The filesysteminfile allows you to create and update filesystems for use as storage devices. 

filesysteminfile IDL

interface FileSystemInFile {
    constructor(String path);
    Promise<String> getFilename();
    Promise<long long> getSize();
    Promise<void> format(String fileSystem);
    Promise<void> mount();
    Promise<void> unmount();
};

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Object Creation

To create a filesysteminfile object, load the @brightsign/filesysteminfile module using the Node.js® require() method:

var FileSystemInFile = require('@brightsign/filesysteminfile');
var fsif = new FileSystemInFile("/storage/sd/usbstore.img"); // Node's native 'fs' can create an .img file

filesysteminfile

Use this interface to configure a filesysteminfile.

getFilename()
Promise<String> getFilename()

Gets the name of the file that was used to create FileSystemInFile.

getSize()
Promise<long long> getSize()

Retrieves the size (in bytes) of the filesystem file used to create the FileSystemInFile class.

format()
Promise<void> format(String fileSystem)

Creates the specified filesystem in a file that already exists. The supported filesystem types are "fat" and "exfat".

mount()
Promise<String> mount()

Mounts the filesystem. There is no need to format the filesystem if it already exists and is formatted.

The return string is filepath and the return value is the path to where the filesystem has been mounted. It cannot be mounted more than once.

unmount()
Promise<void> unmount()

Unmounts the filesystem.

Example

The example below creates a file system, formats, mounts, and unmounts it using the npm package fs, 

const fs = require('fs');
const FileSystemInFile = require('@brightsign/filesysteminfile');

var fsif;
var fd;

open()
.then(function(fileDescriptor) {
	fd = fileDescriptor;
	return write(fd);
})
.then(function(bytes) {
	console.log(`${bytes} written to new file`);
	return close(fd);
})
.then(function() {
	// Create FileSystemInFile using the backing file
	fsif = new FileSystemInFile('/storage/sd/usbstore');

	return format();
})
.then(function() {
	return mount();
})
.then(function() {
	/* This is where you can actually do stuff with the mounted filesystem. */

	// Unmount the mounted file after 10 seconds
	setTimeout(function() {
		return unmount();
	}, 10000);
})
.catch(function(error) {
	console.log(JSON.stringify(error));
});


// Create a writable file for the file system
function open() {
	return new Promise(function(resolve, reject) {
		fs.open('/storage/sd/usbstore', 'w', function(error, fd) {
			if (error) reject(error);
			resolve(fd);
		});	
	});
};

// Write a buffer allocating 1GB of disk space for the file
function write(fd) {
	return new Promise(function(resolve, reject) {
		fs.write(fd, Buffer.alloc(1), 0, 1, (1024*1024*1024) - 1, function(error, bytesWritten) {
			if (error) reject(error);
			resolve(bytesWritten);
		});
	});
};

// Close the created file
function close(fd) {
	return new Promise(function(resolve, reject) {
		fs.close(fd, function(error) {
			if (error) reject(error);
			resolve();
		});
	});
};

// Format the file system
function format() {
	return new Promise(function(resolve, reject) {
		fsif.format("exfat")
		.then(function() {
		  console.log('Filesystem formatted');
		  resolve();
		})
		.catch(function(error) {
		  reject(error);
		});		
	});
};


// Mount the filesystem internally
function mount() {
	return new Promise(function(resolve, reject) {
		fsif.mount()
		.then(function(mount_point) {
		  console.log('Filesystem mounted' + mount_point);
		  resolve();
		})
		.catch(function(error) {
		  reject(error);
		});
	});
};

// Unmount filesystem from internal mount point. Only can unmount a mounted file
function unmount() {
	return new Promise(function(resolve, reject) {
		fsif.unmount()
		.then(function() {
		  console.log('Filesystem unmounted');
		  resolve();
		})
		.catch(function(error) {
		  reject(error);
		});
	});
};

You can also reference our public github example which uses a BrightSign device as a filesystem over USB.