fnv1 hash utilities

fnv1.hpp

#pragma once

namespace uti
{
   static constexpr std::uint32_t fnv1_basis = 0x811c9dc5;
   static constexpr std::uint32_t fnv1_prime = 0x01000193;

   [[ nodiscard ]]
   constexpr std::uint32_t fnv1_hash_ct( const char* string, const std::uint32_t basis = fnv1_basis )
   {
      return ( string[0] == '\0' ) ? basis : fnv1_hash_ct( &string[1], ( string[0] ^ basis ) * fnv1_prime );
   }

   [[ nodiscard ]]
   constexpr std::uint32_t fnv1_hash_ct_w( const wchar_t* string, const std::uint32_t basis = fnv1_basis )
   {
      return ( string[0] == L'\0' ) ? basis : fnv1_hash_ct_w( &string[1], ( string[0] ^ basis ) * fnv1_prime );
   }

   [[ nodiscard ]]
   std::uint32_t fnv1_hash( const char* string )
   {
      auto fnv_ret = fnv1_basis;
      auto fnv_len = std::strlen( string );

      for ( std::size_t idx{}; idx < fnv_len; idx++ )
      {
         fnv_ret ^= string[idx];
         fnv_ret *= fnv1_prime;
      }
      return fnv_ret;
   }

   [[ nodiscard ]]
   std::uint32_t fnv1_hash_w( const wchar_t* string )
   {
      auto fnv_ret = fnv1_basis;
      auto fnv_len = std::wcslen( string );

      for ( std::size_t idx{}; idx < fnv_len; idx++ )
      {
         fnv_ret ^= string[idx];
         fnv_ret *= fnv1_prime;
      }
      return fnv_ret;
   }
}

#define _fnv1_ctw( wstr ) []( ){ constexpr std::uint32_t ctx = uti::fnv1_hash_ct_w( wstr ); return ctx; }( )
#define _fnv1_ct( str ) []( ){ constexpr std::uint32_t ctx = uti::fnv1_hash_ct( str ); return ctx; }( )

#define _fnv1_w( wstr ) uti::fnv1_hash_w( wstr )
#define _fnv1( str ) uti::fnv1_hash( str )