODO: simplify once RFC 2528 is stabilized
let IntegerLit {
start_main_part,
end_main_part,
base,
..
} = parse_impl(&input, digit)?;
Ok(Self { raw: input, start_main_part, end_main_part, base })
},
_ => Err(perr(0, DoesNotStartWithDigit)),
}
}
/// Performs the actual string to int conversion to obtain the integer
/// value. The optional type suffix of the literal **is ignored by this
/// method**. This means `N` does not need to match the type suffix!
///
/// Returns `None` if the literal overflows `N`.
///
/// Hint: `u128` can represent all possible values integer literal values,
/// as there are no negative literals (see type docs). Thus you can, for
/// example, safely use `lit.value::<u128>().to_string()` to get a decimal
/// string. (Technically, Rust integer literals can represent arbitrarily
/// large numbers, but those would be rejected at a later stage by the Rust
/// compiler).
pub fn value<N: FromIntegerLiteral>(&self) -> Option<N> {
let base = N::from_small_number(self.base.value());
let mut acc = N::from_small_number(0);
for digit in self.raw_main_part().bytes() {
if digit == b'_' {
continue;
}
// We don't actually need the base here: we already know this main
// part only contains digits valid for the specified base.
let digit = hex_digit_value(digit)
.unwrap_or_else(|| unreachable!("bug: integer main part contains non-digit"));
acc = acc.checked_mul(base)?;
acc = acc.checked_add(N::from_small_number(digit))?;
}
Some(acc)
}
/// The base of this integer literal.
pub fn base(&self) -> IntegerBase {
self.base
}
/// The main part containing the digits and potentially `_`. Do not try to
/// parse this directly as that would ignore the base!
pub fn raw_main_part(&self) -> &str {
&(*self.raw)[self.start_main_part..self.end_main_part]
}
/// The optional suffix. Returns `""` if the suffix is empty/does not exist.
///
/// If you want the type, try `IntegerType::from_suffix(lit.suffix())`.
pub fn suffix(&self) -> &str {
&(*self.raw)[self.end_main_part..]
}
/// Returns the raw input that was passed to `parse`.
pub fn raw_input(&self) -> &str {
&self.raw
}
/// Returns the raw input that was passed to `parse`, potentially owned.
pub fn into_raw_input(self) -> B {
self.raw
}
}
impl IntegerLit<&str> {
/// Makes a copy of the underlying buffer and returns the owned version of
/// `Self`.
pub fn to_owned(&self) -> IntegerLit<String> {
IntegerLit {
raw: self.raw.to_owned(),
start_main_part: self.start_main_part,
end_main_part: self.end_main_part,
base: self.base,
}
}
}
impl<B: Buffer> fmt::Display for IntegerLit<B> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}", &*self.raw)
}
}
/// Integer literal types. *Implementation detail*.
///
/// Implemented for all integer literal types. This trait is sealed and cannot
/// be implemented outside of this crate. The trait's methods are implementation
/// detail of this library and are not subject to semver.
pub trait FromIntegerLiteral: self::sealed::Sealed + Copy {
/// Creates itself from the given number. `n` is guaranteed to be `<= 16`.
#[doc(hidden)]
fn from_small_number(n: u8) -> Self;
#[doc(hidden)]
fn checked_add(self, rhs: Self) -> Option<Self>;
#[doc(hidden)]
fn checked_mul(self, rhs: Self) -> Option<Self>;
#[doc(hidden)]
fn ty() -> IntegerType;
}
macro_rules! impl_from_int_literal {
($( $ty:ty => $variant:ident ,)* ) => {
$(
impl self::sealed::Sealed for $ty {}
impl FromIntegerLiteral for $ty {
fn from_small_number(n: u8) -> Self {
n as Self
}
fn checked_add(self, rhs: Self) -> Option<Self> {
self.checked_add(rhs)
}
fn checked_mul(self, rhs: Self) -> Option<Self> {
self.checked_mul(rhs)
}
fn ty() -> IntegerType {
IntegerType::$variant
}
}
)*
};
}
impl_from_int_literal!(
u8 => U8, u16 => U16, u32 => U32, u64 => U64, u128 => U128, usize => Usize,
i8 => I8, i16 => I16, i32 => I32, i64 => I64, i128 => I128, isize => Isize,
);
mod sealed {
pub trait Sealed {}
}
/// Precondition: first byte of string has to be in `b'0'..=b'9'`.
