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-rw-r--r--lib/src/srv_tsort.c75
1 files changed, 75 insertions, 0 deletions
diff --git a/lib/src/srv_tsort.c b/lib/src/srv_tsort.c
new file mode 100644
index 0000000..e2549b1
--- /dev/null
+++ b/lib/src/srv_tsort.c
@@ -0,0 +1,75 @@
+#include <stdbool.h>
+#include <stddef.h>
+#include <string.h>
+#include <errno.h>
+
+#include "service.h"
+
+static bool has_dependencies(service_t *list, service_t *svc)
+{
+ size_t i;
+
+ while (list != NULL) {
+ for (i = 0; i < svc->num_after; ++i) {
+ if (!strcmp(svc->after[i], list->name))
+ return true;
+ }
+
+ for (i = 0; i < list->num_before; ++i) {
+ if (!strcmp(list->before[i], svc->name))
+ return true;
+ }
+
+ list = list->next;
+ }
+
+ return false;
+}
+
+service_t *srv_tsort(service_t *list)
+{
+ service_t *nl = NULL, *end = NULL;
+ service_t *svc, *prev;
+
+ while (list != NULL) {
+ /* remove first service without dependencies */
+ prev = NULL;
+ svc = list;
+
+ while (svc != NULL) {
+ if (has_dependencies(list, svc)) {
+ prev = svc;
+ svc = svc->next;
+ } else {
+ if (prev != NULL) {
+ prev->next = svc->next;
+ } else {
+ list = svc->next;
+ }
+ svc->next = NULL;
+ break;
+ }
+ }
+
+ /* cycle! */
+ if (svc == NULL) {
+ if (end == NULL) {
+ nl = list;
+ } else {
+ end->next = list;
+ }
+ errno = ELOOP;
+ break;
+ }
+
+ /* append to new list */
+ if (end == NULL) {
+ nl = end = svc;
+ } else {
+ end->next = svc;
+ end = svc;
+ }
+ }
+
+ return nl;
+}