Mercurial > public > mercurial-scm > hg-stable

diff mercurial/bundle2.py @ 23009:90f86ad3d4ff

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bundle2: change header size and make them signed (new format) We are changing all integers that denote the size of a chunk to read to int32. There are two main motivations for that. First, we change everything to the same width (32 bits) to make it possible for a reasonably agnostic actor to forward a bundle2 without any extra processing. With this change, this could be achieved by just reading int32s and forwarding chunks of the size read. A bit a smartness would be logic to detect the end of stream but nothing too complicated. Second, we need some capacity to transmit special information during the bundle processing. For example we would like to be able to raise an exception while a part is being read if this exception happend while this part was generated. Having signed integer let us use negative numbers to trigger special events during the parsing of the bundle. The format is renamed for B2X to B2Y because this breaks binary compatibility. The B2X format support is dropped. It was experimental to allow this kind of things. All elements not directly related to the binary format remain flagged "b2x" because they are still compatible.
author Pierre-Yves David <pierre-yves.david@fb.com>
date Wed, 01 Oct 2014 23:40:23 -0500
parents d3137827016a
children 73f394f4affc
line wrap: on
line diff
--- a/mercurial/bundle2.py	Tue Oct 14 02:32:26 2014 -0700
+++ b/mercurial/bundle2.py	Wed Oct 01 23:40:23 2014 -0500
@@ -31,7 +31,7 @@
 
 Binary format is as follow
 
-:params size: (16 bits integer)
+:params size: int32
 
   The total number of Bytes used by the parameters
 
@@ -64,7 +64,7 @@
 
 Binary format is as follow
 
-:header size: (16 bits inter)
+:header size: int32
 
   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.
@@ -119,12 +119,15 @@
 
     payload is a series of `<chunksize><chunkdata>`.
 
-    `chunksize` is a 32 bits integer, `chunkdata` are plain bytes (as much as
+    `chunksize` is an int32, `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 ultimately be lifted.
 
+    `chunksize` can be negative to trigger special case processing. No such
+    processing is in place yet.
+
 Bundle processing
 ============================
 
@@ -155,13 +158,13 @@
 _pack = struct.pack
 _unpack = struct.unpack
 
-_magicstring = 'HG2X'
+_magicstring = 'HG2Y'
 
-_fstreamparamsize = '>H'
-_fpartheadersize = '>H'
+_fstreamparamsize = '>i'
+_fpartheadersize = '>i'
 _fparttypesize = '>B'
 _fpartid = '>I'
-_fpayloadsize = '>I'
+_fpayloadsize = '>i'
 _fpartparamcount = '>BB'
 
 preferedchunksize = 4096
@@ -496,7 +499,7 @@
             magic, version = header[0:2], header[2:4]
             if magic != 'HG':
                 raise util.Abort(_('not a Mercurial bundle'))
-            if version != '2X':
+            if version != '2Y':
                 raise util.Abort(_('unknown bundle version %s') % version)
         self.ui.debug('start processing of %s stream\n' % header)
 
@@ -781,7 +784,7 @@
             self.consumed = True
         return data
 
-capabilities = {'HG2X': (),
+capabilities = {'HG2Y': (),
                 'b2x:listkeys': (),
                 'b2x:pushkey': (),
                 'b2x:changegroup': (),