FAT 文件系统模拟设计与实现：C语言程序模拟FAT16

实验描述

利用标准C 语言，模拟实现 FAT 16文件系统，支持 FAT 文件系统格式的模拟磁盘卷及其中的目录与文件的存取操作，包括磁盘卷格式化、创建目录、改变当前目录、重命名目录、显示目录、删除目录、创建空文件、重命名文件、写文件、显示文件内容、删除文件。

用到的数据结构

1. 路径存储，存储卷的名字和当前的目录，存储目录的起点和空闲块。当卷没有初始化即卷名字为空时可以实现报错 

   typedef struct {
       char filename[MAX_FILENAME_LENGTH];
       int start_block;
       int size;
       char data[MAX_FILE_SIZE];
   } DirectoryEntry;

2. 文件的数据结构，存储文件的起点和占用的块的大小，data存储文件内部的数据

   typedef struct {
       char volume_name[MAX_FILENAME_LENGTH];
       int total_blocks;
       int free_blocks;
       DirectoryEntry* directory;
       char current_path[MAX_FILENAME_LENGTH];
   } FileSystem;

磁盘使用模拟

分别用函数实现磁盘卷格式化、创建目录、改变当前目录、重命名目录、显示目录、删除目录、创建空文件、重命名文件、写文件、显示文件内容、删除文件。列表编号每个操作，输入对应的序号选择操作并且进行交互，遇到一些错误则会有提示，模拟结束可以选择退出的操作。

运行示例

卷的初始化：输入卷名字和空间大小，即磁盘的格式化

创建目录user1

进入目录user1，此处若没有写对目录名字则会报错

创建新文件story

查看目录

写文件story，需要在此处输入有效的文件名

查看文件story，需要在此处输入有效的文件名

完整程序 

#include 
#include 
#include 
#define MAX_FILENAME_LENGTH 16
#define MAX_FILE_SIZE 1024

typedef struct {
    char filename[MAX_FILENAME_LENGTH];
    int start_block;
    int size;
    char data[MAX_FILE_SIZE];
} DirectoryEntry;

typedef struct {
    char volume_name[MAX_FILENAME_LENGTH];
    int total_blocks;
    int free_blocks;
    DirectoryEntry* directory;
    char current_path[MAX_FILENAME_LENGTH];
} FileSystem;

FileSystem fs;

void formatDisk() {
    printf("Enter volume name: ");
    scanf("%s", fs.volume_name);
    printf("Enter total number of blocks: ");
    scanf("%d", &fs.total_blocks);
    fs.free_blocks = fs.total_blocks;
    fs.directory = (DirectoryEntry*)malloc(sizeof(DirectoryEntry) * fs.total_blocks);
    for (int i = 0; i < fs.total_blocks; i++) {
        strcpy(fs.directory[i].filename, "");
        fs.directory[i].start_block = -1;
        fs.directory[i].size = 0;
    }
    strcpy(fs.current_path, "/");
    printf("Disk formatted successfully.\n");
}

void createDirectory() {
    char dirname[MAX_FILENAME_LENGTH];
    printf("Enter directory name: ");
    scanf("%s", dirname);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, "") == 0) {
            strcpy(fs.directory[i].filename, dirname);
            fs.directory[i].start_block = -1;
            fs.directory[i].size = 0;
            printf("Directory created successfully.\n");
            return;
        }
    }
    printf("No free space for directory creation.\n");
}

void changeDirectory() {
    char dirname[MAX_FILENAME_LENGTH];
    printf("Enter directory name: ");
    scanf("%s", dirname);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, dirname) == 0) {
            strcat(fs.current_path, dirname);
            strcat(fs.current_path, "/");
            
            printf("Directory changed to '%s'.\n", fs.current_path);
            return;
        }
    }
    printf("Directory '%s' not found.\n", dirname);
}

void renameDirectory() {
    char oldname[MAX_FILENAME_LENGTH], newname[MAX_FILENAME_LENGTH];
    printf("Enter old directory name: ");
    scanf("%s", oldname);
    printf("Enter new directory name: ");
    scanf("%s", newname);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, oldname) == 0) {
            strcpy(fs.directory[i].filename, newname);
            
