import os
import sys
from time import sleep

class HalfBakedMutex:
    def __init__(self):
        import mmap
        #C is an array of people waiting for a ticket
        self.C = mmap.mmap(-1, 1024,
                                  mmap.MAP_SHARED|mmap.MAP_ANONYMOUS)
        #N is list of tickets people are holding
        self.N = mmap.mmap(-1, 1024,
                           mmap.MAP_SHARED|mmap.MAP_ANONYMOUS)

    def take_a_number(self):
        #pick a number to "see the baker"
        i = os.getpid() % 1024

        #find current maximum number
        while True:
            #indicate we are currently getting a number
            self.C[i] = chr(1)

            max = 0
            for j in range(1024):
                if (ord(self.N[j])) > max:
                    max = ord(self.N[j])
            #we can't have max > 256 as chr(256) will fail
            if (max + 1 < 256):
                break
            else:
                self.C[i] = chr(0)
                sleep(0.1)

        #take next maximum
        self.N[i] = chr(max + 1)
        self.C[i] = chr(0)

    def lock(self):

        #first, take a number to see the baker
        self.take_a_number()

        i = os.getpid() % 1024

        for j in range(1024):
            #make sure the process isn't currently getting a ticket
            while ord(self.C[j]) == 1:
                sleep(0.1)
                continue

            # If process j has a ticket, i.e.
            #    N[j] > 0
            # AND either the process has a lower ticket, or the same
            # ticket and a lower PID, i.e.
            #   (N[j],j) < (N[i],i)
            # wait for it to run
            while (ord(self.N[j]) > 0) and (ord(self.N[j]),j) < (ord(self.N[i]),i) :
                sleep(0.1)
                continue

        #if we made it here, it is our turn to run!
        return

    def unlock(self):
        i = os.getpid() % 1024
        self.N[i] = chr(0)


mut = HalfBakedMutex()

os.fork()
os.fork() # 4 processes
os.fork() # 8 processes
os.fork() # 16 processes
os.fork() # 32 processes
os.fork() # 64 processes

while True:
    mut.lock()
    print(" ------ " + `os.getpid()` + " ------ ")
    mut.unlock()