B64Encoder.m

// Copyright (C) 2012 LMIT Limited
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and 
// limitations under the License.

#import "B64Encoder.h"

static char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789"
"+/";

int b64encode(unsigned s_len, char *src, unsigned d_len, char *dst)
{
    unsigned triad;
	
    for (triad = 0; triad < s_len; triad += 3)
    {
		unsigned long int sr=0;
		unsigned byte=0;
		
		for (byte = 0; (byte<3)&&(triad+byte<s_len); ++byte)
		{
			sr <<= 8;
			sr |= (*(src+triad+byte) & 0xff);
		}
		
		sr <<= (6-((8*byte)%6))%6; /*shift left to next 6bit alignment*/
		
		if (d_len < 4) return 1; /* error - dest too short */
		
		*(dst+0) = *(dst+1) = *(dst+2) = *(dst+3) = '=';
		switch(byte)
		{
			case 3:
				*(dst+3) = base64[sr&0x3f];
				sr >>= 6;
			case 2:
				*(dst+2) = base64[sr&0x3f];
				sr >>= 6;
			case 1:
				*(dst+1) = base64[sr&0x3f];
				sr >>= 6;
				*(dst+0) = base64[sr&0x3f];
		}
		dst += 4; d_len -= 4;
    }
	
    return 0;
	
}