369 lines
11 KiB
JavaScript
369 lines
11 KiB
JavaScript
var { promisify } = require('es6-promisify');
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var isNullPath = require('../path.js').isNull;
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var nop = require('../shared.js').nop;
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var Constants = require('../constants.js');
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var FILE_SYSTEM_NAME = Constants.FILE_SYSTEM_NAME;
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var FS_FORMAT = Constants.FS_FORMAT;
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var FS_READY = Constants.FS_READY;
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var FS_PENDING = Constants.FS_PENDING;
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var FS_ERROR = Constants.FS_ERROR;
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var FS_NODUPEIDCHECK = Constants.FS_NODUPEIDCHECK;
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var providers = require('../providers/index.js');
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var Shell = require('../shell/shell.js');
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var Intercom = require('../../lib/intercom.js');
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var FSWatcher = require('../fs-watcher.js');
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var Errors = require('../errors.js');
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var defaultGuidFn = require('../shared.js').guid;
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var STDIN = Constants.STDIN;
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var STDOUT = Constants.STDOUT;
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var STDERR = Constants.STDERR;
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var FIRST_DESCRIPTOR = Constants.FIRST_DESCRIPTOR;
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// The core fs operations live on impl
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var impl = require('./implementation.js');
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// node.js supports a calling pattern that leaves off a callback.
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function maybeCallback(callback) {
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if(typeof callback === 'function') {
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return callback;
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}
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return function(err) {
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if(err) {
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throw err;
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}
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};
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}
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// Default callback that logs an error if passed in
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function defaultCallback(err) {
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if(err) {
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/* eslint no-console: 0 */
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console.error('Filer error: ', err);
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}
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}
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/**
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* FileSystem
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*
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* A FileSystem takes an `options` object, which can specify a number of,
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* options. All options are optional, and include:
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*
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* name: the name of the file system, defaults to "local"
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*
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* flags: one or more flags to use when creating/opening the file system.
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* For example: "FORMAT" will cause the file system to be formatted.
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* No explicit flags are set by default.
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*
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* provider: an explicit storage provider to use for the file
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* system's database context provider. A number of context
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* providers are included (see /src/providers), and users
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* can write one of their own and pass it in to be used.
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* By default an IndexedDB provider is used.
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*
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* guid: a function for generating unique IDs for nodes in the filesystem.
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* Use this to override the built-in UUID generation. (Used mainly for tests).
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*
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* callback: a callback function to be executed when the file system becomes
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* ready for use. Depending on the context provider used, this might
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* be right away, or could take some time. The callback should expect
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* an `error` argument, which will be null if everything worked. Also
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* users should check the file system's `readyState` and `error`
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* properties to make sure it is usable.
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*/
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function FileSystem(options, callback) {
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options = options || {};
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callback = callback || defaultCallback;
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var flags = options.flags || [];
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var guid = options.guid ? options.guid : defaultGuidFn;
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var provider = options.provider || new providers.Default(options.name || FILE_SYSTEM_NAME);
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// If we're given a provider, match its name unless we get an explicit name
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var name = options.name || provider.name;
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var forceFormatting = flags.includes(FS_FORMAT);
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var fs = this;
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fs.readyState = FS_PENDING;
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fs.name = name;
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fs.error = null;
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fs.stdin = STDIN;
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fs.stdout = STDOUT;
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fs.stderr = STDERR;
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// Expose Node's fs.constants to users
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fs.constants = Constants.fsConstants;
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// Expose Shell constructor
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this.Shell = Shell.bind(undefined, this);
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// Safely expose the list of open files and file
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// descriptor management functions
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var openFiles = {};
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var nextDescriptor = FIRST_DESCRIPTOR;
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Object.defineProperty(this, 'openFiles', {
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get: function() { return openFiles; }
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});
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this.allocDescriptor = function(openFileDescription) {
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var fd = nextDescriptor ++;
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openFiles[fd] = openFileDescription;
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return fd;
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};
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this.releaseDescriptor = function(fd) {
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delete openFiles[fd];
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};
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// Safely expose the operation queue
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var queue = [];
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this.queueOrRun = function(operation) {
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var error;
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if(FS_READY == fs.readyState) {
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operation.call(fs);
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} else if(FS_ERROR == fs.readyState) {
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error = new Errors.EFILESYSTEMERROR('unknown error');
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} else {
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queue.push(operation);
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}
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return error;
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};
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function runQueued() {
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queue.forEach(function(operation) {
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operation.call(this);
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}.bind(fs));
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queue = null;
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}
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// We support the optional `options` arg from node, but ignore it
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this.watch = function(filename, options, listener) {
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if(isNullPath(filename)) {
