mutate_bytearray.py

# test concurrent mutating access to a shared bytearray object
#
# MIT license; Copyright (c) 2016 Damien P. George on behalf of Pycom Ltd

import _thread

# the shared bytearray
ba = bytearray()


# main thread function
def th(n, lo, hi):
    for repeat in range(n):
        for i in range(lo, hi):
            l = len(ba)
            ba.append(i)
            assert len(ba) >= l + 1

            l = len(ba)
            ba.extend(bytearray([i]))
            assert len(ba) >= l + 1

    with lock:
        global n_finished
        n_finished += 1


lock = _thread.allocate_lock()
n_thread = 4
n_finished = 0
n_repeat = 4  # use 40 for more stressful test (uses more heap)

# spawn threads
for i in range(n_thread):
    _thread.start_new_thread(th, (n_repeat, i * 256 // n_thread, (i + 1) * 256 // n_thread))

# busy wait for threads to finish
while n_finished < n_thread:
    pass

# check bytearray has correct contents
print(len(ba))
count = [0 for _ in range(256)]
for b in ba:
    count[b] += 1
print(count)