设计一个简单的Linux二级文件系统并给出代码

我可以提供一个简单的Linux二级文件系统的设计思路和代码示例。

设计思路：

这是一个基于内存的简单文件系统，它的主要组成部分包括：

1. SuperBlock：超级块，存储了整个文件系统的信息，如块大小、块数量、inode数量等。

2. Inode：索引节点，存储了文件或目录的元数据，如文件类型、权限、大小、创建时间、修改时间等。

3. Block：数据块，存储了文件的实际数据。

4. Directory Entry：目录项，存储了目录下的文件或目录的名称和对应的inode号。

代码示例：

以下是一个简单的Linux二级文件系统的代码示例，包括了SuperBlock、Inode、Block和Directory Entry的定义和相关操作函数的实现。

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

#define BLOCK_SIZE 512
#define INODE_SIZE 64
#define DIR_ENTRY_SIZE 32

/* SuperBlock结构体 */
struct SuperBlock {
    int block_size;        // 块大小
    int block_count;       // 块数量
    int inode_count;       // inode数量
    int free_block_count;  // 空闲块数量
    int free_inode_count;  // 空闲inode数量
};

/* Inode结构体 */
struct Inode {
    int type;              // 文件类型，0表示文件，1表示目录
    int permission;        // 权限
    int size;              // 大小
    int block_count;       // 数据块数量
    int blocks[10];        // 数据块指针
    time_t ctime;          // 创建时间
    time_t mtime;          // 修改时间
};

/* Block结构体 */
struct Block {
    char data[BLOCK_SIZE];
};

/* Directory Entry结构体 */
struct DirEntry {
    char name[28];         // 文件或目录名
    int inode;             // inode号
};

/* 初始化超级块 */
void init_super_block(struct SuperBlock *sb, int block_count, int inode_count) {
    sb->block_size = BLOCK_SIZE;
    sb->block_count = block_count;
    sb->inode_count = inode_count;
    sb->free_block_count = block_count;
    sb->free_inode_count = inode_count;
}

/* 初始化inode */
void init_inode(struct Inode *inode, int type, int permission) {
    inode->type = type;
    inode->permission = permission;
    inode->size = 0;
    inode->block_count = 0;
    memset(inode->blocks, 0, sizeof(inode->blocks));
    inode->ctime = time(NULL);
    inode->mtime = time(NULL);
}

/* 分配一个空闲inode */
int alloc_inode(struct SuperBlock *sb) {
    if (sb->free_inode_count == 0) {
        printf("Error: no free inode\n");
        return -1;
    }
    int inode = sb->inode_count - sb->free_inode_count;
    sb->free_inode_count--;
    return inode;
}

/* 分配一个空闲数据块 */
int alloc_block(struct SuperBlock *sb) {
    if (sb->free_block_count == 0) {
        printf("Error: no free block\n");
        return -1;
    }
    int block = sb->block_count - sb->free_block_count;
    sb->free_block_count--;
    return block;
}

/* 释放一个inode */
void free_inode(struct SuperBlock *sb, int inode) {
    sb->free_inode_count++;
}

/* 释放一个数据块 */
void free_block(struct SuperBlock *sb, int block) {
    sb->free_block_count++;
}

/* 获取inode对应的数据块 */
int get_block(struct Inode *inode, int index) {
    if (index < 10) {
        return inode->blocks[index];
    }
    printf("Error: file too large\n");
    return -1;
}

/* 设置inode对应的数据块 */
void set_block(struct Inode *inode, int index, int block) {
    if (index < 10) {
        inode->blocks[index] = block;
        inode->block_count++;
    } else {
        printf("Error: file too large\n");
    }
}

/* 读取数据块 */
void read_block(struct Block *block, int fd, int offset) {
    fseek(fd, offset * BLOCK_SIZE, SEEK_SET);
    fread(block->data, BLOCK_SIZE, 1, fd);
}

/* 写入数据块 */
void write_block(struct Block *block, int fd, int offset) {
    fseek(fd, offset * BLOCK_SIZE, SEEK_SET);
    fwrite(block->data, BLOCK_SIZE, 1, fd);
}

/* 根据inode号读取inode */
void read_inode(struct Inode *inode, int fd, int inode_num) {
    fseek(fd, sizeof(struct SuperBlock) + inode_num * INODE_SIZE, SEEK_SET);
    fread(inode, INODE_SIZE, 1, fd);
}

/* 根据inode号写入inode */
void write_inode(struct Inode *inode, int fd, int inode_num) {
    fseek(fd, sizeof(struct SuperBlock) + inode_num * INODE_SIZE, SEEK_SET);
    fwrite(inode, INODE_SIZE, 1, fd);
}

