int sprint_hex_data(char* out_buf, DATA_BLOCK& x) {
    unsigned int i;
    char buf[16];
    const char hex[] = "0123456789abcdef";
    char* p = out_buf;

    for (i=0; i<x.len; i++) {
        *p++ = hex[x.data[i]/16];
        *p++ = hex[x.data[i]%16];
        if (i%32==31) *p++ = '\n';
    }
    if (x.len%32 != 0) *p++ = '\n';
    strcpy(p, ".\n");

    return 0;
}