chu@pioneer.arc.nasa.gov (Susie Chu RCS) (03/31/91)
Can someone tell me how to change the number of files that can
be open simutaaneously?
My system is runing MSDOS 4.1 and I am using Turbo C 2.0.
I have a program that needs to open more than 20 files. I
have tried to
(1) in config.sys, change FILES=35
(2) in Turbo C 2.0 include/stdio.h, change
#define OPEN_MAX 35
#define SYS_OPEN 355
(3) in Turbo C 2.0 include/dos.h, change
#define NFDS 35
It doesn't help. I still failed in openning 21st file. I suspect
it is in the libc. But I don't know how to check and modify it.
If you do know, please tell me. I will appreciate very much.
Thanks in advance.
---Susie Chu
net address: chu@pioneer.arc.nasa.gov
UUCP: {ihnp4,ucbvax,nike,lll-crg}!ames!pioneer!chu
Disclaimer: NASA is in no way responsible for the content of the previous mes-
sag I take full and sole responsibility.tabu6@CCVAX.IASTATE.EDU (Adam Goldberg) (04/01/91)
In article <1991Mar31.011139.8147@news.arc.nasa.gov>, chu@pioneer.arc.nasa.gov (Susie Chu RCS) writes: >Can someone tell me how to change the number of files that can >be open simutaaneously? >My system is runing MSDOS 4.1 and I am using Turbo C 2.0. >I have a program that needs to open more than 20 files. I >have tried to >(1) in config.sys, change FILES=35 >(2) in Turbo C 2.0 include/stdio.h, change > #define OPEN_MAX 35 > #define SYS_OPEN 355 >(3) in Turbo C 2.0 include/dos.h, change > #define NFDS 35 >It doesn't help. I still failed in openning 21st file. I suspect Try adding to config.sys the line: BUFFERS=35 (though that'll eat up RAM, it seems likely that you don't have enough buffers). +----------------------------------------------------------------------------+ + Adam Goldberg Bitnet: tabu6@ISUVAX.BITNET + + Iowa State University Internet: tabu6@CCVAX.IASTATE.EDU + + "It's simple! Even a Pascal programmer could do it!" + + "Remember: The sooner you fall behind, the more time you have to catch up" + +----------------------------------------------------------------------------+
bwilliam%peruvian.utah.edu@cs.utah.edu (Bruce R. Williams) (04/01/91)
In article <1991Mar31.213543.28347@news.iastate.edu> tabu6@CCVAX.IASTATE.EDU writes: >In article <1991Mar31.011139.8147@news.arc.nasa.gov>, chu@pioneer.arc.nasa.gov (Susie Chu RCS) writes: >>Can someone tell me how to change the number of files that can >>be open simutaaneously? >>My system is runing MSDOS 4.1 and I am using Turbo C 2.0. >>I have a program that needs to open more than 20 files. I >>have tried to >>(1) in config.sys, change FILES=35 [...] > >Try adding to config.sys the line: > BUFFERS=35 >(though that'll eat up RAM, it seems likely that you don't have enough >buffers). Hi! I think I can help with this... It isn't a matter of how many buffers you have, it's a limit set inside DOS. You're not stuck though... With MS-DOS Versions 3.3 and later, there is a DOS function (int 21h, function 67h), which allows you to specify the max. number of files that may be open at one time. Previous versions of DOS were limited to at most 20. Since you are using MS-DOS 4.01 this will work. If you need to write code that is compatable with older versions, there is a work-around that involves using your own table of file handles instead of DOS's. See "MS-DOS Advanced Programming" by Michael J. Young for a good example. To use the DOS function: Set AH to 67h, Set BX to the new max number of file handles. Call Int 21h Upon return, if CF is 1 then there was an error and the error code is stored in AX. Using Turbo C, this can all be done either by using inline assembly, or by using one of the C functions for calling interrupts: intdos, int86, intr etc. Good Luck! I hope this was clear -- otherwise feel free to e-mail. -Bruce Bruce R. Williams "The most beautiful thing we can experience University of Utah is the mysterious. It is the source of all (bwilliam@peruvian.utah.edu) true art and science." -Albert Einstein
raymond@math.berkeley.edu (Raymond Chen) (04/02/91)
In article <1991Apr1.023910.22196@hellgate.utah.edu>, bwilliam%peruvian (Bruce R. Williams) writes: >It isn't a matter of how many buffers you have, it's a limit set inside DOS. Actually, it's a limit that Borland stupidly hard-coded into their library support routines. If you study the library source code, you'll see a line that says #define NFILES 20 and then external arrays _openfd and _iobuf declared to be NFILES elements long. (I may have the array names wrong; I'm working from memory.) The number twenty is HARD-CODED into all of the I/O support routines (fopen, read, seek, etc.), so the only way to get around the limit is either [1] Buy the TC source code, change the #define and recompile. [2] Reverse-engineer the library object code and change the 20 to a larger number in all of the functions where it appears, as well as deleting the OBJs that declare _iobuf and _openfd and adding replacements that declare them with a larger size. [3] Avoid the supplied functions and talk to DOS directly. [4] Switch to a different compiler. (MSC comes with instructions in one of its README files on how to increase the number of open files.) I can probably help anyone who wants to try method [2].
