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SPAWNO v4.00 11/17/91 disk/EMS/XMS/INT15 swapping replacement for spawn()
(c) Copyright 1990,1991 Ralf Brown. All Rights Reserved.
-----------------
LICENSE
This document and the associated header file, libraries, and source and
object modules may be freely copied provided that:
1) all of the files are copied as a group (such as in a single
archive). See below for a list of files.
2) the files are not modified in any way (including removal or
alteration of copyright notices or this license)
3) no charge beyond a cost-recovery fee not to exceed $5, or a
general telecommunications connection fee, is made
The source and/or object code comprising the public SPAWNO distribution
may be incorporated at no charge into programs which are distributed or
sold to others provided that:
1) credit is given in the documentation. A mention such as
"This product uses the SPAWNO routines by Ralf Brown
to minimize memory use while shelling to DOS and
running other programs."
is sufficient.
2) you drop me a line telling me that you are using SPAWNO and
in which product(s) you are using it (see addresses at the
end of this file). I'm interested in finding out how wide-
spread the use of SPAWNO becomes.
-----------------
DISCLAIMER
Although both I and others have tested the code which comprises SPAWNO,
it is entirely possible that SPAWNO may malfunction in environments or
under circumstances in which it has not been tested. This code is
provided AS IS, and the author disclaims any and all responsibility for
damages (both consequential and incidental) resulting from the use or
misuse of SPAWNO. Sole responsibility for determining the suitability
of the code rests with the user.
-----------------
FILES
The disk or archive you received should contain the following files:
SPAWNO.DOC this file
SPAWNO.H the header file providing prototypes for the functions
SPAWNx.LIB versions of the library for each of [T]iny, [S]mall,
[C]ompact, [M]edium, [L]arge, and [H]uge memory
models.
SPAWNTP.OBJ Turbo Pascal version of SPAWNO
SPAWNO.PAS Turbo Pascal unit encapsulating SPAWNO
SPAWN_MS.ZIP Microsoft C versions of compiler-specific functions
MSC.BAT replace Turbo C specific functions in libraries with
Microsoft C versions.
NOREPLAC.BAT remove replacements for the standard spawn..()
functions from the libraries.
SWAPTEST.C example program for testing
TEST.PAS example program for testing
SPWNOSRC.ZIP archive containing partial source code for SPAWNO
_SPAWNO.H header file for recompiling library
*.C source for the spawn..() and spawn...o() functions
RULES.ASI shortened and modified Turbo C macro file
SPAWNO.INC include file for various important constants
SPAWNPTH.ASM source for the path search
CHECKEXT.ASM check for 'file', 'file.EXE', and 'file.COM'
SWAP_EMS.ASM support routines for swapping to EMS
SWAPLIST.ASM specify which swap types will be linked in
SPAWNENV.ASM make an environment block from an array of strings
SPAWNERR.ASM set _doserrno and errno
MAKEFILE
-----------------
INSTALLATION
If you are using Turbo C, Turbo C++, or Borland C++, simply dearchive
the libraries and header file and place them where your compiler can
find them. If you are using Microsoft C, dearchive SPAWN_MS.ZIP and
then run the MSC batch file to replace the compiler-specific functions
in the libraries with Microsoft C versions. Please do not run this
batch file on your original copy of the libraries.
If you are using Turbo Pascal, unarchive SPAWNTP.OBJ and SPAWNO.PAS.
Compile SPAWNO.PAS and then add a USES SPAWNO; line to your program.
After that you can call the function SPAWN() as desired. The
distribution does not contain a pre-compiled version because .TPU
files are not compatible between different versions of Turbo Pascal.
-----------------
INSTRUCTIONS
As distributed, SPAWNO contains replacements for the standard spawn..()
functions. You can use SPAWNO with absolutely no changes to your
existing source code; however, you will probably want to call
init_SPAWNO() from main(), and include SPAWNO.H for that source file.
The initialization function takes two arguments: the first is a string
containing a list of directories (separated by semicolons) in which to
attempt to store the swap file when swapping to disk. The second
specifies which swap devices to attempt to use; it may be either
SWAP_ANY or the ORing or addition of any combination of SWAP_DISK,
SWAP_EMS, SWAP_EXT, and SWAP_XMS (such as SWAP_DISK|SWAP_XMS). If you
do not call init_SPAWNO(), the defaults are to attempt all swap devices
and to store the swap file in the current directory when swapping to
disk. init_SPAWNO() will set the swap file directory list to the first
of the following to have a non-NULL, non-empty value: the environment
variable SWAPDIR, the passed parameter, the environment variable TEMP,
and the environment variable TMP.
