ant*_*ony 7 python hash persistence pickle hashlib
我想创建一个hashlib实例，update()然后以某种方式保留其状态。稍后，我想使用此状态数据重新创建对象，并继续update()它。最后，我想获得hexdigest()累计数据的总和。状态持久性必须在多次运行中保持不变。
例子：
import hashlib
m = hashlib.sha1()
m.update('one')
m.update('two')
# somehow, persist the state of m here
#later, possibly in another process
# recreate m from the persisted state
m.update('three')
m.update('four')
print m.hexdigest()
# at this point, m.hexdigest() should be equal to hashlib.sha1().update('onetwothreefour').hextdigest()
编辑：
2010 年，我没有找到使用 python 实现此目的的好方法，最终用 C 语言编写了一个小型辅助应用程序来实现此目的。然而，下面有一些我当时无法获得或不知道的很好的答案。
您可以使用以下方式做到这一点ctypes，不需要C中的帮助程序应用程序：-
重新散列.py
#! /usr/bin/env python
''' A resumable implementation of SHA-256 using ctypes with the OpenSSL crypto library
Written by PM 2Ring 2014.11.13
'''
from ctypes import *
SHA_LBLOCK = 16
SHA256_DIGEST_LENGTH = 32
class SHA256_CTX(Structure):
_fields_ = [
("h", c_long * 8),
("Nl", c_long),
("Nh", c_long),
("data", c_long * SHA_LBLOCK),
("num", c_uint),
("md_len", c_uint)
]
HashBuffType = c_ubyte * SHA256_DIGEST_LENGTH
#crypto = cdll.LoadLibrary("libcrypto.so")
crypto = cdll.LoadLibrary("libeay32.dll" if os.name == "nt" else "libssl.so")
class sha256(object):
digest_size = SHA256_DIGEST_LENGTH
def __init__(self, datastr=None):
self.ctx = SHA256_CTX()
crypto.SHA256_Init(byref(self.ctx))
if datastr:
self.update(datastr)
def update(self, datastr):
crypto.SHA256_Update(byref(self.ctx), datastr, c_int(len(datastr)))
#Clone the current context
def _copy_ctx(self):
ctx = SHA256_CTX()
pointer(ctx)[0] = self.ctx
return ctx
def copy(self):
other = sha256()
other.ctx = self._copy_ctx()
return other
def digest(self):
#Preserve context in case we get called before hashing is
# really finished, since SHA256_Final() clears the SHA256_CTX
ctx = self._copy_ctx()
hashbuff = HashBuffType()
crypto.SHA256_Final(hashbuff, byref(self.ctx))
self.ctx = ctx
return str(bytearray(hashbuff))
def hexdigest(self):
return self.digest().encode('hex')
#Tests
def main():
import cPickle
import hashlib
data = ("Nobody expects ", "the spammish ", "imposition!")
print "rehash\n"
shaA = sha256(''.join(data))
print shaA.hexdigest()
print repr(shaA.digest())
print "digest size =", shaA.digest_size
print
shaB = sha256()
shaB.update(data[0])
print shaB.hexdigest()
#Test pickling
sha_pickle = cPickle.dumps(shaB, -1)
print "Pickle length:", len(sha_pickle)
shaC = cPickle.loads(sha_pickle)
shaC.update(data[1])
print shaC.hexdigest()
#Test copying. Note that copy can be pickled
shaD = shaC.copy()
shaC.update(data[2])
print shaC.hexdigest()
#Verify against hashlib.sha256()
print "\nhashlib\n"
shaD = hashlib.sha256(''.join(data))
print shaD.hexdigest()
print repr(shaD.digest())
print "digest size =", shaD.digest_size
print
shaE = hashlib.sha256(data[0])
print shaE.hexdigest()
shaE.update(data[1])
print shaE.hexdigest()
#Test copying. Note that hashlib copy can NOT be pickled
shaF = shaE.copy()
shaF.update(data[2])
print shaF.hexdigest()
if __name__ == '__main__':
main()
可恢复_SHA-256.py
#! /usr/bin/env python
''' Resumable SHA-256 hash for large files using the OpenSSL crypto library
The hashing process may be interrupted by Control-C (SIGINT) or SIGTERM.
When a signal is received, hashing continues until the end of the
current chunk, then the current file position, total file size, and
the sha object is saved to a file. The name of this file is formed by
appending '.hash' to the name of the file being hashed.
Just re-run the program to resume hashing. The '.hash' file will be deleted
once hashing is completed.
Written by PM 2Ring 2014.11.14
'''
import cPickle as pickle
import os
import signal
import sys
import rehash
quit = False
blocksize = 1<<16 # 64kB
blocksperchunk = 1<<8
chunksize = blocksize * blocksperchunk
def handler(signum, frame):
global quit
print "\nGot signal %d, cleaning up." % signum
quit = True
def do_hash(fname, filesize):
hashname = fname + '.hash'
if os.path.exists(hashname):
with open(hashname, 'rb') as f:
pos, fsize, sha = pickle.load(f)
if fsize != filesize:
print "Error: file size of '%s' doesn't match size recorded in '%s'" % (fname, hashname)
print "%d != %d. Aborting" % (fsize, filesize)
exit(1)
else:
pos, fsize, sha = 0, filesize, rehash.sha256()
finished = False
with open(fname, 'rb') as f:
f.seek(pos)
while not (quit or finished):
for _ in xrange(blocksperchunk):
block = f.read(blocksize)
if block == '':
finished = True
break
sha.update(block)
pos += chunksize
sys.stderr.write(" %6.2f%% of %d\r" % (100.0 * pos / fsize, fsize))
if finished or quit:
break
if quit:
with open(hashname, 'wb') as f:
pickle.dump((pos, fsize, sha), f, -1)
elif os.path.exists(hashname):
os.remove(hashname)
return (not quit), pos, sha.hexdigest()
def main():
if len(sys.argv) != 2:
print "Resumable SHA-256 hash of a file."
print "Usage:\npython %s filename\n" % sys.argv[0]
exit(1)
fname = sys.argv[1]
filesize = os.path.getsize(fname)
signal.signal(signal.SIGINT, handler)
signal.signal(signal.SIGTERM, handler)
finished, pos, hexdigest = do_hash(fname, filesize)
if finished:
print "%s %s" % (hexdigest, fname)
else:
print "sha-256 hash of '%s' incomplete" % fname
print "%s" % hexdigest
print "%d / %d bytes processed." % (pos, filesize)
if __name__ == '__main__':
main()
演示
import rehash
import pickle
sha=rehash.sha256("Hello ")
s=pickle.dumps(sha.ctx)
sha=rehash.sha256()
sha.ctx=pickle.loads(s)
sha.update("World")
print sha.hexdigest()
输出
a591a6d40bf420404a011733cfb7b190d62c65bf0bcda32b57b277d9ad9f146e
注意：我要感谢 PM2Ring 提供的精彩代码。