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Commit d2457a3e authored by Lorenzo Colitti's avatar Lorenzo Colitti
Browse files

Add a MessageUtils class to convert int constants to strings. 

This class uses reflection to find accessible static integer
members in a specified list of classes and returns a SparseArray
mapping the integers to their names. This will allow us to
replace various 400-line switch statements with a simple
array access.

Change-Id: I3607e6389a423cde0bd83270c00b3c863ae1bb29
parent 0d0f0c7f

core/java/com/android/internal/util/MessageUtils.java

0 → 100644
+127 −0
Original line number Diff line number Diff line 
/*

 * Copyright (C) 2016 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */



package com.android.internal.util;



import android.os.Message;

import android.util.Log;

import android.util.SparseArray;



import java.lang.reflect.Field;



/**

 * Static utility class for dealing with {@link Message} objects.

 */

public class MessageUtils {



    private static final String TAG = MessageUtils.class.getSimpleName();

    private static final boolean DBG = false;



    /** Thrown when two different constants have the same value. */

    public static class DuplicateConstantError extends Error {

        private DuplicateConstantError() {}

        public DuplicateConstantError(String name1, String name2, int value) {

            super(String.format("Duplicate constant value: both %s and %s = %d",

                name1, name2, value));

        }

    }



    /**

     * Finds the names of integer constants. Searches the specified {@code classes}, looking for

     * accessible static integer fields whose names begin with one of the specified {@prefixes}.

     *

     * @param classes the classes to examine.

     * @prefixes only consider fields names starting with one of these prefixes.

     * @return a {@link SparseArray} mapping integer constants to their names.

     */

    public static SparseArray<String> findMessageNames(Class[] classes, String[] prefixes) {

        SparseArray<String> messageNames = new SparseArray<>();

        for (Class c : classes) {

            String className = c.getName();

            if (DBG) Log.d(TAG, "Examining class " + className);



            Field[] fields;

            try {

                fields = c.getDeclaredFields();

            } catch (SecurityException e) {

                Log.e(TAG, "Can't list fields of class " + className);

                continue;

            }



            for (Field field : fields) {

                String name = field.getName();



                for (String prefix : prefixes) {

                    // Does this look like a constant?

                    if (!name.startsWith(prefix)) {

                        continue;

                    }



                    try {

                        // TODO: can we have the caller try to access the field instead, so we don't

                        // expose constants it does not have access to?

                        field.setAccessible(true);



                        // Fetch the constant's value.

                        int value;

                        try {

                            value = field.getInt(null);

                        } catch (IllegalArgumentException | ExceptionInInitializerError e) {

                            // The field is not an integer (or short or byte), or c's static

                            // initializer failed and we have no idea what its value is.

                            // Either way, give up on this field.

                            break;

                        }



                        // Check for duplicate values.

                        String previousName = messageNames.get(value);

                        if (previousName != null && !previousName.equals(name)) {

                            throw new DuplicateConstantError(name, previousName, value);

                        }



                        messageNames.put(value, name);

                        if (DBG) {

                            Log.d(TAG, String.format("Found constant: %s.%s = %d",

                                    className, name, value));

                        }

                    } catch (SecurityException | IllegalAccessException e) {

                        // Not allowed to make the field accessible, or no access. Ignore.

                        continue;

                    }

                }

            }

        }

        return messageNames;

    }



    /**

     * Default prefixes for constants.

     */

    public static final String[] DEFAULT_PREFIXES = {"CMD_", "EVENT_"};



    /**

     * Finds the names of integer constants. Searches the specified {@code classes}, looking for

     * accessible static integer values whose names begin with {@link #DEFAULT_PREFIXES}.

     *

     * @param classNames the classes to examine.

     * @prefixes only consider fields names starting with one of these prefixes.

     * @return a {@link SparseArray} mapping integer constants to their names.

     */

    public static SparseArray<String> findMessageNames(Class[] classNames) {

        return findMessageNames(classNames, DEFAULT_PREFIXES);

    }

}

services/net/java/android/net/dhcp/DhcpClient.java

+8 −27
Original line number Diff line number Diff line
@@ -19,6 +19,7 @@ package android.net.dhcp; 
import com.android.internal.util.HexDump;

import com.android.internal.util.Protocol;

import com.android.internal.util.State;

import com.android.internal.util.MessageUtils;

import com.android.internal.util.StateMachine;



import android.app.AlarmManager;
@@ -34,7 +35,6 @@ import android.net.NetworkUtils; 
import android.os.IBinder;

import android.os.INetworkManagementService;

import android.os.Message;

import android.os.PowerManager;

import android.os.RemoteException;

import android.os.ServiceManager;

