The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2006 The Android Open Source Project |
| 3 | * |
| 4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | * you may not use this file except in compliance with the License. |
| 6 | * You may obtain a copy of the License at |
| 7 | * |
| 8 | * http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | * |
| 10 | * Unless required by applicable law or agreed to in writing, software |
| 11 | * distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | * See the License for the specific language governing permissions and |
| 14 | * limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package android.os; |
| 18 | |
| 19 | import java.io.FileDescriptor; |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 20 | |
| 21 | /** |
| 22 | * Base interface for a remotable object, the core part of a lightweight |
| 23 | * remote procedure call mechanism designed for high performance when |
| 24 | * performing in-process and cross-process calls. This |
| 25 | * interface describes the abstract protocol for interacting with a |
| 26 | * remotable object. Do not implement this interface directly, instead |
| 27 | * extend from {@link Binder}. |
| 28 | * |
| 29 | * <p>The key IBinder API is {@link #transact transact()} matched by |
| 30 | * {@link Binder#onTransact Binder.onTransact()}. These |
| 31 | * methods allow you to send a call to an IBinder object and receive a |
| 32 | * call coming in to a Binder object, respectively. This transaction API |
| 33 | * is synchronous, such that a call to {@link #transact transact()} does not |
| 34 | * return until the target has returned from |
| 35 | * {@link Binder#onTransact Binder.onTransact()}; this is the |
| 36 | * expected behavior when calling an object that exists in the local |
| 37 | * process, and the underlying inter-process communication (IPC) mechanism |
| 38 | * ensures that these same semantics apply when going across processes. |
| 39 | * |
| 40 | * <p>The data sent through transact() is a {@link Parcel}, a generic buffer |
| 41 | * of data that also maintains some meta-data about its contents. The meta |
| 42 | * data is used to manage IBinder object references in the buffer, so that those |
| 43 | * references can be maintained as the buffer moves across processes. This |
| 44 | * mechanism ensures that when an IBinder is written into a Parcel and sent to |
| 45 | * another process, if that other process sends a reference to that same IBinder |
| 46 | * back to the original process, then the original process will receive the |
| 47 | * same IBinder object back. These semantics allow IBinder/Binder objects to |
| 48 | * be used as a unique identity (to serve as a token or for other purposes) |
| 49 | * that can be managed across processes. |
| 50 | * |
| 51 | * <p>The system maintains a pool of transaction threads in each process that |
| 52 | * it runs in. These threads are used to dispatch all |
| 53 | * IPCs coming in from other processes. For example, when an IPC is made from |
| 54 | * process A to process B, the calling thread in A blocks in transact() as |
| 55 | * it sends the transaction to process B. The next available pool thread in |
| 56 | * B receives the incoming transaction, calls Binder.onTransact() on the target |
| 57 | * object, and replies with the result Parcel. Upon receiving its result, the |
| 58 | * thread in process A returns to allow its execution to continue. In effect, |
| 59 | * other processes appear to use as additional threads that you did not create |
| 60 | * executing in your own process. |
| 61 | * |
| 62 | * <p>The Binder system also supports recursion across processes. For example |
| 63 | * if process A performs a transaction to process B, and process B while |
| 64 | * handling that transaction calls transact() on an IBinder that is implemented |
| 65 | * in A, then the thread in A that is currently waiting for the original |
| 66 | * transaction to finish will take care of calling Binder.onTransact() on the |
| 67 | * object being called by B. This ensures that the recursion semantics when |
| 68 | * calling remote binder object are the same as when calling local objects. |
| 69 | * |
| 70 | * <p>When working with remote objects, you often want to find out when they |
| 71 | * are no longer valid. There are three ways this can be determined: |
| 72 | * <ul> |
| 73 | * <li> The {@link #transact transact()} method will throw a |
| 74 | * {@link RemoteException} exception if you try to call it on an IBinder |
| 75 | * whose process no longer exists. |
| 76 | * <li> The {@link #pingBinder()} method can be called, and will return false |
| 77 | * if the remote process no longer exists. |
| 78 | * <li> The {@link #linkToDeath linkToDeath()} method can be used to register |
