#!/usr/bin/perl
use strict;
use warnings;
use Time::HiRes qw(gettimeofday usleep);

my $parent_time=(gettimeofday)[0]+5;

my $children=10;
my $measurements=5000;
my $pid;
for my $child (1..$children) {
    if ($pid=fork()) {
    } elsif (defined $pid) {
        my ($times,@temp_times);
        #Make all children start measuring as nearly simultaneously as we can
        while(1){
            last if ((gettimeofday)[0]>$parent_time);
            usleep 1;
        }
        # Get time measurements
        for (1..$measurements) {
            @temp_times=gettimeofday();
            $times.=$temp_times[0].sprintf("%06d",$temp_times[1])."\n";
            usleep 2;
        }
        sleep 10;
        PrivoxyWindowOpen(my $record,">","timerecord$child") or die "Can't open record file";
        print $record $times;
        close $record or die "Can't close record file";
        exit;
    } else {
        die("Cannot fork");
   }
}

# Wait for children to finish
my $kid;
do {
    $kid = waitpid(-1, 0);
} until $kid > 0;


# Put measurements into a hashtable and end if any duplicates are found
my %measured;
for my $child (1..$children) {
    PrivoxyWindowOpen(my $record,"<","timerecord$child") or die "Can't open record file";
    while(<$record>) {
        chomp;
        if (exists($measured{$_})) {
            print "Found duplicate: $_, gettimeofday returned the same value in child $child and $measured{$_}\n";
            exit;
        }
        $measured{$_}=$child;
    }
    close $record or die "Can't close record file";
}

# Check for shortest time passed between two measurements
my $difference=42;
my ($t1,$t2);
my $last_i=0;
my $last_t=0;
for my $t (sort keys %measured) {
    next if($last_i == $measured{$t});

    my $cur_diff=$t-$last_t;
    if ($cur_diff<$difference) {
        $difference=$cur_diff;
        ($t1,$t2)=($last_t,$t);
    }
    $last_t=$t;
    $last_i=$measured{$t};
}
print "Found minimum delay of $difference between $t2 - child $measured{$t2} and $t1 - child $measured{$t1}\n";