Thread: need help understanding this function

Hi all I'm trying to figure out how this function works, pointers give me a hard time still especially a function with several pointers as parameters.

I understand the function takes a string and if it has a % or + it removes those, I don't understand the nibble part of the function is where I'm confused. Long story short guess I just wonder if anyone could comment it so I can understand what's happening.

Code:

/* Unencode a urlencoded string*/
/*----------------------------------------------------------------------------*/
static void unencode(char *dst,char *src,size_t len)
{	char c;
	while (c = *src++,len--)
	{	if (c == '+') c = ' ';
		else if (c == '%')
		{	c = *src++;
			c = (nibble(c) << 4) | nibble(*src++);
			len -= 2;
		}
		*dst++ = c;
	}
	*dst = '\0';
}