From: Mikko Rasa <tdb@tdb.fi>
Date: Wed, 23 Oct 2013 21:02:11 +0000 (+0300)
Subject: Add ring buffer utilities
X-Git-Url: http://git.tdb.fi/?p=model-railway-devices.git;a=commitdiff_plain;h=cd913ccb15a71d793ccd701d3ab8b39a0efeb23a

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
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