#[inline(never)]
pub(crate) fn parse_impl(input: &str, first: u8) -> Result<IntegerLit<&str>, ParseError> {
// Figure out base and strip prefix base, if it exists.
let (end_prefix, base) = match (first, input.as_bytes().get(1)) {
(b'0', Some(b'b')) => (2, IntegerBase::Binary),
(b'0', Some(b'o')) => (2, IntegerBase::Octal),
(b'0', Some(b'x')) => (2, IntegerBase::Hexadecimal),
// Everything else is treated as decimal. Several cases are caught
// by this:
// - "123"
// - "0"
// - "0u8"
// - "0r" -> this will error later
_ => (0, IntegerBase::Decimal),
};
let without_prefix = &input[end_prefix..];
// Scan input to find the first character that's not a valid digit.
let is_valid_digit = match base {
IntegerBase::Binary => |b| matches!(b, b'0' | b'1' | b'_'),
IntegerBase::Octal => |b| matches!(b, b'0'..=b'7' | b'_'),
IntegerBase::Decimal => |b| matches!(b, b'0'..=b'9' | b'_'),
IntegerBase::Hexadecimal => |b| matches!(b, b'0'..=b'9' | b'a'..=b'f' | b'A'..=b'F' | b'_'),
};
let end_main = without_prefix.bytes()
.position(|b| !is_valid_digit(b))
.unwrap_or(without_prefix.len());
let (main_part, suffix) = without_prefix.split_at(end_main);
check_suffix(suffix).map_err(|kind| {
// This is just to have a nicer error kind for this special case. If the
// suffix is invalid, it is non-empty -> unwrap ok.
let first = suffix.as_bytes()[0];
if !is_valid_digit(first) && first.is_ascii_digit() {
perr(end_main + end_prefix, InvalidDigit)
} else {
perr(end_main + end_prefix..input.len(), kind)
}
})?;
if suffix.starts_with('e') || suffix.starts_with('E') {
return Err(perr(end_main, IntegerSuffixStartingWithE));
}
// Make sure main number part is not empty.
if main_part.bytes().filter(|&b| b != b'_').count() == 0 {
return Err(perr(end_prefix..end_prefix + end_main, NoDigits));
}
Ok(IntegerLit {
raw: input,
start_main_part: end_prefix,
end_main_part: end_main + end_prefix,
base,
})
}
/// The bases in which an integer can be specified.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum IntegerBase {
Binary,
Octal,
Decimal,
Hexadecimal,
}
impl IntegerBase {
/// Returns the literal prefix that indicates this base, i.e. `"0b"`,
/// `"0o"`, `""` and `"0x"`.
pub fn prefix(self) -> &'static str {
match self {
Self::Binary => "0b",
Self::Octal => "0o",
Self::Decimal => "",
Self::Hexadecimal => "0x",
}
}
/// Returns the base value, i.e. 2, 8, 10 or 16.
pub fn value(self) -> u8 {
match self {
Self::Binary => 2,
Self::Octal => 8,
Self::Decimal => 10,
Self::Hexadecimal => 16,
}
}
}
/// All possible integer type suffixes.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
#[non_exhaustive]
pub enum IntegerType {
U8,
U16,
U32,
U64,
U128,
Usize,
I8,
I16,
I32,
I64,
I128,
Isize,
}
impl IntegerType {
/// Returns the type corresponding to the given suffix (e.g. `"u8"` is
/// mapped to `Self::U8`). If the suffix is not a valid integer type,
/// `None` is returned.
pub fn from_suffix(suffix: &str) -> Option<Self> {
match suffix {
"u8" => Some(Self::U8),
"u16" => Some(Self::U16),
"u32" => Some(Self::U32),
"u64" => Some(Self::U64),
"u128" => Some(Self::U128),
"usize" => Some(Self::Usize),
"i8" => Some(Self::I8),
"i16" => Some(Self::I16),
"i32" => Some(Self::I32),
"i64" => Some(Self::I64),
"i128" => Some(Self::I128),
"isize" => Some(Self::Isize),
_ => None,
}
}
/// Returns the suffix for this type, e.g. `"u8"` for `Self::U8`.
pub fn suffix(self) -> &'static str {
match self {
Self::U8 => "u8",
Self::U16 => "u16",
Self::U32 => "u32",
Self::U64 => "u64",
Self::U128 => "u128",
Self::Usize => "usize",
Self::I8 => "i8",
Self::I16 => "i16",
Self::I32 => "i32",
Self::I64 => "i64",
Self::I128 => "i128",
Self::Isize => "isize",
}
}
}
impl FromStr for IntegerType {
type Err = ();
fn from_str(s: &str) -> Result<Self, Self::Err> {
Self::from_suffix(s).ok_or(())
}
}
impl fmt::Display for IntegerType {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.suffix().fmt(f)
}
}
#[cfg(test)]
mod tests;