view tests/test-parseindex.t @ 29859:a1092e2d70a3

help: internals topic for wire protocol

The Mercurial wire protocol is under-documented. This includes a lack
of source docstrings and comments as well as pages on the official
wiki.

This patch adds the beginnings of "internals" documentation on the
wire protocol.

The documentation should have nearly complete coverage on the
lower-level parts of the protocol, such as the different transport
mechanims, how commands and arguments are sent, capabilities, and,
of course, the commands themselves.

As part of writing this documentation, I discovered a number of
deficiencies in the protocol and bugs in the implementation. I've
started sending patches for some of the issues. I hope to send a lot
more.

This patch starts with the scaffolding for a new internals page.

revlog.parseindex must be able to parse the index file even if
an index entry is split between two 64k blocks.  The ideal test
would be to create an index file with inline data where
64k < size < 64k + 64 (64k is the size of the read buffer, 64 is
the size of an index entry) and with an index entry starting right
before the 64k block boundary, and try to read it.
We approximate that by reducing the read buffer to 1 byte.

  $ hg init a
  $ cd a
  $ echo abc > foo
  $ hg add foo
  $ hg commit -m 'add foo'
  $ echo >> foo
  $ hg commit -m 'change foo'
  $ hg log -r 0:
  changeset:   0:7c31755bf9b5
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     add foo
  
  changeset:   1:26333235a41c
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     change foo
  
  $ cat >> test.py << EOF
  > from mercurial import changelog, scmutil
  > from mercurial.node import *
  > 
  > class singlebyteread(object):
  >     def __init__(self, real):
  >         self.real = real
  > 
  >     def read(self, size=-1):
  >         if size == 65536:
  >             size = 1
  >         return self.real.read(size)
  > 
  >     def __getattr__(self, key):
  >         return getattr(self.real, key)
  > 
  > def opener(*args):
  >     o = scmutil.opener(*args)
  >     def wrapper(*a):
  >         f = o(*a)
  >         return singlebyteread(f)
  >     return wrapper
  > 
  > cl = changelog.changelog(opener('.hg/store'))
  > print len(cl), 'revisions:'
  > for r in cl:
  >     print short(cl.node(r))
  > EOF
  $ python test.py
  2 revisions:
  7c31755bf9b5
  26333235a41c

  $ cd ..

#if no-pure

Test SEGV caused by bad revision passed to reachableroots() (issue4775):

  $ cd a

  $ python <<EOF
  > from mercurial import changelog, scmutil
  > cl = changelog.changelog(scmutil.vfs('.hg/store'))
  > print 'good heads:'
  > for head in [0, len(cl) - 1, -1]:
  >     print'%s: %r' % (head, cl.reachableroots(0, [head], [0]))
  > print 'bad heads:'
  > for head in [len(cl), 10000, -2, -10000, None]:
  >     print '%s:' % head,
  >     try:
  >         cl.reachableroots(0, [head], [0])
  >         print 'uncaught buffer overflow?'
  >     except (IndexError, TypeError) as inst:
  >         print inst
  > print 'good roots:'
  > for root in [0, len(cl) - 1, -1]:
  >     print '%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root]))
  > print 'out-of-range roots are ignored:'
  > for root in [len(cl), 10000, -2, -10000]:
  >     print '%s: %r' % (root, cl.reachableroots(root, [len(cl) - 1], [root]))
  > print 'bad roots:'
  > for root in [None]:
  >     print '%s:' % root,
  >     try:
  >         cl.reachableroots(root, [len(cl) - 1], [root])
  >         print 'uncaught error?'
  >     except TypeError as inst:
  >         print inst
  > EOF
  good heads:
  0: [0]
  1: [0]
  -1: []
  bad heads:
  2: head out of range
  10000: head out of range
  -2: head out of range
  -10000: head out of range
  None: an integer is required
  good roots:
  0: [0]
  1: [1]
  -1: [-1]
  out-of-range roots are ignored:
  2: []
  10000: []
  -2: []
  -10000: []
  bad roots:
  None: an integer is required

  $ cd ..

Test corrupted p1/p2 fields that could cause SEGV at parsers.c:

  $ mkdir invalidparent
  $ cd invalidparent

  $ hg clone --pull -q --config phases.publish=False ../a limit
  $ hg clone --pull -q --config phases.publish=False ../a segv
  $ rm -R limit/.hg/cache segv/.hg/cache

  $ python <<EOF
  > data = open("limit/.hg/store/00changelog.i", "rb").read()
  > for n, p in [('limit', '\0\0\0\x02'), ('segv', '\0\x01\0\0')]:
  >     # corrupt p1 at rev0 and p2 at rev1
  >     d = data[:24] + p + data[28:127 + 28] + p + data[127 + 32:]
  >     open(n + "/.hg/store/00changelog.i", "wb").write(d)
  > EOF

  $ hg debugindex -f1 limit/.hg/store/00changelog.i
     rev flag   offset   length     size   base   link     p1     p2       nodeid
       0 0000        0       63       62      0      0      2     -1 7c31755bf9b5
       1 0000       63       66       65      1      1      0      2 26333235a41c
  $ hg debugindex -f1 segv/.hg/store/00changelog.i
     rev flag   offset   length     size   base   link     p1     p2       nodeid
       0 0000        0       63       62      0      0  65536     -1 7c31755bf9b5
       1 0000       63       66       65      1      1      0  65536 26333235a41c

  $ cat <<EOF > test.py
  > import sys
  > from mercurial import changelog, scmutil
  > cl = changelog.changelog(scmutil.vfs(sys.argv[1]))
  > n0, n1 = cl.node(0), cl.node(1)
  > ops = [
  >     ('reachableroots',
  >      lambda: cl.index.reachableroots2(0, [1], [0], False)),
  >     ('compute_phases_map_sets', lambda: cl.computephases([[0], []])),
  >     ('index_headrevs', lambda: cl.headrevs()),
  >     ('find_gca_candidates', lambda: cl.commonancestorsheads(n0, n1)),
  >     ('find_deepest', lambda: cl.ancestor(n0, n1)),
  >     ]
  > for l, f in ops:
  >     print l + ':',
  >     try:
  >         f()
  >         print 'uncaught buffer overflow?'
  >     except ValueError, inst:
  >         print inst
  > EOF

  $ python test.py limit/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range
  $ python test.py segv/.hg/store
  reachableroots: parent out of range
  compute_phases_map_sets: parent out of range
  index_headrevs: parent out of range
  find_gca_candidates: parent out of range
  find_deepest: parent out of range

  $ cd ..

#endif