text: # Stress test for threads using AES encryption routines.
  #
  # AES was chosen because it is integer based and inplace so doesn't use the
  # heap.  It is therefore a good test of raw performance and correctness of the
  # VM/runtime.  It can be used to measure threading performance (concurrency is
  # in principle possible) and correctness (it's non trivial for the encryption/
  # decryption to give the correct answer).
  #
  # The AES code comes first (code originates from a C version authored by D.P.George)
  # and then the test harness at the bottom.  It can be tuned to be more/less
  # aggressive by changing the amount of data to encrypt, the number of loops and
  # the number of threads.
  #
  # MIT license; Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd
  
  ##################################################################
  # discrete arithmetic routines, mostly from a precomputed table
  
  # non-linear, invertible, substitution box
  # fmt: off
  aes_s_box_table = bytes((
      0x63,0x7c,0x77,0x7b,0xf2,0x6b,0x6f,0xc5,0x30,0x01,0x67,0x2b,0xfe,0xd7,0xab,0x76,
      0xca,0x82,0xc9,0x7d,0xfa,0x59,0x47,0xf0,0xad,0xd4,0xa2,0xaf,0x9c,0xa4,0x72,0xc0,
      0xb7,0xfd,0x93,0x26,0x36,0x3f,0xf7,0xcc,0x34,0xa5,0xe5,0xf1,0x71,0xd8,0x31,0x15,
      0x04,0xc7,0x23,0xc3,0x18,0x96,0x05,0x9a,0x07,0x12,0x80,0xe2,0xeb,0x27,0xb2,0x75,
      0x09,0x83,0x2c,0x1a,0x1b,0x6e,0x5a,0xa0,0x52,0x3b,0xd6,0xb3,0x29,0xe3,0x2f,0x84,
      0x53,0xd1,0x00,0xed,0x20,0xfc,0xb1,0x5b,0x6a,0xcb,0xbe,0x39,0x4a,0x4c,0x58,0xcf,
      0xd0,0xef,0xaa,0xfb,0x43,0x4d,0x33,0x85,0x45,0xf9,0x02,0x7f,0x50,0x3c,0x9f,0xa8,
      0x51,0xa3,0x40,0x8f,0x92,0x9d,0x38,0xf5,0xbc,0xb6,0xda,0x21,0x10,0xff,0xf3,0xd2,
      0xcd,0x0c,0x13,0xec,0x5f,0x97,0x44,0x17,0xc4,0xa7,0x7e,0x3d,0x64,0x5d,0x19,0x73,
      0x60,0x81,0x4f,0xdc,0x22,0x2a,0x90,0x88,0x46,0xee,0xb8,0x14,0xde,0x5e,0x0b,0xdb,
      0xe0,0x32,0x3a,0x0a,0x49,0x06,0x24,0x5c,0xc2,0xd3,0xac,0x62,0x91,0x95,0xe4,0x79,
      0xe7,0xc8,0x37,0x6d,0x8d,0xd5,0x4e,0xa9,0x6c,0x56,0xf4,0xea,0x65,0x7a,0xae,0x08,
      0xba,0x78,0x25,0x2e,0x1c,0xa6,0xb4,0xc6,0xe8,0xdd,0x74,0x1f,0x4b,0xbd,0x8b,0x8a,
      0x70,0x3e,0xb5,0x66,0x48,0x03,0xf6,0x0e,0x61,0x35,0x57,0xb9,0x86,0xc1,0x1d,0x9e,
      0xe1,0xf8,0x98,0x11,0x69,0xd9,0x8e,0x94,0x9b,0x1e,0x87,0xe9,0xce,0x55,0x28,0xdf,
      0x8c,0xa1,0x89,0x0d,0xbf,0xe6,0x42,0x68,0x41,0x99,0x2d,0x0f,0xb0,0x54,0xbb,0x16,
  ))
  # fmt: on
  
