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/*
* Copyright (c) 2020, yzrh <yzrh@noema.org>
*
* SPDX-License-Identifier: Apache-2.0
*/
#include "cnki.h"
int
cnki_kdh(cnki_t **param)
{
if (*param == NULL)
return 1;
if ((*param)->stat > 0)
printf("Begin 'KDH' decryption\n");
fseek((*param)->fp_i, 0, SEEK_END);
long size = ftell((*param)->fp_i);
fseek((*param)->fp_i, ADDRESS_KDH_BODY, SEEK_SET);
const char key[] = KEY_KDH;
const int key_len = KEY_KDH_LENGTH;
long key_cur = 0;
char buf[(*param)->size_buf];
for (;;) {
fread(buf, (*param)->size_buf, 1, (*param)->fp_i);
for (int i = 0; i < (*param)->size_buf; i++) {
buf[i] ^= key[key_cur % key_len];
key_cur++;
}
fwrite(buf, (*param)->size_buf, 1, (*param)->fp_o);
if (ftell((*param)->fp_i) == size)
break;
}
if ((*param)->stat > 0)
printf("Decryption ended total %ld byte(s) written\n",
ftell((*param)->fp_o));
return 0;
}
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