make has_hex_prefix_unsafe constexpr

include/ada/checkers-inl.h

@@ -5,32 +5,27 @@
 #ifndef ADA_CHECKERS_INL_H
 #define ADA_CHECKERS_INL_H
 
-#include "ada/common_defs.h"
-
-#include <algorithm>
 #include <string_view>
-#include <cstring>
 
 namespace ada::checkers {
 
-inline bool has_hex_prefix_unsafe(std::string_view input) {
+constexpr bool has_hex_prefix_unsafe(std::string_view input) {
   // This is actually efficient code, see has_hex_prefix for the assembly.
-  uint32_t value_one = 1;
-  bool is_little_endian = (reinterpret_cast<char*>(&value_one)[0] == 1);
-  uint16_t word0x{};
-  std::memcpy(&word0x, "0x", 2);  // we would use bit_cast in C++20 and the
-                                  // function could be constexpr.
-  uint16_t two_first_bytes{};
-  std::memcpy(&two_first_bytes, input.data(), 2);
-  if (is_little_endian) {
+  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;
 }
 
-inline bool has_hex_prefix(std::string_view input) {
+constexpr bool has_hex_prefix(std::string_view input) {
   return input.size() >= 2 && has_hex_prefix_unsafe(input);
 }
 
@@ -42,14 +37,14 @@ constexpr bool is_alpha(char x) noexcept {
   return (to_lower(x) >= 'a') && (to_lower(x) <= 'z');
 }
 
-inline constexpr bool is_windows_drive_letter(std::string_view input) noexcept {
+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] == '#'));
 }
 
-inline constexpr bool is_normalized_windows_drive_letter(
+constexpr bool is_normalized_windows_drive_letter(
     std::string_view input) noexcept {
   return input.size() >= 2 && (is_alpha(input[0]) && (input[1] == ':'));
 }

include/ada/checkers.h

@@ -43,12 +43,12 @@ constexpr bool is_alpha(char x) noexcept;
  *
  * @see has_hex_prefix
  */
-inline bool has_hex_prefix_unsafe(std::string_view input);
+constexpr bool has_hex_prefix_unsafe(std::string_view input);
 /**
  * @private
  * Check whether a string starts with 0x or 0X.
  */
-inline bool has_hex_prefix(std::string_view input);
+constexpr bool has_hex_prefix(std::string_view input);
 
 /**
  * @private