path: root/kernel/drivers/tty/ldisc.c

#include "drivers/tty/ldisc.h"
#include <drivers/keyboard.h>
#include <drivers/tty/tty.h>
#include <errno.h>
#include <util/bits.h>
#include <util/debug.h>
#include <util/string.h>

#define ldisc_to_tty(ldisc) CONTAINER_OF((ldisc), tty_t, tty_ldisc)

/**
 * Initialize the line discipline. Don't forget to wipe the buffer associated
 * with the line discipline clean.
 *
 * @param ldisc line discipline.
 */
void ldisc_init(ldisc_t *ldisc)
{
    // reset static buffer
    memset(ldisc->ldisc_buffer, 0, LDISC_BUFFER_SIZE);

    // init the queue
    sched_queue_init(&ldisc->ldisc_read_queue);

    // fill in other fields
    ldisc->ldisc_head = 0;
    ldisc->ldisc_tail = 0;
    ldisc->ldisc_cooked = 0;
    ldisc->ldisc_full = 0; // 0 not full
}

/**
 * While there are no new characters to be read from the line discipline's
 * buffer, you should make the current thread to sleep on the line discipline's
 * read queue. Note that this sleep can be cancelled. What conditions must be met 
 * for there to be no characters to be read?
 *
 * @param  ldisc the line discipline
 * @param  lock  the lock associated with `ldisc`
 * @return       0 if there are new characters to be read or the ldisc is full.
 *               If the sleep was interrupted, return what
 *               `sched_cancellable_sleep_on` returned (i.e. -EINTR)
 */
long ldisc_wait_read(ldisc_t *ldisc)
{
    // while there are no need chars to be read, sleep
    while ( 
        ldisc->ldisc_head == ldisc->ldisc_tail
        )
    {
        long ret = sched_cancellable_sleep_on(&ldisc->ldisc_read_queue);
        if (ret != 0)
        {
            return ret;
        }
    }

    // if we are here, it means we have new chars to read
    return 0;
}

/**
 * Reads `count` bytes (at max) from the line discipline's buffer into the
 * provided buffer. Keep in mind the the ldisc's buffer is circular.
 *
 * If you encounter a new line symbol before you have read `count` bytes, you
 * should stop copying and return the bytes read until now.
 * 
 * If you encounter an `EOT` you should stop reading and you should NOT include 
 * the `EOT` in the count of the number of bytes read
 *
 * @param  ldisc the line discipline
 * @param  buf   the buffer to read into.
 * @param  count the maximum number of bytes to read from ldisc.
 * @return       the number of bytes read from the ldisc.
 */
size_t ldisc_read(ldisc_t *ldisc, char *buf, size_t count)
{
    dbg(DBG_DISK, "ldisc_read: count = %d\n", count);

    // read from ldisc buffer to buf
    size_t i = 0;
    int break_loop = 0;
    while (i < count && !break_loop)
    {
        // if we have no new chars to read, break loop
        if (ldisc->ldisc_head == ldisc->ldisc_tail) 
        {
            break_loop = 1;
            continue;
        }


        char c = ldisc->ldisc_buffer[ldisc->ldisc_tail];
        dbg(DBG_DISK, "ldisc_read: %c\n", c);
        switch (c)
        {

        case EOT:
            buf[i] = c;
            ldisc->ldisc_tail = (ldisc->ldisc_tail + 1) % LDISC_BUFFER_SIZE;
            break_loop = 1;
            break;

        // case ETX:
        //     ldisc->ldisc_tail = ldisc->ldisc_cooked;
        //     break;

        case '\n':
            buf[i] = c;
            ldisc->ldisc_tail = (ldisc->ldisc_tail + 1) % LDISC_BUFFER_SIZE;
            i++;
            break_loop = 1;
            break;
        
        default:
            buf[i] = c;
            ldisc->ldisc_tail = (ldisc->ldisc_tail + 1) % LDISC_BUFFER_SIZE;
            i++;
            break;
        }

