mfbt/TextUtils.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 /* Character/text operations. */
   8
   9 #ifndef mozilla_TextUtils_h
  10 #define mozilla_TextUtils_h
  11
  12 #include "mozilla/Assertions.h"
  13 #include "mozilla/TypeTraits.h"
  14
  15 namespace mozilla {
  16
  17 namespace detail {
  18
  19 template <typename Char>
  20 class MakeUnsignedChar : public MakeUnsigned<Char> {};
  21
  22 template <>
  23 class MakeUnsignedChar<char16_t> {
  24  public:
  25   using Type = char16_t;
  26 };
  27
  28 template <>
  29 class MakeUnsignedChar<char32_t> {
  30  public:
  31   using Type = char32_t;
  32 };
  33
  34 }  // namespace detail
  35
  36 /** Returns true iff |aChar| is ASCII, i.e. in the range [0, 0x80). */
  37 template <typename Char>
  38 constexpr bool IsAscii(Char aChar) {
  39   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
  40   auto uc = static_cast<UnsignedChar>(aChar);
  41   return uc < 0x80;
  42 }
  43
  44 /**
  45  * Returns true iff every character in the null-terminated string pointed to by
  46  * |aChar| is ASCII, i.e. in the range [0, 0x80).
  47  */
  48 template <typename Char>
  49 constexpr bool IsAsciiNullTerminated(const Char* aChar) {
  50   while (Char c = *aChar++) {
  51     if (!IsAscii(c)) {
  52       return false;
  53     }
  54   }
  55   return true;
  56 }
  57
  58 /**
  59  * Returns true iff |aChar| is Latin-1 but not ASCII, i.e. in the range
  60  * [0x80, 0xFF].
  61  */
  62 template <typename Char>
  63 constexpr bool IsNonAsciiLatin1(Char aChar) {
  64   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
  65   auto uc = static_cast<UnsignedChar>(aChar);
  66   return uc >= 0x80 && uc <= 0xFF;
  67 }
  68
  69 /**
  70  * Returns true iff |aChar| matches Ascii Whitespace.
  71  *
  72  * This function is intended to match the Infra standard
  73  * (https://infra.spec.whatwg.org/#ascii-whitespace)
  74  */
  75 template <typename Char>
  76 constexpr bool IsAsciiWhitespace(Char aChar) {
  77   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
  78   auto uc = static_cast<UnsignedChar>(aChar);
  79   return uc == 0x9 || uc == 0xA || uc == 0xC || uc == 0xD || uc == 0x20;
  80 }
  81
  82 /**
  83  * Returns true iff |aChar| matches [a-z].
  84  *
  85  * This function is basically what you thought islower was, except its behavior
  86  * doesn't depend on the user's current locale.
  87  */
  88 template <typename Char>
  89 constexpr bool IsAsciiLowercaseAlpha(Char aChar) {
  90   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
  91   auto uc = static_cast<UnsignedChar>(aChar);
  92   return 'a' <= uc && uc <= 'z';
  93 }
  94
  95 /**
  96  * Returns true iff |aChar| matches [A-Z].
  97  *
  98  * This function is basically what you thought isupper was, except its behavior
  99  * doesn't depend on the user's current locale.
 100  */
 101 template <typename Char>
 102 constexpr bool IsAsciiUppercaseAlpha(Char aChar) {
 103   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
 104   auto uc = static_cast<UnsignedChar>(aChar);
 105   return 'A' <= uc && uc <= 'Z';
 106 }
 107
 108 /**
 109  * Returns true iff |aChar| matches [a-zA-Z].
 110  *
 111  * This function is basically what you thought isalpha was, except its behavior
 112  * doesn't depend on the user's current locale.
 113  */
 114 template <typename Char>
 115 constexpr bool IsAsciiAlpha(Char aChar) {
 116   return IsAsciiLowercaseAlpha(aChar) || IsAsciiUppercaseAlpha(aChar);
 117 }
 118
 119 /**
 120  * Returns true iff |aChar| matches [0-9].
 121  *
 122  * This function is basically what you thought isdigit was, except its behavior
 123  * doesn't depend on the user's current locale.
 124  */
 125 template <typename Char>
 126 constexpr bool IsAsciiDigit(Char aChar) {
 127   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
 128   auto uc = static_cast<UnsignedChar>(aChar);
 129   return '0' <= uc && uc <= '9';
 130 }
 131
 132 /**
 133  * Returns true iff |aChar| matches [0-9a-fA-F].
 134  *
 135  * This function is basically isxdigit, but guaranteed to be only for ASCII.
 136  */
 137 template <typename Char>
 138 constexpr bool IsAsciiHexDigit(Char aChar) {
 139   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
 140   auto uc = static_cast<UnsignedChar>(aChar);
 141   return ('0' <= uc && uc <= '9') || ('a' <= uc && uc <= 'f') ||
 142          ('A' <= uc && uc <= 'F');
 143 }
 144
 145 /**
 146  * Returns true iff |aChar| matches [a-zA-Z0-9].
 147  *
 148  * This function is basically what you thought isalnum was, except its behavior
 149  * doesn't depend on the user's current locale.
 150  */
 151 template <typename Char>
 152 constexpr bool IsAsciiAlphanumeric(Char aChar) {
 153   return IsAsciiDigit(aChar) || IsAsciiAlpha(aChar);
 154 }
 155
 156 /**
 157  * Converts an ASCII alphanumeric digit [0-9a-zA-Z] to number as if in base-36.
 158  * (This function therefore works for decimal, hexadecimal, etc.).
 159  */
 160 template <typename Char>
 161 uint8_t AsciiAlphanumericToNumber(Char aChar) {
 162   using UnsignedChar = typename detail::MakeUnsignedChar<Char>::Type;
 163   auto uc = static_cast<UnsignedChar>(aChar);
 164
 165   if ('0' <= uc && uc <= '9') {
 166     return uc - '0';
 167   }
 168
 169   if ('A' <= uc && uc <= 'Z') {
 170     return uc - 'A' + 10;
 171   }
 172
 173   // Ideally this function would be constexpr, but unfortunately gcc at least as
 174   // of 6.4 forbids non-constexpr function calls in unevaluated constexpr
 175   // function calls.  See bug 1453456.  So for now, just assert and leave the
 176   // entire function non-constexpr.
 177   MOZ_ASSERT('a' <= uc && uc <= 'z',
 178              "non-ASCII alphanumeric character can't be converted to number");
 179   return uc - 'a' + 10;
 180 }
 181
 182 }  // namespace mozilla
 183
 184 #endif /* mozilla_TextUtils_h */