Implement revlogng.
revlogng results in smaller indexes, can address larger data files, and
supports flags and version numbers.
By default the original revlog format is used. To use the new format,
use the following .hgrc field:
[revlog]
# format choices are 0 (classic revlog format) and 1 revlogng
format=1
"""
revlog.py - storage back-end for mercurial
This provides efficient delta storage with O(1) retrieve and append
and O(changes) merge between branches
Copyright 2005 Matt Mackall <mpm@selenic.com>
This software may be used and distributed according to the terms
of the GNU General Public License, incorporated herein by reference.
"""
from node import *
from i18n import gettext as _
from demandload import demandload
demandload(globals(), "binascii changegroup errno heapq mdiff os")
demandload(globals(), "sha struct zlib")
# revlog version strings
REVLOGV0 = 0
REVLOGNG = 1
def hash(text, p1, p2):
"""generate a hash from the given text and its parent hashes
This hash combines both the current file contents and its history
in a manner that makes it easy to distinguish nodes with the same
content in the revision graph.
"""
l = [p1, p2]
l.sort()
s = sha.new(l[0])
s.update(l[1])
s.update(text)
return s.digest()
def compress(text):
""" generate a possibly-compressed representation of text """
if not text: return ("", text)
if len(text) < 44:
if text[0] == '\0': return ("", text)
return ('u', text)
bin = zlib.compress(text)
if len(bin) > len(text):
if text[0] == '\0': return ("", text)
return ('u', text)
return ("", bin)
def decompress(bin):
""" decompress the given input """
if not bin: return bin
t = bin[0]
if t == '\0': return bin
if t == 'x': return zlib.decompress(bin)
if t == 'u': return bin[1:]
raise RevlogError(_("unknown compression type %r") % t)
indexformatv0 = ">4l20s20s20s"
# index ng:
# 6 bytes offset
# 2 bytes flags
# 4 bytes compressed length
# 4 bytes uncompressed length
# 4 bytes: base rev
# 4 bytes link rev
# 4 bytes parent 1 rev
# 4 bytes parent 2 rev
# 32 bytes: nodeid
indexformatng = ">Qiiiiii20s12x"
versionformat = ">i"
class lazyparser(object):
"""
this class avoids the need to parse the entirety of large indices
By default we parse and load 1000 entries at a time.
If no position is specified, we load the whole index, and replace
the lazy objects in revlog with the underlying objects for
efficiency in cases where we look at most of the nodes.
"""
def __init__(self, data, revlog, indexformat):
self.data = data
self.s = struct.calcsize(indexformat)
self.indexformat = indexformat
self.l = len(data)/self.s
self.index = [None] * self.l
self.map = {nullid: -1}
self.all = 0
self.revlog = revlog
def load(self, pos=None):
if self.all: return
if pos is not None:
block = pos / 1000
i = block * 1000
end = min(self.l, i + 1000)
else:
self.all = 1
i = 0
end = self.l
self.revlog.index = self.index
self.revlog.nodemap = self.map
while i < end:
if not self.index[i]:
d = self.data[i * self.s: (i + 1) * self.s]
e = struct.unpack(self.indexformat, d)
self.index[i] = e
self.map[e[-1]] = i
i += 1
class lazyindex(object):
"""a lazy version of the index array"""
def __init__(self, parser):
self.p = parser
def __len__(self):
return len(self.p.index)
def load(self, pos):
if pos < 0:
pos += len(self.p.index)
self.p.load(pos)
return self.p.index[pos]
def __getitem__(self, pos):
return self.p.index[pos] or self.load(pos)
def __setitem__(self, pos, item):
self.p.index[pos] = item
def __delitem__(self, pos):
del self.p.index[pos]
def append(self, e):
self.p.index.append(e)
class lazymap(object):
"""a lazy version of the node map"""
def __init__(self, parser):
self.p = parser
def load(self, key):
if self.p.all: return
n = self.p.data.find(key)
if n < 0:
raise KeyError(key)
pos = n / self.p.s
self.p.load(pos)
def __contains__(self, key):
self.p.load()
return key in self.p.map
def __iter__(self):
yield nullid
for i in xrange(self.p.l):
try:
yield self.p.index[i][-1]
except:
self.p.load(i)
yield self.p.index[i][-1]
def __getitem__(self, key):
try:
return self.p.map[key]
except KeyError:
try:
self.load(key)
return self.p.map[key]
except KeyError:
raise KeyError("node " + hex(key))
def __setitem__(self, key, val):
self.p.map[key] = val
def __delitem__(self, key):
del self.p.map[key]
class RevlogError(Exception): pass
class revlog(object):
"""
the underlying revision storage object
A revlog consists of two parts, an index and the revision data.
