Rename dirs

lib/random.c

@@ -0,0 +1,61 @@
+#define pr_fmt(fmt) "random: " fmt
+
+#include <zinnia/atomic.h>
+#include <zinnia/clock.h>
+#include <zinnia/print.h>
+#include <zinnia/random.h>
+#include <zinnia/spin.h>
+#include <string.h>
+
+static _Atomic(uint64_t) state = 0x9E37'79B9'7F4A'7C15;
+
+static bool dumb_random(struct random_source*, uint64_t* out) {
+    uint64_t z = atomic_fetch_add(&state, 0x9E37'79B9'7F4A'7C15, ATOMIC_RELAXED);
+    z ^= clock_get_elapsed_ns() * 0x2545'F491'4F6C'DD1D;
+    z = (z ^ (z >> 30)) * 0xBF58'476D'1CE4'E5B9;
+    z = (z ^ (z >> 27)) * 0x94D0'49BB'1331'11EB;
+    *out = z ^ (z >> 31);
+    return true;
+}
+
+static struct random_source fallback_source = {
+    .name = "fallback",
+    .quality = 0,
+    .get_u64 = dumb_random,
+};
+
+static _Atomic(struct random_source*) active_source = &fallback_source;
+static struct spinlock lock = {};
+
+bool random_register(struct random_source* source) {
+    spin_lock(&lock);
+
+    struct random_source* active = atomic_load(&active_source, ATOMIC_RELAXED);
+    if (source->quality <= active->quality) {
+        spin_unlock(&lock);
+        return false;
+    }
+    atomic_store(&active_source, source, ATOMIC_RELEASE);
+
+    spin_unlock(&lock);
+
+    log("Switching to random source \"%s\"\n", source->name);
+
+    return true;
+}
+
+void random_fill(void* buf, size_t len) {
+    struct random_source* source = atomic_load(&active_source, ATOMIC_ACQUIRE);
+    uint8_t* out = buf;
+    while (len) {
+        uint64_t value;
+        source->get_u64(source, &value);
+
+        const size_t chunk = len < sizeof(value) ? len : sizeof(value);
+        memcpy(out, &value, chunk);
+        out += chunk;
+        len -= chunk;
+    }
+}
+
+INIT_TASK(random_stage, "core.random");