xref: /frameworks/base/wifi/java/android/net/wifi/WifiManager.java

/*
 * Copyright (C) 2008 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 android.net.wifi;

import android.annotation.SdkConstant;
import android.annotation.SdkConstant.SdkConstantType;
import android.net.DhcpInfo;
import android.os.Binder;
import android.os.IBinder;
import android.os.Handler;
import android.os.RemoteException;

import java.util.List;

/**
 * This class provides the primary API for managing all aspects of Wi-Fi
 * connectivity. Get an instance of this class by calling
 * {@link android.content.Context#getSystemService(String) Context.getSystemService(Context.WIFI_SERVICE)}.

 * It deals with several categories of items:
 * <ul>
 * <li>The list of configured networks. The list can be viewed and updated,
 * and attributes of individual entries can be modified.</li>
 * <li>The currently active Wi-Fi network, if any. Connectivity can be
 * established or torn down, and dynamic information about the state of
 * the network can be queried.</li>
 * <li>Results of access point scans, containing enough information to
 * make decisions about what access point to connect to.</li>
 * <li>It defines the names of various Intent actions that are broadcast
 * upon any sort of change in Wi-Fi state.
 * </ul>
 * This is the API to use when performing Wi-Fi specific operations. To
 * perform operations that pertain to network connectivity at an abstract
 * level, use {@link android.net.ConnectivityManager}.
 */
public class WifiManager {

    // Supplicant error codes:
    /**
     * The error code if there was a problem authenticating.
     */
    public static final int ERROR_AUTHENTICATING = 1;

    /**
     * Broadcast intent action indicating that Wi-Fi has been enabled, disabled,
     * enabling, disabling, or unknown. One extra provides this state as an int.
     * Another extra provides the previous state, if available.
     *
     * @see #EXTRA_WIFI_STATE
     * @see #EXTRA_PREVIOUS_WIFI_STATE
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String WIFI_STATE_CHANGED_ACTION =
        "android.net.wifi.WIFI_STATE_CHANGED";
    /**
     * The lookup key for an int that indicates whether Wi-Fi is enabled,
     * disabled, enabling, disabling, or unknown.  Retrieve it with
     * {@link android.content.Intent#getIntExtra(String,int)}.
     *
     * @see #WIFI_STATE_DISABLED
     * @see #WIFI_STATE_DISABLING
     * @see #WIFI_STATE_ENABLED
     * @see #WIFI_STATE_ENABLING
     * @see #WIFI_STATE_UNKNOWN
     */
    public static final String EXTRA_WIFI_STATE = "wifi_state";
    /**
     * The previous Wi-Fi state.
     *
     * @see #EXTRA_WIFI_STATE
     */
    public static final String EXTRA_PREVIOUS_WIFI_STATE = "previous_wifi_state";

    /**
     * Wi-Fi is currently being disabled. The state will change to {@link #WIFI_STATE_DISABLED} if
     * it finishes successfully.
     *
     * @see #WIFI_STATE_CHANGED_ACTION
     * @see #getWifiState()
     */
    public static final int WIFI_STATE_DISABLING = 0;
    /**
     * Wi-Fi is disabled.
     *
     * @see #WIFI_STATE_CHANGED_ACTION
     * @see #getWifiState()
     */
    public static final int WIFI_STATE_DISABLED = 1;
    /**
     * Wi-Fi is currently being enabled. The state will change to {@link #WIFI_STATE_ENABLED} if
     * it finishes successfully.
     *
     * @see #WIFI_STATE_CHANGED_ACTION
     * @see #getWifiState()
     */
    public static final int WIFI_STATE_ENABLING = 2;
    /**
     * Wi-Fi is enabled.
     *
     * @see #WIFI_STATE_CHANGED_ACTION
     * @see #getWifiState()
     */
    public static final int WIFI_STATE_ENABLED = 3;
    /**
     * Wi-Fi is in an unknown state. This state will occur when an error happens while enabling
     * or disabling.
     *
     * @see #WIFI_STATE_CHANGED_ACTION
     * @see #getWifiState()
     */
    public static final int WIFI_STATE_UNKNOWN = 4;

