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/*
* Copyright (C) 2013 Patrick "P. J." McDermott
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this program. If not, see
* <http://www.gnu.org/licenses/>.
*/
#include "base64.h"
static void
base64_decode_block(const char *src, char *dest)
{
int i;
/* GCC's SSP won't wrap functions with arrays smaller than 8 bytes. */
char buf[8];
/* Convert base 64 characters into values. */
/* Supports ASCII and EBCDIC systems. */
for (i = 0; i < 4; ++i) {
if (src[i] >= 'A' && src[i] <= 'I') {
buf[i] = src[i] - 'A' + 0;
} else if (src[i] >= 'J' && src[i] <= 'R') {
buf[i] = src[i] - 'J' + 9;
} else if (src[i] >= 'S' && src[i] <= 'Z') {
buf[i] = src[i] - 'S' + 18;
} else if (src[i] >= 'a' && src[i] <= 'i') {
buf[i] = src[i] - 'a' + 26;
} else if (src[i] >= 'j' && src[i] <= 'r') {
buf[i] = src[i] - 'j' + 35;
} else if (src[i] >= 's' && src[i] <= 'z') {
buf[i] = src[i] - 's' + 44;
} else if (src[i] >= '0' && src[i] <= '9') {
buf[i] = src[i] - '0' + 52;
} else if (src[i] == '+') {
buf[i] = 62;
} else if (src[i] == '/') {
buf[i] = 63;
} else {
buf[i] = '\0';
}
}
/* Map four decoded value bytes into three output bytes. */
dest[0] = (buf[0] << 2) | (buf[1] >> 4);
dest[1] = (buf[1] << 4) | (buf[2] >> 2);
dest[2] = (buf[2] << 6) | (buf[3] >> 0);
}
void
base64_decode(const char *src, char *dest, size_t dest_len)
{
size_t i;
/* Decode the input one entire block at a time. */
for (i = 0; i < (dest_len - 1) / 3; ++i) {
if (src[i * 4] == '\0' ||
src[i * 4 + 1] == '\0' ||
src[i * 4 + 2] == '\0' ||
src[i * 4 + 3] == '\0') {
dest[i * 3] = '\0';
break;
}
base64_decode_block(src + i * 4, dest + i * 3);
}
/* Ensure NUL termination. */
dest[dest_len - 1] = '\0';
}
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