clock页面置换算法py

以下是Clock页面置换算法的Python实现：

class Page:
    def __init__(self, id):
        self.id = id
        self.referenced = False
        self.modified = False

class Clock:
    def __init__(self, frame_num):
        self.frame_num = frame_num
        self.frames = []
        self.pointer = 0

        for i in range(frame_num):
            self.frames.append(Page(-1))

    def refer(self, page_id):
        for i in range(self.frame_num):
            if self.frames[i].id == page_id:
                self.frames[i].referenced = True
                return

        for i in range(self.frame_num):
            if not self.frames[i].referenced:
                self.frames[i].id = page_id
                self.frames[i].referenced = True
                self.pointer = (i + 1) % self.frame_num
                return

        while True:
            if self.frames[self.pointer].referenced:
                self.frames[self.pointer].referenced = False
                self.pointer = (self.pointer + 1) % self.frame_num
            else:
                self.frames[self.pointer].id = page_id
                self.frames[self.pointer].referenced = True
                self.pointer = (self.pointer + 1) % self.frame_num
                return

    def print_frames(self):
        for i in range(self.frame_num):
            print(self.frames[i].id, end=' ')
        print()

使用方法：

clock = Clock(4)   # 初始化Clock对象，设置帧数为4
clock.refer(1)     # 引用页面1
clock.refer(2)     # 引用页面2
clock.refer(3)     # 引用页面3
clock.refer(4)     # 引用页面4
clock.refer(1)     # 引用页面1
clock.refer(2)     # 引用页面2
clock.refer(5)     # 引用页面5，此时发生页面置换
clock.print_frames()  # 打印当前帧

输出结果：

5 2 3 4