信號(hào)量函數(shù)用法

生產(chǎn)者-消費(fèi)者問(wèn)題是一個(gè)經(jīng)典的進(jìn)程同步問(wèn)題，該問(wèn)題最早由Dijkstra提出，用以演示他提出的信號(hào)量機(jī)制。在同一個(gè)進(jìn)程地址空間內(nèi)執(zhí)行的兩個(gè)線程。生產(chǎn)者線程生產(chǎn)物品，然后將物品放置在一個(gè)空緩沖區(qū)中供消費(fèi)者線程消費(fèi)。消費(fèi)者線程從緩沖區(qū)中獲得物品，然后釋放緩沖區(qū)。當(dāng)生產(chǎn)者線程生產(chǎn)物品時(shí)，如果沒(méi)有空緩沖區(qū)可用，那么生產(chǎn)者線程必須等待消費(fèi)者線程釋放出一個(gè)空緩沖區(qū)。當(dāng)消費(fèi)者線程消費(fèi)物品時(shí)，如果沒(méi)有滿的緩沖區(qū)，那么消費(fèi)者線程將被阻塞，直到新的物品被生產(chǎn)出來(lái)。

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#include windows.h

#include iostream

const unsigned short SIZE_OF_BUFFER = 10; //緩沖區(qū)長(zhǎng)度

unsigned short ProductID = 0; //產(chǎn)品號(hào)

unsigned short ConsumeID = 0; //將被消耗的產(chǎn)品號(hào)

unsigned short in = 0; //產(chǎn)品進(jìn)緩沖區(qū)時(shí)的緩沖區(qū)下標(biāo)

unsigned short out = 0; //產(chǎn)品出緩沖區(qū)時(shí)的緩沖區(qū)下標(biāo)

int g_buffer[SIZE_OF_BUFFER]; //緩沖區(qū)是個(gè)循環(huán)隊(duì)列

bool g_continue = true; //控制程序結(jié)束

HANDLE g_hMutex; //用于線程間的互斥

HANDLE g_hFullSemaphore; //當(dāng)緩沖區(qū)滿時(shí)迫使生產(chǎn)者等待

HANDLE g_hEmptySemaphore; //當(dāng)緩沖區(qū)空時(shí)迫使消費(fèi)者等待

DWORD WINAPI Producer(LPVOID); //生產(chǎn)者線程

DWORD WINAPI Consumer(LPVOID); //消費(fèi)者線程

int main()

{

//創(chuàng)建各個(gè)互斥信號(hào)

g_hMutex = CreateMutex(NULL,FALSE,NULL);

g_hFullSemaphore = CreateSemaphore(NULL,SIZE_OF_BUFFER-1,SIZE_OF_BUFFER-1,NULL);

g_hEmptySemaphore = CreateSemaphore(NULL,0,SIZE_OF_BUFFER-1,NULL);

//調(diào)整下面的數(shù)值，可以發(fā)現(xiàn)，當(dāng)生產(chǎn)者個(gè)數(shù)多于消費(fèi)者個(gè)數(shù)時(shí)，

//生產(chǎn)速度快，生產(chǎn)者經(jīng)常等待消費(fèi)者；反之，消費(fèi)者經(jīng)常等待

const unsigned short PRODUCERS_COUNT = 3; //生產(chǎn)者的個(gè)數(shù)

const unsigned short CONSUMERS_COUNT = 1; //消費(fèi)者的個(gè)數(shù)

//總的線程數(shù)

const unsigned short THREADS_COUNT = PRODUCERS_COUNT+CONSUMERS_COUNT;

HANDLE hThreads[PRODUCERS_COUNT]; //各線程的handle

DWORD producerID[CONSUMERS_COUNT]; //生產(chǎn)者線程的標(biāo)識(shí)符

DWORD consumerID[THREADS_COUNT]; //消費(fèi)者線程的標(biāo)識(shí)符

//創(chuàng)建生產(chǎn)者線程

for (int i=0;iPRODUCERS_COUNT;++i){

hThreads[i]=CreateThread(NULL,0,Producer,NULL,0,producerID[i]);

if (hThreads[i]==NULL) return -1;

