Writing MS-DOS Device Drivers
By Marcus Johnson, December 01, 1990
December 1990/Writing MS-DOS Device Drivers/Listing 7
#includde "char.h"
/*--------- external function prototypes: ---------*/
/* look for unused key buffer */
extern char *k_alloc (void);
/* look for key buffer */
extern char *k_seek (void);
/* write decimal integer to ring buffer */
extern void r_puti (char);
/* write byte to ring buffer */
extern void r_write (char);
/* clear selected part of the screen */
extern void rawclear (void);
/* set the video mode */
extern void rawmode (void);
/* move the cursor */
extern void rawmv (void);
/* scroll the screen up */
extern void rawscroll (void);
/* output character as raw tty */
extern void rawtty (void);
/* output character to screen */
extern void rawwrite (void);
/*
* delimiters used for quoted characters as
* parameters of escape sequences
*/
#define DELIM1 '\"
#define DELIM2 '"'
/*
* characters that require special handling
*/
#define BEL '\007'
#define BS '\010'
#define NL '\012'
#define CR '\015'
#define ESC '\033'
/*
* color codes
*/
#define BLUE (01)
#define GREEN (02)
#define RED (04)
#define CYAN (BLUE <FONT FACE="Symbol" SIZE=2>½ GREEN)
#define MAGENTA (BLUE <FONT FACE="Symbol" SIZE=2>½ RED)
#define YELLOW (GREEN <FONT FACE="Symbol" SIZE=2>½ RED)
#clefine WHITE (BLUE <FONT FACE="Symbol" SIZE=2>½ GREEN <FONT FACE="Symbol" SIZE=2>½ RED)
/*
* macro's for turning on and off attributes or designating
* a color as foreground or background
*/
#define ON(x) (attrib <FONT FACE="Symbol" SIZE=2>½= (char) (x))
#define OFF(x) (attrib &= (char) (~(x)))
#define FORE(x) (attrib <FONT FACE="Symbol" SIZE=2>½= (char) (x))
#define BACK(x) (attrib <FONT FACE="Symbol" SIZE=2>½= (char) ((x) << 4))
/*
* we don't want to use the standard 'c' isdigit(); it's
* either implemented as a function (we don't want to use
* osmebody else's functions that might have unpleasant side
* effects) or a macro invoking an array of values that
* dictate what lexical properties a given character possesses
* (a waste of precious memory)
*/
#define isdigit(x) (((x) >= '0') && ((x) <= '9'))
/*
* w_write()
*
* w_write() keeps track of actually getting stuff on the screen
* and moving the cursor around
*/
void w_write()
{
switch (outchar)
{
case CR:
/* just set the column to 0 for a carriage return */
curr.loc.col = 0;
/* and fall through to the backspace handler */
case BS:
/* decrement the current column unless at the left
* margin */
if (curr.loc.col)
--curr.loc.col;
/* move the cursor and that's it... */
rawmv();
break;
default:
/* first, write the character without
moving the cursor */
rawwrite();
/* then, if we're not on the right margin, bump the
* cursor right and that's it */
if ((curr.loc.col + 1) <= max.loc.col)
{
++curr.loc.col;
rawrmv();
break;
}
/* but if we were at the right margin, check the wrap
* flag; if it's clear, just return. if not, execute
* a carriage return (just set the column to zero -
* we'll do a rawmv() call later), set the current
* character to newline, and fall into the newline
* routine */
if (!wrap)
break;
curr.loc.col = 0;
outchar = NL;
case NL:
/* if we're not at the bottom of the screen, just bump
* the line down and call rawmv() */
if (++curr.loc.line < 25)
{
rawmv();
break;
}
/* but if we were at the bottom (or somehow below!),
* make sure we're on the bottom line. If we're in
* one of the CGA 80x25 text modes, do our fancy
* assembly language scroll routine, else just let
* the BIOS handle it */
curr.loc.line = 24;
if (video_mode == 2 || video_mode == 3)
{
rawscroll();
break;
}
case BEL:
/* do a raw tty output; it handles the cursor movement
* too */
rawtty();
break;
}
}
/*
* w_buffer()
*
* w_buffer() writes a byte into the escape buffer. silently
* overwrites the last byte in the buffer if we get that far. it
* was either that or trash the new byte
*/
void w_buffer(c)
char c;
{
if (char_cnt == BUF_LEN)
esc_buf[ BUF_LEN - 1 ] = c;
else
esc_buf[ char_cnt++ ] = c;
}
/*
* w_cursor()
*
* w_cursor() handles the cursor left, right, up and down
* functions. bumps the value by the value of the 1st parameter
* in the escape sequence (if there isn't one, we put a 1 in for
* it) in the direction specified by the delta, until it hits the
* specified limit. then execute the cursor move...
