[PATCH 2 of 8 V7] bookmarks: introduce binary encoding

Stanislau Hlebik stash at fb.com
Thu Nov 10 04:24:56 EST 2016


We can use 32 bytes, but only 20 bytes will be used.
What’s the point then?

On 11/9/16, 5:22 PM, "Augie Fackler" <raf at durin42.com> wrote:

    On Wed, Nov 02, 2016 at 07:06:44AM -0700, Stanislau Hlebik wrote:
    > # HG changeset patch
    > # User Stanislau Hlebik <stash at fb.com>
    > # Date 1478016027 25200
    > #      Tue Nov 01 09:00:27 2016 -0700
    > # Branch stable
    > # Node ID f3da841e3d47ccbb0be3892b521607c09fdeab13
    > # Parent  a56a624a8a42b93ec980d2c284756a38719dffe6
    > bookmarks: introduce binary encoding
    >
    > Bookmarks binary encoding will be used for `bookmarks` bundle2 part.
    > The format is: <4 bytes - bookmark size, big-endian><bookmark>
    >                <1 byte - 0 if node is empty 1 otherwise><20 bytes node>
    
    Enough other formats have 32 bytes of space for nodes (eg revlog) that
    I suspect we should do 32 bytes here too. Thoughts?
    
    > BookmarksEncodeError and BookmarksDecodeError maybe thrown if input is
    > incorrect.
    >
    > diff --git a/mercurial/bookmarks.py b/mercurial/bookmarks.py
    > --- a/mercurial/bookmarks.py
    > +++ b/mercurial/bookmarks.py
    > @@ -7,8 +7,10 @@
    >
    >  from __future__ import absolute_import
    >
    > +import StringIO
    >  import errno
    >  import os
    > +import struct
    >
    >  from .i18n import _
    >  from .node import (
    > @@ -23,6 +25,70 @@
    >      util,
    >  )
    >
    > +_NONEMPTYNODE = struct.pack('?', False)
    > +_EMPTYNODE = struct.pack('?', True)
    > +
    > +def _unpackbookmarksize(stream):
    > +    """Returns 0 if stream is empty.
    > +    """
    > +
    > +    expectedsize = struct.calcsize('>i')
    > +    encodedbookmarksize = stream.read(expectedsize)
    > +    if len(encodedbookmarksize) == 0:
    > +        return 0
    > +    if len(encodedbookmarksize) != expectedsize:
    > +        raise ValueError(
    > +            _('cannot decode bookmark size: '
    > +              'expected size: %d, actual size: %d') %
    > +            (expectedsize, len(encodedbookmarksize)))
    > +    return struct.unpack('>i', encodedbookmarksize)[0]
    > +
    > +def encodebookmarks(bookmarks):
    > +    """Encodes bookmark to node mapping to the byte string.
    > +
    > +    Format: <4 bytes - bookmark size><bookmark>
    > +            <1 byte - 0 if node is empty 1 otherwise><20 bytes node>
    > +    Node may be 20 byte binary string, 40 byte hex string or empty
    > +    """
    > +
    > +    for bookmark, node in bookmarks.iteritems():
    > +        yield struct.pack('>i', (len(bookmark)))
    > +        yield encoding.fromlocal(bookmark)
    > +        if node:
    > +            if len(node) != 20 and len(node) != 40:
    > +                raise ValueError(_('node must be 20 or bytes long'))
    > +            if len(node) == 40:
    > +                node = bin(node)
    > +            yield _NONEMPTYNODE
    > +            yield node
    > +        else:
    > +            yield _EMPTYNODE
    > +
    > +def decodebookmarks(buf):
    > +    """Decodes buffer into bookmark to node mapping.
    > +
    > +    Node is either 20 bytes or empty.
    > +    """
    > +
    > +    stream = StringIO.StringIO(buf)
    > +    bookmarks = {}
    > +    bookmarksize = _unpackbookmarksize(stream)
    > +    while bookmarksize:
    > +        bookmark = stream.read(bookmarksize)
    > +        if len(bookmark) != bookmarksize:
    > +            raise ValueError(
    > +                _('cannot decode bookmark: expected size: %d, '
    > +                'actual size: %d') % (bookmarksize, len(bookmark)))
    > +        bookmark = encoding.tolocal(bookmark)
    > +        packedemptynodeflag = stream.read(struct.calcsize('?'))
    > +        emptynode = struct.unpack('?', packedemptynodeflag)[0]
    > +        node = ''
    > +        if not emptynode:
    > +            node = stream.read(20)
    > +        bookmarks[bookmark] = node
    > +        bookmarksize = _unpackbookmarksize(stream)
    > +    return bookmarks
    > +
    >  def _getbkfile(repo):
    >      """Hook so that extensions that mess with the store can hook bm storage.
    >
    > _______________________________________________
    > Mercurial-devel mailing list
    > Mercurial-devel at mercurial-scm.org
    > https://urldefense.proofpoint.com/v2/url?u=https-3A__www.mercurial-2Dscm.org_mailman_listinfo_mercurial-2Ddevel&d=DQIBAg&c=5VD0RTtNlTh3ycd41b3MUw&r=1EQ58Dmb5uX1qHujcsT1Mg&m=XfOL5bchNzFkHn3jvJndGgHchtnR08c9-WuY56aaUhw&s=xzxL1iYhrBKwmRk52RxWVbj-I3f4dfTiKl4dd9tjkOQ&e= 
    



More information about the Mercurial-devel mailing list