/* 根据目录项名字查找inode号 */
int find_dir_entry(struct Block *block, char *name) {
    int i;
    struct DirEntry *de;
    for (i = 0; i < BLOCK_SIZE / DIR_ENTRY_SIZE; i++) {
        de = (struct DirEntry *)(block->data + i * DIR_ENTRY_SIZE);
        if (strcmp(de->name, name) == 0) {
            return de->inode;
        }
    }
    return -1;
}

/* 在目录下创建一个文件 */
void create_file(struct SuperBlock *sb, struct Inode *dir_inode, char *name, int permission) {
    if (dir_inode->type != 1) {
        printf("Error: not a directory\n");
        return;
    }
    int inode_num = alloc_inode(sb);
    if (inode_num == -1) {
        return;
    }
    int block_num = alloc_block(sb);
    if (block_num == -1) {
        free_inode(sb, inode_num);
        return;
    }
    struct Inode inode;
    init_inode(&inode, 0, permission);
    set_block(&inode, 0, block_num);
    write_inode(&inode, fd, inode_num);
    struct Block block;
    memset(&block, 0, sizeof(block));
    write_block(&block, fd, block_num);
    struct DirEntry de;
    strncpy(de.name, name, 28);
    de.inode = inode_num;
    read_block(&block, fd, 0);
    struct DirEntry *pde = (struct DirEntry *)block.data;
    int i;
    for (i = 0; i < BLOCK_SIZE / DIR_ENTRY_SIZE; i++) {
        if (pde->inode == 0) {
            memcpy(pde, &de, DIR_ENTRY_SIZE);
            write_block(&block, fd, 0);
            return;
        }
        pde++;
    }
    printf("Error: directory is full\n");
    free_inode(sb, inode_num);
    free_block(sb, block_num);
}

/* 在目录下创建一个目录 */
void create_dir(struct SuperBlock *sb, struct Inode *dir_inode, char *name, int permission) {
    if (dir_inode->type != 1) {
        printf("Error: not a directory\n");
        return;
    }
    int inode_num = alloc_inode(sb);
    if (inode_num == -1) {
        return;
    }
    int block_num = alloc_block(sb);
    if (block_num == -1) {
        free_inode(sb, inode_num);
        return;
    }
    struct Inode inode;
    init_inode(&inode, 1, permission);
    set_block(&inode, 0, block_num);
    write_inode(&inode, fd, inode_num);
    struct Block block;
    memset(&block, 0, sizeof(block));
    write_block(&block, fd, block_num);
    struct DirEntry de;
    strncpy(de.name, name, 28);
    de.inode = inode_num;
    read_block(&block, fd, 0);
    struct DirEntry *pde = (struct DirEntry *)block.data;
    int i;
    for (i = 0; i < BLOCK_SIZE / DIR_ENTRY_SIZE; i++) {
        if (pde->inode == 0) {
            memcpy(pde, &de, DIR_ENTRY_SIZE);
            write_block(&block, fd, 0);
            return;
        }
        pde++;
    }
    printf("Error: directory is full\n");
    free_inode(sb, inode_num);
    free_block(sb, block_num);
}

/* 初始化文件系统 */
void init_filesystem(char *filename, int block_count, int inode_count) {
    FILE *fd = fopen(filename, "w+");
    if (fd == NULL) {
        printf("Error: cannot create file system\n");
        return;
    }
    struct SuperBlock sb;
    init_super_block(&sb, block_count, inode_count);
    fwrite(&sb, sizeof(sb), 1, fd);
    struct Inode root_inode;
    init_inode(&root_inode, 1, 0777);
    write_inode(&root_inode, fd, 0);
    struct Block root_block;
    memset(&root_block, 0, sizeof(root_block));
    struct DirEntry de;
    strncpy(de.name, ".", 28);
    de.inode = 0;
    memcpy(root_block.data, &de, DIR_ENTRY_SIZE);
    strncpy(de.name, "..", 28);
    de.inode = 0;
    memcpy(root_block.data + DIR_ENTRY_SIZE, &de, DIR_ENTRY_SIZE);
    write_block(&root_block, fd, 0);
    fclose(fd);
}

/* 打开文件系统 */
void open_filesystem(char *filename) {
    fd = fopen(filename, "r+");
    if (fd == NULL) {
        printf("Error: cannot open file system\n");
        return;
    }
    fread(&sb, sizeof(sb), 1, fd);
}

/* 关闭文件系统 */
void close_filesystem() {
    fclose(fd);
}

/* 创建文件 */
void create_file(char *path, int permission) {
    int inode_num = 0;
    char *p = strtok(path, "/");
    while (p != NULL) {
        struct Inode inode;
        read_inode(&inode, fd, inode_num);
        int block_num = get_block(&inode, 0);
        struct Block block;
        read_block(&block, fd, block_num);
        inode_num = find_dir_entry(&block, p);
        if (inode_num == -1) {
            create_file(&sb, &inode, p, permission);
            return;
        }
        p = strtok(NULL, "/");
    }
    printf("Error: file already exists\n");
}

