From 19e0195be3599e5b3ef3061d323fc95629f465ab Mon Sep 17 00:00:00 2001
From: =?utf8?q?Janosch=20Gr=C3=A4f?= <janosch@majestix.majestix>
Date: Thu, 25 Dec 2008 02:39:23 +0100
Subject: [PATCH] libmeinos: +ringbuf

---
 apps/include/ringbuf.h       | 18 ++++++++++++
 apps/lib/libmeinos/ringbuf.c | 67 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 85 insertions(+)
 create mode 100644 apps/include/ringbuf.h
 create mode 100644 apps/lib/libmeinos/ringbuf.c

diff --git a/apps/include/ringbuf.h b/apps/include/ringbuf.h
new file mode 100644
index 0000000..a483e8d
--- /dev/null
+++ b/apps/include/ringbuf.h
@@ -0,0 +1,18 @@
+#ifndef _RINGBUF_H_
+#define _RINGBUF_H_
+
+#include <sys/types.h>
+
+typedef struct {
+  void *buf;
+  size_t size;
+  size_t rpos;
+  size_t wpos;
+} ringbuf_t;
+
+ringbuf_t *ringbuf_create(size_t size);
+void ringbuf_destroy(ringbuf_t *ringbuf);
+size_t ringbuf_read(ringbuf_t *ringbuf,void *buf,size_t size);
+size_t ringbuf_write(ringbuf_t *ringbuf,const void *buf,size_t size);
+
+#endif /* _RINGBUF_H_ */
diff --git a/apps/lib/libmeinos/ringbuf.c b/apps/lib/libmeinos/ringbuf.c
new file mode 100644
index 0000000..b7e43df
--- /dev/null
+++ b/apps/lib/libmeinos/ringbuf.c
@@ -0,0 +1,67 @@
+#include <ringbuf.h>
+#include <stdlib.h>
+#include <sys/types.h>
+
+ringbuf_t *ringbuf_create(size_t size) {
+  ringbuf_t *ringbuf = malloc(sizeof(ringbuf_t));
+  ringbuf->buf = malloc(size);
+  ringbuf->size = size;
+  ringbuf->wpos = 0;
+  ringbuf->rpos = 0;
+  return ringbuf;
+}
+
+void ringbuf_destroy(ringbuf_t *ringbuf) {
+  free(ringbuf->buf);
+  free(ringbuf);
+}
+
+size_t ringbuf_read(ringbuf_t *ringbuf,void *buf,size_t size) {
+  // calculate free size
+  size_t size_free = ringbuf->wpos>=ringbuf->rpos?ringbuf->wpos-ringbuf->rpos:ringbuf->wpos+ringbuf->size-ringbuf->rpos;
+
+  // check if buffer is big enough
+  if (size>size_free) size = size_free;
+  if (size==0) return 0;
+
+  // if isn't wrapped around at end just copy
+  /// @todo Check this line
+  if (ringbuf->rpos+size<ringbuf->size) memcpy(buf,ringbuf->buf+ringbuf->rpos,size);
+  // else you have to do 2 copies
+  else {
+    size_t part1 = ringbuf->size-ringbuf->rpos;
+    size_t part2 = size-part1;
+    memcpy(buf,ringbuf->buf+ringbuf->rpos,part1);
+    memcpy(buf+part1,ringbuf->buf,part2);
+  }
+
+  // update read position
+  ringbuf->rpos = (ringbuf->rpos+size)%ringbuf->size;
+
+  return size;
+}
+
+size_t ringbuf_write(ringbuf_t *ringbuf,const void *buf,size_t size) {
+  // calculate free size
+  size_t size_free = ringbuf->rpos>ringbuf->wpos?ringbuf->rpos-ringbuf->wpos:ringbuf->rpos+ringbuf->size-ringbuf->rpos;
+
+  // check if buffer is big enough
+  if (size>size_free) size = size_free;
+  if (size==0) return 0;
+
+  // if isn't be wrapped around at end just copy
+  /// @todo Check this line
+  if (ringbuf->rpos+size<ringbuf->size) memcpy(ringbuf->buf+ringbuf->wpos,buf,size);
+  // else you have to do 2 copies
+  else {
+    size_t part1 = ringbuf->size-ringbuf->wpos;
+    size_t part2 = size-part1;
+    memcpy(ringbuf->buf+ringbuf->wpos,buf,part1);
+    memcpy(ringbuf->buf,buf+part1,part2);
+  }
+
+  // update read position
+  ringbuf->wpos = (ringbuf->wpos+size)%ringbuf->size;
+
+  return size;
+}
-- 
2.11.4.GIT