Added d64 encoding

Author: hannes-ucsc

src/bd2k/util/d64.py

@@ -0,0 +1,117 @@
+# Copyright (c) 2014 Dominic Tarr
+# Copyright (c) 2015 Hannes Schmidt
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+# and associated documentation files (the "Software"), to deal in the Software without
+# restriction, including without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all copies or
+# substantial portions of the Software.
+#
+# 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.
+
+# Ported from JS found at https://github.com/dominictarr/d64
+
+
+
+class D64( object ):
+    def __init__( self, special_chars ):
+        super( D64, self ).__init__( )
+        self.chars = bytearray( sorted(
+            'PYFGCRLAOEUIDHTNSQJKXBMWVZpyfgcrlaoeuidhtnsqjkxbmwvz1234567890' + special_chars ) )
+        self.codeToIndex = bytearray( 128 )
+        for i in xrange( 64 ):
+            code = self.chars[ i ]
+            self.codeToIndex[ code ] = i
+
+    def encode( self, data ):
+        """
+        >>> encode = standard.encode
+        >>> encode('')
+        ''
+        >>> encode('\\x00')
+        '..'
+        >>> encode('\\x00\\x01')
+        '..3'
+        >>> encode('\\x00\\x01\\x02')
+        '..31'
+        >>> encode('\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07')
+        '..31.kF40VR'
+        """
+        l = len( data )
+        s = bytearray( (l * 4 + 2) / 3 )
+        hang = 0
+        j = 0
+        chars = self.chars
+        for i in xrange( l ):
+            v = ord( data[ i ] )
+            r = i % 3
+            if r == 0:
+                s[ j ] = chars[ v >> 2 ]
+                j += 1
+                hang = (v & 3) << 4
+            elif r == 1:
+                s[ j ] = chars[ hang | v >> 4 ]
+                j += 1
+                hang = (v & 0xf) << 2
+            elif r == 2:
+                s[ j ] = chars[ hang | v >> 6 ]
+                j += 1
+                s[ j ] = chars[ v & 0x3f ]
+                j += 1
+                hang = 0
+            else:
+                assert False
+        if l % 3:
+            s[ j ] = chars[ hang ]
+
+        return str( s )
+
+    def decode( self, s ):
+        """
+        >>> decode = standard.decode
+        >>> decode('')
+        ''
+        >>> decode('..')
+        '\\x00'
+        >>> decode('..3')
+        '\\x00\\x01'
+        >>> decode('..31')
+        '\\x00\\x01\\x02'
+        >>> decode('..31.kF40VR')
+        '\\x00\\x01\\x02\\x03\\x04\\x05\\x06\\x07'
+        """
+        l = len( s )
+        j = 0
+        b = bytearray( l * 3 / 4 )
+        hang = 0
+        codeToIndex = self.codeToIndex
+
+        for i in xrange( l ):
+            v = codeToIndex[ ord( s[ i ] ) ]
+            r = i % 4
+            if r == 0:
+                hang = v << 2
+            elif r == 1:
+                b[ j ] = hang | v >> 4
+                j += 1
+                hang = (v << 4) & 0xFF
+            elif r == 2:
+                b[ j ] = hang | v >> 2
+                j += 1
+                hang = (v << 6) & 0xFF
+            elif r == 3:
+                b[ j ] = hang | v
+                j += 1
+            else:
+                assert False
+        return str( b )
+
+
+standard = D64( '._' )

src/bd2k/util/test/test_d64.py

@@ -0,0 +1,34 @@
+# Copyright (c) 2014 Dominic Tarr
+# Copyright (c) 2015 Hannes Schmidt
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+# and associated documentation files (the "Software"), to deal in the Software without
+# restriction, including without limitation the rights to use, copy, modify, merge, publish,
+# distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the
+# Software is furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all copies or
+# substantial portions of the Software.
+#
+# 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.
+
+# Ported from JS found at https://github.com/dominictarr/d64
+
+from __future__ import absolute_import
+from unittest import TestCase
+from bd2k.util.d64 import standard as d64
+import os
+
+
+class TestD64( TestCase ):
+    def test( self ):
+        data = [ (os.urandom( i ), i) for i in xrange( 1000 ) ]
+        encoded_data = [ (d64.encode( d ), i) for d, i in data ]
+        decoded_data = [ (d64.decode( s ), i) for s, i in encoded_data ]
+        self.assertEqual( data, decoded_data )
+        # Ensure that lexicographical sort is consistent between data and encoded data
+        self.assertEqual( zip( *sorted( data ) )[ 1 ], zip( *sorted( encoded_data ) )[ 1 ] )