From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 28 Sep 2021 22:13:12 +0000 (+0200)
Subject: list: add LIST_POP() helper that pops the first item off a linked list
X-Git-Tag: v250-rc1~161
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=55cb63bf6e5878e25ce7934b57b7214a9f0cc161;p=thirdparty%2Fsystemd.git

list: add LIST_POP() helper that pops the first item off a linked list
---

diff --git a/src/basic/list.h b/src/basic/list.h
index e488fff9f02..effee0e435e 100644
--- a/src/basic/list.h
+++ b/src/basic/list.h
@@ -181,3 +181,12 @@
                 }                                                       \
                 (b) = NULL;                                             \
         } while (false)
+
+#define LIST_POP(name, a)                                               \
+        ({                                                              \
+                typeof(a)* _a = &(a);                                   \
+                typeof(a) _p = *_a;                                     \
+                if (_p)                                                 \
+                        LIST_REMOVE(name, *_a, _p);                     \
+                _p;                                                     \
+        })
diff --git a/src/test/test-list.c b/src/test/test-list.c
index a41f23ab3ed..25cc55a998d 100644
--- a/src/test/test-list.c
+++ b/src/test/test-list.c
@@ -247,5 +247,14 @@ int main(int argc, const char *argv[]) {
 
         assert_se(head == NULL);
 
+        LIST_PREPEND(item, head, items + 0);
+        LIST_PREPEND(item, head, items + 1);
+        LIST_PREPEND(item, head, items + 2);
+
+        assert_se(LIST_POP(item, head) == items + 2);
+        assert_se(LIST_POP(item, head) == items + 1);
+        assert_se(LIST_POP(item, head) == items + 0);
+        assert_se(LIST_POP(item, head) == NULL);
+
         return 0;
 }