Test in Perl if data is available on Device::SerialPort - linux

I have written a Perl script that reads data from the serial port.
use Device::SerialPort;
$PortObj = new Device::SerialPort ($PortName, $quiet, $lockfile);
$PortObj->read_const_time( 500 ); # timeout waiting for data after 500ms
...
The main loop tries to read data from the serial port:
while ( 1 ) {
( $count, $data ) = $PortObj->read( $frameLength );
process_my_data( $data );
do_something_entirely_different_that_needs_being_done;
}
But rather than having a $PortObj->read time out (which consumes a lot of time), I want to be able to test if data is available in the buffer, so I can speed up the loop:
while ( 1 ) {
if ( test_serial_data_available ) { ( $count, $data ) = $PortObj->read( $frameLength ); }
do_something_entirely_different_that_needs_being_done;
}
Can I test the serial buffer for data availability?
EDIT1: I've been spending this morning rewriting the problem to use serial device as a file handle and reading data works, but it is still blocking the loop. This might open up new options to check for data available in the buffer.
In pseudo-Perl:
use Symbol qw( gensym );
my $handle = gensym();
my $PortObj = tie( *$handle, "Device::SerialPort", $PortName );
while ( 1 ) {
my $frameData;
if ( test_serial_data_available ) { my $readLength = read( $handle , $frameData , $frameLength ); }
do_something_entirely_different_that_needs_being_done;
}
So my question is: What should test_serial_data_available look like?

Since you have a filehandle, you can use select.
select will take an arbitrary number of file descriptors and wait until one of them becomes "ready", where ready is defined by which of the 3 sets select gets contains the filehandle. See perldoc -f select for details.
select accepts a timeout, so if you give it a timeout of 0, it becomes a polling function. So this function will do what you need:
sub poll {
my ($fh) = #_;
my $in = '';
vec($in,fileno($fh),1) = 1;
return select($in,undef,undef,0);
}
# ...
if ( poll($handle) ) { my $readLength = read( $handle , $frameData , $frameLength ); }

