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/* This file is part of Ping903
   Copyright (C) 2020 Sergey Poznyakoff
  
   Ping903 is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3, or (at your option)
   any later version.
  
   Ping903 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 General Public License for more details.
  
   You should have received a copy of the GNU General Public License
   along with Ping903.  If not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <stdlib.h>
#include <errno.h>

static char b64tab[] =
  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

int
base64_encode(const unsigned char *input, size_t input_len,
	      unsigned char **output, size_t *output_len)
{
	size_t olen = 4 * (input_len + 2) / 3 + 1;
	unsigned char *out = malloc(olen);

	if (!out)
		return -1;
	*output = out;
	while (input_len >= 3) {
		*out++ = b64tab[input[0] >> 2];
		*out++ = b64tab[((input[0] << 4) & 0x30) | (input[1] >> 4)];
		*out++ = b64tab[((input[1] << 2) & 0x3c) | (input[2] >> 6)];
		*out++ = b64tab[input[2] & 0x3f];
		input_len -= 3;
		input += 3;
	}

	if (input_len > 0) {
		unsigned char c = (input[0] << 4) & 0x30;
		*out++ = b64tab[input[0] >> 2];
		if (input_len > 1)
			c |= input[1] >> 4;
		*out++ = b64tab[c];
		*out++ = (input_len < 2) ?
			        '=' : b64tab[(input[1] << 2) & 0x3c];
		*out++ = '=';
	}
	*output_len = out - *output;
	*out = 0;
	return 0;
}

static int b64val[128] = {
    	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
	-1, 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, -1, -1, -1, -1, -1,
	-1, 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, -1, -1, -1, -1, -1
};

int
base64_decode(const unsigned char *input, size_t input_len,
              unsigned char *output, size_t output_len)
{
	unsigned char *out = output;
#define AC(c) do { if (output_len-- == 0) return -1; *out++ = (c); } while (0)
	
    	if (!out)
        	return -1;

    	do {
        	if (input[0] > 127 || b64val[input[0]] == -1 || 
                    input[1] > 127 || b64val[input[1]] == -1 || 
                    input[2] > 127 || 
                    ((input[2] != '=') && (b64val[input[2]] == -1)) || 
                    input[3] > 127 || 
                    ((input[3] != '=') && (b64val[input[3]] == -1))) {
            		errno = EINVAL;
            		return -1;
        	}
        	AC((b64val[input[0]] << 2) | (b64val[input[1]] >> 4));
        	if (input[2] != '=') {
            		AC(((b64val[input[1]] << 4) & 0xf0) | 
                           (b64val[input[2]] >> 2));
            		if (input[3] != '=')
                		AC(((b64val[input[2]] << 6) & 0xc0) | 
                                    b64val[input[3]]);
        	}
        	input += 4;
        	input_len -= 4;
    	} while (input_len > 0);
    	return out - output;
}

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