xxtea.cpp

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#include "xxtea.h"
 
namespace esphome::xxtea {
 
static const uint32_t DELTA = 0x9e3779b9;
#define MX ((((z >> 5) ^ (y << 2)) + ((y >> 3) ^ (z << 4))) ^ ((sum ^ y) + (k[(p ^ e) & 7] ^ z)))
 
void encrypt(uint32_t *v, size_t n, const uint32_t *k) {
  if (n == 0)
    return;
  uint32_t z, y, sum, e;
  size_t p;
  size_t q = 6 + 52 / n;
  sum = 0;
  z = v[n - 1];
  while (q-- != 0) {
    sum += DELTA;
    e = (sum >> 2);
    for (p = 0; p != n - 1; p++) {
      y = v[p + 1];
      z = v[p] += MX;
    }
    y = v[0];
    z = v[n - 1] += MX;
  }
}
 
void decrypt(uint32_t *v, size_t n, const uint32_t *k) {
  if (n == 0)
    return;
  uint32_t z, y, sum, e;
  size_t p;
  size_t q = 6 + 52 / n;
  sum = q * DELTA;
  y = v[0];
  while (q-- != 0) {
    e = (sum >> 2);
    for (p = n - 1; p != 0; p--) {
      z = v[p - 1];
      y = v[p] -= MX;
    }
    z = v[n - 1];
    y = v[0] -= MX;
    sum -= DELTA;
  }
}
 
}  // namespace esphome::xxtea