After making the above change, recompile your existing code, but include
the SPAWNO library in the link step. Note that SPAWNO does not support
the P_OVERLAY spawn type--any calls using that argument should be
replaced with the corresponding exec..() function. If a SPAWNO function
is called with P_OVERLAY, it simply returns an error.
For backwards compatibility with previous versions of SPAWNO, and for
those who (for whatever reason) require the use of both the swapping and
standard spawn..() functions, there is a second set of functions which
take an explicit swap directory argument. To use them, include the
header file SPAWNO.H. Then use the functions provided in this
archive--spawnvo(), spawnlo(), spawnvpo(), etc--as you would the
corresponding spawnv(), spawnl(), etc, except replace the first argument
by a string containing the path where the swap file is to be stored.
Note that the swap file path is required even when swapping to XMS, EMS,
or plain extended memory, as SPAWNO will swap to disk anyway if there is
not enough memory available.
If you require the use of both the swapping and standard spawn..()
functions, you will need to run the NOREPLAC.BAT batch file to remove
the modules containing the replacements for the standard functions or
arrange the linker command line such that SPAWNx.LIB is listed after the
standard runtime library (for Turbo/Borland C users, the latter requires
a separate TLINK command, as TCC/BCC places any libraries specified on
the command line prior to the runtime library). Please do not run
NOREPLAC on your original copy of the libraries, as the process is
destructive and cannot be reversed.
The spawn?p??() functions search for both .COM and .EXE files in the
current directory and then in the pathed directories if no extension is
given, but use the specified extension if present. If a full pathname
is given to those functions, only the specified directory is searched.
If both a path and an extension are given, only that specific file will
be loaded. The other spawn..() functions check the current directory
only; if the specified filename does not contain an extension, .COM and
.EXE will be tried if the extension-less file does not exist.
When linking, you must include SPAWNx.LIB. A sample TCC line would be
tcc -mc <other-flags> sample spawnc.lib library.lib
This results in 208 to 288 bytes remaining in memory (depending on swap
type) while the spawned program executes. However, if you want to keep
an interrupt hooked which might be invoked while spawned, you must set
__spawn_resident large enough that *all* code and data which could be
invoked by that interrupt is kept resident[1]. SPAWNO automatically
deactivates INT 23h and INT 24h and restores them before returning to
the caller unless __spawn_keepints is set to 1, so no extra work is
required if those two are the only interrupts hooked by the program.
----
[1] Due to the segment layout used by C compilers, this option is probably
useful only when calling SPAWNO from assembly-language code (which can
localize such code and data near the start of the executable) or a
small program which uses a large amount of space in the far heap.
-----------------
ERROR MESSAGES
SPAWNO: stack too small, retrying
SPAWNO did not correctly determine the stack requirements for
the system on which it is running, but was able to determine
that the specified minimum size is insufficient. On the retry,
the stack size is increased by one paragraph. Since SPAWNO
cannot always detect the problem, which would result in
memory chain corruption, you should increase the value of
__spawn_res_stack to prevent a recurrence of this error
message. For most systems, the default value of 4 paragraphs
will be sufficient.
SWAP ERR
The resident stub detected an error while trying to reload the
main portion of the program and aborted. This may be due to
loading a TSR while swapped out or deleting the swap file.
SPAWNO: error reloading program, aborting
The main portion of SPAWNO detected an error while attempting
to restore the remainder of the program to memory.
-----------------
LIMITATIONS
After freeing all memory owned by the program except the initial (PSP)
memory block and the environment, at least 384 bytes of conventional
memory must be available. SPAWNO uses this for its temporary stack.
This is of particular importance for the Turbo Pascal variant, because
setting the maximum heap size to the available memory or greater will
use up all RAM and prevent SPAWNO from allocating its temporary stack
unless memory is fragmented or there is DOS 5 high memory available.
SPAWNO may report insufficient memory even though the program to be
executed would fit with up to 600 bytes to spare, due to the fact that
part of the stack and all of the data used by DOS to start the program
may be overwritten after the child program starts executing.
