cat函数解析

matlab的strcat函数MATLAB中的strcat函数是用于连接一串字符串的函数。

字符串是任何字符的序列。

可以通过单引号或双引号括起来创建字符串。

例如：```str1 = 'hello';str2 = "world";```MATLAB中提供了许多字符串相关的函数，包括连接字符串的strcat函数。

下面我们来详细地介绍一下strcat函数。

函数语法MATLAB中strcat函数的语法如下：```new_string = strcat(str1, str2, ..., strN)```str1, str2, ..., strN是要连接的字符串，new_string是输出的新字符串。

strcat 函数将输入的字符串按照顺序连接起来，并返回一个新的字符串，其中每个字符串之间没有空格或其他分隔符。

函数示例下面我们来看一些实际的例子，以便更好地理解strcat函数。

假设我们有三个字符串变量str1、str2和str3，分别存储了“hello”、“world”和“！”这三个字符串。

我们可以使用strcat函数将它们连接起来，得到新的字符串：运行以上代码，输出如下结果：我们也可以将多个字符串常量直接作为参数传递给strcat函数：这会得到的结果与上面的例子一样。

值得注意的是，如果要连接的字符串中存在空白字符（例如空格），则我们需要将其加入到参数中。

否则，任何相邻的字符串将相互粘合，使新字符串变得不可读。

例如：如果不记得在str1和str2之间添加空格，则输出结果将不可读：这将返回：我们可以在其中添加更多的字符串数组元素，以得到更长的字符串。

小结在MATLAB中使用strcat函数可以轻松地将多个字符串连接起来。

只需将它们作为参数传递给函数，就可以得到新的连接字符串。

需要注意的是，在连接含有空白字符的字符串时，需要考虑参数中的空白字符，这样可以避免输出结果不可读的问题。

右击POUs，添加一个FB功能块，相比于FUN,FB功能块有INPUT,OUTPUT,还有VAR，即FB可以有多个输出，但是整个FB没有返回值
实现相同的功能，FB要比FUN难看的多，FB要声明实例，此外注意前面是赋值符号（给FB的几个输入参数赋值，然后最后输出是=>符号，即把FB的某个输出参数灌给指定的主程序变量）
但是FB有一些别的好处，尤其是在写复杂算法的时候，FB可以整合很多算法到一个对象中，比如可以把角度转弧度，弧度转角度，开平方根，多次方等等基本函数放到统一的FB中管理，就可以使用类似于面向对象的写法来访问类的方法，比FUN更加方便。

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在前面两篇文章Android日志系统驱动程序Logger源代码分析和Android应用程序框架层和系统运行库层日志系统源代码中，介绍了Android内核空间层、系统运行库层和应用程序框架层日志系统相关的源代码，其中，后一篇文章着重介绍了日志的写入操作。

为了描述完整性，这篇文章着重介绍日志的读取操作，这就是我们在开发Android应用程序时，经常要用到日志查看工具Logcat了。

Logcat工具内置在Android系统中，可以在主机上通过adb logcat命令来查看模拟机上日志信息。

Logcat工具的用法很丰富，因此，源代码也比较多，本文并不打算完整地介绍整个Logcat工具的源代码，主要是介绍Logcat读取日志的主线，即从打开日志设备文件到读取日志设备文件的日志记录到输出日志记录的主要过程，希望能起到一个抛砖引玉的作用。

Logcat工具源代码位于system/core/logcat目录下，只有一个源代码文件logcat.cpp，编译后生成的可执行文件位于out/target/product/generic/system/bin目录下，在模拟机中，可以在/system/bin目录下看到logcat工具。