The index is a file with a fixed record size containing
information on each revision, includings its nodeid (hash), the
nodeids of its parents, the position and offset of its data within
the data file, and the revision it's based on. Finally, each entry
contains a linkrev entry that can serve as a pointer to external
data.
The revision data itself is a linear collection of data chunks.
Each chunk represents a revision and is usually represented as a
delta against the previous chunk. To bound lookup time, runs of
deltas are limited to about 2 times the length of the original
version data. This makes retrieval of a version proportional to
its size, or O(1) relative to the number of revisions.
Both pieces of the revlog are written to in an append-only
fashion, which means we never need to rewrite a file to insert or
remove data, and can use some simple techniques to avoid the need
for locking while reading.
"""
def __init__(self, opener, indexfile, datafile, defversion=0):
"""
create a revlog object
opener is a function that abstracts the file opening operation
and can be used to implement COW semantics or the like.
"""
self.indexfile = indexfile
self.datafile = datafile
self.opener = opener
self.indexstat = None
self.cache = None
self.chunkcache = None
self.defversion = defversion
self.load()
def load(self):
v = self.defversion
try:
f = self.opener(self.indexfile)
i = f.read()
except IOError, inst:
if inst.errno != errno.ENOENT:
raise
i = ""
else:
try:
st = os.fstat(f.fileno())
except AttributeError, inst:
st = None
else:
oldst = self.indexstat
if (oldst and st.st_dev == oldst.st_dev
and st.st_ino == oldst.st_ino
and st.st_mtime == oldst.st_mtime
and st.st_ctime == oldst.st_ctime):
return
self.indexstat = st
if len(i) > 0:
v = struct.unpack(versionformat, i[:4])[0]
if v != 0:
flags = v & ~0xFFFF
fmt = v & 0xFFFF
if fmt != REVLOGNG or (flags & ~(REVLOGNGINLINEDATA)):
raise RevlogError(
_("unknown version format %d or flags %x on %s") %
(v, flags, self.indexfile))
self.version = v
if v == 0:
self.indexformat = indexformatv0
else:
self.indexformat = indexformatng
if i:
if st and st.st_size > 10000:
# big index, let's parse it on demand
parser = lazyparser(i, self, self.indexformat)
self.index = lazyindex(parser)
self.nodemap = lazymap(parser)
else:
self.parseindex(i)
if self.version != 0:
e = list(self.index[0])
type = self.ngtype(e[0])
e[0] = self.offset_type(0, type)
self.index[0] = e
else:
self.nodemap = { nullid: -1}
self.index = []
def parseindex(self, data):
s = struct.calcsize(self.indexformat)
l = len(data)
self.index = []
self.nodemap = {nullid: -1}
off = 0
n = 0
while off < l:
e = struct.unpack(self.indexformat, data[off:off + s])
self.index.append(e)
self.nodemap[e[-1]] = n
n += 1
off += s
def ngoffset(self, q):
if q & 0xFFFF:
raise RevlogError(_('%s: incompatible revision flag %x') %
(self.indexfile, type))
return long(q >> 16)
def ngtype(self, q):
return int(q & 0xFFFF)
def offset_type(self, offset, type):
return long(long(offset) << 16 | type)
def loadindexmap(self):
"""loads both the map and the index from the lazy parser"""
if isinstance(self.index, lazyindex):
p = self.index.p
p.load()
def tip(self): return self.node(len(self.index) - 1)
def count(self): return len(self.index)
def node(self, rev):
return (rev < 0) and nullid or self.index[rev][-1]
def rev(self, node):
try:
return self.nodemap[node]
except KeyError:
raise RevlogError(_('%s: no node %s') % (self.indexfile, hex(node)))
def linkrev(self, node): return self.index[self.rev(node)][-4]
def parents(self, node):
if node == nullid: return (nullid, nullid)
r = self.rev(node)
d = self.index[r][-3:-1]
if self.version == 0:
return d
return [ self.node(x) for x in d ]
def start(self, rev):
if rev < 0:
return -1
if self.version != 0:
return self.ngoffset(self.index[rev][0])
return self.index[rev][0]
def end(self, rev): return self.start(rev) + self.length(rev)
def length(self, rev):
if rev < 0:
return 0
else:
return self.index[rev][1]
def base(self, rev): return (rev < 0) and rev or self.index[rev][-5]
def reachable(self, rev, stop=None):
reachable = {}
visit = [rev]
reachable[rev] = 1
if stop:
stopn = self.rev(stop)
else:
stopn = 0
while visit:
n = visit.pop(0)
if n == stop:
continue
if n == nullid:
continue
for p in self.parents(n):
if self.rev(p) < stopn:
continue
if p not in reachable:
reachable[p] = 1
visit.append(p)
return reachable
def nodesbetween(self, roots=None, heads=None):
"""Return a tuple containing three elements. Elements 1 and 2 contain
a final list bases and heads after all the unreachable ones have been
pruned. Element 0 contains a topologically sorted list of all
nodes that satisfy these constraints:
1. All nodes must be descended from a node in roots (the nodes on
roots are considered descended from themselves).
