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/* MIT License - Copyright (c) 2025 wallstop
* Original C# implementation from: https://github.com/wallstop/unity-helpers
* Converted to C for librandom project
*
* @BAKE cc -O2 -Wall -Wextra -std=c99 -o wy_random wy_random.c -lm @STOP
*/
#include "wy_random.h"
#define WY_PRIME0 0xa0761d6478bd642fULL
#define WY_PRIME1 0xe7037ed1a0b428dbULL
/* Multiply two 64-bit integers and return hi and lo parts of 128-bit result */
static inline void multiply_64(uint64_t x, uint64_t y, uint64_t *hi, uint64_t *lo) {
uint64_t x0 = (uint32_t)x;
uint64_t x1 = x >> 32;
uint64_t y0 = (uint32_t)y;
uint64_t y1 = y >> 32;
uint64_t p11 = x1 * y1;
uint64_t p01 = x0 * y1;
uint64_t p10 = x1 * y0;
uint64_t p00 = x0 * y0;
uint64_t middle = p10 + (p00 >> 32) + (uint32_t)p01;
*lo = (middle << 32) | (uint32_t)p00;
*hi = p11 + (middle >> 32) + (p01 >> 32);
}
/* MUM (MUltiply and Mix) operation */
static inline uint64_t mum(uint64_t x, uint64_t y) {
uint64_t hi, lo;
multiply_64(x, y, &hi, &lo);
return hi ^ lo;
}
void wy_init(wy_random_t *rng, uint64_t seed) {
rng->state = seed;
}
uint32_t wy_next_uint(wy_random_t *rng) {
rng->state += WY_PRIME0;
return (uint32_t)mum(rng->state ^ WY_PRIME1, rng->state);
}
uint64_t wy_next_ulong(wy_random_t *rng) {
rng->state += WY_PRIME0;
return mum(rng->state ^ WY_PRIME1, rng->state);
}
float wy_next_float(wy_random_t *rng) {
uint32_t value = wy_next_uint(rng);
return (value >> 8) * 0x1.0p-24f;
}
double wy_next_double(wy_random_t *rng) {
uint64_t value = wy_next_ulong(rng);
return (value >> 11) * 0x1.0p-53;
}
#ifdef WY_TEST_MAIN
#include <stdio.h>
#include <time.h>
int main(void) {
wy_random_t rng;
printf("WyRandom C Implementation Test\n");
printf("===============================\n\n");
wy_init(&rng, 42);
printf("Testing with seed 42:\n");
printf("First 10 uint32_t values:\n");
for (int i = 0; i < 10; i++) {
printf(" %u\n", wy_next_uint(&rng));
}
printf("\nFirst 10 uint64_t values:\n");
wy_init(&rng, 42);
for (int i = 0; i < 10; i++) {
printf(" %llu\n", (unsigned long long)wy_next_ulong(&rng));
}
printf("\nFirst 10 float values:\n");
wy_init(&rng, 42);
for (int i = 0; i < 10; i++) {
printf(" %.6f\n", wy_next_float(&rng));
}
printf("\nPerformance test: generating 10 million uint64_t values...\n");
wy_init(&rng, (uint64_t)time(NULL));
clock_t start = clock();
uint64_t sum = 0;
for (int i = 0; i < 10000000; i++) {
sum += wy_next_ulong(&rng);
}
clock_t end = clock();
double elapsed = (double)(end - start) / CLOCKS_PER_SEC;
printf("Time: %.3f seconds (sum: %llu to prevent optimization)\n", elapsed, (unsigned long long)sum);
return 0;
}
#endif
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