When `php_zlib_deflate_filter()` is called with `PSFS_FLAG_FLUSH_INC`
but without new buckets being available (e.g. because a user calls
`rewind()` after writing to the stream), we have to make sure that any
pending data are flushed. This could basically be done like in the
attached patch[1], but that could cause unnessary flushes, which can be
harmful for compression, and adds unnecessary flush markers to the
stream. Thus, we use the `php_zlib_filter_data.finished` field, which
has not been used for `zlib.deflate` filters, and properly keep track
of the need to flush.
[1] <https://bugs.php.net/patch-display.php?bug_id=48725&patch=zlib-filter-flush-fix.patch&revision=latest>
Closes GH-6019.
Reading from a stream may return greater than zero, but nonetheless the
stream's EOF flag may have been set. We have to cater to this
condition by setting the close flag for filters.
We also have to cater to that change in the zlib.inflate filter:
If `inflate()` is called with flush mode `Z_FINISH`, but the output
buffer is not large enough to inflate all available data, it fails with
`Z_BUF_ERROR`. However, `Z_BUF_ERROR` is not fatal; in fact, the zlib
manual states: "If deflate returns with Z_OK or Z_BUF_ERROR, this
function must be called again with Z_FINISH and more output space
(updated avail_out) but no more input data, until it returns with
Z_STREAM_END or an error." Hence, we do so.
Closes GH-6001.
The php_stream_read() and php_stream_write() functions now return
an ssize_t value, with negative results indicating failure. Functions
like fread() and fwrite() will return false in that case.
As a special case, EWOULDBLOCK and EAGAIN on non-blocking streams
should not be regarded as error conditions, and be reported as
successful zero-length reads/writes instead. The handling of EINTR
remains unclear and is internally inconsistent (e.g. some code-paths
will automatically retry on EINTR, while some won't).
I'm landing this now to make sure the stream wrapper ops API changes
make it into 7.4 -- however, if the user-facing changes turn out to
be problematic we have the option of clamping negative returns to
zero in php_stream_read() and php_stream_write() to restore the
old behavior in a relatively non-intrusive manner.
Christoph M. Becker