Functions which pass an explicit environment attempt to allocate enough
memory to build the environment block which is passed to the DOS EXEC
function. If neither malloc() nor a DOS memory allocation request are
successful, SPAWNO passes the original environment rather than the
specified environment.
As distributed, SPAWNO functions which do not take an explicit
environment pointer pass the calling program's original environment to
the child, rather than the current environment as modified by putenv().
You may recompile SPAWNO to pass the current environment (see
_SPAWNO.H); if you do so, the caveat discussed in the previous paragraph
will apply to all of the spawn..() functions.
-----------------
SUPPORT
Since I am not getting any money, I can't promise any support. Those
who have purchased the complete source code will receive priority over
those who haven't, but even they will only receive support to the
extent that I have spare time....
-----------------
ACKNOWLEDGEMENTS
Thanks to Gene McManus for testing the Microsoft versions of SPAWNO 3.0
and 4.0.
-----------------
FUTURE PLANS
The next release will drop support for DOS 2.x (which is now over
seven years old) to reduce the code size and further reduce the size
of the resident stub.
-----------------
SPAWNO versus THE COMPETITION
Product: SPAWNO XSPAWN SWAP
Version: 4.00 1.34 1.0
Author: Ralf Brown Whitney Software Marty Del Vecchio
Memory models: tsmclh tsmclh tsm
Supported DOS vers: 2.0-5.0 2.1-5.0 3.0-5.0
Code size [1]: 4.2-5.6K 4.4-9K 1.5K
Resident stub (bytes): 208-288 1277+2*env 1.8K+env [2]
Direct replacement for
spawn..(): yes yes no
Use in existing code
without changes: yes no no
Swap to disk: yes yes yes
Swap to EMS: yes yes yes
Swap to XMS: yes no no
Swap to INT 15h ext: yes no no
Multiple swap dirs: yes yes no
Automatic unique swap
file naming: yes yes no
May leave interrupts
hooked [3]: yes no yes
Swaps DOS5 high memory: yes ? ?
Free for any use: yes yes yes
Source included: partial [4] yes yes
Notes:
[1] For both SPAWNO and XSPAWN, the amount added to the executable's
size depends on which functions of the library are called and which
of the additional C runtime library function that are called by
SPAWNO/XSPAWN would have been included anyway. SPAWNO's size may
be reduced by removing one or more swap types; the savings are
about 400 bytes per swap type (without EMS and non-XMS (INT 15h)
swapping, SPAWNO would add as little as 3.4K to the executable).
[2] SWAP's resident size depends on the location of the object code
within the executable. The size reported here is the resident
size when SWAP immediately follows the Turbo C 2.0 startup code.
[3] For SPAWNO, enough of the program must be left in memory to keep all
interrupt handlers resident. XSPAWN has no provision for keeping
an interrupt handler resident unless swapping is disabled; it does
however permit selection whether a given interrupt handler will
automatically be restored to its original value or pointed at an
IRET instruction while swapped out. For SWAP, the swapper module
must be linked in after all code and data which might be accessed
by the interrupt handler(s).
[4] Full SPAWNO source code is available for purchase. See ORDER.FRM for
details.
-----------------
Functions:
void init_SPAWNO(const char *swap_directories, int swap_types) ;
/* replacements for the standard functions */
int spawnv(int type, const char *name, const char **args) ;
int spawnvp(int type, const char *name, const char **args) ;
int spawnve(int type, const char *name, const char **args,
const char **env) ;
int spawnvpe(int type, const char *name, const char **args,
const char **env) ;
int spawnl(int type, const char *name, const char *argv0, ...) ;
int spawnlp(int type, const char *name, const char *argv0, ...) ;
int spawnle(int type, const char *name, const char *argv0, ...) ;
int spawnlpe(int type, const char *name, const char *argv0, ...) ;
int system(const char *command) ;
/* Note: the above functions return -1 (error) if 'type' is not */
/* P_WAIT */
/* SPAWNO-specific functions */
int spawnvo(const char *overlay_path, const char *name,
const char **args) ;
int spawnvpo(const char *overlay_path, const char *name,
const char **args) ;
int spawnveo(const char *overlay_path, const char *name,
const char **args,const char **env) ;
int spawnvpeo(const char *overlay_path, const char *name,
const char **args,const char **env) ;
int spawnlo(const char *overlay_path, const char *name, ...) ;
int spawnlpo(const char *overlay_path, const char *name, ...) ;
int spawnleo(const char *overlay_path, const char *name, ...) ;
int spawnlpeo(const char *overlay_path, const char *name, ...) ;
int systemo(const char *overlay_path, const char *command) ;
Global variables:
char __spawn_xms ;
Specify whether to use XMS memory for swapping (if available).