  # multiplication of polynomials modulo x^8 + x^4 + x^3 + x + 1 = 0x11b
  def aes_gf8_mul_2(x):
      if x & 0x80:
          return (x << 1) ^ 0x11B
      else:
          return x << 1
  
  
  def aes_gf8_mul_3(x):
      return x ^ aes_gf8_mul_2(x)
  
  
  # non-linear, invertible, substitution box
  def aes_s_box(a):
      return aes_s_box_table[a & 0xFF]
  
  
  # return 0x02^(a-1) in GF(2^8)
  def aes_r_con(a):
      ans = 1
      while a > 1:
          ans <<= 1
          if ans & 0x100:
              ans ^= 0x11B
          a -= 1
      return ans
  
  
  ##################################################################
  # basic AES algorithm; see FIPS-197
  #
  # Think of it as a pseudo random number generator, with each
  # symbol in the sequence being a 16 byte block (the state).  The
  # key is a parameter of the algorithm and tells which particular
  # sequence of random symbols you want.  The initial vector, IV,
  # sets the start of the sequence.  The idea of a strong cipher
  # is that it's very difficult to guess the key even if you know
  # a large part of the sequence.  The basic AES algorithm simply
  # provides such a sequence.  En/de-cryption is implemented here
  # using OCB, where the sequence is xored against the plaintext.
  # Care must be taken to (almost) always choose a different IV.
  
  # all inputs must be size 16
  def aes_add_round_key(state, w):
      for i in range(16):
          state[i] ^= w[i]
  
  
  # combined sub_bytes, shift_rows, mix_columns, add_round_key
  # all inputs must be size 16
  def aes_sb_sr_mc_ark(state, w, w_idx, temp):
      temp_idx = 0
      for i in range(4):
          x0 = aes_s_box_table[state[i * 4]]
          x1 = aes_s_box_table[state[1 + ((i + 1) & 3) * 4]]
          x2 = aes_s_box_table[state[2 + ((i + 2) & 3) * 4]]
          x3 = aes_s_box_table[state[3 + ((i + 3) & 3) * 4]]
          temp[temp_idx] = aes_gf8_mul_2(x0) ^ aes_gf8_mul_3(x1) ^ x2 ^ x3 ^ w[w_idx]
          temp[temp_idx + 1] = x0 ^ aes_gf8_mul_2(x1) ^ aes_gf8_mul_3(x2) ^ x3 ^ w[w_idx + 1]
          temp[temp_idx + 2] = x0 ^ x1 ^ aes_gf8_mul_2(x2) ^ aes_gf8_mul_3(x3) ^ w[w_idx + 2]
          temp[temp_idx + 3] = aes_gf8_mul_3(x0) ^ x1 ^ x2 ^ aes_gf8_mul_2(x3) ^ w[w_idx + 3]
          w_idx += 4
          temp_idx += 4
      for i in range(16):
          state[i] = temp[i]
  
  
  # combined sub_bytes, shift_rows, add_round_key
  # all inputs must be size 16
  def aes_sb_sr_ark(state, w, w_idx, temp):
      temp_idx = 0
      for i in range(4):
          x0 = aes_s_box_table[state[i * 4]]
          x1 = aes_s_box_table[state[1 + ((i + 1) & 3) * 4]]
          x2 = aes_s_box_table[state[2 + ((i + 2) & 3) * 4]]
          x3 = aes_s_box_table[state[3 + ((i + 3) & 3) * 4]]
          temp[temp_idx] = x0 ^ w[w_idx]
          temp[temp_idx + 1] = x1 ^ w[w_idx + 1]
          temp[temp_idx + 2] = x2 ^ w[w_idx + 2]
          temp[temp_idx + 3] = x3 ^ w[w_idx + 3]
          w_idx += 4
          temp_idx += 4
      for i in range(16):
          state[i] = temp[i]
  
  
  # take state as input and change it to the next state in the sequence
  # state and temp have size 16, w has size 16 * (Nr + 1), Nr >= 1
  def aes_state(state, w, temp, nr):
      aes_add_round_key(state, w)
      w_idx = 16
      for i in range(nr - 1):
          aes_sb_sr_mc_ark(state, w, w_idx, temp)
          w_idx += 16
      aes_sb_sr_ark(state, w, w_idx, temp)
  
