mime.h

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//#pragma package(smart_init)


//---------------------------------------------------------------------------
//  4bit binary to char 0-F
char Hex2Chr( unsigned char n )
{
	n &= 0xF;
	if ( n < 10 )
		return ( char )( n + '0' );
	else
		return ( char )( n - 10 + 'A' );
}
//---------------------------------------------------------------------------
//  char 0-F to 4bit binary
unsigned char Chr2Hex( char c )
{
	if ( c >= 'a' && c <= 'z' )  //  it's toupper
		c = c - 'a' + 'A';
	if ( c >= '0' && c <= '9' )
		return ( int )( c - '0' );
	else if ( c >= 'A' && c <= 'F' )
		return ( int )( c - 'A' + 10 );
	else
		return -1;
}
//---------------------------------------------------------------------------
//  Base64 code table
//  0-63 : A-Z(25) a-z(51), 0-9(61), +(62), /(63)
char  Base2Chr( unsigned char n )
{
	n &= 0x3F;
	if ( n < 26 )
		return ( char )( n + 'A' );
	else if ( n < 52 )
		return ( char )( n - 26 + 'a' );
	else if ( n < 62 )
		return ( char )( n - 52 + '0' );
	else if ( n == 62 )
		return '+';
	else
		return '/';
}
//---------------------------------------------------------------------------
unsigned char Chr2Base( char c )
{
	if ( c >= 'A' && c <= 'Z' )
		return ( unsigned char )( c - 'A' );
	else if ( c >= 'a' && c <= 'z' )
		return ( unsigned char )( c - 'a' + 26 );
	else if ( c >= '0' && c <= '9' )
		return ( unsigned char )( c - '0' + 52 );
	else if ( c == '+' )
		return 62;
	else if ( c == '/' )
		return 63;
	else
		return 64;  //  无效字符
}
//---------------------------------------------------------------------------
//  aLen 为 aSrc 的大小， aDest 所指的缓冲区必须至少为 aLen 的 3 倍！！！
//  返回 aDest 的长度
int QPEncode( char * const aDest, const unsigned char * aSrc, int aLen )
{
	char * p = aDest;
	int    i = 0;

	while ( i++ < aLen )
	{
		*p++ = '=';
		*p++ = Hex2Chr( *aSrc >> 4 );
		*p++ = Hex2Chr( *aSrc++ );
	}
	*p = 0;  //  aDest is an ASCIIZ string
	return ( p - aDest );  //  exclude the end of zero
}
//---------------------------------------------------------------------------
//  aDest 所指的缓冲区必须至少为 aSrc 长度的 1/3 ！！！
//  返回 aDest 的长度
int QPDecode( unsigned char * const aDest, const char * aSrc )
{
	unsigned char * p = aDest;
	int             n = strlen( aSrc );
	unsigned char   ch, cl;

	while ( *aSrc )  //  aSrc is an ASCIIZ string
	{
		if ( ( *aSrc == '=' ) && ( n - 2 > 0 ) )
		{
			ch = Chr2Hex( aSrc[1] );
			cl = Chr2Hex( aSrc[2] );
			if ( ( ch == ( unsigned char )-1 ) || ( cl == ( unsigned char )-1 ) )
				*p++ = *aSrc++;
			else
			{
				*p++ = ( ch << 4 ) | cl;
				aSrc += 3;
			}
		}
		else
			*p++ = *aSrc++;
	}
	return ( p - aDest );
}
//---------------------------------------------------------------------------
//  aLen 为 aSrc 的长度， aDest 所指的缓冲区必须至少为 aLen 的 1.33 倍！！！
//  返回 aDest 的长度
int Base64Encode( char * const aDest, const unsigned char * aSrc, int aLen )
{
	char        * p = aDest;
	int           i;
	unsigned char t;

	for ( i = 0; i < aLen; i++ )
	{
		switch ( i % 3 )
		{
		case 0 :
			*p++ = Base2Chr( *aSrc >> 2 );
			t = ( *aSrc++ << 4 ) & 0x3F;
			break;
		case 1 :
			*p++ = Base2Chr( t | ( *aSrc >> 4 ) );
			t = ( *aSrc++ << 2 ) & 0x3F;
			break;
		case 2 :
			*p++ = Base2Chr( t | ( *aSrc >> 6 ) );
			*p++ = Base2Chr( *aSrc++ );
			break;
		}
	}
	if ( aLen % 3 != 0 )
	{
		*p++ = Base2Chr( t );
		if ( aLen % 3 == 1 )
			*p++ = '=';
		*p++ = '=';
	}
	*p = 0;  //  aDest is an ASCIIZ string
	return ( p - aDest );  //  exclude the end of zero
}
//---------------------------------------------------------------------------
//  aDest 所指的缓冲区必须至少为 aSrc 长度的 0.75 倍！！！
//  返回 aDest 的长度
int Base64Decode( unsigned char * const aDest, const char * aSrc )
{
	unsigned char * p = aDest;
	int             i, n = strlen( aSrc );
	unsigned char   c, t;

	for ( i = 0; i < n; i++ )
	{
		if ( *aSrc == '=' )
			break;
		do {
			if ( *aSrc )
				c = Chr2Base( *aSrc++ );
			else
				c = 65;  //  字符串结束
		} while ( c == 64 );  //  跳过无效字符，如回车等
		
		if ( c == 65 )
			break;

		switch ( i % 4 )
		{
		case 0 :
			t = c << 2;
			break;
		case 1 :
			*p++ = ( unsigned char )( t | ( c >> 4 ) );
			t = ( unsigned char )( c << 4 );
			break;
		case 2 :
			*p++ = ( unsigned char )( t | ( c >> 2 ) );
			t = ( unsigned char )( c << 6 );
			break;
		case 3 :
			*p++ = ( unsigned char )( t | c );
			break;
		}
	}
	return ( p - aDest );
}
//---------------------------------------------------------------------------