在上一篇博客中Android源碼分析–MediaServer源碼分析（一），我們知道了ProcessState和defaultServiceManager，在分析源碼的過程中，我們被Android的Binder通信機制中的各種復雜的類關系搞的眼花繚亂，接下來我們就以MediaPlayerService為例來分析一下Binder的通信機制。首先來回顧一下：

• BpBinder和BBinder都是Android中Binder通信的代表類，其中BpBinder是客戶端用來與Server交互的代理類，p代表的就是proxy，而BBinder則是交互的目的端；
• BpBinder和BBinder是相互對應的，Binder系統會通過handle來標識對應的BBinder。

Android的通信機制基本上可以看做是Client、Server和ServiceManager三者之間的交互：

• Server首先要注冊一些Service到ServiceManager；
• 如果某個Client要使用Service，則首先到ServiceManager中獲得該Service的相關信息；
• Client得到Service信息，然后和該Service所在的Server進程建立通信之后使用Service。

注冊MediaPlayerService

我們知道若要使用一個Service的話首先要進行注冊，所有首先讓我們來看看MediaService是如何注冊的，文件位置：frameworks\base\media\libmediaplayerservice\MediaPlayerService.cpp

<code class="hljs coffeescript has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-reserved" style="box-sizing: border-box;">void</span> <span class="hljs-attribute" style="box-sizing: border-box; color: rgb(0, 136, 0);">MediaPlayerService</span>::instantiate() {defaultServiceManager<span class="hljs-function" style="box-sizing: border-box;"><span class="hljs-params" style="color: rgb(102, 0, 102); box-sizing: border-box;">()</span>-></span>addService(String16(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"media.player"</span>), <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MediaPlayerService()); }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

defaultServiceManager返回的其實是一個BpServiceManager對象，在這里我看到了注冊的函數addService：

<code class="hljs haskell has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"> virtual status_t addService(const <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">String16</span>& name, const sp<<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">IBinder</span>>& service){<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Parcel</span> <span class="hljs-typedef" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">data</span>, reply;</span>//將<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">Descriptor</span>作為令牌<span class="hljs-typedef" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">data</span>.writeInterfaceToken<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">IServiceManager</span>::<span class="hljs-title" style="box-sizing: border-box;">getInterfaceDescriptor</span>()</span>);</span><span class="hljs-typedef" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">data</span>.writeString16<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box;">name</span>)</span>;</span><span class="hljs-typedef" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">data</span>.writeStrongBinder<span class="hljs-container" style="box-sizing: border-box;">(<span class="hljs-title" style="box-sizing: border-box;">service</span>)</span>;</span>status_t err = remote()->transact(<span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">ADD_SERVICE_TRANSACTION</span>, <span class="hljs-typedef" style="box-sizing: border-box;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">data</span>, &reply);</span>return err == <span class="hljs-type" style="box-sizing: border-box; color: rgb(102, 0, 102);">NO_ERROR</span> ? reply.readExceptionCode() : err; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

Parcel類可以看作一個數據塊，在該類的內部主要封裝了一些數據操作的方法。在寫入數據之后remote()->transact方法，remote()方法返回的值是mRemote，在上一篇中我們知道它是一個BpBinder對象，之后我們的通信工作就交由了BpBinder的transact方法：

<code class="hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">status_t BpBinder<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;">::transact</span>(uint32_t code, const Parcel<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">&</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span>, Parcel<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">*</span> reply, uint32_t flags) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// Binder一旦死去將永遠不能復活.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mAlive) {status_t status <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> IPCThreadState<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;">::self</span>()<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">-></span>transact(mHandle, code, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span>, reply, flags);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (status <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">==</span> DEAD_OBJECT) mAlive <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> status;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> DEAD_OBJECT; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li></ul>

BpBinder完全將工作交給了IPCThreadState，接下來的任務也全部轉移到了IPCThreadState類中。

IPCThreadState類分析

IPCThreadState也是以單例模式設計的。由于每個進程只維護了一個ProcessState實例，同時ProcessState只啟動一個 Pool thread，也就是說每一個進程只會啟動一個Pool thread，因此每個進程則只需要一個IPCThreadState即可。首先讓我們來看看這個self方法，文件位置：frameworks\base\libs\binder\IPCThreadState.cpp