Related

Use of global arrays in different threads in perl

Use of global arrays in different threads
I'm going to use Dancer2 and File::Tail to use Tail on the web. So when the Websocket is opened, it stores the $conn in an array, and when File::Tail is detected, it tries to send data to the socket stored in the array. But it doesn't work as expected.
The array that is saved when a websocket connection occurs is probably not a global variable.
# it doesn't works.
foreach (#webs) {
$_->send_utf8("test2!!!!!!!!");
}
I tried to use threads::shared and Cache:::Memcached etc, but I failed.
I don't know perl very well. I tried to solve it myself, but I couldn't solve it for too long, so I leave a question.
This is the whole code.
use File::Tail ();
use threads;
use threads::shared;
use Net::WebSocket::Server;
use strict;
use Dancer2;
my #webs = ();
# my %clients :shared = ();
my $conns :shared = 4;
threads->create(sub {
print "start-end:", "$conns", "\n";
my #files = glob( $ARGV[0] . '/*' );
my #fs = ();
foreach my $fileName(#files) {
my $file = File::Tail->new(name=>"$fileName",
tail => 1000,
maxinterval=>1,
interval=>1,
adjustafter=>5,resetafter=>1,
ignore_nonexistant=>1,
maxbuf=>32768);
push(#fs, $file);
}
do {
my $timeout = 1;
(my $nfound,my $timeleft,my #pending)=
File::Tail::select(undef,undef,undef,$timeout,#fs);
unless ($nfound) {
} else {
foreach (#pending) {
my $str = $_->read;
print $_->{"input"} . " ||||||||| ".localtime(time)." ||||||||| ".$str;
# it doesn't works.
foreach (#webs) {
$_->send_utf8("test!!!!!!!!");
}
}
}
} until(0);
})->detach();
threads->create(sub {
Net::WebSocket::Server->new(
listen => 8080,
on_connect => sub {
my ($serv, $conn) = #_;
push(#webs, $conn);
$conn->on(
utf8 => sub {
my ($conn, $msg) = #_;
$conn->send_utf8($msg);
# it works.
foreach (#webs) {
$_->send_utf8("test!!!!!!!!");
}
},
);
},
)->start;
})->detach();
get '/' => sub {
my $ws_url = "ws://127.0.0.1:8080/";
return <<"END";
<html>
<head><script>
var urlMySocket = "$ws_url";
var mySocket = new WebSocket(urlMySocket);
mySocket.onmessage = function (evt) {
console.log( "Got message " + evt.data );
};
mySocket.onopen = function(evt) {
console.log("opening");
setTimeout( function() {
mySocket.send('hello'); }, 2000 );
};
</script></head>
<body><h1>WebSocket client</h1></body>
</html>
END
};
dance;
Threads in perl are not lightweight. They're separate instances of the program.
The only thing that threads have in common, are things that exist prior to the threads instantating.
You can - with declaring shared variables - allow data structures to share between threads, however I'd warn you to be cautious here - without some manner of locking, you potentially create yourself a race condition.
In your case, you could declare #webs as : shared. This will mean values inserted into it will be visible to all your threads. But you still need a degree of caution there, because 'when stuff is added' is still nondeterministic.
But anyway, this basically works:
#!/usr/bin/env perl
use strict;
use warnings;
use threads;
use threads::shared;
use Data::Dumper;
my #shared_struct : shared;
sub reader {
