From: Andre Noll <maan@systemlinux.org>
Date: Tue, 19 Jan 2010 11:38:29 +0000 (+0100)
Subject: [btr] Complete source code documentation.
X-Git-Tag: v0.4.2~72
X-Git-Url: http://git.tue.mpg.de/?a=commitdiff_plain;h=a09516998f148e8892bb8665ffe3dcf58ac7e5c5;p=paraslash.git

[btr] Complete source code documentation.
---

diff --git a/buffer_tree.c b/buffer_tree.c
index 201fb0b0..4aeb790a 100644
--- a/buffer_tree.c
+++ b/buffer_tree.c
@@ -104,7 +104,7 @@ size_t btr_pool_size(struct btr_pool *btrp)
 	return btrp->area_end - btrp->area_start;
 }
 
-size_t btr_pool_filled(struct btr_pool *btrp)
+static size_t btr_pool_filled(struct btr_pool *btrp)
 {
 	if (!btrp->whead)
 		return btr_pool_size(btrp);
@@ -134,7 +134,7 @@ size_t btr_pool_unused(struct btr_pool *btrp)
  * Return maximal size available for one read. This is
  * smaller than the value returned by btr_pool_unused().
  */
-size_t btr_pool_available(struct btr_pool *btrp)
+static size_t btr_pool_available(struct btr_pool *btrp)
 {
 	if (!btrp->whead)
 		return 0;
@@ -431,6 +431,8 @@ static void btr_pushdown_br(struct btr_buffer_reference *br, struct btr_node *bt
  * This function is useful for filters that do not change the contents of the
  * buffers at all, like the wav filter or the amp filter if no amplification
  * was specified. This function is rather cheap.
+ *
+ * \sa \ref btr_pushdown_one().
  */
 void btr_pushdown(struct btr_node *btrn)
 {
@@ -440,15 +442,22 @@ void btr_pushdown(struct btr_node *btrn)
 		btr_pushdown_br(br, btrn);
 }
 
-int btr_pushdown_one(struct btr_node *btrn)
+/**
+ * Feed the next buffer of the input queue through the output channel.
+ *
+ * \param btrn The node whose first input queue buffer should be pushed down.
+ *
+ * This works like \ref btr_pushdown() but pushes down only one buffer
+ * reference.
+ */
+void btr_pushdown_one(struct btr_node *btrn)
 {
 	struct btr_buffer_reference *br;
 
 	if (list_empty(&btrn->input_queue))
-		return 0;
+		return;
 	br = list_first_entry(&btrn->input_queue, struct btr_buffer_reference, node);
 	btr_pushdown_br(br, btrn);
-	return 1;
 }
 
 /*
@@ -478,6 +487,24 @@ bool btr_no_parent(struct btr_node *btrn)
 	return !btrn->parent;
 }
 
+/**
+ * Find out whether it is OK to change an input buffer.
+ *
+ * \param btrn The buffer tree node to check.
+ *
+ * This is used by filters that produce exactly the same amount of output as
+ * there is input. The amp filter which multiplies each sample by some number
+ * is an example of such a filter. If there are no other nodes in the buffer
+ * tree that read the same input stream (i.e. if \a btrn has no siblings), a
+ * node may modify its input buffer directly and push down the modified buffer
+ * to its children, thereby avoiding to allocate a possibly large additional
+ * buffer.
+ *
+ * Since the buffer tree may change at any time, this function should be called
+ * during each post_select call.
+ *
+ * \return True if \a btrn has no siblings.
+ */
 bool btr_inplace_ok(struct btr_node *btrn)
 {
 	if (!btrn->parent)
@@ -490,7 +517,7 @@ static inline size_t br_available_bytes(struct btr_buffer_reference *br)
 	return br->btrb->size - br->consumed;
 }
 
-size_t btr_get_buffer_by_reference(struct btr_buffer_reference *br, char **buf)
+static size_t btr_get_buffer_by_reference(struct btr_buffer_reference *br, char **buf)
 {
 	if (buf)
 		*buf = br->btrb->buf + br->consumed;
@@ -700,7 +727,7 @@ void btr_splice_out_node(struct btr_node *btrn)
 	assert(list_empty(&btrn->children));
 }
 
-/**
+/*
  * Return the size of the largest input queue.
  *
  * Iterates over all children of the given node.
@@ -952,7 +979,7 @@ void btr_merge(struct btr_node *btrn, size_t dest_size)
 	}
 }
 
