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/* subroutine to put a value string into an environment symbol.
Uses the controling command.com environment, not the programs.
This means that the env variable is set so other routines in
a .BAT file may use it.
call: settheenv (char * symbol, char * val);
symbol is an asciiz string containing the env variable name,
val is an asciiz string containing the value to assign to this vbl.
returns: 0 = OK,
1 = failure.
failure is not unlikely. The env block may be full. Or on some
systems the env block might not be found
SETENVS.C was written by Richard Marks <rmarks@KSP.unisys.COM>.
*/
#include <stdio.h>
#include <dos.h>
#include <string.h>
#include <stdlib.h>
typedef struct {
char fill1[0x0A];
int *prev_term_handler;
int *prev_ctrl_c;
int *prev_crit_error;
char fill2[0x16];
int envir_seg;
} psp;
typedef struct {
char type;
int psp_segment;
int num_segments;
char fill[11];
char arena_data;
} arena;
#define NORMAL_ATYPE 0x4D
#define LAST_ATYPE 0x5A
static arena * get_next_arena (arena * ap) {
return( MK_FP( FP_SEG(ap)+1+ap->num_segments, 0) );
}
/* returns 0 if passed pointer is to an arena, else returns 1 */
static int is_valid_arena (arena * ap) {
arena * ap1;
if (ap->type == NORMAL_ATYPE &&
(ap1=get_next_arena(ap))->type == NORMAL_ATYPE &&
( (ap1=get_next_arena(ap1))->type == NORMAL_ATYPE ||
ap1->type == LAST_ATYPE) )
return(0);
return (1);
}
static arena * get_first_arena () {
/* return pointer to the first arena.
* scan memory for a 0x4D on a segment start,
* see if this points to another two levels of arena
*/
arena * ap, * ap1;
int * temp;
int segment;
for (segment=0; segment<_CS; segment++) {
ap = MK_FP(segment, 0);
if ( is_valid_arena (ap) == 0) return (ap);
}
return(NULL);
} /* end get_first_arena */
static int is_valid_env (char * ad, int num_segs) {
char * base_ad;
base_ad = ad;
while ( (*ad) && (((ad-base_ad)>>4) < num_segs) ) {
if (strnicmp(ad, "COMSPEC=", 8)==0) return(0);
ad += strlen(ad) + 1;
}
return (1);
}
static arena * get_arena_of_environment () {
/* to get the arena of first environment block:
First get segment of COMMAND.COM from segment of previous critical err code.
Then scan all the arenas for an environment block with a matching PSP
segment */
arena * ap;
psp * pspp, * pspc;
unsigned int i, ccseg;
/* set pspp to psp of this program */
pspp = MK_FP(_psp,0);
#ifdef DEBUG
printf("prog psp=%p\n",pspp);
#endif
/* set pspc to psp of COMMAND.COM, back up a bit to get it if needed */
ccseg = FP_SEG (pspp->prev_crit_error);
if ( (i=ccseg-32) < 60) i=60;
while (ccseg>i) {
pspc = MK_FP (ccseg, 0);
if ( is_valid_arena((arena *) pspc) == 0) goto L1;
ccseg--;
}
return (NULL);
L1: pspc = MK_FP (++ccseg, 0);
#ifdef DEBUG
printf("comm.com=%p\n",pspc);
#endif
/* first see if env seg in command.com points to valid env block
if env seg is in a valid arena, then arena must point to this command.com
else assume env block is fabricated like for 4DOS, use 128 bytes */
ap = MK_FP (pspc->envir_seg-1, 0);
i = ap->num_segments;
if (is_valid_arena (ap) == 0) {
if (ap->psp_segment != FP_SEG(pspc)) goto L2;
} else {
i = 9;
}
if ( is_valid_env (&ap->arena_data, i) == 0 )
return (ap);
/* command.com did not so point, search thru all env blocks */
L2:
if ( (ap=get_first_arena()) != NULL ) {
while (ap->type != LAST_ATYPE) {
#ifdef DEBUG
printf("%p\n",ap);
#endif
if (ap->psp_segment == FP_SEG(pspc) &&
is_valid_env (&ap->arena_data, ap->num_segments)==0 )
return (ap);
ap = get_next_arena(ap);
}
} return(NULL);
} /* end get_arena_of_environment */
/*****************************************************************************/
int settheenv(char * symbol, char * val) {
int total_size,
needed_size=0,
strlength;
char * sp, *op, *envir;
char symb_len=strlen(symbol);
char found=0;
arena * ap;
strupr(symbol);
/* first, can COMMAND.COM's envir block be found ? */
if ( (ap=get_arena_of_environment()) == NULL)
return(1);
/* search to end of the envir block, get sizes */
total_size = 16 * ap->num_segments;
envir = &ap->arena_data;
op=sp=envir;
while (*sp) {
strlength = strlen(sp)+1;
if ( *(sp+symb_len)=='=' &&
strnicmp(sp,symbol,symb_len)==0 )
found=1;
else {
needed_size += strlength;
if (found) strcpy(op,sp);
op = &op[strlength];
}
sp += strlength;
}
*op=0;
if (strlen(val) > 0) {
needed_size += 3 + strlen(symbol) + strlen(val);
if (needed_size > total_size)
return(1); /* could mess with environment expansion here */
strcpy(op, symbol); strcat(op, "="); strcat(op, val);
op += strlen(op)+1;
*op = 0;
}
return(0);
} /* end setheenv subroutine */
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