Extract splitmix64 PRNG

src/prng/splitmix64/splitmix64.c

@@ -0,0 +1,97 @@
+// vim:fileencoding=utf-8:foldmethod=marker
+
+#include "splitmix64.h"
+#include "../../common/aliases/aliases.h"
+#include "../../common/assert/assert.h"
+#include "../../common/platform/platform.h"
+#include <stdlib.h>
+#include <time.h>
+
+wp_intern void seedOsGenerator(u64 seed);
+wp_intern u64 genRandomNumber(void);
+
+WpSplitmix64State wpPrngSplitmix64Init(void) {
+	wp_persist b8 seeded = false;
+	if (!seeded) {
+		seeded = true;
+		seedOsGenerator(0);
+	}
+
+	return (WpSplitmix64State){ .seed = genRandomNumber() };
+}
+
+WpSplitmix64State wpPrngSplitmix64InitWithSeed(u64 seed) {
+	return (WpSplitmix64State){ .seed = seed };
+}
+
+u64 wpPrngSplitmix64(WpSplitmix64State *state) {
+	state->seed += 0x9E3779B97f4A7C15;
+
+	u64 result = state->seed;
+	result = (result ^ (result >> 30)) * 0xBF58476D1CE4E5B9;
+	result = (result ^ (result >> 27)) * 0x94D049BB133111EB;
+
+	return result ^ (result >> 31);
+}
+
+u64 wpPrngSplitmix64InRange(WpSplitmix64State *state, u64 start, u64 end) {
+	return wpPrngSplitmix64(state) % (end - start) + start;
+}
+
+u64 wpPrngSplitmix64Choice(WpSplitmix64State *state, u64 available_choices) {
+	return wpPrngSplitmix64(state) % available_choices;
+}
+
+#if defined(WP_PLATFORM_C) && WP_PLATFORM_C_VERSION >= WP_PLATFORM_C11_VERSION
+#ifdef WP_PLATFORM_POSIX
+wp_intern void seedOsGenerator(u64 seed) {
+	if (seed == 0) {
+		struct timespec ts = {0};
+		int result = clock_gettime(CLOCK_MONOTONIC_RAW, &ts);
+		wpRuntimeAssert(result == 0, "Invalid seed value");
+		seed = (u64)ts.tv_nsec;
+	}
+
+	srand48(seed);
+}
+
+wp_intern u64 genRandomNumber(void) {
+	return lrand48();
+}
+#else
+wp_intern void seedOsGenerator(u64 seed) {
+	if (seed == 0) {
+		struct timespec ts = {0};
+		int result = timespec_get(&ts, TIME_UTC);
+		wpRuntimeAssert(result != 0, "Invalid seed value");
+		seed = (u64)ts.tv_nsec;
+	}
+
+	srand(seed);
+}
+
+wp_intern u64 genRandomNumber(void) {
+	i32 n1 = rand();
+	i32 n2 = rand();
+
+	return (((u64)n1) << 32 | (u64)n2);
+}
+#endif // !WP_PLATFORM_POSIX
+#else
+wp_intern void seedOsGenerator(u64 seed) {
+	if (seed == 0) {
+		time_t result = time(NULL);
+		wpRuntimeAssert(result != (time_t)(-1), "Invalid seed value");
+		seed = (u64)result;
+	}
+
+	srand(seed);
+}
+
+wp_intern u64 genRandomNumber(void) {
+	i32 n1 = rand();
+	i32 n2 = rand();
+
+	return (((u64)n1) << 32 | (u64)n2);
+}
+#endif // !WP_PLATFORM_C