On 9/21/2018 1:39 PM, Derrick Stolee via GitGitGadget wrote:
From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
When consuming a priority queue, it can be convenient to inspect
the next object that will be dequeued without actually dequeueing
it. Our existing library did not have such a 'peek' operation, so
add it as prio_queue_peek().
Add a reference-level comparison in t/helper/test-prio-queue.c
so this method is exercised by t0009-prio-queue.sh.
Signed-off-by: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
---
prio-queue.c | 9 +++++++++
prio-queue.h | 6 ++++++
t/helper/test-prio-queue.c | 10 +++++++---
3 files changed, 22 insertions(+), 3 deletions(-)
diff --git a/prio-queue.c b/prio-queue.c
index a078451872..d3f488cb05 100644
--- a/prio-queue.c
+++ b/prio-queue.c
@@ -85,3 +85,12 @@ void *prio_queue_get(struct prio_queue *queue)
}
return result;
}
+
+void *prio_queue_peek(struct prio_queue *queue)
+{
+ if (!queue->nr)
+ return NULL;
+ if (!queue->compare)
+ return queue->array[queue->nr - 1].data;
+ return queue->array[0].data;
+}
The second branch here is never run by the test suite, as the only
consumers never have compare== NULL. I'll add an ability to test this
"stack" behavior into t0009-prio-queue.sh.
-Stolee