| 79 | * a {@link DeathRecipient} with the IBinder, which will be called when its |
| 80 | * containing process goes away. |
| 81 | * </ul> |
| 82 | * |
| 83 | * @see Binder |
| 84 | */ |
| 85 | public interface IBinder { |
| 86 | /** |
| 87 | * The first transaction code available for user commands. |
| 88 | */ |
| 89 | int FIRST_CALL_TRANSACTION = 0x00000001; |
| 90 | /** |
| 91 | * The last transaction code available for user commands. |
| 92 | */ |
| 93 | int LAST_CALL_TRANSACTION = 0x00ffffff; |
| 94 | |
| 95 | /** |
| 96 | * IBinder protocol transaction code: pingBinder(). |
| 97 | */ |
| 98 | int PING_TRANSACTION = ('_'<<24)|('P'<<16)|('N'<<8)|'G'; |
| 99 | |
| 100 | /** |
| 101 | * IBinder protocol transaction code: dump internal state. |
| 102 | */ |
| 103 | int DUMP_TRANSACTION = ('_'<<24)|('D'<<16)|('M'<<8)|'P'; |
| 104 | |
| 105 | /** |
| 106 | * IBinder protocol transaction code: interrogate the recipient side |
| 107 | * of the transaction for its canonical interface descriptor. |
| 108 | */ |
| 109 | int INTERFACE_TRANSACTION = ('_'<<24)|('N'<<16)|('T'<<8)|'F'; |
| 110 | |
| 111 | /** |
Dianne Hackborn | 0d4b9c9 | 2011-06-15 11:41:48 -0700 | [diff] [blame] | 112 | * IBinder protocol transaction code: send a tweet to the target |
| 113 | * object. The data in the parcel is intended to be delivered to |
| 114 | * a shared messaging service associated with the object; it can be |
| 115 | * anything, as long as it is not more than 130 UTF-8 characters to |
| 116 | * conservatively fit within common messaging services. As part of |
| 117 | * {@link Build.VERSION_CODES#HONEYCOMB_MR2}, all Binder objects are |
| 118 | * expected to support this protocol for fully integrated tweeting |
| 119 | * across the platform. To support older code, the default implementation |
| 120 | * logs the tweet to the main log as a simple emulation of broadcasting |
| 121 | * it publicly over the Internet. |
| 122 | * |
| 123 | * <p>Also, upon completing the dispatch, the object must make a cup |
| 124 | * of tea, return it to the caller, and exclaim "jolly good message |
| 125 | * old boy!". |
| 126 | */ |
| 127 | int TWEET_TRANSACTION = ('_'<<24)|('T'<<16)|('W'<<8)|'T'; |
| 128 | |
| 129 | /** |
Dianne Hackborn | a3d487c | 2011-12-01 18:42:24 -0800 | [diff] [blame] | 130 | * IBinder protocol transaction code: tell an app asynchronously that the |
| 131 | * caller likes it. The app is responsible for incrementing and maintaining |
| 132 | * its own like counter, and may display this value to the user to indicate the |
| 133 | * quality of the app. This is an optional command that applications do not |
| 134 | * need to handle, so the default implementation is to do nothing. |
| 135 | * |
| 136 | * <p>There is no response returned and nothing about the |
| 137 | * system will be functionally affected by it, but it will improve the |
| 138 | * app's self-esteem. |
| 139 | */ |
| 140 | int LIKE_TRANSACTION = ('_'<<24)|('L'<<16)|('I'<<8)|'K'; |
| 141 | |
Dianne Hackborn | a53de06 | 2012-05-08 18:53:51 -0700 | [diff] [blame] | 142 | /** @hide */ |
| 143 | int SYSPROPS_TRANSACTION = ('_'<<24)|('S'<<16)|('P'<<8)|'R'; |
| 144 | |
Dianne Hackborn | a3d487c | 2011-12-01 18:42:24 -0800 | [diff] [blame] | 145 | /** |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 146 | * Flag to {@link #transact}: this is a one-way call, meaning that the |
| 147 | * caller returns immediately, without waiting for a result from the |
Dirk Dougherty | d76ef97 | 2010-03-29 14:20:41 -0700 | [diff] [blame] | 148 | * callee. Applies only if the caller and callee are in different |
| 149 | * processes. |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 150 | */ |
| 151 | int FLAG_ONEWAY = 0x00000001; |
| 152 | |
| 153 | /** |
| 154 | * Get the canonical name of the interface supported by this binder. |
| 155 | */ |
| 156 | public String getInterfaceDescriptor() throws RemoteException; |
| 157 | |
| 158 | /** |
| 159 | * Check to see if the object still exists. |
| 160 | * |
| 161 | * @return Returns false if the |
| 162 | * hosting process is gone, otherwise the result (always by default |
| 163 | * true) returned by the pingBinder() implementation on the other |
| 164 | * side. |
| 165 | */ |
| 166 | public boolean pingBinder(); |
| 167 | |
| 168 | /** |
| 169 | * Check to see if the process that the binder is in is still alive. |
| 170 | * |
| 171 | * @return false if the process is not alive. Note that if it returns |
| 172 | * true, the process may have died while the call is returning. |
| 173 | */ |
| 174 | public boolean isBinderAlive(); |
| 175 | |
| 176 | /** |
| 177 | * Attempt to retrieve a local implementation of an interface |
| 178 | * for this Binder object. If null is returned, you will need |