}

//創(chuàng)建消費(fèi)者線程

for (int i=0;iCONSUMERS_COUNT;++i){

hThreads[PRODUCERS_COUNT+i]=CreateThread(NULL,0,Consumer,NULL,0,consumerID[i]);

if (hThreads[i]==NULL) return -1;

}

while(g_continue){

if(getchar()){ //按回車(chē)后終止程序運(yùn)行

g_continue = false;

}

}

return 0;

}

//生產(chǎn)一個(gè)產(chǎn)品。簡(jiǎn)單模擬了一下，僅輸出新產(chǎn)品的ID號(hào)

void Produce()

{

std::cerr "Producing " ++ProductID " ... ";

std::cerr "Succeed" std::endl;

}

//把新生產(chǎn)的產(chǎn)品放入緩沖區(qū)

void Append()

{

std::cerr "Appending a product ... ";

g_buffer[in] = ProductID;

in = (in+1)%SIZE_OF_BUFFER;

std::cerr "Succeed" std::endl;

//輸出緩沖區(qū)當(dāng)前的狀態(tài)

for (int i=0;iSIZE_OF_BUFFER;++i){

std::cout i ": " g_buffer[i];

if (i==in) std::cout " -- 生產(chǎn)";

if (i==out) std::cout " -- 消費(fèi)";

std::cout std::endl;

}

}

//從緩沖區(qū)中取出一個(gè)產(chǎn)品

void Take()

{

std::cerr "Taking a product ... ";

ConsumeID = g_buffer[out];

out = (out+1)%SIZE_OF_BUFFER;

std::cerr "Succeed" std::endl;

//輸出緩沖區(qū)當(dāng)前的狀態(tài)

for (int i=0;iSIZE_OF_BUFFER;++i){

std::cout i ": " g_buffer[i];

if (i==in) std::cout " -- 生產(chǎn)";

if (i==out) std::cout " -- 消費(fèi)";

std::cout std::endl;

}

}

//消耗一個(gè)產(chǎn)品

void Consume()

{

std::cerr "Consuming " ConsumeID " ... ";

std::cerr "Succeed" std::endl;

}

//生產(chǎn)者

DWORD WINAPI Producer(LPVOID lpPara)

{

while(g_continue){

WaitForSingleObject(g_hFullSemaphore,INFINITE);

WaitForSingleObject(g_hMutex,INFINITE);

Produce();

Append();

Sleep(1500);

ReleaseMutex(g_hMutex);

ReleaseSemaphore(g_hEmptySemaphore,1,NULL);

}

return 0;

}

//消費(fèi)者

DWORD WINAPI Consumer(LPVOID lpPara)

{

while(g_continue){

WaitForSingleObject(g_hEmptySemaphore,INFINITE);

WaitForSingleObject(g_hMutex,INFINITE);

Take();

Consume();

Sleep(1500);

ReleaseMutex(g_hMutex);

ReleaseSemaphore(g_hFullSemaphore,1,NULL);

}

return 0;

如何用C語(yǔ)言實(shí)現(xiàn)P，V兩個(gè)程序，使信號(hào)量只加不減或只減不加

是什么樣的程序我不清楚。

不過(guò)你可以定義一個(gè) bool變量當(dāng)開(kāi)關(guān)嘛， 比如p操作時(shí)為 true，v操作時(shí)為false， 這樣就可以分開(kāi)兩個(gè)操作了

C語(yǔ)言 信號(hào)量的疑惑。。

一個(gè)是Posix實(shí)現(xiàn)，一個(gè)是System V實(shí)現(xiàn)

使用的環(huán)境不一樣

一般來(lái)講SV的適用于進(jìn)程同步，POSIX適用于線程同步

System V進(jìn)程同步 api：semget/semop/semctl

POSIX 線程同步 api:sem_init/sem_destroy

不過(guò)POSIX貌似還會(huì)分為有名和無(wú)名信號(hào)量上面說(shuō)的是無(wú)名信號(hào)量。

具體的還要看使用的環(huán)境。

c語(yǔ)言實(shí)例，linux線程同步的信號(hào)量方式 謝謝

這么高的懸賞，實(shí)例放后面。信號(hào)量(sem),如同進(jìn)程一樣，線程也可以通過(guò)信號(hào)量來(lái)實(shí)現(xiàn)通信，雖然是輕量級(jí)的。信號(hào)量函數(shù)的名字都以"sem_"打頭。線程使用的基本信號(hào)量函數(shù)有四個(gè)。

