The Tor Browser / file revision

 <h2>What's that?</h2>

 Simply package enigmail hard work on providing IPC feature in mozilla platform.

 So we are able to launch child proccesses from javascript,

 and in our case, from addon-sdk libraries :)

 <h2>Sample of code:</h2>

   This object allows to start a process, and read/write data to/from it

   using stdin/stdout/stderr streams.

   Usage example:

    const subprocess = require("subprocess");

    var p = subprocess.call({

      command:     '/bin/foo',

      arguments:   ['-v', 'foo'],

      environment: [ "XYZ=abc", "MYVAR=def" ],

      charset: 'UTF-8',

      workdir: '/home/foo',

      //stdin: "some value to write to stdin\nfoobar",

      stdin: function(stdin) {

        stdin.write("some value to write to stdin\nfoobar");

        stdin.close();

      },

      stdout: function(data) {

        dump("got data on stdout:" + data + "\n");

      },

      stderr: function(data) {

        dump("got data on stderr:" + data + "\n");

      },

      done: function(result) {

        dump("process terminated with " + result.exitCode + "\n");

      },

      mergeStderr: false

    });

    p.wait(); // wait for the subprocess to terminate

              // this will block the main thread,

              // only do if you can wait that long

   Description of parameters:

   --------------------------

   Apart from <command>, all arguments are optional.

   command:     either a |nsIFile| object pointing to an executable file or a

               String containing the platform-dependent path to an executable

               file.

   arguments:   optional string array containing the arguments to the command.

   environment: optional string array containing environment variables to pass

                to the command. The array elements must have the form

                "VAR=data". Please note that if environment is defined, it

                replaces any existing environment variables for the subprocess.

   charset:     Output is decoded with given charset and a string is returned.

                If charset is undefined, "UTF-8" is used as default.

                To get binary data, set this to null and the returned string

                is not decoded in any way.

   workdir:     optional; String containing the platform-dependent path to a

                directory to become the current working directory of the subprocess.

   stdin:       optional input data for the process to be passed on standard

                input. stdin can either be a string or a function.

                A |string| gets written to stdin and stdin gets closed;

                A |function| gets passed an object with write and close function.

                Please note that the write() function will return almost immediately;

                data is always written asynchronously on a separate thread.

   stdout:      an optional function that can receive output data from the

                process. The stdout-function is called asynchronously; it can be

                called mutliple times during the execution of a process.

                At a minimum at each occurance of \n or \r.

                Please note that null-characters might need to be escaped

                with something like 'data.replace(/\0/g, "\\0");'.

   stderr:      an optional function that can receive stderr data from the

                process. The stderr-function is called asynchronously; it can be

                called mutliple times during the execution of a process. Please

                note that null-characters might need to be escaped with

                something like 'data.replace(/\0/g, "\\0");'.

                (on windows it only gets called once right now)

   done:        optional function that is called when the process has terminated.

                The exit code from the process available via result.exitCode. If

                stdout is not defined, then the output from stdout is available

                via result.stdout. stderr data is in result.stderr

   mergeStderr: optional boolean value. If true, stderr is merged with stdout;

                no data will be provided to stderr.

   Description of object returned by subprocess.call(...)

   ------------------------------------------------------

   The object returned by subprocess.call offers a few methods that can be

   executed:

   wait():         waits for the subprocess to terminate. It is not required to use

                   wait; done will be called in any case when the subprocess terminated.

   kill(hardKill): kill the subprocess. Any open pipes will be closed and

                   done will be called.

                   hardKill [ignored on Windows]:

                    - false: signal the process terminate (SIGTERM)

                    - true:  kill the process (SIGKILL)

   Other methods in subprocess

   ---------------------------

   registerDebugHandler(functionRef):   register a handler that is called to get

                                        debugging information

   registerLogHandler(functionRef):     register a handler that is called to get error

                                        messages

   example:

      subprocess.registerLogHandler( function(s) { dump(s); } );

 <h2>Credits:</h2>

 All enigmail team working on IPC component.

   The Initial Developer of this code is Jan Gerber.

   Portions created by Jan Gerber <j@mailb.org>,

   Patrick Brunschwig (author of almost all code) <patrick@mozilla-enigmail.org>,

   Ramalingam Saravanan (from enigmail team) <svn@xmlterm.org>