1 files changed, 65 insertions, 0 deletions
diff --git a/dcb.c b/dcb.c
new file mode 100644
index 0000000..e2c1e4c
--- /dev/null
+++ b/dcb.c
@@ -0,0 +1,65 @@
+/**
+ * MPX OS
+ * Operating Systems - Fall 2013
+ * Averill Morash, Ben Burwell
+ */
+
+#include "mpx.h"
+
+/**
+ * Returns the character at the front of the ring queue
+ * associated with the dcb, or '\0' if the queue is empty.
+ */
+char dcb_dequeue(dcb *d) {
+  char c;
+
+  if (d->ring_count == 0) {
+	return '\0';
+  }
+
+  c = d->ring[d->ring_front];
+
+  if (d->ring_front == d->ring_size - 1) {
+	d->ring_front = 0;
+  } else {
+	d->ring_front++;
+  }
+
+  d->ring_count--;
+
+  return c;
+}
+
+/**
+ * Adds the given character to the end of the ring queue
+ * in the given dcb if there is room
+ */
+void dcb_enqueue(dcb *d, char c) {
+  if (d->ring_count >= d->ring_size) {
+	return;
+  }
+
+  if (d->ring_rear == d->ring_size - 1) {
+	d->ring_rear = 0;
+  } else {
+	d->ring_rear++;
+  }
+
+  d->ring[d->ring_rear] = c;
+
+  d->ring_count++;
+
+  return;
+}
+
+/**
+ * Set up a dcb's circular queue, and set the current_op to NO_OP
+ */
+void dcb_init(dcb *d) {
+  d->ring_front = 0;
+  d->ring_rear = -1;
+  d->ring_size = INPUT_BUFFER_MAX;
+  d->ring_count = 0;
+  d->current_op = NO_OP;
+  return;
+}