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# Copyright 2008 The Tor Project, Inc. See LICENSE for licensing information.
import os
import sys
import tempfile
import random
try:
import json
except ImportError:
import simplejson as json
import thandy.formats
import thandy.keys
import thandy.master_keys
def moveFile(fromLocation, toLocation):
if sys.platform in ('cygwin', 'win32'):
# Win32 doesn't let rename replace an existing file.
try:
os.unlink(toLocation)
except OSError:
pass
os.rename(fromLocation, toLocation)
def replaceFile(fname, contents, textMode=False):
"""overwrite the file in 'fname' atomically with the content of 'contents'
"""
dir, prefix = os.path.split(fname)
fd, fname_tmp = tempfile.mkstemp(prefix=prefix, dir=dir, text=textMode)
try:
os.write(fd, contents)
finally:
os.close(fd)
moveFile(fname_tmp, fname)
def userFilename(name):
try:
base = os.environ["THANDY_HOME"]
except KeyError:
base = "~/.thandy"
base = os.path.expanduser(base)
if not os.path.exists(base):
os.makedirs(base, 0700)
return os.path.join(base, name)
def ensureParentDir(name):
"""DOCDOC"""
directory = os.path.split(name)[0]
if not os.path.exists(directory):
os.makedirs(directory, 0700)
def getKeylist(keys_fname, checkKeys=True):
import thandy.master_keys
keydb = thandy.formats.Keylist()
for key in thandy.master_keys.MASTER_KEYS:
keydb.addKey(thandy.keys.RSAKey.fromJSon(key))
user_keys = userFilename("preload_keys")
if os.path.exists(user_keys):
#XXXX somewhat roundabout.
keylist = thandy.formats.makeKeylistObj(user_keys)
keydb.addFromKeylist(keylist, allowMasterKeys=True)
if keys_fname and os.path.exists(keys_fname):
f = open(keys_fname, 'r')
try:
obj = json.load(f)
finally:
f.close()
ss, role, path = thandy.formats.checkSignedObj(obj, keydb)
if role != 'master':
raise thandy.FormatException("%s wasn't a keylist."%keys_fname)
if checkKeys and not ss.isValid():
raise thandy.FormatException("%s not signed by enough master keys"%
keys_fname)
keydb.addFromKeylist(obj['signed'], allowMasterKeys=False)
return keydb
def randChooseWeighted(lst):
"""Given a list of (weight,item) tuples, pick an item with
probability proportional to its weight.
"""
totalweight = sum(w for w,i in lst)
position = random.uniform(0, totalweight)
soFar = 0
# We could use bisect here, but this is not going to be in the
# critical path. If it is, oops.
for w,i in lst:
soFar += w
if position < soFar:
return i
return lst[-1][1]
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