<code class="hljs php has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">IPCThreadState* IPCThreadState::<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">self</span>() {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (gHaveTLS) { restart:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> pthread_key_t k = gTLS;IPCThreadState* st = (IPCThreadState*)pthread_getspecific(k);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (st) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> st;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> IPCThreadState;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (gShutdown) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">NULL</span>;pthread_mutex_lock(&gTLSMutex);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!gHaveTLS) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (pthread_key_create(&gTLS, threadDestructor) != <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {pthread_mutex_unlock(&gTLSMutex);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">NULL</span>;}gHaveTLS = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">true</span>;}pthread_mutex_unlock(&gTLSMutex);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> restart; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li></ul>

TLS是Thread Local Storage的縮寫，表示線程本地存儲，類似于Java中的ThreadLocal機制)pthread_getspecific和)pthread_setspecific方法分別提供了設置變量和獲取變量的方法。

在這里我們看到了get方法，有get方法就一定有對應的set方法，set的設置就在構造函數中：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-label" style="box-sizing: border-box;">IPCThreadState:</span>:IPCThreadState(): mProcess(ProcessState::self()),mMyThreadId(androidGetTid()),mStrictModePolicy(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>),mLastTransactionBinderFlags(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {pthread_setspecific(gTLS, this)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>clearCaller()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mIn<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setDataCapacity</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">256</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mOut<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setDataCapacity</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">256</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

可以看到在構造函數中IPCThreadState將自身和線程本地存儲關聯起來了，在每一個IPCThreadState中都存在一個mIn和mOut，mIn用來存儲接收Binder的數據，mOut用來存儲發送到Binder的數據。

接下來看看transact方法：

<code class="hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">status_t IPCThreadState<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;">::transact</span>(int32_t <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">handle</span>,uint32_t code, const Parcel<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">&</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span>,Parcel<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">*</span> reply, uint32_t flags) {status_t err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>errorCheck();flags <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">|=</span> TF_ACCEPT_FDS;<span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">==</span> NO_ERROR) {<span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-attribute" style="box-sizing: border-box;">...</span>err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> writeTransactionData(BC_TRANSACTION, flags, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">handle</span>, code, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span>, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NULL</span>);} <span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (reply) {err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> waitForResponse(reply);} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {Parcel fakeReply;err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> waitForResponse(<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">&</span>fakeReply);}<span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-attribute" style="box-sizing: border-box;">...</span>} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> waitForResponse(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NULL</span>, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">NULL</span>);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> err; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>

在這里省略了一些打印輸出信息的語句，在這里我們可以清楚的看到通信的流程：先寫入數據，然后等待接收數據。

如何進行通信

在前面我們知道了通信的流程，首先寫入數據，之后等待回應，那么我們的通信就是這樣不斷的讀寫數據嗎？接下來我們來一下看一下這兩個讀寫的函數：?
1.寫入數據：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">status_t IPCThreadState::writeTransactionData(int32_t cmd, uint32_t binderFlags,int32_t handle, uint32_t code, const Parcel& data, status_t* statusBuffer) {binder_transaction_data tr<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.target</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.handle</span> = handle<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.code</span> = code<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.flags</span> = binderFlags<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.cookie</span> = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.sender</span>_pid = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.sender</span>_euid = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>const status_t err = data<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.errorCheck</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>if (err == NO_ERROR) {tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.data</span>_size = data<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ipcDataSize</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.data</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ptr</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.buffer</span> = data<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ipcData</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.offsets</span>_size = data<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ipcObjectsCount</span>()*sizeof(size_t)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.data</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ptr</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.offsets</span> = data<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ipcObjects</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>} else if (statusBuffer) {tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.flags</span> |= TF_STATUS_CODE<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>*statusBuffer = err<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.data</span>_size = sizeof(status_t)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.data</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ptr</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.buffer</span> = statusBuffer<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.offsets</span>_size = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>tr<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.data</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.ptr</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.offsets</span> = NULL<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>} else {return (mLastError = err)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}mOut<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.writeInt</span>32(cmd)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mOut<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.write</span>(&tr, sizeof(tr))<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>return NO_ERROR<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span> }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li></ul>