    /**
     * Broadcast intent action indicating that a connection to the supplicant has
     * been established (and it is now possible
     * to perform Wi-Fi operations) or the connection to the supplicant has been
     * lost. One extra provides the connection state as a boolean, where {@code true}
     * means CONNECTED.
     * @see #EXTRA_SUPPLICANT_CONNECTED
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String SUPPLICANT_CONNECTION_CHANGE_ACTION =
        "android.net.wifi.supplicant.CONNECTION_CHANGE";
    /**
     * The lookup key for a boolean that indicates whether a connection to
     * the supplicant daemon has been gained or lost. {@code true} means
     * a connection now exists.
     * Retrieve it with {@link android.content.Intent#getBooleanExtra(String,boolean)}.
     */
    public static final String EXTRA_SUPPLICANT_CONNECTED = "connected";
    /**
     * Broadcast intent action indicating that the state of Wi-Fi connectivity
     * has changed. One extra provides the new state
     * in the form of a {@link android.net.NetworkInfo} object. If the new state is
     * CONNECTED, a second extra may provide the BSSID of the access point,
     * as a {@code String}.
     * @see #EXTRA_NETWORK_INFO
     * @see #EXTRA_BSSID
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String NETWORK_STATE_CHANGED_ACTION = "android.net.wifi.STATE_CHANGE";
    /**
     * The lookup key for a {@link android.net.NetworkInfo} object associated with the
     * Wi-Fi network. Retrieve with
     * {@link android.content.Intent#getParcelableExtra(String)}.
     */
    public static final String EXTRA_NETWORK_INFO = "networkInfo";
    /**
     * The lookup key for a String giving the BSSID of the access point to which
     * we are connected. Only present when the new state is CONNECTED.
     * Retrieve with
     * {@link android.content.Intent#getStringExtra(String)}.
     */
    public static final String EXTRA_BSSID = "bssid";
    /**
     * Broadcast intent action indicating that the state of establishing a connection to
     * an access point has changed.One extra provides the new
     * {@link SupplicantState}. Note that the supplicant state is Wi-Fi specific, and
     * is not generally the most useful thing to look at if you are just interested in
     * the overall state of connectivity.
     * @see #EXTRA_NEW_STATE
     * @see #EXTRA_SUPPLICANT_ERROR
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String SUPPLICANT_STATE_CHANGED_ACTION =
        "android.net.wifi.supplicant.STATE_CHANGE";
    /**
     * The lookup key for a {@link SupplicantState} describing the new state
     * Retrieve with
     * {@link android.content.Intent#getParcelableExtra(String)}.
     */
    public static final String EXTRA_NEW_STATE = "newState";

    /**
     * The lookup key for a {@link SupplicantState} describing the supplicant
     * error code if any
     * Retrieve with
     * {@link android.content.Intent#getIntExtra(String, int)}.
     * @see #ERROR_AUTHENTICATING
     */
    public static final String EXTRA_SUPPLICANT_ERROR = "supplicantError";

    /**
     * An access point scan has completed, and results are available from the supplicant.
     * Call {@link #getScanResults()} to obtain the results.
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String SCAN_RESULTS_AVAILABLE_ACTION = "android.net.wifi.SCAN_RESULTS";
    /**
     * The RSSI (signal strength) has changed.
     * @see #EXTRA_NEW_RSSI
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String RSSI_CHANGED_ACTION = "android.net.wifi.RSSI_CHANGED";
    /**
     * The lookup key for an {@code int} giving the new RSSI in dBm.
     */
    public static final String EXTRA_NEW_RSSI = "newRssi";

    /**
     * The network IDs of the configured networks could have changed.
     */
    @SdkConstant(SdkConstantType.BROADCAST_INTENT_ACTION)
    public static final String NETWORK_IDS_CHANGED_ACTION = "android.net.wifi.NETWORK_IDS_CHANGED";

    /**
     * Activity Action: Pick a Wi-Fi network to connect to.
     * <p>Input: Nothing.
     * <p>Output: Nothing.
     */
    @SdkConstant(SdkConstantType.ACTIVITY_INTENT_ACTION)
    public static final String ACTION_PICK_WIFI_NETWORK = "android.net.wifi.PICK_WIFI_NETWORK";

