dmramfs

DMOD RAM File System - an in-memory file system module for the DMOD framework.

Overview

dmramfs is a RAM-based file system implementation that provides a fully featured, transient file system stored entirely in memory. It implements the DMOD File System Interface (DMFSI) and can be used with the DMOD Virtual File System (DMVFS).

Features

• In-Memory Storage: All files and directories are stored in RAM for fast access
• Full File Operations: Support for read, write, seek, truncate, and append operations
• Directory Support: Create, list, and navigate directories
• File Management: Rename, delete, and get file statistics
• DMFSI Compliant: Implements the standard DMOD file system interface

Dependencies

This module requires the following system libraries:

• dmlist - DMOD linked list library (fetched automatically via CMake FetchContent)

Building

mkdir build
cd build
cmake .. -DDMOD_MODE=DMOD_MODULE
cmake --build .

Usage

The module can be loaded and mounted using DMVFS:

#include "dmvfs.h"

// Initialize DMVFS
dmvfs_init(16, 32);

// Mount the RAM filesystem at /mnt
dmvfs_mount_fs("dmramfs", "/mnt", NULL);

// Use standard file operations
void* fp;
dmvfs_fopen(&fp, "/mnt/test.txt", DMFSI_O_CREAT | DMFSI_O_RDWR, 0, 0);
dmvfs_fwrite(fp, "Hello, World!", 13, NULL);
dmvfs_fclose(fp);

// Unmount when done
dmvfs_unmount_fs("/mnt");
dmvfs_deinit();

API

The module implements the full DMFSI interface:

File Operations

• _fopen - Open a file
• _fclose - Close a file
• _fread - Read from a file
• _fwrite - Write to a file
• _lseek - Seek to a position
• _tell - Get current position
• _eof - Check for end of file
• _size - Get file size
• _getc - Read a single character
• _putc - Write a single character
• _sync - Sync file (no-op for RAM FS)
• _fflush - Flush buffers (no-op for RAM FS)

Directory Operations

• _mkdir - Create a directory
• _opendir - Open a directory for reading
• _readdir - Read directory entries
• _closedir - Close a directory
• _direxists - Check if directory exists

File Management

• _stat - Get file/directory statistics
• _unlink - Delete a file
• _rename - Rename a file

Testing

Tests are run using the fs_tester tool from the dmvfs repository:

# Build dmvfs with tests
cd /path/to/dmvfs
mkdir build && cd build
cmake .. -DDMOD_MODE=DMOD_SYSTEM -DDMVFS_BUILD_TESTS=ON
cmake --build .

# Run tests against dmramfs
./tests/fs_tester /path/to/dmramfs.dmf

Known Issues

When running fs_tester, you may see [ERROR] Failed to close file messages even though tests pass. This is due to a return value convention mismatch in the dmvfs layer (which expects boolean success/failure) versus the DMFSI interface convention (which uses 0 for success). The actual file operations work correctly despite these messages.

License

See LICENSE file for details.