-bool btr_eof(struct btr_node *btrn)
+static bool btr_eof(struct btr_node *btrn)
 {
 	char *buf;
 	size_t len = btr_next_buffer(btrn, &buf);
@@ -960,7 +987,7 @@ bool btr_eof(struct btr_node *btrn)
 	return (len == 0 && btr_no_parent(btrn));
 }
 
-void log_tree_recursively(struct btr_node *btrn, int loglevel, int depth)
+static void log_tree_recursively(struct btr_node *btrn, int loglevel, int depth)
 {
 	struct btr_node *ch;
 	const char spaces[] = "                 ", *space = spaces + 16 - depth;
@@ -972,13 +999,26 @@ void log_tree_recursively(struct btr_node *btrn, int loglevel, int depth)
 		log_tree_recursively(ch, loglevel, depth + 1);
 }
 
+/**
+ * Write the current buffer (sub-)tree to the log.
+ *
+ * \param btrn Start logging at this node.
+ * \param loglevel Set severity with which the tree should be logged.
+ */
 void btr_log_tree(struct btr_node *btrn, int loglevel)
 {
 	return log_tree_recursively(btrn, loglevel, 0);
 }
 
-/*
- * \return \a root if \a name is \p NULL.
+/**
+ * Find the node with the given name in the buffer tree.
+ *
+ * \param name The name of the node to search.
+ * \param root Where to start the search.
+ *
+ * \return A pointer to the node with the given name on success. If \a name is
+ * \p NULL, the function returns \a root. If there is no node with the given
+ * name, \p NULL is returned.
  */
 struct btr_node *btr_search_node(const char *name, struct btr_node *root)
 {
@@ -999,6 +1039,32 @@ struct btr_node *btr_search_node(const char *name, struct btr_node *root)
 /** 640K ought to be enough for everybody ;) */
 #define BTRN_MAX_PENDING (640 * 1024)
 
+/**
+ * Return the current state of a buffer tree node.
+ *
+ * \param btrn The node whose state should be queried.
+ * \param min_iqs The minimal input queue size.
+ * \param type The supposed type of \a btrn.
+ *
+ * Most users of the buffer tree subsystem call this function from both
+ * their pre_select and the post_select methods.
+ *
+ * \return Negative if an error condition was detected, zero if there
+ * is nothing to do and positive otherwise.
+ *
+ * Examples:
+ *
+ * - If a non-root node has no parent and an empty input queue, the function
+ * returns \p -E_BTR_EOF. Similarly, if a non-leaf node has no children, \p
+ * -E_BTR_NO_CHILD is returned.
+ *
+ * - If less than \a min_iqs many bytes are available in the input queue and no
+ * EOF condition was detected, the function returns zero.
+ *
+ * - If there's plenty of data left in the input queue of the children of \a
+ * btrn, the function also returns zero in order to bound the memory usage of
+ * the buffer tree.
+ */
 int btr_node_status(struct btr_node *btrn, size_t min_iqs,
 	enum btr_node_type type)
 {
@@ -1023,6 +1089,14 @@ int btr_node_status(struct btr_node *btrn, size_t min_iqs,
 	return 1;
 }
 
+/**
+ * Get the time of the first I/O for a buffer tree node.
+ *
+ * \param btrn The node whose I/O time should be obtained.
+ * \param tv Result pointer.
+ *
+ * Mainly useful for the time display of para_audiod.
+ */
 void btr_get_node_start(struct btr_node *btrn, struct timeval *tv)
 {
 	*tv = btrn->start;
diff --git a/buffer_tree.h b/buffer_tree.h
index 305fb7d1..e2af2fc8 100644
--- a/buffer_tree.h
+++ b/buffer_tree.h
@@ -188,7 +188,7 @@ void btr_pushdown(struct btr_node *btrn);
 void *btr_context(struct btr_node *btrn);
 void btr_merge(struct btr_node *btrn, size_t dest_size);
 void btr_log_tree(struct btr_node *btrn, int loglevel);
-int btr_pushdown_one(struct btr_node *btrn);
+void btr_pushdown_one(struct btr_node *btrn);
 bool btr_inplace_ok(struct btr_node *btrn);
 int btr_node_status(struct btr_node *btrn, size_t min_iqs,
 		enum btr_node_type type);