From ef21b3b5bf824e652addf850bcfd9374c7b33ce8 Mon Sep 17 00:00:00 2001
From: =?utf8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= <zbyszek@in.waw.pl>
Date: Sat, 26 Jan 2019 11:27:18 +0100
Subject: [PATCH] basic/prioq: add prioq_peek_item()

---
 src/basic/prioq.c     |  7 +++----
 src/basic/prioq.h     |  8 +++++++-
 src/test/test-prioq.c | 16 ++++++++++++++++
 3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/src/basic/prioq.c b/src/basic/prioq.c
index cfd08d5..76b27fa 100644
--- a/src/basic/prioq.c
+++ b/src/basic/prioq.c
@@ -259,15 +259,14 @@ int prioq_reshuffle(Prioq *q, void *data, unsigned *idx) {
         return 1;
 }
 
-void *prioq_peek(Prioq *q) {
-
+void *prioq_peek_by_index(Prioq *q, unsigned idx) {
         if (!q)
                 return NULL;
 
-        if (q->n_items <= 0)
+        if (idx >= q->n_items)
                 return NULL;
 
-        return q->items[0].data;
+        return q->items[idx].data;
 }
 
 void *prioq_pop(Prioq *q) {
diff --git a/src/basic/prioq.h b/src/basic/prioq.h
index bba5c7c..1fb57bf 100644
--- a/src/basic/prioq.h
+++ b/src/basic/prioq.h
@@ -19,8 +19,14 @@ int prioq_put(Prioq *q, void *data, unsigned *idx);
 int prioq_remove(Prioq *q, void *data, unsigned *idx);
 int prioq_reshuffle(Prioq *q, void *data, unsigned *idx);
 
-void *prioq_peek(Prioq *q) _pure_;
+void *prioq_peek_by_index(Prioq *q, unsigned idx) _pure_;
+static inline void *prioq_peek(Prioq *q) {
+        return prioq_peek_by_index(q, 0);
+}
 void *prioq_pop(Prioq *q);
 
+#define PRIOQ_FOREACH_ITEM(q, p)                                \
+        for (unsigned _i = 0; (p = prioq_peek_by_index(q, _i)); _i++)
+
 unsigned prioq_size(Prioq *q) _pure_;
 bool prioq_isempty(Prioq *q) _pure_;
diff --git a/src/test/test-prioq.c b/src/test/test-prioq.c
index bc5fdd1..53c9e09 100644
--- a/src/test/test-prioq.c
+++ b/src/test/test-prioq.c
@@ -69,6 +69,11 @@ static void test_struct(void) {
         assert_se(q = prioq_new((compare_func_t) test_compare));
         assert_se(s = set_new(&test_hash_ops));
 
+        assert_se(prioq_peek(q) == NULL);
+        assert_se(prioq_peek_by_index(q, 0) == NULL);
+        assert_se(prioq_peek_by_index(q, 1) == NULL);
+        assert_se(prioq_peek_by_index(q, (unsigned) -1) == NULL);
+
         for (i = 0; i < SET_SIZE; i++) {
                 assert_se(t = new0(struct test, 1));
                 t->value = (unsigned) rand();
@@ -79,6 +84,17 @@ static void test_struct(void) {
                         assert_se(set_consume(s, t) >= 0);
         }
 
+        for (i = 0; i < SET_SIZE; i++)
+                assert_se(prioq_peek_by_index(q, i));
+        assert_se(prioq_peek_by_index(q, SET_SIZE) == NULL);
+
+        unsigned count = 0;
+        PRIOQ_FOREACH_ITEM(q, t) {
+                assert_se(t);
+                count++;
+        }
+        assert_se(count == SET_SIZE);
+
         while ((t = set_steal_first(s))) {
                 assert_se(prioq_remove(q, t, &t->idx) == 1);
                 assert_se(prioq_remove(q, t, &t->idx) == 0);
-- 
2.7.4