/* 创建目录 */
void create_dir(char *path, int permission) {
    int inode_num = 0;
    char *p = strtok(path, "/");
    while (p != NULL) {
        struct Inode inode;
        read_inode(&inode, fd, inode_num);
        int block_num = get_block(&inode, 0);
        struct Block block;
        read_block(&block, fd, block_num);
        inode_num = find_dir_entry(&block, p);
        if (inode_num == -1) {
            create_dir(&sb, &inode, p, permission);
            return;
        }
        p = strtok(NULL, "/");
    }
    printf("Error: directory already exists\n");
}

/* 删除文件 */
void delete_file(char *path) {
    int inode_num = 0;
    char *p = strtok(path, "/");
    while (p != NULL) {
        struct Inode inode;
        read_inode(&inode, fd, inode_num);
        int block_num = get_block(&inode, 0);
        struct Block block;
        read_block(&block, fd, block_num);
        inode_num = find_dir_entry(&block, p);
        if (inode_num == -1) {
            printf("Error: file not found\n");
            return;
        }
        p = strtok(NULL, "/");
    }
    struct Inode inode;
    read_inode(&inode, fd, inode_num);
    if (inode.type != 0) {
        printf("Error: not a file\n");
        return;
    }
    free_inode(&sb, inode_num);
    int i;
    for (i = 0; i < inode.block_count; i++) {
        free_block(&sb, inode.blocks[i]);
    }
}

/* 删除目录 */
void delete_dir(char *path) {
    int inode_num = 0;
    char *p = strtok(path, "/");
    while (p != NULL) {
        struct Inode inode;
        read_inode(&inode, fd, inode_num);
        int block_num = get_block(&inode, 0);
        struct Block block;
        read_block(&block, fd, block_num);
        inode_num = find_dir_entry(&block, p);
        if (inode_num == -1) {
            printf("Error: directory not found\n");
            return;
        }
        p = strtok(NULL, "/");
    }
    struct Inode inode;
    read_inode(&inode, fd, inode_num);
    if (inode.type != 1) {
        printf("Error: not a directory\n");
        return;
    }
    struct Block block;
    read_block(&block, fd, inode.blocks[0]);
    struct DirEntry *de = (struct DirEntry *)block.data;
    int i;
    for (i = 0; i < BLOCK_SIZE / DIR_ENTRY_SIZE; i++) {
        if (de->inode != 0) {
            struct Inode child_inode;
            read_inode(&child_inode, fd, de->inode);
            if (child_inode.type == 0) {
                free_inode(&sb, de->inode);
                int j;
                for (j = 0; j < child_inode.block_count; j++) {
                    free_block(&sb, child_inode.blocks[j]);
                }
            } else {
                delete_dir(child_inode.blocks[0]);
                free_inode(&sb, de->inode);
                free_block(&sb, child_inode.blocks[0]);
            }
        }
        de++;
    }
    free_inode(&sb, inode_num);
    free_block(&sb, inode.blocks[0]);
}

/* 列出目录下的文件和目录 */
void list_dir(char *path) {
    int inode_num = 0;
    char *p = strtok(path, "/");
    while (p != NULL) {
        struct Inode inode;
        read_inode(&inode, fd, inode_num);
        int block_num = get_block(&inode, 0);
        struct Block block;
        read_block(&block, fd, block_num);
        inode_num = find_dir_entry(&block, p);
        if (inode_num == -1) {
            printf("Error: directory not found\n");
            return;
        }
        p = strtok(NULL, "/");
    }
    struct Inode inode;
    read_inode(&inode, fd, inode_num);
    if (inode.type != 1) {
        printf("Error: not a directory\n");
        return;
    }
    struct Block block;
    read_block(&block, fd, inode.blocks[0]);
    struct DirEntry *de = (struct DirEntry *)block.data;
    int i;
    for (i = 0; i < BLOCK_SIZE / DIR_ENTRY_SIZE; i++) {
        if (de->inode != 0) {
            struct Inode child_inode;
            read_inode(&child_inode, fd, de->inode);
            if (child_inode.type == 0) {
                printf("%s\n", de->name);
            } else {
                printf("%s/\n", de->name);
            }
        }
        de++;
    }
}

int main() {
    init_filesystem("test.fs", 1024, 128);
    open_filesystem("test.fs");
    create_dir("/", 0777);
    create_file("/test.txt", 0666);
    list_dir("/");
    delete_file("/test.txt");
    delete_dir("/");
    close_filesystem();
    return 0;
}

以上代码仅供参考，可能存在不完善的地方，仅供学习和交流。