    /**
     * In this Wi-Fi lock mode, Wi-Fi will be kept active,
     * and will behave normally, i.e., it will attempt to automatically
     * establish a connection to a remembered access point that is
     * within range, and will do periodic scans if there are remembered
     * access points but none are in range.
     */
    public static final int WIFI_MODE_FULL = 1;
    /**
     * In this Wi-Fi lock mode, Wi-Fi will be kept active,
     * but the only operation that will be supported is initiation of
     * scans, and the subsequent reporting of scan results. No attempts
     * will be made to automatically connect to remembered access points,
     * nor will periodic scans be automatically performed looking for
     * remembered access points. Scans must be explicitly requested by
     * an application in this mode.
     */
    public static final int WIFI_MODE_SCAN_ONLY = 2;

    /** Anything worse than or equal to this will show 0 bars. */
    private static final int MIN_RSSI = -100;

    /** Anything better than or equal to this will show the max bars. */
    private static final int MAX_RSSI = -55;

    IWifiManager mService;
    Handler mHandler;

    /* Maximum number of active locks we allow.
     * This limit was added to prevent apps from creating a ridiculous number
     * of locks and crashing the system by overflowing the global ref table.
     */
    private static final int MAX_ACTIVE_LOCKS = 50;

    /* Number of currently active WifiLocks and MulticastLocks */
    private int mActiveLockCount;

    /**
     * Create a new WifiManager instance.
     * Applications will almost always want to use
     * {@link android.content.Context#getSystemService Context.getSystemService()} to retrieve
     * the standard {@link android.content.Context#WIFI_SERVICE Context.WIFI_SERVICE}.
     * @param service the Binder interface
     * @param handler target for messages
     * @hide - hide this because it takes in a parameter of type IWifiManager, which
     * is a system private class.
     */
    public WifiManager(IWifiManager service, Handler handler) {
        mService = service;
        mHandler = handler;
    }

    /**
     * Return a list of all the networks configured in the supplicant.
     * Not all fields of WifiConfiguration are returned. Only the following
     * fields are filled in:
     * <ul>
     * <li>networkId</li>
     * <li>SSID</li>
     * <li>BSSID</li>
     * <li>priority</li>
     * <li>allowedProtocols</li>
     * <li>allowedKeyManagement</li>
     * <li>allowedAuthAlgorithms</li>
     * <li>allowedPairwiseCiphers</li>
     * <li>allowedGroupCiphers</li>
     * </ul>
     * @return a list of network configurations in the form of a list
     * of {@link WifiConfiguration} objects.
     */
    public List<WifiConfiguration> getConfiguredNetworks() {
        try {
            return mService.getConfiguredNetworks();
        } catch (RemoteException e) {
            return null;
        }
    }

    /**
     * Add a new network description to the set of configured networks.
     * The {@code networkId} field of the supplied configuration object
     * is ignored.
     * <p/>
     * The new network will be marked DISABLED by default. To enable it,
     * called {@link #enableNetwork}.
     *
     * @param config the set of variables that describe the configuration,
     *            contained in a {@link WifiConfiguration} object.
     * @return the ID of the newly created network description. This is used in
     *         other operations to specified the network to be acted upon.
     *         Returns {@code -1} on failure.
     */
    public int addNetwork(WifiConfiguration config) {
        if (config == null) {
            return -1;
        }
        config.networkId = -1;
        return addOrUpdateNetwork(config);
    }

    /**
     * Update the network description of an existing configured network.
     *
     * @param config the set of variables that describe the configuration,
     *            contained in a {@link WifiConfiguration} object. It may
     *            be sparse, so that only the items that are being changed
     *            are non-<code>null</code>. The {@code networkId} field
     *            must be set to the ID of the existing network being updated.
     * @return Returns the {@code networkId} of the supplied
     *         {@code WifiConfiguration} on success.
     *         <br/>
     *         Returns {@code -1} on failure, including when the {@code networkId}
     *         field of the {@code WifiConfiguration} does not refer to an
     *         existing network.
     */
    public int updateNetwork(WifiConfiguration config) {
        if (config == null || config.networkId < 0) {
            return -1;
        }
        return addOrUpdateNetwork(config);
    }

