run-tests: drop wifexited polyfill
os.WIFEXITED exists as of python 2.6 for me, so we no longer need this
polyfill.
# manifest.py - manifest revision class for mercurial
#
# Copyright 2005-2007 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from i18n import _
import mdiff, parsers, error, revlog, util
import array, struct
import os
propertycache = util.propertycache
def _parsev1(data):
# This method does a little bit of excessive-looking
# precondition checking. This is so that the behavior of this
# class exactly matches its C counterpart to try and help
# prevent surprise breakage for anyone that develops against
# the pure version.
if data and data[-1] != '\n':
raise ValueError('Manifest did not end in a newline.')
prev = None
for l in data.splitlines():
if prev is not None and prev > l:
raise ValueError('Manifest lines not in sorted order.')
prev = l
f, n = l.split('\0')
if len(n) > 40:
yield f, revlog.bin(n[:40]), n[40:]
else:
yield f, revlog.bin(n), ''
def _parsev2(data):
metadataend = data.find('\n')
# Just ignore metadata for now
pos = metadataend + 1
prevf = ''
while pos < len(data):
end = data.find('\n', pos + 1) # +1 to skip stem length byte
if end == -1:
raise ValueError('Manifest ended with incomplete file entry.')
stemlen = ord(data[pos])
items = data[pos + 1:end].split('\0')
f = prevf[:stemlen] + items[0]
if prevf > f:
raise ValueError('Manifest entries not in sorted order.')
fl = items[1]
# Just ignore metadata (items[2:] for now)
n = data[end + 1:end + 21]
yield f, n, fl
pos = end + 22
prevf = f
def _parse(data):
"""Generates (path, node, flags) tuples from a manifest text"""
if data.startswith('\0'):
return iter(_parsev2(data))
else:
return iter(_parsev1(data))
def _text(it, usemanifestv2):
"""Given an iterator over (path, node, flags) tuples, returns a manifest
text"""
if usemanifestv2:
return _textv2(it)
else:
return _textv1(it)
def _textv1(it):
files = []
lines = []
_hex = revlog.hex
for f, n, fl in it:
files.append(f)
# if this is changed to support newlines in filenames,
# be sure to check the templates/ dir again (especially *-raw.tmpl)
lines.append("%s\0%s%s\n" % (f, _hex(n), fl))
_checkforbidden(files)
return ''.join(lines)
def _textv2(it):
files = []
lines = ['\0\n']
prevf = ''
for f, n, fl in it:
files.append(f)
stem = os.path.commonprefix([prevf, f])
stemlen = min(len(stem), 255)
lines.append("%c%s\0%s\n%s\n" % (stemlen, f[stemlen:], fl, n))
prevf = f
_checkforbidden(files)
return ''.join(lines)
class _lazymanifest(dict):
"""This is the pure implementation of lazymanifest.
It has not been optimized *at all* and is not lazy.
"""
def __init__(self, data):
dict.__init__(self)
for f, n, fl in _parse(data):
self[f] = n, fl
def __setitem__(self, k, v):
node, flag = v
assert node is not None
if len(node) > 21:
node = node[:21] # match c implementation behavior
dict.__setitem__(self, k, (node, flag))
def __iter__(self):
return iter(sorted(dict.keys(self)))
def iterkeys(self):
return iter(sorted(dict.keys(self)))
def iterentries(self):
return ((f, e[0], e[1]) for f, e in sorted(self.iteritems()))
def copy(self):
c = _lazymanifest('')
c.update(self)
return c
def diff(self, m2, clean=False):
'''Finds changes between the current manifest and m2.'''
diff = {}
for fn, e1 in self.iteritems():
if fn not in m2:
diff[fn] = e1, (None, '')
else:
e2 = m2[fn]
if e1 != e2:
diff[fn] = e1, e2
elif clean:
diff[fn] = None
for fn, e2 in m2.iteritems():
if fn not in self:
diff[fn] = (None, ''), e2
return diff
def filtercopy(self, filterfn):
c = _lazymanifest('')
for f, n, fl in self.iterentries():
if filterfn(f):
c[f] = n, fl
return c
def text(self):
"""Get the full data of this manifest as a bytestring."""
