BSD 4_3 development

[unix-history] / usr / src / games / compat / unixstart.c

#ifndef lint
static char sccsid[] = "        unixstart.c     4.2     84/05/05        ";
#endif

/* From Lou Salkind: compat/RCS/unixstart.c,v 1.2 84/01/31 13:34:27 */

/*      Start up a version 6 or version 7 pdp-11 UNIX compatability mode
*      program. Must set up the memory layout with args etc.
*      Art Wetzel      August 1979
*/
#include <stdio.h>
#include "defs.h"
#define MAXARGS 100
start(argv, envp) unsigned char **argv, **envp; {
       register unsigned char *sp, *ap;
       register unsigned short *ssp;
       register int i, argc, envc;
       unsigned char *envps[MAXARGS], *argps[MAXARGS], **av, *p1, *p2;
       extern unsigned char *progname, *nameend;
       /* set up initial memory layout for unix */
       /* set stack pointer to top of memory */
       sp = memsiz;
#ifdef  V7UNIX
       /* zero top 2 bytes */
       *(--sp) = 0;
       *(--sp) = 0;
       /* point to environment pointer list */
       av = envp;
       envc = 0;
       /* count up number of env elements */
       while(*(av++)) envc++;
       /* last UNIX V7 env ptr is 0 */
       envps[envc] = (unsigned char *)0;
       /* copy actual environment (assume byte text) - last first */
       for(i=envc-1; i>=0; i--) {
               ap = envp[i];
               while(*(ap++)) ;
               while(ap != envp[i]) *(--sp) = *(--ap);
               /* force stack word alignment - required per arg in v7 */
               if((int)sp & 1) {
                       ap = sp--;
                       while((*(ap-1) = *ap)) ap++;
               }
               envps[i] = sp;
       }
#endif
       /* point to argument pointer list */
       av = argv;
       argc = 0;
       /* count up number of args */
       while(*(av++)) argc++;
#ifdef V7UNIX
       /* last UNIX V7 arg ptr is 0 */
       argps[argc] = (unsigned char *)0;
#endif
#ifdef V6UNIX
       /* last UNIX V6 arg ptr is -1 */
       argps[argc] = (unsigned char *)-1;
#endif
       /* copy actual arguments (assume byte text) - last first */
       for(i=argc-1; i>=0; i--) {
               ap = argv[i];
               while(*(ap++)) ;
               while(ap != argv[i]) *(--sp) = *(--ap);
               /* force stack word alignment - required per arg in v7 */
               if((int)sp & 1) {
                       ap = sp--;
                       while((*(ap-1) = *ap)) ap++;
               }
               argps[i] = sp;
       }
       ssp = (unsigned short *)sp;
#ifdef  V7UNIX
       /* set up environment pointers */
       for(i=envc; i>=0; i--) {
               *(--ssp) = (short)(long)envps[i];
       }
#endif
       /* set up argument pointers */
       for(i=argc; i>=0; i--) {
               *(--ssp) = (short)(long)argps[i];
       }
       /* then argument count */
       *(--ssp) = argc;
       /* set up stack pointer */
       regs[6] = (int)ssp;
       /* set up a psl with cleared condition codes */
       psl = 0x83c00000;
       /* copy out part of the program name and args where ps can get them */
       /* flag it with a * so it shows up as a compatability mode process */
       /* check for case with no env and reset nameend */
       if(nameend < progname) nameend = (unsigned char *)2147483647;
       for(p1=progname, *p1++ = '*', i=1, p2=argv[0]; p1<nameend; p1++) {
               if((*p1 = *p2))
                       p2++;
               else if(argv[i])
                       p2 = argv[i++];
               else break;
       }
       while(p1 < nameend) *p1++ = ' ';
       *p1 = 0;
       /* clear out registers other than sp */
       regs[0] = 0;
       regs[1] = 0;
       regs[2] = 0;
       regs[3] = 0;
       regs[4] = 0;
       regs[5] = 0;
       /* finally get around to actually starting up in compatability mode */
       incompat++;
       compat();
}