Removed the automatic window_size adjustments from
_libssh2_channel_read() and instead all channel readers must now make
sure to enlarge the window sizes properly themselves.
libssh2_channel_read_ex() - the public function, now grows the window
size according to the requested buffer size. Applications can still opt
to grow the window more on demand. Larger windows tend to give higher
performance.
sftp_read() now uses the read-ahead logic to figure out a window_size.
A returned READ packet that is short will now only reduce the
offset.
This is a temporary fix as it is slightly better than the previous
approach but still not very good.
When receiving more data than what the window size allows on a
particular channel, make sure that the window size is adjusted in that
case too. Previously it would only adjust the window in the non-error
case.
When seeking to a new position, flush the packetlist and buffered data
to prevent already received or pending data to wrongly get used when
sftp-reading from the new offset within the file.
In the case where a read packet has been received from the server, but
the entire contents couldn't be copied to the user-buffer, the data is
instead buffered and copied to the user's buffer in the next invocation
of sftp_read(). When that "extra" copy is made, the 'offset' pointer was
not advanced accordingly.
The biggest impact of this flaw was that the 'already' variable at the
top of the function that figures out how much data "ahead" that has
already been asked for would slowly go more and more out of sync, which
could lead to the file not being read all the way to the end.
This problem was most noticable in cases where the application would
only try to read the exact file size amount, like curl does. In the
examples libssh2 provides the sftp read function is most often called
with a fixed size large buffer and then the bug would not appear as
easily.
This bug was introduced in the SFTP rewrite in 1.2.8.
Bug: http://curl.haxx.se/mail/lib-2011-08/0305.htmlhttp://www.libssh2.org/mail/libssh2-devel-archive-2011-08/0085.shtml
