2014年2月26日 星期三

IPC(socket)

from:http://jimmychenhaha.blogspot.tw/2012/12/ipcsocket.html

網路找到的範例: 很不錯

http://www.cs.cf.ac.uk/Dave/C/node28.html

source code:
https://docs.google.com/folder/d/0B8hm-I2M8BD7TkVJcGtHQUM3MTg/edit

server.c 


#include
#include
#include
#include

#define NSTRS       3           /* no. of strings  */
#define ADDRESS     "mysocket"  /* addr to connect */

/*
 * Strings we send to the client.
 */
char *strs[NSTRS] = {
    "This is the first string from the server.\n",
    "This is the second string from the server.\n",
    "This is the third string from the server.\n"
};

main()
{
    char c;
    FILE *fp;
    int fromlen;
    register int i, s, ns, len;
    struct sockaddr_un saun, fsaun;

    /*
     * Get a socket to work with.  This socket will
     * be in the UNIX domain, and will be a
     * stream socket.
     */
    if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
        perror("server: socket");
        exit(1);
    }

    /*
     * Create the address we will be binding to.
     */
    saun.sun_family = AF_UNIX;
    strcpy(saun.sun_path, ADDRESS);

    /*
     * Try to bind the address to the socket.  We
     * unlink the name first so that the bind won't
     * fail.
     *
     * The third argument indicates the "length" of
     * the structure, not just the length of the
     * socket name.
     */
    unlink(ADDRESS);
    len = sizeof(saun.sun_family) + strlen(saun.sun_path);

    if (bind(s, &saun, len) < 0) {
        perror("server: bind");
        exit(1);
    }

    /*
     * Listen on the socket.
     */
    if (listen(s, 5) < 0) {
        perror("server: listen");
        exit(1);
    }

    /*
     * Accept connections.  When we accept one, ns
     * will be connected to the client.  fsaun will
     * contain the address of the client.
     */
    if ((ns = accept(s, &fsaun, &fromlen)) < 0) {
        perror("server: accept");
        exit(1);
    }

    /*
     * We'll use stdio for reading the socket.
     */
    fp = fdopen(ns, "r");

    /*
     * First we send some strings to the client.
     */
    for (i = 0; i < NSTRS; i++)
        send(ns, strs[i], strlen(strs[i]), 0);

    /*
     * Then we read some strings from the client and
     * print them out.
     */
    for (i = 0; i < NSTRS; i++) {
        while ((c = fgetc(fp)) != EOF) {
            putchar(c);

            if (c == '\n')
                break;
        }
    }

    /*
     * We can simply use close() to terminate the
     * connection, since we're done with both sides.
     */
    close(s);

    exit(0);
}



client.c

#include
#include
#include
#include

#define NSTRS       3           /* no. of strings  */
#define ADDRESS     "mysocket"  /* addr to connect */

/*
 * Strings we send to the server.
 */
char *strs[NSTRS] = {
    "This is the first string from the client.\n",
    "This is the second string from the client.\n",
    "This is the third string from the client.\n"
};

main()
{
    char c;
    FILE *fp;
    register int i, s, len;
    struct sockaddr_un saun;

    /*
     * Get a socket to work with.  This socket will
     * be in the UNIX domain, and will be a
     * stream socket.
     */
    if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) {
        perror("client: socket");
        exit(1);
    }

    /*
     * Create the address we will be connecting to.
     */
    saun.sun_family = AF_UNIX;
    strcpy(saun.sun_path, ADDRESS);

    /*
     * Try to connect to the address.  For this to
     * succeed, the server must already have bound
     * this address, and must have issued a listen()
     * request.
     *
     * The third argument indicates the "length" of
     * the structure, not just the length of the
     * socket name.
     */
    len = sizeof(saun.sun_family) + strlen(saun.sun_path);

    if (connect(s, &saun, len) < 0) {
        perror("client: connect");
        exit(1);
    }

    /*
     * We'll use stdio for reading
     * the socket.
     */
    fp = fdopen(s, "r");

    /*
     * First we read some strings from the server
     * and print them out.
     */
    for (i = 0; i < NSTRS; i++) {
        while ((c = fgetc(fp)) != EOF) {
            putchar(c);

            if (c == '\n')
                break;
        }
    }

    /*
     * Now we send some strings to the server.
     */
    for (i = 0; i < NSTRS; i++)
        send(s, strs[i], strlen(strs[i]), 0);

    /*
     * We can simply use close() to terminate the
     * connection, since we're done with both sides.
     */
    close(s);

    exit(0);
}

IPC (share memory)

From:http://jimmychenhaha.blogspot.tw/2012/10/ipcshare-memory.html

[Function]