dwayne@stratsft.UUCP (Dwayne Bailey) (04/02/91)
In article <1991Mar31.011139.8147@news.arc.nasa.gov> chu@pioneer.arc.nasa.gov (Susie Chu RCS) writes: >Can someone tell me how to change the number of files that can >be open simutaaneously? >My system is runing MSDOS 4.1 and I am using Turbo C 2.0. >I have a program that needs to open more than 20 files. I >have tried to >(1) in config.sys, change FILES=35 >(2) in Turbo C 2.0 include/stdio.h, change > #define OPEN_MAX 35 > #define SYS_OPEN 355 >(3) in Turbo C 2.0 include/dos.h, change > #define NFDS 35 >It doesn't help. I still failed in openning 21st file. I suspect >it is in the libc. But I don't know how to check and modify it. > >If you do know, please tell me. I will appreciate very much. >Thanks in advance. >---Susie Chu > Two things are probably biting you. One is that MS-DOS gives each and every process EXACTLY 20 file handles at startup, no matter what is in CONFIG.SYS. The FILES= line controls the TOTAL number of files open, not the number of files for one process. Thus, your TSRs can have files open without interfering with the 20 file handles of your main program. The other problem is that thos #defines you changed had very little effect, if any. They tell your program the size of some external arrays. You lied to your program about those arrays, BUT YOU DIDN'T ACTUALLY CHANGE THEIR SIZE! To do that, you would need access to the source code for the Runtime Library, and recompile with your changes. There are workarounds. The DOS limit is easy, since you are using 4.0 This code will only work in DOS 3.3 and higher. /* Routine to set the maximum handles allowed to other than 20 */ /* Returns 0 on success, DOS Error number on failure */ int SetHandleLimit(int MaxHandles) { int Result = 0; asm { mov ah,67h ; This might need to be 0x67. I can't ; remember which style HEX number TC ; wants here. mov bx,MaxHandles int 21h ; Ditto the above comment jnc NoError mov Result,ax NoError: } return Result; } Add a line like "SetHandleLimit(25);" to increase the limit to 35. The only reason this should fail is if there is not enough memory for DOS to allocate a 35 byte table for the new handles. BTW, this can be dome is versions of DOS below 3.3, but it's ugly. There is no function to do it for you. You have to allocate the table youself, then set the far pointer to the table in you PSP at offset 34h. The word at 32h must also be set to the number of entries on the new table. Now for Turbo C: If you don't need stream IO (FILE * type files), then you can get around the Runtime library by using just the low-level calls. I would use _dos_open() to open the files, rather than open(), just to be sure you are at a low enough level to get past the runtime library. If you DO need stream IO, you might be able to do the same thing. You would just need some extra steps. Be warned, this paragraph is total conjecture on my part. I have not tried is, and make no warranties, expressed or implied! That said, the following MIGHT work: 1. Open the file(s) using _dos_open(). 2. Use fdopen() to associate the file handle with a stream. 3. Process the file as before. 4. Close the file. This doesn't give you more than 20 streams at one time, but as long as you aren't swapping back and forth between files TOO much, the performance hit shouldn't be too bad. You could also try using a call to dup() to make a copy of the file handle after set 1. That way, the close in step 4 will not close the file completely, just remove its association with the stream pointer. If this works, I suspect it will meet your needs the best. However, I still recomment that, if at all possible, use only low level calls, and avoid a ton of headaches. Or buy the Runtime Library source. The money spent will most likely be saved in time and aggravation! ======================================================================== ..!uunet!basfpac!stratsft!dwayne Dwayne Bailey + Strategic Software is ME, so my opinions ARE those Strategic Software + of my company! ========================================================================