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Power Programmierung
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Power-Programmierung (Tewi)(1994).iso
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05
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swap
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exec.c
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C/C++ Source or Header
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1990-09-01
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9KB
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333 lines
/*
EXEC function with memory swap.
Needs Assembler file 'spawn.asm'.
Public domain software by
Thomas Wagner
Ferrari electronic GmbH
Beusselstrasse 27
D-1000 Berlin 21
West Germany
BIXname: twagner
*/
#include "compat.h"
#include <ctype.h>
extern int do_exec (char *xfn, char *pars, int spwn, unsigned needed,
char **envp);
/*
The EXEC function.
Parameters: xfn is a string containing the name of the file
to be executed. If the string is empty,
the COMSPEC environment variable is used to
load a copy of COMMAND.COM or its equivalent.
If the filename does not include a path, the
current PATH is searched after the default.
If the filename does not include an extension,
the path is scanned for a COM or EXE file in
that order.
pars The program parameters.
spwn If 1, the function will return, if necessary
after swapping the memory image.
If -1, EMS will not be used when swapping.
If 0, the function will terminate after the
EXECed program returns.
NOTE: If the program file is not found,
the function will always return
with the appropriate error code, even if
'spwn' is 0.
needed The memory needed for the program in
paragraphs. If not enough memory is free, the
program will be swapped out. Use 0 to never
swap, 0xffff to always swap. If 'spwn' is false,
this parameter is irrelevant.
envp The environment to be passed to the spawned
program. If this parameter is NULL, a copy
of the parent's environment is used (i.e.
'putenv' calls have no effect). If non-NULL,
envp must point to an array of pointers to
strings, terminated by a NULL pointer (the
standard variable 'environ' may be used).
Return value:
0x0000..00FF: The EXECed Program's return code
(0..255 decimal)
0x0100: Error writing swap file
(256 decimal)
0x0200: Program file not found
(512 decimal)
0x03xx: DOS-error-code xx calling EXEC
(768..1023 decimal)
0x0400: Error allocating environment buffer
(1024 decimal)
*/
#define SWAP_FILENAME "$$AAAAAA.AAA"
#define M_SWAPPING 0x01
#define M_USE_EMS 0x02
#define M_CREAT_TEMP 0x04
#define M_EXEC 0x80
extern int do_spawn (unsigned char method,
char *swapfn, char *xeqfn, char *cmdtail,
unsigned envlen, char *envp);
int exists (char *fn)
/* Returns TRUE if a file with name 'fn' exists. */
{
struct ffblk fb;
return !findfirst (fn,
&fb,
FA_RDONLY | FA_HIDDEN | FA_SYSTEM | FA_ARCH);
}
int tryext (char *fn)
/* Try '.COM' and '.EXE' on current filename, modify filename if found. */
{
int i;
i = strlen (fn);
strcat (fn, ".COM");
if (exists (fn))
return 1;
fn [i] = 0;
strcat (fn, ".EXE");
if (exists (fn))
return 1;
fn [i] = 0;
return 0;
}
int findfile (char *fn)
/* Try to find the file 'fn' in the current path. Modifies the filename
accordingly. */
{
char path [256];
char *prfx;
int found;
char drive [MAXDRIVE], dir [MAXDIR], name [MAXFILE], ext [MAXEXT];
if (!fn [0])
strcpy (fn, getenv ("COMSPEC"));
fnsplit (fn, drive, dir, name, ext);
if (ext [0])
found = exists (fn);
else
found = tryext (fn);
if (!found && !dir [0] && !drive [0])
{
strcpy (path, getenv ("PATH"));
prfx = strtok (path, ";");
while (!found && prfx != NULL)
{
fnmerge (fn, drive, prfx, name, ext);
if (ext [0])
found = exists (fn);
else
found = tryext (fn);
prfx = strtok (NULL, ";");
}
}
return found;
}
/*
tempdir: Set temporary file path.
