src/tools/clippy/clippy_utils/src/numeric_literal.rs

   1 use rustc_ast::ast::{Lit, LitFloatType, LitIntType, LitKind};
   2 use std::iter;
   3
   4 #[derive(Debug, PartialEq, Copy, Clone)]
   5 pub enum Radix {
   6     Binary,
   7     Octal,
   8     Decimal,
   9     Hexadecimal,
  10 }
  11
  12 impl Radix {
  13     /// Returns a reasonable digit group size for this radix.
  14     #[must_use]
  15     fn suggest_grouping(self) -> usize {
  16         match self {
  17             Self::Binary | Self::Hexadecimal => 4,
  18             Self::Octal | Self::Decimal => 3,
  19         }
  20     }
  21 }
  22
  23 /// A helper method to format numeric literals with digit grouping.
  24 /// `lit` must be a valid numeric literal without suffix.
  25 pub fn format(lit: &str, type_suffix: Option<&str>, float: bool) -> String {
  26     NumericLiteral::new(lit, type_suffix, float).format()
  27 }
  28
  29 #[derive(Debug)]
  30 pub struct NumericLiteral<'a> {
  31     /// Which radix the literal was represented in.
  32     pub radix: Radix,
  33     /// The radix prefix, if present.
  34     pub prefix: Option<&'a str>,
  35
  36     /// The integer part of the number.
  37     pub integer: &'a str,
  38     /// The fraction part of the number.
  39     pub fraction: Option<&'a str>,
  40     /// The exponent separator (b'e' or b'E') including preceding underscore if present
  41     /// and the exponent part.
  42     pub exponent: Option<(&'a str, &'a str)>,
  43
  44     /// The type suffix, including preceding underscore if present.
  45     pub suffix: Option<&'a str>,
  46 }
  47
  48 impl<'a> NumericLiteral<'a> {
  49     pub fn from_lit(src: &'a str, lit: &Lit) -> Option<NumericLiteral<'a>> {
  50         NumericLiteral::from_lit_kind(src, &lit.kind)
  51     }
  52
  53     pub fn from_lit_kind(src: &'a str, lit_kind: &LitKind) -> Option<NumericLiteral<'a>> {
  54         if lit_kind.is_numeric() && src.chars().next().map_or(false, |c| c.is_digit(10)) {
  55             let (unsuffixed, suffix) = split_suffix(src, lit_kind);
  56             let float = matches!(lit_kind, LitKind::Float(..));
  57             Some(NumericLiteral::new(unsuffixed, suffix, float))
  58         } else {
  59             None
  60         }
  61     }
  62
  63     #[must_use]
  64     pub fn new(lit: &'a str, suffix: Option<&'a str>, float: bool) -> Self {
  65         // Determine delimiter for radix prefix, if present, and radix.
  66         let radix = if lit.starts_with("0x") {
  67             Radix::Hexadecimal
  68         } else if lit.starts_with("0b") {
  69             Radix::Binary
  70         } else if lit.starts_with("0o") {
  71             Radix::Octal
  72         } else {
  73             Radix::Decimal
  74         };
  75
  76         // Grab part of the literal after prefix, if present.
  77         let (prefix, mut sans_prefix) = if let Radix::Decimal = radix {
  78             (None, lit)
  79         } else {
  80             let (p, s) = lit.split_at(2);
  81             (Some(p), s)
  82         };
  83
  84         if suffix.is_some() && sans_prefix.ends_with('_') {
  85             // The '_' before the suffix isn't part of the digits
  86             sans_prefix = &sans_prefix[..sans_prefix.len() - 1];
  87         }
  88
  89         let (integer, fraction, exponent) = Self::split_digit_parts(sans_prefix, float);
  90
  91         Self {
  92             radix,
  93             prefix,
  94             integer,
  95             fraction,
  96             exponent,
  97             suffix,
  98         }
  99     }
 100
 101     pub fn is_decimal(&self) -> bool {
 102         self.radix == Radix::Decimal
 103     }
 104
 105     pub fn split_digit_parts(digits: &str, float: bool) -> (&str, Option<&str>, Option<(&str, &str)>) {
 106         let mut integer = digits;
 107         let mut fraction = None;
 108         let mut exponent = None;
 109
 110         if float {
 111             for (i, c) in digits.char_indices() {
 112                 match c {
 113                     '.' => {
 114                         integer = &digits[..i];
 115                         fraction = Some(&digits[i + 1..]);
 116                     },
 117                     'e' | 'E' => {
 118                         let exp_start = if digits[..i].ends_with('_') { i - 1 } else { i };
 119
 120                         if integer.len() > exp_start {
 121                             integer = &digits[..exp_start];
 122                         } else {
 123                             fraction = Some(&digits[integer.len() + 1..exp_start]);
 124                         };
 125                         exponent = Some((&digits[exp_start..=i], &digits[i + 1..]));
 126                         break;
 127                     },
 128                     _ => {},
 129                 }
 130             }
 131         }
 132
 133         (integer, fraction, exponent)
 134     }
 135
 136     /// Returns literal formatted in a sensible way.
