pure parsers: properly detect corrupt index files

This new Python code should be equivalent in behavior to the if
statement at line 312 of parsers.c. Without this, the pure-python
parsers improperly ignore truncated revlogs as created in
test-verify.t.

mercurial/pure/parsers.py

@@ -1,88 +1,91 b''
 # parsers.py - Python implementation of parsers.c
 #
 # Copyright 2009 Matt Mackall <[e-mail]> and others
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from mercurial.node import bin, nullid
 from mercurial import util
 import struct, zlib
 
 _pack = struct.pack
 _unpack = struct.unpack
 _compress = zlib.compress
 _decompress = zlib.decompress
 _sha = util.sha1
 
 def parse_manifest(mfdict, fdict, lines):
     for l in lines.splitlines():
         f, n = l.split('\0')
         if len(n) > 40:
             fdict[f] = n[40:]
             mfdict[f] = bin(n[:40])
         else:
             mfdict[f] = bin(n)
 
 def parse_index2(data, inline):
     def gettype(q):
         return int(q & 0xFFFF)
 
     def offset_type(offset, type):
         return long(long(offset) << 16 | type)
 
     indexformatng = ">Qiiiiii20s12x"
 
     s = struct.calcsize(indexformatng)
     index = []
     cache = None
     n = off = 0
 
     l = len(data) - s
     append = index.append
     if inline:
         cache = (0, data)
         while off <= l:
             e = _unpack(indexformatng, data[off:off + s])
             append(e)
             n += 1
             if e[1] < 0:
                 break
             off += e[1] + s
     else:
         while off <= l:
             e = _unpack(indexformatng, data[off:off + s])
             append(e)
             n += 1
             off += s
 
+    if off != len(data):
+        raise ValueError('corrupt index file')
+
     if index:
         e = list(index[0])
         type = gettype(e[0])
         e[0] = offset_type(0, type)
         index[0] = tuple(e)
 
     # add the magic null revision at -1
     index.append((0, 0, 0, -1, -1, -1, -1, nullid))
 
     return index, cache
 
 def parse_dirstate(dmap, copymap, st):
     parents = [st[:20], st[20: 40]]
     # deref fields so they will be local in loop
     format = ">cllll"
     e_size = struct.calcsize(format)
     pos1 = 40
     l = len(st)
 
     # the inner loop
     while pos1 < l:
         pos2 = pos1 + e_size
         e = _unpack(">cllll", st[pos1:pos2]) # a literal here is faster
         pos1 = pos2 + e[4]
         f = st[pos2:pos1]
         if '\0' in f:
             f, c = f.split('\0')
             copymap[f] = c
         dmap[f] = e[:4]
     return parents