1 files changed, 59 insertions, 0 deletions
diff --git a/pipeline.c b/pipeline.c
new file mode 100644
index 0000000..477421f
--- /dev/null
+++ b/pipeline.c
@@ -0,0 +1,59 @@
+#include "pipeline.h"
+#include <string.h>
+
+int pipeline_add_stage_after(struct pipeline_t *pl, struct pipeline_stage_t *stage, const char *name)
+{
+  if (!name) {
+    /* name == NULL: insert at end of pipeline */
+    stage->next = NULL;
+
+#if 0
+    if (pl->first) {
+      struct pipeline_stage_t *tail = pl->first;
+      for (; tail->next; tail = tail->next);
+      tail->next = stage;
+    } else { /* corner case: pipeline is empty */
+      pl->first = stage;
+    }
+#else
+    /* i like this implementation because it's pretty */
+    struct pipeline_stage_t **ptail = &pl->first;
+    for (; *ptail; ptail = &(*ptail)->next);
+    *ptail = stage;
+#endif
+
+    return 1;
+  }
+
+  for (struct pipeline_stage_t *cur = pl->first; cur; cur = cur->next) {
+    if (name == cur->name || !strcmp(name, cur->name)) {
+      stage->next = cur->next;
+      cur->next = stage;
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+int pipeline_add_stage_before(struct pipeline_t *pl, struct pipeline_stage_t *stage, const char *name)
+{
+  if (!name || !pl->first || name == pl->first->name || !strcmp(name, pl->first->name)) {
+    stage->next = pl->first;
+    pl->first = stage;
+    return 1;
+  }
+
+  /* note that it's okay we don't properly check if prev->first->name equals name here, since that was done above. */
+  for (struct pipeline_stage_t *cur = pl->first->next, *prev = pl->first; cur; prev = cur, cur = cur->next) {
+    if (name == cur->name || !strcmp(name, cur->name)) {
+      prev->next = stage;
+      stage->next = cur;
+      return 1;
+    }
+  }
+
+  return 0;
+}
+
+