return _textv1(self.iterentries())
try:
_lazymanifest = parsers.lazymanifest
except AttributeError:
pass
class manifestdict(object):
def __init__(self, data=''):
if data.startswith('\0'):
#_lazymanifest can not parse v2
self._lm = _lazymanifest('')
for f, n, fl in _parsev2(data):
self._lm[f] = n, fl
else:
self._lm = _lazymanifest(data)
def __getitem__(self, key):
return self._lm[key][0]
def find(self, key):
return self._lm[key]
def __len__(self):
return len(self._lm)
def __setitem__(self, key, node):
self._lm[key] = node, self.flags(key, '')
def __contains__(self, key):
return key in self._lm
def __delitem__(self, key):
del self._lm[key]
def __iter__(self):
return self._lm.__iter__()
def iterkeys(self):
return self._lm.iterkeys()
def keys(self):
return list(self.iterkeys())
def filesnotin(self, m2):
'''Set of files in this manifest that are not in the other'''
files = set(self)
files.difference_update(m2)
return files
@propertycache
def _dirs(self):
return util.dirs(self)
def dirs(self):
return self._dirs
def hasdir(self, dir):
return dir in self._dirs
def _filesfastpath(self, match):
'''Checks whether we can correctly and quickly iterate over matcher
files instead of over manifest files.'''
files = match.files()
return (len(files) < 100 and (match.isexact() or
(not match.anypats() and all(fn in self for fn in files))))
def walk(self, match):
'''Generates matching file names.
Equivalent to manifest.matches(match).iterkeys(), but without creating
an entirely new manifest.
It also reports nonexistent files by marking them bad with match.bad().
'''
if match.always():
for f in iter(self):
yield f
return
fset = set(match.files())
# avoid the entire walk if we're only looking for specific files
if self._filesfastpath(match):
for fn in sorted(fset):
yield fn
return
for fn in self:
if fn in fset:
# specified pattern is the exact name
fset.remove(fn)
if match(fn):
yield fn
# for dirstate.walk, files=['.'] means "walk the whole tree".
# follow that here, too
fset.discard('.')
for fn in sorted(fset):
if not self.hasdir(fn):
match.bad(fn, None)
def matches(self, match):
'''generate a new manifest filtered by the match argument'''
if match.always():
return self.copy()
if self._filesfastpath(match):
m = manifestdict()
lm = self._lm
for fn in match.files():
if fn in lm:
m._lm[fn] = lm[fn]
return m
m = manifestdict()
m._lm = self._lm.filtercopy(match)
return m
def diff(self, m2, clean=False):
'''Finds changes between the current manifest and m2.
Args:
m2: the manifest to which this manifest should be compared.
clean: if true, include files unchanged between these manifests
with a None value in the returned dictionary.
The result is returned as a dict with filename as key and
values of the form ((n1,fl1),(n2,fl2)), where n1/n2 is the
nodeid in the current/other manifest and fl1/fl2 is the flag
in the current/other manifest. Where the file does not exist,
the nodeid will be None and the flags will be the empty
string.
'''
return self._lm.diff(m2._lm, clean)
def setflag(self, key, flag):
self._lm[key] = self[key], flag
def get(self, key, default=None):
try:
return self._lm[key][0]
except KeyError:
return default
def flags(self, key, default=''):
try:
return self._lm[key][1]
except KeyError:
return default
def copy(self):
c = manifestdict()
c._lm = self._lm.copy()
return c
def iteritems(self):
return (x[:2] for x in self._lm.iterentries())
def text(self, usemanifestv2=False):
if usemanifestv2:
return _textv2(self._lm.iterentries())
else:
# use (probably) native version for v1
return self._lm.text()
def fastdelta(self, base, changes):
"""Given a base manifest text as an array.array and a list of changes
relative to that text, compute a delta that can be used by revlog.
