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// util/base64.cpp
/**
* Copyright (C) 2008 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "stdafx.h"
namespace mongo {
namespace base64 {
class Alphabet {
public:
Alphabet(){
encode =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789"
"+/";
decode = (char*)malloc(257);
memset( decode , 0 , 256 );
for ( int i=0; i<64; i++ ){
decode[ encode[i] ] = i;
}
test();
}
~Alphabet(){
delete( decode );
}
void test(){
assert( strlen( encode ) == 64 );
for ( int i=0; i<26; i++ )
assert( encode[i] == toupper( encode[i+26] ) );
}
char e( int x ){
return encode[x&0x3f];
}
private:
const char * encode;
public:
char * decode;
} alphabet;
void encode( stringstream& ss , const char * data , int size ){
for ( int i=0; i<size; i+=3 ){
int left = size - i;
const char * start = data + i;
// byte 0
ss << alphabet.e(start[0]>>2);
// byte 1
char temp = ( start[0] << 4 );
if ( left == 1 ){
ss << alphabet.e(temp);
break;
}
temp |= ( ( start[1] >> 4 ) & 0xF );
ss << alphabet.e(temp);
// byte 2
temp = ( start[1] & 0xF ) << 2;
if ( left == 2 ){
ss << alphabet.e(temp);
break;
}
temp |= ( ( start[2] >> 6 ) & 0x3 );
ss << alphabet.e(temp);
// byte 3
ss << alphabet.e(start[2] & 0x3f);
}
int mod = size % 3;
if ( mod == 1 ){
ss << "==";
}
else if ( mod == 2 ){
ss << "=";
}
}
string encode( const char * data , int size ){
stringstream ss;
encode( ss , data ,size );
return ss.str();
}
string encode( const string& s ){
return encode( s.c_str() , s.size() );
}
void decode( stringstream& ss , const string& s ){
uassert( "invalid base64" , s.size() % 4 == 0 );
const char * data = s.c_str();
int size = s.size();
char buf[3];
for ( int i=0; i<size; i+=4){
const char * start = data + i;
buf[0] = ( ( alphabet.decode[start[0]] << 2 ) & 0xFC ) | ( ( alphabet.decode[start[1]] >> 4 ) & 0x3 );
buf[1] = ( ( alphabet.decode[start[1]] << 4 ) & 0xF0 ) | ( ( alphabet.decode[start[2]] >> 2 ) & 0xF );
buf[2] = ( ( alphabet.decode[start[2]] << 6 ) & 0xC0 ) | ( ( alphabet.decode[start[3]] & 0x3F ) );
int len = 3;
if ( start[3] == '=' ){
len = 2;
if ( start[2] == '=' ){
len = 1;
}
}
ss.write( buf , len );
}
}
string decode( const string& s ){
stringstream ss;
decode( ss , s );
return ss.str();
}
}
}
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