From 9c8a163e1a45c42cd6d2fa62affa66d4c969c541 Mon Sep 17 00:00:00 2001
From: Matthias Kruk <m@m10k.eu>
Date: Wed, 19 May 2021 08:03:51 +0900
Subject: [PATCH] loop: Add convenience functions and a foreach function
 without data

This commit adds convenience functions to the loop data type that
allow the caller to find the elements that come before or after an
element in a loop.
This further adds functions to shift the position of an element in
the loop to the back or the front, and a foreach function that
passes only the element pointer to the callback (this is useful for
calling things like free() from the foreach function).
---
 loop.c | 130 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 loop.h |   7 +++-
 2 files changed, 129 insertions(+), 8 deletions(-)

diff --git a/loop.c b/loop.c
index 50370d4..2f74943 100644
--- a/loop.c
+++ b/loop.c
@@ -154,7 +154,29 @@ int loop_find(struct loop **loop, int (*cmp)(void*, void*),
 	return(err);
 }
 
-int loop_foreach(struct loop **loop, int(*func)(void*, void*),
+int loop_foreach(struct loop **loop, void(*func)(void*))
+{
+	struct loop *cur;
+
+	if(!loop) {
+		return(-EINVAL);
+	}
+
+	if(!*loop) {
+		return(0);
+	}
+
+	cur = *loop;
+
+	do {
+		func(cur->data);
+		cur = cur->next;
+	} while(cur != *loop);
+
+	return(0);
+}
+
+int loop_foreach_with_data(struct loop **loop, int(*func)(void*, void*),
 		 void *data)
 {
 	struct loop *cur;
@@ -163,19 +185,19 @@ int loop_foreach(struct loop **loop, int(*func)(void*, void*),
 		return(-EINVAL);
 	}
 
+	if(!*loop) {
+		return(0);
+	}
+
 	cur = *loop;
 
-	while(cur) {
+	do {
 		if(func(cur->data, data) < 0) {
 			break;
 		}
 
 		cur = cur->next;
-
-		if(cur == *loop) {
-			break;
-		}
-	}
+	} while(cur != *loop);
 
 	return(0);
 }
@@ -276,3 +298,97 @@ int loop_get_length(struct loop **loop)
 
 	return(length);
 }
+
+int loop_get_next(struct loop **loop, void *data, void **next)
+{
+	struct loop *iter;
+
+	if(!loop || !data || !next) {
+		return(-EINVAL);
+	}
+
+	if(__loop_find(loop, NULL, data, &iter) < 0) {
+		return(-ENOENT);
+	}
+
+	*next = iter->next->data;
+	return(0);
+}
+
+int loop_get_prev(struct loop **loop, void *data, void **prev)
+{
+	struct loop *iter;
+
+	if(!loop || !data || !prev) {
+		return(-EINVAL);
+	}
+
+	if(__loop_find(loop, NULL, data, &iter) < 0) {
+		return(-ENOENT);
+	}
+
+	*prev = iter->prev->data;
+	return(0);
+}
+
+int loop_shift_forwards(struct loop **loop, void *data)
+{
+	struct loop *iter;
+	struct loop *next;
+
+	if(!loop || !data) {
+		return(-EINVAL);
+	}
+
+	if(__loop_find(loop, NULL, data, &iter) < 0) {
+		return(-ENOENT);
+	}
+
+	next = iter->next;
+
+	iter->prev->next = next;
+	next->prev = iter->prev;
+	next->next->prev = iter;
+	iter->next = next->next;
+	iter->prev = next;
+	next->next = iter;
+
+	if(*loop == iter) {
+		*loop = iter->prev;
+	} else if(*loop == iter->prev) {
+		*loop = iter;
+	}
+
+	return(0);
+}
+
+int loop_shift_backwards(struct loop **loop, void *data)
+{
+	struct loop *iter;
+	struct loop *next;
+
+	if(!loop || !data) {
+		return(-EINVAL);
+	}
+
+	if(__loop_find(loop, NULL, data, &next) < 0) {
+		return(-ENOENT);
+	}
+
+	iter = next->prev;
+
+	iter->prev->next = next;
+	next->prev = iter->prev;
+	next->next->prev = iter;
+	iter->next = next->next;
+	iter->prev = next;
+	next->next = iter;
+
+	if(*loop == next) {
+		*loop = next->next;
+	} else if(*loop == next->next) {
+		*loop = next;
+	}
+
+	return(0);
+}
diff --git a/loop.h b/loop.h
index 746949b..03a5cfc 100644
--- a/loop.h
+++ b/loop.h
@@ -8,11 +8,16 @@ int loop_append(struct loop **loop, void *data);
 int loop_prepend(struct loop **loop, void *data);
 int loop_remove(struct loop **loop, void *data);
 int loop_find(struct loop **loop, int(*cmp)(void*, void*), void *data, void **dst);
-int loop_foreach(struct loop **loop, int(*func)(void*, void*), void*);
+int loop_foreach(struct loop **loop, void(*func)(void*));
+int loop_foreach_with_data(struct loop **loop, int(*func)(void*, void*), void*);
 int loop_free(struct loop **loop);
 int loop_get_first(struct loop **loop, void**);
 int loop_get_last(struct loop **loop, void**);
 int loop_get_length(struct loop **loop);
+int loop_get_next(struct loop **loop, void *data, void **next);
+int loop_get_prev(struct loop **loop, void *data, void **next);
+int loop_shift_backwards(struct loop **loop, void *data);
+int loop_shift_forwards(struct loop **loop, void *data);
 
 loop_iter_t loop_get_iter(struct loop **loop);
 loop_iter_t loop_iter_get_next(loop_iter_t iter);
-- 
2.47.3