print "Starting reader\n";
for ( 1..10 ) {
print threads -> self() -> tid(), ":", join (",", #shared_struct ), "\n";
sleep 1;
}
}
sub writer {
print "starting writer\n";
for ( 1..10 ) {
push #shared_struct, rand(10);
print Dumper \#shared_struct;
sleep 1;
}
}
## start the threads;
my $reader = threads -> create ( \&reader );
my $writer = threads -> create ( \&writer );
while ( 1 ) {
print #shared_struct;
sleep 1;
}
More generally, I'd suggest you almost never actually want to detach a thread in perl - in doing so, what you're saying is 'I don't care about your execution'. And clearly that's not the case in your code - you're trying to talk to the threads.
Just creating the thread accomplishes what you want - parallel execution and you can have:
for my $thread ( threads -> list ) {
$thread -> join;
}
As and when you're ready for the thread to terminate.

Gdal:Increase dimensions (Resolution) of image obtained after using createcopy()

I am using visual c++ gdal to read .gis file from my desktop and then output the image of that file (png/jpeg). The code accepts the "input.gis" file and then creates "output.png".
Here is my working code :
GDALDriver *poDriver;
GDALDataset *poDataset;
char **papszMetadata;
double adfGeoTransform[6];
int nBlockXSize, nBlockYSize;
int bGotMin, bGotMax;
double adfMinMax[2];
GDALAllRegister();
poDataset = (GDALDataset *) GDALOpen("C:\\input.gis", GA_ReadOnly );
if( poDataset == NULL )
{
MessageBox::Show("cannot open");
}
else
{
poDataset->GetGeoTransform( adfGeoTransform );
GDALRasterBand *poBand;
poBand = poDataset->GetRasterBand( 1 );
float *pafScanline;
int nXSize = poBand->GetXSize();
poBand->GetBlockSize( &nBlockXSize, &nBlockYSize );
adfMinMax[0] = poBand->GetMinimum( &bGotMin );
adfMinMax[1] = poBand->GetMaximum( &bGotMax );
if( ! (bGotMin && bGotMax) )
GDALComputeRasterMinMax((GDALRasterBandH)poBand, TRUE, adfMinMax);
poDriver = GetGDALDriverManager()->GetDriverByName("PNG");
if( poDriver == NULL )
printf("Cannot create image");
else
{
papszMetadata = poDriver->GetMetadata();
if( CSLFetchBoolean( papszMetadata, GDAL_DCAP_CREATECOPY, FALSE ) )
{
printf( "Driver %s supports CreateCopy() method.\n", "png" );
}
}
GDALDataset *poDstDS;
poDstDS = poDriver->CreateCopy( "C:\\output.png", poDataset, FALSE, NULL, NULL, NULL );
if( poDstDS != NULL )
GDALClose( (GDALDatasetH) poDstDS );
GDALClose( (GDALDatasetH) poDataset );
}
My problem is when I use createcopy() function from gdal the size of image output is always 99 X 99 (which i guess is the default size). How can I increase the size of image to be outputted for example (512 x 512 )?
The dimensions of your output dataset output.png are 99 x 99 because those are also the dimensions of your input dataset input.gis. To create a new dataset with different dimensions you need to use the Create method as described in the GDAL tutorial.
The PNG driver unfortunately does not support this method which leaves you with two options:
Choose a different output format which supports the Create method.
Use the Create method to create a dataset in your memory and then use CreateCopy on it - as suggestested in this GIS.SE post

