1 files changed, 95 insertions, 0 deletions
diff --git a/reftable/pq.c b/reftable/pq.c
new file mode 100644
index 0000000000..9a79f5c5ee
--- /dev/null
+++ b/reftable/pq.c
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Use of this source code is governed by a BSD-style
+ * license that can be found in the LICENSE file or at
+ * https://developers.google.com/open-source/licenses/bsd
+ */
+
+#include "pq.h"
+
+#include "reftable-error.h"
+#include "reftable-record.h"
+#include "system.h"
+#include "basics.h"
+
+int pq_less(struct pq_entry *a, struct pq_entry *b)
+{
+	int cmp, err;
+
+	err = reftable_record_cmp(a->rec, b->rec, &cmp);
+	if (err < 0)
+		return err;
+
+	if (cmp == 0)
+		return a->index > b->index;
+	return cmp < 0;
+}
+
+int merged_iter_pqueue_remove(struct merged_iter_pqueue *pq, struct pq_entry *out)
+{
+	size_t i = 0;
+	struct pq_entry e = pq->heap[0];
+	pq->heap[0] = pq->heap[pq->len - 1];
+	pq->len--;
+
+	while (i < pq->len) {
+		size_t min = i;
+		size_t j = 2 * i + 1;
+		size_t k = 2 * i + 2;
+		int cmp;
+
+		if (j < pq->len) {
+			cmp = pq_less(&pq->heap[j], &pq->heap[i]);
+			if (cmp < 0)
+				return -1;
+			else if (cmp)
+				min = j;
+		}
+
+		if (k < pq->len) {
+			cmp = pq_less(&pq->heap[k], &pq->heap[min]);
+			if (cmp < 0)
+				return -1;
+			else if (cmp)
+				min = k;
+		}
+
+		if (min == i)
+			break;
+		REFTABLE_SWAP(pq->heap[i], pq->heap[min]);
+		i = min;
+	}
+
+	if (out)
+		*out = e;
+
+	return 0;
+}
+
+int merged_iter_pqueue_add(struct merged_iter_pqueue *pq, const struct pq_entry *e)
+{
+	size_t i = 0;
+
+	REFTABLE_ALLOC_GROW_OR_NULL(pq->heap, pq->len + 1, pq->cap);
+	if (!pq->heap)
+		return REFTABLE_OUT_OF_MEMORY_ERROR;
+	pq->heap[pq->len++] = *e;
+
+	i = pq->len - 1;
+	while (i > 0) {
+		size_t j = (i - 1) / 2;
+		if (pq_less(&pq->heap[j], &pq->heap[i]))
+			break;
+		REFTABLE_SWAP(pq->heap[j], pq->heap[i]);
+		i = j;
+	}
+
+	return 0;
+}
+
+void merged_iter_pqueue_release(struct merged_iter_pqueue *pq)
+{
+	REFTABLE_FREE_AND_NULL(pq->heap);
+	memset(pq, 0, sizeof(*pq));
+}