import android.os.SystemClock;
@@ -42,16 +42,15 @@ import android.system.ErrnoException; 
import android.system.Os;

import android.system.PacketSocketAddress;

import android.util.Log;

import android.util.SparseArray;

import android.util.TimeUtils;



import java.io.FileDescriptor;

import java.io.IOException;

import java.lang.Thread;

import java.net.Inet4Address;

import java.net.InetSocketAddress;

import java.net.NetworkInterface;

import java.net.SocketException;

import java.nio.BufferUnderflowException;

import java.nio.ByteBuffer;

import java.util.Arrays;

import java.util.Random;
@@ -133,6 +132,11 @@ public class DhcpClient extends StateMachine { 
    private static final int CMD_TIMEOUT          = PRIVATE_BASE + 3;

    private static final int CMD_ONESHOT_TIMEOUT  = PRIVATE_BASE + 4;



    // For message logging.

    private static final Class[] sMessageClasses = { DhcpClient.class };

    private static final SparseArray<String> sMessageNames =

            MessageUtils.findMessageNames(sMessageClasses);



    // DHCP parameters that we request.

    private static final byte[] REQUESTED_PARAMS = new byte[] {

        DHCP_SUBNET_MASK,
@@ -497,30 +501,7 @@ public class DhcpClient extends StateMachine { 
        }



        private String messageName(int what) {

            switch (what) {

                case CMD_START_DHCP:

                    return "CMD_START_DHCP";

                case CMD_STOP_DHCP:

                    return "CMD_STOP_DHCP";

                case CMD_RENEW_DHCP:

                    return "CMD_RENEW_DHCP";

                case CMD_PRE_DHCP_ACTION:

                    return "CMD_PRE_DHCP_ACTION";

                case CMD_PRE_DHCP_ACTION_COMPLETE:

                    return "CMD_PRE_DHCP_ACTION_COMPLETE";

                case CMD_POST_DHCP_ACTION:

                    return "CMD_POST_DHCP_ACTION";

                case CMD_KICK:

                    return "CMD_KICK";

                case CMD_RECEIVED_PACKET:

                    return "CMD_RECEIVED_PACKET";

                case CMD_TIMEOUT:

                    return "CMD_TIMEOUT";

                case CMD_ONESHOT_TIMEOUT:

                    return "CMD_ONESHOT_TIMEOUT";

                default:

                    return Integer.toString(what);

            }

            return sMessageNames.get(what, Integer.toString(what));

        }



        private String messageToString(Message message) {

services/net/java/android/net/ip/IpManager.java

+9 −20
Original line number Diff line number Diff line
@@ -16,6 +16,8 @@ 


package android.net.ip;



import com.android.internal.util.MessageUtils;



import android.content.Context;

import android.net.DhcpResults;

import android.net.InterfaceConfiguration;
@@ -30,6 +32,7 @@ import android.os.Message; 
import android.os.RemoteException;

import android.os.ServiceManager;

import android.util.Log;

import android.util.SparseArray;



import com.android.internal.annotations.GuardedBy;

import com.android.internal.annotations.VisibleForTesting;
@@ -61,6 +64,11 @@ public class IpManager extends StateMachine { 
    private static final boolean DBG = true;

    private static final boolean VDBG = false;



    // For message logging.

    private static final Class[] sMessageClasses = { IpManager.class, DhcpClient.class };

    private static final SparseArray<String> sWhatToString =

            MessageUtils.findMessageNames(sMessageClasses);



    /**

     * Callbacks for handling IpManager events.

     */
@@ -306,26 +314,7 @@ public class IpManager extends StateMachine { 


    @Override

    protected String getWhatToString(int what) {

        // TODO: Investigate switching to reflection.

        switch (what) {

            case CMD_STOP:

                return "CMD_STOP";

            case CMD_START:

                return "CMD_START";

            case CMD_CONFIRM:

                return "CMD_CONFIRM";

            case EVENT_PRE_DHCP_ACTION_COMPLETE:

                return "EVENT_PRE_DHCP_ACTION_COMPLETE";

            case EVENT_NETLINK_LINKPROPERTIES_CHANGED:

                return "EVENT_NETLINK_LINKPROPERTIES_CHANGED";

            case DhcpClient.CMD_PRE_DHCP_ACTION:

                return "DhcpClient.CMD_PRE_DHCP_ACTION";

            case DhcpClient.CMD_POST_DHCP_ACTION:

                return "DhcpClient.CMD_POST_DHCP_ACTION";

            case DhcpClient.CMD_ON_QUIT:

                return "DhcpClient.CMD_ON_QUIT";

        }

        return "UNKNOWN:" + Integer.toString(what);

        return sWhatToString.get(what, "UNKNOWN: " + Integer.toString(what));

    }



    @Override