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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 xorshift_random xorshift_random.c -lm @STOP
*/
#include "xorshift_random.h"
static uint32_t normalize_state(uint32_t state) {
return state != 0 ? state : XORSHIFT_DEFAULT_STATE;
}
void xorshift_init(xorshift_random_t *rng, uint32_t seed) {
rng->state = normalize_state(seed);
}
uint32_t xorshift_next_uint(xorshift_random_t *rng) {
rng->state = normalize_state(rng->state);
rng->state ^= rng->state << 13;
rng->state ^= rng->state >> 17;
rng->state ^= rng->state << 5;
return rng->state;
}
float xorshift_next_float(xorshift_random_t *rng) {
uint32_t value = xorshift_next_uint(rng);
return (value >> 8) * 0x1.0p-24f;
}
double xorshift_next_double(xorshift_random_t *rng) {
uint32_t high = xorshift_next_uint(rng);
uint32_t low = xorshift_next_uint(rng);
uint64_t combined = ((uint64_t)high << 32) | low;
return (combined >> 11) * 0x1.0p-53;
}
#ifdef XORSHIFT_TEST_MAIN
#include <stdio.h>
#include <time.h>
int main(void) {
xorshift_random_t rng;
printf("XorShift Random C Implementation Test\n");
printf("=====================================\n\n");
xorshift_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", xorshift_next_uint(&rng));
}
printf("\nFirst 10 float values:\n");
xorshift_init(&rng, 42);
for (int i = 0; i < 10; i++) {
printf(" %.6f\n", xorshift_next_float(&rng));
}
printf("\nPerformance test: generating 10 million uint32_t values...\n");
xorshift_init(&rng, (uint32_t)time(NULL));
clock_t start = clock();
uint64_t sum = 0;
for (int i = 0; i < 10000000; i++) {
sum += xorshift_next_uint(&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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