From 20a73af374aa038d85a9324cdb65f96d24f487a3 Mon Sep 17 00:00:00 2001
From: Krzosa Karol <krzosa@proton.me>
Date: Sun, 5 Jan 2025 14:57:28 +0100
Subject: [PATCH] core_random, default_is_invalid

---
 src/core/core_inc.c    |  3 ++-
 src/core/core_log.h    |  1 +
 src/core/core_random.c | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 src/core/core_random.c

diff --git a/src/core/core_inc.c b/src/core/core_inc.c
index 5f92bcc..764ccaf 100644
--- a/src/core/core_inc.c
+++ b/src/core/core_inc.c
@@ -43,4 +43,5 @@
 #include "core_string.c"
 #include "core_log.c"
 #include "core_lexer.c"
-#include "core_type_info.c"
\ No newline at end of file
+#include "core_type_info.c"
+#include "core_random.c"
\ No newline at end of file
diff --git a/src/core/core_log.h b/src/core/core_log.h
index 704f0a2..042fb22 100644
--- a/src/core/core_log.h
+++ b/src/core/core_log.h
@@ -66,6 +66,7 @@ fn void default_log_proc(log_event_t ev);
 #endif
 #define not_implemented assert(!"not implemented!")
 #define invalid_codepath assert(!"invalid code path!")
+#define default_is_invalid default: assert(!"invalid default case")
 
 
 
diff --git a/src/core/core_random.c b/src/core/core_random.c
new file mode 100644
index 0000000..3a3db9e
--- /dev/null
+++ b/src/core/core_random.c
@@ -0,0 +1,35 @@
+typedef struct random_seed_t random_seed_t;
+struct random_seed_t {
+    u64 a;
+};
+
+// xorshift64
+u64 get_random_u64(random_seed_t *seed) {
+    u64 x = seed->a;
+    x ^= x << 13;
+    x ^= x >> 7;
+    x ^= x << 17;
+    return seed->a = x;
+}
+
+u64 get_random_in_range_u64(random_seed_t *seed, u64 start, u64 one_past_end) {
+    u64 r    = get_random_u64(seed);
+    u64 diff = one_past_end - start;
+    u64 rr   = r % diff;
+    u64 rrr  = rr + start;
+    return rrr;
+}
+
+i64 get_random_in_range_i64(random_seed_t *seed, i64 start, i64 one_past_end) {
+    u64 r    = get_random_u64(seed);
+    i64 diff = one_past_end - start;
+    u64 rr   = r % diff;
+    i64 rrr  = (i64)rr + start;
+    return rrr;
+}
+
+f64 get_random_f64(random_seed_t *seed) {
+    f64 random = (f64)get_random_in_range_u64(seed, 0, UINT32_MAX);
+    f64 result = random / (f64)(UINT32_MAX - 1u);
+    return result;
+}
\ No newline at end of file