0 = no, 1 = yes, default = 1
This variable is set by init_SPAWNO().
char __spawn_ems ;
Specify whether to use EMS memory for swapping (if available).
0 = no, 1 = yes, default = 1
This variable is set by init_SPAWNO().
char __spawn_ext ; /* 0 = don't use non-XMS extended memory for swap */
Specify whether to use non-XMS extended memory (via INT 15h) for
swapping (if available). 0 = no, 1 = yes, default = 1
This variable is set by init_SPAWNO().
Note: SPAWNO should not be allowed to swap to extended memory if
running under a multitasker or task switcher, as other programs
would be able to grab the same memory used by SPAWNO to store the
swapped-out program. For this reason, SPAWNO automatically
disables swapping to non-XMS extended memory if it detects that
TopView, DESQview, or any other TopView API-compatible multi-
tasker is active, or the DOS 5 task switcher is loaded, or
MS Windows 3 is running in real or standard mode (enhanced mode
is not readily detectable from a program, unfortunately).
const char *pascal ___spawn_swap_dirs ;
Specify the list of directories in which to attempt to store
the swap file when swapping to disk. The directories are
separated by semicolons just as they would be in the PATH
environment variable. Default = "." (current directory)
This variable is set by init_SPAWNO().
Note: SPAWNO will not swap to disk if this variable is set to an
empty string; if it is set to NULL, SPAWNO will use the default
of ".".
char __spawn_keepints ;
Specify whether to deactivate INT 23h and INT 24h handlers by
temporarily restoring the vectors stored in the PSP.
0 = no, nonzero = yes, default = 0
char __spawn_swap_UMA ;
Specify whether to swap out memory blocks in the upper memory
area (640K-1M). 0 = no, 1 = yes, default = 1
Note: This option only has an effect under MSDOS 5.0 with the
line DOS=UMB or DOS=HIGH,UMB in CONFIG.SYS.
unsigned __spawn_resident ;
Specify the minimum number of paragraphs in the memory block
containing the PSP to keep resident while in the child program.
This value will be increased if necessary to be large enough to
hold the swapping code; it may also be increased slightly if it
causes the end of the shrunken PSP block to fall within a
specific section of SPAWNO's code. You may force the entire
main block to stay in memory by setting this variable to 0xFFFF;
however, the environment and any additional memory blocks
allocated by the program will still be swapped out. default = 0
Note: in addition to the PSP memory block, a small second block
is used for the stack needed by the swapping code (see below).
unsigned __spawn_res_stack ;
Specify the minimum number of paragraphs of the stack to keep
resident while in the child program. Default = 4, minimum = 2
(two paragraphs is only sufficient for bare DOS; TSRs which
hook INT 21h will increase the stack requirements, but four is
sufficient for most systems). SPAWNO attempts to compute the
necessary stack size, but this variable allows the computed
value to be overridden if necessary.
External functions called by SPAWNO:
malloc() \ only when passing an array of environment strings
free() /
External variables referenced by SPAWNO:
int errno ;
int _doserrno ;
unsigned int _psp ;
char **environ ; (only when passing an array of environment strings)
Other:
This version of SPAWNO overwrites the PSP, so the commandline
will be lost unless it was copied before the first spawn().
-----------------
Functions (Turbo Pascal):
init_SPAWNO(swap_dirs : string ; swap_types : integer ;
min_resident : integer ; resident_stack : integer) ;
spawn(program_name : string ; arguments : string ;
envseg : integer) : integer ;
Global Variables (Turbo Pascal):
spawno_error : integer ; (error code when spawn() returns -1)
-----------------
Send comments, bug reports, etc. to
Internet: ralf+@cs.cmu.edu
Fidonet: Ralf Brown 1:129/26.1 (or post a message to me on DR_DEBUG--I
have to route netmail outside Zone 1
via Internet -> Fidonet gateways, which
is not always reliable)
or
Ralf Brown
Suite #26
813 Copeland Way
Pittsburgh, PA 15232