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操作系统第三次作业-文件管理系统

1. 介绍

本次作业是在内存中模拟实现一个文件管理系统，退出此文件系统后，会将该文件系统的内容保存到磁盘中，下次使用此文件系统时可以将上次的内容恢复到内存中去。

本项目实现了一个基本完整的文件系统，实现的功能点有：

  • 格式化
  • 新建子目录
  • 删除子目录
  • 显示当前目录
  • 新建文件
  • 删除文件
  • 更改当前目录
  • 打开文件
  • 关闭文件
  • 写文件
  • 读文件
  • 文件与目录重命名
  • 统计文件大小

同时提供了一个简洁的用户交互界面，以及一个简单的文本编辑器可以对文件进行查看与编辑操作。

开发环境

  • 语言：python3
  • 界面：PyQt5
  • 操作系统：Kubuntu 23.04

3. 系统设计

3.1 文件系统内核

3.1.1 块类设计

本文件系统对空间进行分块管理，一块的大小为4kB,块类设计如下：

class Block:
    def __init__(self):
        self.block_size = 1024*4
        self.data = bytearray(self.block_size)

    def write(self, data: bytearray):
        self.data = data

    def read(self) -> bytearray:
        return self.data

3.1.2 Inode类设计

Inode类保存每个文件相关信息，例如单个文件块索引位置，文件创建修改与访问时间，文件大小等信息。设计如下：

class Inode:
    def __init__(self):
        self.file_size = 0
        self.file_blocks_index = []
        self.ctime = datetime.now()
        self.mtime = datetime.now()
        self.atime = datetime.now()

    def add_block(self, block_index: int):
        self.file_blocks_index.append(block_index)

    def remove_block(self, block_index: int):
        self.file_blocks_index.remove(block_index)

3.1.3 文件类设计

文件类包含一个对应的Inode对象和文件名以及类型标识符，具有read,write，与clear方法，read,write方法读写对应文件内容，clear方法情空文件内容，同时标记位图释放空闲块。

class File:
    def __init__(self, name):
        self.name = name
        self.inode = Inode()
        self.type = "file"

    def read(self, fs: FileSystem) -> bytearray:
        data = bytearray()
        self.inode.atime = datetime.now()
        for block_index in self.inode.file_blocks_index:
            data += fs.space[block_index].read()
        return data

    def write(self, data: bytearray, fs: FileSystem) -> bool:
        valid_block_nums = fs.get_valid_block_nums()
        block_count = len(data) // (1024*4) + 1
        if block_count > valid_block_nums:
            print("No more space available")
            return False
        self.clear(fs)
        self.inode.file_size = len(data)
        fs.used_size += self.inode.file_size
        for i in range(block_count):
            j = 0
            for j in range(fs.file_block_nums):
                if fs.valid_blocks[j] == 0:
                    fs.valid_blocks[j] = 1
                    block = fs.space[j]
                    if i == 0:
                        self.inode.mtime = datetime.now()
                        self.inode.atime = datetime.now()
                    block.write(
                        data[i * 1024*4: min((i + 1) * 1024*4, len(data))])
                    self.inode.add_block(j)
                    break
            if j == fs.file_block_nums-1:
                print("No more space available")
                return False
        return True

    def clear(self, fs: FileSystem):
        """释放文件占用block
        """
        fs.used_size -= self.inode.file_size
        self.inode.ctime = datetime.now()
        self.inode.mtime = datetime.now()
        self.inode.atime = datetime.now()
        for i in self.inode.file_blocks_index:
            fs.valid_blocks[i] = 0
        self.inode.file_blocks_index = []

3.1.4 目录类设计

目录类包含目录名，子目录列表，子文件列表，父目录等相关信息，提供添加删除文件，添加删除子目录，列出目录内容等方法。

class Directory:
    def __init__(self, name, parent):
        self.name = name
        self.parent = parent
        self.files = []
        self.subdirectories = []
        self.type = "directory"

    def add_file(self, file):
        self.files.append(file)

    def remove_file(self, file, fs: FileSystem):
        file.clear(fs)
        self.files.remove(file)

    def get_file(self, name):
        for file in self.files:
            if file.name == name:
                return file

    def add_subdirectory(self, directory):
        self.subdirectories.append(directory)

    def remove_subdirectory(self, directory, fs: FileSystem):
        if directory in self.subdirectories:
            for file in directory.files:
                directory.remove_file(file, fs)
            self.subdirectories.remove(directory)
            directory.parent = None
            directory.remove_all_subdirectories(fs)

    def remove_all_subdirectories(self, fs: FileSystem):
        for directory in self.subdirectories:
            for file in directory.files:
                directory.remove_file(file, fs)
            directory.parent = None
            directory.remove_all_subdirectories(fs)
        self.subdirectories = []

    def get_subdirectory(self, name):
        for directory in self.subdirectories:
            if directory.name == name:
                return directory

    def list_contents(self):
        dir_contents = []
        file_contents = []
        for directory in self.subdirectories:
            dir_contents.append(directory)
        for file in self.files:
            file_contents.append(file)
        return dir_contents, file_contents

