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/*
Weborf
Copyright (C) 2007-2016 Salvo "LtWorf" Tomaselli
Weborf 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 of the License, or
(at your option) any later version.
This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
@author Salvo "LtWorf" Tomaselli <tiposchi@tiscali.it>
*/
#include "options.h"
#include <stdlib.h>
#include <stdio.h>
#include "base64.h"
/**
Returns the base64 (6bit) code of a char
*/
static char getCode(char c) {
if ('A' <=c && c<='Z') {
return c-'A';
} else if ('a' <=c && c<='z') {
return c-'a'+26;
} else if ('0' <=c && c<='9') {
return c-'0'+52;
} else if (c=='+')
return 62;
else if(c=='/')
return 63;
return 0;
}
/**
Decodes a group of 4 characters and put 3 resulting chars in res
res buffer must be able to contain 3 bytes.
*/
void decode4_64(char *res, char *group) {
///////CALCULATE CHAR 0
res[0] = getCode(group[0]) << 2;
char t = getCode(group[1]);
char t1 = t;
t >>= 4;
res[0] = res[0] | t; //Completed 1st char
///////CALCULATE CHAR 1
res[1] = t1 << 4;
t = getCode(group[2]);
t1 = t;
res[1] = res[1] | (t >> 2);
//CALCULATE CHAR 2
res[2] = t1 << 6;
t = getCode(group[3]);
res[2] = res[2] | t;
}
/**
Decodes a base64 string, putting the result inside the result buffer.
Terminates with a \0 the buffer, so string functions can be used on the result.
Doesn't change the encoded string.
result's length must be at least: (strlen(encoded) /4 *3 )+1
*/
void decode64(char *result, char *encoded) {
char *res = result;
while (encoded[0] != 0) {
decode4_64(res, encoded);
encoded += 4;
res += 3;
res[0] = 0;
}
}
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