- group with option changes, so the options change at this level. If this
- item is right at the start of the pattern, the options can be
- abstracted and made external in the pre-compile phase, and ignored in
- the compile phase. This can be helpful when matching -- for instance in
- caseless checking of required bytes.
-
- If the code pointer is not (cd->start_code + 1 + LINK_SIZE), we are
- definitely *not* at the start of the pattern because something has been
- compiled. In the pre-compile phase, however, the code pointer can have
- that value after the start, because it gets reset as code is discarded
- during the pre-compile. However, this can happen only at top level - if
- we are within parentheses, the starting BRA will still be present. At
- any parenthesis level, the length value can be used to test if anything
- has been compiled at that level. Thus, a test for both these conditions
- is necessary to ensure we correctly detect the start of the pattern in
- both phases.
-