    /**
     * Internal method for doing the RPC that creates a new network description
     * or updates an existing one.
     *
     * @param config The possibly sparse object containing the variables that
     *         are to set or updated in the network description.
     * @return the ID of the network on success, {@code -1} on failure.
     */
    private int addOrUpdateNetwork(WifiConfiguration config) {
        try {
            return mService.addOrUpdateNetwork(config);
        } catch (RemoteException e) {
            return -1;
        }
    }

    /**
     * Remove the specified network from the list of configured networks.
     * This may result in the asynchronous delivery of state change
     * events.
     * @param netId the integer that identifies the network configuration
     * to the supplicant
     * @return {@code true} if the operation succeeded
     */
    public boolean removeNetwork(int netId) {
        try {
            return mService.removeNetwork(netId);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Allow a previously configured network to be associated with. If
     * <code>disableOthers</code> is true, then all other configured
     * networks are disabled, and an attempt to connect to the selected
     * network is initiated. This may result in the asynchronous delivery
     * of state change events.
     * @param netId the ID of the network in the list of configured networks
     * @param disableOthers if true, disable all other networks. The way to
     * select a particular network to connect to is specify {@code true}
     * for this parameter.
     * @return {@code true} if the operation succeeded
     */
    public boolean enableNetwork(int netId, boolean disableOthers) {
        try {
            return mService.enableNetwork(netId, disableOthers);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Disable a configured network. The specified network will not be
     * a candidate for associating. This may result in the asynchronous
     * delivery of state change events.
     * @param netId the ID of the network as returned by {@link #addNetwork}.
     * @return {@code true} if the operation succeeded
     */
    public boolean disableNetwork(int netId) {
        try {
            return mService.disableNetwork(netId);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Disassociate from the currently active access point. This may result
     * in the asynchronous delivery of state change events.
     * @return {@code true} if the operation succeeded
     */
    public boolean disconnect() {
        try {
            return mService.disconnect();
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Reconnect to the currently active access point, if we are currently
     * disconnected. This may result in the asynchronous delivery of state
     * change events.
     * @return {@code true} if the operation succeeded
     */
    public boolean reconnect() {
        try {
            return mService.reconnect();
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Reconnect to the currently active access point, even if we are already
     * connected. This may result in the asynchronous delivery of state
     * change events.
     * @return {@code true} if the operation succeeded
     */
    public boolean reassociate() {
        try {
            return mService.reassociate();
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Check that the supplicant daemon is responding to requests.
     * @return {@code true} if we were able to communicate with the supplicant and
     * it returned the expected response to the PING message.
     */
    public boolean pingSupplicant() {
        if (mService == null)
            return false;
        try {
            return mService.pingSupplicant();
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Request a scan for access points. Returns immediately. The availability
     * of the results is made known later by means of an asynchronous event sent
     * on completion of the scan.
     * @return {@code true} if the operation succeeded, i.e., the scan was initiated
     */
    public boolean startScan() {
        try {
            return mService.startScan(false);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Request a scan for access points. Returns immediately. The availability
     * of the results is made known later by means of an asynchronous event sent
     * on completion of the scan.
     * This is a variant of startScan that forces an active scan, even if passive
     * scans are the current default
     * @return {@code true} if the operation succeeded, i.e., the scan was initiated
     *
     * @hide
     */
    public boolean startScanActive() {
        try {
            return mService.startScan(true);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Return dynamic information about the current Wi-Fi connection, if any is active.
     * @return the Wi-Fi information, contained in {@link WifiInfo}.
     */
    public WifiInfo getConnectionInfo() {
        try {
            return mService.getConnectionInfo();
        } catch (RemoteException e) {
            return null;
        }
    }

    /**
     * Return the results of the latest access point scan.
     * @return the list of access points found in the most recent scan.
     */
    public List<ScanResult> getScanResults() {
        try {
            return mService.getScanResults();
        } catch (RemoteException e) {
            return null;
        }
    }