下面我们就分段来阅读logcat.cpp源代码文件。

一. Logcat工具的相关数据结构。

这些数据结构是用来保存从日志设备文件读出来的日志记录：view plain1.struct queued_entry_t {2.union {3. unsigned char buf[LOGGER_ENTRY_MAX_LEN + 1] __attribute__((aligned(4)));4.struct logger_entry entry __attribute__((aligned(4)));5. };6. queued_entry_t* next;7.8. queued_entry_t() {9. next = NULL;10. }11.};12.13.struct log_device_t {14.char* device;15.bool binary;16.int fd;17.bool printed;18.char label;19.20. queued_entry_t* queue;21. log_device_t* next;22.23. log_device_t(char* d, bool b, char l) {24. device = d;25. binary = b;26. label = l;27. queue = NULL;28. next = NULL;29. printed = false;30. }31.32.void enqueue(queued_entry_t* entry) {33.if (this->queue == NULL) {34.this->queue = entry;35. } else {36. queued_entry_t** e = &this->queue;37.while (*e && cmp(entry, *e) >= 0) {38. e = &((*e)->next);39. }40. entry->next = *e;41. *e = entry;42. }43. }44.};其中，宏LOGGER_ENTRY_MAX_LEN和struct logger_entry定义在system/core/include/cutils/logger.h文件中，在Android应用程序框架层和系统运行库层日志系统源代码分析一文有提到，为了方便描述，这里列出这个宏和结构体的定义：view plain1.struct logger_entry {2. __u16 len; /* length of the payload */3. __u16 __pad; /* no matter what, we get 2 bytes of padding */4. __s32 pid; /* generating process's pid */5. __s32 tid; /* generating process's tid */6. __s32 sec; /* seconds since Epoch */7. __s32 nsec; /* nanoseconds */8.char msg[0]; /* the entry's payload */9.};10.11.#define LOGGER_ENTRY_MAX_LEN (4*1024)从结构体struct queued_entry_t和struct log_device_t的定义可以看出，每一个log_device_t都包含有一个queued_entry_t队列，queued_entry_t就是对应从日志设备文件读取出来的一条日志记录了，而log_device_t则是对应一个日志设备文件上下文。

1．为什么要引入构造函数和析构函数？对象的初始化是指对象数据成员的初始化，在使用对象前，一定要初始化。

由于数据成员一般为私有的(private)，所以不能直接赋值。

对对象初始化有以下两种方法：类中提供一个普通成员函数来初始化，但是会造成使用上的不便（使用对象前必须显式调用该函数）和不安全(未调用初始化函数就使用对象)。

当定义对象时，编译程序自动调用构造函数。

析构函数的功能是当对象被撤消时，释放该对象占用的内存空间。

析构函数的作用与构造函数正好相反，一般情况下，析构函数执行构造函数的逆操作。

在对象消亡时，系统将自动调用析构函数，执行一些在对象撤消前必须执行的清理任务。

2. 类的公有、私有和保护成员之间的区别是什么？①私有成员private: 私有成员是在类中被隐藏的部分，它往往是用来描述该类对象属性的一些数据成员，私有成员只能由本类的成员函数或某些特殊说明的函数（如第4章讲到的友员函数）访问，而类的外部根本就无法访问，实现了访问权限的有效控制，使数据得到有效的保护，有利于数据的隐藏，使内部数据不能被任意的访问和修改，也不会对该类以外的其余部分造成影响，使模块之间的相互作用被降低到最小。

private成员若处于类声明中的第一部分，可省略关键字private。

②公有成员public：公有成员对外是完全开放的，公有成员一般是成员函数，它提供了外部程序与类的接口功能，用户通过公有成员访问该类对象中的数据。

③保护成员protected: 只能由该类的成员函数，友元，公有派生类成员函数访问的成员。

保护成员与私有成员在一般情况下含义相同，它们的区别体现在类的继承中对产生的新类的影响不同，具体内容将在第5章中介绍。

缺省访问控制（未指定private、protected、public访问权限）时，系统认为是私有private 成员。

3. 什么是拷贝构造函数，它何时被调用？拷贝构造函数的功能是用一个已有的对象来初始化一个被创建的同类对象，是一种特殊的构造函数，具有一般构造函数的所有特性，当创建一个新对象时系统自动调用它；其形参是本类对象的引用，它的特殊功能是将参数代表的对象逐域拷贝到新创建的对象中。