*/
void w_cursor()
{
if (!char_cnt)
esc_buf[ 0 ] = 1;
while (*cur_val != limit)
{
*cur_val += delta;
esc_buf[ 0 ]--;
if (!esc_buf[ 0 ])
break;
}
rawmv();
}
/*
* w_putc()
*
* w_putc() updates the parameters that might have changed since
* last time, then runs the character through the escape sequence
* state machine
*/
void w_putc()
{
/* update parameters */
max.loc.col = SCREEN_WIDTH - 1;
cur_page = CURRENT_PAGE;
curr.position = (PAGE_TABLE [ cur_page ]).position;
if (curr.loc.col > max.loc.col)
curr.loc.col = max.loc.col;
if ((video_mode = CURRENT_MODE) == 7)
video_address = MONOCHROME + SCREEN_OFFSET;
else
video_address = GRAPHIC + SCREEN_OFFSET;
/* process the escape sequence state */
switch (state)
{
case HAVE_ESC:
/* if we have an escape, we want a left bracket.
* if we get it, change the state and return,
* else reset back to the RAW state and fall
* through */
if (outchar == '[')
{
state = HAVE_LBRACE;
break;
}
state = RAW;
case RAW:
/* if it's an escape, change the stae, else output the
* character */
if (outchar == ESC)
state = HAVE_ESC;
else
w_write();
break;
case IN_NUMBER:
/* if it's another digit, roll it into the value. else
* the state falls back to HAVE_LBRACE, and we fall
* through */
if (isdigit(outchar))
{
tmp.value *= 10;
tmp.value += outchar - '0';
break;
}
else
{
state = HAVE_LBRACE;
w_buffer(tmp.value);
}
case HAVE_LBRACE:
/* if we have a string delimiter, change the state and
* save the delimiter */
if (outchar == DELIM1 || outchar == DELIM2)
{
state = IN_STRING;
tmp.delim = outchar;
break;
}
/* else if it's 'punctuation', ignore it */
if (outchar == ';' || outchar == '=' ||
outchar == '?')
break;
/* else if it's a digit, start a number and
change the state */
if (isdigit(outchar))
{
state = IN_NUMBER;
tmp.value = outchar - '0';
break;
}
/* else it terminates the escape sequence, and
* identifies its purpose */
switch (outchar)
{
case 'A': /* cursor up */
limit = 0;
delta = (char) -1;
cur_val = &curr.loc.line;
w_cursor();
break;
case 'B': /* cursor down */
limit = 24;
delta = 1;
cur_val= &curr.loc.line;
w_cursor();
break;
case 'C': /* cursor right */
limit = max.loc.col;
delta = 1;
cur_val = &curr.loc.col;
w_cursor();
break;
case 'D': /* cursor left */
limit = 0;
delta = (char) -1;
cur_val = &curr.loc.col;
w_cursor();
break;
case 'H':
case 'R':
case 'f':
/* set cursor position: make sure there
* are at least 2 parameters stored,
* correct any out-of-range parameters,
* and execute the move. if the
* character was 'R', fall through into
* the report position sequence */
switch (char_cnt)
{
case 0:
w_buffer(1);
case 1:
w_buffer(1);
default:
break;
/* set graphic rendition - just do all
* the parameters and set/reset the
* appropriate bits in the attribute
* byte */
while (char_cnt)
{
switch (esc_buff[ --char_cnt ])
{
case 0:
attrib = 0007; break;
case 1:
ON(010); break;
case 4:
OFF(07); ON(01); break;
case 5:
ON(0200); break;
case 7:
OFF(07); 0N(0160); break;
case 8:
0FF(0167); break;
case 30:
OFF(07); break;
case 31:
OFF(07); FORE(RED); break;
case 32:
OFF(07); FORE(GREEN); break;
case 33:
OFF(07); FORE(YELLOW); break;
case 34:
OFF(07); FORE(BLUE); break;
case 35:
OFF(07); FORE(MAGENTA); break;
case 36:
OFF(07); FORE(CYAN); break;
case 37:
