Basic help with strings

[nime]

Hello gurus,

I still have problems with C learning so please if somebody want to fix my concrete problem:

// here I search for string under bigger string

         char* found = strstr(bigString, searchPart);
         if (found)
             {
             
             char* leftpart = ?
             char* midpart = ?
             char* rightpart = ?

             gchar* markup;
             markup = g_markup_printf_escaped("%s<b>%s</b>%s", leftpart, midpart, rightpart);

             etc...

I dont know to get 'leftpart', 'midpart' and 'rightpart' based on 'found' which I need for fill into gtktreeview with markup.

So, please help.
I prefer ready, clean and fast solution
Thank you, nime.

[tabstop]

Where does found point? Can you use that as one of your three?

Where does right begin? At the end of your found string? Then you'll have to advance from the beginning to the end (by the length of the substring).

I would bet left begins at the beginning of the original string.

[nime]

Well tabstop,
If I understand well strstr should return place where finded string begins.
So, left part should be from 1 to found.
Mid part from found to found + strlen(searchPart)
And right part from found + strlen(searchPart) + 1 to strlen(bigString)

In visial basic I can write this in 5 seconds, but in C I can't.
So I ask someone to do this for me.

[tabstop]

Well tabstop,
If I understand well strstr should return place where finded string begins.
So, left part should be from 1 to found.
Mid part from found to found + strlen(searchPart)
And right part from found + strlen(searchPart) + 1 to strlen(bigString)

In visial basic I can write this in 5 seconds, but in C I can't.
So I ask someone to do this for me.

I don't know why you say you can't in C, because you just did. (Once you realize that in C your char pointers point to the start of the string.)

EDIT: Now, if you need them to be honest C-strings, with a \0 at the end, then you will need to acquire more memory to put these in, you can't do them in place, because the \0 will overwrite part of your strings.

[anduril462]

So if I understand you correctly, say your string was "abcdefg", and your search string was "de". That means you want leftpart to be "abc", midpart to be "de" and rightpart to be "fg"? If so, you can do so with

leftpart = bigString;  // point to the first char of bigString (index 0)
midpart = found;  // of course, the mid part is where i found searchPart
rightpart = found + strlen(searchPart) + 1;  // point to the first char after found, there will be a null terminator at the end of bigString to stop me

That should make them each point to the respective parts of bigString. Now, to get this printed into your markup string correctly. Then, look into using "%.*s" modifier. The . means you're giving a maximum width, and the * means that you insert an extra parameter that specifies how many characters you want to print, max. The man page for printf will give you more details. You can find the length of a part by subtracting the pointers, like midpart-leftpart.

[nime]

anduril,
thanks for help but this is not exactly what I need.

Shown part of program is inside for loop and 'found' changes often same as length of my parts.
I tested my markup string "by hand" and this part works OK.
I also don't understand pointers well so...
Here would be the best if someone write asked code for me.
This is only detail which remains to make my test program with gtktreeview - finished.

[anduril462]

anduril,
thanks for help but this is not exactly what I need.

You're welcome. I know it's not a "drop in place" solution, but it should give you some ideas as to how to make your program work.

Shown part of program is inside for loop and 'found' changes often same as length of my parts.

So each time through the loop, you will have a different bigString, searchPart and found. Each time you will also calculate a new leftpart, midpart and rightpart, so this shouldn't be a problem.

I tested my markup string "by hand" and this part works OK.

That's great. We know it's the logic of determining left, mid and right that you need help with, and help you we did.

I also don't understand pointers well so...

So what? Go learn them. It will be good for you. We have a tutorial on this very site, here. Google will turn up tons more. Go get your learn on.

Here would be the best if someone write asked code for me.

No, it would not be best, because next time you have a pointer problem, you will just have to ask somebody else to write code for you again. Best would be you learning how to program C and how to use pointers. Then you can write it yourself, and we can help with the little bumps in the road.

This is only detail which remains to make my test program with gtktreeview - finished.

Well, guess you better get going, so you can finish your program.

[ssharish2005]

Why dont you shown an example on what is the right, left, and the mid part your thinking in your mind. With an example string, for which we could propose a solution?

ssharish

[nime]

ssharish2005

I didn't show more code because it is complex and I make one minimal example for try to get what I need what was not good idea.
Strings are readen from structures in binary file and here could be few thousand of strings.
Strings on disk are written with dos codepage to 256 chars and then converted with iconv to UTF8 to be suitable for showing with gtk+ and much, much more.

Anyway,
Thanks for all which try to help.
Regards, nime.

[quzah]

So are you just trying to point to those spots in a string, or are you actually trying to copy them to their own buffers? If the former:

char *l = wholestring;
char *m = strstr( wholestring, "findthis" );
char *r = m ? m + strlen( findthis );

If the latter, do almost the same thing, except start copying blocks to their individual buffers.

Give it a try. Don't worry about doing it in a loop first. Just try to get what you want working with a single string that you pass it. Then worry about putting it into a bigger program.


Quzah.

[AndrewHunter]

A very basic program to give an example to demonstrate what has been talked about:

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

int main(void){

	char *myString = "LeftMiddleRight";
	char *searchString = "Middle";
	char *mySearch, Left, Right, Middle;

	mySearch = strstr(myString, searchString);
	if(mySearch){
		Left = myString[0];
		Middle = *mySearch;
		Right = *(mySearch + strlen(searchString));
		printf("%c %c %c", Left, Middle, Right);
		printf("\n%s\n%s\n%s\n", myString, mySearch,(mySearch + strlen(searchString))); 
	}
	
	_getch();
	return 0;
}

[quzah]

A very basic program to give an example to demonstrate what has been talked about:

#include <stdio.h>
#include <conio.h>
...
	_getch();
	return 0;
}

Seems silly to include a separate header just for one function, when similar functionality exists in stdio.h.


Quzah.

[AndrewHunter]

Seems silly to include a separate header just for one function, when similar functionality exists in stdio.h.
Quzah.

Quite a good point, thanks Quzah. That's what I get for just leaving a bare framework in place for these cboard posts.

[nime]

Andrew,
I can't get to work your example.
And I found why I can't solve this problem.

char* found = strstr("abcdefg", "de"); gives a pointer and I need integer.
In this case my integer should be 4.

I try to cast (int)found but without results (I get some address).
Now is question, how can I get 4 from found in this example?

[AndrewHunter]

You actually want 3 since arrays begin indexing at 0. C style strings are char arrays. So in your example char myString[]="abcdefg"; produces an array with 7 elements which are indexed 0 - 6. So for the position of d it would be myString[3]. An example of this is:

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

int main(void){

	char myString [] = "abcdefg";
	char *searchString = "de";
	char *mySearch;
	int arrayOffset;

	mySearch = strstr(myString, searchString);
	if(mySearch){
		arrayOffset = (mySearch - myString);
		printf("%d %c", arrayOffset,myString[arrayOffset]);
	}
	
	_getch();
	return 0;
}