"""
delta = []
dstart = None
dend = None
dline = [""]
start = 0
# zero copy representation of base as a buffer
addbuf = util.buffer(base)
# start with a readonly loop that finds the offset of
# each line and creates the deltas
for f, todelete in changes:
# bs will either be the index of the item or the insert point
start, end = _msearch(addbuf, f, start)
if not todelete:
h, fl = self._lm[f]
l = "%s\0%s%s\n" % (f, revlog.hex(h), fl)
else:
if start == end:
# item we want to delete was not found, error out
raise AssertionError(
_("failed to remove %s from manifest") % f)
l = ""
if dstart is not None and dstart <= start and dend >= start:
if dend < end:
dend = end
if l:
dline.append(l)
else:
if dstart is not None:
delta.append([dstart, dend, "".join(dline)])
dstart = start
dend = end
dline = [l]
if dstart is not None:
delta.append([dstart, dend, "".join(dline)])
# apply the delta to the base, and get a delta for addrevision
deltatext, arraytext = _addlistdelta(base, delta)
return arraytext, deltatext
def _msearch(m, s, lo=0, hi=None):
'''return a tuple (start, end) that says where to find s within m.
If the string is found m[start:end] are the line containing
that string. If start == end the string was not found and
they indicate the proper sorted insertion point.
m should be a buffer or a string
s is a string'''
def advance(i, c):
while i < lenm and m[i] != c:
i += 1
return i
if not s:
return (lo, lo)
lenm = len(m)
if not hi:
hi = lenm
while lo < hi:
mid = (lo + hi) // 2
start = mid
while start > 0 and m[start - 1] != '\n':
start -= 1
end = advance(start, '\0')
if m[start:end] < s:
# we know that after the null there are 40 bytes of sha1
# this translates to the bisect lo = mid + 1
lo = advance(end + 40, '\n') + 1
else:
# this translates to the bisect hi = mid
hi = start
end = advance(lo, '\0')
found = m[lo:end]
if s == found:
# we know that after the null there are 40 bytes of sha1
end = advance(end + 40, '\n')
return (lo, end + 1)
else:
return (lo, lo)
def _checkforbidden(l):
"""Check filenames for illegal characters."""
for f in l:
if '\n' in f or '\r' in f:
raise error.RevlogError(
_("'\\n' and '\\r' disallowed in filenames: %r") % f)
# apply the changes collected during the bisect loop to our addlist
# return a delta suitable for addrevision
def _addlistdelta(addlist, x):
# for large addlist arrays, building a new array is cheaper
# than repeatedly modifying the existing one
currentposition = 0
newaddlist = array.array('c')
for start, end, content in x:
newaddlist += addlist[currentposition:start]
if content:
newaddlist += array.array('c', content)
currentposition = end
newaddlist += addlist[currentposition:]
deltatext = "".join(struct.pack(">lll", start, end, len(content))
+ content for start, end, content in x)
return deltatext, newaddlist
def _splittopdir(f):
if '/' in f:
dir, subpath = f.split('/', 1)
return dir + '/', subpath
else:
return '', f
class treemanifest(object):
def __init__(self, dir='', text=''):
self._dir = dir
self._node = revlog.nullid
self._dirs = {}
# Using _lazymanifest here is a little slower than plain old dicts
self._files = {}
self._flags = {}
def readsubtree(subdir, subm):
raise AssertionError('treemanifest constructor only accepts '
'flat manifests')
self.parse(text, readsubtree)
def _subpath(self, path):
return self._dir + path
def __len__(self):
size = len(self._files)
for m in self._dirs.values():
size += m.__len__()
return size
def _isempty(self):
return (not self._files and (not self._dirs or
all(m._isempty() for m in self._dirs.values())))
def __str__(self):
return ('<treemanifest dir=%s, node=%s>' %
(self._dir, revlog.hex(self._node)))
def dir(self):
'''The directory that this tree manifest represents, including a
trailing '/'. Empty string for the repo root directory.'''
return self._dir
def node(self):
'''This node of this instance. nullid for unsaved instances. Should
be updated when the instance is read or written from a revlog.
