From 9d87c925a9eaa4fc256be3173c14a20d1469472d Mon Sep 17 00:00:00 2001
From: fishsoupisgood <github@madingley.org>
Date: Wed, 9 Sep 2020 11:53:37 +0100
Subject: everything, mostly, working

---
 radiator-plc/stm32/app/ring.c | 69 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)
 create mode 100644 radiator-plc/stm32/app/ring.c

(limited to 'radiator-plc/stm32/app/ring.c')

diff --git a/radiator-plc/stm32/app/ring.c b/radiator-plc/stm32/app/ring.c
new file mode 100644
index 0000000..c1d1803
--- /dev/null
+++ b/radiator-plc/stm32/app/ring.c
@@ -0,0 +1,69 @@
+#include "project.h"
+
+
+static inline size_t
+ring_next (ring_t *r, size_t p)
+{
+  p++;
+
+  if (p >= r->size)
+    p -= r->size;
+
+  return p;
+}
+
+void
+ring_init (ring_t *r, uint8_t *buf, size_t len)
+{
+  r->data = buf;
+  r->size = len;
+  r->write = 0;
+  r->read = 0;
+}
+
+int
+ring_write_byte (ring_t *r, uint8_t c)
+{
+  size_t n = ring_next (r, r->write);
+
+  if (n == r->read)
+    return -1;
+
+  r->data[r->write] = c;
+
+  r->write = n;
+
+  return 0;
+}
+
+
+int
+ring_read_byte (ring_t *r, uint8_t *c)
+{
+  size_t n = ring_next (r, r->read);
+
+  if (r->read == r->write)
+    return -1;
+
+  *c = r->data[r->read];
+  r->read = n;
+
+  return 0;
+}
+
+int
+ring_write (ring_t *r, uint8_t *buf, size_t len)
+{
+  while (len--) {
+    if (ring_write_byte (r, * (buf++)))
+      return -1;
+  }
+
+  return 0;
+}
+
+int
+ring_empty (ring_t *r)
+{
+  return (r->read == r->write) ? 1 : 0;
+}
-- 
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