CRC32.h

namespace CRC32
{
	unsigned int uiCRC32_Table[256] =
	{
		0x00000000L, 0x77073096L, 0xEE0E612CL,
		0x990951BAL, 0x076DC419L, 0x706AF48FL,
		0xE963A535L, 0x9E6495A3L, 0x0EDB8832L,
		0x79DCB8A4L, 0xE0D5E91EL, 0x97D2D988L,
		0x09B64C2BL, 0x7EB17CBDL, 0xE7B82D07L,
		0x90BF1D91L, 0x1DB71064L, 0x6AB020F2L,
		0xF3B97148L, 0x84BE41DEL, 0x1ADAD47DL,
		0x6DDDE4EBL, 0xF4D4B551L, 0x83D385C7L,
		0x136C9856L, 0x646BA8C0L, 0xFD62F97AL,
		0x8A65C9ECL, 0x14015C4FL, 0x63066CD9L,
		0xFA0F3D63L, 0x8D080DF5L, 0x3B6E20C8L,
		0x4C69105EL, 0xD56041E4L, 0xA2677172L,
		0x3C03E4D1L, 0x4B04D447L, 0xD20D85FDL,
		0xA50AB56BL, 0x35B5A8FAL, 0x42B2986CL,
		0xDBBBC9D6L, 0xACBCF940L, 0x32D86CE3L,
		0x45DF5C75L, 0xDCD60DCFL, 0xABD13D59L,
		0x26D930ACL, 0x51DE003AL, 0xC8D75180L,
		0xBFD06116L, 0x21B4F4B5L, 0x56B3C423L,
		0xCFBA9599L, 0xB8BDA50FL, 0x2802B89EL,
		0x5F058808L, 0xC60CD9B2L, 0xB10BE924L,
		0x2F6F7C87L, 0x58684C11L, 0xC1611DABL,
		0xB6662D3DL, 0x76DC4190L, 0x01DB7106L,
		0x98D220BCL, 0xEFD5102AL, 0x71B18589L,
		0x06B6B51FL, 0x9FBFE4A5L, 0xE8B8D433L,
		0x7807C9A2L, 0x0F00F934L, 0x9609A88EL,
		0xE10E9818L, 0x7F6A0DBBL, 0x086D3D2DL,
		0x91646C97L, 0xE6635C01L, 0x6B6B51F4L,
		0x1C6C6162L, 0x856530D8L, 0xF262004EL,
		0x6C0695EDL, 0x1B01A57BL, 0x8208F4C1L,
		0xF50FC457L, 0x65B0D9C6L, 0x12B7E950L,
		0x8BBEB8EAL, 0xFCB9887CL, 0x62DD1DDFL,
		0x15DA2D49L, 0x8CD37CF3L, 0xFBD44C65L,
		0x4DB26158L, 0x3AB551CEL, 0xA3BC0074L,
		0xD4BB30E2L, 0x4ADFA541L, 0x3DD895D7L,
		0xA4D1C46DL, 0xD3D6F4FBL, 0x4369E96AL,
		0x346ED9FCL, 0xAD678846L, 0xDA60B8D0L,
		0x44042D73L, 0x33031DE5L, 0xAA0A4C5FL,
		0xDD0D7CC9L, 0x5005713CL, 0x270241AAL,
		0xBE0B1010L, 0xC90C2086L, 0x5768B525L,
		0x206F85B3L, 0xB966D409L, 0xCE61E49FL,
		0x5EDEF90EL, 0x29D9C998L, 0xB0D09822L,
		0xC7D7A8B4L, 0x59B33D17L, 0x2EB40D81L,
		0xB7BD5C3BL, 0xC0BA6CADL, 0xEDB88320L,
		0x9ABFB3B6L, 0x03B6E20CL, 0x74B1D29AL,
		0xEAD54739L, 0x9DD277AFL, 0x04DB2615L,
		0x73DC1683L, 0xE3630B12L, 0x94643B84L,
		0x0D6D6A3EL, 0x7A6A5AA8L, 0xE40ECF0BL,
		0x9309FF9DL, 0x0A00AE27L, 0x7D079EB1L,
		0xF00F9344L, 0x8708A3D2L, 0x1E01F268L,
		0x6906C2FEL, 0xF762575DL, 0x806567CBL,
		0x196C3671L, 0x6E6B06E7L, 0xFED41B76L,
		0x89D32BE0L, 0x10DA7A5AL, 0x67DD4ACCL,
		0xF9B9DF6FL, 0x8EBEEFF9L, 0x17B7BE43L,
		0x60B08ED5L, 0xD6D6A3E8L, 0xA1D1937EL,
		0x38D8C2C4L, 0x4FDFF252L, 0xD1BB67F1L,
		0xA6BC5767L, 0x3FB506DDL, 0x48B2364BL,
		0xD80D2BDAL, 0xAF0A1B4CL, 0x36034AF6L,
		0x41047A60L, 0xDF60EFC3L, 0xA867DF55L,
		0x316E8EEFL, 0x4669BE79L, 0xCB61B38CL,
		0xBC66831AL, 0x256FD2A0L, 0x5268E236L,
		0xCC0C7795L, 0xBB0B4703L, 0x220216B9L,
		0x5505262FL, 0xC5BA3BBEL, 0xB2BD0B28L,
		0x2BB45A92L, 0x5CB36A04L, 0xC2D7FFA7L,
		0xB5D0CF31L, 0x2CD99E8BL, 0x5BDEAE1DL,
		0x9B64C2B0L, 0xEC63F226L, 0x756AA39CL,
		0x026D930AL, 0x9C0906A9L, 0xEB0E363FL,
		0x72076785L, 0x05005713L, 0x95BF4A82L,
		0xE2B87A14L, 0x7BB12BAEL, 0x0CB61B38L,
		0x92D28E9BL, 0xE5D5BE0DL, 0x7CDCEFB7L,
		0x0BDBDF21L, 0x86D3D2D4L, 0xF1D4E242L,
		0x68DDB3F8L, 0x1FDA836EL, 0x81BE16CDL,
		0xF6B9265BL, 0x6FB077E1L, 0x18B74777L,
		0x88085AE6L, 0xFF0F6A70L, 0x66063BCAL,
		0x11010B5CL, 0x8F659EFFL, 0xF862AE69L,
		0x616BFFD3L, 0x166CCF45L, 0xA00AE278L,
		0xD70DD2EEL, 0x4E048354L, 0x3903B3C2L,
		0xA7672661L, 0xD06016F7L, 0x4969474DL,
		0x3E6E77DBL, 0xAED16A4AL, 0xD9D65ADCL,
		0x40DF0B66L, 0x37D83BF0L, 0xA9BCAE53L,
		0xDEBB9EC5L, 0x47B2CF7FL, 0x30B5FFE9L,
		0xBDBDF21CL, 0xCABAC28AL, 0x53B39330L,
		0x24B4A3A6L, 0xBAD03605L, 0xCDD70693L,
		0x54DE5729L, 0x23D967BFL, 0xB3667A2EL,
		0xC4614AB8L, 0x5D681B02L, 0x2A6F2B94L,
		0xB40BBE37L, 0xC30C8EA1L, 0x5A05DF1BL,
		0x2D02EF8DL
	};

