Filesystem API

Filesystem API

API for implementing new file systems in ModuOS.

Overview

To add a new filesystem, implement these functions and register with VFS.

Required Functions

Mount/Unmount

int fs_mount(int drive_index, uint32_t partition_lba);
int fs_unmount(int handle);

Parameters:

• drive_index: Physical drive number
• partition_lba: Partition start sector
• handle: Filesystem handle

Returns: Handle on success, negative on error

File Operations

int fs_read_file(int handle, const char *path, void *buffer,
                 size_t buffer_size, size_t *bytes_read);

/* Note: filesystem drivers receive *real* filesystem paths like `/ModuOS/...`.
 * The special `$/...` namespace router is handled at a higher layer (fd/devfs path routing).
 */

int fs_stat(int handle, const char *path, fs_file_info_t *info);

int fs_file_exists(int handle, const char *path);

Directory Operations

int fs_list_directory(int handle, const char *path);

int fs_directory_exists(int handle, const char *path);

Data Structures

File Info

typedef struct {
    char name[260];           // Filename
    uint32_t size;            // Size in bytes
    int is_directory;         // 1=directory, 0=file
    uint32_t cluster;         // FS-specific data
} fs_file_info_t;

Example: Minimal Filesystem

// myfs.h
#ifndef MYFS_H
#define MYFS_H

int myfs_mount(int drive_index, uint32_t partition_lba);
int myfs_unmount(int handle);
int myfs_read_file(int handle, const char *path, void *buffer, 
                   size_t buffer_size, size_t *bytes_read);

#endif

// myfs.c
int myfs_mount(int drive_index, uint32_t partition_lba) {
    // 1. Read filesystem metadata
    // 2. Validate filesystem
    // 3. Allocate handle
    // 4. Return handle
}

int myfs_read_file(int handle, const char *path, void *buffer,
                   size_t buffer_size, size_t *bytes_read) {
    // 1. Parse path
    // 2. Locate file in filesystem
    // 3. Read file data
    // 4. Copy to buffer
    // 5. Return bytes read
}

Registering Filesystem

Add to fs.c:

switch (type) {
    case FS_TYPE_FAT32:
        return fat32_mount(drive_index, partition_lba);
    case FS_TYPE_ISO9660:
        return iso9660_mount(drive_index, partition_lba);
    case FS_TYPE_MYFS:
        return myfs_mount(drive_index, partition_lba);
}

Next Steps

• File Systems - Filesystem overview
• MDFS - MDFS-specific documentation
• Storage Drivers - Storage access