how to fill file with 0

[david]

using MASM,
The size of complied file is 3K, I want to extend file to 32K, and fill file with 0.
how to do ?

[bluecode]

Under which operating system?

[JamesM]

MASM - can only be windows.

[bluecode]

Well, I meant which environment david targets, ie. a userspace Windows/Linux/DOS/whatever application or soem freestanding stuff... The hosting environment is not really important.

[01000101]

I have no idea about doing it in a low language like that, but i know in C# you can read the bytes of the file, then increase the size of bytes, and re-make a replica file but with the extension.

[inflater]

using MASM,
The size of complied file is 3K, I want to extend file to 32K, and fill file with 0.
how to do ?

Simple as it gets, add this to the end:

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times 32768-($-$$) db 0

Don't know if it will work in MASM, if not, try DB 0 DUP (...).

MASM - can only be windows.

You're wrong, it can be DOS too.

[Dex]

maybe

The DUP Operator
You can also declare an array with the DUP operator. This operator works with any of the data allocation directives described in "Allocating Memory for Integer Variables" in Chapter 4. In the syntax

count DUP (initialvalue [[, initialvalue]]...)
the count value sets the number of times to repeat all values within the parentheses. The initialvalue can be an integer, character constant, or another DUP operator, and must always appear within parentheses. For example, the statement
barray BYTE 5 DUP (1)
allocates the integer 1 five times for a total of 5 bytes.

The following examples show various ways to allocate data elements with the DUP operator:
array DWORD 10 DUP (1) ; 10 doublewords
                                              ;   initialized to 1
buffer  BYTE    256 DUP (?)                   ; 256-byte buffer

masks   BYTE    20 DUP (040h, 020h, 04h, 02h) ; 80-byte buffer
                                              ;   with bit masks
three_d DWORD   5 DUP (5 DUP (5 DUP (0)))     ; 125 doublewords
                                              ;   initialized to 0

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ORG 510    ; Make the file 512 bytes long

[david]

thank you, I know .

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org 32767                   ; 32 * 1024 - 1
db 0

The exe file is 0.5K more than bin file.

But i find a problem.
It is impossible to create file which size is 64K.

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.model tiny
.code
.386
start:
    xor ax, ax

    org 65535                        ; 64 * 1024 -1
    db 0

end start

if the file name is test.asm

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masm test.asm
link test.obj
exe2bin test.exe test.bin

the compile message is :

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F:\EzNet>masm test.asm
Microsoft (R) MASM Compatibility Driver
Copyright (C) Microsoft Corp 1993.  All rights reserved.

 Invoking: ML.EXE /I. /Zm /c /Ta test.asm

Microsoft (R) Macro Assembler Version 6.11c
Copyright (C) Microsoft Corp 1981-1994.  All rights reserved.

 Assembling: test.asm

F:\EzNet>link test.obj

Microsoft (R) Segmented Executable Linker  Version 5.31.009 Jul 13 1992
Copyright (C) Microsoft Corp 1984-1992.  All rights reserved.

Run File [test.exe]:
List File [nul.map]:
Libraries [.lib]:
Definitions File [nul.def]:
test.obj(test.asm) : warning L4020: _TEXT : code-segment size exceeds 64K-36
LINK : warning L4021: no stack segment

F:\EzNet>exe2bin test.exe test.bin
Insufficient memory

The size of test.exe is 64.5K.
exe2bin can't change test.exe to test.bin.

I need the file's size is 64K.

so, I think it is impossilbe to create bin file which size is 64k using MASM.

who know other good idea.

I know it maybe done using NASM.

But i must using MASM in my company .

Thanks.

[Combuster]

But i must using MASM in my company.

For what company are you working that enforces this assembler, and assembly in general. Especially with this kind of dated software.

If there's a good reason for using these tools, then you should be able to ask your fellow colleagues during a coffee break how they would solve such a problem.

[JamesM]

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#include <stdio.h>

#define FILE_SIZE 64*1024   // 64KB

int main (char argc, char **argv)
{
  FILE *in = fopen(argv[1], "rb");
  FILE *out = fopen(argv[2], "wb");

  if (!in || !out)
  {
    fprintf(stderr, "File open error!\n");
    exit(1);
  }

  unsigned long i;
  char buffer;
  for (i = 0; i < FILE_SIZE; i++)
  {
    if (!fread(&buffer, 1, 1, in))
      buffer = '\0';
    fwrite(&buffer, 1, 1, out);
  }  

  exit(0);
}

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$ gcc -o test test.c
test.c: In function ‘main’:
test.c:18: warning: incompatible implicit declaration of built-in function ‘exit’
test.c:38: warning: incompatible implicit declaration of built-in function ‘exit’

$ echo "Howay the lads" >test.in

$ ./test test.in test.out

$ cat test.out
Howay the lads

$ ls -l test.out
-rw-r--r-- 1 james james 65536 2008-05-05 10:48 test.out

[AJ]

[quote]
org 65535 ; 64 * 1024 -1
db 0
[quote]

Wouldn't this place a zeroed byte after the 64k file? That would make the on-disk size 64.5k, whereas:

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   org 65534
   db 0

Should create a 64k file (disclaimer: I don't know MASM).

Cheers,
Adam

[bewing]

I think JamesM is right. Don't pad the binary object -- pad the executable file. Just append a bunch of junk to the end of a compiled executable until it is exactly 64K.

[Dex]

What does this assemble too ?

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.model tiny
.code
.386
start:
    xor ax, ax
    org 1024
    org 64511                        
    db 0

If it will allow it.

[david]

What does this assemble too ?

Code: Select all

.model tiny
.code
.386
start:
    xor ax, ax
    org 1024
    org 64511                        
    db 0

If it will allow it.

org 64511
db 0
The byte's offset is 64511, not (64511 + 1024).

[david]

to JamesM

I have made a tool to extend a file to 64K if the file's size is not 64K.
But I don't want to use it after I make the binary file everytime.

I want to make the binary file like this:
1 program
2 compile
3 link
then, the binary file's size is 64K.

Perhaps I am lazy,

Thanks!