	unsigned int CRC32(void* pData, size_t iLen)
	{
		unsigned int uiCRC32 = 0xFFFFFFFF;
		unsigned char* pszData = (unsigned char*)pData;

		for (size_t i = 0; i < iLen; ++i)
			uiCRC32 = ((uiCRC32 >> 8) & 0x00FFFFFF) ^ uiCRC32_Table[(uiCRC32 ^ (unsigned int)*pszData++) & 0xFF];

		return (uiCRC32 ^ 0xFFFFFFFF);
	}

	unsigned int ToCRC32(std::string Sz)
	{
		unsigned int Hash = CRC32((void*)Sz.data(), Sz.length());
		return Hash;
		//	std::cout << "0x" << std::uppercase << std::hex << Hash << " -> " << Sz.c_str() << std::endl;
	}
}

namespace Hash
{
#pragma once

	// todo - dex; check arg type for macros?

	// hash type.
	using hash32_t = uint32_t;

	// compile-time hash.
#define HASH( str )                                     \
    []() {                                              \
        constexpr Hash::hash32_t out{ Hash::FNV1a::Get( str ) };    \
                                                        \
        return out;                                     \
    }()

// compile-time const hash.
#define CONST_HASH( str ) Hash::FNV1a::Get( str )

	class FNV1a
	{
	private:
		// fnv1a constants.
		enum : uint32_t
		{
			PRIME = 0x1000193u,
			BASIS = 0x811C9DC5u
		};

		// compile-time strlen.
		// todo - dex; move this?
		static __forceinline constexpr size_t ct_strlen(const char* str, bool include_nullchar = false)
		{
			size_t out{};

			// count number of characters.
			while (str[++out] != '\0');

			// add one for null character if desired.
			if (include_nullchar)
				++out;

			return out;
		}

	public:
		// hash data ( compile-time or run-time ).
		static __forceinline constexpr hash32_t Get(const uint8_t* data, const size_t len)
		{
			hash32_t out{ BASIS };

			for (size_t i{}; i < len; ++i)
				out = (out ^ data[i]) * PRIME;

			return out;
		}

		// hash c-style string ( compile-time or run-time ).
		static __forceinline constexpr hash32_t Get(const char* str)
		{
			hash32_t out{ BASIS };
			size_t   len{ ct_strlen(str) };

			for (size_t i{}; i < len; ++i)
				out = (out ^ str[i]) * PRIME;

			return out;
		}

		// hash c++-style string ( run-time only ).
		static __forceinline hash32_t Get(const std::string& str)
		{
			return Get((uint8_t*)str.c_str(), str.size());
		}
	};
}