在寫入數據之前，我們首先對BpBinder進行了標識，在這里我們看到了之前所說的handle值，這樣印證了之前一篇博客中所說的BBinder和BpBinder是由handle值來相互標識的。

2.等待回應：

<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">status_t IPCThreadState::waitForResponse(Parcel *reply, status_t *acquireResult) {int32_t cmd;int32_t err;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//talkWithDriver重要函數之一，負責從Binder中讀寫數據</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((err=talkWithDriver()) < NO_ERROR) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;err = mIn.errorCheck();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err < NO_ERROR) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (mIn.dataAvail() == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>;cmd = mIn.readInt32();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (cmd) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_TRANSACTION_COMPLETE:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//發送完一個數據包后，可以收到該消息做為成功發送的反饋。</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!reply && !acquireResult) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_DEAD_REPLY:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//交互過程中如果發現對方進程或線程已經死亡</span>err = DEAD_OBJECT;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_FAILED_REPLY:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//發送失敗</span>err = FAILED_TRANSACTION;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_ACQUIRE_RESULT:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//獲得結果</span>{<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> int32_t result = mIn.readInt32();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (!acquireResult) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>;*acquireResult = result ? NO_ERROR : INVALID_OPERATION;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_REPLY:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//當前接收的數據是回復</span>{binder_transaction_data tr;err = mIn.read(&tr, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(tr));ALOG_ASSERT(err == NO_ERROR, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Not enough command data for brREPLY"</span>);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err != NO_ERROR) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (reply) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((tr.flags & TF_STATUS_CODE) == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {reply->ipcSetDataReference(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> uint8_t*>(tr.data.ptr.buffer),tr.data_size,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> size_t*>(tr.data.ptr.offsets),tr.offsets_size/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(size_t),freeBuffer, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {err = *<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> status_t*>(tr.data.ptr.buffer);freeBuffer(NULL,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> uint8_t*>(tr.data.ptr.buffer),tr.data_size,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> size_t*>(tr.data.ptr.offsets),tr.offsets_size/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(size_t), <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);}} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {freeBuffer(NULL,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> uint8_t*>(tr.data.ptr.buffer),tr.data_size,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> size_t*>(tr.data.ptr.offsets),tr.offsets_size/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(size_t), <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">continue</span>;}}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">default</span>:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//第二個重要函數，處理命令</span>err = executeCommand(cmd);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err != NO_ERROR) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">goto</span> finish;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;}}finish:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err != NO_ERROR) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (acquireResult) *acquireResult = err;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (reply) reply->setError(err);mLastError = err;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> err; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li></ul>

可以看到我們首先從Binder中讀寫數據，之后執行命令并返回結果狀態碼。

兩個重要函數

IPCThreadState有兩個重要的函數，talkWithDriver函數負責從Binder讀寫數據，executeCommand函數負責解析并執行mIn中的數據。?
1.talkWithDriver：