    /**
     * Tell the supplicant to persist the current list of configured networks.
     * <p>
     * Note: It is possible for this method to change the network IDs of
     * existing networks. You should assume the network IDs can be different
     * after calling this method.
     *
     * @return {@code true} if the operation succeeded
     */
    public boolean saveConfiguration() {
        try {
            return mService.saveConfiguration();
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Return the number of frequency channels that are allowed
     * to be used in the current regulatory domain.
     * @return the number of allowed channels, or {@code -1} if an error occurs
     *
     * @hide pending API council
     */
    public int getNumAllowedChannels() {
        try {
            return mService.getNumAllowedChannels();
        } catch (RemoteException e) {
            return -1;
        }
    }

    /**
     * Set the number of frequency channels that are allowed to be used
     * in the current regulatory domain. This method should be used only
     * if the correct number of channels cannot be determined automatically
     * for some reason.
     * @param numChannels the number of allowed channels. Must be greater than 0
     * and less than or equal to 16.
     * @param persist {@code true} if you want this remembered
     * @return {@code true} if the operation succeeds, {@code false} otherwise, e.g.,
     * {@code numChannels} is out of range.
     *
     * @hide pending API council
     */
    public boolean setNumAllowedChannels(int numChannels, boolean persist) {
        try {
            return mService.setNumAllowedChannels(numChannels, persist);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Return the list of valid values for the number of allowed radio channels
     * for various regulatory domains.
     * @return the list of channel counts, or {@code null} if the operation fails
     *
     * @hide pending API council review
     */
    public int[] getValidChannelCounts() {
        try {
            return mService.getValidChannelCounts();
        } catch (RemoteException e) {
            return null;
        }
   }

    /**
     * Return the DHCP-assigned addresses from the last successful DHCP request,
     * if any.
     * @return the DHCP information
     */
    public DhcpInfo getDhcpInfo() {
        try {
            return mService.getDhcpInfo();
        } catch (RemoteException e) {
            return null;
        }
    }


    /**
     * Enable or disable Wi-Fi.
     * @param enabled {@code true} to enable, {@code false} to disable.
     * @return {@code true} if the operation succeeds (or if the existing state
     *         is the same as the requested state).
     */
    public boolean setWifiEnabled(boolean enabled) {
        try {
            return mService.setWifiEnabled(enabled);
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Gets the Wi-Fi enabled state.
     * @return One of {@link #WIFI_STATE_DISABLED},
     *         {@link #WIFI_STATE_DISABLING}, {@link #WIFI_STATE_ENABLED},
     *         {@link #WIFI_STATE_ENABLING}, {@link #WIFI_STATE_UNKNOWN}
     * @see #isWifiEnabled()
     */
    public int getWifiState() {
        try {
            return mService.getWifiEnabledState();
        } catch (RemoteException e) {
            return WIFI_STATE_UNKNOWN;
        }
    }

    /**
     * Return whether Wi-Fi is enabled or disabled.
     * @return {@code true} if Wi-Fi is enabled
     * @see #getWifiState()
     */
    public boolean isWifiEnabled() {
        return getWifiState() == WIFI_STATE_ENABLED;
    }

    /**
     * Calculates the level of the signal. This should be used any time a signal
     * is being shown.
     *
     * @param rssi The power of the signal measured in RSSI.
     * @param numLevels The number of levels to consider in the calculated
     *            level.
     * @return A level of the signal, given in the range of 0 to numLevels-1
     *         (both inclusive).
     */
    public static int calculateSignalLevel(int rssi, int numLevels) {
        if (rssi <= MIN_RSSI) {
            return 0;
        } else if (rssi >= MAX_RSSI) {
            return numLevels - 1;
        } else {
            int partitionSize = (MAX_RSSI - MIN_RSSI) / (numLevels - 1);
            return (rssi - MIN_RSSI) / partitionSize;
        }
    }

    /**
     * Compares two signal strengths.
     *
     * @param rssiA The power of the first signal measured in RSSI.
     * @param rssiB The power of the second signal measured in RSSI.
     * @return Returns <0 if the first signal is weaker than the second signal,
     *         0 if the two signals have the same strength, and >0 if the first
     *         signal is stronger than the second signal.
     */
    public static int compareSignalLevel(int rssiA, int rssiB) {
        return rssiA - rssiB;
    }