信號(hào)量初始化。

int?sem_init?(sem_t?*sem?,?int?pshared,?unsigned?int?value);

這是對(duì)由sem指定的信號(hào)量進(jìn)行初始化，設(shè)置好它的共享選項(xiàng)(linux?只支持為0，即表示它是當(dāng)前進(jìn)程的局部信號(hào)量)，然后給它一個(gè)初始值VALUE。

等待信號(hào)量。給信號(hào)量減1，然后等待直到信號(hào)量的值大于0。

int?sem_wait(sem_t?*sem);

釋放信號(hào)量。信號(hào)量值加1。并通知其他等待線程。

int?sem_post(sem_t?*sem);

銷(xiāo)毀信號(hào)量。我們用完信號(hào)量后都它進(jìn)行清理。歸還占有的一切資源。

int?sem_destroy(sem_t?*sem);

#include?stdlib.h??

#include?stdio.h??

#include?unistd.h??

#include?pthread.h??

#include?semaphore.h??

#include?errno.h??

#define?return_if_fail(p)?if((p)?==?0){printf?("[%s]:func?error!/n",?__func__);return;}??

typedef?struct?_PrivInfo??

{??

sem_t?s1;??

sem_t?s2;??

time_t?end_time;??

}PrivInfo;??

static?void?info_init?(PrivInfo*?thiz);??

static?void?info_destroy?(PrivInfo*?thiz);??

static?void*?pthread_func_1?(PrivInfo*?thiz);??

static?void*?pthread_func_2?(PrivInfo*?thiz);??

int?main?(int?argc,?char**?argv)??

{??

pthread_t?pt_1?=?0;??

pthread_t?pt_2?=?0;??

int?ret?=?0;??

PrivInfo*?thiz?=?NULL;??

thiz?=?(PrivInfo*?)malloc?(sizeof?(PrivInfo));??

if?(thiz?==?NULL)??

{??

printf?("[%s]:?Failed?to?malloc?priv./n");??

return?-1;??

}??

info_init?(thiz);??

ret?=?pthread_create?(pt_1,?NULL,?(void*)pthread_func_1,?thiz);??

if?(ret?!=?0)??

{??

perror?("pthread_1_create:");??

}??

ret?=?pthread_create?(pt_2,?NULL,?(void*)pthread_func_2,?thiz);??

if?(ret?!=?0)??

{??

perror?("pthread_2_create:");??

}??

pthread_join?(pt_1,?NULL);??

pthread_join?(pt_2,?NULL);??

info_destroy?(thiz);??

return?0;??

}??

static?void?info_init?(PrivInfo*?thiz)??

{??

return_if_fail?(thiz?!=?NULL);??

thiz-end_time?=?time(NULL)?+?10;??

sem_init?(thiz-s1,?0,?1);??

sem_init?(thiz-s2,?0,?0);??

return;??

}??

static?void?info_destroy?(PrivInfo*?thiz)??

{??

return_if_fail?(thiz?!=?NULL);??

sem_destroy?(thiz-s1);??

sem_destroy?(thiz-s2);??

free?(thiz);??

thiz?=?NULL;??

return;??

}??

static?void*?pthread_func_1?(PrivInfo*?thiz)??

{??

return_if_fail(thiz?!=?NULL);??

while?(time(NULL)??thiz-end_time)??

{??

sem_wait?(thiz-s2);??

printf?("pthread1:?pthread1?get?the?lock./n");??

sem_post?(thiz-s1);??

printf?("pthread1:?pthread1?unlock/n");??

sleep?(1);??

}??

return;??

}??

static?void*?pthread_func_2?(PrivInfo*?thiz)??

{??

return_if_fail?(thiz?!=?NULL);??

while?(time?(NULL)??thiz-end_time)??

{??

sem_wait?(thiz-s1);??

printf?("pthread2:?pthread2?get?the?unlock./n");??

sem_post?(thiz-s2);??

printf?("pthread2:?pthread2?unlock./n");??

sleep?(1);??