Change thread priority ERROR_INVALID_HANDLE

I'm trying to change a thread priority within my script, without success, here are the details.
$thr = threads->new(\&someFunction,
$shared variable 1,
$shared variable 2,
);
I've tried using threads::State;
$thr->priority(2);
Without success
So, I thought the Win32::API must work
my $functionGetLastError= Win32::API->new('Kernel32',
'GetLastError',
'',
'N'
);
my $functionSetThreadPriority= Win32::API->new('Kernel32',
'SetThreadPriority',
'II', # I've tried 'PI' and 'II' as well
'N'
);
my $h = $thr->_handle();
my $success = $functionSetThreadPriority->Call( $h, 2 );
warn "Return Error #".$functionGetLastError->Call() if !$success;
Again, without success: (, but now I have a clue, the script return error number
last Error 6
From MSDN site, System Error Codes (0-499), it seems that the error is
ERROR_INVALID_HANDLE
What am I doing wrong?
$thread->_handle weirdly returns a HANDLE*, while SetThreadPriority expects a HANDLE. You need to dereference the pointer, which you can do as follows:
use constant THREAD_PRIORITY_HIGHEST => 2;
sub SetThreadPriority {
my ($thread, $priority) = #_;
# $thread->_handle() returns a HANDLE*.
my $handle_ptr = $thread->_handle();
my $packed_handle = unpack('P'.HANDLE_SIZE, pack(PTR_FORMAT, $handle_ptr));
my $handle = unpack(HANDLE_FORMAT, $packed_handle);
state $SetThreadPriority = (
Win32::API->new('Kernel32', 'SetThreadPriority', 'Ni', 'i')
or die("Loading SetThreadPriority: $^E\n")
);
return $SetThreadPriority->Call($handle, $priority);
}
Here's the full test program:
use strict;
use warnings;
use feature qw( say state );
use threads;
use threads::shared;
use Carp qw( croak );
use Config qw( %Config );
use Win32::API qw( );
sub uint_format {
$_[0] == 4 ? 'L'
: $_[0] == 8 ? 'Q'
: croak("Unsupported")
}
use constant PTR_SIZE => $Config{ptrsize};
use constant PTR_FORMAT => uint_format(PTR_SIZE);
use constant HANDLE_SIZE => PTR_SIZE;
use constant HANDLE_FORMAT => PTR_FORMAT;
use constant THREAD_PRIORITY_HIGHEST => 2;
sub SetThreadPriority {
my ($thread, $priority) = #_;
# $thread->_handle() returns a HANDLE*.
my $handle_ptr = $thread->_handle();
my $packed_handle = unpack('P'.HANDLE_SIZE, pack(PTR_FORMAT, $handle_ptr));
my $handle = unpack(HANDLE_FORMAT, $packed_handle);
state $SetThreadPriority = (
Win32::API->new('Kernel32', 'SetThreadPriority', 'Ni', 'i')
or die("Loading SetThreadPriority: $^E\n")
);
return $SetThreadPriority->Call($handle, $priority);
}
{
my $done :shared = 0;
my $thread = async {
{ lock($done); cond_wait($done) while !$done; }
};
my $rv = SetThreadPriority($thread, THREAD_PRIORITY_HIGHEST);
say $rv ? "Success" : "Error: $^E";
{ lock($done); $done = 1; cond_broadcast($done); }
$thread->join();
}
Notice that you can use $^E to access GetLastError.
SetThreadPriority($handle, THREAD_PRIORITY_HIGHEST)
or die("SetThreadPriority: $^E\n";
ERROR_INVALID_HANDLE
Which suggests that what _handle returns is not something Win32::API understands. I suspect "P" wants a string buffer not an integer-casted pointer. "I" may be the wrong thing because it's the wrong size on 64-bit, I would try "N" myself.
Also, for future readers running into this issue on Unix: try my POSIX::RT::Scheduler module.

