实现 I/O设备管理spooling技术例程库的c代码

以下是一个简单的 I/O 设备管理 spooling 技术例程库的 C 代码：

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

#define MAX_QUEUE_SIZE 10
#define MAX_LINE_LENGTH 1024

typedef struct {
    char *line;
    int length;
} Line;

typedef struct {
    Line queue[MAX_QUEUE_SIZE];
    int front;
    int rear;
    int size;
    pthread_mutex_t mutex;
    pthread_cond_t cond_full;
    pthread_cond_t cond_empty;
} Spooler;

void init_spooler(Spooler *spooler) {
    spooler->front = 0;
    spooler->rear = 0;
    spooler->size = 0;
    pthread_mutex_init(&spooler->mutex, NULL);
    pthread_cond_init(&spooler->cond_full, NULL);
    pthread_cond_init(&spooler->cond_empty, NULL);
}

void destroy_spooler(Spooler *spooler) {
    pthread_mutex_destroy(&spooler->mutex);
    pthread_cond_destroy(&spooler->cond_full);
    pthread_cond_destroy(&spooler->cond_empty);
}

void enqueue(Spooler *spooler, const char *line) {
    pthread_mutex_lock(&spooler->mutex);
    while (spooler->size == MAX_QUEUE_SIZE) {
        pthread_cond_wait(&spooler->cond_full, &spooler->mutex);
    }
    spooler->queue[spooler->rear].length = strlen(line);
    spooler->queue[spooler->rear].line = malloc(spooler->queue[spooler->rear].length + 1);
    strcpy(spooler->queue[spooler->rear].line, line);
    spooler->rear = (spooler->rear + 1) % MAX_QUEUE_SIZE;
    spooler->size++;
    pthread_cond_signal(&spooler->cond_empty);
    pthread_mutex_unlock(&spooler->mutex);
}

Line dequeue(Spooler *spooler) {
    pthread_mutex_lock(&spooler->mutex);
    while (spooler->size == 0) {
        pthread_cond_wait(&spooler->cond_empty, &spooler->mutex);
    }
    Line line = spooler->queue[spooler->front];
    spooler->front = (spooler->front + 1) % MAX_QUEUE_SIZE;
    spooler->size--;
    pthread_cond_signal(&spooler->cond_full);
    pthread_mutex_unlock(&spooler->mutex);
    return line;
}

void *spooler_thread(void *arg) {
    Spooler *spooler = (Spooler *) arg;
    while (1) {
        Line line = dequeue(spooler);
        printf("Printing: %s\n", line.line);
        free(line.line);
    }
}

void print(const char *line, Spooler *spooler) {
    enqueue(spooler, line);
}

int main() {
    Spooler spooler;
    init_spooler(&spooler);
    pthread_t thread;
    pthread_create(&thread, NULL, spooler_thread, &spooler);
    char line[MAX_LINE_LENGTH];
    while (fgets(line, MAX_LINE_LENGTH, stdin)) {
        print(line, &spooler);
    }
    destroy_spooler(&spooler);
    pthread_join(thread, NULL);
    return 0;
}

这段代码定义了一个 Spooler 结构体，其中包含一个循环队列，一个互斥锁和两个条件变量。enqueue 函数将一行字符插入到队列中，dequeue 函数从队列中取出一行字符。spooler_thread 函数是一个长期运行的线程，它不断从队列中取出字符并打印。

在 main 函数中，我们首先初始化一个 Spooler 实例，然后创建一个线程来处理队列中的字符。接下来，我们从标准输入读取字符，并将其插入到队列中。最后，我们销毁 Spooler 实例并等待线程结束。