2. All nodes must also be ancestors of a node in heads (the nodes in
heads are considered to be their own ancestors).
If roots is unspecified, nullid is assumed as the only root.
If heads is unspecified, it is taken to be the output of the
heads method (i.e. a list of all nodes in the repository that
have no children)."""
nonodes = ([], [], [])
if roots is not None:
roots = list(roots)
if not roots:
return nonodes
lowestrev = min([self.rev(n) for n in roots])
else:
roots = [nullid] # Everybody's a descendent of nullid
lowestrev = -1
if (lowestrev == -1) and (heads is None):
# We want _all_ the nodes!
return ([self.node(r) for r in xrange(0, self.count())],
[nullid], list(self.heads()))
if heads is None:
# All nodes are ancestors, so the latest ancestor is the last
# node.
highestrev = self.count() - 1
# Set ancestors to None to signal that every node is an ancestor.
ancestors = None
# Set heads to an empty dictionary for later discovery of heads
heads = {}
else:
heads = list(heads)
if not heads:
return nonodes
ancestors = {}
# Start at the top and keep marking parents until we're done.
nodestotag = heads[:]
# Turn heads into a dictionary so we can remove 'fake' heads.
# Also, later we will be using it to filter out the heads we can't
# find from roots.
heads = dict.fromkeys(heads, 0)
# Remember where the top was so we can use it as a limit later.
highestrev = max([self.rev(n) for n in nodestotag])
while nodestotag:
# grab a node to tag
n = nodestotag.pop()
# Never tag nullid
if n == nullid:
continue
# A node's revision number represents its place in a
# topologically sorted list of nodes.
r = self.rev(n)
if r >= lowestrev:
if n not in ancestors:
# If we are possibly a descendent of one of the roots
# and we haven't already been marked as an ancestor
ancestors[n] = 1 # Mark as ancestor
# Add non-nullid parents to list of nodes to tag.
nodestotag.extend([p for p in self.parents(n) if
p != nullid])
elif n in heads: # We've seen it before, is it a fake head?
# So it is, real heads should not be the ancestors of
# any other heads.
heads.pop(n)
if not ancestors:
return nonodes
# Now that we have our set of ancestors, we want to remove any
# roots that are not ancestors.
# If one of the roots was nullid, everything is included anyway.
if lowestrev > -1:
# But, since we weren't, let's recompute the lowest rev to not
# include roots that aren't ancestors.
# Filter out roots that aren't ancestors of heads
roots = [n for n in roots if n in ancestors]
# Recompute the lowest revision
if roots:
lowestrev = min([self.rev(n) for n in roots])
else:
# No more roots? Return empty list
return nonodes
else:
# We are descending from nullid, and don't need to care about
# any other roots.
lowestrev = -1
roots = [nullid]
# Transform our roots list into a 'set' (i.e. a dictionary where the
# values don't matter.
descendents = dict.fromkeys(roots, 1)
# Also, keep the original roots so we can filter out roots that aren't
# 'real' roots (i.e. are descended from other roots).
roots = descendents.copy()
# Our topologically sorted list of output nodes.
orderedout = []
