2-32customer.c

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

#define MAX_FILE_SIZE 100*1024*1024 /*100MB*/

const char *fifo_file = "./myfifo";/*仿真FIFO文件名*/
const char *tmp_file = "./tmp";/*临时文件名*/

/*资源消费函数*/
int customing(const char *myfifo, int need){
	int fd;
	char buf;
	int counter = 0;

	if((fd = open(myfifo, O_RDONLY)) < 0){
		perror("Function customing error");
		return -1;
	}

	printf("Enioy:");
	lseek(fd, SEEK_SET, 0);
	while(counter < need){
		while((read(fd, &buf, 1) == 1) && (counter < need)){
			fputc(buf, stdout);/*消费就是在终端上简单显示*/
			counter++;
		}
	}
	fputs("\n", stdout);

	close(fd);
	return 0;
}
/*功能：从sour_file文件的offset偏移处开始将count字节数据复制到dest_file文件*/
int myfilecopy(const char *sour_file, const char *dest_file, int offset, int count, int copy_mode){
	int in_file, out_file;
	int counter = 0;
	char buff_unit;

	if((in_file = open(sour_file, O_RDONLY|O_NONBLOCK)) < 0){
		perror("Function myfilecopy error int source file\n");
		return -1;
	}

	if((out_file = open(dest_file, O_RDWR|O_CREAT|O_TRUNC|O_NONBLOCK, 0664)) < 0){
		perror("Function myfilecopy error in destination file");
		return -1;
	}

	lseek(in_file, offset, SEEK_SET);

	while((read(in_file, &buff_unit, 1) == 1) && (counter < count)){
		write(out_file, &buff_unit, 1);
		counter++;
	}

	close(in_file);
	close(out_file);
	return 0;
}
/*功能：实现FIFO消费者*/
int custom(int need){
	int fd;

	/*对资源进行消费，need表示该消费的资源数目*/

	customing(fifo_file, need);

	if((fd = open(fifo_file, O_RDWR)) < 0){
		perror("Function myfilecopy error in source_file");
		return -1;
	}

	/*为了模拟FIFO结构，对整个文件内容进行平行移动*/
	lock_set(fd, F_WRLCK);
	myfilecopy(fifo_file, tmp_file, need, MAX_FILE_SIZE, 0);
	myfilecopy(tmp_file, fifo_file, 0, MAX_FILE_SIZE, 0);
	lock_set(fd, F_UNLCK);

	unlink(tmp_file);
	close(fd);

	return 0;
}

int main(int argc, const char *argv[])
{
	int customer_capacity = 10;

	if(argc > 1){/*第一个参数指定需要消费的资源数目，默认值为10*/
		sscanf(argv[1], "%d", &customer_capacity);
	}

	if(customer_capacity > 0){
		custom(customer_capacity);
	}
	return 0;
}