Mercurial > hg
view mercurial/txnutil.py @ 39814:d059cb669632
wireprotov2: allow multiple fields to follow revision maps
The *data wire protocol commands emit a series of CBOR values.
Because revision/delta data may be large, their data is emitted
outside the map as a top-level bytestring value.
Before this commit, we'd emit a single optional bytestring
value after the revision descriptor map. This got the job done.
But it was limiting in that we could only send a single field.
And, it required the consumer to know that the presence of a
key in the map implied the existence of a following bytestring
value.
This commit changes the encoding strategy so top-level bytestring
values in the stream are explicitly denoted in a "fieldsfollowing"
key. This key contains an array defining what fields that follow
and the expected size of each field.
By defining things this way, we can easily send N bytestring
values without any ambiguity about their order. In addition,
clients only need to know how to parse ``fieldsfollowing`` to
know if extra values are present.
Because this breaks backwards compatibility, we've bumped the version
number of the wire protocol version 2 API endpoint.
Differential Revision: https://phab.mercurial-scm.org/D4620
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 20 Sep 2018 12:57:23 -0700 |
parents | 206532700213 |
children | 2372284d9457 |
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# txnutil.py - transaction related utilities # # Copyright FUJIWARA Katsunori <foozy@lares.dti.ne.jp> and others # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import import errno from . import ( encoding, ) def mayhavepending(root): '''return whether 'root' may have pending changes, which are visible to this process. ''' return root == encoding.environ.get('HG_PENDING') def trypending(root, vfs, filename, **kwargs): '''Open file to be read according to HG_PENDING environment variable This opens '.pending' of specified 'filename' only when HG_PENDING is equal to 'root'. This returns '(fp, is_pending_opened)' tuple. ''' if mayhavepending(root): try: return (vfs('%s.pending' % filename, **kwargs), True) except IOError as inst: if inst.errno != errno.ENOENT: raise return (vfs(filename, **kwargs), False)