<code class="hljs lasso has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">status_t IPCThreadState<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;">::talkWithDriver</span>(bool doReceive) { <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//用來和Binder交換數據的結構</span>binder_write_read bwr;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 判斷數據是否為空</span>const bool needRead <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">mIn</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>dataPosition() <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">>=</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">mIn</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>dataSize();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 如果caller已經請求讀取下一行數據，或緩沖區中有數據沒讀完的時候我們不會進行任何寫操作</span>const size_t outAvail <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> (<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">!</span>doReceive <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">||</span> needRead) <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">?</span> mOut<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>dataSize() : <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//填充請求命令</span>bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_size <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> outAvail;bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_buffer <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> (long unsigned int)mOut<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span>();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (doReceive <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">&&</span> needRead) {bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_size <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">mIn</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>dataCapacity();bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_buffer <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> (long unsigned int)<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">mIn</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">data</span>();<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//mIn用來存儲接收的Binder數據</span>} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_size <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_buffer <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;} <span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-attribute" style="box-sizing: border-box;">...</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// 如果不需要任何操作了立即返回.</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_size <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">==</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">&&</span> (bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_size <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">==</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> NO_ERROR;bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_consumed <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_consumed <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;status_t err;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">do</span> { <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">#if</span> defined(HAVE_ANDROID_OS) <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//ioctl方式進行通信</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (ioctl(mProcess<span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">-></span>mDriverFD, BINDER_WRITE_READ, <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">&</span>bwr) <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">>=</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>)err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> NO_ERROR;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> <span class="hljs-attribute" style="box-sizing: border-box;">-errno</span>; <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">#else</span>err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">=</span> INVALID_OPERATION; <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">#endif</span>} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">==</span> <span class="hljs-attribute" style="box-sizing: border-box;">-EINTR</span>);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (err <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">>=</span> NO_ERROR) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_consumed <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_consumed <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;"><</span> (ssize_t)mOut<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>dataSize())mOut<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>remove(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>, bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>write_consumed);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span>mOut<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>setDataSize(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_consumed <span class="hljs-subst" style="color: rgb(0, 0, 0); box-sizing: border-box;">></span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">mIn</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>setDataSize(bwr<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>read_consumed);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">mIn</span><span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">.</span>setDataPosition(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> NO_ERROR;} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> err; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; 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position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; 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padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li></ul>

可以看到我們的Binder通信并不是采用的讀寫方式，而是ioctl方式，什么是ioctl方式呢？

ioctl是設備驅動程序中對設備的I/O通道進行管理的函數。所謂對I/O通道進行管理，就是對設備的一些特性進行控制，例如串口的傳輸波特率、馬達的 轉速等等。它的調用函數如下：int ioctl(int fd, ind cmd, …)；其中fd就是用戶程序打開設備時使用open函數返回的文件標示符，cmd就是用戶程序對設備的控制命令。

