ringbuffer: add documentation

sys/include/ringbuffer.h

@@ -19,30 +19,98 @@
 #ifndef __RINGBUFFER_H
 #define __RINGBUFFER_H
 
+/**
+ * @brief     Ringbuffer.
+ * @details   Non thread-safe FIFO ringbuffer implementation around a `char` array.
+ */
 typedef struct ringbuffer {
-    char *buf;
-    unsigned int size;
-    unsigned int start;
-    unsigned int avail;
+    char *buf;          /**< Buffer to operate on. */
+    unsigned int size;  /**< Size of buf. */
+    unsigned int start; /**< Current read position in the ring buffer. */
+    unsigned int avail; /**< Number of elements available for reading. */
 } ringbuffer_t;
 
+/**
+ * @brief        Initialize a ringbuffer.
+ * @param[out]   rb        Datum to initialize.
+ * @param[in]    buffer    Buffer to use by rb.
+ * @param[in]    bufsize   `sizeof (buffer)`
+ */
 void ringbuffer_init(ringbuffer_t *restrict rb, char *buffer, unsigned bufsize);
+
+/**
+ * @brief           Add an element to the ringbuffer.
+ * @details         If rb is full, then the oldest element gets overwritten.
+ *                  Test ringbuffer_full() first if overwriting is not intended.
+ * @param[in,out]   rb   Ringbuffer to operate on.
+ * @param[in]       c    Element to add.
+ * @returns         The element that was dropped, iff the buffer was full.
+ *                  -1 iff the buffer was not full.
+ */
 int ringbuffer_add_one(ringbuffer_t *restrict rb, char c);
+
+/**
+ * @brief           Add a number of elements to the ringbuffer.
+ * @details         Only so many elements are added as fit in the ringbuffer.
+ *                  No elements get overwritten.
+ *                  If this is not the intended behavior, then use ringbuffer_add_one() in a loop instead.
+ * @param[in,out]   rb    Ringbuffer to operate on.
+ * @param[in]       buf   Buffer to add elements from.
+ * @param[in]       n     Maximum number of elements to add.
+ * @returns         Number of elements actually added. 0 if rb is full.
+ */
 unsigned ringbuffer_add(ringbuffer_t *restrict rb, const char *buf, unsigned n);
+
+/**
+ * @brief           Peek and remove oldest element from the ringbuffer.
+ * @param[in,out]   rb   Ringbuffer to operate on.
+ * @returns         The oldest element that was added, or `-1` if rb is empty.
+ */
 int ringbuffer_get_one(ringbuffer_t *restrict rb);
+
+/**
+ * @brief           Read and remove a number of elements from the ringbuffer.
+ * @param[in,out]   rb    Ringbuffer to operate on.
+ * @param[out]      buf   Buffer to write into.
+ * @param[in]       n     Read at most n elements.
+ * @returns         Number of elements actually read.
+ */
 unsigned ringbuffer_get(ringbuffer_t *restrict rb, char *buf, unsigned n);
 
+/**
+ * @brief           Test if the ringbuffer is empty.
+ * @param[in,out]   rb    Ringbuffer to operate on.
+ * @returns         0 iff not empty
+ */
 static inline int ringbuffer_empty(const ringbuffer_t *restrict rb)
 {
     return rb->avail == 0;
 }
 
+/**
+ * @brief           Test if the ringbuffer is full.
+ * @param[in,out]   rb    Ringbuffer to operate on.
+ * @returns         0 iff not full
+ */
 static inline int ringbuffer_full(const ringbuffer_t *restrict rb)
 {
     return rb->avail == rb->size;
 }
 
+/**
+ * @brief           Read, but don't remove, the oldest element in the buffer.
+ * @param[in]       rb    Ringbuffer to operate on.
+ * @returns         Same as ringbuffer_get_one()
+ */
 int ringbuffer_peek_one(const ringbuffer_t *restrict rb);
+
+/**
+ * @brief           Read, but don't remove, the a number of element of the buffer.
+ * @param[in]       rb    Ringbuffer to operate on.
+ * @param[out]      buf   Buffer to write into.
+ * @param[in]       n     Read at most n elements.
+ * @returns         Same as ringbuffer_get()
+ */
 unsigned ringbuffer_peek(const ringbuffer_t *restrict rb, char *buf, unsigned n);
 
 #endif /* __RINGBUFFER_H */

sys/lib/ringbuffer.c

@@ -26,6 +26,13 @@ void ringbuffer_init(ringbuffer_t *restrict rb, char *buffer, unsigned bufsize)
     rb->avail = 0;
 }
 
+/**
+ * @brief           Add an element to the end of the ringbuffer.
+ * @details         This helper function does not check the pre-requirements for adding,
+ *                  i.e. the caller has to ensure that ringbuffer_full() is false.
+ * @param[in,out]   rb   Ringbuffer to operate on.
+ * @param[in]       c    Element to add.
+ */
 static void add_tail(ringbuffer_t *restrict rb, char c)
 {
     unsigned pos = rb->start + rb->avail++;
@@ -35,6 +42,13 @@ static void add_tail(ringbuffer_t *restrict rb, char c)
     rb->buf[pos] = c;
 }
 
+/**
+ * @brief           Remove an element from the start of the ringbuffer.
+ * @details         This helper function does not check the pre-requirements for reading,
+ *                  i.e. the caller has to ensure that ringbuffer_empty() is false.
+ * @param[in,out]   rb   Ringbuffer to operate on.
+ * @returns         The removed element.
+ */
 static char get_head(ringbuffer_t *restrict rb)
 {
     char result = rb->buf[rb->start];