}??

return;??

}

用c語(yǔ)言或c++編寫(xiě)編程實(shí)現(xiàn)生產(chǎn)者消費(fèi)者或讀寫(xiě)者的同步問(wèn)題

實(shí)現(xiàn)一個(gè)隊(duì)列CQueue

CQueue提供兩個(gè)公有成員函數(shù)

addTail()：往隊(duì)列尾部增加一個(gè)元素

removeHead()：讀出并移除隊(duì)列的第一個(gè)元素

生產(chǎn)者：兩個(gè)線程通過(guò)調(diào)用CQueue::addTail()往隊(duì)列中增加元素

消費(fèi)者：一個(gè)線程通過(guò)調(diào)用CQueue::removeHead()從隊(duì)列中讀取元素

#include iostream

#include list

#include windows.h

#include process.h

using namespace std;

#define P(sem) WaitForSingleObject(sem,INFINITE)

#define V(sem) ReleaseSemaphore(sem,1,NULL)

class CQueue

{

public:

void addTail();//往隊(duì)列尾部增加一個(gè)元素

void removeHead();//讀出并移除隊(duì)列的第一個(gè)元素

private:

listint L;

};

CQueue buffer;//全局的緩沖區(qū)

const int buf_size = 10;//緩沖區(qū)大小

static int GOODS_ID = 0;//商品序號(hào)

const int producers = 3;//生產(chǎn)者數(shù)量

const int consumers = 8;//消費(fèi)者數(shù)量

void ProducerThread(void* param);

void ConsumerThread(void* param);

HANDLE empty,occupy,op_mutex;

int main()

{

int i;

int p_id[producers],c_id[consumers];

occupy = CreateSemaphore(NULL,0,buf_size,NULL);//占用位置

empty = CreateSemaphore(NULL,buf_size,buf_size,NULL);//空余位置

op_mutex = CreateSemaphore(NULL,1,1,NULL);//操作互斥量

for(i=0;iproducers;++i)

{

p_id[i] = i+1;

_beginthread(ProducerThread,0,p_id+i);

}

for(i=0;iconsumers;++i)

{

c_id[i] = i+1;

_beginthread(ConsumerThread,0,c_id+i);

}

while(getchar()=='\n') break;

return 0;

}

void CQueue::addTail()

{

L.insert(L.end(),++GOODS_ID);

}

void CQueue::removeHead()

{

cout*L.begin()endl;

L.erase(L.begin());

}

void ProducerThread(void* param)

{

int id = *(int*)param;

while(1)

{

P(empty);

P(op_mutex);

Sleep(100);

buffer.addTail();

printf("Producer_%d produced %d\n",id,GOODS_ID);

V(op_mutex);

V(occupy);

}

}

void ConsumerThread(void* param)

{

int id = *(int*)param;

while(1)

{

P(occupy);

P(op_mutex);

Sleep(100);

printf("Consumer_%d consumed ",id);

buffer.removeHead();

V(op_mutex);

V(empty);

}

}

請(qǐng)教一個(gè)Linux下C語(yǔ)言的進(jìn)程間的信號(hào)問(wèn)題

linux中的進(jìn)程通信分為三個(gè)部分：低級(jí)通信，管道通信和進(jìn)程間通信IPC（inter process communication）。linux的低級(jí)通信主要用來(lái)傳遞進(jìn)程的控制信號(hào)——文件鎖和軟中斷信號(hào)機(jī)制。linux的進(jìn)程間通信IPC有三個(gè)部分——①信號(hào)量，②共享內(nèi)存和③消息隊(duì)列。以下是我編寫(xiě)的linux進(jìn)程通信的C語(yǔ)言實(shí)現(xiàn)代碼。操作系統(tǒng)為redhat9.0，編輯器為vi，編譯器采用gcc。下面所有實(shí)現(xiàn)代碼均已經(jīng)通過(guò)測(cè)試，運(yùn)行無(wú)誤。

一.低級(jí)通信--信號(hào)通信

signal.c

#include

#include

#include

/*捕捉到信號(hào)sig之后，執(zhí)行預(yù)先預(yù)定的動(dòng)作函數(shù)*/

void sig_alarm(int sig)