2.executeCommand函數：

<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">status_t IPCThreadState::executeCommand(int32_t cmd) {BBinder* obj;RefBase::weakref_type* refs;status_t result = NO_ERROR;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (cmd) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_ERROR:result = mIn.readInt32();<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_OK:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_ACQUIRE:refs = (RefBase::weakref_type*)mIn.readInt32();obj = (BBinder*)mIn.readInt32();obj->incStrong(mProcess.get()); mOut.writeInt32(BC_ACQUIRE_DONE);mOut.writeInt32((int32_t)refs);mOut.writeInt32((int32_t)obj);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_RELEASE:refs = (RefBase::weakref_type*)mIn.readInt32();obj = (BBinder*)mIn.readInt32();mPendingStrongDerefs.push(obj);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_INCREFS:refs = (RefBase::weakref_type*)mIn.readInt32();obj = (BBinder*)mIn.readInt32();refs->incWeak(mProcess.get());mOut.writeInt32(BC_INCREFS_DONE);mOut.writeInt32((int32_t)refs);mOut.writeInt32((int32_t)obj);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_DECREFS:refs = (RefBase::weakref_type*)mIn.readInt32();obj = (BBinder*)mIn.readInt32();mPendingWeakDerefs.push(refs);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_ATTEMPT_ACQUIRE:refs = (RefBase::weakref_type*)mIn.readInt32();obj = (BBinder*)mIn.readInt32();{<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">bool</span> success = refs->attemptIncStrong(mProcess.get());mOut.writeInt32(BC_ACQUIRE_RESULT);mOut.writeInt32((int32_t)success);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_TRANSACTION:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//當前接收的數據是請求</span>{binder_transaction_data tr;result = mIn.read(&tr, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(tr));<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (result != NO_ERROR) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;Parcel buffer;buffer.ipcSetDataReference(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> uint8_t*>(tr.data.ptr.buffer),tr.data_size,<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">reinterpret_cast</span><<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> size_t*>(tr.data.ptr.offsets),tr.offsets_size/<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">sizeof</span>(size_t), freeBuffer, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> pid_t origPid = mCallingPid;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> uid_t origUid = mCallingUid;mCallingPid = tr.sender_pid;mCallingUid = tr.sender_euid;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> curPrio = getpriority(PRIO_PROCESS, mMyThreadId);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (gDisableBackgroundScheduling) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (curPrio > ANDROID_PRIORITY_NORMAL) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//我們已經從caller實現了一個減小的優先級，但我們不希望它以這</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//種狀態運行在進程中。驅動已經設置了優先級，所以在開始事務</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//前首先將他設置為默認 </span>setpriority(PRIO_PROCESS, mMyThreadId, ANDROID_PRIORITY_NORMAL);}} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (curPrio >= ANDROID_PRIORITY_BACKGROUND) {androidSetThreadSchedulingGroup(mMyThreadId, ANDROID_TGROUP_BG_NONINTERACT);}}Parcel reply;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (tr.target.ptr) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//在這里我們看到了BBinder，還記得嗎，BBinder和BpBinder相對應，</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//是交互的目的端</span>sp<BBinder> b((BBinder*)tr.cookie);<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//在transact函數中調用了onTransact方法向reply寫入數據</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> status_t error = b->transact(tr.code, buffer, &reply, tr.flags);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (error < NO_ERROR) reply.setError(error);} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">else</span> {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">const</span> status_t error = the_context_object->transact(tr.code, buffer, &reply, tr.flags);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (error < NO_ERROR) reply.setError(error);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> ((tr.flags & TF_ONE_WAY) == <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>) {sendReply(reply, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>);} mCallingPid = origPid;mCallingUid = origUid; }<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_DEAD_BINDER:{BpBinder *proxy = (BpBinder*)mIn.readInt32();proxy->sendObituary();mOut.writeInt32(BC_DEAD_BINDER_DONE);mOut.writeInt32((int32_t)proxy);} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_CLEAR_DEATH_NOTIFICATION_DONE:{BpBinder *proxy = (BpBinder*)mIn.readInt32();proxy->getWeakRefs()->decWeak(proxy);} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_FINISHED:result = TIMED_OUT;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_NOOP:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> BR_SPAWN_LOOPER:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//用于接收方線程池管理。