# Don't start at nullid since we don't want nullid in our output list,
# and if nullid shows up in descedents, empty parents will look like
# they're descendents.
for r in xrange(max(lowestrev, 0), highestrev + 1):
n = self.node(r)
isdescendent = False
if lowestrev == -1: # Everybody is a descendent of nullid
isdescendent = True
elif n in descendents:
# n is already a descendent
isdescendent = True
# This check only needs to be done here because all the roots
# will start being marked is descendents before the loop.
if n in roots:
# If n was a root, check if it's a 'real' root.
p = tuple(self.parents(n))
# If any of its parents are descendents, it's not a root.
if (p[0] in descendents) or (p[1] in descendents):
roots.pop(n)
else:
p = tuple(self.parents(n))
# A node is a descendent if either of its parents are
# descendents. (We seeded the dependents list with the roots
# up there, remember?)
if (p[0] in descendents) or (p[1] in descendents):
descendents[n] = 1
isdescendent = True
if isdescendent and ((ancestors is None) or (n in ancestors)):
# Only include nodes that are both descendents and ancestors.
orderedout.append(n)
if (ancestors is not None) and (n in heads):
# We're trying to figure out which heads are reachable
# from roots.
# Mark this head as having been reached
heads[n] = 1
elif ancestors is None:
# Otherwise, we're trying to discover the heads.
# Assume this is a head because if it isn't, the next step
# will eventually remove it.
heads[n] = 1
# But, obviously its parents aren't.
for p in self.parents(n):
heads.pop(p, None)
heads = [n for n in heads.iterkeys() if heads[n] != 0]
roots = roots.keys()
assert orderedout
assert roots
assert heads
return (orderedout, roots, heads)
def heads(self, start=None):
"""return the list of all nodes that have no children
if start is specified, only heads that are descendants of
start will be returned
"""
if start is None:
start = nullid
reachable = {start: 1}
heads = {start: 1}
startrev = self.rev(start)
for r in xrange(startrev + 1, self.count()):
n = self.node(r)
for pn in self.parents(n):
if pn in reachable:
reachable[n] = 1
heads[n] = 1
if pn in heads:
del heads[pn]
return heads.keys()
def children(self, node):
"""find the children of a given node"""
c = []
p = self.rev(node)
for r in range(p + 1, self.count()):
n = self.node(r)
for pn in self.parents(n):
if pn == node:
c.append(n)
continue
elif pn == nullid:
continue
return c
def lookup(self, id):
"""locate a node based on revision number or subset of hex nodeid"""
try:
rev = int(id)
if str(rev) != id: raise ValueError
if rev < 0: rev = self.count() + rev
if rev < 0 or rev >= self.count(): raise ValueError
return self.node(rev)
except (ValueError, OverflowError):
c = []
for n in self.nodemap:
if hex(n).startswith(id):
c.append(n)
if len(c) > 1: raise RevlogError(_("Ambiguous identifier"))
if len(c) < 1: raise RevlogError(_("No match found"))
return c[0]
return None
def diff(self, a, b):
"""return a delta between two revisions"""
return mdiff.textdiff(a, b)
def patches(self, t, pl):
"""apply a list of patches to a string"""
return mdiff.patches(t, pl)
def chunk(self, rev, df=None, cachelen=4096):
start, length = self.start(rev), self.length(rev)
end = start + length
def loadcache(df):
cache_length = max(cachelen, length) # 4k
if not df:
df = self.opener(self.datafile)
df.seek(start)
self.chunkcache = (start, df.read(cache_length))
if not self.chunkcache:
loadcache(df)
cache_start = self.chunkcache[0]
cache_end = cache_start + len(self.chunkcache[1])
if start >= cache_start and end <= cache_end:
# it is cached
offset = start - cache_start
else:
loadcache(df)
offset = 0
#def checkchunk():
# df = self.opener(self.datafile)
# df.seek(start)
# return df.read(length)
#assert s == checkchunk()
return decompress(self.chunkcache[1][offset:offset + length])
def delta(self, node):
"""return or calculate a delta between a node and its predecessor"""
r = self.rev(node)
return self.revdiff(r - 1, r)
def revdiff(self, rev1, rev2):
"""return or calculate a delta between two revisions"""
b1 = self.base(rev1)
b2 = self.base(rev2)
if b1 == b2 and rev1 + 1 == rev2:
return self.chunk(rev2)
else:
return self.diff(self.revision(self.node(rev1)),
self.revision(self.node(rev2)))
def revision(self, node):
"""return an uncompressed revision of a given"""
if node == nullid: return ""
if self.cache and self.cache[0] == node: return self.cache[2]
# look up what we need to read
text = None
rev = self.rev(node)
base = self.base(rev)
df = self.opener(self.datafile)
