/* note: addFields always adds _id even if not specified
returns n added not counting _id unless requested.
*/
int BSONObj::addFields(BSONObj& from, set<string>& fields) {
assert( isEmpty() && !isOwned() ); /* partial implementation for now... */
BSONObjBuilder b;
int N = fields.size();
int n = 0;
BSONObjIterator i(from);
bool gotId = false;
while ( i.more() ) {
BSONElement e = i.next();
const char *fname = e.fieldName();
if ( fields.count(fname) ) {
b.append(e);
++n;
gotId = gotId || strcmp(fname, "_id")==0;
if ( n == N && gotId )
break;
} else if ( strcmp(fname, "_id")==0 ) {
b.append(e);
gotId = true;
if ( n == N && gotId )
break;
}
}
if ( n ) {
int len;
init( b.decouple(len), true );
}
return n;
}