            printf("Directory renamed successfully.\n");
            return;
        }
    }
    printf("Directory '%s' not found.\n", oldname);
}

void displayDirectory() {
    printf("Current Disk: %s\n", fs.volume_name);
    printf("Current Path: %s\n", fs.current_path);
    printf("Directory listing:\n");
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, "") != 0) {
            printf("- %s\n", fs.directory[i].filename);
        }
    }
}

void deleteDirectory() {
    char dirname[MAX_FILENAME_LENGTH];
    printf("Enter directory name: ");
    scanf("%s", dirname);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, dirname) == 0) {
            strcpy(fs.directory[i].filename, "");
            
            printf("Directory deleted successfully.\n");
            return;
        }
    }
    printf("Directory '%s' not found.\n", dirname);
}

void createFile() {
    char filename[MAX_FILENAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", filename);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, "") == 0) {
            strcpy(fs.directory[i].filename, filename);
            fs.directory[i].start_block = i;
            fs.directory[i].size = 0;
            fs.directory[i].data[0] = '\0'; 
            fs.free_blocks--;
            printf("File created successfully.\n");
            return;
        }
    }
    printf("No free space for file creation.\n");
}

void renameFile() {
    char oldname[MAX_FILENAME_LENGTH], newname[MAX_FILENAME_LENGTH];
    printf("Enter old file name: ");
    scanf("%s", oldname);
    printf("Enter new file name: ");
    scanf("%s", newname);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, oldname) == 0) {
            strcpy(fs.directory[i].filename, newname);
            
            printf("File renamed successfully.\n");
            return;
        }
    }
    printf("File '%s' not found.\n", oldname);
}

void writeFile() {
    char filename[MAX_FILENAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", filename);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, filename) == 0) {
            int block_index = fs.directory[i].start_block;
            
            if (block_index == -1) {
                printf("File '%s' not found.\n", filename);
                return;
            }
            printf("Enter file content:\n");
            char content[MAX_FILE_SIZE];
            scanf("%s", content);
            strcpy(fs.current_path, filename);
            fs.directory[i].size = strlen(content);
            strcpy(fs.directory[i].data, content); 
            printf("File '%s' written successfully.\n", filename);
            return;
        }
    }
    
    printf("File '%s' not found.\n", filename);
}

void displayFileContent() {
    char filename[MAX_FILENAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", filename);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, filename) == 0) {
            printf("Content of file '%s':\n%s\n", filename, fs.directory[i].data);
            return;
        }
    }
    printf("File '%s' not found.\n", filename);
}

void deleteFile() {
    char filename[MAX_FILENAME_LENGTH];
    printf("Enter file name: ");
    scanf("%s", filename);
    for (int i = 0; i < fs.total_blocks; i++) {
        if (strcmp(fs.directory[i].filename, filename) == 0) {
            strcpy(fs.directory[i].filename, "");
            fs.directory[i].start_block = -1;
            fs.directory[i].size = 0;
            fs.free_blocks++;
            printf("File deleted successfully.\n");
            return;
        }
    }
    printf("File '%s' not found.\n", filename);
}

int main() {
    int choice;
    printf("----------------------------------- FAT16 File System ----------------------------------\n");
    printf("1. Format Disk         2. Create Directory    3. Change Directory    4. Rename Directory\n");
    printf("5. Display Directory   6. Delete Directory    7. Create File         8. Rename File\n");
    printf("9. Write File         10. Display File       11. Delete File         0. Exit\n");
    do {
        printf("\nCurrent Disk: %s   Current Path: %s\n", fs.volume_name, fs.current_path);  
        printf("Enter your choice: ");
        scanf("%d", &choice);
        switch (choice) {
            case 1: formatDisk(); break;
            case 2: createDirectory(); break;
            case 3: changeDirectory(); break;
            case 4: renameDirectory(); break;
            case 5: displayDirectory(); break;
            case 6: deleteDirectory(); break;
            case 7: createFile(); break;
            case 8: renameFile(); break;
            case 9: writeFile(); break;
            case 10: displayFileContent(); break;
            case 11: deleteFile(); break;
            case 0: break;
            default: printf("Invalid choice.\n");
        }
    } while (choice != 0);
    free(fs.directory);
    return 0;
}