1# Copyright 2005 Ben Escoto
2#
3# This file is part of rdiff-backup.
4#
5# rdiff-backup is free software; you can redistribute it and/or modify
6# under the terms of the GNU General Public License as published by the
7# Free Software Foundation; either version 2 of the License, or (at your
8# option) any later version.
9#
10# rdiff-backup is distributed in the hope that it will be useful, but
11# WITHOUT ANY WARRANTY; without even the implied warranty of
12# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13# General Public License for more details.
14#
15# You should have received a copy of the GNU General Public License
16# along with rdiff-backup; if not, write to the Free Software
17# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
18# 02110-1301, USA
19"""Contains a file wrapper that returns a hash on close"""
20
21import hashlib
22from . import Globals
23
24
25class FileWrapper:
26    """Wrapper around a file-like object
27
28    Only use this with files that will be read through in a single
29    pass and then closed.  (There is no seek().)  When you close it,
30    return value will be a Report.
31
32    Currently this just calculates a sha1sum of the datastream.
33
34    """
35
36    def __init__(self, fileobj):
37        self.fileobj = fileobj
38        self.sha1 = hashlib.sha1()
39        self.closed = 0
40
41    def read(self, length=-1):
42        assert not self.closed
43        buf = self.fileobj.read(length)
44        self.sha1.update(buf)
45        return buf
46
47    def close(self):
48        return Report(self.fileobj.close(), self.sha1.hexdigest())
49
50
51class Report:
52    """Hold final information about a byte stream"""
53
54    def __init__(self, close_val, sha1_digest):
55        # FIXME this is a strange construct because it looks like the fileobj
56        # wrapped in a FileWrapper already returns a Report as closing value,
57        # which we can't wrap again in a Report, so we only check that the
58        # hash values do fit.
59        if isinstance(close_val, Report):
60            assert close_val.sha1_digest == sha1_digest, \
61                "Hashes from return code %s and given %s don't match" % \
62                (close_val.sha1_digest, sha1_digest)
63        else:
64            assert not close_val, "Return code %s of type %s isn't null" % \
65                (close_val, type(close_val))
66        self.sha1_digest = sha1_digest
67
68
69def compute_sha1(rp, compressed=0):
70    """Return the hex sha1 hash of given rpath"""
71    assert rp.conn is Globals.local_connection  # inefficient not to do locally
72    digest = compute_sha1_fp(rp.open("rb", compressed))
73    rp.set_sha1(digest)
74    return digest
75
76
77def compute_sha1_fp(fp, compressed=0):
78    """Return hex sha1 hash of given file-like object"""
79    blocksize = Globals.blocksize
80    fw = FileWrapper(fp)
81    while 1:
82        if not fw.read(blocksize):
83            break
84    return fw.close().sha1_digest
85