#include <iostream>
#include <sys/types.h>
#include <sys/ipc.h>
#include <cstring>
#include <unistd.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/ipc.h>
#include <sys/stat.h>
#include <fcntl.h>

#define PATHNAME "/home/sxb/240416/shared_memory"
#define PROJ_ID 0x28364
#define DEFAULT_SIZE 4096

using namespace std;

key_t get_key(const char *pathname, int proj_id)
{
    key_t key = ftok(pathname, proj_id);

    // 成功返回key值，失败返回-1
    if (key == -1)
    {
        cout << "获取key值失败，原因是：" << strerror(errno) << endl;
        exit(1);
    }

    return key;
}

int get_or_create_shared_memory(key_t key, int size, int flag)
{
    int shmid = shmget(key, size, flag);

    // 成功返回共享内存标识符，失败返回-1
    if (shmid == -1)
    {
        cout << "共享内存创建失败，原因是：" << strerror(errno) << endl;
        exit(2);
    }

    return shmid;
}

int create_shared_memory(key_t key, int size)
{
    return get_or_create_shared_memory(key, size, IPC_CREAT | IPC_EXCL | 0666);
}

int get_shared_memory(key_t key, int size)
{
    return get_or_create_shared_memory(key, size, IPC_CREAT);
}

void *shm_attch(int shmid)
{
    void *addr = shmat(shmid, nullptr, 0);

    if ((long long int)addr == -1)
    {
        cerr << "挂接失败" << endl;
        return nullptr;
    }
    else
        cout << "挂接成功" << endl;
    return addr;
}

void shm_detach(void *addr)
{
    int ret = shmdt(addr);
    if (ret == -1)
    {
        cerr << "去挂接失败" << endl;
    }
    else
        cout << "去挂接成功" << endl;
}

void shm_del(int shmid)
{
    int ret = shmctl(shmid, IPC_RMID, nullptr);
    if (ret == -1)
        cerr << "删除共享内存失败" << endl;
    else
        cout << "删除共享内存成功" << endl;
}