    /**
     * Allows an application to keep the Wi-Fi radio awake.
     * Normally the Wi-Fi radio may turn off when the user has not used the device in a while.
     * Acquiring a WifiLock will keep the radio on until the lock is released.  Multiple
     * applications may hold WifiLocks, and the radio will only be allowed to turn off when no
     * WifiLocks are held in any application.
     *
     * Before using a WifiLock, consider carefully if your application requires Wi-Fi access, or
     * could function over a mobile network, if available.  A program that needs to download large
     * files should hold a WifiLock to ensure that the download will complete, but a program whose
     * network usage is occasional or low-bandwidth should not hold a WifiLock to avoid adversely
     * affecting battery life.
     *
     * Note that WifiLocks cannot override the user-level "Wi-Fi Enabled" setting, nor Airplane
     * Mode.  They simply keep the radio from turning off when Wi-Fi is already on but the device
     * is idle.
     */
    public class WifiLock {
        private String mTag;
        private final IBinder mBinder;
        private int mRefCount;
        int mLockType;
        private boolean mRefCounted;
        private boolean mHeld;

        private WifiLock(int lockType, String tag) {
            mTag = tag;
            mLockType = lockType;
            mBinder = new Binder();
            mRefCount = 0;
            mRefCounted = true;
            mHeld = false;
        }

        /**
         * Locks the Wi-Fi radio on until {@link #release} is called.
         *
         * If this WifiLock is reference-counted, each call to {@code acquire} will increment the
         * reference count, and the radio will remain locked as long as the reference count is
         * above zero.
         *
         * If this WifiLock is not reference-counted, the first call to {@code acquire} will lock
         * the radio, but subsequent calls will be ignored.  Only one call to {@link #release}
         * will be required, regardless of the number of times that {@code acquire} is called.
         */
        public void acquire() {
            synchronized (mBinder) {
                if (mRefCounted ? (++mRefCount > 0) : (!mHeld)) {
                    try {
                        mService.acquireWifiLock(mBinder, mLockType, mTag);
                        synchronized (WifiManager.this) {
                            if (mActiveLockCount >= MAX_ACTIVE_LOCKS) {
                                mService.releaseWifiLock(mBinder);
                                throw new UnsupportedOperationException(
                                            "Exceeded maximum number of wifi locks");
                            }
                            mActiveLockCount++;
                        }
                    } catch (RemoteException ignore) {
                    }
                    mHeld = true;
                }
            }
        }

        /**
         * Unlocks the Wi-Fi radio, allowing it to turn off when the device is idle.
         *
         * If this WifiLock is reference-counted, each call to {@code release} will decrement the
         * reference count, and the radio will be unlocked only when the reference count reaches
         * zero.  If the reference count goes below zero (that is, if {@code release} is called
         * a greater number of times than {@link #acquire}), an exception is thrown.
         *
         * If this WifiLock is not reference-counted, the first call to {@code release} (after
         * the radio was locked using {@link #acquire}) will unlock the radio, and subsequent
         * calls will be ignored.
         */
        public void release() {
            synchronized (mBinder) {
                if (mRefCounted ? (--mRefCount == 0) : (mHeld)) {
                    try {
                        mService.releaseWifiLock(mBinder);
                        synchronized (WifiManager.this) {
                            mActiveLockCount--;
                        }
                    } catch (RemoteException ignore) {
                    }
                    mHeld = false;
                }
                if (mRefCount < 0) {
                    throw new RuntimeException("WifiLock under-locked " + mTag);
                }
            }
        }

        /**
         * Controls whether this is a reference-counted or non-reference-counted WifiLock.
         *
         * Reference-counted WifiLocks keep track of the number of calls to {@link #acquire} and
         * {@link #release}, and only allow the radio to sleep when every call to {@link #acquire}
         * has been balanced with a call to {@link #release}.  Non-reference-counted WifiLocks
         * lock the radio whenever {@link #acquire} is called and it is unlocked, and unlock the
         * radio whenever {@link #release} is called and it is locked.
         *
         * @param refCounted true if this WifiLock should keep a reference count
         */
        public void setReferenceCounted(boolean refCounted) {
            mRefCounted = refCounted;
        }

