lpq: New module

[ccan] / ccan / lpq / lpq.c

diff --git a/ccan/lpq/lpq.c b/ccan/lpq/lpq.c
new file mode 100644 (file)
index 0000000..a93c4be
--- /dev/null
+++ b/ccan/lpq/lpq.c
@@ -0,0 +1,31 @@
+/* GNU LGPL version 2 (or later) - see LICENSE file for details */
+#include <assert.h>
+
+#include <ccan/cast/cast.h>
+
+#include <ccan/lpq/lpq.h>
+
+static int lpq_cmp(const struct lpq_ *pq, size_t offset,
+                  const struct lpq_link *al, const struct lpq_link *bl)
+{
+       void *a = (char *)al - offset;
+       void *b = (char *)bl - offset;
+
+       return total_order_cmp(pq->order, a, b);
+}
+
+struct lpq_link **lpq_frontp_(struct lpq_ *pq, size_t offset)
+{
+       struct lpq_link **frontp = &pq->list;
+       struct lpq_link **p;
+
+       if (lpq_empty_(pq))
+               return NULL;
+
+       for (p = &(pq->list->next); *p; p = &(*p)->next) {
+               if (lpq_cmp(pq, offset, *p, *frontp) >= 0)
+                       frontp = p;
+       }
+
+       return frontp;
+}