OFF(07); FORE(WHITE); break;
case 40:
OFF(0160); break;
case 41:
OFF(0160); BACK(RED); break;
case 42:
OFF(0160); BACK(GREEN); break;
case 43:
OFF(0160); BACK(YELLOW); break;
case 44:
OFF(0160); BACK(BLUE); break;
case 45:
OFF(0160); BACK(MAGENTA); break;
case 46:
OFF(0160); BACK(CYAN); break;
case 47:
OFF(0160); BACK(WHITE); break;
default:
break;
}
}
break;
case 'p':
if (esc_buf[ 0 ])
{
/* if the first parameter is not nul, then we're
redefining a 'normal' key. Clear the msb of
keyc1heck to indicate this */
keycheck = (esc_buf[ 0 ]) &
0000377;
/* check first to see if we've already allocated
a buffer to this key; then if not, see if we have
an unused buffer to hand out */
if (k_seek() <FONT FACE="Symbol" SIZE=2>½<FONT FACE="Symbol" SIZE=2>½ k_alloc()))
}
if (!esc_buf[ 0 ])
curr.loc.line = 1;
else if (esc_buf[ 0 ] > 25)
curr.loc.line = 25;
else
curr.loc.line = esc_buf[ 0 ];
if (!esc_buf[ 1 ])
curr.loc.col = 1;
else if (esc_buf[ 1 ] > max.loc.col + 1)
curr.loc.col = max.loc.col + 1;
else
curr.loc.col = esc_buf[ 1 ];
curr.loc.line--;
curr.loc.col--;
rawmv();
if (outchar != 'R')
break;
case 'n':
/* output the position; format is
* "\033[%.2d;%.2dR\015" */
r_write(ESC);
r_write('[');
r_puti(curr.loc.line + 1);
r_write(';');
r_puti(curr.loc.col + 1);
r_write('R');
r_write(CR);
break;
case 'J':
/* rawclear clears the screen from
* (curr.loc.line, curr.loc.col) to
* (max.loc.line, max.loc.col); so for
* clear screen, set the current
* position to the upper left hand
* corner of the screen, and the max
* line to the bottom of the screen */
curr.loc.line = curr.loc.col = 0;
max.loc.line = 24;
rawclear();
break;
case 'K':
/* and clear to end of line is even
* simpler - just set the max line equal
* to the same line we're on */
max.loc.line = curr.loc.line;
rawclear();
break;
case 'h':
case 'l':
/* set and reset mode do the same thing
* unless the mode is 7. easy */
if (!char_cnt)
w_buffer(2);
if (esc_buf[ 0 ] > 7)
break;
if (esc_buf[ 0 ] == 7)
wrap = (char) (outchar == 'h');
else
rawmode();
break;
case 'm':
{
k = 1;
kp->keystroke =
(esc_buf[ 0 ])
& 0000377;
}
else
break;
}
else
{
/* first byte was nul - an extended key. indicate
by setting msb of keycheck to $FF */
keycheck = (esc_buf[ 1 ]) <FONT FACE="Symbol" SIZE=2>|
0177400;
if (k_seek() <FONT FACE="Symbol" SIZE=2>½<FONT FACE="Symbol" SIZE=2>½ k_alloc())
{
k = 2;
kp->keystroke =
(esc_buf[ 1 ])
<FONT FACE="Symbol" SIZE=2>½ 0177400;
}
else
break;
}55
/* copy the parameters into the buffer, counting as we go */
for (*len= 0; (k < char_cnt) &&
(k < KEY_BUFLEN); ++*len)
*ptr++ = esc_buf[ k++ ];
break;
case 's':
/* save current position */
saved.position = curr.position;
break;
case 'u':
/* restore current position */
curr.position = saved.position;
rawmv();
break;
default:
/* anything else? discard the parameters
* and output the final character to the
* screen */
w_write();
break;
}
/* finally, clear the buffer by resetting the count
and fall back to the RAW state */
char_cnt = 0;
state = RAW;
break;
case IN_STRING:
/* finally, the IN_STRING case - if the character
* isn't the delimiter we saved, then put it into
* the buffer as it was received */
if (outchar == tmp.delim)
state = HAVE_LBRACE;
else
w_buffer(outchar);
break;
}
}
