Define a Rules Action for creating Registration Codes

You missed to increment

function regcode_rules_action_create($quantity, $size, $prefix, $format, $case, $maxuses, $begins, $expires, $term, $settings) {
  $code = new stdClass;
  $code->is_active = 1;
  $code->maxuses = $maxuses;
  $code->begins = $begins;
  $code->expires = $expires;

  for ($i = 0; $i < $quantity; $i++) {
    $code->code = $prefix . regcode_generate($size, $format, $case);
    regcode_save($code, array($term->tid => TRUE), REGCODE_MODE_REPLACE);
  }
}

value of i which results infinite loop of registration code being create.moreover you are not taking in consideration total length which results in increased length if we add prefix to it.

and as module is designed if no. of registration code is 1 only registration code produced should be the code with prefix character.....

sorry ,if something in wrong in English .hope things i wanted to convey are conveyed.

for which i made following modification...a newbie so code may not be optimised

function regcode_rules_action_create($quantity, $size, $prefix, $format, $case, $maxuses, $begins, $expires, $term, $settings) {
  $code = new stdClass;
  $code->is_active = 1;
  $code->maxuses = $maxuses;
  $code->begins = $begins;
  $code->expires = $expires;

  if ($quantity == "1")
  {$code->code = $prefix;
    regcode_save($code, array($term->tid => TRUE), REGCODE_MODE_REPLACE);
	}
	else{
  for ($i = 0; $i < $quantity; $i++) {
    $code->code = $prefix . regcode_generate($size, $format, $case);
    regcode_save($code, array($term->tid => TRUE), REGCODE_MODE_REPLACE);
  }}
}

Has anyone had a deadlock issue running this rule action?

Using the following rule which attempts to create a new reg code using a hidden field when a group is created. It works most the time, typically the error comes when the client tests it!

{ "rules_create_registration_codes_for_group_invitees" : {
    "LABEL" : "Create Registration Codes For Group Invitees",
    "PLUGIN" : "reaction rule",
    "OWNER" : "rules",
    "REQUIRES" : [ "rules", "regcode", "group" ],
    "ON" : { "group_insert" : [] },
    "IF" : [
      { "user_has_role" : {
          "account" : [ "site:current-user" ],
          "roles" : { "value" : { "4" : "4", "5" : "5" } },
          "operation" : "OR"
        }
      }
    ],
    "DO" : [
      { "regcode_rules_action_create" : {
          "quantity" : "1",
          "size" : "0",
          "prefix" : "[group:field-reg-code]",
          "format" : "alphanum",
          "case" : "1",
          "maxuses" : "100",
          "begins" : "now",
          "expires" : "+ 10 days",
          "term" : "5"
        }
      }
    ]
  }
}

New features need to be put into the current branch first, then backported to previous versions if there is community interest.