MONGO_EXPORT bson_type bson_iterator_next( bson_iterator *i ) {
    int ds;

    if ( i->first ) {
        i->first = 0;
        return ( bson_type )( *i->cur );
    }

    switch ( bson_iterator_type( i ) ) {
    case BSON_EOO:
        return BSON_EOO; /* don't advance */
    case BSON_UNDEFINED:
    case BSON_NULL:
        ds = 0;
        break;
    case BSON_BOOL:
        ds = 1;
        break;
    case BSON_INT:
        ds = 4;
        break;
    case BSON_LONG:
    case BSON_DOUBLE:
    case BSON_TIMESTAMP:
    case BSON_DATE:
        ds = 8;
        break;
    case BSON_OID:
        ds = 12;
        break;
    case BSON_STRING:
    case BSON_SYMBOL:
    case BSON_CODE:
        ds = 4 + bson_iterator_int_raw( i );
        break;
    case BSON_BINDATA:
        ds = 5 + bson_iterator_int_raw( i );
        break;
    case BSON_OBJECT:
    case BSON_ARRAY:
    case BSON_CODEWSCOPE:
        ds = bson_iterator_int_raw( i );
        break;
    case BSON_DBREF:
        ds = 4+12 + bson_iterator_int_raw( i );
        break;
    case BSON_REGEX: {
        const char *s = bson_iterator_value( i );
        const char *p = s;
        p += strlen( p )+1;
        p += strlen( p )+1;
        ds = p-s;
        break;
    }

    default: {
        char msg[] = "unknown type: 000000000000";
        bson_numstr( msg+14, ( unsigned )( i->cur[0] ) );
        bson_fatal_msg( 0, msg );
        return 0;
    }
    }

    i->cur += 1 + strlen( i->cur + 1 ) + 1 + ds;

    return ( bson_type )( *i->cur );
}
The software performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control.