diff options
| author | Ben Burwell <ben@benburwell.com> | 2015-04-01 20:29:53 -0400 |
|---|---|---|
| committer | Ben Burwell <ben@benburwell.com> | 2015-04-01 20:29:53 -0400 |
| commit | 2b30f30a330ee9bc9feb9ec4e55c8b6f3e6eb8fe (patch) | |
| tree | 08d7be1d815e1ae676eab5c734438ba048b854d1 /dcb.c | |
| parent | e282a861d5868868940b449681f2ee5da3e439e8 (diff) | |
as of 2013-11-182013-11-18
Diffstat (limited to 'dcb.c')
| -rw-r--r-- | dcb.c | 65 |
1 files changed, 65 insertions, 0 deletions
@@ -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;
+}
|