I'm using a couple of functions for filling a list of contacts.   This is done by passing a list of custom BD__c object records to another function (retrieveTopOneHundred) which, in short, uses the BD__c objects to retrieve a list of contacts.  Problem I'm trying to solve:  I want to keep fetching contacts using the retrieveTopOneHundred function until the contactsListB list reaches 100 contacts.  How can I rewrite the code below so that I can do this without having to write a bunch of nested "if(contactsListB.size() < 100)...find more contacts based on the next set of BD__c records"?  I was hoping to use a Do While loop or something simple, but I just couldn't arrive at anything that worked. Thanks in advance for your help!

CODE:
public String TopOneHundred()
{
    List < sObject > bd = StdSetControllerBD.getRecords();
    List < Contact > contactsListB = retrieveTopOneHundred(bd);
    if (contactsListB.size() < 100)
    {
        StdSetControllerBD.next(); //if we have less than 100 contact records then we will go get more by repeating the process, this time with the next set of bd records in the StdSetControllerBD
        List < BD__c > nextRoundOfBdRecords = new List < BD__c > ();
        for (sObject sob: StdSetControllerBD.getRecords())
        {
            BD__c sobd = (BD__c) sob;
            nextRoundOfBdRecords.Add(sobd);
        }
        contactsListB.addAll(retrieveTopOneHundred(nextRoundOfBdRecords));
        if (contactsListB.size() < 100)
        {
            StdSetControllerBD.next(); //if we have less than 100 contact records then we will go get more by repeating the process, this time with the next set of bd records in the StdSetControllerBD
            List < BD__c > thirdRoundOfBdRecords = new List < BD__c > ();
            for (sObject sob: StdSetControllerBD.getRecords())
            {
                BD__c sobdd = (BD__c) sob;
                thirdRoundOfBdRecords.Add(sobdd);
            }
            contactsListB.addAll(retrieveTopOneHundred(nextRoundOfBdRecords));
        }
    }

    String contactsJSON = JSON.serializePretty(contactsListB);
    return contactsJSON;​
}