checkers-inl.h

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#ifndef ADA_CHECKERS_INL_H
#define ADA_CHECKERS_INL_H
 
#include <bit>
#include <string_view>
 
namespace ada::checkers {
 
constexpr bool has_hex_prefix_unsafe(std::string_view input) {
  // This is actually efficient code, see has_hex_prefix for the assembly.
  constexpr bool is_little_endian = std::endian::native == std::endian::little;
  constexpr auto word0x =
      std::bit_cast<uint16_t>(static_cast<uint16_t>(0x7830));
  uint16_t two_first_bytes =
      static_cast<uint16_t>(input[0]) |
      static_cast<uint16_t>((static_cast<uint16_t>(input[1]) << 8));
  if constexpr (is_little_endian) {
    two_first_bytes |= 0x2000;
  } else {
    two_first_bytes |= 0x020;
  }
  return two_first_bytes == word0x;
}
 
constexpr bool has_hex_prefix(std::string_view input) {
  return input.size() >= 2 && has_hex_prefix_unsafe(input);
}
 
constexpr bool is_digit(char x) noexcept { return (x >= '0') & (x <= '9'); }
 
constexpr char to_lower(char x) noexcept { return (x | 0x20); }
 
constexpr bool is_alpha(char x) noexcept {
  return (to_lower(x) >= 'a') && (to_lower(x) <= 'z');
}
 
constexpr bool is_windows_drive_letter(std::string_view input) noexcept {
  return input.size() >= 2 &&
         (is_alpha(input[0]) && ((input[1] == ':') || (input[1] == '|'))) &&
         ((input.size() == 2) || (input[2] == '/' || input[2] == '\\' ||
                                  input[2] == '?' || input[2] == '#'));
}
 
constexpr bool is_normalized_windows_drive_letter(
    std::string_view input) noexcept {
  return input.size() >= 2 && (is_alpha(input[0]) && (input[1] == ':'));
}
 
}  // namespace ada::checkers
 
#endif  // ADA_CHECKERS_INL_H