gpxe/contrib/romid/setenvs.c

   1 /* subroutine to put a value string into an environment symbol.
   2    Uses the controling command.com environment, not the programs.
   3    This means that the env variable is set so other routines in
   4    a .BAT file may use it.
   5
   6    call:  settheenv (char * symbol, char * val);
   7    symbol is an asciiz string containing the env variable name,
   8    val    is an asciiz string containing the value to assign to this vbl.
   9
  10    returns: 0 = OK,
  11             1 = failure.
  12    failure is not unlikely.  The env block may be full.  Or on some
  13    systems the env block might not be found
  14
  15    SETENVS.C was written by Richard Marks <rmarks@KSP.unisys.COM>.
  16 */
  17
  18
  19 #include <stdio.h>
  20 #include <dos.h>
  21 #include <string.h>
  22 #include <stdlib.h>
  23
  24 typedef struct {
  25     char fill1[0x0A];
  26     int *prev_term_handler;
  27     int *prev_ctrl_c;
  28     int *prev_crit_error;
  29     char fill2[0x16];
  30     int  envir_seg;
  31 } psp;
  32
  33 typedef struct {
  34     char  type;
  35     int   psp_segment;
  36     int   num_segments;
  37     char  fill[11];
  38     char  arena_data;
  39 } arena;
  40
  41
  42 #define NORMAL_ATYPE 0x4D
  43 #define LAST_ATYPE   0x5A
  44
  45
  46 static arena * get_next_arena (arena * ap) {
  47     return( MK_FP( FP_SEG(ap)+1+ap->num_segments, 0) );
  48 }
  49
  50 /* returns 0 if passed pointer is to an arena, else returns 1 */
  51 static int is_valid_arena (arena * ap) {
  52     arena * ap1;
  53     if (ap->type == NORMAL_ATYPE  &&
  54           (ap1=get_next_arena(ap))->type == NORMAL_ATYPE  &&
  55           ( (ap1=get_next_arena(ap1))->type == NORMAL_ATYPE  ||
  56           ap1->type == LAST_ATYPE) )
  57             return(0);
  58     return (1);
  59 }
  60
  61
  62 static arena * get_first_arena () {
  63 /* return pointer to the first arena.
  64  * scan memory for a 0x4D on a segment start,
  65  * see if this points to another two levels of arena
  66  */
  67     arena * ap, * ap1;
  68     int * temp;
  69     int segment;
  70
  71     for (segment=0; segment<_CS;  segment++) {
  72         ap = MK_FP(segment, 0);
  73         if ( is_valid_arena (ap) == 0)  return (ap);
  74     }
  75     return(NULL);
  76 } /* end get_first_arena */
  77
  78
  79 static int is_valid_env (char * ad, int num_segs) {
  80     char * base_ad;
  81     base_ad = ad;
  82     while ( (*ad) && (((ad-base_ad)>>4) < num_segs) ) {
  83         if (strnicmp(ad, "COMSPEC=", 8)==0)  return(0);
  84         ad += strlen(ad) + 1;
  85     }
  86     return (1);
  87 }
  88
  89
  90 static arena * get_arena_of_environment () {
  91 /* to get the arena of first environment block:
  92    First get segment of COMMAND.COM from segment of previous critical err code.
  93    Then scan all the arenas for an environment block with a matching PSP
  94    segment */
  95
  96 arena * ap;
  97 psp   * pspp, * pspc;
  98 unsigned int i, ccseg;
  99
 100 /* set pspp to psp of this program */
 101 pspp = MK_FP(_psp,0);
 102
 103 #ifdef DEBUG
 104 printf("prog psp=%p\n",pspp);
 105 #endif
 106
 107 /* set pspc to psp of COMMAND.COM, back up a bit to get it if needed */
 108 ccseg = FP_SEG (pspp->prev_crit_error);
 109 if ( (i=ccseg-32) < 60)  i=60;
 110
 111 while (ccseg>i) {
 112     pspc = MK_FP (ccseg, 0);
 113     if ( is_valid_arena((arena *) pspc) == 0)  goto L1;
 114     ccseg--;
 115 }
 116 return (NULL);
 117
 118 L1: pspc = MK_FP (++ccseg, 0);
 119 #ifdef DEBUG
 120 printf("comm.com=%p\n",pspc);
 121 #endif
 122
 123 /* first see if env seg in command.com points to valid env block
 124    if env seg is in a valid arena, then arena must point to this command.com
 125    else assume env block is fabricated like for 4DOS, use 128 bytes */
 126
 127 ap = MK_FP (pspc->envir_seg-1, 0);
 128 i  = ap->num_segments;
 129
 130 if (is_valid_arena (ap) == 0) {
 131     if (ap->psp_segment != FP_SEG(pspc))  goto L2;
 132 } else {
 133     i = 9;
 134 }
 135
 136 if ( is_valid_env (&ap->arena_data, i) == 0 )
 137     return (ap);
 138
 139 /* command.com did not so point, search thru all env blocks */
 140
 141 L2:
 142 if ( (ap=get_first_arena()) != NULL ) {
 143     while (ap->type != LAST_ATYPE) {
 144 #ifdef DEBUG
 145         printf("%p\n",ap);
 146 #endif
 147         if (ap->psp_segment == FP_SEG(pspc) &&
 148             is_valid_env (&ap->arena_data, ap->num_segments)==0 )
 149             return (ap);
 150
 151         ap = get_next_arena(ap);
 152     }
 153 } return(NULL);
 154 }  /* end get_arena_of_environment */
 155
 156 /*****************************************************************************/
 157
 158 int settheenv(char * symbol, char * val) {
 159 int total_size,
 160     needed_size=0,
 161     strlength;
 162 char * sp, *op, *envir;
 163 char symb_len=strlen(symbol);
 164 char found=0;
 165 arena * ap;
 166
 167 strupr(symbol);
 168
 169 /* first, can COMMAND.COM's envir block be found ? */
 170 if ( (ap=get_arena_of_environment()) == NULL)
 171     return(1);
 172
 173 /* search to end of the envir block, get sizes */
 174 total_size = 16 * ap->num_segments;
 175 envir = &ap->arena_data;
 176 op=sp=envir;
 177 while (*sp) {
 178     strlength = strlen(sp)+1;
 179     if ( *(sp+symb_len)=='='  &&
 180          strnicmp(sp,symbol,symb_len)==0 )
 181         found=1;
 182     else {
 183         needed_size += strlength;
 184         if (found) strcpy(op,sp);
 185         op = &op[strlength];
 186     }
 187     sp += strlength;
 188 }
 189 *op=0;
 190 if (strlen(val) > 0) {
 191     needed_size += 3 + strlen(symbol) + strlen(val);
 192     if (needed_size > total_size)
 193         return(1);  /* could mess with environment expansion here */
 194
 195     strcpy(op, symbol); strcat(op, "="); strcat(op, val);
 196     op += strlen(op)+1;
 197     *op = 0;
 198 }
 199 return(0);
 200 } /* end setheenv subroutine */