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author | Legrandin <gooksankoo@hoiptorrow.mailexpire.com> | 2011-12-22 14:57:45 +0100 |
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committer | Legrandin <gooksankoo@hoiptorrow.mailexpire.com> | 2011-12-22 14:57:45 +0100 |
commit | b29a859ba577967a49950570f0b61d227c63ca86 (patch) | |
tree | 3849a375b4c8d7e3b073129b5eeef9ab215a27a3 | |
parent | 114ca5b4d467617489817eee77ed0621665ee362 (diff) | |
download | pycrypto-b29a859ba577967a49950570f0b61d227c63ca86.tar.gz |
Added description of what string helper functions in py3compat.py do.
-rw-r--r-- | lib/Crypto/Util/py3compat.py | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/lib/Crypto/Util/py3compat.py b/lib/Crypto/Util/py3compat.py index 139aa73..34e5224 100644 --- a/lib/Crypto/Util/py3compat.py +++ b/lib/Crypto/Util/py3compat.py @@ -23,6 +23,39 @@ # =================================================================== """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__ = "$Id$" |