# do we have useful data cached?
if self.cache and self.cache[1] >= base and self.cache[1] < rev:
base = self.cache[1]
text = self.cache[2]
else:
text = self.chunk(base, df=df)
bins = []
for r in xrange(base + 1, rev + 1):
bins.append(self.chunk(r, df=df))
text = self.patches(text, bins)
p1, p2 = self.parents(node)
if node != hash(text, p1, p2):
raise RevlogError(_("integrity check failed on %s:%d")
% (self.datafile, rev))
self.cache = (node, rev, text)
return text
def addrevision(self, text, transaction, link, p1=None, p2=None, d=None):
"""add a revision to the log
text - the revision data to add
transaction - the transaction object used for rollback
link - the linkrev data to add
p1, p2 - the parent nodeids of the revision
d - an optional precomputed delta
"""
if text is None: text = ""
if p1 is None: p1 = self.tip()
if p2 is None: p2 = nullid
node = hash(text, p1, p2)
if node in self.nodemap:
return node
n = self.count()
t = n - 1
if n:
base = self.base(t)
start = self.start(base)
end = self.end(t)
if not d:
prev = self.revision(self.tip())
d = self.diff(prev, str(text))
data = compress(d)
l = len(data[1]) + len(data[0])
dist = end - start + l
# full versions are inserted when the needed deltas
# become comparable to the uncompressed text
if not n or dist > len(text) * 2:
data = compress(text)
l = len(data[1]) + len(data[0])
base = n
else:
base = self.base(t)
offset = 0
if t >= 0:
offset = self.end(t)
if self.version == 0:
e = (offset, l, base, link, p1, p2, node)
else:
e = (self.offset_type(offset, 0), l, len(text),
base, link, self.rev(p1), self.rev(p2), node)
self.index.append(e)
self.nodemap[node] = n
entry = struct.pack(self.indexformat, *e)
transaction.add(self.datafile, offset)
transaction.add(self.indexfile, n * len(entry))
f = self.opener(self.datafile, "a")
if data[0]:
f.write(data[0])
f.write(data[1])
f = self.opener(self.indexfile, "a")
if len(self.index) == 1 and self.version != 0:
l = struct.pack(versionformat, self.version)
f.write(l)
entry = entry[4:]
f.write(entry)
self.cache = (node, n, text)
return node
def ancestor(self, a, b):
"""calculate the least common ancestor of nodes a and b"""
# calculate the distance of every node from root
dist = {nullid: 0}
for i in xrange(self.count()):
n = self.node(i)
p1, p2 = self.parents(n)
dist[n] = max(dist[p1], dist[p2]) + 1
# traverse ancestors in order of decreasing distance from root
def ancestors(node):
# we store negative distances because heap returns smallest member
h = [(-dist[node], node)]
seen = {}
while h:
d, n = heapq.heappop(h)
if n not in seen:
seen[n] = 1
yield (-d, n)
for p in self.parents(n):
heapq.heappush(h, (-dist[p], p))
def generations(node):
sg, s = None, {}
for g,n in ancestors(node):
if g != sg:
if sg:
yield sg, s
sg, s = g, {n:1}
else:
s[n] = 1
yield sg, s
x = generations(a)
y = generations(b)
gx = x.next()
gy = y.next()
# increment each ancestor list until it is closer to root than
# the other, or they match
while 1:
#print "ancestor gen %s %s" % (gx[0], gy[0])
if gx[0] == gy[0]:
# find the intersection
i = [ n for n in gx[1] if n in gy[1] ]
if i:
return i[0]
else:
#print "next"
gy = y.next()
gx = x.next()
elif gx[0] < gy[0]:
#print "next y"
gy = y.next()
else:
#print "next x"
gx = x.next()
def group(self, nodelist, lookup, infocollect=None):
"""calculate a delta group
Given a list of changeset revs, return a set of deltas and
metadata corresponding to nodes. the first delta is
parent(nodes[0]) -> nodes[0] the receiver is guaranteed to
have this parent as it has all history before these
changesets. parent is parent[0]
"""
revs = [self.rev(n) for n in nodelist]
# if we don't have any revisions touched by these changesets, bail
if not revs:
yield changegroup.closechunk()
return
# add the parent of the first rev
p = self.parents(self.node(revs[0]))[0]
revs.insert(0, self.rev(p))
# build deltas
for d in xrange(0, len(revs) - 1):
a, b = revs[d], revs[d + 1]
nb = self.node(b)
if infocollect is not None:
infocollect(nb)
d = self.revdiff(a, b)
p = self.parents(nb)
meta = nb + p[0] + p[1] + lookup(nb)
yield changegroup.genchunk("%s%s" % (meta, d))
yield changegroup.closechunk()
def addgroup(self, revs, linkmapper, transaction, unique=0):
"""
add a delta group
given a set of deltas, add them to the revision log. the
first delta is against its parent, which should be in our
log, the rest are against the previous delta.
