Thread: Help to change a file extension

This is my code:

Code:

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

int parse (char **buf, const char *src, const char *ext)
{
	const char *cpy = src; /* make a copy */
	int len = 0; /* total size of buf */
	int pos = 0; /* grab the last dot found */
	int index = 0; /* current iterator character */
	int stop = 1; /* stop the loop */
	while (*cpy)
	{
		/* find the last dot in the string */
		if (*cpy == '.')
		{
			pos = index; /* save the position */
		}
		cpy++; /* next char */
		index++; /* len of the string */
	}
	len = pos; /* save the position of the last dot in the string */
	index = 0;/* reset the counter */
	for (;*src || !stop;pos++,src++)
	{
		/* now locate the position of the dot to ... */
		if (pos == index)
		{
			/* copy the new file extension */
			while (*ext)
			{
				**buf = *ext;
				ext++;
				*buf++;
				len++;
			}
			**buf++ = '\0'; /* add null terminated char */
			stop = 0; /* since we done, stop the loop */
		}
		**buf = *src; /* copying ... */
		*buf++;
	}
	return len; /* return len of bufy */
}

int main (int argc, char *argv[])
{
	char *bufy = (char *) malloc (256);
	int ret = parse (&bufy, "/home/joel/foo.flv", "mp3");
	printf ("New path: %s\n", bufy);
	free (bufy);
	return 0;
}

"bufy", should return something like: /home/joel/foo.mp3, but instead it crashes
Any ideas?

Holy crap... I generally just use...

Code:

char *x;

x = strrchr(string,'.');
strcpy(x,extension);

Yes, I know...but I'm trying to do it for myself
plus, learn about to use "&buffy"

Originally Posted by Joelito

Yes, I know...but I'm trying to do it for myself
plus, learn about to use "&buffy"

Then I suggest you learn to think in smaller blobs.... Write a simple function to find the dot and return a pointer. Write a second function to copy the extension to the pointer from the first function. Functions are pest kept to single purposes... one calculation, one operation, etc. Where you get into trouble is when you try to write one function that does 3245 different things all at once...

For example, your find last dot function could look something like this...

Code:

char * FindLastDot(char* str)
  { char *ptr = str;
     char *dot = NULL;

     while(*ptr++)
       { if (*ptr == '.')
            dot = ptr; }
 
    return dot; }

Smaller blobs make for easier coding and much easier debugging.