3.1.5 文件系统类设计

文件系统类对外层提供所有文件系统的相关接口，同时存储当前所处目录位置，文件系统整体空间，以及位图管理文件系统空闲空间。

class FileSystem:
    def __init__(self):
        self.root = Directory("/", None)
        self.current_directory = self.root
        self.file_block_nums = 2560*4  # 块数量
        self.valid_blocks = bytearray(
            self.file_block_nums)    # 位图管理空闲空间，0表示空闲, 1表示已使用
        self.space = [Block() for _ in range(self.file_block_nums)]  # 文件系统整体空间
        self.used_size = 0

    def create_file(self, name):
        for file in self.current_directory.files:
            if file.name == name:
                print("File already exists")
                return False
        file = File(name)
        self.current_directory.add_file(file)
        return True

    def delete_file(self, name):
        file = self.current_directory.get_file(name)
        if file:
            self.current_directory.remove_file(file, self)
            return True
        else:
            print("File not found")
            return False

    def read_file(self, name):
        file = self.current_directory.get_file(name)
        if file:
            return file.read(self)
        else:
            return bytearray()

    def write_file(self, name, data):
        file = self.current_directory.get_file(name)
        if file:
            return file.write(data, self)
        else:
            return False

    def list_directory(self):
        return self.current_directory.list_contents()

    def change_directory(self, name):
        if name == "..":
            parent = self.current_directory.parent
            if parent:
                self.current_directory = parent
            return
        for dir in self.current_directory.subdirectories:
            if dir.name == name:
                self.current_directory = dir
                return
        directory = self.find_directory(self.root, name)
        if directory:
            self.current_directory = directory

    def find_directory(self, directory, name):
        if directory.name == name:
            return directory

        for subdirectory in directory.subdirectories:
            result = self.find_directory(subdirectory, name)
            if result:
                return result

        return None

    def make_directory(self, name):
        for dir in self.current_directory.subdirectories:
            if dir.name == name:
                print("Directory already exists")
                return False
        directory = Directory(name, self.current_directory)
        self.current_directory.add_subdirectory(directory)
        return True

    def remove_directory(self, name):
        for subdirectory in self.current_directory.subdirectories:
            if name == subdirectory.name:
                self.current_directory.remove_subdirectory(subdirectory, self)
                return True
        directory = self.find_directory(self.root, name)
        parent = directory.parent
        if directory:
            parent.remove_subdirectory(directory, self)
            return True
        else:
            print("Directory not found")
            return False

    def save_to_disk(self, filename):
        with open(filename, "wb") as f:
            pickle.dump(self, f)

    def get_current_path(self):
        # 获取当前目录的路径
        if self.current_directory.name == "/":
            return "/"
        path = ""
        directory = self.current_directory
        while directory.name != "/":
            path = "/"+directory.name + path
            directory = directory.parent
        return path

    def get_file_size(self, file):
        return file.inode.file_size

    def get_file_mtime(self, file):
        return file.inode.mtime

    def get_dir_item_nums(self, directory):
        return len(directory.files) + len(directory.subdirectories)

    def rename_file(self, old_name, new_name):
        """重命名文件
        Returns:
            bool: 是否成功
            int: 错误码, 0表示成功, 1表示文件不存在, 2表示新文件名与旧文件名相同, 3表示新文件名已存在, 4表示新文件名为空
        """
        if new_name is None:
            return False, 4
        if new_name == old_name:
            return False, 2
        for file in self.current_directory.files:
            if file.name == new_name:
                return False, 3
        file = self.current_directory.get_file(old_name)
        if file:
            file.name = new_name
            return True, 0
        else:
            return False, 1

    def rename_directory(self, old_name, new_name):
        """重命名目录
        Returns:
            bool: 是否成功
            int: 错误码, 0表示成功, 1表示目录不存在, 2表示新目录名与旧目录名相同, 3表示新目录名已存在, 4表示新目录名为空
        """
        if new_name is None:
            return False, 4
        if new_name == old_name:
            return False, 2
        if new_name in [dir.name for dir in self.current_directory.subdirectories]:
            return False, 3
        directory = self.current_directory.get_subdirectory(old_name)
        if directory:
            directory.name = new_name
            return True, 0
        else:
            return False, 1

    def fformat(self):
        for file in self.root.files:
            self.root.remove_file(file, self)
        self.root.remove_all_subdirectories(self)

    def get_total_and_used_space_size(self):
        return self.file_block_nums*1024*4, self.used_size

    def get_valid_block_nums(self) -> int:
        result = 0
        for block in self.valid_blocks:
            if block == 0:
                result += 1
        return result

