+/*
+
+ * Copyright (c) 1984, 1985, 1986 AT&T
+ * All Rights Reserved
+
+ * THIS IS UNPUBLISHED PROPRIETARY SOURCE
+ * CODE OF AT&T.
+ * The copyright notice above does not
+ * evidence any actual or intended
+ * publication of such source code.
+
+ */
+/* @(#)vfork.c 1.1 */
+/*
+ * UNIX shell
+ *
+ * S. R. Bourne
+ * Rewritten by David Korn
+ * Bell Telephone Laboratories
+ *
+ */
+
+#include "flags.h"
+#include "defs.h"
+#include "sym.h"
+#include "name.h"
+#include "io.h"
+#include "stak.h"
+#include "jobs.h"
+#include "builtins.h"
+#include "brkincr.h"
+#include "mode.h"
+
+/*
+ * This module is provided to allow the Shell to work with vfork instead
+ * of fork. With vfork the data area is shared by parent and child.
+ * Save state variables at fork and make Shell variables copy on write.
+ * Restore everything to previous state when fork_exit is called and
+ * terminate process.
+ */
+
+/* The following structure contains the variables that must be saved */
+struct f_save
+{
+ struct f_save *f_save_fork;
+ DOLPTR f_savearg;
+ STKPTR f_staksave;
+ struct State f_st;
+ char f_trapflg[MAXTRAP+1];
+ char *f_trapcom[MAXTRAP+1];
+ FILE f_save_iob[FCIO+1];
+ struct jobs f_jobstat;
+};
+
+/* The following routines are defined by this module */
+int vfork_check();
+void vfork_restore();
+int vfork_save();
+
+/* The following external routines are referenced by this module */
+extern DOLPTR arg_use();
+extern void arg_free();
+extern NAMPTR checkfor();
+extern unsigned chkid();
+extern void free();
+extern char *malloc();
+extern struct Amemory *namep;
+extern char *simple();
+extern char trapflg[];
+extern char *valup();
+
+static struct f_save *save_fork; /* most recently saved data */
+
+/*
+ * Save state on fork
+ */
+
+int vfork_save()
+{
+ register struct f_save *fp = (struct f_save*)malloc(sizeof(struct f_save));
+ if(fp==NULL)
+ return(-1);
+ locstak();
+ fp->f_save_fork = save_fork;
+ save_fork = fp;
+ fp->f_staksave = savstak();
+ fp->f_st = st;
+ fp->f_jobstat = jobstat;
+ jobstat.p_pwlist = 0;
+ fp->f_savearg = arg_use();
+ bcopy(trapflg,fp->f_trapflg,MAXTRAP+1);
+ bcopy((char*)trapcom,(char*)fp->f_trapcom,(MAXTRAP+1)*sizeof(char*));
+#ifdef _N_STATIC_IOBS
+ bcopy((char*)_iob,(char*)fp->f_save_iob,(_N_STATIC_IOBS)*sizeof(FILE));
+ bcopy((char*)_myiob,(char*)(fp->f_save_iob+_N_STATIC_IOBS),
+ (FCIO+1-_N_STATIC_IOBS)*sizeof(FILE));
+#else
+ bcopy((char*)_iob,(char*)fp->f_save_iob,(FCIO+1)*sizeof(FILE));
+#endif /* _N_STATIC_IOBS */
+ states |= VFORKED;
+ return(0);
+}
+
+/*
+ * Restore state and exit
+ */
+
+void vfork_restore()
+{
+ register struct f_save *fp = save_fork;
+ if((states&VFORKED)==0)
+ return;
+#ifdef _N_STATIC_IOBS
+ bcopy((char*)fp->f_save_iob,(char*)_iob,(_N_STATIC_IOBS)*sizeof(FILE));
+ bcopy((char*)(fp->f_save_iob+_N_STATIC_IOBS),(char*)_myiob,
+ (FCIO+1-_N_STATIC_IOBS)*sizeof(FILE));
+#else
+ bcopy((char*)fp->f_save_iob,(char*)_iob,(FCIO+1)*sizeof(FILE));
+#endif /* _N_STATIC_IOBS */
+ bcopy(fp->f_trapflg,trapflg,MAXTRAP+1);
+ bcopy((char*)fp->f_trapcom,(char*)trapcom,(MAXTRAP+1)*sizeof(char*));
+ st = fp->f_st;
+ jobstat = fp->f_jobstat;
+ arg_free(fp->f_savearg,0);
+ save_fork = fp->f_save_fork;
+ free(fp);
+ tdystak(fp->f_staksave);
+}
+
+
+/*
+ * Get the interpreter name given a script file
+ * The first line must be of the form #! <iname>.
+ * Returns 1 if <iname> is found, 0 otherwise
+ */
+int get_shell(name,iname)
+char *name;
+char *iname;
+{
+ register int c;
+ register int state = 0;
+ register int fd;
+ int n;
+ char *cp;
+ int rval = 0;
+ char buffer[256];
+ cp = valup(SHELLNOD);
+ /* don't use csh */
+ if(strcmp(simple(cp),"csh")==0)
+ cp = 0;
+ strcpy(iname,cp?cp:"/bin/sh");
+ if((fd=open(name,0))<0)
+ return(-1);
+ n = read(fd,buffer,sizeof(buffer));
+ cp = buffer;
+ while(n-- > 0)
+ {
+ c = *cp++;
+ switch(state)
+ {
+ case 0:
+ if(c!='#')
+ goto out;
+ break;
+
+ case 1:
+ if(c!='!')
+ goto out;
+ break;
+
+ case 2:
+ if(c==' ' || c =='\t')
+ continue;
+ default:
+ if(c=='\n')
+ {
+ *iname = 0;
+ rval = 1;
+ goto out;
+ }
+ *iname++ = c;
+ }
+ state++;
+ }
+out:
+ close(fd);
+ return(rval);
+}
+
+/*
+ * returns non-zero if process should vfork, 0 otherwise
+ * we do not vfork for functions and built-ins in the background
+ */
+int vfork_check(t)
+TREPTR t;
+{
+ register COMPTR tf;
+ register ARGPTR arg;
+ register char *arg0 = NIL;
+ NAMPTR np;
+ int bltno;
+ /* simple command */
+ if((t->tretyp&COMMSK)==TCOM)
+ return(1);
+ tf = (COMPTR)(((FORKPTR)t)->forktre);
+ if((tf->comtyp&COMMSK)!=TCOM)
+ return(0);
+ /* background command */
+ arg = tf->comarg;
+ bltno = tf->comtyp>>(COMBITS+1);
+ /* can't vfork assignments or most built-ins */
+ if(arg==0 || bltno > SYSLOGIN)
+ return(0);
+ if(tf->comtyp&COMSCAN)
+ {
+ if(arg->argflag&A_RAW)
+ arg0 = arg->argval;
+ }
+ else
+ arg0 = *(((DOLPTR)arg)->dolarg+1);
+ /* no vfork if not sure */
+ if(arg0==NIL)
+ return(0);
+ /* eliminate functions */
+ if(chkid(arg0) && (np=checkfor(arg0,prnames))&& np->value.namval.ip)
+ return(0);
+ /* command substitution with i/o redirection use fork */
+ if((t->tretyp&FCOMSUB) && t->treio==(IOPTR)0)
+ return(0);
+ return(2);
+}
+
+#ifndef BSD_4_2
+/*
+ * copy <n> bytes from <sp> to <dp>
+ */
+
+int bcopy(sp,dp,n)
+register char *sp, *dp;
+register int n;
+{
+ while(n-- >0)
+ *dp++ = *sp++;
+}
+#endif BSD_4_2
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