bundle2: introduce a `parthandler` decorator

Simple syntax sugar to register an handler for a new part type.

mercurial/bundle2.py

@@ -1,433 +1,448
 # bundle2.py - generic container format to transmit arbitrary data.
 #
 # Copyright 2013 Facebook, Inc.
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 """Handling of the new bundle2 format
 
 The goal of bundle2 is to act as an atomically packet to transmit a set of
 payloads in an application agnostic way. It consist in a sequence of "parts"
 that will be handed to and processed by the application layer.
 
 
 General format architecture
 ===========================
 
 The format is architectured as follow
 
  - magic string
  - stream level parameters
  - payload parts (any number)
  - end of stream marker.
 
 the Binary format
 ============================
 
 All numbers are unsigned and big endian.
 
 stream level parameters
 ------------------------
 
 Binary format is as follow
 
 :params size: (16 bits integer)
 
   The total number of Bytes used by the parameters
 
 :params value: arbitrary number of Bytes
 
   A blob of `params size` containing the serialized version of all stream level
   parameters.
 
   The blob contains a space separated list of parameters. parameter with value
   are stored in the form `<name>=<value>`. Both name and value are urlquoted.
 
   Empty name are obviously forbidden.
 
   Name MUST start with a letter. If this first letter is lower case, the
   parameter is advisory and can be safefly ignored. However when the first
   letter is capital, the parameter is mandatory and the bundling process MUST
   stop if he is not able to proceed it.
 
   Stream parameters use a simple textual format for two main reasons:
 
   - Stream level parameters should remains simple and we want to discourage any
     crazy usage.
   - Textual data allow easy human inspection of a the bundle2 header in case of
     troubles.
 
   Any Applicative level options MUST go into a bundle2 part instead.
 
 Payload part
 ------------------------
 
 Binary format is as follow
 
 :header size: (16 bits inter)
 
   The total number of Bytes used by the part headers. When the header is empty
   (size = 0) this is interpreted as the end of stream marker.
 
 :header:
 
     The header defines how to interpret the part. It contains two piece of
     data: the part type, and the part parameters.
 
     The part type is used to route an application level handler, that can
     interpret payload.
 
     Part parameters are passed to the application level handler.  They are
     meant to convey information that will help the application level object to
     interpret the part payload.
 
     The binary format of the header is has follow
 
     :typesize: (one byte)
 
     :typename: alphanumerical part name
 
     :parameters:
 
         Part's parameter may have arbitraty content, the binary structure is::
 
             <mandatory-count><advisory-count><param-sizes><param-data>
 
         :mandatory-count: 1 byte, number of mandatory parameters
 
         :advisory-count:  1 byte, number of advisory parameters
 
         :param-sizes:
 
             N couple of bytes, where N is the total number of parameters. Each
             couple contains (<size-of-key>, <size-of-value) for one parameter.
 
         :param-data:
 
             A blob of bytes from which each parameter key and value can be
             retrieved using the list of size couples stored in the previous
             field.
 
             Mandatory parameters comes first, then the advisory ones.
 
 :payload:
 
     payload is a series of `<chunksize><chunkdata>`.
 
     `chunksize` is a 32 bits integer, `chunkdata` are plain bytes (as much as
     `chunksize` says)` The payload part is concluded by a zero size chunk.
 
     The current implementation always produces either zero or one chunk.
     This is an implementation limitation that will ultimatly be lifted.
 """
 
 import util
 import struct
 import urllib
 import string
 
 import changegroup
 from i18n import _
 
 _pack = struct.pack
 _unpack = struct.unpack
 
 _magicstring = 'HG20'
 
 _fstreamparamsize = '>H'
 _fpartheadersize = '>H'
 _fparttypesize = '>B'
 _fpayloadsize = '>I'
 _fpartparamcount = '>BB'
 
 def _makefpartparamsizes(nbparams):
     """return a struct format to read part parameter sizes
 
     The number parameters is variable so we need to build that format
     dynamically.
     """
     return '>'+('BB'*nbparams)
 
+parthandlermapping = {}
 
-parthandlermapping = {}
+def parthandler(parttype):
+    """decorator that register a function as a bundle2 part handler
+
+    eg::
+
+        @parthandler('myparttype')
+        def myparttypehandler(...):
+            '''process a part of type "my part".'''
+            ...
+    """
+    def _decorator(func):
+        assert parttype not in parthandlermapping
+        parthandlermapping[parttype] = func
+        return func
+    return _decorator
 
 def processbundle(repo, stream):
     """This function process a bundle, apply effect to/from a repo
 
     Currently it:
     - parse a stream into an unbundle20 object
     - iterate over each parts then search and use the proper handling code to
       process the part.
 