varcat函数同花顺
在同花顺软件中，自定义函数可以通过以下步骤创建:
1. 打开同花顺软件，点击“文件”菜单，选择“选项”。

2. 在“选项”对话框中，选择“自定义功能区”。

3. 在“自定义功能区”中，勾选“开发工具”选项卡，点击“确定”。

4. 在“开发工具”选项卡下，选择“Visual Basic”选项。

5. 在“Visual Basic”中，选择“插入”菜单，选择“模块”。

6. 在新建的模块中，编写自定义函数的代码，符合 VBA 语法规范，且函数的返回值与函数名称一致。

7. 编写完毕后，保存模块，返回同花顺软件。

8. 在同花顺软件中，输入自定义函数的名称和参数，即可使用自定义函数。

需要注意的是，自定义函数的代码需要符合 VBA 语法规范，且函数的返回值需要与函数名称一致。

同时，如果需要在同花顺软件中使用自定义函数，需要在同花顺软件中进行设置，具体方法可以参考同花顺软件的使用说明。

C标准库源码解剖(4)字符串处理函数stringh和wcharh tring.h中包含了所有的字符串处理函数，也包含了内存处理函数，因为这些内存处理函数（如比如、复制、搜索）的功能与字符串处理函数功能类似。

我们是用通用指针来指向内存块的，通用指针可以用char某类型（传统C语言），也可以用void某类型（标准C语言）。

每个函数都有对应的宽字符版本，在wchar.h中。

tring.h中包含的标准库函数：trcat,trncat,trcmp,trncmp,trcpy,trncpy,trlen,trchr,trrchr,tr pn,trcpn,trpbrk,trtr,trok,trcoll,tr某frm,trerror;memcpy,memmove,memcmp,memchr,memeet。

GNU还提供了很多非标准的扩展，如memccpy,rawmemchr,memrchr,trdup,trndup等。

viewplaincopytoclipboardprint1./某ISOC99Standard:7.21字符串处理<tring.h>某/2.#ifndef_STRING_H3.#define_STRING_H14.#include<feature.h>/某非标准头文件，定义了一些编译选项某/5.__BEGIN_DECLS6./某从<tddef.h>中获得ize_t和NULL某/7.#define__need_ize_t8.#define__need_NULL9.#include<tddef.h>10.__BEGIN_NAMESPACE_STD11./某从SRC中复制N个字节的内容到DEST中某/12.e某ternvoid某memcpy(void某__retrict__det,13.__contvoid某__retrict__rc,ize_t__n)14.__THROW__nonnull((1,2));15./某从SRC中复制N个字节的内容到DEST中，保证对重叠字符串（即SRC与DEST共用存储空间）有正确的行为某/16.e某ternvoid某memmove(void某__det,__contvoid某__rc,ize_t__n)17.__THROW__nonnull((1,2));18.__END_NAMESPACE_STD19./某从SRC中复制不超过N个字节的内容到DEST中，当遇到字符C返回DEST中C的拷贝后面的字符指针。

inspect模块详解inspect模块主要提供了四种⽤处：(1).对是否是模块，框架，函数等进⾏类型检查。

(2).获取源码(3).获取类或函数的参数的信息(4).解析堆栈使⽤inspect模块可以提供⾃省功能，下⾯是关于⾃省的⼀些介绍:　⾸先通过⼀个例⼦来看⼀下本⽂中可能⽤到的对象和相关概念。

#coding: UTF-8import sys #模块，sys指向这个模块对象import inspectdef foo(): pass#函数，foo指向这个函数对象class Cat(object): #类，Cat指向这个类对象def__init__(self, name='kitty'): = namedef sayHi(self): #实例⽅法，sayHi指向这个⽅法对象，使⽤类或实例.sayHi访问print , 'says Hi!'#访问名为name的字段，使⽤实例.name访问cat = Cat() # cat是Cat类的实例对象print Cat.sayHi #使⽤类名访问实例⽅法时，⽅法是未绑定的(unbound)print cat.sayHi #使⽤实例访问实例⽅法时，⽅法是绑定的(bound)有时候我们会碰到这样的需求，需要执⾏对象的某个⽅法，或是需要对对象的某个字段赋值，⽽⽅法名或是字段名在编码代码时并不能确定，需要通过参数传递字符串的形式输⼊。

举个具体的例⼦：当我们需要实现⼀个通⽤的DBM框架时，可能需要对数据对象的字段赋值，但我们⽆法预知⽤到这个框架的数据对象都有些什么字段，换⾔之，我们在写框架的时候需要通过某种机制访问未知的属性。