Read "TMP/TEMP" environment. If empty or invalid, clear path.
If TEMP is drive or drive+backslash only, return TEMP.
Otherwise check if given path is a valid directory.
If so, add a backslash, else clear path.
*/
void tempdir (char *outfn)
{
int l;
char drive [MAXDRIVE], dir [MAXDIR];
char name [MAXFILE], ext [MAXEXT];
char *s;
struct stat ff;
union REGS regs;
struct SREGS segregs;
*outfn = 0;
if ((s = getenv ("TMP")) == NULL)
if ((s = getenv ("TEMP")) == NULL)
return;
strcpy (outfn, s);
l = strlen (outfn);
if (!l)
return;
if (outfn [l - 1] == '\\' || outfn [l - 1] == '/')
outfn [--l] = 0;
fnsplit (outfn, drive, dir, name, ext);
if (drive [0])
{
regs.h.dl = toupper (drive [0]) - 'A' + 1;
regs.h.ah = 0x1c;
intdosx (®s, ®s, &segregs);
if (regs.h.al == 0xff)
{
*outfn = 0;
return;
}
}
if (!name [0]) /* No dir name */
{
if (dir [0])
*outfn = 0;
else
{
outfn [l++] = '\\';
outfn [l] = 0;
}
return;
}
if (stat (outfn, &ff))
*outfn = 0;
else if (!(ff.st_mode & S_IFDIR) || !(ff.st_mode & S_IWRITE))
*outfn = 0;
else
{
outfn [l++] = '\\';
outfn [l] = 0;
}
}
int do_exec (char *exfn, char *epars, int spwn, unsigned needed, char **envp)
{
char swapfn [80];
char xfbuf [80];
char *xfn;
char pars [130];
unsigned avail;
union REGS regs;
unsigned envlen, rc;
int idx;
char **env;
char *ep, *envbuf;
unsigned char method;
xfn = &xfbuf [1];
strcpy (xfn, exfn);
strcpy (&pars [1], epars);
pars [0] = (char)strlen (epars);
/* First, check if the file to execute exists. */
if (!findfile (xfn))
return 0x200;
/* Now create a copy of the environment if the user wants it. */
envlen = 0;
if (envp != NULL)
for (env = envp; *env != NULL; env++)
envlen += strlen (*env) + 1;
if (envlen)
{
envlen++;
ep = envbuf = malloc (envlen);
if (envbuf == NULL)
return 0x400;
for (env = envp; *env != NULL; env++)
{
ep = stpcpy (ep, *env) + 1;
}
*ep = 0;
}
xfbuf [0] = (char)strlen (xfn);
if (!spwn)
method = M_EXEC; /* Mark 'EXEC' function */
else
{
/* Determine amount of free memory */
regs.x.ax = 0x4800;
regs.x.bx = 0xffff;
intdos (®s, ®s);
avail = regs.x.bx;
/* No swapping if available memory > needed */
if (needed < avail)
method = 0;
else
{
/* Swapping necessary, use 'TMP' or 'TEMP' environment variable
to determine swap file path if defined. */
method = (unsigned char)
((spwn < 0) ? M_SWAPPING : M_SWAPPING | M_USE_EMS);
swapfn [0] = 1; /* dummy length byte */
tempdir (&swapfn [1]);
if (OS_MAJOR >= 3)
method |= M_CREAT_TEMP;
else
{
strcat (swapfn, SWAP_FILENAME);
idx = strlen (swapfn) - 1;
while (exists (swapfn))
{
if (swapfn [idx] == 'Z')
idx--;
if (swapfn [idx] == '.')
idx--;
swapfn [idx]++;
}
}
}
}
/* All set up, ready to go. */
rc = do_spawn (method, swapfn, xfbuf, pars, envlen, envbuf);
/* Free the environment buffer if it was allocated. */
if (envlen)
free (envbuf);
return rc;
}