Is there a thread-safe way to print in Perl?

I currently have a script that kicks off threads to perform various actions on several directories. A snippet of my script is:
#main
sub BuildInit {
my $actionStr = "";
my $compStr = "";
my #component_dirs;
my #compToBeBuilt;
foreach my $comp (#compList) {
#component_dirs = GetDirs($comp); #populates #component_dirs
}
print "Printing Action List: #actionList\n";
#---------------------------------------
#---- Setup Worker Threads ----------
for ( 1 .. NUM_WORKERS ) {
async {
while ( defined( my $job = $q->dequeue() ) ) {
worker($job);
}
};
}
#-----------------------------------
#---- Enqueue The Work ----------
for my $action (#actionList) {
my $sem = Thread::Semaphore->new(0);
$q->enqueue( [ $_, $action, $sem ] ) for #component_dirs;
$sem->down( scalar #component_dirs );
print "\n------>> Waiting for prior actions to finish up... <<------\n";
}
# Nothing more to do - notify the Queue that we're not adding anything else
$q->end();
$_->join() for threads->list();
return 0;
}
#worker
sub worker {
my ($job) = #_;
my ( $component, $action, $sem ) = #$job;
Build( $component, $action );
$sem->up();
}
#builder method
sub Build {
my ( $comp, $action ) = #_;
my $cmd = "$MAKE $MAKE_INVOCATION_PATH/$comp ";
my $retCode = -1;
given ($action) {
when ("depend") { $cmd .= "$action >nul 2>&1" } #suppress output
when ("clean") { $cmd .= $action }
when ("build") { $cmd .= 'l1' }
when ("link") { $cmd .= '' } #add nothing; default is to link
default { die "Action: $action is unknown to me." }
}
print "\n\t\t*** Performing Action: \'$cmd\' on $comp ***" if $verbose;
if ( $action eq "link" ) {
# hack around potential race conditions -- will only be an issue during linking
my $tries = 1;
until ( $retCode == 0 or $tries == 0 ) {
last if ( $retCode = system($cmd) ) == 2; #compile error; stop trying
$tries--;
}
}
else {
$retCode = system($cmd);
}
push( #retCodes, ( $retCode >> 8 ) );
#testing
if ( $retCode != 0 ) {
print "\n\t\t*** ERROR IN $comp: $# !! ***\n";
print "\t\t*** Action: $cmd -->> Error Level: " . ( $retCode >> 8 ) . "\n";
#exit(-1);
}
return $retCode;
}
The print statement I'd like to be thread-safe is: print "\n\t\t*** Performing Action: \'$cmd\' on $comp ***" if $verbose; Ideally, I would like to have this output, and then each component that is having the $action performed on it, would output in related chunks. However, this obviously doesn't work right now - the output is interleaved for the most part, with each thread spitting out it's own information.
E.g.,:
ComponentAFile1.cpp
ComponentAFile2.cpp
ComponentAFile3.cpp
ComponentBFile1.cpp
ComponentCFile1.cpp
ComponentBFile2.cpp
ComponentCFile2.cpp
ComponentCFile3.cpp
... etc.
I considered executing the system commands using backticks, and capturing all of the output in a big string or something, then output it all at once, when the thread terminates. But the issue with this is (a) it seems super inefficient, and (b) I need to capture stderr.
Can anyone see a way to keep my output for each thread separate?
clarification:
My desired output would be:
ComponentAFile1.cpp
ComponentAFile2.cpp
ComponentAFile3.cpp
------------------- #some separator
ComponentBFile1.cpp
ComponentBFile2.cpp
------------------- #some separator
ComponentCFile1.cpp
ComponentCFile2.cpp
ComponentCFile3.cpp
... etc.
To ensure your output isn't interrupted, access to STDOUT and STDERR must be mutually exclusive. That means that between the time a thread starts printing and finishes printing, no other thread can be allowed to print. This can be done using Thread::Semaphore[1].
Capturing the output and printing it all at once allows you to reduce the amount of time a thread holds a lock. If you don't do that, you'll effectively make your system single-threaded system as each thread attempts lock STDOUT and STDERR while one thread runs.
Other options include:
Using a different output file for each thread.
Prepending a job id to each line of output so the output can be sorted later.
In both of those cases, you only need to lock it for a very short time span.
# Once
my $mutex = Thread::Semaphore->new(); # Shared by all threads.
# When you want to print.
$mutex->down();
print ...;
STDOUT->flush();
STDERR->flush();
$mutex->up();
or
# Once
my $mutex = Thread::Semaphore->new(); # Shared by all threads.
STDOUT->autoflush();
STDERR->autoflush();
# When you want to print.
$mutex->down();
print ...;
$mutex->up();
You can utilize the blocking behavior of $sem->down if it attempts to decrease the semaphore counter below zero, as mentioned in perldoc perlthrtut:
If down() attempts to decrement the counter below zero, it blocks
until the counter is large enough.
So here's what one could do:
Initialize a semaphore with counter 1 that is shared across all threads
my $sem = Thread::Semaphore->new( 1 );
Pass a thread counter to worker and Build
for my $thr_counter ( 1 .. NUM_WORKERS ) {
async {
while ( defined( my $job = $q->dequeue() ) ) {
worker( $job, $thr_counter );
}
};
}
sub worker {
my ( $job, $counter ) = #_;
Build( $component, $action, $counter );
}
Go ->down and ->up inside Build (and nowhere else)
sub Build {
my ( $comp, $action, $counter ) = #_;
... # Execute all concurrently-executed code here
$sem->down( 1 << ( $counter -1 ) );
print "\n\t\t*** Performing Action: \'$cmd\' on $comp ***" if $verbose;
# Execute all sequential 'chunks' here
$sem->up( 1 << ( $counter - 1) );
}
By using the thread counter to left-shift the semaphore counter, it guarantees that the threads won't trample on one another:
+-----------+---+---+---+---+
| Thread | 1 | 2 | 3 | 4 |
+-----------+---+---+---+---+
| Semaphore | 1 | 2 | 4 | 8 |
+-----------+---+---+---+---+
I've approached this problem differently in the past, by creating an IO thread, and using that to serialise the file access.
E.g.
my $output_q = Thread::Queue -> new();
sub writer {
open ( my $output_fh, ">", $output_filename );
while ( my $line = $output_q -> dequeue() ) {
print {$output_fh} $line;
}
close ( $output_fh );
}
And within threads, 'print' by:
$output_q -> enqueue ( "text_to_print\n"; );
Either with or without a wrapper - e.g. for timestamping statements if they're going to a log. (You probably want to timestamp when queued, rather than when actually printer).