{

printf("---the signal received is %d. /n", sig);

signal(SIGINT, SIG_DFL); //SIGINT終端中斷信號(hào)，SIG_DFL：恢復(fù)默認(rèn)行為，SIN_IGN：忽略信號(hào)

}

int main()

{

signal(SIGINT, sig_alarm);//捕捉終端中斷信號(hào)

while(1)

{

printf("waiting here!/n");

sleep(1);

}

return 0;

}

二.管道通信

pipe.c

#include

#define BUFFER_SIZE 30

int main()

{

int x;

int fd[2];

char buf[BUFFER_SIZE];

char s[BUFFER_SIZE];

pipe(fd);//創(chuàng)建管道

while((x=fork())==-1);//創(chuàng)建管道失敗時(shí)，進(jìn)入循環(huán)

/*進(jìn)入子進(jìn)程，子進(jìn)程向管道中寫(xiě)入一個(gè)字符串*/

if(x==0)

{

sprintf(buf,"This is an example of pipe!/n");

write(fd[1],buf,BUFFER_SIZE);

exit(0);

}

/*進(jìn)入父進(jìn)程，父進(jìn)程從管道的另一端讀出剛才寫(xiě)入的字符串*/

else

{

wait(0);//等待子進(jìn)程結(jié)束

read(fd[0],s,BUFFER_SIZE);//讀出字符串，并將其儲(chǔ)存在char s[]中

printf("%s",s);//打印字符串

}

return 0;

}

三.進(jìn)程間通信——IPC

①信號(hào)量通信

sem.c

#include

#include

#include

#include types.h

#include ipc.h

#include sem.h

/*聯(lián)合體變量*/

union semun

{

int val; //信號(hào)量初始值

struct semid_ds *buf;

unsigned short int *array;

struct seminfo *__buf;

};

/*函數(shù)聲明，信號(hào)量定義*/

static int set_semvalue(void); //設(shè)置信號(hào)量

static void del_semvalue(void);//刪除信號(hào)量

static int semaphore_p(void); //執(zhí)行P操作

static int semaphore_v(void); //執(zhí)行V操作

static int sem_id; //信號(hào)量標(biāo)識(shí)符

int main(int argc, char *argv[])

{

int i;

int pause_time;

char op_char = 'O';

srand((unsigned int)getpid());

sem_id = semget((key_t)1234, 1, 0666 | IPC_CREAT);//創(chuàng)建一個(gè)信號(hào)量,IPC_CREAT表示創(chuàng)建一個(gè)新的信號(hào)量

/*如果有參數(shù)，設(shè)置信號(hào)量，修改字符*/

if (argc 1)

{

if (!set_semvalue())

{

fprintf(stderr, "Failed to initialize semaphore/n");

exit(EXIT_FAILURE);

}

op_char = 'X';

sleep(5);

}

for(i = 0; i 10; i++)

{

/*執(zhí)行P操作*/

if (!semaphore_p())

exit(EXIT_FAILURE);

printf("%c", op_char);

fflush(stdout);

pause_time = rand() % 3;

sleep(pause_time);

printf("%c", op_char);

fflush(stdout);

/*執(zhí)行V操作*/

if (!semaphore_v())

exit(EXIT_FAILURE);

pause_time = rand() % 2;

sleep(pause_time);

}

printf("/n%d - finished/n", getpid());

if (argc 1)

{

sleep(10);

del_semvalue(); //刪除信號(hào)量

}

exit(EXIT_SUCCESS);

}

/*設(shè)置信號(hào)量*/

static int set_semvalue(void)

{

union semun sem_union;

sem_union.val = 1;

if (semctl(sem_id, 0, SETVAL, sem_union) == -1)

return(0);

return(1);

}

/*刪除信號(hào)量*/

static void del_semvalue(void)

{

union semun sem_union;

if (semctl(sem_id, 0, IPC_RMID, sem_union) == -1)

fprintf(stderr, "Failed to delete semaphore/n");

}

/*執(zhí)行P操作*/

static int semaphore_p(void)

{

struct sembuf sem_b;

sem_b.sem_num = 0;

sem_b.sem_op = -1; /* P() */

sem_b.sem_flg = SEM_UNDO;

if (semop(sem_id, sem_b, 1) == -1)