'''
return self._node
def setnode(self, node):
self._node = node
def iteritems(self):
for p, n in sorted(self._dirs.items() + self._files.items()):
if p in self._files:
yield self._subpath(p), n
else:
for f, sn in n.iteritems():
yield f, sn
def iterkeys(self):
for p in sorted(self._dirs.keys() + self._files.keys()):
if p in self._files:
yield self._subpath(p)
else:
for f in self._dirs[p].iterkeys():
yield f
def keys(self):
return list(self.iterkeys())
def __iter__(self):
return self.iterkeys()
def __contains__(self, f):
if f is None:
return False
dir, subpath = _splittopdir(f)
if dir:
if dir not in self._dirs:
return False
return self._dirs[dir].__contains__(subpath)
else:
return f in self._files
def get(self, f, default=None):
dir, subpath = _splittopdir(f)
if dir:
if dir not in self._dirs:
return default
return self._dirs[dir].get(subpath, default)
else:
return self._files.get(f, default)
def __getitem__(self, f):
dir, subpath = _splittopdir(f)
if dir:
return self._dirs[dir].__getitem__(subpath)
else:
return self._files[f]
def flags(self, f):
dir, subpath = _splittopdir(f)
if dir:
if dir not in self._dirs:
return ''
return self._dirs[dir].flags(subpath)
else:
if f in self._dirs:
return ''
return self._flags.get(f, '')
def find(self, f):
dir, subpath = _splittopdir(f)
if dir:
return self._dirs[dir].find(subpath)
else:
return self._files[f], self._flags.get(f, '')
def __delitem__(self, f):
dir, subpath = _splittopdir(f)
if dir:
self._dirs[dir].__delitem__(subpath)
# If the directory is now empty, remove it
if self._dirs[dir]._isempty():
del self._dirs[dir]
else:
del self._files[f]
if f in self._flags:
del self._flags[f]
def __setitem__(self, f, n):
assert n is not None
dir, subpath = _splittopdir(f)
if dir:
if dir not in self._dirs:
self._dirs[dir] = treemanifest(self._subpath(dir))
self._dirs[dir].__setitem__(subpath, n)
else:
self._files[f] = n[:21] # to match manifestdict's behavior
def setflag(self, f, flags):
"""Set the flags (symlink, executable) for path f."""
assert 'd' not in flags
dir, subpath = _splittopdir(f)
if dir:
if dir not in self._dirs:
self._dirs[dir] = treemanifest(self._subpath(dir))
self._dirs[dir].setflag(subpath, flags)
else:
self._flags[f] = flags
def copy(self):
copy = treemanifest(self._dir)
copy._node = self._node
for d in self._dirs:
copy._dirs[d] = self._dirs[d].copy()
copy._files = dict.copy(self._files)
copy._flags = dict.copy(self._flags)
return copy
def filesnotin(self, m2):
'''Set of files in this manifest that are not in the other'''
files = set()
def _filesnotin(t1, t2):
for d, m1 in t1._dirs.iteritems():
if d in t2._dirs:
m2 = t2._dirs[d]
_filesnotin(m1, m2)
else:
files.update(m1.iterkeys())
for fn in t1._files.iterkeys():
if fn not in t2._files:
files.add(t1._subpath(fn))
_filesnotin(self, m2)
return files
@propertycache
def _alldirs(self):
return util.dirs(self)
def dirs(self):
return self._alldirs
def hasdir(self, dir):
topdir, subdir = _splittopdir(dir)
if topdir:
if topdir in self._dirs:
return self._dirs[topdir].hasdir(subdir)
return False
return (dir + '/') in self._dirs
def walk(self, match):
'''Generates matching file names.
Equivalent to manifest.matches(match).iterkeys(), but without creating
an entirely new manifest.
It also reports nonexistent files by marking them bad with match.bad().
'''
if match.always():
for f in iter(self):
yield f
return
fset = set(match.files())
for fn in self._walk(match):
if fn in fset:
# specified pattern is the exact name
fset.remove(fn)
yield fn
# for dirstate.walk, files=['.'] means "walk the whole tree".
# follow that here, too
fset.discard('.')
for fn in sorted(fset):
if not self.hasdir(fn):
match.bad(fn, None)
def _walk(self, match, alldirs=False):
'''Recursively generates matching file names for walk().
Will visit all subdirectories if alldirs is True, otherwise it will
only visit subdirectories for which match.visitdir is True.'''
if not alldirs:
# substring to strip trailing slash
visit = match.visitdir(self._dir[:-1] or '.')
if not visit:
return
alldirs = (visit == 'all')
# yield this dir's files and walk its submanifests
for p in sorted(self._dirs.keys() + self._files.keys()):
if p in self._files:
fullp = self._subpath(p)
if match(fullp):
yield fullp
else:
for f in self._dirs[p]._walk(match, alldirs):
yield f
def matches(self, match):
'''generate a new manifest filtered by the match argument'''
if match.always():
return self.copy()
return self._matches(match)
def _matches(self, match, alldirs=False):
'''recursively generate a new manifest filtered by the match argument.
