Liren Large Software Subsidy 7/07.iso/c/c005/4.ddi/C/KBSTUFF.C

C/C++ Source or Header | 1986-08-05 | 4.7 KB | 155 lines

/**
*
* Name        kbstuff -- Force a string into the BIOS type-ahead
*               buffer.
*
* Synopsis    premainder = kbstuff(at_head,pstring);
*
*        char *premainder  Pointer to first character in string
*                  NOT inserted in queue, or to the
*                  trailing NUL ('\0') if they were all
*                  placed in the queue.
*        int at_head      KB_HEAD if string to be placed at head
*                  of queue, KB_TAIL if at tail.
*        char *pstring      Pointer to first character in string.
*                  String must be terminated by NUL ('\0').
*
* Description    This function forces a string of keystrokes into the
*        BIOS type-ahead queue as if they were typed by the
*        operator.  The string may be inserted at the tail of the
*        queue (as if most recently typed) or at the head (least
*        recently typed).
*
*        If characters in the string are to be placed at the tail
*        of the queue, then as many as possible are inserted and
*        the value of the function is returned as a pointer to
*        the first character NOT inserted.
*
*        If the string is to be placed at the head of the queue,
*        then characters are inserted into the queue if and only
*        if they all fit.  (Therefore no string longer than 15
*        characters may be placed at the head of the queue.)
*
*        The BIOS keyboard buffer is arranged as a circular queue
*        of fifteen pairs of bytes (plus one pair for overhead).
*        For extended key sequences the character value is 0 and
*        the scan code is as described in the IBM Technical
*        Reference.  For ASCII characters, on the other hand, the
*        first byte of the pair is the ASCII code for the
*        character and the second is the keystroke's scan code
*        (if the key was generated by a normal scan code) or 0
*        (if the key was generated by ALT plus the numeric ASCII
*        code on the numeric keypad).  For instance,
*
*            pressing 'a' generates character 65, scan code 30,
*
*        but
*
*            pressing ALT + 65 generates character 65, scan code 0.
*
*        (Virtually all application programs treat those two
*        cases identically.)
*
*        For ordinary ASCII characters in the string, this
*        function inserts 0 as the scan code.
*
*        To indicate extended key sequences in the string, use
*        the character '\377' followed by the scan code.  This
*        function will insert 0 as the character value followed
*        by the scan code.
*
* Returns    premainder      Pointer to first character in string
*                  NOT inserted in queue, or to the
*                  trailing NUL ('\0') if they were all
*                  placed in the queue.
*
* Version    3.0 (C)Copyright Blaise Computing Inc.    1986
*
**/

#include <bkeybd.h>
#include <butility.h>

#define EXT_FLAG    '\377'            /* Indicates scan code of       */
                      /* extended key sequence.       */

char *kbstuff(at_head,pstring)
int  at_head;
char *pstring;
{
    int       length,i;
    register int  j;
    register char *ptr;
    char      *pend;
    int       ints_were_on;
    int       total_size;
    char      value,scan;

    if (at_head == KB_TAIL)
    {                      /* Stuff at tail of queue.      */
    ints_were_on = utintoff();    /* Turn interrupts off.          */
    for (; *pstring; pstring++)
    {
        if (*pstring == EXT_FLAG)
        {
        value = '\0';
        scan  = *++pstring;
        }
        else
        {
        value = *pstring;
        scan  = '\0';
        }
        if (kbplace(at_head,value,scan))    /* Try to stuff it.   */
        break;              /* Quit if it didn't fit.       */
    }
    }
    else
    {                      /* Stuff at head of queue.      */
    length = 0;
    for (ptr = pstring; *ptr; ptr++)
    {                  /* Measure length of string.    */
        length++;
        if (*ptr == EXT_FLAG)
        ptr++;
    }
    pend = ptr;              /* Pointer to end of string.    */

    ints_were_on = utintoff();    /* Turn interrupts off.          */

    if (length <= kbqueue(&total_size))
    {                  /* The string fits.          */
        for (i = length; i; i--)  /* Stuff each character in      */
        {                  /* reverse order.           */
        ptr = pstring;
        for (j = 1; j < i; j++)
        {              /* Step past first (i-1)          */
                      /* characters in string.          */
            if (*ptr == EXT_FLAG)
            ptr++;
            ptr++;
        }
                      /* Now ptr points to i-th       */
                      /* character in string.          */
        if (*ptr == EXT_FLAG)
            kbplace(at_head,
                (char) 0,
                *(ptr + 1));       /* Scan code only. */
        else
            kbplace(at_head,
                *ptr,           /* Character only. */
                (char) 0);
        }
        pstring = pend;          /* All characters stuffed.      */
    }
    else
    {
        /* Do nothing. */          /* String too big:  No          */
    }                  /* characters stuffed.          */
    }

    if (ints_were_on)
    utinton();              /* Turn interrupts back on.     */
    return pstring;              /* Return remainder of string.  */
}