當驅動發現接收方所有線程都處于忙碌狀態且線</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//程池里的線程總數沒有超過BINDER_SET_MAX_THREADS設置的最大線程數 </span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//時，向接收方發送該命令要求創建更多線程以備接收數據。</span>mProcess->spawnPooledThread(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">false</span>);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">default</span>:<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">printf</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"*** BAD COMMAND %d received from Binder driver\n"</span>, cmd);result = UNKNOWN_ERROR;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (result != NO_ERROR) {mLastError = result;}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> result; }</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; 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padding: 0px 5px;">147</li><li style="box-sizing: border-box; padding: 0px 5px;">148</li><li style="box-sizing: border-box; padding: 0px 5px;">149</li><li style="box-sizing: border-box; padding: 0px 5px;">150</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; 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padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li><li style="box-sizing: border-box; padding: 0px 5px;">39</li><li style="box-sizing: border-box; padding: 0px 5px;">40</li><li style="box-sizing: border-box; padding: 0px 5px;">41</li><li style="box-sizing: border-box; padding: 0px 5px;">42</li><li style="box-sizing: border-box; padding: 0px 5px;">43</li><li style="box-sizing: border-box; padding: 0px 5px;">44</li><li style="box-sizing: border-box; padding: 0px 5px;">45</li><li style="box-sizing: border-box; padding: 0px 5px;">46</li><li style="box-sizing: border-box; padding: 0px 5px;">47</li><li style="box-sizing: border-box; padding: 0px 5px;">48</li><li style="box-sizing: border-box; padding: 0px 5px;">49</li><li style="box-sizing: border-box; padding: 0px 5px;">50</li><li style="box-sizing: border-box; padding: 0px 5px;">51</li><li style="box-sizing: border-box; padding: 0px 5px;">52</li><li style="box-sizing: border-box; padding: 0px 5px;">53</li><li style="box-sizing: border-box; padding: 0px 5px;">54</li><li style="box-sizing: border-box; padding: 0px 5px;">55</li><li style="box-sizing: border-box; padding: 0px 5px;">56</li><li style="box-sizing: border-box; padding: 0px 5px;">57</li><li style="box-sizing: border-box; padding: 0px 5px;">58</li><li style="box-sizing: border-box; padding: 0px 5px;">59</li><li style="box-sizing: border-box; padding: 0px 5px;">60</li><li style="box-sizing: border-box; padding: 0px 5px;">61</li><li style="box-sizing: border-box; padding: 0px 5px;">62</li><li style="box-sizing: border-box; padding: 0px 5px;">63</li><li style="box-sizing: border-box; padding: 0px 5px;">64</li><li style="box-sizing: border-box; padding: 0px 5px;">65</li><li style="box-sizing: border-box; padding: 0px 5px;">66</li><li style="box-sizing: border-box; padding: 0px 5px;">67</li><li style="box-sizing: border-box; padding: 0px 5px;">68</li><li style="box-sizing: border-box; padding: 0px 5px;">69</li><li style="box-sizing: border-box; padding: 0px 5px;">70</li><li style="box-sizing: border-box; padding: 0px 5px;">71</li><li style="box-sizing: border-box; padding: 0px 5px;">72</li><li style="box-sizing: border-box; padding: 0px 5px;">73</li><li style="box-sizing: border-box; padding: 0px 5px;">74</li><li style="box-sizing: border-box; padding: 0px 5px;">75</li><li style="box-sizing: border-box; padding: 0px 5px;">76</li><li style="box-sizing: border-box; padding: 0px 5px;">77</li><li style="box-sizing: border-box; padding: 0px 5px;">78</li><li style="box-sizing: border-box; padding: 0px 5px;">79</li><li style="box-sizing: border-box; padding: 0px 5px;">80</li><li style="box-sizing: border-box; padding: 0px 5px;">81</li><li style="box-sizing: border-box; padding: 0px 5px;">82</li><li style="box-sizing: border-box; padding: 0px 5px;">83</li><li style="box-sizing: border-box; padding: 0px 5px;">84</li><li style="box-sizing: border-box; padding: 0px 