From 6c33d90aaf83e96f071932080bb81dbdd26c2f3a Mon Sep 17 00:00:00 2001
From: Nick Krichevsky <nick@ollien.com>
Date: Wed, 25 Sep 2019 21:46:31 -0400
Subject: [PATCH] Add ability to add something to the front of the queue

---
 queue.c | 25 +++++++++++++++++++++++++
 queue.h |  1 +
 2 files changed, 26 insertions(+)

diff --git a/queue.c b/queue.c
index 787dee9..6f07adc 100644
--- a/queue.c
+++ b/queue.c
@@ -43,6 +43,30 @@ int enqueue(struct queue *q, void *item) {
 	return 0;
 }
 
+/**
+ * Enqueue an item in the given queue, but allow it to cut the line and insert it at the front.
+ *
+ * @param q
+ * @param item
+ * @return int
+ */
+int priority_enqueue(struct queue *q, void *item) {
+	if (q->n == q->cap) {
+		return -1;
+	}
+
+	// Shift all of the items back.
+	for (int i = q->n ; i > 0; i--) {
+		q->items[i] = q->items[i - 1];
+	}
+
+	// Put the new item at the front
+	q->items[0] = item;
+	q->n++;
+
+	return 0;
+}
+
 /**
  * Dequeue an item from the given queue.
  *
@@ -57,6 +81,7 @@ int dequeue(struct queue *q, void **item) {
 
 	q->n--;
 	*item = q->items[0];
+	// Shift all of the items forward.
 	for (int i = 1; i <= q->n; i++) {
 		q->items[i-1] = q->items[i];
 	}
diff --git a/queue.h b/queue.h
index aab2ce0..63b8848 100644
--- a/queue.h
+++ b/queue.h
@@ -10,6 +10,7 @@ struct queue {
 struct queue init_queue(int cap);
 void free_queue(struct queue *q);
 int enqueue(struct queue *q, void *item);
+int priority_enqueue(struct queue *q, void *item);
 int dequeue(struct queue *q, void **item);
 
 #endif
\ No newline at end of file