3.1.6 文件存储空间管理

文件存储空间管理采取索引表的方式，通过对文件系统空间分块读取，对块索引，来进行文件的读写，相关操作函数如下：

  • write

    def write(self, data: bytearray, fs: FileSystem) -> bool:
    valid_block_nums = fs.get_valid_block_nums()
    block_count = len(data) // (1024*4) + 1
    if block_count > valid_block_nums:
        print("No more space available")
        return False
    self.clear(fs)
    self.inode.file_size = len(data)
    fs.used_size += self.inode.file_size
    for i in range(block_count):
        j = 0
        for j in range(fs.file_block_nums):
            if fs.valid_blocks[j] == 0:
                fs.valid_blocks[j] = 1
                block = fs.space[j]
                if i == 0:
                    self.inode.mtime = datetime.now()
                    self.inode.atime = datetime.now()
                    block.write(
                        data[i * 1024*4: min((i + 1) * 1024*4, len(data))])
                    self.inode.add_block(j)
                    break
                    if j == fs.file_block_nums-1:
                        print("No more space available")
                        return False
                    return True

  • read

    def read(self, fs: FileSystem) -> bytearray:
    data = bytearray()
    self.inode.atime = datetime.now()
    for block_index in self.inode.file_blocks_index:
        data += fs.space[block_index].read()
        return data

3.1.7 空闲空间管理

空闲空间管理采用位图标记，0表示块空闲，1表示块占用，代码如下：

self.valid_blocks = bytearray(
            self.file_block_nums)    # 位图管理空闲空间，0表示空闲, 1表示已使用

当对文件进行写入时，会首先计算该文件需要占用的块数，然后遍历块位图，找到空闲块进行写入，

for i in range(block_count):
    j = 0
    for j in range(fs.file_block_nums):
        if fs.valid_blocks[j] == 0:
            fs.valid_blocks[j] = 1
            block = fs.space[j]
            if i == 0:
                self.inode.mtime = datetime.now()
                self.inode.atime = datetime.now()
                block.write(
                    data[i * 1024*4: min((i + 1) * 1024*4, len(data))])
                self.inode.add_block(j)
                break
                if j == fs.file_block_nums-1:
                    print("No more space available")
                    return False

文件删除时，也会首先释放块的占用，更改位图：

def clear(self, fs: FileSystem):
    """释放文件占用block
        """
    fs.used_size -= self.inode.file_size
    self.inode.ctime = datetime.now()
    self.inode.mtime = datetime.now()
    self.inode.atime = datetime.now()
    for i in self.inode.file_blocks_index:
        fs.valid_blocks[i] = 0
        self.inode.file_blocks_index = []

3.1.8 文件目录管理

文件目录采用多级目录结构，可以在不同级目录间进行切换，目录项中记录了文件名，文件大小以及文件索引地址等信息。

class Inode:
    def __init__(self):
        self.file_size = 0
        self.file_blocks_index = []
        self.ctime = datetime.now()
        self.mtime = datetime.now()
        self.atime = datetime.now()

    def add_block(self, block_index: int):
        self.file_blocks_index.append(block_index)

    def remove_block(self, block_index: int):
        self.file_blocks_index.remove(block_index)
class Directory:
    def __init__(self, name, parent):
        self.name = name
        self.parent = parent
        self.files = []
        self.subdirectories = []
        self.type = "directory"

3.1.9 磁盘保存

由于本文件系统是在内存中开辟一块空间，当退出文件系统后，会调用python的pickle模块将文件系统对象序列化为fs.pickle文件保存到磁盘，当下次打开本文件系统时，将会从本地的fs.pickle文件读取文件系统对象，实现保留上一次使用的内容。

def save_to_disk(self, filename):
    with open(filename, "wb") as f:
        pickle.dump(self, f)
def load_from_disk(filename):
    with open(filename, "rb") as f:
        return pickle.load(f)

3.2 界面设计

3.2.1 界面展示

  • 主界面

    1. 正常界面

      image-20230605110117806

    2. 右键菜单

      image-20230605110918495

  • 编辑器界面

    1. 正常界面

      image-20230605110530823

    2. 做出修改未保存，标题栏显示“*”号

      image-20230605110634294

3.3.2 功能提供

本UI界面提供以下几点功能：

  • 新建文件
  • 新建文件夹
  • 重命名文件或文件夹
  • 删除文件或文件夹
  • 格式化文件系统
  • 文件编辑(支持快捷键Ctrl+s保存)

以上功能可以通过按钮点击也可通过右键菜单实现。

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同济大学软件学院2021级操作系统第三次作业-文件系统

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