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// Base64.cpp: implementation of the CBase64 class.
// Author: Wes Clyburn (clyburnw@enmu.edu)
//
// This code was practically stolen from:
// Dr. Dobb's Journal, September 1995,
// "Mime and Internet Mail", by Tim Kientzle
//////////////////////////////////////////////////////////////////////
#include "stdafx.h"
#include "Base64.h"
#ifdef _DEBUG
#undef THIS_FILE
static char THIS_FILE[]=__FILE__;
#define new DEBUG_NEW
#endif
// Static Member Initializers
//
// The 7-bit alphabet used to encode binary information
CString CBase64::m_sBase64Alphabet =
_T( "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" );
int CBase64::m_nMask[] = { 0, 1, 3, 7, 15, 31, 63, 127, 255 };
//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////
CBase64::CBase64()
{
}
CBase64::~CBase64()
{
}
CString CBase64::Encode(LPCTSTR szEncoding, int nSize)
{
CString sOutput = _T( "" );
int nNumBits = 6;
UINT nDigit;
int lp = 0;
ASSERT( szEncoding != NULL );
if( szEncoding == NULL )
return sOutput;
m_szInput = szEncoding;
m_nInputSize = nSize;
m_nBitsRemaining = 0;
nDigit = read_bits( nNumBits, &nNumBits, lp );
while( nNumBits > 0 )
{
sOutput += m_sBase64Alphabet[ (int)nDigit ];
nDigit = read_bits( nNumBits, &nNumBits, lp );
}
// Pad with '=' as per RFC 1521
while( sOutput.GetLength() % 4 != 0 )
{
sOutput += '=';
}
return sOutput;
}
// The size of the output buffer must not be less than
// 3/4 the size of the input buffer. For simplicity,
// make them the same size.
int CBase64::Decode(LPCTSTR szDecoding, LPTSTR szOutput)
{
CString sInput;
int c, lp =0;
int nDigit;
int nDecode[ 256 ];
ASSERT( szDecoding != NULL );
ASSERT( szOutput != NULL );
if( szOutput == NULL )
return 0;
if( szDecoding == NULL )
return 0;
sInput = szDecoding;
if( sInput.GetLength() == 0 )
return 0;
// Build Decode Table
//
for( int i = 0; i < 256; i++ )
nDecode[i] = -2; // Illegal digit
for( i=0; i < 64; i++ )
{
nDecode[ m_sBase64Alphabet[ i ] ] = i;
nDecode[ m_sBase64Alphabet[ i ] | 0x80 ] = i; // Ignore 8th bit
nDecode[ '=' ] = -1;
nDecode[ '=' | 0x80 ] = -1; // Ignore MIME padding char
}
// Clear the output buffer
memset( szOutput, 0, sInput.GetLength() + 1 );
// Decode the Input
//
for( lp = 0, i = 0; lp < sInput.GetLength(); lp++ )
{
c = sInput[ lp ];
nDigit = nDecode[ c & 0x7F ];
if( nDigit < -1 )
{
return 0;
}
else if( nDigit >= 0 )
// i (index into output) is incremented by write_bits()
write_bits( nDigit & 0x3F, 6, szOutput, i );
}
return i;
}
UINT CBase64::read_bits(int nNumBits, int * pBitsRead, int& lp)
{
ULONG lScratch;
while( ( m_nBitsRemaining < nNumBits ) &&
( lp < m_nInputSize ) )
{
int c = m_szInput[ lp++ ];
m_lBitStorage <<= 8;
m_lBitStorage |= (c & 0xff);
m_nBitsRemaining += 8;
}
if( m_nBitsRemaining < nNumBits )
{
lScratch = m_lBitStorage << ( nNumBits - m_nBitsRemaining );
*pBitsRead = m_nBitsRemaining;
m_nBitsRemaining = 0;
}
else
{
lScratch = m_lBitStorage >> ( m_nBitsRemaining - nNumBits );
*pBitsRead = nNumBits;
m_nBitsRemaining -= nNumBits;
}
return (UINT)lScratch & m_nMask[nNumBits];
}
void CBase64::write_bits(UINT nBits,
int nNumBits,
LPTSTR szOutput,
int& i)
{
UINT nScratch;
m_lBitStorage = (m_lBitStorage << nNumBits) | nBits;
m_nBitsRemaining += nNumBits;
while( m_nBitsRemaining > 7 )
{
nScratch = m_lBitStorage >> (m_nBitsRemaining - 8);
szOutput[ i++ ] = nScratch & 0xFF;
m_nBitsRemaining -= 8;
}
}
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