base64.c

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/*  Copyright (c) 2006-2007, Philip Busch <broesel@studcs.uni-sb.de>
 *  All rights reserved.
 *
 *  Redistribution and use in source and binary forms, with or without
 *  modification, are permitted provided that the following conditions are met:
 *
 *   - Redistributions of source code must retain the above copyright notice,
 *     this list of conditions and the following disclaimer.
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 *  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 *  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 *  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 *  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 *  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 *  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 *  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 *  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *  POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "base64.h"

#define XX 100

static const char base64_list[] = \
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const int base64_index[256] = {
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,62, XX,XX,XX,63,
    52,53,54,55, 56,57,58,59, 60,61,XX,XX, XX,XX,XX,XX,
    XX, 0, 1, 2,  3, 4, 5, 6,  7, 8, 9,10, 11,12,13,14,
    15,16,17,18, 19,20,21,22, 23,24,25,XX, XX,XX,XX,XX,
    XX,26,27,28, 29,30,31,32, 33,34,35,36, 37,38,39,40,
    41,42,43,44, 45,46,47,48, 49,50,51,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
    XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX, XX,XX,XX,XX,
};

void base64_encode_block(unsigned char out[4], const unsigned char in[3], int len)
{
        out[0] = base64_list[ in[0] >> 2 ];
        out[1] = base64_list[ ((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4) ];
        out[2] = (unsigned char) (len > 1 ? base64_list[ ((in[1] & 0x0f) << 2) | ((in[2] & 0xc0) >> 6) ] : '=');
        out[3] = (unsigned char) (len > 2 ? base64_list[in[2] & 0x3f] : '=');
}

int base64_decode_block(unsigned char out[3], const unsigned char in[4])
{
        int i, numbytes = 3;
        char tmp[4];

        for(i = 3; i >= 0; i--) {
                if(in[i] == '=') {
                        tmp[i] = 0;
                        numbytes = i - 1;
                } else {
                        tmp[i] = base64_index[ (unsigned char)in[i] ];
                }
                
                if(tmp[i] == XX)
                        return(-1);
        }

        out[0] = (unsigned char) (  tmp[0] << 2 | tmp[1] >> 4);
        out[1] = (unsigned char) (  tmp[1] << 4 | tmp[2] >> 2);
        out[2] = (unsigned char) (((tmp[2] << 6) & 0xc0) | tmp[3]);

        return(numbytes);
}

size_t base64_encoded_size(size_t len)
{
        return(((len + 2) / 3) * 4);
}

size_t base64_decoded_size(size_t len)
{
        return((len / 4) * 3);
}

void base64_encode_binary(char *out, const unsigned char *in, size_t len)
{
        int size;
        size_t i = 0;
        
        while(i < len) {
                size = (len-i < 4) ? len-i : 4;
                
                base64_encode_block((unsigned char *)out, in, size);

                out += 4;
                in  += 3;
                i   += 3;
        }

        *out = '\0';
}

int base64_decode_binary(unsigned char *out, const char *in)
{
        size_t len = strlen(in), i = 0;
        int numbytes = 0;

        while(i < len) {
                if((numbytes += base64_decode_block(out, (unsigned char *)in)) < 0)
                        return(-1);

                out += 3;
                in  += 4;
                i   += 4;
        }

        return(numbytes);
}

char *base64_encode(const char *in, size_t size)
{
        char *out;
        size_t outlen;

        if(in == NULL)
                return(NULL);
        
        if(size == 0)
                size = strlen(in);

        outlen = base64_encoded_size(size);

        if((out = (char *)malloc(sizeof(char) * (outlen + 1))) == NULL)
                return(NULL);

        base64_encode_binary(out, (unsigned char *)in, size);

        return(out);
}

char *base64_decode(const char *in)
{
        char *out;
        size_t outlen;
        int numbytes;
        
        outlen = base64_decoded_size(strlen(in));

        if((out = (char *)malloc(sizeof(char) * (outlen + 1))) == NULL)
                return(NULL);

        if((numbytes = base64_decode_binary((unsigned char *)out, in)) < 0) {
                free(out);
                return(NULL);
        }
        
        *(out + numbytes) = '\0';
        
        return(out);
}

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