#include "sm4_core.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static void rk_crypto_ofb128_encrypt(void *ctx, const unsigned char *in,
                                     unsigned char *out, int len,
                                     unsigned char *ivec, unsigned int *num,
                                     block128_f block) {
  int n, l = 0;

  n = *num;

  while (l < len) {
    if (n == 0) {
      (*block)(ivec, ivec, ctx);
    }
    out[l] = in[l] ^ ivec[n];
    ++l;
    n = (n + 1) % SM4_BLOCK_SIZE;
  }

  *num = n;
}

/* XTS makes use of two different keys, usually generated by splitting
 * the supplied block cipher's key in half.
 * Because of the splitting, users wanting AES 256 and AES 128 encryption
 * will need to choose key sizes of 512 bits and 256 bits respectively.
 */
int rk_sm4_ofb_encrypt(const unsigned char *in, unsigned char *out,
                       unsigned long length, const unsigned char *key,
                       const int key_len, unsigned char *ivec, const int enc) {
  sm4_context ctx;
  unsigned int num = 0;

  if (key_len != 16)
    return -1;

  if (length == 0)
    return -1;

  rk_sm4_setkey_enc(&ctx, key);
  rk_crypto_ofb128_encrypt((void *)&ctx, in, out, length, ivec, &num,
                           rk_rk_sm4_crypt_ecb);
  return 0;
}