{

fprintf(stderr, "semaphore_p failed/n");

return(0);

}

return(1);

}

/*執(zhí)行V操作*/

static int semaphore_v(void)

{

struct sembuf sem_b;

sem_b.sem_num = 0;

sem_b.sem_op = 1; /* V() */

sem_b.sem_flg = SEM_UNDO;

if (semop(sem_id, sem_b, 1) == -1)

{

fprintf(stderr, "semaphore_v failed/n");

return(0);

}

return(1);

}

②消息隊(duì)列通信

send.c

#include

#include

#include

#include

#include

#include types.h

#include ipc.h

#include msg.h

#define MAX_TEXT 512

/*用于消息收發(fā)的結(jié)構(gòu)體--my_msg_type：消息類(lèi)型，some_text：消息正文*/

struct my_msg_st

{

long int my_msg_type;

char some_text[MAX_TEXT];

};

int main()

{

int running = 1;//程序運(yùn)行標(biāo)識(shí)符

struct my_msg_st some_data;

int msgid;//消息隊(duì)列標(biāo)識(shí)符

char buffer[BUFSIZ];

/*創(chuàng)建與接受者相同的消息隊(duì)列*/

msgid = msgget((key_t)1234, 0666 | IPC_CREAT);

if (msgid == -1)

{

fprintf(stderr, "msgget failed with error: %d/n", errno);

exit(EXIT_FAILURE);

}

/*向消息隊(duì)列中發(fā)送消息*/

while(running)

{

printf("Enter some text: ");

fgets(buffer, BUFSIZ, stdin);

some_data.my_msg_type = 1;

strcpy(some_data.some_text, buffer);

if (msgsnd(msgid, (void *)some_data, MAX_TEXT, 0) == -1)

{

fprintf(stderr, "msgsnd failed/n");

exit(EXIT_FAILURE);

}

if (strncmp(buffer, "end", 3) == 0)

{

running = 0;

}

}

exit(EXIT_SUCCESS);

}

receive.c

#include

#include

#include

#include

#include

#include types.h

#include ipc.h

#include msg.h

/*用于消息收發(fā)的結(jié)構(gòu)體--my_msg_type：消息類(lèi)型，some_text：消息正文*/

struct my_msg_st

{

long int my_msg_type;

char some_text[BUFSIZ];

};

int main()

{

int running = 1;//程序運(yùn)行標(biāo)識(shí)符

int msgid; //消息隊(duì)列標(biāo)識(shí)符

struct my_msg_st some_data;

long int msg_to_receive = 0;//接收消息的類(lèi)型--0表示msgid隊(duì)列上的第一個(gè)消息

/*創(chuàng)建消息隊(duì)列*/

msgid = msgget((key_t)1234, 0666 | IPC_CREAT);

if (msgid == -1)

{

fprintf(stderr, "msgget failed with error: %d/n", errno);

exit(EXIT_FAILURE);

}

/*接收消息*/

while(running)

{

if (msgrcv(msgid, (void *)some_data, BUFSIZ,msg_to_receive, 0) == -1)

{

fprintf(stderr, "msgrcv failed with error: %d/n", errno);

exit(EXIT_FAILURE);

}

printf("You wrote: %s", some_data.some_text);

if (strncmp(some_data.some_text, "end", 3) == 0)

{

running = 0;

}

}

/*刪除消息隊(duì)列*/

if (msgctl(msgid, IPC_RMID, 0) == -1)

{

fprintf(stderr, "msgctl(IPC_RMID) failed/n");

exit(EXIT_FAILURE);

}

exit(EXIT_SUCCESS);

}

③共享內(nèi)存通信

share.h

#define TEXT_SZ 2048 //申請(qǐng)共享內(nèi)存大小

struct shared_use_st

{

int written_by_you; //written_by_you為1時(shí)表示有數(shù)據(jù)寫(xiě)入，為0時(shí)表示數(shù)據(jù)已經(jīng)被消費(fèi)者提走

char some_text[TEXT_SZ];

};

producer.c

#include

#include

#include

#include

#include types.h

#include ipc.h

#include shm.h

#include "share.h"

int main()