这个机制被称为反射（反过来让对象告诉我们他是什么），或是⾃省（让对象⾃⼰告诉我们他是什么，好吧我承认括号⾥是我瞎掰的- -#），⽤于实现在运⾏时获取未知对象的信息。

反射是个很吓唬⼈的名词，听起来⾼深莫测，在⼀般的编程语⾔⾥反射相对其他概念来说稍显复杂，⼀般来说都是作为⾼级主题来讲；但在Python中反射⾮常简单，⽤起来⼏乎感觉不到与其他的代码有区别，使⽤反射获取到的函数和⽅法可以像平常⼀样加上括号直接调⽤，获取到类后可以直接构造实例；不过获取到的字段不能直接赋值，因为拿到的其实是另⼀个指向同⼀个地⽅的引⽤，赋值只能改变当前的这个引⽤⽽已。

AdsGetDllVersionReturns the version number, revision number and build number of the ADS-DLL.LONG AdsGetDllVersion(void);Parameter-Return valueThe return value, which is of type long, contains in coded form these three items related to the ADS-DLL.AdsPortOpenEstablishes a connection (communication port) to the TwinCAT message router.LONG AdsPortOpen(void);Parameter-Return valueA port number that has been assigned to the program by the ADS router is returned.AdsPortCloseThe connection (communication port) to the TwinCAT message router is closed.LONG AdsPortClose(void);Parameter-Return valueReturns the function's error status.AdsGetLocalAddressReturns the local NetId and port number. LONG AdsGetLocalAddress(PAmsAddr pAddr);ParameterpAddr[out] Pointer to the structure of type AmsAddr. Return valueReturns the function's error status.AdsSyncWriteReqWrites data synchronously to an ADS device. LONG AdsSyncWriteReq(PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nLength,PVOID pData);ParameterpAddr[in] Structure with NetId and port number of the ADS server. nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nLength[in] Length of the data, in bytes, written to the ADS server. pData[in] Pointer to the data written to the ADS server.Return valueReturns the function's error status.AdsSyncReadReqReads data synchronously from an ADS server.LONG AdsSyncReadReq(PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nLength,PVOID pData);ParameterpAddr[in] Structure with NetId and port number of the ADS server. nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nLength[in] Length of the data in bytes.pData[out] Pointer to a data buffer that will receive the data.Return valueReturns the function's error status.AdsSyncReadReqExReads data synchronously from an ADS server.LONG AdsSyncReadReq(PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nLength,PVOID pData,ULONG*pcbReturn);ParameterpAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nLength[in] Length of the data in bytes.pData[out] Pointer to a data buffer that will receive the data.pcbReturn[out] Pointer to a variable. This variable returns the number of succesfully read data bytes. Return valueReturns the function's error status.Writes data synchronously into an ADS server and receives data back from the ADS device. LONG AdsSyncReadWriteReq(PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nReadLength,PVOID pReadData,ULONG nWriteLength,PVOID pWriteData);ParameterpAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nReadLength[in] Length of the data, in bytes, returned by the ADS device.pReadData[out] Buffer with data returned by the ADS device.nWriteLength[in] Length of the data, in bytes, written to the ADS device.pWriteData[out] Buffer with data written to the ADS device.Return valueReturns the function's error status.AdsSyncReadWriteReqExWrites data synchronously into an ADS server and receives data back from the ADS device.PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nReadLength,PVOID pReadData,ULONG nWriteLength,PVOID pWriteData,ULONG*pcbReturn);ParameterpAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nReadLength[in] Length of the data, in bytes, returned by the ADS device.pReadData[out] Buffer with data returned by the ADS device.nWriteLength[in] Length of the data, in bytes, written to the ADS device.pWriteData[out] Buffer with data written to the ADS device.pcbReturn[out] Pointer to a variable. This variable returns the number of succesfully read data bytes.AdsSyncReadDeviceInfoReqReads the identification and version number of an ADS server.LONG AdsSyncReadDeviceInfoReq(PAmsAddr pAddr,PCHAR pDevName,PAdsVersion pVersion);ParameterpAddr[in] Structure with NetId and port number of the ADS server.pDevName[out] Pointer to a character string that will receive the name of the ADS device.pVersion[out] Address of a variable of type AdsVersion, which will receive the version number, revision number and the build number.Return valueReturns the function's error status.AdsSyncWriteControlReqChanges the ADS status and the device status of an ADS server.LONG AdsSyncWriteControlReq(PAmsAddr pAddr,USHORT nAdsState,USHORT nDeviceState,ULONG nLength,PVOID pData);ParameterpAddr[in] Structure with NetId and port number of the ADS server.nAdsState[in] New ADS status.nDeviceState[in] New device status.nLength[in] Length of the data in bytes.pData[in] Pointer to data sent additionally to the ADS device.Return valueReturns the function's error status.CommentsIn addition to changing the ADS status and the device status, it is also possible to send data to the ADS server in order to transfer further information. In the current ADS devices (PLC, NC, ...) this data has no further effect. Any ADS device can inform another ADS device of its current state. A distinction is drawn here between the status of the device itself (DeviceState) and the status of the ADS interface of the ADS device (AdsState). The states that the ADS interface can adopt are laid down in the ADS specification.AdsSyncReadStateReqReads the ADS status and the device status from an ADS server.LONG AdsSyncReadStateReq(PAmsAddr