misc: add hook structure

The hook structure can be used to provide a central hook where other
subsystems can register callbacks.

Signed-off-by: David Herrmann <dh.herrmann@googlemail.com>

src/misc.c

@@ -34,6 +34,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <string.h>
+#include "misc.h"
 
 #define RING_SIZE 512
 
@@ -164,3 +165,104 @@ next:
 		ent->len -= len;
 	}
 }
+
+struct hook_entry {
+	struct hook_entry *next;
+	kmscon_hook_cb cb;
+	void *data;
+};
+
+struct kmscon_hook {
+	struct hook_entry *entries;
+	struct hook_entry *cur_entry;
+};
+
+int kmscon_hook_new(struct kmscon_hook **out)
+{
+	struct kmscon_hook *hook;
+
+	if (!out)
+		return -EINVAL;
+
+	hook = malloc(sizeof(*hook));
+	if (!hook)
+		return -ENOMEM;
+	memset(hook, 0, sizeof(*hook));
+
+	*out = hook;
+	return 0;
+}
+
+void kmscon_hook_free(struct kmscon_hook *hook)
+{
+	struct hook_entry *entry;
+
+	if (!hook)
+		return;
+
+	while ((entry = hook->entries)) {
+		hook->entries = entry->next;
+		free(entry);
+	}
+
+	free(hook);
+}
+
+int kmscon_hook_add(struct kmscon_hook *hook, kmscon_hook_cb cb, void *data)
+{
+	struct hook_entry *entry;
+
+	if (!hook || !cb)
+		return -EINVAL;
+
+	entry = malloc(sizeof(*entry));
+	if (!entry)
+		return -ENOMEM;
+	memset(entry, 0, sizeof(*entry));
+	entry->cb = cb;
+	entry->data = data;
+
+	entry->next = hook->entries;
+	hook->entries = entry;
+	return 0;
+}
+
+void kmscon_hook_rm(struct kmscon_hook *hook, kmscon_hook_cb cb)
+{
+	struct hook_entry *entry, *tmp;
+
+	if (!hook || !cb || !hook->entries)
+		return;
+
+	tmp = NULL;
+	if (hook->entries->cb == cb) {
+		tmp = hook->entries;
+		hook->entries = tmp->next;
+	} else for (entry = hook->entries; entry->next; entry = entry->next) {
+		if (entry->next->cb == cb) {
+			tmp = entry->next;
+			entry->next = tmp->next;
+			break;
+		}
+	}
+
+	if (tmp) {
+		/* if *_call() is currently running we must not disturb it */
+		if (hook->cur_entry == tmp)
+			hook->cur_entry = tmp->next;
+		free(tmp);
+	}
+}
+
+void kmscon_hook_call(struct kmscon_hook *hook, void *parent, void *arg)
+{
+	if (!hook)
+		return;
+
+	hook->cur_entry = hook->entries;
+	while (hook->cur_entry) {
+		hook->cur_entry->cb(parent, arg, hook->cur_entry->data);
+		if (hook->cur_entry)
+			hook->cur_entry = hook->cur_entry->next;
+	}
+}

src/misc.h

@@ -45,4 +45,17 @@ int kmscon_ring_write(struct kmscon_ring *ring, const char *val, size_t len);
 const char *kmscon_ring_peek(struct kmscon_ring *ring, size_t *len);
 void kmscon_ring_drop(struct kmscon_ring *ring, size_t len);
 
+struct kmscon_hook;
+typedef void (*kmscon_hook_cb) (void *parent, void *arg, void *data);
+
+int kmscon_hook_new(struct kmscon_hook **out);
+void kmscon_hook_free(struct kmscon_hook *hook);
+int kmscon_hook_add(struct kmscon_hook *hook, kmscon_hook_cb cb, void *data);
+void kmscon_hook_rm(struct kmscon_hook *hook, kmscon_hook_cb cb);
+void kmscon_hook_call(struct kmscon_hook *hook, void *parent, void *arg);
+#define kmscon_hook_add_cast(hook, cb, data) \
+	kmscon_hook_add((hook), (kmscon_hook_cb)(cb), (data))
+#define kmscon_hook_rm_cast(hook, cb) \
+	kmscon_hook_rm((hook), (kmscon_hook_cb)(cb))
+
 #endif /* KMSCON_MISC_H */