#include
int shmget(key_t key, size_t size, int shmflg);

key:
      IPC_PRIVATE:產生一個新的共享記憶體分段

size:
      需要共享記憶體的大小 , 因為分配大小皆以page為單位 , 所以如果size = 1~4096 , 則實際上會分配到4k.

shmflag:
      S_IRUSR: 讀記憶體分段
      S_IWUSR: 寫記憶體分段
      IPC_CREAT :確保開啟的記憶體是新的,而不是現存的記憶體.
      | 0666 : 作為校驗 ,  ubuntu要加

<shmat>
#include
void *shmat(int shmid, const void *shmaddr, int shmflg);

shmid:
          共享記憶體的id

shmaddr:
     NULL:讓系統自己選擇.

shmflg:
     SHM_RDONLY:唯讀模式
          0:可讀可寫

<shmdt>          

#include
int shmdt(const void *shmaddr);
<shmctl>
 #include
#include
 int shmctl(int shmid, int cmd, struct shmid_ds *buf);
shmid:
           share memory id
cmd:
          IPC_STAT: 從共享記憶體裡,拿 shmid_ds 結構資料給 buf.
          IPC_SET: 從buf 複製到共享記憶體
          IPC_RMID: 砍了共享記憶體
buf:
        就暫存區.

[CODE] 


#include
#include
#include
#include
#include
#define shm_size     32
#define PARM IPC_CREAT | 0666
int main(void)
{
    char c;
    int shm_id;
    char *shm_addr, *s;
 key_t key;

 key = 5679;
    if ((shm_id = shmget(key, shm_size, PARM)) < 0) {
        perror("shmget");
        return 0;
    }
    if ((shm_addr = shmat(shm_id, NULL, 0)) == (char *) -1) {
        perror("shmat");
        return 1;
    }
    s = shm_addr;
    for (c = 'a'; c <= 'z'; c++)
        *s++ = c;
    *s = NULL;

    while (*shm_addr != '*'){
        sleep(1);
 }

 shmdt(shm_addr);
 shmctl(shm_id , IPC_RMID , NULL);
    return 0;
}

#include
#include
#include
#include
#include
#define shm_size     32
int main(void)
{
    int shmid;
    key_t key;
    char *shm, *s;
    key = 5679;
    if ((shmid = shmget(key, shm_size , S_IRUSR | 0666)) < 0) {
        perror("shmget");
        return 1;
    }
    if ((shm = shmat(shmid, NULL, 0)) == (char *) -1) {
        perror("shmat");
        return 1;
    }
    for (s = shm; *s != NULL; s++)
        putchar(*s);
    putchar('\n');
    *shm = '*';

 return 0;
}


[編譯]
gcc -o server shm_server.c
gcc -o client shm_client.c
./server &
./client &

最後顯示
 haha@haha-VirtualBox:~/work$ abcdefghijklmnopqrstuvwxyz


ref:http://systw.net/note/af/sblog/more.php?reply=ok&id=235&tl=no

2014年2月18日 星期二

JSON (JavaScript Object Notation) Format

完整的JSON寫法:

01{
02  'familys' = [
03    {'name' 'Bruce',
04     'age' : 18,
05     'sex' 'male'},
06    {'name' 'Sherry',
07     'age' : 16,
08     'sex' 'famale'}
09  ]
10}

JSON會建構出兩種結構:(1)「"名稱" : 值」的集合;(2)Array。

JSON的細節

比對上面範例,你會發現一點也不難。

JSON Object:
  1. 以"{"開始,以"}"結尾
  2. 每個名稱後跟著一個":"
  3. 每對"名稱:值"之間用","分隔
1// 以"{"開始
2  'name' 'Bruce',  // 每個名稱後跟著一個":"
3  'age' : 18,        // 每對"名稱:值"之間用","分隔
4  'sex' 'male'
5// 以"}"結尾

JSON Array:
  1. 以"["開始,以"]"結尾
  2. 值之間使用","
01{
02  // familys為一維陣列,陣列裡包含兩筆物件資料
03  'familys' = [  // 以"["開始
04    {'name' 'Bruce',
05     'age' : 18,
06     'sex' 'male'},  // 值之間使用","
07    {'name' 'Sherry',
08     'age' : 16,
09     'sex' 'famale'}
10  // 以"]"結尾
11}

JSON Value:
  • 值本身可以是String、Number、true、false、null、ObjectArray

JSON String:
  • 由雙引號包圍的任意Unicode字元集合。可以使用"反斜線(\)"來轉義。
1{
2  "details" "這是JSON的值. \n 此格式比XML合適Ajax交換資料使用."
3}

JSON Number:
  • 與一般數值相同,除8 / 16進制外。

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