        dbg(DBG_DISK, "ldisc_read: i = %d\n", i);
    }

    // return the number of bytes read
    return i;
}

/**
 * Place the character received into the ldisc's buffer. You should also update
 * relevant fields of the struct.
 *
 * An easier way of handling new characters is making sure that you always have
 * one byte left in the line discipline. This way, if the new character you
 * received is a new line symbol (user hit enter), you can still place the new
 * line symbol into the buffer; if the new character is not a new line symbol,
 * you shouldn't place it into the buffer so that you can leave the space for
 * a new line symbol in the future. 
 * 
 * If the line discipline is full, all incoming characters should be ignored. 
 *
 * Here are some special cases to consider:
 *      1. If the character is a backspace:
 *          * if there is a character to remove you must also emit a `\b` to
 *            the vterminal.
 *      2. If the character is end of transmission (EOT) character (typing ctrl-d)
 *      3. If the character is end of text (ETX) character (typing ctrl-c)
 *      4. If your buffer is almost full and what you received is not a new line
 *      symbol
 *
 * If you did receive a new line symbol, you should wake up the thread that is
 * sleeping on the wait queue of the line discipline. You should also
 * emit a `\n` to the vterminal by using `vterminal_write`.  
 * 
 * If you encounter the `EOT` character, you should add it to the buffer, 
 * cook the buffer, and wake up the reader (but do not emit an `\n` character 
 * to the vterminal)
 * 
 * In case of `ETX` you should cause the input line to be effectively transformed
 * into a cooked blank line. You should clear uncooked portion of the line, by 
 * adjusting ldisc_head. 
 *
 * Finally, if the none of the above cases apply you should fallback to
 * `vterminal_key_pressed`.
 *
 * Don't forget to write the corresponding characters to the virtual terminal
 * when it applies!
 *
 * @param ldisc the line discipline
 * @param c     the new character
 */
void ldisc_key_pressed(ldisc_t *ldisc, char c)
{
    switch (c)
    {
    case '\b':
        // if there is a character to remove
        if (ldisc->ldisc_head != ldisc->ldisc_tail)
        {
            // remove the last char
            ldisc->ldisc_head = (ldisc->ldisc_head - 1 + LDISC_BUFFER_SIZE) % LDISC_BUFFER_SIZE;

            // emit a `\b` to the vterminal
            vterminal_write(&ldisc_to_tty(ldisc)->tty_vterminal, "\b", 1);


            if (ldisc->ldisc_full) 
            {
                ldisc->ldisc_full = 0;
            }
        }
        break;

    case '\n':

        // add the new char to the buffer
        ldisc->ldisc_buffer[ldisc->ldisc_head] = c;

        if (!ldisc->ldisc_full) 
        {
            ldisc->ldisc_head = (ldisc->ldisc_head + 1) % LDISC_BUFFER_SIZE;
        }

        // cook the buffer
        ldisc->ldisc_cooked = ldisc->ldisc_head;

        sched_wakeup_on(&ldisc->ldisc_read_queue, 0);

        // emit a `\n` to the vterminal
        vterminal_write(&ldisc_to_tty(ldisc)->tty_vterminal, "\n", 1);

        if (ldisc->ldisc_full) 
        {
            ldisc->ldisc_full = 0;
        }
        break;

    case EOT:
        // add the new char to the buffer
        dbg(DBG_DISK, "EOT\n");
        ldisc->ldisc_buffer[ldisc->ldisc_head] = c;
        if (!ldisc->ldisc_full) 
        {
            ldisc->ldisc_head = (ldisc->ldisc_head + 1) % LDISC_BUFFER_SIZE;
        }

        // cook the buffer
        ldisc->ldisc_cooked = ldisc->ldisc_head;

        // wake up the thread that is sleeping on the wait queue of the line discipline
        sched_wakeup_on(&ldisc->ldisc_read_queue, 0);

        vterminal_write(&ldisc_to_tty(ldisc)->tty_vterminal, "\n", 1);

        if (ldisc->ldisc_full) 
        {
            ldisc->ldisc_full = 0;
        }
        break;

    case ETX:
        // clear uncooked portion of the line
        dbg(DBG_DISK, "ETX\n");
        ldisc->ldisc_head = (ldisc->ldisc_cooked + 1) % LDISC_BUFFER_SIZE;
        ldisc->ldisc_cooked = ldisc->ldisc_head;

        // wake up the thread that is sleeping on the wait queue of the line discipline
        sched_wakeup_on(&ldisc->ldisc_read_queue, 0);

        // emit a `\n` to the vterminal
        vterminal_write(&ldisc_to_tty(ldisc)->tty_vterminal, "\n", 1);
        break;

    default:
        // if the buffer is full, ignore the incoming char
        // if (ldisc->ldisc_full)
        // {
        //     return;
        // }

        // if none applies, fallback to vterminal_key_pressed
        // vterminal_write(ldisc_to_tty(ldisc), &c, 1);

        // update the buffer if it's not full
        if (!ldisc->ldisc_full)
        {
            ldisc->ldisc_buffer[ldisc->ldisc_head] = c;
            ldisc->ldisc_head = (ldisc->ldisc_head + 1) % LDISC_BUFFER_SIZE;
            if (ldisc->ldisc_head + 1 == ldisc->ldisc_tail)
            {
                ldisc->ldisc_full = 1;
            }
            vterminal_key_pressed(&ldisc_to_tty(ldisc)->tty_vterminal);
        }

        break;
    }
}

/**
 * Copy the raw part of the line discipline buffer into the buffer provided.
 *
 * @param  ldisc the line discipline
 * @param  s     the character buffer to write to
 * @return       the number of bytes copied
 */
size_t ldisc_get_current_line_raw(ldisc_t *ldisc, char *s)
{
    // copy the raw part of the line discipline buffer into the buffer provided
    size_t i = 0;
    size_t j = ldisc->ldisc_cooked;
    while (j != ldisc->ldisc_head)
    {
        s[i] = ldisc->ldisc_buffer[j];
        j = (j + 1) % LDISC_BUFFER_SIZE;
        i++;
    }

    // return the number of bytes copied
    return i;
}