     Parts are processes in order.
 
     This is very early version of this function that will be strongly reworked
     before final usage.
 
     All unknown parts are currently ignored (Mandatory parts logic will comes
     later).
     """
     ui = repo.ui
     # Extraction of the unbundler object will most likely change. It may be
     # done outside of this function, the unbundler would be passed as argument.
     # in all case the unbundler will eventually be created by a
     # `changegroup.readbundle` style function.
     unbundler = unbundle20(ui, stream)
     # todo:
     # - replace this is a init function soon.
     # - exception catching
     unbundler.params
     for part in unbundler:
         parttype = part.type
         # part key are matched lower case
         key = parttype.lower()
         try:
             handler = parthandlermapping[key]
             ui.debug('found an handler for part %r\n' % parttype)
         except KeyError:
             ui.debug('ignoring unknown advisory part %r\n' % key)
             # todo: consume the part (once we use streamed parts)
             continue
         handler(repo, part)
 
 class bundle20(object):
     """represent an outgoing bundle2 container
 
     Use the `addparam` method to add stream level parameter. and `addpart` to
     populate it. Then call `getchunks` to retrieve all the binary chunks of
     datathat compose the bundle2 container."""
 
     def __init__(self, ui):
         self.ui = ui
         self._params = []
         self._parts = []
 
     def addparam(self, name, value=None):
         """add a stream level parameter"""
         if not name:
             raise ValueError('empty parameter name')
         if name[0] not in string.letters:
             raise ValueError('non letter first character: %r' % name)
         self._params.append((name, value))
 
     def addpart(self, part):
         """add a new part to the bundle2 container
 
         Parts contains the actuall applicative payload."""
         self._parts.append(part)
 
     def getchunks(self):
         self.ui.debug('start emission of %s stream\n' % _magicstring)
         yield _magicstring
         param = self._paramchunk()
         self.ui.debug('bundle parameter: %s\n' % param)
         yield _pack(_fstreamparamsize, len(param))
         if param:
             yield param
 
         self.ui.debug('start of parts\n')
         for part in self._parts:
             self.ui.debug('bundle part: "%s"\n' % part.type)
             for chunk in part.getchunks():
                 yield chunk
         self.ui.debug('end of bundle\n')
         yield '\0\0'
 
     def _paramchunk(self):
         """return a encoded version of all stream parameters"""
         blocks = []
         for par, value in self._params:
             par = urllib.quote(par)
             if value is not None:
                 value = urllib.quote(value)
                 par = '%s=%s' % (par, value)
             blocks.append(par)
         return ' '.join(blocks)
 
 class unbundle20(object):
     """interpret a bundle2 stream
 
     (this will eventually yield parts)"""
 
     def __init__(self, ui, fp):
         self.ui = ui
         self._fp = fp
         header = self._readexact(4)
         magic, version = header[0:2], header[2:4]
         if magic != 'HG':
             raise util.Abort(_('not a Mercurial bundle'))
         if version != '20':
             raise util.Abort(_('unknown bundle version %s') % version)
         self.ui.debug('start processing of %s stream\n' % header)
 
     def _unpack(self, format):
         """unpack this struct format from the stream"""
         data = self._readexact(struct.calcsize(format))
         return _unpack(format, data)
 
     def _readexact(self, size):
         """read exactly <size> bytes from the stream"""
         return changegroup.readexactly(self._fp, size)
 
     @util.propertycache
     def params(self):
         """dictionnary of stream level parameters"""
         self.ui.debug('reading bundle2 stream parameters\n')
         params = {}
         paramssize = self._unpack(_fstreamparamsize)[0]
         if paramssize:
             for p in self._readexact(paramssize).split(' '):
                 p = p.split('=', 1)
                 p = [urllib.unquote(i) for i in p]
                 if len(p) < 2:
                     p.append(None)
                 self._processparam(*p)
                 params[p[0]] = p[1]
         return params
 
     def _processparam(self, name, value):
         """process a parameter, applying its effect if needed
 
         Parameter starting with a lower case letter are advisory and will be
         ignored when unknown.  Those starting with an upper case letter are
         mandatory and will this function will raise a KeyError when unknown.
 
