#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>

struct expanded_key {
  uint32_t l[16], r[16];
};

void __des_setkey(const unsigned char* key, struct expanded_key* ekey);
void __do_des(uint32_t l_in,
              uint32_t r_in,
              uint32_t* l_out,
              uint32_t* r_out,
              uint32_t count,
              uint32_t saltbits,
              const struct expanded_key* ekey);

static struct expanded_key __encrypt_key;

void setkey(const char* key) {
  unsigned char bkey[8];
  int i, j;

  for (i = 0; i < 8; i++) {
    bkey[i] = 0;
    for (j = 7; j >= 0; j--, key++)
      bkey[i] |= (uint32_t)(*key & 1) << j;
  }

  __des_setkey(bkey, &__encrypt_key);
}

void encrypt(char* block, int edflag) {
  struct expanded_key decrypt_key, *key;
  uint32_t b[2];
  int i, j;
  char* p;

  p = block;
  for (i = 0; i < 2; i++) {
    b[i] = 0;
    for (j = 31; j >= 0; j--, p++)
      b[i] |= (uint32_t)(*p & 1) << j;
  }

  key = &__encrypt_key;
  if (edflag) {
    key = &decrypt_key;
    for (i = 0; i < 16; i++) {
      decrypt_key.l[i] = __encrypt_key.l[15 - i];
      decrypt_key.r[i] = __encrypt_key.r[15 - i];
    }
  }

  __do_des(b[0], b[1], b, b + 1, 1, 0, key);

  p = block;
  for (i = 0; i < 2; i++)
    for (j = 31; j >= 0; j--)
      *p++ = b[i] >> j & 1;
}