Add ring buffer utilities

These are cropping up all over the place in arducontrol.

diff --git a/common/ringbuffer.h b/common/ringbuffer.h
new file mode 100644 (file)
index 0000000..1a03ec5
--- /dev/null
+++ b/common/ringbuffer.h
@@ -0,0 +1,53 @@
+#ifndef RINGBUFFER_H_
+#define RINGBUFFER_H_
+
+#define RINGBUFFER(name, size) uint8_t name[(size)+4] = { size, 0, 0, 0 }
+
+static inline uint8_t ringbuffer_fill(const uint8_t *buffer)
+{
+       return buffer[1];
+}
+
+static inline uint8_t ringbuffer_space(const uint8_t *buffer)
+{
+       return buffer[0]-buffer[1];
+}
+
+static inline void ringbuffer_push(uint8_t *buffer, uint8_t value)
+{
+       const uint8_t size = buffer[0];
+       uint8_t head = buffer[2];
+       buffer[4+head++] = value;
+       if(head>=size)
+               head -= size;
+       buffer[2] = head;
+       ++buffer[1];
+}
+
+static inline void ringbuffer_blocking_push(uint8_t *buffer, uint8_t value)
+{
+       const volatile uint8_t *fill = buffer+1;
+       while(*fill>=buffer[0]) ;
+       ringbuffer_push(buffer, value);
+}
+
+static inline uint8_t ringbuffer_pop(uint8_t *buffer)
+{
+       const uint8_t size = buffer[0];
+       uint8_t tail = buffer[3];
+       uint8_t value = buffer[4+tail++];
+       if(tail>=size)
+               tail -= size;
+       buffer[3] = tail;
+       --buffer[1];
+       return value;
+}
+
+static inline uint8_t rinbuffer_blocking_pop(uint8_t *buffer)
+{
+       const volatile uint8_t *fill = buffer+1;
+       while(*fill==0) ;
+       return ringbuffer_pop(buffer);
+}
+
+#endif