[alsa-devel] [PATCH][RFC][alsa-utils 5/9] alsactl: use link list to maintain source of events

[Takashi Sakamoto]

At present, handlers for control nodes are maintained by one-dimensional
array. This is not necessarily useful to maintain handlers with
associated information.

This commit adds link-list for the maintenance.

Signed-off-by: Takashi Sakamoto <o-takashi at sakamocchi.jp>
---
 alsactl/monitor.c | 84 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)

diff --git a/alsactl/monitor.c b/alsactl/monitor.c
index cf5c50a..8b16307 100644
--- a/alsactl/monitor.c
+++ b/alsactl/monitor.c
@@ -29,6 +29,16 @@
 static int signal_type;
 static bool interrupted;
 
+struct src_entry {
+	snd_ctl_t *handle;
+	char *name;
+	unsigned int pfd_count;
+	struct {
+		struct src_entry *prev;
+		struct src_entry *next;
+	} list;
+};
+
 #define MAX_CARDS	256
 
 struct snd_card_iterator {
@@ -59,6 +69,72 @@ static const char *snd_card_iterator_next(struct snd_card_iterator *iter)
         return (const char *)iter->name;
 }
 
+static inline void remove_source_entry(struct src_entry *src)
+{
+	struct src_entry *prev = src->list.prev;
+	struct src_entry *next = src->list.next;
+
+	if (prev)
+		prev->list.next = src->list.next;
+	if (next)
+		next->list.prev = src->list.prev;
+	free(src->name);
+	free(src);
+}
+
+static void clear_source_list(struct src_entry **srcs)
+{
+	while (*srcs) {
+		struct src_entry *src = *srcs;
+		*srcs = src->list.next;
+
+		remove_source_entry(src);
+	}
+}
+
+static int insert_source_entry(struct src_entry **head, snd_ctl_t *handle,
+			       const char *name)
+{
+	struct src_entry *src;
+	int count;
+	int err;
+
+	src = calloc(1, sizeof(*src));
+	if (!src)
+		return -ENOMEM;
+	src->handle = handle;
+
+	src->name = strdup(name);
+	if (!src->name) {
+		err = -ENOMEM;
+		goto error;
+	}
+
+	count = snd_ctl_poll_descriptors_count(handle);
+	if (count < 0) {
+		err = count;
+		goto error;
+	}
+	if (count == 0) {
+		err = -ENXIO;
+		goto error;
+	}
+	src->pfd_count = count;
+
+	if (*head) {
+		src->list.next = (*head)->list.next;
+		src->list.prev = *head;
+		(*head)->list.next = src;
+	} else {
+		*head = src;
+	}
+
+	return 0;
+error:
+	free(src);
+	return err;
+}
+
 static int open_ctl(const char *name, snd_ctl_t **ctlp)
 {
 	snd_ctl_t *ctl;
@@ -259,6 +335,7 @@ static int prepare_signal_handler(void)
 
 int monitor(const char *name)
 {
+	struct src_entry *srcs = NULL;
 	snd_ctl_t *ctls[MAX_CARDS] = {0};
 	int ncards = 0;
 	int show_cards;
@@ -281,6 +358,9 @@ int monitor(const char *name)
 		snd_card_iterator_init(&iter);
 		while ((cardname = snd_card_iterator_next(&iter))) {
 			err = open_ctl(cardname, &ctls[ncards]);
+			if (err < 0)
+				goto error;
+			err = insert_source_entry(&srcs, ctls[ncards], cardname);
 			if (err < 0)
 				goto error;
 			++ncards;
@@ -288,6 +368,9 @@ int monitor(const char *name)
 		show_cards = 1;
 	} else {
 		err = open_ctl(name, &ctls[0]);
+		if (err < 0)
+			goto error;
+		err = insert_source_entry(&srcs, ctls[ncards], name);
 		if (err < 0)
 			goto error;
 		ncards++;
@@ -300,6 +383,7 @@ int monitor(const char *name)
 	clear_dispatcher(epfd, ctls, ncards);
 
 error:
+	clear_source_list(&srcs);
 	for (i = 0; i < ncards; i++) {
 		if (ctls[i])
 			snd_ctl_close(ctls[i]);
-- 
2.19.0