Hash.h File Reference

Unified template-based hash function API. More...

#include "nfx/hashing/Concepts.h"
#include "nfx/hashing/Hasher.h"
#include "nfx/detail/hashing/Hash.inl"

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Functions
template<typename T, Hash32or64 HashType = uint32_t, HashType Seed = ( sizeof( HashType ) == 4 ? constants::FNV_OFFSET_BASIS_32 : constants::FNV_OFFSET_BASIS_64 )>
HashType	nfx::hashing::hash (const T &value) noexcept
	Hash a value with explicit type and hash size specification.

Detailed Description

Unified template-based hash function API.

Provides a clean, STL-style hash<T>() interface that delegates to Hasher<HashType, Seed>. Supports explicit type and hash size specification with optional custom seeding.

Definition in file Hash.h.

Function Documentation

hash()

template<typename T, Hash32or64 HashType = uint32_t, HashType Seed = ( sizeof( HashType ) == 4 ? constants::FNV_OFFSET_BASIS_32 : constants::FNV_OFFSET_BASIS_64 )>

HashType nfx::hashing::hash ( const T & value )

inlinenodiscardnoexcept

Hash a value with explicit type and hash size specification.

Template Parameters

T	The type of value to hash
HashType	The hash output type (uint32_t or uint64_t)
Seed	The seed value for hash initialization (default: FNV_OFFSET_BASIS_32 for 32-bit, FNV_OFFSET_BASIS_64 for 64-bit)

Parameters

value

The value to hash

Returns

Hash value of type HashType

Note

This function is marked [[nodiscard]] - the return value should not be ignored

Unified template-based hash function that provides a clean, STL-style API for hashing values. The function automatically selects appropriate algorithms based on input type:

• Strings: CRC32-C (SSE4.2 hardware-accelerated when available, compiler flags required)
• Integers: Multiplicative hashing (Knuth for 32-bit, Wang for 64-bit)
• Floating-point: Bit-representation hashing with normalization
• Complex types: Recursive element hashing with combining

Hardware Acceleration: String hashing uses SSE4.2 CRC32-C instructions when:

1. CPU supports SSE4.2 (runtime detection)
2. Code compiled with proper flags: -march=native or -msse4.2 (GCC/Clang), /arch:AVX (MSVC)

Without compiler flags, software fallback is used even if CPU supports SSE4.2.

Default Seed: FNV offset basis (0x811C9DC5 for 32-bit, 0xCBF29CE484222325 for 64-bit) provides consistent initialization across the library. For zero-seed behavior, explicitly specify: hash<T, HashType, 0>(value)

Internally delegates to Hasher<HashType, Seed> functor for type-specific implementations.

// Basic usage with default FNV seed
auto h1 = hash<int>(42);                           // uint32_t, seed=0x811C9DC5
auto h2 = hash<std::string>("hello");              // uint32_t, seed=0x811C9DC5
 
// 64-bit hash output
auto h3 = hash<std::string, uint64_t>("hello");    // uint64_t, seed=0xCBF29CE484222325
 
// Custom seeds
auto h4 = hash<int, uint32_t, 0>(42);              // Zero seed (no mixing)
auto h5 = hash<int, uint32_t, 0xDEADBEEF>(42);     // Custom seed