searching 10 bytes of char *

[jimberger]

Hi,

I have a char * that can be of any size, lets say for example 100 bytes. I want to be able to seek to the first 10 bytes and compare that with the first 10 bytes of another char * and so on..so next i will move on 10 bytes and compare these 10 bytes with the corresponding char *.

Any ideas on how i can do this? my c knowledge is very limited.
thanks for your help
jim

 

[ArkM]

Use memcmp(buf1,buf2,count) from <cstring> (in C++) or <string.h> (in C) to compare bytes. It returns:
< 0 - buf1 count bytes less than buf2
0 - buf1 identical to buf2
> 0 - buf1 greater than buf2
Use buf1 += 10 to advance the pointer.
I don't know what else. I think it's enough info to program your case. Your functional specifications are slightly incomplete...

 

[iribach]

this is not really what you want, (feel free
to make changes) it print starting pos of fully
matching string a in string b.

#include <stdio.h>
#define MAX 256
#define MIN 32

int main()
{
    char bigstr[MAX];
    char findme[MIN];
    char *big, *find;
    
    strcpy(bigstr,"abc bcabcabcabcabcabc  abc");
    strcpy(findme,"abc");
   
    for(big = bigstr; *big;){

       for(find = findme; *big && *find != *big; ++big);

       for(; *find && *find == *big; ++find, ++big);

       if(*find) continue;

       printf("%s found at pos %d\n",findme, big-bigstr-find-findme);
    }
    exit(0);
}

 

[ArkM]

To search a zero-ended substring in a zero-ended string use strstr() library function:

char* psub = strstr(bigstr,findme);

It's a portable, compact and fast way to go...