         Note: no option are currently supported. Any input will be either
               ignored or failing.
         """
         if not name:
             raise ValueError('empty parameter name')
         if name[0] not in string.letters:
             raise ValueError('non letter first character: %r' % name)
         # Some logic will be later added here to try to process the option for
         # a dict of known parameter.
         if name[0].islower():
             self.ui.debug("ignoring unknown parameter %r\n" % name)
         else:
             raise KeyError(name)
 
 
     def __iter__(self):
         """yield all parts contained in the stream"""
         # make sure param have been loaded
         self.params
         self.ui.debug('start extraction of bundle2 parts\n')
         part = self._readpart()
         while part is not None:
             yield part
             part = self._readpart()
         self.ui.debug('end of bundle2 stream\n')
 
     def _readpart(self):
         """return None when an end of stream markers is reach"""
 
         headersize = self._unpack(_fpartheadersize)[0]
         self.ui.debug('part header size: %i\n' % headersize)
         if not headersize:
             return None
         headerblock = self._readexact(headersize)
         # some utility to help reading from the header block
         self._offset = 0 # layer violation to have something easy to understand
         def fromheader(size):
             """return the next <size> byte from the header"""
             offset = self._offset
             data = headerblock[offset:(offset + size)]
             self._offset = offset + size
             return data
         def unpackheader(format):
             """read given format from header
 
             This automatically compute the size of the format to read."""
             data = fromheader(struct.calcsize(format))
             return _unpack(format, data)
 
         typesize = unpackheader(_fparttypesize)[0]
         parttype = fromheader(typesize)
         self.ui.debug('part type: "%s"\n' % parttype)
         ## reading parameters
         # param count
         mancount, advcount = unpackheader(_fpartparamcount)
         self.ui.debug('part parameters: %i\n' % (mancount + advcount))
         # param size
         paramsizes = unpackheader(_makefpartparamsizes(mancount + advcount))
         # make it a list of couple again
         paramsizes = zip(paramsizes[::2], paramsizes[1::2])
         # split mandatory from advisory
         mansizes = paramsizes[:mancount]
         advsizes = paramsizes[mancount:]
         # retrive param value
         manparams = []
         for key, value in mansizes:
             manparams.append((fromheader(key), fromheader(value)))
         advparams = []
         for key, value in advsizes:
             advparams.append((fromheader(key), fromheader(value)))
         del self._offset # clean up layer, nobody saw anything.
         ## part payload
         payload = []
         payloadsize = self._unpack(_fpayloadsize)[0]
         self.ui.debug('payload chunk size: %i\n' % payloadsize)
         while payloadsize:
             payload.append(self._readexact(payloadsize))
             payloadsize = self._unpack(_fpayloadsize)[0]
             self.ui.debug('payload chunk size: %i\n' % payloadsize)
         payload = ''.join(payload)
         current = part(parttype, manparams, advparams, data=payload)
         return current
 
 
 class part(object):
     """A bundle2 part contains application level payload
 
     The part `type` is used to route the part to the application level
     handler.
     """
 
     def __init__(self, parttype, mandatoryparams=(), advisoryparams=(),
                  data=''):
         self.type = parttype
         self.data = data
         self.mandatoryparams = mandatoryparams
         self.advisoryparams = advisoryparams
 