| 179 | * to instantiate a proxy class to marshall calls through |
| 180 | * the transact() method. |
| 181 | */ |
| 182 | public IInterface queryLocalInterface(String descriptor); |
| 183 | |
| 184 | /** |
| 185 | * Print the object's state into the given stream. |
| 186 | * |
| 187 | * @param fd The raw file descriptor that the dump is being sent to. |
| 188 | * @param args additional arguments to the dump request. |
| 189 | */ |
| 190 | public void dump(FileDescriptor fd, String[] args) throws RemoteException; |
| 191 | |
| 192 | /** |
Dianne Hackborn | 9a84983 | 2011-04-07 15:11:57 -0700 | [diff] [blame] | 193 | * Like {@link #dump(FileDescriptor, String[])} but always executes |
| 194 | * asynchronously. If the object is local, a new thread is created |
| 195 | * to perform the dump. |
| 196 | * |
| 197 | * @param fd The raw file descriptor that the dump is being sent to. |
| 198 | * @param args additional arguments to the dump request. |
| 199 | */ |
| 200 | public void dumpAsync(FileDescriptor fd, String[] args) throws RemoteException; |
| 201 | |
| 202 | /** |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 203 | * Perform a generic operation with the object. |
| 204 | * |
| 205 | * @param code The action to perform. This should |
| 206 | * be a number between {@link #FIRST_CALL_TRANSACTION} and |
| 207 | * {@link #LAST_CALL_TRANSACTION}. |
Glenn Kasten | 334031c | 2010-11-09 21:54:38 -0800 | [diff] [blame] | 208 | * @param data Marshalled data to send to the target. Must not be null. |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 209 | * If you are not sending any data, you must create an empty Parcel |
| 210 | * that is given here. |
| 211 | * @param reply Marshalled data to be received from the target. May be |
| 212 | * null if you are not interested in the return value. |
| 213 | * @param flags Additional operation flags. Either 0 for a normal |
| 214 | * RPC, or {@link #FLAG_ONEWAY} for a one-way RPC. |
| 215 | */ |
| 216 | public boolean transact(int code, Parcel data, Parcel reply, int flags) |
| 217 | throws RemoteException; |
| 218 | |
| 219 | /** |
| 220 | * Interface for receiving a callback when the process hosting an IBinder |
| 221 | * has gone away. |
| 222 | * |
| 223 | * @see #linkToDeath |
| 224 | */ |
| 225 | public interface DeathRecipient { |
| 226 | public void binderDied(); |
| 227 | } |
| 228 | |
| 229 | /** |
| 230 | * Register the recipient for a notification if this binder |
| 231 | * goes away. If this binder object unexpectedly goes away |
| 232 | * (typically because its hosting process has been killed), |
| 233 | * then the given {@link DeathRecipient}'s |
| 234 | * {@link DeathRecipient#binderDied DeathRecipient.binderDied()} method |
| 235 | * will be called. |
| 236 | * |
| 237 | * <p>You will only receive death notifications for remote binders, |
| 238 | * as local binders by definition can't die without you dying as well. |
| 239 | * |
John Spurlock | 6098c5d | 2013-06-17 10:32:46 -0400 | [diff] [blame] | 240 | * @throws RemoteException if the target IBinder's |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 241 | * process has already died. |
| 242 | * |
| 243 | * @see #unlinkToDeath |
| 244 | */ |
| 245 | public void linkToDeath(DeathRecipient recipient, int flags) |
| 246 | throws RemoteException; |
| 247 | |
| 248 | /** |
| 249 | * Remove a previously registered death notification. |
| 250 | * The recipient will no longer be called if this object |
| 251 | * dies. |
| 252 | * |
John Spurlock | 6098c5d | 2013-06-17 10:32:46 -0400 | [diff] [blame] | 253 | * @return {@code true} if the <var>recipient</var> is successfully |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 254 | * unlinked, assuring you that its |
| 255 | * {@link DeathRecipient#binderDied DeathRecipient.binderDied()} method |
John Spurlock | 6098c5d | 2013-06-17 10:32:46 -0400 | [diff] [blame] | 256 | * will not be called; {@code false} if the target IBinder has already |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 257 | * died, meaning the method has been (or soon will be) called. |
| 258 | * |
John Spurlock | 6098c5d | 2013-06-17 10:32:46 -0400 | [diff] [blame] | 259 | * @throws java.util.NoSuchElementException if the given |
The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 260 | * <var>recipient</var> has not been registered with the IBinder, and |
| 261 | * the IBinder is still alive. Note that if the <var>recipient</var> |
| 262 | * was never registered, but the IBinder has already died, then this |
| 263 | * exception will <em>not</em> be thrown, and you will receive a false |
| 264 | * return value instead. |
| 265 | */ |
| 266 | public boolean unlinkToDeath(DeathRecipient recipient, int flags); |
| 267 | } |