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|
#!/usr/bin/env perl
# a very basic and imprecise time quantizer
use strict;
use warnings;
use Getopt::Std qw{getopts};
use Time::HiRes qw{usleep gettimeofday tv_interval};
# be sure to flush right away!
$| = 1;
# arguments
my %flags;
getopts('s', \%flags);
my $ms = ($ARGV[0]? $ARGV[0]: 1);
my $dlen = length(pack("d", ()));
# parser
sub parser()
{
while(<STDIN>)
{
my $v = pack("d", ($_ + 0));
syswrite(FD, $v, $dlen);
}
}
# quantizer
sub quantize()
{
my $res = $ms;
my $cum = 0;
my $num = 0;
# prepare fds
my $fds = '';
vec($fds, fileno(STDIN), 1) = 1;
while($fds)
{
# select
my $pre = [gettimeofday];
my $rfs = $fds;
my $n = select($rfs, undef, undef, $res);
$res -= tv_interval($pre, [gettimeofday]);
# return values
if($n > 0)
{
my $v;
if(!sysread(STDIN, $v, $dlen)) {
$fds = undef;
} else {
++$num;
$cum += unpack("d", $v);
}
}
# average
if($res <= 0)
{
my $v = ($flags{s}? $cum: ($num? $cum / $num: 0));
syswrite(STDOUT, pack("d", $v), $dlen);
# we should rather compensate than drift
$num = $cum = 0;
$res += $ms;
}
}
}
# execution
my $pid = open(FD, "|-");
die unless(defined($pid));
if($pid) {
parser();
} else {
quantize();
}
|