Will visit all subdirectories if alldirs is True, otherwise it will
only visit subdirectories for which match.visitdir is True.'''
ret = treemanifest(self._dir)
if not alldirs:
# substring to strip trailing slash
visit = match.visitdir(self._dir[:-1] or '.')
if not visit:
return ret
alldirs = (visit == 'all')
for fn in self._files:
fullp = self._subpath(fn)
if not match(fullp):
continue
ret._files[fn] = self._files[fn]
if fn in self._flags:
ret._flags[fn] = self._flags[fn]
for dir, subm in self._dirs.iteritems():
m = subm._matches(match, alldirs)
if not m._isempty():
ret._dirs[dir] = m
return ret
def diff(self, m2, clean=False):
'''Finds changes between the current manifest and m2.
Args:
m2: the manifest to which this manifest should be compared.
clean: if true, include files unchanged between these manifests
with a None value in the returned dictionary.
The result is returned as a dict with filename as key and
values of the form ((n1,fl1),(n2,fl2)), where n1/n2 is the
nodeid in the current/other manifest and fl1/fl2 is the flag
in the current/other manifest. Where the file does not exist,
the nodeid will be None and the flags will be the empty
string.
'''
result = {}
emptytree = treemanifest()
def _diff(t1, t2):
for d, m1 in t1._dirs.iteritems():
m2 = t2._dirs.get(d, emptytree)
_diff(m1, m2)
for d, m2 in t2._dirs.iteritems():
if d not in t1._dirs:
_diff(emptytree, m2)
for fn, n1 in t1._files.iteritems():
fl1 = t1._flags.get(fn, '')
n2 = t2._files.get(fn, None)
fl2 = t2._flags.get(fn, '')
if n1 != n2 or fl1 != fl2:
result[t1._subpath(fn)] = ((n1, fl1), (n2, fl2))
elif clean:
result[t1._subpath(fn)] = None
for fn, n2 in t2._files.iteritems():
if fn not in t1._files:
fl2 = t2._flags.get(fn, '')
result[t2._subpath(fn)] = ((None, ''), (n2, fl2))
_diff(self, m2)
return result
def parse(self, text, readsubtree):
for f, n, fl in _parse(text):
if fl == 'd':
f = f + '/'
self._dirs[f] = readsubtree(self._subpath(f), n)
else:
# Use __setitem__ and setflag rather than assigning directly
# to _files and _flags, thereby letting us parse flat manifests
# as well as tree manifests.
self[f] = n
if fl:
self.setflag(f, fl)
def text(self, usemanifestv2=False):
"""Get the full data of this manifest as a bytestring."""
flags = self.flags
return _text(((f, self[f], flags(f)) for f in self.keys()),
usemanifestv2)
def dirtext(self, usemanifestv2=False):
"""Get the full data of this directory as a bytestring. Make sure that
any submanifests have been written first, so their nodeids are correct.
"""
flags = self.flags
dirs = [(d[:-1], self._dirs[d]._node, 'd') for d in self._dirs]
files = [(f, self._files[f], flags(f)) for f in self._files]
return _text(sorted(dirs + files), usemanifestv2)
def writesubtrees(self, m1, m2, writesubtree):
emptytree = treemanifest()
for d, subm in self._dirs.iteritems():
subp1 = m1._dirs.get(d, emptytree)._node
subp2 = m2._dirs.get(d, emptytree)._node
if subp1 == revlog.nullid:
subp1, subp2 = subp2, subp1
writesubtree(subm, subp1, subp2)
class manifest(revlog.revlog):
def __init__(self, opener, dir=''):
