Merge r422731, r422736, r422739, r423940, r424759, r424950, r425109, r426790,

r426791, r426793, r426795, r416165, r426799, r475403, r475406, r475915,
r475920, r475922, r476600, r437668 from trunk, which makes mod_deflate.c the
same as r483597 from trunk:

All comments to these changes for the sake of completeness:

* Fix wrong FLUSH bucket handling in deflate_out_filter: Actually the internal
  structures of libz never got flushed as ctx->stream.avail_in is always zero
  here. As the EOS and the FLUSH bucket case use the same code for flushing
  libz's internal buffers move this code to the new function flush_zlib_buffer.

* Fix potential memory leaks in deflate_out_filter if bailing out due to an
  error (either in the lower filter chain or during a libz operation). We need
  to call deflateEnd as it is very likely that this filter is never called
  again to ensures that libz's internal structures get cleaned properly.

* Remove ourselves from the filter chain if we failed to init libz, as we
  pass data down the filter chain uncompressed afterwards.

* In preparation of the changes of the inflate out filter:
  - rename flush_zlib_buffer to flush_libz_buffer (this name seems
    better)
  - add a parameter to tell flush_libz_buffer whether it should
    deflate or inflate as this function should be also used for the
    inflate out filter.

* This shortcut is too short. It is not up to the filters to decide
  whether filters down the chain can do something useful with this empty
  brigade.

* Initialize zRC to avoid a compiler warning.

* Rather use a pool cleanup function than calling deflateEnd before every
  return from function to ensure that libz's internals get cleaned up.

* Add parameter crc to flush_libz_buffer in order to call the libz's crc32
  function on the output buffer if needed. This is actually needed by the
  later rework of the inflate out filter.

* Use a define for the number of validation bytes (CRC and length) after the
  compressed data

* We can ignore Z_BUF_ERROR in flush_libz_buffer because:
  When we call libz_func we can assume that

   - avail_in is zero (due to the surrounding code that calls
     flush_libz_buffer)
   - avail_out is non zero due to the fact that we just emptied
     the output buffer and stored it into a brigade

  So the only reason for Z_BUF_ERROR is that the internal libz
  buffers are now empty and thus we called libz_func one time
  too often. This does not hurt. It simply says that we are done.

* some optimizations taken from the inflate out filter

* Remove bogus code that chokes on flush buckets

* Rework inflate out filter and give it a similar workflow as the deflate out
  filter. This fixes the following bugs in the inflate out filter:

  - Incorrect handling of flush buckets.
  - Excessive memory usage for large compressed content (because we now
    already sent parts down the chain and do not process the whole brigade
    first before sending something down the chain).
  - Handle the case correctly where the validation bytes at the end of
    the compressed data stream are distributed across different buckets /
    brigades.
  - Fix a memory leak due to not cleaning up the internal structures of
    libz in some error cases.

* Ensure that we do not try to inflate validation data or garbage data. None
  of this is zlib's business.

* Ensure that we do not perform our final operations twice if a second EOS
  falls down the chain by accident. Otherwise we are likely to run in a
  SEGFAULT. So remove ourselves from the chain.

* Actually append new data to the validation buffer and do not overwrite old
  data already there by setting the correct offset for the target buffer.

* Also log the presence of garbage data at the end of the stream if all
  validation data is available in the first round.

* Housekeeping: keep track of size even in the edge-case where validation
  bytes trickle in over multiple buckets.


PR: 39854
Reviewed by: rpluem, niq, jerenkrantz, wrowe


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@488817 13f79535-47bb-0310-9956-ffa450edef68