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https://github.com/winterknife/SILVERPICK
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winterknife
113 lines
4.3 KiB
C++
113 lines
4.3 KiB
C++
// ========================================================================
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// File: HashString.h
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//
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// Author: winterknife
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//
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// Description: This header file contains inline routines to hash short
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// strings using non-cryptographic hash functions
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//
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// Modifications:
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// 2025-08-24 Created
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// 2025-09-22 Updated
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// ========================================================================
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// ========================================================================
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// Header guards
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// ========================================================================
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#pragma once
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// ========================================================================
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// Includes
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// ========================================================================
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#include <stdint.h>
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#include <sal.h>
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// ========================================================================
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// Macros
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// ========================================================================
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#pragma region MACROS
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// 64-bit magic prime for Fowler/Noll/Vo (FNV) hash
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// May not be modified
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#define FNV_PRIME_64 0x100000001B3ULL
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// 64-bit non-zero initial basis for FNV-1 hash
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// May be modified as long as it is non-zero
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#define FNV_OFFSET_BASIS_64 0xCBF29CE484222325ULL
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// Macro to hash a short string at compile time
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#define HASH_STRING_COMPILE_TIME(String) hash_string_fnv1a_64_as_constant(String, 0x95DD92DBA3D9E736ULL)
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// Macro to hash a short string at run time
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#define HASH_STRING_RUN_TIME(String, Length) hash_string_fnv1a_64(String, Length, 0x95DD92DBA3D9E736ULL)
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#pragma endregion
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// ========================================================================
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// Inline routines
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// ========================================================================
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#pragma region INLINES
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// Original implementation: http://www.isthe.com/chongo/tech/comp/fnv/index.html
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// Authors: Phong Vo, Glenn Fowler, Landon Curt Noll
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// Online hash lookup:
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// curl -s -D "/dev/stderr" https://hashdb.openanalysis.net/hash/fnv1a_64/<hash value in decimal> | jq
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/// @brief Hash a short string using 64-bit Fowler/Noll/Vo (FNV-1a) hash function
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/// @tparam Type Type template parameter that acts as a placeholder for the type of character literals that make up the string
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/// @param pctyString Pointer to a constant null-terminated string of ANSI/UNICODE characters
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/// @param dwptrSize Number of characters in the string, excluding the terminal null
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/// @param qwHash FNV offset basis (initial hash value)
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/// @return 64-bit unsigned integer representing the hash value
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template <typename Type>
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__attribute__((always_inline)) inline constexpr unsigned long long hash_string_fnv1a_64(
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_In_z_ const Type* pctyString,
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_In_ size_t dwptrSize,
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_In_ unsigned long long qwHash = FNV_OFFSET_BASIS_64
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) noexcept {
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// Init local variables
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unsigned char byCurrent = 0;
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// Hash each byte of the buffer
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while (dwptrSize--) {
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// Get current byte
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byCurrent = static_cast<unsigned char>(*pctyString++);
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// XOR the lower 8-bits of the hash value with the current byte
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qwHash ^= byCurrent;
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// Multiply the hash value by the 64-bit FNV magic prime mod 2^64
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qwHash *= FNV_PRIME_64;
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}
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return qwHash;
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}
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#pragma endregion
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// ========================================================================
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// Immediate routines
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// ========================================================================
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#pragma region IMMEDIATES
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/// @brief Hash a compile-time string constant at compile time using 64-bit Fowler/Noll/Vo (FNV-1a) hash function
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/// @tparam Type Type template parameter that acts as a placeholder for the type of character literals that make up the string
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/// @tparam Size Number of characters in the string, including the terminal null
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/// @param tyarrInputData Reference to an array of constant ANSI/UNICODE characters
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/// @param qwHash FNV offset basis (initial hash value)
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/// @return 64-bit unsigned integer representing the hash value
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template <typename Type, size_t Size>
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consteval auto hash_string_fnv1a_64_as_constant(
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_In_z_ const Type (&tyarrInputData)[Size],
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_In_ unsigned long long qwHash = FNV_OFFSET_BASIS_64
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) {
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return hash_string_fnv1a_64(tyarrInputData, (Size - 1), qwHash);
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}
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#pragma endregion |