Issue #4554, Wrong file length with PLAIN representations in FSFS

r1654932 introduced into svn_fs_fs__file_length():

  if data_rep->expanded_size is 0:
    /* ... A plain representation may specify its EXPANDED LENGTH as "0"
         in which case, the SIZE value is what we want.

         Because EXPANDED_LENGTH will also be 0 for empty files, while
         SIZE is non-null, we need to check wether the content is
         actually empty. ... */
      if data_rep->md5 == empty_md5:
          *length = data_rep->size
      else:
          *length = 0

But how could SIZE be non-zero for an empty file? (If we were allowed
to store the rep as a delta from <non-empty> to <empty>, that would
have SIZE != 0, but a delta rep is not allowed when the (true)
expanded size is zero, according to the 'structure' document.)

This code is only in svn_fs_fs__file_length(). It seems to me that
other places where the ->expanded_size field is used, such as
svn_fs_fs__file_text_rep_equal(), are also affected by the problem.
This would falsely return "they're equal" if one or both reps have
->expanded_size==0 for a non-empty file.

- Julian
Received on 2015-04-13 18:10:04 CEST