5px;">85</li><li style="box-sizing: border-box; padding: 0px 5px;">86</li><li style="box-sizing: border-box; padding: 0px 5px;">87</li><li style="box-sizing: border-box; padding: 0px 5px;">88</li><li style="box-sizing: border-box; padding: 0px 5px;">89</li><li style="box-sizing: border-box; padding: 0px 5px;">90</li><li style="box-sizing: border-box; padding: 0px 5px;">91</li><li style="box-sizing: border-box; padding: 0px 5px;">92</li><li style="box-sizing: border-box; padding: 0px 5px;">93</li><li style="box-sizing: border-box; padding: 0px 5px;">94</li><li style="box-sizing: border-box; padding: 0px 5px;">95</li><li style="box-sizing: border-box; padding: 0px 5px;">96</li><li style="box-sizing: border-box; padding: 0px 5px;">97</li><li style="box-sizing: border-box; padding: 0px 5px;">98</li><li style="box-sizing: border-box; padding: 0px 5px;">99</li><li style="box-sizing: border-box; padding: 0px 5px;">100</li><li style="box-sizing: border-box; padding: 0px 5px;">101</li><li style="box-sizing: border-box; padding: 0px 5px;">102</li><li style="box-sizing: border-box; padding: 0px 5px;">103</li><li style="box-sizing: border-box; padding: 0px 5px;">104</li><li style="box-sizing: border-box; padding: 0px 5px;">105</li><li style="box-sizing: border-box; padding: 0px 5px;">106</li><li style="box-sizing: border-box; padding: 0px 5px;">107</li><li style="box-sizing: border-box; padding: 0px 5px;">108</li><li style="box-sizing: border-box; padding: 0px 5px;">109</li><li style="box-sizing: border-box; padding: 0px 5px;">110</li><li style="box-sizing: border-box; padding: 0px 5px;">111</li><li style="box-sizing: border-box; padding: 0px 5px;">112</li><li style="box-sizing: border-box; padding: 0px 5px;">113</li><li style="box-sizing: border-box; padding: 0px 5px;">114</li><li style="box-sizing: border-box; padding: 0px 5px;">115</li><li style="box-sizing: border-box; padding: 0px 5px;">116</li><li style="box-sizing: border-box; padding: 0px 5px;">117</li><li style="box-sizing: border-box; padding: 0px 5px;">118</li><li style="box-sizing: border-box; padding: 0px 5px;">119</li><li style="box-sizing: border-box; padding: 0px 5px;">120</li><li style="box-sizing: border-box; padding: 0px 5px;">121</li><li style="box-sizing: border-box; padding: 0px 5px;">122</li><li style="box-sizing: border-box; padding: 0px 5px;">123</li><li style="box-sizing: border-box; padding: 0px 5px;">124</li><li style="box-sizing: border-box; padding: 0px 5px;">125</li><li style="box-sizing: border-box; padding: 0px 5px;">126</li><li style="box-sizing: border-box; padding: 0px 5px;">127</li><li style="box-sizing: border-box; padding: 0px 5px;">128</li><li style="box-sizing: border-box; padding: 0px 5px;">129</li><li style="box-sizing: border-box; padding: 0px 5px;">130</li><li style="box-sizing: border-box; padding: 0px 5px;">131</li><li style="box-sizing: border-box; padding: 0px 5px;">132</li><li style="box-sizing: border-box; padding: 0px 5px;">133</li><li style="box-sizing: border-box; padding: 0px 5px;">134</li><li style="box-sizing: border-box; padding: 0px 5px;">135</li><li style="box-sizing: border-box; padding: 0px 5px;">136</li><li style="box-sizing: border-box; padding: 0px 5px;">137</li><li style="box-sizing: border-box; padding: 0px 5px;">138</li><li style="box-sizing: border-box; padding: 0px 5px;">139</li><li style="box-sizing: border-box; padding: 0px 5px;">140</li><li style="box-sizing: border-box; padding: 0px 5px;">141</li><li style="box-sizing: border-box; padding: 0px 5px;">142</li><li style="box-sizing: border-box; padding: 0px 5px;">143</li><li style="box-sizing: border-box; padding: 0px 5px;">144</li><li style="box-sizing: border-box; padding: 0px 5px;">145</li><li style="box-sizing: border-box; padding: 0px 5px;">146</li><li style="box-sizing: border-box; padding: 0px 5px;">147</li><li style="box-sizing: border-box; padding: 0px 5px;">148</li><li style="box-sizing: border-box; padding: 0px 5px;">149</li><li style="box-sizing: border-box; padding: 0px 5px;">150</li></ul>

在這里我們主要分析一下接收數據請求的情況：在這里我們看到了BBinder對象，并調用了它的transact函數，其實在內部調用了onTransact函數，而這個函數在BBinder中只是定義了兩種code之下的操作，大部分的情況是由它的子類完成。還記得上一篇中那個類的關系圖嗎：BBinder的直接子類是BnInterface，而這是一個接口類，所以所有的任務都落在了BnInterface的子類BnServiceManager中。

總結

看了這個類IPCThreadState，真的有點頭暈眼花，究其原因是：該類將代碼一部分給客戶端使用，一部分給服務端使用，所以有點雜亂?？偨Y一下今天學到的IPCThreadState的工作：

首先，通過線程本地存儲機制IPCThreadState將自身和線程本地存儲關聯起來；

通過writeTransactionData將發生的數據存儲在mOut中；

waitForResponse調用了talkWithDriver從Binder設備中讀寫數據，在這里采用的是ioctl方式；

調用executeCommand函數解析并執行mIn中的數據。

原文地址：?http://blog.csdn.net/smbroe/article/details/44725143

總結

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