您可以使用这种方式进行操作，不需要Cctypes中的辅助应用程序：-
rehash.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()
resumable_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 的精彩代码。