Perl Queues and Threading

I'm trying to accomplish the following:
Have a thread that reads data from a very large file say about
10GB and push them into the queue. (I do not wish for the queue to
get very large either)
While the buildQueue thread is pushing data to the queue at the same time have
about 5 worker threads de-queue and process data.
I've made an attempt but my other threads are unreachable because of a continuous loop in my buildQueue thread.
My approach may be totally wrong. Thanks for any help, it's much appreciated.
Here's the code for buildQueue:
sub buildQueue {
print "Enter a file name: ";
my $dict_path = <STDIN>;
chomp($dict_path);
open DICT_FILE, $dict_path or die("Sorry, could not open file!");
while (1) {
if (<DICT_FILE>) {
if ($queue->pending() < 100) {
my $query = <DICT_FILE>;
chomp($query);
$queue->enqueue($query);
my $count = $queue->pending();
print "Queue Size: $count Query: $query\n";
}
}
}
}
And as I've expected when this thread gets executed nothing else after will be executed because this thread will not finish.
my $builder = new Thread(&buildQueue);
Since the builder thread will be running for a long time I never get to create worker threads.
Here's the entire code:
#!/usr/bin/perl -w
use strict;
use Thread;
use Thread::Queue;
my $queue = new Thread::Queue();
my #threads;
sub buildQueue {
print "Enter a file name: ";
my $dict_path = <STDIN>;
chomp($dict_path);
open dict_file, $dict_path or die("Sorry, could not open file!");
while (1) {
if (<dict_file>) {
if ($queue->pending() < 100) {
my $query = <dict_file>;
chomp($query);
$queue->enqueue($query);
my $count = $queue->pending();
print "Queue Size: $count Query: $query\n";
}
}
}
}
sub processor {
my $query;
while (1) {
if ($query = $queue->dequeue) {
print "$query\n";
}
}
}
my $builder = new Thread(&buildQueue);
push #threads, new Thread(&processor) for 1..5;
You'll need to mark when you want your threads to exit (via either joinor detach ). The fact that you have infinite loops with no last statements to break out of them is also a problem.
Edit: I also forgot a very important part! Each worker thread will block, waiting for another item to process off of the queue until they get an undef in the queue. Hence why we specifically enqueue undef once for each thread after the queue builder is done.
Try:
#!/usr/bin/perl -w
use strict;
use threads;
use Thread::Queue;
my $queue = new Thread::Queue();
our #threads; #Do you really need our instead of my?
sub buildQueue
{
print "Enter a file name: ";
my $dict_path = <STDIN>;
chomp($dict_path);
#Three-argument open, please!
open my $dict_file, "<",$dict_path or die("Sorry, could not open file!");
while(my $query=<$dict_file>)
{
chomp($query);
while(1)
{ #Wait to see if our queue has < 100 items...
if ($queue->pending() < 100)
{
$queue->enqueue($query);
print "Queue Size: " . $queue->pending . "\n";
last; #This breaks out of the infinite loop
}
}
}
close($dict_file);
foreach(1..5)
{
$queue->enqueue(undef);
}
}
sub processor
{
my $query;
while ($query = $queue->dequeue)
{
print "Thread " . threads->tid . " got $query\n";
}
}
my $builder=threads->create(\&buildQueue);
push #threads,threads->create(\&process) for 1..5;
#Waiting for our threads to finish.
$builder->join;
foreach(#threads)
{
$_->join;
}
The MCE module for Perl loves big files. With MCE, one can chunk many lines at once, slurp a big chunk as a scalar string, or read 1 line at a time. Chunking many lines at once reduces the overhead for IPC.
MCE 1.504 is out now. It provides MCE::Queue with support for child processes including threads. In addition, the 1.5 release comes with 5 models (MCE::Flow, MCE::Grep, MCE::Loop, MCE::Map, and MCE::Stream) which take care of instantiating the MCE instance as well as auto-tuning max_workers and chunk_size. One may override these options btw.
Below, MCE::Loop is used for the demonstration.
