1 files changed, 77 insertions, 0 deletions
diff --git a/boiler-monster/stm32/app/ring.c b/boiler-monster/stm32/app/ring.c
new file mode 100644
index 0000000..973f345
--- /dev/null
+++ b/boiler-monster/stm32/app/ring.c
@@ -0,0 +1,77 @@
+#include "project.h"
+
+
+static inline size_t
+ring_next (volatile ring_t *r, size_t p)
+{
+  p++;
+
+  if (p >= r->size)
+    p -= r->size;
+
+  return p;
+}
+
+void
+ring_init (volatile 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 (volatile ring_t *r, uint8_t c)
+{
+  size_t n = ring_next (r, r->write);
+
+  if (n == r->read)
+    return -EAGAIN;
+
+  r->data[r->write] = c;
+
+  r->write = n;
+
+  return 0;
+}
+
+
+int
+ring_read_byte (volatile ring_t *r, uint8_t *c)
+{
+  size_t n = ring_next (r, r->read);
+
+  if (r->read == r->write)
+    return -EAGAIN;
+
+  *c = r->data[r->read];
+  r->read = n;
+
+  return 0;
+}
+
+int
+ring_write (volatile ring_t *r, uint8_t *buf, size_t len, int blocking)
+{
+  while (len--) {
+    if (blocking) {
+      while (ring_write_byte (r, *buf));
+
+      buf++;
+    } else {
+      if (ring_write_byte (r, * (buf++)))
+        return -EAGAIN;
+    }
+  }
+
+  return 0;
+}
+
+
+
+int
+ring_empty (volatile ring_t *r)
+{
+  return (r->read == r->write) ? 1 : 0;
+}