usage of strstr();

[Lincon Xue]

I want to handle a file in memory. This file is about 1.2M bytes. So I read the whole file in the memory . There is a special string in the file. When I use strstr() this special string , the debugger returns null . I want to know how long a tring the strstr() can to search.
the simple code is here:

#define specialstr "anystring"
#define _1M 1024*1024
char filedata[2*_1M];

void main(void,void)
{
FILE * fp;
char * spstrpos;
fp=fopen("path:file","rb");
fread(filedata,2*_1M,1,fp);
spstrpos=strstr(filedata,specialstr);

}

Any problem in it?
Thanks in advance!

[Ed Mulroy [TeamB]]

While the array really should be allocated at runtime with malloc or if
using C++ with new, I copied what you showed and filled in the missing
parts. There was no problem finding the string in the file.

----------------------------------
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define _1M 1024*1024
#define INSERT_POS (_1M + 32768)

char filedata[2*_1M];
const char filename[] = "bigtemp.tmp";
const char specialstr[] = "anystring";

int main()
{
FILE *fp;
char *spstrpos;
int i;

printf("Creating file ...");
fp = fopen(filename, "wb");

if (!fp)
{
printf("Could not open file\n");
return 0;
}

for (i = 0; i < (_1M + _1M); ++i)
{
if (i == INSERT_POS)
{
printf("\nInserting string at position %d ...", INSERT_POS);
fputs(specialstr, fp);
}
else
{
fputc((rand() % 27) + 'A', fp);
}
}

printf("\n");
fclose(fp);
fp = fopen(filename, "rb");

if (!fp)
{
printf("Could not open file\n");
return 0;
}

printf("\nReading file ...");
fread(filedata, sizeof(filedata), 1, fp);
spstrpos = strstr(filedata, specialstr);

if (!spstrpos)
{
printf("\nString not found\n");
}
else
{
printf("\nString found at position %d\n", (spstrpos - filedata));
}

fclose(fp);
return 0;
}

----------------------------------

. Ed

> Lincon Xue wrote in message
> news:3fc6ae6e$1...@newsgroups.borland.com...

[JD]

"Lincon Xue" <xueyon...@zcom.unimis.com> wrote:
> [...] There is a special string in the file.

You should note that strstr() will not search past NULL
characters so if the file does has NULL characters you'll run
into a problem. Additionally, you should ensure that the file
in memory is NULL terminated to prevent a potential infinate
loop.

~ JD

[Frank Birbacher]

Hi!

Lincon Xue wrote:
> #define specialstr "anystring"
> #define _1M 1024*1024
> char filedata[2*_1M];

You should not use "_1M". Everything beginning with an underscore "_" is
reserved for C++. However a trailing underscore is ok, like "MB_".

#define MBYTE 1024*1024

Frank