PipeSys

PipeSys (said Pipes) is a very basic system of pipes implemented in PHP.

Requirements

• PHP >= 5.5

How it works

The way PipeSys works is by having a chain of commands which are joined together by the Scheduler to give the effect of pipes by chaining the output of one to the input of another. A Scheduler can have many commands added to it and all must follow the OutputInterface.

Commands are special classes which have a doCommand method which should return a Generator, i.e. it should have yield statements in it. When a command wants to read it should use a coroutine call like:

$input = (yield new ReadIntent);

By yielding a ReadIntent object the command tells the Scheduler that it wants to read to continue. When data is available for the command it it sent using the send() generator method. $input will pick up this sent value and the generator will continue.

When a command wants to write it should yield the line:

yield $line;

The line should be a single line of text, with a platform dependant newline on the end. (PHP_EOL)

Commands at the start or end have access to the stdin or stdout respectively of the Scheduler which may correspond to the stdin and stdout of the system. (Provided by the StdIn and StdOut classes.)

The Scheduler uses coöperative scheduling, because PHP is single process and single threaded there is no way to implement preëmptive scheduling.

When a stdin method is exhausted it should return an EOF object.The EOF signals that the end of the stream (EOF = End Of File) has been reached. Commands that read will most likely want to return once receiving this as they can't continue any further without anything to read.

Example Code

Examples of simple command chains are shown below.

ChattyYes is similar to the Unix Yes command except instead of y being output it outputs:

Yes
I
Am
Chatty

over and over.

ChattyYes | head

The above chain shows that ChattyYes is connected to stdIn and its output is connected to head which will print the first 10 lines it receives.

The PHP code for this is below:

use ElvenSpellmaker\PipeSys as PS;
use ElvenSpellmaker\PipeSys\Command as Command;

$s = new PS\Scheduler( new PS\IO\StdIn, new PS\IO\StdOut );
$s->addCommand( new Command\ChattyYes );
$s->addCommand( new Command\Head );
$s->run();

Output:
Yes
I
Am
Chatty
Yes
I
Am
Chatty
Yes
I

ChattyYes | grep "Chatty" | head

The above chain shows that ChattyYes is connected to stdIn and it outputs to grep which is looking for the phrase "Chatty" and its output is connected to head which will print the first 10 lines it receives.

The PHP code for this is below:

use ElvenSpellmaker\PipeSys as PS;
use ElvenSpellmaker\PipeSys\Command as Command;

$s = new PS\Scheduler( new PS\IO\StdIn, new PS\IO\StdOut );
$s->addCommand( new Command\ChattyYes );
$s->addCommand( new Command\Grep( 'Chatty' ) );
$s->addCommand( new Command\Head );
$s->run();

Output:
Chatty
Chatty
Chatty
Chatty
Chatty
Chatty
Chatty
Chatty
Chatty
Chatty