     def getchunks(self):
         #### header
         ## parttype
         header = [_pack(_fparttypesize, len(self.type)),
                   self.type,
                  ]
         ## parameters
         # count
         manpar = self.mandatoryparams
         advpar = self.advisoryparams
         header.append(_pack(_fpartparamcount, len(manpar), len(advpar)))
         # size
         parsizes = []
         for key, value in manpar:
             parsizes.append(len(key))
             parsizes.append(len(value))
         for key, value in advpar:
             parsizes.append(len(key))
             parsizes.append(len(value))
         paramsizes = _pack(_makefpartparamsizes(len(parsizes) / 2), *parsizes)
         header.append(paramsizes)
         # key, value
         for key, value in manpar:
             header.append(key)
             header.append(value)
         for key, value in advpar:
             header.append(key)
             header.append(value)
         ## finalize header
         headerchunk = ''.join(header)
         yield _pack(_fpartheadersize, len(headerchunk))
         yield headerchunk
         ## payload
         # we only support fixed size data now.
         # This will be improved in the future.
         if len(self.data):
             yield _pack(_fpayloadsize, len(self.data))
             yield self.data
         # end of payload
         yield _pack(_fpayloadsize, 0)
 

tests/test-bundle2.t

@@ -1,380 +1,379
 
 Create an extension to test bundle2 API
 
   $ cat > bundle2.py << EOF
   > """A small extension to test bundle2 implementation
   > 
   > Current bundle2 implementation is far too limited to be used in any core
   > code. We still need to be able to test it while it grow up.
   > """
   > 
   > import sys
   > from mercurial import cmdutil
   > from mercurial import util
   > from mercurial import bundle2
   > cmdtable = {}
   > command = cmdutil.command(cmdtable)
   > 
   > ELEPHANTSSONG = """Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko
   > Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
   > Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko."""
   > assert len(ELEPHANTSSONG) == 178 # future test say 178 bytes, trust it.
   > 
+  > @bundle2.parthandler('test:song')
   > def songhandler(repo, part):
   >     """handle a "test:song" bundle2 part, printing the lyrics on stdin"""
   >     repo.ui.write('The choir start singing:\n')
   >     for line in part.data.split('\n'):
   >         repo.ui.write('    %s\n' % line)
   > 
-  > bundle2.parthandlermapping['test:song'] = songhandler
-  > 
   > @command('bundle2',
   >          [('', 'param', [], 'stream level parameter'),
   >           ('', 'parts', False, 'include some arbitrary parts to the bundle'),],
   >          '[OUTPUTFILE]')
   > def cmdbundle2(ui, repo, path=None, **opts):
   >     """write a bundle2 container on standard ouput"""
   >     bundler = bundle2.bundle20(ui)
   >     for p in opts['param']:
   >         p = p.split('=', 1)
   >         try:
   >             bundler.addparam(*p)
   >         except ValueError, exc:
   >             raise util.Abort('%s' % exc)
   > 
   >     if opts['parts']:
   >        part = bundle2.part('test:empty')
   >        bundler.addpart(part)
   >        # add a second one to make sure we handle multiple parts
   >        part = bundle2.part('test:empty')
   >        bundler.addpart(part)
   >        part = bundle2.part('test:song', data=ELEPHANTSSONG)
   >        bundler.addpart(part)
   >        part = bundle2.part('test:math',
   >                            [('pi', '3.14'), ('e', '2.72')],
   >                            [('cooking', 'raw')],
   >                            '42')
   >        bundler.addpart(part)
   > 
   >     if path is None:
   >        file = sys.stdout
   >     else:
   >         file = open(path, 'w')
   > 
   >     for chunk in bundler.getchunks():
   >         file.write(chunk)
   > 
   > @command('unbundle2', [], '')
   > def cmdunbundle2(ui, repo):
   >     """process a bundle2 stream from stdin on the current repo"""
   >     bundle2.processbundle(repo, sys.stdin)
   > 
   > @command('statbundle2', [], '')
   > def cmdstatbundle2(ui, repo):
   >     """print statistic on the bundle2 container read from stdin"""
   >     unbundler = bundle2.unbundle20(ui, sys.stdin)
   >     try:
   >         params = unbundler.params
   >     except KeyError, exc:
   >        raise util.Abort('unknown parameters: %s' % exc)
   >     ui.write('options count: %i\n' % len(params))
   >     for key in sorted(params):
   >         ui.write('- %s\n' % key)
   >         value = params[key]
   >         if value is not None:
   >             ui.write('    %s\n' % value)
   >     parts = list(unbundler)
   >     ui.write('parts count:   %i\n' % len(parts))
   >     for p in parts:
   >         ui.write('  :%s:\n' % p.type)
   >         ui.write('    mandatory: %i\n' % len(p.mandatoryparams))
   >         ui.write('    advisory: %i\n' % len(p.advisoryparams))
   >         ui.write('    payload: %i bytes\n' % len(p.data))
   > EOF
   $ cat >> $HGRCPATH << EOF
   > [extensions]
   > bundle2=$TESTTMP/bundle2.py
   > EOF
 