 137     pub fn format(&self) -> String {
 138         let mut output = String::new();
 139
 140         if let Some(prefix) = self.prefix {
 141             output.push_str(prefix);
 142         }
 143
 144         let group_size = self.radix.suggest_grouping();
 145
 146         Self::group_digits(
 147             &mut output,
 148             self.integer,
 149             group_size,
 150             true,
 151             self.radix == Radix::Hexadecimal,
 152         );
 153
 154         if let Some(fraction) = self.fraction {
 155             output.push('.');
 156             Self::group_digits(&mut output, fraction, group_size, false, false);
 157         }
 158
 159         if let Some((separator, exponent)) = self.exponent {
 160             output.push_str(separator);
 161             Self::group_digits(&mut output, exponent, group_size, true, false);
 162         }
 163
 164         if let Some(suffix) = self.suffix {
 165             if output.ends_with('.') {
 166                 output.push('0');
 167             }
 168             output.push('_');
 169             output.push_str(suffix);
 170         }
 171
 172         output
 173     }
 174
 175     pub fn group_digits(output: &mut String, input: &str, group_size: usize, partial_group_first: bool, pad: bool) {
 176         debug_assert!(group_size > 0);
 177
 178         let mut digits = input.chars().filter(|&c| c != '_');
 179
 180         let first_group_size;
 181
 182         if partial_group_first {
 183             first_group_size = (digits.clone().count() - 1) % group_size + 1;
 184             if pad {
 185                 for _ in 0..group_size - first_group_size {
 186                     output.push('0');
 187                 }
 188             }
 189         } else {
 190             first_group_size = group_size;
 191         }
 192
 193         for _ in 0..first_group_size {
 194             if let Some(digit) = digits.next() {
 195                 output.push(digit);
 196             }
 197         }
 198
 199         for (c, i) in iter::zip(digits, (0..group_size).cycle()) {
 200             if i == 0 {
 201                 output.push('_');
 202             }
 203             output.push(c);
 204         }
 205     }
 206 }
 207
 208 fn split_suffix<'a>(src: &'a str, lit_kind: &LitKind) -> (&'a str, Option<&'a str>) {
 209     debug_assert!(lit_kind.is_numeric());
 210     lit_suffix_length(lit_kind).map_or((src, None), |suffix_length| {
 211         let (unsuffixed, suffix) = src.split_at(src.len() - suffix_length);
 212         (unsuffixed, Some(suffix))
 213     })
 214 }
 215
 216 fn lit_suffix_length(lit_kind: &LitKind) -> Option<usize> {
 217     debug_assert!(lit_kind.is_numeric());
 218     let suffix = match lit_kind {
 219         LitKind::Int(_, int_lit_kind) => match int_lit_kind {
 220             LitIntType::Signed(int_ty) => Some(int_ty.name_str()),
 221             LitIntType::Unsigned(uint_ty) => Some(uint_ty.name_str()),
 222             LitIntType::Unsuffixed => None,
 223         },
 224         LitKind::Float(_, float_lit_kind) => match float_lit_kind {
 225             LitFloatType::Suffixed(float_ty) => Some(float_ty.name_str()),
 226             LitFloatType::Unsuffixed => None,
 227         },
 228         _ => None,
 229     };
 230
 231     suffix.map(str::len)
 232 }