125 lines
3.6 KiB
C++
125 lines
3.6 KiB
C++
/*
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----
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This file is part of SECONDO.
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Copyright (C) 2004, University in Hagen, Department of Computer Science,
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Database Systems for New Applications.
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SECONDO is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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SECONDO is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with SECONDO; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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----
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//characters [1] verbatim: [\verb@] [@]
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1 Base64, a class for encoding binary data to text and vice versa.
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December 08, M. Spiekermann: Initial Version
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This class provides member functions used for encoding and decoding the ~base64~
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data format as specified in RFC 1341. The interface was designed to interact
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kindly with the text atoms of nested lists. The nested list parser recognizes a
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file name enclosed in the tag-pair "<file>"[1],"</file--->" and translates it to
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a text atom containing the data of the file encoded into base64 format. The
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base64 data maps 24 bits of input to 4 letters into an alphabet of 64
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characters. Thus the encoded data grows to 4/3 (not exactly, since newlines are
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added every 72 bytes) of the original size and the decoded Size shrinks to less
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than 3/4 since newlines and unknown characters are ignored.
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*/
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#ifndef CLASS_BASE64_H
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#define CLASS_BASE64_H
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#include <string>
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#include <math.h>
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class Base64{
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public:
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Base64(char newline='\n');
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~Base64(){};
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int sizeDecoded(int letters) {
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return (int)ceil( (3*(double)letters)/4 );
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}
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int sizeEncoded(int bytes) {
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return ( (int)ceil( 4*(double)bytes/3 )
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+ (int)ceil( 4*(double)bytes/(3*72) ) );
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}
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/*
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These functions calculate the decoded or encoded size for a given
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number of bytes. This is useful for allocating buffers.
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1.1 Encoding and Decoding
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*/
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void encode(const char* bytes, int size, std::string& base64);
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/*
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Encodes the bytes contained in the buffer ~bytes~ of size ~size~ into base64
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format written into the string ~base64~.
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*/
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int decode(const std::string& text, char* bytes);
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/*
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Decodes the base64 data stored in ~text~ and returns the number of bytes written
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into the buffer ~bytes~ which has to be allocated by the caller. The size of the
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buffer can be estimated by the function sizeDecoded().
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*/
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void decodeStream(std::istream& in, std::ostream& out);
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void encodeStream(std::istream& in, std::ostream& out);
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/*
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Encode or decode a stream of base64 characters or bytes.
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*/
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private:
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/* buffers, note that a single base64 instance is not thread savem,
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but several instances can be used in parallel.
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*/
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std::string newline;
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char inbuffer[5];
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char outbuffer[3];
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char resultbuffer[73];
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/* the characters used in the base64 format */
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static char base64Alphabet[];
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/* internal helper functions */
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unsigned int getIndex(char b);
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bool isAllowed(char b);
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/* these functions implement the encoding logic */
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void encode2(const char* buffer, std::string& text, int size);
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bool getNext(char& byte, std::istream& in);
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/* status and position information*/
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bool endReached;
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int currentPos;
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int filled;
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int Pos;
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void init();
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};
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#endif
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