 The extension requires a repo (currently unused)
 
   $ hg init main
   $ cd main
   $ touch a
   $ hg add a
   $ hg commit -m 'a'
 
 
 Empty bundle
 =================
 
 - no option
 - no parts
 
 Test bundling
 
   $ hg bundle2
   HG20\x00\x00\x00\x00 (no-eol) (esc)
 
 Test unbundling
 
   $ hg bundle2 | hg statbundle2
   options count: 0
   parts count:   0
 
 Test old style bundle are detected and refused
 
   $ hg bundle --all ../bundle.hg
   1 changesets found
   $ hg statbundle2 < ../bundle.hg
   abort: unknown bundle version 10
   [255]
 
 Test parameters
 =================
 
 - some options
 - no parts
 
 advisory parameters, no value
 -------------------------------
 
 Simplest possible parameters form
 
 Test generation simple option
 
   $ hg bundle2 --param 'caution'
   HG20\x00\x07caution\x00\x00 (no-eol) (esc)
 
 Test unbundling
 
   $ hg bundle2 --param 'caution' | hg statbundle2
   options count: 1
   - caution
   parts count:   0
 
 Test generation multiple option
 
   $ hg bundle2 --param 'caution' --param 'meal'
   HG20\x00\x0ccaution meal\x00\x00 (no-eol) (esc)
 
 Test unbundling
 
   $ hg bundle2 --param 'caution' --param 'meal' | hg statbundle2
   options count: 2
   - caution
   - meal
   parts count:   0
 
 advisory parameters, with value
 -------------------------------
 
 Test generation
 
   $ hg bundle2 --param 'caution' --param 'meal=vegan' --param 'elephants'
   HG20\x00\x1ccaution meal=vegan elephants\x00\x00 (no-eol) (esc)
 
 Test unbundling
 
   $ hg bundle2 --param 'caution' --param 'meal=vegan' --param 'elephants' | hg statbundle2
   options count: 3
   - caution
   - elephants
   - meal
       vegan
   parts count:   0
 
 parameter with special char in value
 ---------------------------------------------------
 
 Test generation
 
   $ hg bundle2 --param 'e|! 7/=babar%#==tutu' --param simple
   HG20\x00)e%7C%21%207/=babar%25%23%3D%3Dtutu simple\x00\x00 (no-eol) (esc)
 
 Test unbundling
 
   $ hg bundle2 --param 'e|! 7/=babar%#==tutu' --param simple | hg statbundle2
   options count: 2
   - e|! 7/
       babar%#==tutu
   - simple
   parts count:   0
 
 Test unknown mandatory option
 ---------------------------------------------------
 
   $ hg bundle2 --param 'Gravity' | hg statbundle2
   abort: unknown parameters: 'Gravity'
   [255]
 
 Test debug output
 ---------------------------------------------------
 
 bundling debug
 
   $ hg bundle2 --debug --param 'e|! 7/=babar%#==tutu' --param simple ../out.hg2
   start emission of HG20 stream
   bundle parameter: e%7C%21%207/=babar%25%23%3D%3Dtutu simple
   start of parts
   end of bundle
 
 file content is ok
 
   $ cat ../out.hg2
   HG20\x00)e%7C%21%207/=babar%25%23%3D%3Dtutu simple\x00\x00 (no-eol) (esc)
 
 unbundling debug
 
   $ hg statbundle2 --debug < ../out.hg2
   start processing of HG20 stream
   reading bundle2 stream parameters
   ignoring unknown parameter 'e|! 7/'
   ignoring unknown parameter 'simple'
   options count: 2
   - e|! 7/
       babar%#==tutu
   - simple
   start extraction of bundle2 parts
   part header size: 0
   end of bundle2 stream
   parts count:   0
 
