[dosdemo] / src / dos / keyb.c

/*
DOS interrupt-based keyboard driver.
Copyright (C) 2013  John Tsiombikas <nuclear@member.fsf.org>

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License  for more details.

You should have received a copy of the GNU General Public License
along with the program. If not, see <http://www.gnu.org/licenses/>
*/
#define KEYB_C_

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <conio.h>
#include <dos.h>

#ifdef __WATCOMC__
#include <i86.h>
#endif
#ifdef __DJGPP__
#include <stdint.h>
#include <dpmi.h>
#include <go32.h>
#include <pc.h>
#endif

#include "keyb.h"
#include "scancode.h"

#define KB_INTR         0x9
#define KB_PORT         0x60

#define PIC1_CMD_PORT   0x20
#define OCW2_EOI                (1 << 5)

#ifdef __WATCOMC__
#define INTERRUPT __interrupt __far

#define DONE_INIT       (prev_handler)
static void (INTERRUPT *prev_handler)();
#endif

#ifdef __DJGPP__
#define INTERRUPT

#define DONE_INIT prev_intr.pm_offset
static _go32_dpmi_seginfo intr, prev_intr;

#define outp(p, v)      outportb(p, v)
#define inp(p)  inportb(p)
#endif

static void INTERRUPT kbintr();

static int *buffer;
static int buffer_size, buf_ridx, buf_widx;
static int last_key;

static unsigned int num_pressed;
static unsigned char keystate[256];

#define ADVANCE(x)      ((x) = ((x) + 1) % buffer_size)

int kb_init(int bufsz)
{
        if(DONE_INIT) {
                fprintf(stderr, "keyboard driver already initialized!\n");
                return 0;
        }

        buffer_size = bufsz;
        if(buffer_size && !(buffer = malloc(buffer_size * sizeof *buffer))) {
                fprintf(stderr, "failed to allocate input buffer, continuing without\n");
                buffer_size = 0;
        }
        buf_ridx = buf_widx = 0;
        last_key = -1;

        memset(keystate, 0, sizeof keystate);
        num_pressed = 0;

        /* set our interrupt handler */
        _disable();
#ifdef __WATCOMC__
        prev_handler = _dos_getvect(KB_INTR);
        _dos_setvect(KB_INTR, kbintr);
#endif
#ifdef __DJGPP__
        _go32_dpmi_get_protected_mode_interrupt_vector(KB_INTR, &prev_intr);
        intr.pm_offset = (intptr_t)kbintr;
        intr.pm_selector = _go32_my_cs();
        _go32_dpmi_allocate_iret_wrapper(&intr);
        _go32_dpmi_set_protected_mode_interrupt_vector(KB_INTR, &intr);
#endif
        _enable();

        return 0;
}

void kb_shutdown(void)
{
        if(!DONE_INIT) {
                return;
        }

        /* restore the original interrupt handler */
        _disable();
#ifdef __WATCOMC__
        _dos_setvect(KB_INTR, prev_handler);
#endif
#ifdef __DJGPP__
        _go32_dpmi_set_protected_mode_interrupt_vector(KB_INTR, &prev_intr);
        _go32_dpmi_free_iret_wrapper(&intr);
#endif
        _enable();

        free(buffer);
}

int kb_isdown(int key)
{
        switch(key) {
        case KB_ANY:
                return num_pressed;

        case KB_ALT:
                return keystate[KB_LALT] + keystate[KB_RALT];

        case KB_CTRL:
                return keystate[KB_LCTRL] + keystate[KB_RCTRL];
        }
        return keystate[key];
}

#ifdef __WATCOMC__
void halt(void);
#pragma aux halt = \
        "sti" \
        "hlt";
#endif

#ifdef __DJGPP__
#define halt() asm volatile("sti\n\thlt\n\t")
#endif

void kb_wait(void)
{
        int key;
        while((key = kb_getkey()) == -1) {
                /* put the processor to sleep while waiting for keypresses, but first
                 * make sure interrupts are enabled, or we'll sleep forever
                 */
                halt();
        }
        kb_putback(key);
}

int kb_getkey(void)
{
        int res;

        if(buffer) {
                if(buf_ridx == buf_widx) {
                        return -1;
                }
                res = buffer[buf_ridx];
                ADVANCE(buf_ridx);
        } else {
                res = last_key;
                last_key = -1;
        }
        return res;
}

void kb_putback(int key)
{
        if(buffer) {
                /* go back a place */
                if(--buf_ridx < 0) {
                        buf_ridx += buffer_size;
                }

                /* if the write end hasn't caught up with us, go back one place
                 * and put it there, otherwise just overwrite the oldest key which
                 * is right where we were.
                 */
                if(buf_ridx == buf_widx) {
                        ADVANCE(buf_ridx);
                }

                buffer[buf_ridx] = key;
        } else {
                last_key = key;
        }
}

static void INTERRUPT kbintr()
{
        unsigned char code;
        int key, press;

        code = inp(KB_PORT);

        if(code >= 128) {
                press = 0;
                code -= 128;

                if(num_pressed > 0) {
                        num_pressed--;
                }
        } else {
                press = 1;

                num_pressed++;
        }

        key = scantbl[code];

        if(press) {
                /* append to buffer */
                last_key = key;
                if(buffer_size > 0) {
                        buffer[buf_widx] = key;
                        ADVANCE(buf_widx);
                        /* if the write end overtook the read end, advance the read end
                         * too, to discard the oldest keypress from the buffer
                         */
                        if(buf_widx == buf_ridx) {
                                ADVANCE(buf_ridx);
                        }
                }
        }

        /* and update keystate table */
        keystate[key] = press;

        outp(PIC1_CMD_PORT, OCW2_EOI);  /* send end-of-interrupt */
}