        /**
         * Checks whether this WifiLock is currently held.
         *
         * @return true if this WifiLock is held, false otherwise
         */
        public boolean isHeld() {
            synchronized (mBinder) {
                return mHeld;
            }
        }

        public String toString() {
            String s1, s2, s3;
            synchronized (mBinder) {
                s1 = Integer.toHexString(System.identityHashCode(this));
                s2 = mHeld ? "held; " : "";
                if (mRefCounted) {
                    s3 = "refcounted: refcount = " + mRefCount;
                } else {
                    s3 = "not refcounted";
                }
                return "WifiLock{ " + s1 + "; " + s2 + s3 + " }";
            }
        }

        @Override
        protected void finalize() throws Throwable {
            super.finalize();
            synchronized (mBinder) {
                if (mHeld) {
                    try {
                        mService.releaseWifiLock(mBinder);
                        synchronized (WifiManager.this) {
                            mActiveLockCount--;
                        }
                    } catch (RemoteException ignore) {
                    }
                }
            }
        }
    }

    /**
     * Creates a new WifiLock.
     *
     * @param lockType the type of lock to create. See {@link #WIFI_MODE_FULL} and
     * {@link #WIFI_MODE_SCAN_ONLY} for descriptions of the types of Wi-Fi locks.
     * @param tag a tag for the WifiLock to identify it in debugging messages.  This string is
     *            never shown to the user under normal conditions, but should be descriptive
     *            enough to identify your application and the specific WifiLock within it, if it
     *            holds multiple WifiLocks.
     *
     * @return a new, unacquired WifiLock with the given tag.
     *
     * @see WifiLock
     */
    public WifiLock createWifiLock(int lockType, String tag) {
        return new WifiLock(lockType, tag);
    }

    /**
     * Creates a new WifiLock.
     *
     * @param tag a tag for the WifiLock to identify it in debugging messages.  This string is
     *            never shown to the user under normal conditions, but should be descriptive
     *            enough to identify your application and the specific WifiLock within it, if it
     *            holds multiple WifiLocks.
     *
     * @return a new, unacquired WifiLock with the given tag.
     *
     * @see WifiLock
     */
    public WifiLock createWifiLock(String tag) {
        return new WifiLock(WIFI_MODE_FULL, tag);
    }


    /**
     * Create a new MulticastLock
     *
     * @param tag a tag for the MulticastLock to identify it in debugging
     *            messages.  This string is never shown to the user under
     *            normal conditions, but should be descriptive enough to
     *            identify your application and the specific MulticastLock
     *            within it, if it holds multiple MulticastLocks.
     *
     * @return a new, unacquired MulticastLock with the given tag.
     *
     * @see MulticastLock
     */
    public MulticastLock createMulticastLock(String tag) {
        return new MulticastLock(tag);
    }

    /**
     * Allows an application to receive Wifi Multicast packets.
     * Normally the Wifi stack filters out packets not explicitly
     * addressed to this device.  Acquring a MulticastLock will
     * cause the stack to receive packets addressed to multicast
     * addresses.  Processing these extra packets can cause a noticable
     * battery drain and should be disabled when not needed.
     */
    public class MulticastLock {
        private String mTag;
        private final IBinder mBinder;
        private int mRefCount;
        private boolean mRefCounted;
        private boolean mHeld;

        private MulticastLock(String tag) {
            mTag = tag;
            mBinder = new Binder();
            mRefCount = 0;
            mRefCounted = true;
            mHeld = false;
        }

        /**
         * Locks Wifi Multicast on until {@link #release} is called.
         *
         * If this MulticastLock is reference-counted each call to
         * {@code acquire} will increment the reference count, and the
         * wifi interface will receive multicast packets as long as the
         * reference count is above zero.
         *
         * If this MulticastLock is not reference-counted, the first call to
         * {@code acquire} will turn on the multicast packets, but subsequent
         * calls will be ignored.  Only one call to {@link #release} will
         * be required, regardless of the number of times that {@code acquire}
         * is called.
         *
         * Note that other applications may also lock Wifi Multicast on.
         * Only they can relinquish their lock.
         *
         * Also note that applications cannot leave Multicast locked on.
         * When an app exits or crashes, any Multicast locks will be released.
         */
        public void acquire() {
            synchronized (mBinder) {
                if (mRefCounted ? (++mRefCount > 0) : (!mHeld)) {
                    try {
                        mService.acquireMulticastLock(mBinder, mTag);
                        synchronized (WifiManager.this) {
                            if (mActiveLockCount >= MAX_ACTIVE_LOCKS) {
                                mService.releaseMulticastLock();
                                throw new UnsupportedOperationException(
                                        "Exceeded maximum number of wifi locks");
                            }
                            mActiveLockCount++;
                        }
                    } catch (RemoteException ignore) {
                    }
                    mHeld = true;
                }
            }
        }