 
 Test buggy input
 ---------------------------------------------------
 
 empty parameter name
 
   $ hg bundle2 --param '' --quiet
   abort: empty parameter name
   [255]
 
 bad parameter name
 
   $ hg bundle2 --param 42babar
   abort: non letter first character: '42babar'
   [255]
 
 
 Test part
 =================
 
   $ hg bundle2 --parts ../parts.hg2 --debug
   start emission of HG20 stream
   bundle parameter: 
   start of parts
   bundle part: "test:empty"
   bundle part: "test:empty"
   bundle part: "test:song"
   bundle part: "test:math"
   end of bundle
 
   $ cat ../parts.hg2
   HG20\x00\x00\x00\r (esc)
   test:empty\x00\x00\x00\x00\x00\x00\x00\r (esc)
   test:empty\x00\x00\x00\x00\x00\x00\x00\x0c	test:song\x00\x00\x00\x00\x00\xb2Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko (esc)
   Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
   Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.\x00\x00\x00\x00\x00'	test:math\x02\x01\x02\x04\x01\x04\x07\x03pi3.14e2.72cookingraw\x00\x00\x00\x0242\x00\x00\x00\x00\x00\x00 (no-eol) (esc)
 
 
   $ hg statbundle2 < ../parts.hg2
   options count: 0
   parts count:   4
     :test:empty:
       mandatory: 0
       advisory: 0
       payload: 0 bytes
     :test:empty:
       mandatory: 0
       advisory: 0
       payload: 0 bytes
     :test:song:
       mandatory: 0
       advisory: 0
       payload: 178 bytes
     :test:math:
       mandatory: 2
       advisory: 1
       payload: 2 bytes
 
   $ hg statbundle2 --debug < ../parts.hg2
   start processing of HG20 stream
   reading bundle2 stream parameters
   options count: 0
   start extraction of bundle2 parts
   part header size: 13
   part type: "test:empty"
   part parameters: 0
   payload chunk size: 0
   part header size: 13
   part type: "test:empty"
   part parameters: 0
   payload chunk size: 0
   part header size: 12
   part type: "test:song"
   part parameters: 0
   payload chunk size: 178
   payload chunk size: 0
   part header size: 39
   part type: "test:math"
   part parameters: 3
   payload chunk size: 2
   payload chunk size: 0
   part header size: 0
   end of bundle2 stream
   parts count:   4
     :test:empty:
       mandatory: 0
       advisory: 0
       payload: 0 bytes
     :test:empty:
       mandatory: 0
       advisory: 0
       payload: 0 bytes
     :test:song:
       mandatory: 0
       advisory: 0
       payload: 178 bytes
     :test:math:
       mandatory: 2
       advisory: 1
       payload: 2 bytes
 
 Test actual unbundling
 ========================
 
 Process the bundle
 
   $ hg unbundle2 --debug < ../parts.hg2
   start processing of HG20 stream
   reading bundle2 stream parameters
   start extraction of bundle2 parts
   part header size: 13
   part type: "test:empty"
   part parameters: 0
   payload chunk size: 0
   ignoring unknown advisory part 'test:empty'
   part header size: 13
   part type: "test:empty"
   part parameters: 0
   payload chunk size: 0
   ignoring unknown advisory part 'test:empty'
   part header size: 12
   part type: "test:song"
   part parameters: 0
   payload chunk size: 178
   payload chunk size: 0
   found an handler for part 'test:song'
   The choir start singing:
       Patali Dirapata, Cromda Cromda Ripalo, Pata Pata, Ko Ko Ko
       Bokoro Dipoulito, Rondi Rondi Pepino, Pata Pata, Ko Ko Ko
       Emana Karassoli, Loucra Loucra Ponponto, Pata Pata, Ko Ko Ko.
   part header size: 39
   part type: "test:math"
   part parameters: 3
   payload chunk size: 2
   payload chunk size: 0
   ignoring unknown advisory part 'test:math'
   part header size: 0
   end of bundle2 stream