From e4257284ad9762bea8a4c06f6612e380525659f6 Mon Sep 17 00:00:00 2001
From: Kaspar Schleiser <kaspar@schleiser.de>
Date: Thu, 11 Sep 2014 13:31:39 +0200
Subject: [PATCH] sys: lib: introduce ringbuffer_remove()

This commit adds a function that deletes n elements from the ringbuffer
without actually writing them somewhere.
---
 sys/include/ringbuffer.h |  8 ++++++++
 sys/lib/ringbuffer.c     | 19 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/sys/include/ringbuffer.h b/sys/include/ringbuffer.h
index af8c20e419..8641c318ed 100644
--- a/sys/include/ringbuffer.h
+++ b/sys/include/ringbuffer.h
@@ -86,6 +86,14 @@ int ringbuffer_get_one(ringbuffer_t *restrict rb);
  */
 unsigned ringbuffer_get(ringbuffer_t *restrict rb, char *buf, unsigned n);
 
+/**
+ * @brief           Remove a number of elements from the ringbuffer.
+ * @param[in,out]   rb    Ringbuffer to operate on.
+ * @param[in]       n     Read at most n elements.
+ * @returns         Number of elements actually removed.
+ */
+unsigned ringbuffer_remove(ringbuffer_t *restrict rb, unsigned n);
+
 /**
  * @brief           Test if the ringbuffer is empty.
  * @param[in,out]   rb    Ringbuffer to operate on.
diff --git a/sys/lib/ringbuffer.c b/sys/lib/ringbuffer.c
index 8cdcc02f41..2e7a14ca98 100644
--- a/sys/lib/ringbuffer.c
+++ b/sys/lib/ringbuffer.c
@@ -102,6 +102,25 @@ unsigned ringbuffer_get(ringbuffer_t *restrict rb, char *buf, unsigned n)
     return n;
 }
 
+unsigned ringbuffer_remove(ringbuffer_t *restrict rb, unsigned n)
+{
+    if (n > rb->avail) {
+        n = rb->avail;
+        rb->start = rb->avail = 0;
+    }
+    else {
+        rb->start -= n;
+        rb->avail -= n;
+
+        /* compensate underflow */
+        if (rb->start > rb->size) {
+            rb->start += rb->size;
+        }
+    }
+
+    return n;
+}
+
 int ringbuffer_peek_one(const ringbuffer_t *restrict rb_)
 {
     ringbuffer_t rb = *rb_;