1 files changed, 68 insertions, 0 deletions

diff --git a/kernel/include/drivers/tty/ldisc.h b/kernel/include/drivers/tty/ldisc.h
new file mode 100644
index 0000000..920c816
--- /dev/null
+++ b/kernel/include/drivers/tty/ldisc.h
@@ -0,0 +1,68 @@
+#pragma once
+
+#include "types.h"
+#include <proc/kmutex.h>
+
+#define LDISC_BUFFER_SIZE 128
+
+/**
+ * The line discipline is implemented as a circular buffer containing two 
+ * sections: cooked and raw. These sections are tracked by three indices: 
+ * ldisc_cooked, ldisc_tail, and ldisc_head.
+ *  
+ * New characters (via ldisc_key_pressed) are put at the head position (and the 
+ * head is incremented). If a newline is received, cooked is moved up to the head. 
+ * Characters are read from tail up until cooked, and the tail is updated
+ * to equal cooked.
+ * 
+ * The cooked portion (ready for reading) runs from ldisc_tail (inclusive) to
+ * ldisc_cooked (exclusive). The raw portion (subject to editing) runs from 
+ * ldisc_cooked (inclusive) to ldisc_head (exclusive).
+ * 
+ * e.g.
+ *            [..........t........c...h.......]
+ *              (cooked) ^^^^^^^^^
+ *                                ^^^^ (raw)
+ *
+ * Bear in mind that the buffer is circular, so another possible configuration
+ * might be 
+ * 
+ *            [....h............t......c......]
+ *                     (cooked) ^^^^^^^
+ *             ^^^^                    ^^^^^^^ (raw)
+ * 
+ * When incrementing the indices, make sure that you take the circularity of
+ * the buffer into account! (Hint: using LDISC_BUFFER_SIZE macro will be helpful.) 
+ * 
+ * The field ldisc_full is used to indicate when the circular buffer has been
+ * completely filled. This is necessary because there are two possible states
+ * in which cooked == tail == head: 
+ * 
+ *      1) The buffer is empty, or 
+ * 
+ *      2) The buffer is full: head has wrapped around and is equal to tail. 
+ * 
+ * ldisc_full is used to differentiate between these two states.
+ */
+typedef struct ldisc
+{
+    size_t ldisc_cooked; // Cooked is the index after the most last or most recent '\n' in the buffer.
+    size_t ldisc_tail;   // Tail is the index from which characters are read by processes
+    size_t ldisc_head;   // Head is the index from which new characters are placed
+    char ldisc_full;     // Full identifies if the buffer is full
+                         // 1 -> full
+                         // 0 -> not full  
+
+    ktqueue_t ldisc_read_queue; // Queue for threads waiting for data to be read 
+    char ldisc_buffer[LDISC_BUFFER_SIZE];
+} ldisc_t;
+
+void ldisc_init(ldisc_t *ldisc);
+
+long ldisc_wait_read(ldisc_t *ldisc);
+
+size_t ldisc_read(ldisc_t *ldisc, char *buf, size_t count);
+
+void ldisc_key_pressed(ldisc_t *ldisc, char c);
+
+size_t ldisc_get_current_line_raw(ldisc_t *ldisc, char *s);
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