Add UUIDv4 generator

src/uuid/uuid.c

@@ -0,0 +1,59 @@
+#include "uuid.h"
+#include "../common/aliases/aliases.h"
+#include "../core/strings/str8/str8.h"
+#include "../prng/xorshift/xorshift.h"
+#include <stdbool.h>
+#include <inttypes.h>
+
+#define UUID_STR_FORMAT ("%.8" PRIx64 "-%.4" PRIx64 "-%.4" PRIx64 "-%.4" PRIx64 "-%.12" PRIx64)
+
+typedef struct uuid4 UUID4;
+struct uuid4 {
+  u64 high;
+  u64 low;
+};
+
+internal UUID4 generate_uuid4(void);
+internal void  uuid4_to_uuid(const UUID4* uuid4, UUID *uuid);
+
+UUID *wapp_uuid_init_uuid4(UUID *uuid) {
+	if (!uuid) {
+		goto RETURN_INIT_UUID4;
+	}
+
+  UUID4 uuid4 = generate_uuid4();
+  uuid4_to_uuid(&uuid4, uuid);
+
+RETURN_INIT_UUID4:
+	return uuid;
+}
+
+internal UUID4 generate_uuid4(void) {
+  persistent XOR256State state = {0};
+  persistent bool initialised = false;
+
+  if (!initialised) {
+    initialised = true;
+    state       = wapp_prng_xorshift_init_state();
+  }
+
+  UUID4 uuid = (UUID4){
+    .high = wapp_prng_xorshift_256(&state),
+    .low  = wapp_prng_xorshift_256(&state),
+  };
+
+  uuid.high = (uuid.high & 0xffffffffffff0fff) | 0x0000000000004000;
+  uuid.low  = (uuid.low  & 0x3fffffffffffffff) | 0x8000000000000000;
+
+  return uuid;
+}
+
+internal void uuid4_to_uuid(const UUID4* uuid4, UUID *uuid) {
+  u64 grp1 = uuid4->high >> 32;
+  u64 grp2 = (uuid4->high << 32) >> 48;
+  u64 grp3 = (uuid4->high << 48) >> 48;
+  u64 grp4 = uuid4->low >> 48;
+  u64 grp5 = (uuid4->low << 16) >> 16;
+
+  wapp_str8_format(&(uuid->uuid), UUID_STR_FORMAT, grp1, grp2, grp3, grp4, grp5);
+}