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# Python modules
import os
import sys
PY_MAJOR_VERSION = sys.version_info[0]
# hashlib is only available in Python >= 2.5. I still want to support
# older Pythons so I import md5 if hashlib is not available. Fortunately
# md5 can masquerade as hashlib for my purposes.
try:
import hashlib
except ImportError:
import md5 as hashlib
# 3rd party modules
import sysv_ipc
# Utils for this demo
import utils
if PY_MAJOR_VERSION > 2:
import utils_for_3 as flex_utils
else:
import utils_for_2 as flex_utils
utils.say("Oooo 'ello, I'm Mrs. Conclusion!")
params = utils.read_params()
semaphore = sysv_ipc.Semaphore(params["KEY"])
memory = sysv_ipc.SharedMemory(params["KEY"])
utils.say("memory attached at %d" % memory.address)
what_i_wrote = ""
s = ""
for i in range(0, params["ITERATIONS"]):
utils.say("i = %d" % i)
if not params["LIVE_DANGEROUSLY"]:
# Wait for Mrs. Premise to free up the semaphore.
utils.say("acquiring the semaphore...")
semaphore.acquire()
s = utils.read_from_memory(memory)
while s == what_i_wrote:
if not params["LIVE_DANGEROUSLY"]:
# Release the semaphore...
utils.say("releasing the semaphore")
semaphore.release()
# ...and wait for it to become available again.
utils.say("acquiring for the semaphore...")
semaphore.acquire()
s = utils.read_from_memory(memory)
if what_i_wrote:
if PY_MAJOR_VERSION > 2:
what_i_wrote = what_i_wrote.encode()
try:
assert(s == hashlib.md5(what_i_wrote).hexdigest())
except AssertionError:
flex_utils.raise_error(AssertionError,
"Shared memory corruption after %d iterations." % i)
if PY_MAJOR_VERSION > 2:
s = s.encode()
what_i_wrote = hashlib.md5(s).hexdigest()
utils.write_to_memory(memory, what_i_wrote)
if not params["LIVE_DANGEROUSLY"]:
utils.say("releasing the semaphore")
semaphore.release()
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