"""
#track the base of the current delta log
r = self.count()
t = r - 1
node = None
base = prev = -1
start = end = measure = 0
if r:
end = self.end(t)
ifh = self.opener(self.indexfile, "a+")
transaction.add(self.indexfile, ifh.tell())
transaction.add(self.datafile, end)
dfh = self.opener(self.datafile, "a")
# loop through our set of deltas
chain = None
for chunk in revs:
node, p1, p2, cs = struct.unpack("20s20s20s20s", chunk[:80])
link = linkmapper(cs)
if node in self.nodemap:
# this can happen if two branches make the same change
# if unique:
# raise RevlogError(_("already have %s") % hex(node[:4]))
chain = node
continue
delta = chunk[80:]
for p in (p1, p2):
if not p in self.nodemap:
raise RevlogError(_("unknown parent %s") % short(p1))
if not chain:
# retrieve the parent revision of the delta chain
chain = p1
if not chain in self.nodemap:
raise RevlogError(_("unknown base %s") % short(chain[:4]))
# full versions are inserted when the needed deltas become
# comparable to the uncompressed text or when the previous
# version is not the one we have a delta against. We use
# the size of the previous full rev as a proxy for the
# current size.
if chain == prev:
tempd = compress(delta)
cdelta = tempd[0] + tempd[1]
if chain != prev or (end - start + len(cdelta)) > measure * 2:
# flush our writes here so we can read it in revision
if dfh:
dfh.flush()
ifh.flush()
text = self.revision(chain)
text = self.patches(text, [delta])
chk = self.addrevision(text, transaction, link, p1, p2)
if chk != node:
raise RevlogError(_("consistency error adding group"))
measure = len(text)
else:
if self.version == 0:
e = (end, len(cdelta), base, link, p1, p2, node)
else:
e = (self.offset_type(end, 0), len(cdelta), -1, base,
link, self.rev(p1), self.rev(p2), node)
self.index.append(e)
self.nodemap[node] = r
dfh.write(cdelta)
ifh.write(struct.pack(self.indexformat, *e))
t, r, chain, prev = r, r + 1, node, node
base = self.base(t)
start = self.start(base)
end = self.end(t)
if node is None:
raise RevlogError(_("group to be added is empty"))
return node
def strip(self, rev, minlink):
if self.count() == 0 or rev >= self.count():
return
if isinstance(self.index, lazyindex):
self.loadindexmap()
# When stripping away a revision, we need to make sure it
# does not actually belong to an older changeset.
# The minlink parameter defines the oldest revision
# we're allowed to strip away.
while minlink > self.index[rev][-4]:
rev += 1
if rev >= self.count():
return
# first truncate the files on disk
end = self.start(rev)
df = self.opener(self.datafile, "a")
df.truncate(end)
end = rev * struct.calcsize(self.indexformat)
indexf = self.opener(self.indexfile, "a")
indexf.truncate(end)
# then reset internal state in memory to forget those revisions
self.cache = None
self.chunkcache = None
for x in xrange(rev, self.count()):
del self.nodemap[self.node(x)]
del self.index[rev:]
def checksize(self):
expected = 0
if self.count():
expected = self.end(self.count() - 1)
try:
f = self.opener(self.datafile)
f.seek(0, 2)
actual = f.tell()
dd = actual - expected
except IOError, inst:
if inst.errno != errno.ENOENT:
raise
dd = 0
try:
f = self.opener(self.indexfile)
f.seek(0, 2)
actual = f.tell()
s = struct.calcsize(self.indexformat)
i = actual / s
di = actual - (i * s)
except IOError, inst:
if inst.errno != errno.ENOENT:
raise
di = 0
return (dd, di)