Support plan classes with negative host_summary_regex matching

[Rytiss]

Description of the Change
Currently host_summary_regex field in the plan class definition only allows to send work to hosts matching a certain spec. This change allows to specify a negative regex to send work to hosts NOT matching the specified regex.

Use case: send work only to hosts without Virtualbox.

Release Notes
Support plan classes with negative host_summary_regex matching.

[Rytiss]

Note: needs doc updates at https://boinc.berkeley.edu/trac/wiki/AppPlanSpec but I seem to have misplaced my password, and password reset also cannot find my account.

[bema-aei]

The current 'master' version of the plan_class_spec code differs a bit from what I sent David originally. In our (Einstein@Home) code I do the following to achieve negated regex (and better logging that may help with debugging):

• The originally parsed string is kept in a separate variable (usually tag_string, here host_summary_string). This also allows for more explicit logging.
• in parse(), if the string starts with an !, the regex (here host_summary_regex) is compiled without it, i.e. from &(host_summary_string[1]) or host_summary_string+1, i.e. skipping the !.
• in check(), the truth value of the regex match is compared to the first character of the string being !

As a result. if the regex begins with a !, it is negated, meaning not match.

Here's an example (cpu_model)

in PLAN_CLASS_SPEC:

  regex_t cpu_model_regex; /* a regexp to match the device name */
  char   cpu_model_string[256];

in parse() (this is the old parser, but you get the idea):

                if(xp.parse_str(tag, "cpu_model", pc.cpu_model_string, sizeof(pc.cpu_model_string))) {
                  char*c=pc.cpu_model_string;
                  if (*c == '!') {
                    c++;
                  }
                  if ( regcomp(&(pc.cpu_model_regex), c, REG_EXTENDED|REG_NOSUB) ) {
                    log_messages.printf(MSG_CRITICAL, "BAD REGEXP: %s\n", pc.cpu_model_string);
                    return ERR_XML_PARSE;
                  }
                  continue;
                }

in check()

  // CPU model (regexp match)                                                                                                                                                                                                                                                                                                                                            
  if((strlen(cpu_model_string) > 0) &&
     ((regexec(&(cpu_model_regex), sreq.host.p_model, 0, NULL, 0) == 0) == (*cpu_model_string == '!'))) {
    if (config.debug_version_select)
      log_messages.printf(MSG_NORMAL,
                          "[version] CPU model '%s' doesn't match '%s'\n",
                          sreq.host.p_model, cpu_model_string);
    return false;
  }

[davidpanderson]

I created a PR #4390 which allows negation of any of the regular expressions in a plan class spec (OS, CPU vendor, etc.)