Question

I’m writing a simple C++ class in which I would like cache picture thumbnails versions of images downloaded from the web. As such, I would like to use a hash function which takes in URL strings and outputs a unique string suitable as a filename.

Is there a simple way to do this without re-writing the function myself? I searched around for a simple library, but couldn’t find anything. Surely this is a common problem.

Answer 1

A simpler approach is to replace everything which is not a character or a number with an underscore.

EDIT: Here’s a naive implementation in C:

#include <cctype>  char *safe_url(const char *str) {     char *safe = strdup(str);     for (int i = 0; i < strlen(str); i++) {         if (isalpha(str[i]))             safe[i] = str[i];         else             safe[i] = '_';     } }