pAddr,USHORT *pAdsState,PUSHORT pDeviceState);ParameterpAddr[in] Structure with NetId and port number of the ADS server.pAdsState[out] Address of a variable that will receive the ADS status (see data type ADSSTATE).pDeviceState[out] Address of a variable that will receive the device status.Return valueReturns the function's error status.RemarksAny ADS device can inform another ADS device of its current state. A distinction is drawn here between the status of the device itself (DeviceState) and the status of the ADS interface of the ADS device (AdsState). The states that the ADS interface can adopt are laid down in the ADS specification.AdsSyncAddDeviceNotificationReqA notification is defined within an ADS server (e.g. PLC). When a certain event occurs a function (the callback function) is invoked in the ADS client (C program).LONG AdsSyncAddDeviceNotificationReq(PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,PAdsNotificationAttrib pNoteAttrib,PAdsNotificationFuncEx pNoteFunc,ULONG hUser,PULONG pNotification);ParameterpAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] IndexGroup.nIndexOffset[in] IndexOffset.pNoteAttrib[in] Pointer to the structure that contains further information.pNoteFunc[in] Name of the callback function.hUser[in] 32-bit value that is passed to the callback function.pNotification[out] Address of the variable that will receive the handle of the notification.Return valueReturns the function's error status.Limitation:Per ADS-Port a limitted number of 550 notifications are available. AdsSyncDelDeviceNotificationReqA notification defined previously is deleted from an ADS server.LONG AdsSyncDelDeviceNotificationReq(PAmsAddr pAddr,ULONG hNotification);ParameterpAddr[in] Structure with NetId and port number of the ADS server.hNotification[out] Address of the variable that contains the handle of the notification.Return valueReturns the function's error status.AdsSyncSetTimeoutAlters the timeout for the ADS functions. The standard value is 5000 ms.LONG AdsSyncSetTimeout(LONG nMs,);ParameternMs[in] Timeout in ms.Return valueReturns the function's error status.AdsAmsRegisterRouterNotificationThe AdsAmsRegisterNotificationReq() function can be used to detect a change in the status of the TwinCAT router. The given callback function is invoked each time the status changes. Monitoring of the router's status is ended once more by the AdsAmsUnRegisterNotification() function.LONG AdsAmsRegisterRouterNotification(PAmsRouterNotificationFuncEx pNoteFunc );ParameterpNoteFunc[in] Name of the callback functionReturn valueReturns the function's error status.Hints:∙Implemented from TcAdsDLL File Version: 2.8.0.21 ( delivered with TwinCAT 2.9 Build > 941).∙ A connection to the TwinCAT-Router can be done, if TwinCAT has been installed on the local PC. The function delivers an error on a system without TwinCAT.AdsAmsUnRegisterRouterNotificationMonitoring the router's status is ended by the AdsAmsUnRegisterNotification() function. See also AdsAmsRegisterNotificationReq().LONG AdsAmsUnRegisterRouterNotification( void );Parameter-Return valueReturns the function's error status.Hints:∙Implemented from TcAdsDLL File Version: 2.8.0.21 ( delivered with TwinCAT 2.9 Build > 941).∙ A connection to the TwinCAT-Router can be done, if TwinCAT has been installed on the local PC. The function delivers an error on a system without TwinCAT.PAmsRouterNotificationFuncExType definition of the callback function required by the AdsAmsRegisterRouterNotification function. typedef void ( __stdcall *PAmsRouterNotificationFuncEx)( long nEvent );PAdsNotificationFuncExType definition of the callback function required by the AdsSyncAddDeviceNotificationReq function.typedef void (__stdcall *PAdsNotificationFuncEx)(AmsAddr* pAddr, AdsNotificationHeader* pNotification, unsigned long hUser );MMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMMAdsPortOpenExEstablishes a connection (communication port) to the TwinCAT message router. Unlike with AdsPortOpen, a new ADS port is opened each time. The extended Ads functions have to be used for communicating with this port. The port number returned by AdsPortOpenEx is transferred as parameter to these functions. If no TwinCAT MessageRouter is present, the AdsPortOpenEx function will fail. LONG AdsPortOpenEx(void);Parameters-Return valuePort number of the opened Ads port. A return value of 0 means the call has failed.AdsPortCloseExThe connection (communication port) to the TwinCAT message router is closed. The port to be closed must previously have been opened via an AdsPortOpenEx call.LONG AdsPortCloseEx(long nPort);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx.Return valueReturns the function's error status.AdsGetLocalAddressExReturns the local NetId and port number.LONG AdsGetLocalAddressEx(long portPAmsAddr pAddr);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[out] Pointer to the structure of type AmsAddr.Return valueReturns the function's error status.AdsSyncWriteReqExWrites data synchronously to an ADS device.LONG AdsSyncWriteReqEx(LONG port,PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nLength,PVOID pData);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nLength[in] Length of the data, in bytes, written to the ADS server.pData[in] Pointer to the data written to the ADS server.Return valueReturns the function's error status.AdsSyncReadReqEx2Reads data synchronously from an ADS server.LONG AdsSyncReadReqEx2(LONG port,PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nLength,PVOID pData,ULONG*pcbReturn);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nLength[in] Length of the data in bytes.pData[out] Pointer to a data buffer that will receive the data.pcbReturn[out] pointer to a variable. If successful, this variable will return the number of actually read data bytes.AdsSyncReadWriteReqEx2Writes data synchronously into an ADS server and receives data back from the ADS device.LONG AdsSyncReadWriteReqEx2(LONG port,PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,ULONG nReadLength,PVOID pReadData,ULONG nWriteLength,PVOID pWriteData,ULONG* pcbReturn);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] Index Group.nIndexOffset[in] Index Offset.nReadLength[in] Length of the data, in bytes, returned by the ADS device.pReadData[out] Buffer with data returned by the ADS device.nWriteLength[in] Length of the data, in bytes, written to the ADS device.pWriteData[out] Buffer with data written to the ADS device.pcbReturn[out] pointer to a variable. If successful, this variable will return the number of actually read data bytes.AdsSyncReadDeviceInfoReqExReads the identification and version number of an ADS server.LONG AdsSyncReadDeviceInfoReqEx(LONG p ort,PAmsAddr pAddr,PCHAR pDevName,PAdsVersion pVersion);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.pDevName[out] Pointer to a character string that will receive the name of the ADS device.pVersion[out] Address of a variable of type AdsVersion, which will receive the version number, revision number and the build number.Return valueReturns the function's error status.AdsSyncWriteControlReqExChanges the ADS status and the device status of an ADS server.LONG AdsSyncWriteControlReqEx(LONG port,PAmsAddr pAddr,USHORT nAdsState,USHORT nDeviceState,ULONG nLength,PVOID pData);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.nAdsState[in] New ADS status.nDeviceState[in] New device status.nLength[in] Length of the data in bytes.pData[in] Pointer to data sent additionally to the ADS device.Return valueReturns the function's error status.CommentsIn addition to changing the ADS status and the device status, it is also possible to send data to the ADS server in order to transfer further information. In the current ADS devices (PLC, NC, ...) this data has no further effect. Any ADS device can inform another ADS device of its current state. A distinction is drawn here between the status of the device itself (DeviceState) and the status of the ADS interface of the ADS device (AdsState). The states that the ADS interface can adopt are laid down in the ADS specification.AdsSyncReadStateReqExReads the ADS status and the device status from an ADS server.LONG AdsSyncReadStateReqEx(LONG port,PAmsAddr pAddr,USHORT *pAdsState,PUSHORT pDeviceState);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.pAdsState[out] Address of a variable that will receive the ADS status (see data type ADSSTATE).pDeviceState[out] Address of a variable that will receive the device status.Return valueReturns the function's error status.RemarksAny ADS device can inform another ADS device of its current state. A distinction is drawn here between the status of the device itself (DeviceState) and the status of the ADS interface of the ADS device (AdsState). The states that the ADS interface can adopt are laid down in the ADS specification. Example 11 illustrates how the change can be detected with the aid of a callback function.AdsSyncAddDeviceNotificationReqExA notification is defined within an ADS server (e.g. PLC). When a certain event occurs a function (the callback function) is invoked in the ADS client (C program).LONG AdsSyncAddDeviceNotificationReqEx(LONG port,PAmsAddr pAddr,ULONG nIndexGroup,ULONG nIndexOffset,PAdsNotificationAttrib pNoteAttrib,PAdsNotificationFuncEx pNoteFunc,ULONG hUser,PULONG pNotification);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.nIndexGroup[in] IndexGroup.nIndexOffset[in] IndexOffset.pNoteAttrib[in] Pointer to the structure that contains further information.pNoteFunc[in] Name of the callback function.hUser[in] 32-bit value that is passed to the callback function.pNotification[out] Address of the variable that will receive the handle of the notification.Return valueReturns the function's error status.Limitation:Per ADS-Port a limited number of 550 notifications are available.RemarksIf the TwinCAT router is stopped and then started again, the notifications become invalid. You can trap this event with the AdsAmsRegisterRouterNotification() function.AdsSyncDelDeviceNotificationReqExA notification defined previously is deleted from an ADS server.LONG AdsSyncDelDeviceNotificationReqEx(LONG port,PAmsAddr pAddr,ULONG hNotification);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. pAddr[in] Structure with NetId and port number of the ADS server.hNotification[out] Address of the variable that contains the handle of the notification.Return valueReturns the function's error status.AdsSyncSetTimeoutExAlters the timeout for the ADS functions. The standard value is 5000 ms.LONG AdsSyncSetTimeoutEx(LONG port,LONG nMs,);Parametersport[in] port number of an Ads port that had previously been opened with AdsPortOpenEx or AdsPortOpen. nMs[in] Timeout in ms.Return valueReturns the function's error status.。

androidlogd原理及实现⼀、logd介绍logd 是Android L版本提出来的概念，其作⽤是保存Android运⾏期间的log（⽇志）。

在Android L之前，log由kernel的ring buffer 保存，在Android L之后，log保存在⽤户空间。

1） logd进程启动系统启动到init函数时会解析init.rc⽂件，启动logd进程和logd-reinit（重新初始化logd）进程，init.rc⽂件中的相关内容如下：onload_persist_props_actionload_persist_propsstart logdstart logd-reinit在system/core/logd中的logd.rc⽂件中，启动logdservice和logd-reinit service，具体内容如下：service logd /system/bin/logdsocket logd stream 0666logd logdsocket logdr seqpacket0666 logd logdsocket logdw dgram 0222logd logdgroup root system readprocwritepid/dev/cpuset/system-background/tasksservice logd-reinit /system/bin/logd --reinitoneshotdisabledwritepid/dev/cpuset/system-background/tasks注：logd-reinit只会执⾏⼀次，logd和logd-reinit都会调⽤system/core/logd/main.cpp中的main函数，但logd-reinit通过netlink给logd进程发送reinit命令后就会退出。

2） logd 实现log管理主要原理是：上层应⽤（Android层）通过调⽤Log/Slog/Rlog中的v/d⽅法打印log，最终log会通过netlink传递给logd，logd会将log保存在内存中（由C++中的list容器管理，后续会介绍），logcat等log获取⼯具同样通过netlink⽅式从logd获取log。