sshpeer: return framed file object when needed
Currently, wireproto.wirepeer has a default implementation of
_submitbatch() and sshv1peer has a very similar implementation.
The main difference is that sshv1peer is aware of the total amount
of bytes it can read whereas the default implementation reads the
stream until no more data is returned. The default implementation
works for HTTP, since there is a known end to HTTP responses (either
Content-Length or 0 sized chunk).
This commit teaches sshv1peer to use our just-introduced "cappedreader"
class for wrapping a file object to limit the number of bytes that
can be read. We do this by introducing an argument to specify whether
the response is framed. If set, we returned a cappedreader instance
instead of the raw pipe.
_call() always has framed responses. So we set this argument
unconditionally and then .read() the entirety of the result.
Strictly speaking, we don't need to use cappedreader in this case
and can inline frame decoding/read logic. But I like when things
are consistent. The overhead should be negligible.
_callstream() and _callcompressable() are special: whether framing
is used depends on the specific command. So, we define a set
of commands that have framed response. It currently only
contains "batch."
As a result of this change, the one-off implementation of
_submitbatch() in sshv1peer can be removed since it is now
safe to .read() the response's file object until end of stream.
cappedreader takes care of not overrunning the frame.
Differential Revision: https://phab.mercurial-scm.org/D2380
sshpeer: move logic for sending a request into a new function
The **args being used to pass arbitrary command arguments is limiting
because it makes it harder to control behavior of the function.
We factor most of _callstream() into a new function that doesn't
use **args.
Differential Revision: https://phab.mercurial-scm.org/D2379
graphlog: document what "_" and "*" mean
Documenting "*" should've been a part of
9b3f95d9783d, but I somehow didn't
notice that the symbols are explained in the command's help text.
sshpeer: rename _recv and _send to _readframed and _writeframed
Because it is reading and writing a chunk of data with a well-defined
size. "recv" and "send" make it sound like things are a direct proxy to
the underlying pipe, which they aren't.
Differential Revision: https://phab.mercurial-scm.org/D2378
util: add a file object proxy that can read at most N bytes
Sometimes we have data of a known size within a stream. For
performance reasons, we don't want to pre-read this data (we want
to allow consumers to read on demand). For simplicitly reasons,
we don't want callers to necessarily know their data is coming
from within an outer stream and there is a limit to how much
they should read.
The class introduced by this commit provides a very simple proxy
around an underlying file object that allows the consumer to
.read() up to N bytes from the file object. Attempts to read
past this many bytes results in a simulated EOF.
Differential Revision: https://phab.mercurial-scm.org/D2377
patches: release the GIL while applying the patch
This will allow multiple threads to apply patches at the same time.