操作系统 电梯调c语言

电梯调度是一个典型的操作系统问题，具体实现可以借助C语言来完成。以下是一个简单的电梯调度C语言代码示例：

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>

#define FLOOR_NUM 20
#define ELEVATOR_NUM 3
#define MAX_PEOPLE 10

enum Direction {
    UP,
    DOWN
};

struct Person {
    int id;
    int start_floor;
    int end_floor;
};

struct Elevator {
    int id;
    int cur_floor;
    int num_people;
    struct Person people[MAX_PEOPLE];
    enum Direction direction;
    pthread_mutex_t mutex;
    pthread_cond_t cond;
    pthread_t thread;
};

struct Building {
    struct Elevator elevators[ELEVATOR_NUM];
    pthread_mutex_t mutex;
};

void person_init(struct Person *person, int id, int start_floor, int end_floor) {
    person->id = id;
    person->start_floor = start_floor;
    person->end_floor = end_floor;
}

void elevator_init(struct Elevator *elevator, int id) {
    elevator->id = id;
    elevator->cur_floor = 1;
    elevator->num_people = 0;
    elevator->direction = UP;
    pthread_mutex_init(&elevator->mutex, NULL);
    pthread_cond_init(&elevator->cond, NULL);
}

void building_init(struct Building *building) {
    for (int i = 0; i < ELEVATOR_NUM; i++) {
        elevator_init(&building->elevators[i], i);
    }
    pthread_mutex_init(&building->mutex, NULL);
}

void elevator_add_person(struct Elevator *elevator, struct Person *person) {
    pthread_mutex_lock(&elevator->mutex);
    while (elevator->num_people >= MAX_PEOPLE) { // 电梯已满
        pthread_cond_wait(&elevator->cond, &elevator->mutex); // 等待
    }
    elevator->people[elevator->num_people++] = *person;
    pthread_cond_signal(&elevator->cond); // 通知电梯已有人
    pthread_mutex_unlock(&elevator->mutex);
}

void elevator_remove_person(struct Elevator *elevator, int index) {
    pthread_mutex_lock(&elevator->mutex);
    for (int i = index; i < elevator->num_people - 1; i++) {
        elevator->people[i] = elevator->people[i + 1];
    }
    elevator->num_people--;
    pthread_cond_signal(&elevator->cond); // 通知电梯已有空位
    pthread_mutex_unlock(&elevator->mutex);
}

void elevator_move(struct Elevator *elevator) {
    pthread_mutex_lock(&elevator->mutex);
    if (elevator->direction == UP) {
        for (int i = 0; i < FLOOR_NUM; i++) {
            if (i < elevator->cur_floor) { // 已经经过的楼层
                continue;
            }
            elevator->cur_floor = i;
            printf("电梯%d上行到%d楼\n", elevator->id, elevator->cur_floor);
            for (int j = 0; j < elevator->num_people; j++) { // 检查每个人是否到达目的地
                if (elevator->people[j].end_floor == elevator->cur_floor) {
                    printf("电梯%d有人在%d楼下电梯\n", elevator->id, elevator->cur_floor);
                    elevator_remove_person(elevator, j);
                    j--;
                }
            }
            if (elevator->cur_floor == FLOOR_NUM - 1) { // 到达顶层，改为下行
                elevator->direction = DOWN;
                break;
            }
        }
    } else {
        for (int i = FLOOR_NUM - 1; i >= 0; i--) {
            if (i > elevator->cur_floor) { // 已经经过的楼层
                continue;
            }
            elevator->cur_floor = i;
            printf("电梯%d下行到%d楼\n", elevator->id, elevator->cur_floor);
            for (int j = 0; j < elevator->num_people; j++) { // 检查每个人是否到达目的地
                if (elevator->people[j].end_floor == elevator->cur_floor) {
                    printf("电梯%d有人在%d楼下电梯\n", elevator->id, elevator->cur_floor);
                    elevator_remove_person(elevator, j);
                    j--;
                }
            }
            if (elevator->cur_floor == 0) { // 到达底层，改为上行
                elevator->direction = UP;
                break;
            }
        }
    }
    pthread_mutex_unlock(&elevator->mutex);
}

void *elevator_thread(void *arg) {
    struct Elevator *elevator = (struct Elevator *)arg;
    while (1) {
        elevator_move(elevator);
        usleep(1); // 等待一段时间，模拟电梯运行
    }
    return NULL;
}

void building_add_person(struct Building *building, struct Person *person) {
    int elevator_id = rand() % ELEVATOR_NUM;
    pthread_mutex_lock(&building->elevators[elevator_id].mutex);
    elevator_add_person(&building->elevators[elevator_id], person);
    pthread_mutex_unlock(&building->elevators[elevator_id].mutex);
}

void *person_thread(void *arg) {
    struct Person *person = (struct Person *)arg;
    printf("有人[%d]在%d楼等电梯\n", person->id, person->start_floor);
    building_add_person((struct Building *)arg, person);
    return NULL;
}

int main() {
    srand(time(NULL)); // 随机数种子
    struct Building building;
    building_init(&building);

    pthread_t person_threads[MAX_PEOPLE];
    for (int i = 0; i < MAX_PEOPLE; i++) {
        struct Person person;
        person_init(&person, i, rand() % FLOOR_NUM, rand() % FLOOR_NUM);
        pthread_create(&person_threads[i], NULL, person_thread, (void *)&building);
        usleep(10000); // 等待一段时间，模拟人的到来
    }

    for (int i = 0; i < ELEVATOR_NUM; i++) {
        pthread_create(&building.elevators[i].thread, NULL, elevator_thread, (void *)&building.elevators[i]);
    }

    for (int i = 0; i < MAX_PEOPLE; i++) {
        pthread_join(person_threads[i], NULL);
    }

    for (int i = 0; i < ELEVATOR_NUM; i++) {
        pthread_cancel(building.elevators[i].thread);
    }

    return 0;
}

以上代码实现了一个多线程的电梯调度，包括电梯的初始化、人员的加入和移除、电梯的移动等功能。在主函数中，我们使用多个线程模拟了多个人同时在楼层等电梯，通过调用`building_add_person`函数将人分配给随机选择的电梯。电梯运行的过程在`elevator_thread`函数中被模拟，通过调用`elevator_move`函数实现电梯的移动，每次移动后等待一段时间，模拟电梯的实际运行。最后，我们使用`pthread_cancel`函数取消电梯线程的运行。

需要注意的是，多线程程序中需要使用锁和条件变量来保证线程之间的同步和互斥，避免出现竞态条件等问题。在以上代码中，我们使用了`pthread_mutex_t`和`pthread_cond_t`等线程相关的函数来实现同步和互斥。