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/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
* base64.c
*
* Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
*/
#include "config.h"
#include "internal.h"
static sqfs_u8 convert(char in)
{
if (isupper(in))
return in - 'A';
if (islower(in))
return in - 'a' + 26;
if (isdigit(in))
return in - '0' + 52;
if (in == '+')
return 62;
if (in == '/' || in == '-')
return 63;
return 0;
}
size_t base64_decode(sqfs_u8 *out, const char *in, size_t len)
{
sqfs_u8 *start = out;
while (len > 0) {
unsigned int diff = 0, value = 0;
while (diff < 4 && len > 0) {
if (*in == '=' || *in == '_' || *in == '\0') {
len = 0;
} else {
value = (value << 6) | convert(*(in++));
--len;
++diff;
}
}
if (diff < 2)
break;
value <<= 6 * (4 - diff);
switch (diff) {
case 4: out[2] = value & 0xff; /* fall-through */
case 3: out[1] = (value >> 8) & 0xff; /* fall-through */
default: out[0] = (value >> 16) & 0xff;
}
out += (diff * 3) / 4;
}
*out = '\0';
return out - start;
}
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