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/**
* Arara, the cool TeX automation tool
* Copyright (c) 2012 -- 2018, Paulo Roberto Massa Cereda
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* 3. Neither the name of the project's author nor the names of its
* contributors may be used to endorse or promote products derived from
* this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY
* WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
package com.github.cereda.arara.controller;
import java.util.HashMap;
import java.util.Map;
import org.zeroturnaround.exec.ProcessExecutor;
/**
* Implements a system call controller. This class wraps a map that holds the
* result of system specific variables not directly available at runtime.
* @author Paulo Roberto Massa Cereda
* @version 4.0
* @since 4.0
*/
public class SystemCallController {
/**
* Implements a private command interface.
*/
private interface Command {
/**
* Executes the command body.
* @return An object.
*/
public Object execute();
}
// the controller itself, since we have a singleton;
// this is the reference instance, instantiated once
private static final SystemCallController instance =
new SystemCallController();
// the system call map which holds the result of
// system specific variables not directly available
// at runtime; the idea here is to provide wrappers
// to the map getter, so it could be easily manipulated
private final Map<String, Object> map;
// the commands map will allow the system call map being
// populated only on demand, that is, if the key is not
// found, this map will provide the corresponding method
// and update the value
private final Map<String, Command> commands;
/**
* Private constructor. Called once when the singleton is created.
*/
private SystemCallController() {
// create the new map instance to be
// populated on demand
map = new HashMap<String, Object>();
// create the new map of commands and
// add the corresponding system calls
commands = new HashMap<String, Command>();
// add the check for a Cygwin
// environment in here
commands.put("cygwin", new Command() {
/**
* Implements the body of the command. In this particular
* instance, it checks if we are inside a Cygwin environment.
* @return A boolean value indicating if we are inside a Cygwin
* environment.
*/
public Object execute() {
try {
// execute a new system call to 'uname -s', read the output
// as an UTF-8 string, lowercase it and check if it starts
// with the 'cygwin' string; if so, we are inside Cygwin
return (
new ProcessExecutor().command("uname", "-s").
readOutput(true).execute().outputUTF8()
).toLowerCase().startsWith("cygwin");
} catch (Exception exception) {
// gracefully fallback in case of any nasty and evil
// exception, e.g, if the command is unavailable
return false;
}
}
});
}
/**
* Gets the singleton reference. Since this class is implemented as a
* singleton, you will get the same controller every single time.
* @return The system call controller which holds the system call map.
*/
public static SystemCallController getInstance() {
return instance;
}
/**
* Gets the object indexed by the provided key. This method actually holds
* the map method of the very same name.
* @param key The provided map key.
* @return The object indexed by the provided map key.
*/
public Object get(String key) {
// if key is not found, meaning that
// the value wasn't required before
if (!map.containsKey(key)) {
// perform the system call and
// populate the corresponding value
map.put(key, commands.get(key).execute());
}
// simply return the corresponding
// value based on the provided key
return map.get(key);
}
}
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