  
  # expand 'key' to 'w' for use with aes_state
  # key has size 4 * Nk, w has size 16 * (Nr + 1), temp has size 16
  def aes_key_expansion(key, w, temp, nk, nr):
      for i in range(4 * nk):
          w[i] = key[i]
      w_idx = 4 * nk - 4
      for i in range(nk, 4 * (nr + 1)):
          t = temp
          t_idx = 0
          if i % nk == 0:
              t[0] = aes_s_box(w[w_idx + 1]) ^ aes_r_con(i // nk)
              for j in range(1, 4):
                  t[j] = aes_s_box(w[w_idx + (j + 1) % 4])
          elif nk > 6 and i % nk == 4:
              for j in range(0, 4):
                  t[j] = aes_s_box(w[w_idx + j])
          else:
              t = w
              t_idx = w_idx
          w_idx += 4
          for j in range(4):
              w[w_idx + j] = w[w_idx + j - 4 * nk] ^ t[t_idx + j]
  
  
  ##################################################################
  # simple use of AES algorithm, using output feedback (OFB) mode
  
  
  class AES:
      def __init__(self, keysize):
          if keysize == 128:
              self.nk = 4
              self.nr = 10
          elif keysize == 192:
              self.nk = 6
              self.nr = 12
          else:
              assert keysize == 256
              self.nk = 8
              self.nr = 14
  
          self.state = bytearray(16)
          self.w = bytearray(16 * (self.nr + 1))
          self.temp = bytearray(16)
          self.state_pos = 16
  
      def set_key(self, key):
          aes_key_expansion(key, self.w, self.temp, self.nk, self.nr)
          self.state_pos = 16
  
      def set_iv(self, iv):
          for i in range(16):
              self.state[i] = iv[i]
          self.state_pos = 16
  
      def get_some_state(self, n_needed):
          if self.state_pos >= 16:
              aes_state(self.state, self.w, self.temp, self.nr)
              self.state_pos = 0
          n = 16 - self.state_pos
          if n > n_needed:
              n = n_needed
          return n
  
      def apply_to(self, data):
          idx = 0
          n = len(data)
          while n > 0:
              ln = self.get_some_state(n)
              n -= ln
              for i in range(ln):
                  data[idx + i] ^= self.state[self.state_pos + i]
              idx += ln
              self.state_pos += n
  
  
  ##################################################################
  # test code
  
  try:
      import utime as time
  except ImportError:
      import time
  import _thread
  
  
  class LockedCounter:
      def __init__(self):
          self.lock = _thread.allocate_lock()
          self.value = 0
  
      def add(self, val):
          self.lock.acquire()
          self.value += val
          self.lock.release()
  
  
  count = LockedCounter()
  
  
  def thread_entry(n_loop):
      global count
  
      aes = AES(256)
      key = bytearray(256 // 8)
      iv = bytearray(16)
      data = bytearray(128)
      # from now on we don't use the heap
  
      for loop in range(n_loop):
          # encrypt
          aes.set_key(key)
          aes.set_iv(iv)
          for i in range(8):
              aes.apply_to(data)
  
          # decrypt
          aes.set_key(key)
          aes.set_iv(iv)
          for i in range(8):
              aes.apply_to(data)
  
          # verify
          for i in range(len(data)):
              assert data[i] == 0
  
      count.add(1)
  
  
  if __name__ == "__main__":
      import sys
  
      if sys.platform == "rp2":
          n_thread = 1
          n_loop = 2
      elif sys.platform in ("esp32", "pyboard"):
          n_thread = 2
          n_loop = 2
      else:
          n_thread = 20
          n_loop = 5
      for i in range(n_thread):
          _thread.start_new_thread(thread_entry, (n_loop,))
      thread_entry(n_loop)
      while count.value < n_thread:
          time.sleep(1)
      print("done")
  