starting to work on pty drivers, fork(), and scheduler redesign

kernel/lib/ringbuf.c

@@ -0,0 +1,34 @@
+#include <lib/ringbuf.h>
+
+void ring_buf_init(ring_buf_t* rb) {
+    rb->head = 0;
+    rb->tail = 0;
+}
+
+int ring_buf_is_empty(ring_buf_t* rb) {
+    return rb->head == rb->tail;
+}
+
+int ring_buf_is_full(ring_buf_t* rb) {
+    return ((rb->head + 1) % PTY_BUFFER_SIZE) == rb->tail;
+}
+
+int ring_buf_write(ring_buf_t *buf, char c) {
+    if (ring_buf_is_full(buf)) {
+        return -1;
+    }
+    
+    buf->data[buf->head] = c;
+    buf->head = (buf->head + 1) % PTY_BUFFER_SIZE;
+    return 0;
+}
+
+int ring_buf_read(ring_buf_t *buf, char *c) {
+    if (ring_buf_is_empty(buf)) {
+        return -1;
+    }
+    
+    *c = buf->data[buf->tail];
+    buf->tail = (buf->tail + 1) % PTY_BUFFER_SIZE;
+    return 0;
+}

kernel/lib/ringbuf.h

@@ -0,0 +1,20 @@
+#ifndef KRINGBUF_H
+#define KRINGBUF_H
+
+#include <stddef.h>
+
+#define PTY_BUFFER_SIZE 1024
+
+typedef struct {
+    char data[PTY_BUFFER_SIZE];
+    size_t head;
+    size_t tail;
+} ring_buf_t;
+
+void ring_buf_init(ring_buf_t* rb);
+int ring_buf_is_empty(ring_buf_t* rb);
+int ring_buf_is_full(ring_buf_t* rb);
+int ring_buf_write(ring_buf_t *buf, char c);
+int ring_buf_read(ring_buf_t *buf, char *c);
+
+#endif