squeeze!

/*
 *  call-seq:
 *     str.squeeze!([other_str]*)   => str or nil
 *  
 *  Squeezes <i>str</i> in place, returning either <i>str</i>, or
 *  <code>nil</code> if no changes were made.
 */

static VALUE
rb_str_squeeze_bang(argc, argv, str)
    int argc;
    VALUE *argv;
    VALUE str;
{
    char squeez[256];
    char *s, *send, *t;
    int c, save, modify = 0;
    int init = 1;
    int i;

    if (argc == 0) {
        for (i=0; i<256; i++) {
            squeez[i] = 1;
        }
    }
    else {
        for (i=0; i<argc; i++) {
            VALUE s = argv[i];

            StringValue(s);
            tr_setup_table(s, squeez, init);
            init = 0;
        }
    }

    rb_str_modify(str);
    s = t = RSTRING(str)->ptr;
    if (!s || RSTRING(str)->len == 0) return Qnil;
    send = s + RSTRING(str)->len;
    save = -1;
    while (s < send) {
        c = *s++ & 0xff;
        if (c != save || !squeez[c]) {
            *t++ = save = c;
        }
    }
    *t = '\0';
    if (t - RSTRING(str)->ptr != RSTRING(str)->len) {
        RSTRING(str)->len = t - RSTRING(str)->ptr;
        modify = 1;
    }

    if (modify) return str;
    return Qnil;
}