代码

#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <cassert>
#include <pthread.h>
#include <cstdio>
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <sstream>
#include <cstring>
#include <sys/wait.h>/***  返回一片共享内存标识符，用于后续获取该共享内存，以及销毁该共享内存*/class mutex_function{public:mutex_function() = default;// 定义进程锁结构体typedef struct mutex_struct{pthread_rwlock_t lock;pthread_rwlockattr_t lock_attr;int memory_addr;}mutex_struct_t;int create_share_memory_id(const int index_of_key,size_t md5){const char* file_path = "./";key_t id = ftok(file_path,md5);const int share_memory_id = shmget(id,md5,IPC_CREAT | 0666);if (share_memory_id == -1){std::cout << "share_memory_id error!\n" << std::endl;exit(EXIT_FAILURE);}else{return share_memory_id;}}// 初始化进程锁结构体int init_mutex_struct(mutex_struct_t* mutex_ptr){pthread_rwlockattr_init(&(mutex_ptr->lock_attr));pthread_rwlockattr_setpshared(&(mutex_ptr->lock_attr),PTHREAD_PROCESS_SHARED);pthread_rwlock_init(&(mutex_ptr->lock),&(mutex_ptr->lock_attr));return 0;}// 在共享内存上定义进程锁结构体并且返回其位置mutex_struct_t* mutex_struct_addr(const int index){int memory_id = create_share_memory_id(index,sizeof (mutex_struct_t));mutex_struct_t * share_ptr = (mutex_struct_t* )shmat(memory_id, 0, 0);if (share_ptr == (void *)-1){std::cout << "share_ptr error!\n" << std::endl;exit(EXIT_FAILURE);}share_ptr->memory_addr = memory_id;assert(init_mutex_struct(share_ptr)== 0);return share_ptr;}// 销毁进程锁结构体，利用其memory_addr变量索引到其占用的共享内存并销毁const int destroy_mutex_memory(mutex_struct_t * mutex_struct){pthread_rwlock_destroy(&(mutex_struct->lock));pthread_rwlockattr_destroy(&(mutex_struct->lock_attr));assert(shmctl(mutex_struct->memory_addr,IPC_RMID, nullptr) == 0);return 0;}public:mutex_struct_t* mutex_struct_ptr;};//read file
void read_file(const std::string file_name,int id){std::ifstream fp(file_name,std::ios::binary);std::stringstream ss;ss << fp.rdbuf();std::cout << "线程"<< id << "抢占了资源,输出:" << ss.str() << std::endl;sleep(3);std::cout << "线程"<< id << "释放了资源...\n" << std::endl;fp.close();
}
//write file
void write_file(const char *file_name,char *str,int id){FILE *fd = fopen(file_name,"a+");if (fd == nullptr){printf("fd is nullptr and open file fail\n");} else{std::cout <<"线程"<< id << "抢占了资源" << std::endl;fwrite(str,strlen(str),1,fd);char *next = "\0";fwrite(next,strlen(next),1,fd);sleep(5);std::cout << "线程"<< id << "释放了资源...\n" << std::endl;}fclose(fd);
}
int main(){std::string file_name = "/home/gsc/Projects/1.txt";char * str1 = "progress 1\n";char * str2 = "progress 2\n";// 创建自定义进程锁hsm::hal::mutex_function mutex_function_object;mutex_function_object.mutex_struct_ptr = mutex_function_object.mutex_struct_addr(111);pid_t c_pid = fork();if (c_pid == -1) {perror("fork");exit(EXIT_FAILURE);} else if (c_pid > 0) {std::cout << "Parent process " << getpid() << std::endl;
//            pthread_rwlock_rdlock(&(mutex_function_object.mutex_struct_ptr->lock));
//            read_file(file_name,getpid());
//            pthread_rwlock_unlock(&(mutex_function_object.mutex_struct_ptr->lock));pthread_rwlock_wrlock(&(mutex_function_object.mutex_struct_ptr->lock));write_file(file_name.c_str(),str1,getpid());pthread_rwlock_unlock(&(mutex_function_object.mutex_struct_ptr->lock));wait(nullptr);} else {std::cout << "Child process " << getpid() << std::endl;pthread_rwlock_rdlock(&(mutex_function_object.mutex_struct_ptr->lock));read_file(file_name,getpid());pthread_rwlock_unlock(&(mutex_function_object.mutex_struct_ptr->lock));//        pthread_rwlock_wrlock(&(mutex_function_object.mutex_struct_ptr->lock));
//        write_file(file_name.c_str(),str2,getpid());
//        pthread_rwlock_unlock(&(mutex_function_object.mutex_struct_ptr->lock));exit(EXIT_SUCCESS);}return 0;
}