# During normal operations, we expect to deal with not more than four
# revs at a time (such as during commit --amend). When rebasing large
# stacks of commits, the number can go up, hence the config knob below.
cachesize = 4
usetreemanifest = False
usemanifestv2 = False
opts = getattr(opener, 'options', None)
if opts is not None:
cachesize = opts.get('manifestcachesize', cachesize)
usetreemanifest = opts.get('treemanifest', usetreemanifest)
usemanifestv2 = opts.get('manifestv2', usemanifestv2)
self._mancache = util.lrucachedict(cachesize)
self._treeinmem = usetreemanifest
self._treeondisk = usetreemanifest
self._usemanifestv2 = usemanifestv2
indexfile = "00manifest.i"
if dir:
assert self._treeondisk
if not dir.endswith('/'):
dir = dir + '/'
indexfile = "meta/" + dir + "00manifest.i"
revlog.revlog.__init__(self, opener, indexfile)
self._dir = dir
def _newmanifest(self, data=''):
if self._treeinmem:
return treemanifest(self._dir, data)
return manifestdict(data)
def _slowreaddelta(self, node):
r0 = self.deltaparent(self.rev(node))
m0 = self.read(self.node(r0))
m1 = self.read(node)
md = self._newmanifest()
for f, ((n0, fl0), (n1, fl1)) in m0.diff(m1).iteritems():
if n1:
md[f] = n1
if fl1:
md.setflag(f, fl1)
return md
def readdelta(self, node):
if self._usemanifestv2 or self._treeondisk:
return self._slowreaddelta(node)
r = self.rev(node)
d = mdiff.patchtext(self.revdiff(self.deltaparent(r), r))
return self._newmanifest(d)
def readfast(self, node):
'''use the faster of readdelta or read
This will return a manifest which is either only the files
added/modified relative to p1, or all files in the
manifest. Which one is returned depends on the codepath used
to retrieve the data.
'''
r = self.rev(node)
deltaparent = self.deltaparent(r)
if deltaparent != revlog.nullrev and deltaparent in self.parentrevs(r):
return self.readdelta(node)
return self.read(node)
def read(self, node):
if node == revlog.nullid:
return self._newmanifest() # don't upset local cache
if node in self._mancache:
return self._mancache[node][0]
text = self.revision(node)
if self._treeondisk:
def readsubtree(dir, subm):
sublog = manifest(self.opener, dir)
return sublog.read(subm)
m = self._newmanifest()
m.parse(text, readsubtree)
m.setnode(node)
arraytext = None
else:
m = self._newmanifest(text)
arraytext = array.array('c', text)
self._mancache[node] = (m, arraytext)
return m
def find(self, node, f):
'''look up entry for a single file efficiently.
return (node, flags) pair if found, (None, None) if not.'''
m = self.read(node)
try:
return m.find(f)
except KeyError:
return None, None
def add(self, m, transaction, link, p1, p2, added, removed):
if (p1 in self._mancache and not self._treeinmem
and not self._usemanifestv2):
# If our first parent is in the manifest cache, we can
# compute a delta here using properties we know about the
# manifest up-front, which may save time later for the
# revlog layer.
_checkforbidden(added)
# combine the changed lists into one list for sorting
work = [(x, False) for x in added]
work.extend((x, True) for x in removed)
# this could use heapq.merge() (from Python 2.6+) or equivalent
# since the lists are already sorted
work.sort()
arraytext, deltatext = m.fastdelta(self._mancache[p1][1], work)
cachedelta = self.rev(p1), deltatext
text = util.buffer(arraytext)
n = self.addrevision(text, transaction, link, p1, p2, cachedelta)
else:
# The first parent manifest isn't already loaded, so we'll
# just encode a fulltext of the manifest and pass that
# through to the revlog layer, and let it handle the delta
# process.
if self._treeondisk:
m1 = self.read(p1)
m2 = self.read(p2)
n = self._addtree(m, transaction, link, m1, m2)
arraytext = None
else:
text = m.text(self._usemanifestv2)
n = self.addrevision(text, transaction, link, p1, p2)
arraytext = array.array('c', text)
self._mancache[n] = (m, arraytext)
return n
def _addtree(self, m, transaction, link, m1, m2):
def writesubtree(subm, subp1, subp2):
sublog = manifest(self.opener, subm.dir())
sublog.add(subm, transaction, link, subp1, subp2, None, None)
m.writesubtrees(m1, m2, writesubtree)
text = m.dirtext(self._usemanifestv2)
# If the manifest is unchanged compared to one parent,
# don't write a new revision
if text == m1.dirtext(self._usemanifestv2):
n = m1.node()
elif text == m2.dirtext(self._usemanifestv2):
n = m2.node()
else:
n = self.addrevision(text, transaction, link, m1.node(), m2.node())
# Save nodeid so parent manifest can calculate its nodeid
m.setnode(n)
return n