hash

---

layout: default title: Hash

Hash Functions

Overview

Non-cryptographic hash functions for all numeric types, generic data buffer hashing via FNV-1a, and hash combining for composite objects.

Why Use This?

Fast hashing is needed for hash tables, deduplication, checksums, and spatial hashing. These are not suitable for cryptographic purposes.

Functions

Bit-Mixing Functions

Low-level functions that mix bits of an integer for better hash distribution.

Function	Description
lm2_hash_mix_u64(x)	64-bit mixing
lm2_hash_mix_u32(x)	32-bit mixing

Numeric Type Hashing

Function	Input	Output
lm2_hash_f64(value)	double	uint64_t
lm2_hash_f32(value)	float	uint32_t
lm2_hash_i64(value)	int64_t	uint64_t
lm2_hash_i32(value)	int32_t	uint32_t
lm2_hash_i16(value)	int16_t	uint32_t
lm2_hash_i8(value)	int8_t	uint32_t
lm2_hash_u64(value)	uint64_t	uint64_t
lm2_hash_u32(value)	uint32_t	uint32_t
lm2_hash_u16(value)	uint16_t	uint32_t
lm2_hash_u8(value)	uint8_t	uint32_t

Buffer Hashing (FNV-1a)

Function	Description
lm2_hash_fnv1a_u32(data, size)	FNV-1a hash of arbitrary data (32-bit)
lm2_hash_fnv1a_u64(data, size)	FNV-1a hash of arbitrary data (64-bit)

Hash Combining

Combine two hash values into one. Useful for hashing composite objects (e.g., hash a struct by combining hashes of its fields).

Function	Description
lm2_hash_combine_u32(seed, hash)	Combine two 32-bit hashes
lm2_hash_combine_u64(seed, hash)	Combine two 64-bit hashes

Example

// Hash a 2D grid cell
int32_t cell_x = 42, cell_y = 17;
uint32_t h = lm2_hash_combine_u32(lm2_hash_i32(cell_x), lm2_hash_i32(cell_y));

// Hash arbitrary data
const char* str = "hello";
uint32_t str_hash = lm2_hash_fnv1a_u32(str, 5);