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1# -*- coding: utf-8 -*-
2#
3# Util/py3compat.py : Compatibility code for handling Py3k / Python 2.x
4#
5# Written in 2010 by Thorsten Behrens
6#
7# ===================================================================
8# The contents of this file are dedicated to the public domain. To
9# the extent that dedication to the public domain is not available,
10# everyone is granted a worldwide, perpetual, royalty-free,
11# non-exclusive license to exercise all rights associated with the
12# contents of this file for any purpose whatsoever.
13# No rights are reserved.
14#
15# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22# SOFTWARE.
23# ===================================================================
25"""Compatibility code for handling string/bytes changes from Python 2.x to Py3k
27In Python 2.x, strings (of type ''str'') contain binary data, including encoded
28Unicode text (e.g. UTF-8). The separate type ''unicode'' holds Unicode text.
29Unicode literals are specified via the u'...' prefix. Indexing or slicing
30either type always produces a string of the same type as the original.
31Data read from a file is always of '''str'' type.
33In Python 3.x, strings (type ''str'') may only contain Unicode text. The u'...'
34prefix and the ''unicode'' type are now redundant. A new type (called
35''bytes'') has to be used for binary data (including any particular
36''encoding'' of a string). The b'...' prefix allows one to specify a binary
37literal. Indexing or slicing a string produces another string. Slicing a byte
38string produces another byte string, but the indexing operation produces an
39integer. Data read from a file is of '''str'' type if the file was opened in
40text mode, or of ''bytes'' type otherwise.
42Since PyCrypto aims at supporting both Python 2.x and 3.x, the following helper
43functions are used to keep the rest of the library as independent as possible
44from the actual Python version.
46In general, the code should always deal with binary strings, and use integers
47instead of 1-byte character strings.
49b(s)
50 Take a text string literal (with no prefix or with u'...' prefix) and
51 make a byte string.
52bchr(c)
53 Take an integer and make a 1-character byte string.
54bord(c)
55 Take the result of indexing on a byte string and make an integer.
56tobytes(s)
57 Take a text string, a byte string, or a sequence of character taken from
58 a byte string and make a byte string.
59"""
61import sys
62import abc
65if sys.version_info[0] == 2:
66 def b(s):
67 return s
68 def bchr(s):
69 return chr(s)
70 def bstr(s):
71 return str(s)
72 def bord(s):
73 return ord(s)
74 def tobytes(s, encoding="latin-1"):
75 if isinstance(s, unicode):
76 return s.encode(encoding)
77 elif isinstance(s, str):
78 return s
79 elif isinstance(s, bytearray):
80 return bytes(s)
81 elif isinstance(s, memoryview):
82 return s.tobytes()
83 else:
84 return ''.join(s)
85 def tostr(bs):
86 return bs
87 def byte_string(s):
88 return isinstance(s, str)
90 # In Python 2, a memoryview does not support concatenation
91 def concat_buffers(a, b):
92 if isinstance(a, memoryview):
93 a = a.tobytes()
94 if isinstance(b, memoryview):
95 b = b.tobytes()
96 return a + b
98 from StringIO import StringIO
99 BytesIO = StringIO
101 from sys import maxint
103 iter_range = xrange
105 def is_native_int(x):
106 return isinstance(x, (int, long))
108 def is_string(x):
109 return isinstance(x, basestring)
111 def is_bytes(x):
112 return isinstance(x, str) or \
113 isinstance(x, bytearray) or \
114 isinstance(x, memoryview)
116 ABC = abc.ABCMeta('ABC', (object,), {'__slots__': ()})
118 FileNotFoundError = IOError
120else:
121 def b(s):
122 return s.encode("latin-1") # utf-8 would cause some side-effects we don't want
123 def bchr(s):
124 return bytes([s])
125 def bstr(s):
126 if isinstance(s,str):
127 return bytes(s,"latin-1")
128 else:
129 return bytes(s)
130 def bord(s):
131 return s
132 def tobytes(s, encoding="latin-1"):
133 if isinstance(s, bytes):
134 return s
135 elif isinstance(s, bytearray):
136 return bytes(s)
137 elif isinstance(s,str):
138 return s.encode(encoding)
139 elif isinstance(s, memoryview):
140 return s.tobytes()
141 else:
142 return bytes([s])
143 def tostr(bs):
144 return bs.decode("latin-1")
145 def byte_string(s):
146 return isinstance(s, bytes)
148 def concat_buffers(a, b):
149 return a + b
151 from io import BytesIO
152 from io import StringIO
153 from sys import maxsize as maxint
155 iter_range = range
157 def is_native_int(x):
158 return isinstance(x, int)
160 def is_string(x):
161 return isinstance(x, str)
163 def is_bytes(x):
164 return isinstance(x, bytes) or \
165 isinstance(x, bytearray) or \
166 isinstance(x, memoryview)
168 from abc import ABC
170 FileNotFoundError = FileNotFoundError
173def _copy_bytes(start, end, seq):
174 """Return an immutable copy of a sequence (byte string, byte array, memoryview)
175 in a certain interval [start:seq]"""
177 if isinstance(seq, memoryview):
178 return seq[start:end].tobytes()
179 elif isinstance(seq, bytearray):
180 return bytes(seq[start:end])
181 else:
182 return seq[start:end]
184del sys
185del abc