basic functionalty

modules/Crypto/Util/py3compat.py

@@ -0,0 +1,117 @@
+# -*- coding: utf-8 -*-
+#
+#  Util/py3compat.py : Compatibility code for handling Py3k / Python 2.x
+#
+# Written in 2010 by Thorsten Behrens
+#
+# ===================================================================
+# The contents of this file are dedicated to the public domain.  To
+# the extent that dedication to the public domain is not available,
+# everyone is granted a worldwide, perpetual, royalty-free,
+# non-exclusive license to exercise all rights associated with the
+# contents of this file for any purpose whatsoever.
+# No rights are reserved.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
+# BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+# ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+# ===================================================================
+
+"""Compatibility code for handling string/bytes changes from Python 2.x to Py3k
+
+In Python 2.x, strings (of type ''str'') contain binary data, including encoded
+Unicode text (e.g. UTF-8).  The separate type ''unicode'' holds Unicode text.
+Unicode literals are specified via the u'...' prefix.  Indexing or slicing
+either type always produces a string of the same type as the original.
+Data read from a file is always of '''str'' type.
+
+In Python 3.x, strings (type ''str'') may only contain Unicode text. The u'...'
+prefix and the ''unicode'' type are now redundant.  A new type (called
+''bytes'') has to be used for binary data (including any particular
+''encoding'' of a string).  The b'...' prefix allows one to specify a binary
+literal.  Indexing or slicing a string produces another string.  Slicing a byte
+string produces another byte string, but the indexing operation produces an
+integer.  Data read from a file is of '''str'' type if the file was opened in
+text mode, or of ''bytes'' type otherwise.
+
+Since PyCrypto aims at supporting both Python 2.x and 3.x, the following helper
+functions are used to keep the rest of the library as independent as possible
+from the actual Python version.
+
+In general, the code should always deal with binary strings, and use integers
+instead of 1-byte character strings.
+
+b(s)
+    Take a text string literal (with no prefix or with u'...' prefix) and
+    make a byte string.
+bchr(c)
+    Take an integer and make a 1-character byte string.
+bord(c)
+    Take the result of indexing on a byte string and make an integer.
+tobytes(s)
+    Take a text string, a byte string, or a sequence of character taken from
+    a byte string and make a byte string.
+"""
+
+__revision__ = "$Id$"
+
+import sys
+
+if sys.version_info[0] == 2:
+    def b(s):
+        return s
+    def bchr(s):
+        return chr(s)
+    def bstr(s):
+        return str(s)
+    def bord(s):
+        return ord(s)
+    if sys.version_info[1] == 1:
+        def tobytes(s):
+            try:
+                return s.encode('latin-1')
+            except:
+                return ''.join(s)
+        def tostr(bs):
+            return unicode(bs, 'latin-1')
+    else:
+        def tobytes(s):
+            if isinstance(s, unicode):
+                return s.encode("latin-1")
+            else:
+                return ''.join(s)
+        def tostr(bs):
+            return bs.decode('latin-1')
+    # In Pyton 2.x, StringIO is a stand-alone module
+    from StringIO import StringIO as BytesIO
+else:
+    def b(s):
+       return s.encode("latin-1") # utf-8 would cause some side-effects we don't want
+    def bchr(s):
+        return bytes([s])
+    def bstr(s):
+        if isinstance(s,str):
+            return bytes(s,"latin-1")
+        else:
+            return bytes(s)
+    def bord(s):
+        return s
+    def tobytes(s):
+        if isinstance(s,bytes):
+            return s
+        else:
+            if isinstance(s,str):
+                return s.encode("latin-1")
+            else:
+                return bytes(s)
+    def tostr(bs):
+        return bs.decode("latin-1")
+    # In Pyton 3.x, StringIO is a sub-module of io
+    from io import BytesIO
+ 
+# vim:set ts=4 sw=4 sts=4 expandtab: