c program – Records And Memorys

December 31, 2018January 3, 2019

Pjsip note

pjsua的启动参数可以这样设置：

--id sip:12345@192.168.18.6 --registrar sip:192.168.18.6 --realm * --username alice --password 123456

1

--id sip:12345@192.168.18.6 --registrar sip:192.168.18.6 --realm * --username alice --password 123456

前提是服务器在 192.168.18.6 ，设置的来源是 pjsip手册：

https://www.pjsip.org/pjsua.htm

设置以后，在手机上用zoiper 注册到 192.168.18.6 ，然后用pjsua 程序先 m 命令，再输入：

sip:alice@192.168.18.5:36876

1

sip:alice@192.168.18.5:36876

就可以打电话到手机， 192.168.18.5:36876 是注册以后，在服务器看到的当前用户信息。
pjsua 重要的结构

a) endpoint

/**
 * The SIP endpoint.
 */
struct pjsip_endpoint
{
    /** Pool to allocate memory for the endpoint. */
    pj_pool_t		*pool;

    /** Mutex for the pool, hash table, and event list/queue. */
    pj_mutex_t		*mutex;

    /** Pool factory. */
    pj_pool_factory	*pf;

    /** Name. */
    pj_str_t		 name;

    /** Timer heap. */
    pj_timer_heap_t	*timer_heap;

    /** Transport manager. */
    pjsip_tpmgr		*transport_mgr;

    /** Ioqueue. */
    pj_ioqueue_t	*ioqueue;

    /** Last ioqueue err */
    pj_status_t		 ioq_last_err;

    /** DNS Resolver. */
    pjsip_resolver_t	*resolver;

    /** Modules lock. */
    pj_rwmutex_t	*mod_mutex;

    /** Modules. */
    pjsip_module        *modules[PJSIP_MAX_MODULE];

    /** Module list, sorted by priority. */
    pjsip_module	 module_list;

    /** Capability header list. */
    pjsip_hdr		 cap_hdr;

    /** Additional request headers. */
    pjsip_hdr		 req_hdr;

    /** List of exit callback. */
    exit_cb		 exit_cb_list;
};

/**

* The SIP endpoint.

struct pjsip_endpoint

{

/** Pool to allocate memory for the endpoint. */

pj_pool_t *pool;

/** Mutex for the pool, hash table, and event list/queue. */

pj_mutex_t *mutex;

/** Pool factory. */

pj_pool_factory *pf;

/** Name. */

pj_str_t name;

/** Timer heap. */

pj_timer_heap_t *timer_heap;

/** Transport manager. */

pjsip_tpmgr *transport_mgr;

/** Ioqueue. */

pj_ioqueue_t *ioqueue;

/** Last ioqueue err */

pj_status_t ioq_last_err;

/** DNS Resolver. */

pjsip_resolver_t *resolver;

/** Modules lock. */

pj_rwmutex_t *mod_mutex;

/** Modules. */

pjsip_module *modules[PJSIP_MAX_MODULE];

/** Module list, sorted by priority. */

pjsip_module module_list;

/** Capability header list. */

pjsip_hdr cap_hdr;

/** Additional request headers. */

pjsip_hdr req_hdr;

/** List of exit callback. */

exit_cb exit_cb_list;

};

注意每个 endpoint 维护着一个 module 数组

December 30, 2018

visual studio Common macros for build commands and properties

编译时经常能看到这样的宏： $(SolutionDir)$(Configuration)\

在这个网址，能看到所有宏的详细解释 https://docs.microsoft.com/en-us/cpp/ide/common-macros-for-build-commands-and-properties?view=vs-2017

但是，如果能看到具体的路径，当然更明确了，那么，怎么看到？或者说，怎么把这些变量print 出来？

方法是：项目 properties—–>Build Event—-> pre 或者 post build event 都可以 —-> command line —-> edit ——> macro

就可以看到这些macro 的 name value pair

December 29, 2018December 30, 2018

c Notes

为什么 c 语言有static function

c++ class 有 static function 能理解，代表不用实例化类也可以调用的函数

c 并没有类的概念， static function 是什么意思？

—

解释： In C, functions are global by default. The “static” keyword before a function name makes it static.

Unlike global functions in C, access to static functions is restricted to the file where they are declared.

用代码说明：

/* Inside file1.c */

static void fun1(void)

{

puts("fun1 called");

}

/* Iinside file2.c  */
intmain(void) 
{ 
  fun1();  
  getchar(); 
  return0;   

Now, if we compile the above code with command “gcc file2.c file1.c”, we get the error “undefined reference to `fun1’” . This is because fun1() is declared static in file1.c and cannot be used in file2.c.

static variable

1) A static int variable remains in memory while the program is running. A normal or auto variable is destroyed when a function call where the variable was declared is over.

2) Static variables are allocated memory in data segment, not stack segment. See memory layout of C programs for details.

3) Static variables (like global variables) are initialized as 0 if not initialized explicitly. For example in the below program, value of x is printed as 0, while value of y is something garbage. See this for more details.

4) In C, static variables can only be initialized using constant literals. For example, following program fails in compilation. See this for more details.