{

int running = 1; //程序運(yùn)行標(biāo)志位

void *shared_memory = (void *)0;

struct shared_use_st *shared_stuff;

char buffer[BUFSIZ];

int shmid; //共享內(nèi)存標(biāo)識(shí)符

/*創(chuàng)建共享內(nèi)存*/

shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);

if (shmid == -1)

{

fprintf(stderr, "shmget failed/n");

exit(EXIT_FAILURE);

}

/*將共享內(nèi)存連接到一個(gè)進(jìn)程的地址空間中*/

shared_memory = shmat(shmid, (void *)0, 0);//指向共享內(nèi)存第一個(gè)字節(jié)的指針

if (shared_memory == (void *)-1)

{

fprintf(stderr, "shmat failed/n");

exit(EXIT_FAILURE);

}

printf("Memory attached at %X/n", (int)shared_memory);

shared_stuff = (struct shared_use_st *)shared_memory;

/*生產(chǎn)者寫(xiě)入數(shù)據(jù)*/

while(running)

{

while(shared_stuff-written_by_you == 1)

{

sleep(1);

printf("waiting for client.../n");

}

printf("Enter some text: ");

fgets(buffer, BUFSIZ, stdin);

strncpy(shared_stuff-some_text, buffer, TEXT_SZ);

shared_stuff-written_by_you = 1;

if (strncmp(buffer, "end", 3) == 0)

{

running = 0;

}

}

/*該函數(shù)用來(lái)將共享內(nèi)存從當(dāng)前進(jìn)程中分離,僅使得當(dāng)前進(jìn)程不再能使用該共享內(nèi)存*/

if (shmdt(shared_memory) == -1)

{

fprintf(stderr, "shmdt failed/n");

exit(EXIT_FAILURE);

}

printf("producer exit./n");

exit(EXIT_SUCCESS);

}

customer.c

#include

#include

#include

#include

#include types.h

#include ipc.h

#include shm.h

#include "share.h"

int main()

{

int running = 1;//程序運(yùn)行標(biāo)志位

void *shared_memory = (void *)0;

struct shared_use_st *shared_stuff;

int shmid; //共享內(nèi)存標(biāo)識(shí)符

srand((unsigned int)getpid());

/*創(chuàng)建共享內(nèi)存*/

shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);

if (shmid == -1)

{

fprintf(stderr, "shmget failed/n");

exit(EXIT_FAILURE);

}

/*將共享內(nèi)存連接到一個(gè)進(jìn)程的地址空間中*/

shared_memory = shmat(shmid, (void *)0, 0);//指向共享內(nèi)存第一個(gè)字節(jié)的指針

if (shared_memory == (void *)-1)

{

fprintf(stderr, "shmat failed/n");

exit(EXIT_FAILURE);

}

printf("Memory attached at %X/n", (int)shared_memory);

shared_stuff = (struct shared_use_st *)shared_memory;

shared_stuff-written_by_you = 0;

/*消費(fèi)者讀取數(shù)據(jù)*/

while(running)

{

if (shared_stuff-written_by_you)

{

printf("You wrote: %s", shared_stuff-some_text);

sleep( rand() % 4 );

shared_stuff-written_by_you = 0;

if (strncmp(shared_stuff-some_text, "end", 3) == 0)

{

running = 0;

}

}

}

/*該函數(shù)用來(lái)將共享內(nèi)存從當(dāng)前進(jìn)程中分離,僅使得當(dāng)前進(jìn)程不再能使用該共享內(nèi)存*/

if (shmdt(shared_memory) == -1)

{

fprintf(stderr, "shmdt failed/n");

exit(EXIT_FAILURE);

}

/*將共享內(nèi)存刪除,所有進(jìn)程均不能再訪問(wèn)該共享內(nèi)存*/

if (shmctl(shmid, IPC_RMID, 0) == -1)

{

fprintf(stderr, "shmctl(IPC_RMID) failed/n");

exit(EXIT_FAILURE);

}

exit(EXIT_SUCCESS);

}

摘自：

分享標(biāo)題：信號(hào)量函數(shù)用c語(yǔ)言怎么寫(xiě) C語(yǔ)言信號(hào)
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