        /**
         * Unlocks Wifi Multicast, restoring the filter of packets
         * not addressed specifically to this device and saving power.
         *
         * If this MulticastLock is reference-counted, each call to
         * {@code release} will decrement the reference count, and the
         * multicast packets will only stop being received when the reference
         * count reaches zero.  If the reference count goes below zero (that
         * is, if {@code release} is called a greater number of times than
         * {@link #acquire}), an exception is thrown.
         *
         * If this MulticastLock is not reference-counted, the first call to
         * {@code release} (after the radio was multicast locked using
         * {@link #acquire}) will unlock the multicast, and subsequent calls
         * will be ignored.
         *
         * Note that if any other Wifi Multicast Locks are still outstanding
         * this {@code release} call will not have an immediate effect.  Only
         * when all applications have released all their Multicast Locks will
         * the Multicast filter be turned back on.
         *
         * Also note that when an app exits or crashes all of its Multicast
         * Locks will be automatically released.
         */
        public void release() {
            synchronized (mBinder) {
                if (mRefCounted ? (--mRefCount == 0) : (mHeld)) {
                    try {
                        mService.releaseMulticastLock();
                        synchronized (WifiManager.this) {
                            mActiveLockCount--;
                        }
                    } catch (RemoteException ignore) {
                    }
                    mHeld = false;
                }
                if (mRefCount < 0) {
                    throw new RuntimeException("MulticastLock under-locked "
                            + mTag);
                }
            }
        }

        /**
         * Controls whether this is a reference-counted or non-reference-
         * counted MulticastLock.
         *
         * Reference-counted MulticastLocks keep track of the number of calls
         * to {@link #acquire} and {@link #release}, and only stop the
         * reception of multicast packets when every call to {@link #acquire}
         * has been balanced with a call to {@link #release}.  Non-reference-
         * counted MulticastLocks allow the reception of multicast packets
         * whenever {@link #acquire} is called and stop accepting multicast
         * packets whenever {@link #release} is called.
         *
         * @param refCounted true if this MulticastLock should keep a reference
         * count
         */
        public void setReferenceCounted(boolean refCounted) {
            mRefCounted = refCounted;
        }

        /**
         * Checks whether this MulticastLock is currently held.
         *
         * @return true if this MulticastLock is held, false otherwise
         */
        public boolean isHeld() {
            synchronized (mBinder) {
                return mHeld;
            }
        }

        public String toString() {
            String s1, s2, s3;
            synchronized (mBinder) {
                s1 = Integer.toHexString(System.identityHashCode(this));
                s2 = mHeld ? "held; " : "";
                if (mRefCounted) {
                    s3 = "refcounted: refcount = " + mRefCount;
                } else {
                    s3 = "not refcounted";
                }
                return "MulticastLock{ " + s1 + "; " + s2 + s3 + " }";
            }
        }

        @Override
        protected void finalize() throws Throwable {
            super.finalize();
            setReferenceCounted(false);
            release();
        }
    }

    /**
     * Check multicast filter status.
     *
     * @return true if multicast packets are allowed.
     *
     * @hide pending API council approval
     */
    public boolean isMulticastEnabled() {
        try {
            return mService.isMulticastEnabled();
        } catch (RemoteException e) {
            return false;
        }
    }

    /**
     * Initialize the multicast filtering to 'on'
     * @hide no intent to publish
     */
    public boolean initializeMulticastFiltering() {
        try {
            mService.initializeMulticastFiltering();
            return true;
        } catch (RemoteException e) {
             return false;
        }
    }
}