moonlight-android/src/com/limelight/computers/IdentityManager.java

package com.limelight.computers;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.Random;

import com.limelight.LimeLog;

import android.content.Context;

public class IdentityManager {
	private static final String UNIQUE_ID_FILE_NAME = "uniqueid";
	private static final int UID_SIZE_IN_BYTES = 8;
	
	private String uniqueId;
	
	public IdentityManager(Context c) {
		uniqueId = loadUniqueId(c);
		if (uniqueId == null) {
			uniqueId = generateNewUniqueId(c);
		}
		
		LimeLog.info("UID is now: "+uniqueId);
	}
	
	public String getUniqueId() {
		return uniqueId;
	}
	
	private static String loadUniqueId(Context c) {
		// 2 Hex digits per byte
		char[] uid = new char[UID_SIZE_IN_BYTES * 2];
		InputStreamReader reader = null;
		LimeLog.info("Reading UID from disk");
		try {
			reader = new InputStreamReader(c.openFileInput(UNIQUE_ID_FILE_NAME));
			if (reader.read(uid) != UID_SIZE_IN_BYTES * 2)
			{
				LimeLog.severe("UID file data is truncated");
				return null;
			}
			return new String(uid);
		} catch (FileNotFoundException e) {
			LimeLog.info("No UID file found");
			return null;
		} catch (IOException e) {
			LimeLog.severe("Error while reading UID file");
			e.printStackTrace();
			return null;
		} finally {
			if (reader != null) {
				try {
					reader.close();
				} catch (IOException e) {}
			}
		}
	}
	
	private static String generateNewUniqueId(Context c) {
		// Generate a new UID hex string
		LimeLog.info("Generating new UID");
		String uidStr = String.format("%016x", new Random().nextLong());
		
		OutputStreamWriter writer = null;
		try {
			writer = new OutputStreamWriter(c.openFileOutput(UNIQUE_ID_FILE_NAME, 0));
			writer.write(uidStr);
			LimeLog.info("UID written to disk");
		} catch (IOException e) {
			LimeLog.severe("Error while writing UID file");
			e.printStackTrace();
		} finally {
			if (writer != null) {
				try {
					writer.close();
				} catch (IOException e) {}
			}
		}
		
		// We can return a UID even if I/O fails
		return uidStr;
	}
}