cbuf: new start/end assignment functions

2 files changed, 35 insertions, 2 deletions

diff --git a/src/cbuf.c b/src/cbuf.c
index 099047a..0f9fd15 100644
--- a/src/cbuf.c
+++ b/src/cbuf.c
@@ -55,12 +55,19 @@ cbuf_index(const struct cbuf *cbuf, size_t abs_index)
 static void
 cbuf_update_start(struct cbuf *cbuf)
 {
-    /* Mind integer overflows */
     if (cbuf_size(cbuf) > cbuf->capacity) {
         cbuf->start = cbuf->end - cbuf->capacity;
     }
 }
 
+static void
+cbuf_update_end(struct cbuf *cbuf)
+{
+    if (cbuf_size(cbuf) > cbuf->capacity) {
+        cbuf->end = cbuf->start + cbuf->capacity;
+    }
+}
+
 int
 cbuf_push(struct cbuf *cbuf, const void *buf, size_t size, bool erase)
 {
@@ -199,3 +206,17 @@ cbuf_read(const struct cbuf *cbuf, size_t index, void *buf, size_t *sizep)
     memcpy(buf, start, size);
     return 0;
 }
+
+void
+cbuf_set_start(struct cbuf *cbuf, size_t start)
+{
+    cbuf->start = start;
+    cbuf_update_start(cbuf);
+}
+
+void
+cbuf_set_end(struct cbuf *cbuf, size_t end)
+{
+    cbuf->end = end;
+    cbuf_update_end(cbuf);
+}
diff --git a/src/cbuf.h b/src/cbuf.h
index 9e4216c..577f57b 100644
--- a/src/cbuf.h
+++ b/src/cbuf.h
@@ -23,7 +23,7 @@
  * http://git.sceen.net/rbraun/librbraun.git/
  *
  *
- * Circular byte buffer.
+ * FIFO circular byte buffer.
  */
 
 #ifndef CBUF_H
@@ -160,4 +160,16 @@ int cbuf_write(struct cbuf *cbuf, size_t index, const void *buf, size_t size);
  */
 int cbuf_read(const struct cbuf *cbuf, size_t index, void *buf, size_t *sizep);
 
+/*
+ * Set the value of the start/end index.
+ *
+ * These functions provide low level access to the circular buffer boundaries
+ * while making sure its size doesn't exceed its capacity.
+ *
+ * Users should try and find a higher level way to manipulate the circular
+ * buffer, and only resort to using these functions if there's no other choice.
+ */
+void cbuf_set_start(struct cbuf *cbuf, size_t start);
+void cbuf_set_end(struct cbuf *cbuf, size_t end);
+
 #endif /* CBUF_H */