use MCE::Loop;
print "Enter a file name: ";
my $dict_path = <STDIN>;
chomp($dict_path);
mce_loop_f {
my ($mce, $chunk_ref, $chunk_id) = #_;
foreach my $line ( #$chunk_ref ) {
chomp $line;
## add your code here to process $line
}
} $dict_path;
If you want to specify the number of workers and/or chunk_size, then there are 2 ways to do it.
use MCE::Loop max_workers => 5, chunk_size => 300000;
Or...
use MCE::Loop;
MCE::Loop::init {
max_workers => 5,
chunk_size => 300000
};
Although chunking is preferred for large files, one can compare the time with chunking one line at a time. One may omit the first line inside the block (commented out). Notice how there's no need for an inner for loop. $chunk_ref is still an array ref containing 1 line. The input scalar $_ contains the line when chunk_size equals 1, otherwise points to $chunk_ref.
use MCE::Loop;
MCE::Loop::init {
max_workers => 5,
chunk_size => 1
};
print "Enter a file name: ";
my $dict_path = <STDIN>;
chomp($dict_path);
mce_loop_f {
# my ($mce, $chunk_ref, $chunk_id) = #_;
my $line = $_;
## add your code here to process $line or $_
} $dict_path;
I hope that this demonstration was helpful for folks wanting to process a file in parallel.
:) mario
It sounds like this case could do with the Parallel::ForkManager module.
A different approach: You can also use user_tasks in MCE 1.2+ and create two multi-worker multithreading tasks, one task for reading (since it's a big file, you could also benefit from parallel reading while preserving file read seek) and one task for processing, etc.
The code below still uses Thread::Queue to manage your buffer queue.
The buildQueue sub has your queue size control and it pushes the data directly to the manager process' $R_QUEUE since we've used threads, so it has access to the parent's memory space. If you want to use forks instead, you can still access the queue through a call back function. But here I chose to simply just push to the queue.
The processQueue sub will simply de-queue whatever is in the queue until there's nothing more pending.
The task_end sub in each task is run only once by the manager process at the end of each task, so we use it to signal a stop to our worker processes.
Obviously, there's a lot of freedom in how you want to chunk your data to the workers, so you can decide upon the size of the chunk or even how to slurp your data in.
#!/usr/bin/env perl
use strict;
use warnings;
use threads;
use threads::shared;
use Thread::Queue;
use MCE;
my $R_QUEUE = Thread::Queue->new;
my $queue_workers = 8;
my $process_workers = 8;
my $chunk_size = 1;
print "Enter a file name: ";
my $input_file = <STDIN>;
chomp($input_file);
sub buildQueue {
my ($self, $chunk_ref, $chunk_id) = #_;
if ($R_QUEUE->pending() < 100) {
$R_QUEUE->enqueue($chunk_ref);
$self->sendto('stdout', "Queue Size: " . $R_QUEUE->pending ."\n");
}
}
sub processQueue {
my $self = shift;
my $wid = $self->wid;
while (my $buff = $R_QUEUE->dequeue) {
$self->sendto('stdout', "Thread " . $wid . " got $$buff");
}
}
my $mce = MCE->new(
input_data => $input_file, # this could be a filepath or a file handle or even a scalar to treat like a file, check the documentation for more details.
chunk_size => $chunk_size,
use_slurpio => 1,
user_tasks => [
{ # queueing task
max_workers => $queue_workers,
user_func => \&buildQueue,
use_threads => 1, # we'll use threads to have access to the parent's variables in shared memory.
task_end => sub { $R_QUEUE->enqueue( (undef) x $process_workers ) } # signal stop to our process workers when they hit the end of the queue. Thanks > Jack Maney!
},
{ # process task
max_workers => $process_workers,
user_func => \&processQueue,
use_threads => 1, # we'll use threads to have access to the parent's variables in shared memory
task_end => sub { print "Finished processing!\n"; }
}
]
);
$mce->run();
exit;

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