[PATCH 1 of 4] obsolete: gather all contents related to format version 0 in a single place

[Augie Fackler]

On Tue, Sep 16, 2014 at 07:28:31PM -0700, Pierre-Yves David wrote:
> # HG changeset patch
> # User Pierre-Yves David <pierre-yves.david at fb.com>
> # Date 1410525703 -7200
> #      Fri Sep 12 14:41:43 2014 +0200
> # Node ID d5f9d5cb72e220cc89661dbe08afd9b13436c1df
> # Parent  48791c2bea1ceda4e4f28bc11651e281d636ce1a
> obsolete: gather all contents related to format version 0 in a single place
>
> All contents embrances documentation, constants and functions. The diff is confusing

Should "embrances" have been "enhances"? I'm not quite sure what word you meant.

> because it cannot understand what code is semantically moved around in this
> grand migration.

I assume "no functionality change, just code movement" is true?

This might be a case where a class-as-namespace would make some amount
of sense, as much as I hate myself for the proposal.

>
> diff --git a/mercurial/obsolete.py b/mercurial/obsolete.py
> --- a/mercurial/obsolete.py
> +++ b/mercurial/obsolete.py
> @@ -61,29 +61,12 @@ Markers are stored in an append-only fil
>
>  The file starts with a version header:
>
>  - 1 unsigned byte: version number, starting at zero.
>
> -
> -The header is followed by the markers. Each marker is made of:
> -
> -- 1 unsigned byte: number of new changesets "N", can be zero.
> -
> -- 1 unsigned 32-bits integer: metadata size "M" in bytes.
> -
> -- 1 byte: a bit field. It is reserved for flags used in common
> -  obsolete marker operations, to avoid repeated decoding of metadata
> -  entries.
> -
> -- 20 bytes: obsoleted changeset identifier.
> -
> -- N*20 bytes: new changesets identifiers.
> -
> -- M bytes: metadata as a sequence of nul-terminated strings. Each
> -  string contains a key and a value, separated by a colon ':', without
> -  additional encoding. Keys cannot contain '\0' or ':' and values
> -  cannot contain '\0'.
> +The header is followed by the markers. Marker format depend of the version. See
> +comment associated with each format for details.
>
>  """
>  import struct
>  import util, base85, node
>  import phases
> @@ -96,17 +79,10 @@ from i18n import _
>
>  # the obsolete feature is not mature enough to be enabled by default.
>  # you have to rely on third party extension extension to enable this.
>  _enabled = False
>
> -# data used for parsing and writing
> -_fm0version = 0
> -_fm0fixed   = '>BIB20s'
> -_fm0node = '20s'
> -_fm0fsize = struct.calcsize(_fm0fixed)
> -_fm0fnodesize = struct.calcsize(_fm0node)
> -
>  ### obsolescence marker flag
>
>  ## bumpedfix flag
>  #
>  # When a changeset A' succeed to a changeset A which became public, we call A'
> @@ -135,28 +111,35 @@ from i18n import _
>  # This flag mean that the successors express the changes between the public and
>  # bumped version and fix the situation, breaking the transitivity of
>  # "bumped" here.
>  bumpedfix = 1
>
> -def _readmarkers(data):
> -    """Read and enumerate markers from raw data"""
> -    off = 0
> -    diskversion = _unpack('>B', data[off:off + 1])[0]
> -    off += 1
> -    if diskversion not in formats:
> -        raise util.Abort(_('parsing obsolete marker: unknown version %r')
> -                         % diskversion)
> -    return diskversion, formats[diskversion][0](data, off)
> -
> -def encodemarkers(markers, addheader=False, version=_fm0version):
> -    # Kept separate from flushmarkers(), it will be reused for
> -    # markers exchange.
> -    encodeone = formats[version][1]
> -    if addheader:
> -        yield _pack('>B', _fm0version)
> -    for marker in markers:
> -        yield encodeone(marker)
> +## Parsing and writing of version "0"
> +#
> +# The header is followed by the markers. Each marker is made of:
> +#
> +# - 1 unsigned byte: number of new changesets "N", can be zero.
> +#
> +# - 1 unsigned 32-bits integer: metadata size "M" in bytes.
> +#
> +# - 1 byte: a bit field. It is reserved for flags used in common
> +#   obsolete marker operations, to avoid repeated decoding of metadata
> +#   entries.
> +#
> +# - 20 bytes: obsoleted changeset identifier.
> +#
> +# - N*20 bytes: new changesets identifiers.
> +#
> +# - M bytes: metadata as a sequence of nul-terminated strings. Each
> +#   string contains a key and a value, separated by a colon ':', without
> +#   additional encoding. Keys cannot contain '\0' or ':' and values
> +#   cannot contain '\0'.
> +_fm0version = 0
> +_fm0fixed   = '>BIB20s'
> +_fm0node = '20s'
> +_fm0fsize = struct.calcsize(_fm0fixed)
> +_fm0fnodesize = struct.calcsize(_fm0node)
>
>  def _fm0readmarkers(data, off=0):
>      # Loop on markers
>      l = len(data)
>      while off + _fm0fsize <= l:
> @@ -227,10 +210,30 @@ def _fm0encodeonemarker(marker):
>
>  # mapping to read/write various marker formats
>  # <version> -> (decoder, encoder)
>  formats = {0: (_fm0readmarkers, _fm0encodeonemarker)}
>
> +def _readmarkers(data):
> +    """Read and enumerate markers from raw data"""
> +    off = 0
> +    diskversion = _unpack('>B', data[off:off + 1])[0]
> +    off += 1
> +    if diskversion not in formats:
> +        raise util.Abort(_('parsing obsolete marker: unknown version %r')
> +                         % diskversion)
> +    return diskversion, formats[diskversion][0](data, off)
> +
> +def encodemarkers(markers, addheader=False, version=_fm0version):
> +    # Kept separate from flushmarkers(), it will be reused for
> +    # markers exchange.
> +    encodeone = formats[version][1]
> +    if addheader:
> +        yield _pack('>B', _fm0version)
> +    for marker in markers:
> +        yield encodeone(marker)
> +
> +
>  def encodemeta(meta):
>      """Return encoded metadata string to string mapping.
>
>      Assume no ':' in key and no '\0' in both key and value."""
>      for key, value in meta.iteritems():
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