implement xorshift

1 files changed, 20 insertions, 0 deletions

diff --git a/lichen.c b/lichen.c
new file mode 100644
index 0000000..f20c1b3
--- /dev/null
+++ b/lichen.c
@@ -0,0 +1,20 @@
+#include "lichen.h"
+
+
+void li_xorshift32_seed(struct li_xorshift32_t *xor, uint32_t seed) {
+  xor->state = seed ? seed : 1;
+  xor->generator.rand = li_xorshift32;
+  xor->generator.state = &(xor->state);
+}
+
+
+uint32_t li_xorshift32(void *s) {
+  uint64_t x = *((uint64_t*)s);
+  x ^= x >> 12;
+  x ^= x << 25;
+  x ^= x >> 27;
+  x *= 0x2545F4914F6CDD1DULL;
+  *((uint64_t*)s) = x;
+  // return just top 32 bits
+  return x >> 32;
+}