X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=buffer_tree.c;h=4aeb790a6e3c6e8efe9a841e4b12fbe331f360f9;hp=aff03444cc8cc3d0181812fc677c03bfa132e3b0;hb=3741aebd97c1b370f4e783dd6d82dd9e690195a8;hpb=ecd2ef112f101a03dda582401d58080cd7c7c43d

diff --git a/buffer_tree.c b/buffer_tree.c
index aff03444..4aeb790a 100644
--- a/buffer_tree.c
+++ b/buffer_tree.c
@@ -57,8 +57,7 @@ struct btr_node {
  * Create a new buffer pool.
  *
  * \param name The name of the new buffer pool.
- *
- * \param area The size in bytes of the pool area.
+ * \param area_size The size in bytes of the pool area.
  *
  * \return An opaque pointer to the newly created buffer pool. It must be
  * passed to btr_pool_free() after it is no longer used to deallocate all
@@ -79,7 +78,7 @@ struct btr_pool *btr_pool_new(const char *name, size_t area_size)
 }
 
 /**
- * Dellocate resources used by a buffer pool.
+ * Deallocate resources used by a buffer pool.
  *
  * \param btrp A pointer obtained via btr_pool_new().
  */
@@ -105,7 +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);
@@ -135,7 +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;
@@ -222,9 +221,9 @@ static void btr_pool_deallocate(struct btr_pool *btrp, size_t size)
  *
  * \param bnd Specifies how to create the new node.
  *
- * This function always succeeds (or calls exit()). The returned pointer
- * must be freed using btr_free_node() after it has been removed from
- * the buffer tree via btr_remove_node().
+ * This function always succeeds (or calls exit()). The returned pointer must
+ * be freed using btr_free_node() after the node has been removed from the
+ * buffer tree via btr_remove_node().
  */
 struct btr_node *btr_new_node(struct btr_node_description *bnd)
 {
@@ -424,6 +423,17 @@ static void btr_pushdown_br(struct btr_buffer_reference *br, struct btr_node *bt
 	btr_drop_buffer_reference(br);
 }
 
+/**
+ * Feed all buffer references of the input queue through the output channel.
+ *
+ * \param btrn The node whose buffer references should be pushed down.
+ *
+ * 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)
 {
 	struct btr_buffer_reference *br, *tmp;
@@ -432,15 +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;
 }
 
 /*
@@ -470,6 +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)
@@ -482,7 +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;
@@ -596,6 +631,11 @@ static void flush_input_queue(struct btr_node *btrn)
 		btr_drop_buffer_reference(br);
 }
 
+/**
+ * Free all resources allocated by btr_new_node().
+ *
+ * Like free(3), it is OK to call this with a \p NULL pointer argument.
+ */
 void btr_free_node(struct btr_node *btrn)
 {
 	if (!btrn)
@@ -604,6 +644,17 @@ void btr_free_node(struct btr_node *btrn)
 	free(btrn);
 }
 
+/**
+ * Remove a node from a buffer tree.
+ *
+ * \param btrn The node to remove.
+ *
+ * This makes all child nodes of \a btrn orphans and removes \a btrn from the
+ * list of children of its parent. Moreover, the input queue of \a btrn is
+ * flushed if it is not empty.
+ *
+ * \sa \ref btr_splice_out_node.
+ */
 void btr_remove_node(struct btr_node *btrn)
 {
 	struct btr_node *ch;
@@ -646,6 +697,17 @@ size_t btr_get_input_queue_size(struct btr_node *btrn)
 	return size;
 }
 
+/**
+ * Remove a node from the buffer tree, reconnecting parent and children.
+ *
+ * \param btrn The node to splice out.
+ *
+ * This function is used by buffer tree nodes that do not exist during the
+ * whole lifetime of the buffer tree. Unlike btr_remove_node(), calling
+ * btr_splice_out_node() does not split the tree into disconnected components
+ * but reconnects the buffer tree by making all child nodes of \a btrn children
+ * of the parent of \a btrn.
+ */
 void btr_splice_out_node(struct btr_node *btrn)
 {
 	struct btr_node *ch, *tmp;
@@ -665,7 +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.
@@ -692,7 +754,18 @@ int btr_exec(struct btr_node *btrn, const char *command, char **value_result)
 }
 
 /**
- * Execute a inter-node command.
+ * Execute a inter-node command on a parent node.
+ *
+ * \param btrn The node to start looking.
+ * \param command The command to execute.
+ * \param value_result Additional arguments and result value.
+ *
+ * This function traverses the buffer tree upwards and looks for parent nodes
+ * of \a btrn that understands \a command. On the first such node the command
+ * is executed, and the result is stored in \a value_result.
+ *
+ * \return \p -ENOTSUP if no parent node of \a btrn understands \a command.
+ * Otherwise the return value of the command handler is returned.
  */
 int btr_exec_up(struct btr_node *btrn, const char *command, char **value_result)
 {
@@ -718,6 +791,14 @@ int btr_exec_up(struct btr_node *btrn, const char *command, char **value_result)
 	return -ERRNO_TO_PARA_ERROR(ENOTSUP);
 }
 
+/**
+ * Obtain the context of a buffer node tree.
+ *
+ * The returned pointer equals the context pointer used at creation time of the
+ * node.
+ *
+ * \sa btr_new_node(), struct \ref btr_node_description.
+ */
 void *btr_context(struct btr_node *btrn)
 {
 	return btrn->context;
@@ -869,6 +950,20 @@ static int merge_input(struct btr_node *btrn)
 	return 2;
 }
 
+/**
+ * Combine input queue buffers.
+ *
+ * \param btrn The buffer tree node whose input should be merged.
+ * \param dest_size Stop merging if a buffer of at least this size exists.
+ *
+ * Used to combine as many buffers as needed into a single buffer whose size is
+ * at least \a dest_size. This function is rather cheap in case the parent node
+ * uses buffer pools and rather expensive otherwise.
+ *
+ * Note that if less than \a dest_size bytes are available in total, this
+ * function does nothing and subsequent calls to btr_next_buffer() will still
+ * return a buffer size less than \a dest_size.
+ */
 void btr_merge(struct btr_node *btrn, size_t dest_size)
 {
 	if (need_buffer_pool_merge(btrn))
@@ -884,7 +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);
@@ -892,7 +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;
@@ -904,13 +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)
 {
@@ -931,6 +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)
 {
@@ -955,6 +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;