From d3e265121290f0775337e2a237c39ebb9038684c Mon Sep 17 00:00:00 2001
From: giomba <giomba@glgprograms.it>
Date: Sun, 22 Oct 2023 11:39:02 +0200
Subject: [PATCH] Add linear feedback shift register to generate "random"
 numbers.

---
 src/lfsr.c | 14 ++++++++++++++
 src/lfsr.h | 14 ++++++++++++++
 2 files changed, 28 insertions(+)
 create mode 100644 src/lfsr.c
 create mode 100644 src/lfsr.h

diff --git a/src/lfsr.c b/src/lfsr.c
new file mode 100644
index 0000000..d3378d0
--- /dev/null
+++ b/src/lfsr.c
@@ -0,0 +1,14 @@
+#include "lfsr.h"
+
+void lfsr_init(Lfsr *ctx, uint16_t init) {
+    ctx->lfsr = init;
+    ctx->bit = 0;
+}
+
+uint16_t lfsr_next(Lfsr *ctx) {
+    ctx->bit = ((ctx->lfsr >> 0) ^ (ctx->lfsr >> 2) ^ (ctx->lfsr >> 3) ^
+                (ctx->lfsr >> 5)) &
+               1U;
+    ctx->lfsr = (ctx->lfsr >> 1) | (ctx->bit << 15);
+    return ctx->lfsr;
+}
diff --git a/src/lfsr.h b/src/lfsr.h
new file mode 100644
index 0000000..6cd3770
--- /dev/null
+++ b/src/lfsr.h
@@ -0,0 +1,14 @@
+#ifndef LFSR_H
+#define LFSR_H
+
+#include <stdint.h>
+
+typedef struct Lfsr {
+    uint16_t lfsr;
+    uint16_t bit;
+} Lfsr;
+
+void lfsr_init(Lfsr *ctx, uint16_t init);
+uint16_t lfsr_next(Lfsr *ctx);
+
+#endif // LFSR_H