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throw new Error('Path must be a string without null bytes.');
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}
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if(typeof options === 'function') {
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listener = options;
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options = {};
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}
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options = options || {};
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listener = listener || nop;
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var watcher = new FSWatcher();
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watcher.start(filename, false, options.recursive);
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watcher.on('change', listener);
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return watcher;
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};
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// Deal with various approaches to node ID creation
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function wrappedGuidFn(context) {
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return function(callback) {
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// Skip the duplicate ID check if asked to
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if(flags.includes(FS_NODUPEIDCHECK)) {
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callback(null, guid());
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return;
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}
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// Otherwise (default) make sure this id is unused first
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function guidWithCheck(callback) {
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var id = guid();
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context.getObject(id, function(err, value) {
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if(err) {
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callback(err);
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return;
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}
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// If this id is unused, use it, otherwise find another
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if(!value) {
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callback(null, id);
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} else {
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guidWithCheck(callback);
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}
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});
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}
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guidWithCheck(callback);
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};
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}
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// Let other instances (in this or other windows) know about
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// any changes to this fs instance.
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function broadcastChanges(changes) {
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if(!changes.length) {
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return;
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}
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var intercom = Intercom.getInstance();
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changes.forEach(function(change) {
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intercom.emit(change.event, change.path);
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});
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}
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// Open file system storage provider
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provider.open(function(err) {
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function complete(error) {
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function wrappedContext(methodName) {
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var context = provider[methodName]();
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context.flags = flags;
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context.changes = [];
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context.guid = wrappedGuidFn(context);
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// When the context is finished, let the fs deal with any change events
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context.close = function() {
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var changes = context.changes;
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broadcastChanges(changes);
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changes.length = 0;
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};
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return context;
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}
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// Wrap the provider so we can extend the context with fs flags and
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// an array of changes (e.g., watch event 'change' and 'rename' events
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// for paths updated during the lifetime of the context). From this
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// point forward we won't call open again, so it's safe to drop it.
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fs.provider = {
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openReadWriteContext: function() {
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return wrappedContext('getReadWriteContext');
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},
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openReadOnlyContext: function() {
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return wrappedContext('getReadOnlyContext');
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}
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};
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if(error) {
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fs.readyState = FS_ERROR;
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} else {
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fs.readyState = FS_READY;
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}
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runQueued();
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callback(error, fs);
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}
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if(err) {
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return complete(err);
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}
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var context = provider.getReadWriteContext();
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context.guid = wrappedGuidFn(context);
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// Mount the filesystem, formatting if necessary
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if(forceFormatting) {
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// Wipe the storage provider, then write root block
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context.clear(function(err) {
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if(err) {
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return complete(err);
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}
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impl.ensureRootDirectory(context, complete);
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});
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} else {
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// Use existing (or create new) root and mount
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impl.ensureRootDirectory(context, complete);
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}
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});
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FileSystem.prototype.promises = {};
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/**
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* Public API for FileSystem. All node.js methods that are
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* exposed on fs.promises include `promise: true`. We also
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* include our own extra methods, but skip the fd versions
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* to match node.js, which puts these on a FileHandle object.
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*/
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[
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{ name: 'open', promises: true },
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{ name: 'access', promises: true },
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{ name: 'chmod', promises: true },
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{ name: 'fchmod' },
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{ name: 'chown', promises: true },
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{ name: 'fchown' },
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{ name: 'close' },
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{ name: 'mknod', promises: true },
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{ name: 'mkdir', promises: true },
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{ name: 'rmdir', promises: true },
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{ name: 'stat', promises: true },
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{ name: 'fstat' },
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{ name: 'link', promises: true },
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{ name: 'unlink', promises: true },
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{ name: 'read' },
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{ name: 'readFile', promises: true },
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{ name: 'write' },
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{ name: 'writeFile', promises: true },
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{ name: 'appendFile', promises: true },
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{ name: 'exists' },
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{ name: 'lseek' },
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{ name: 'readdir', promises: true },
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{ name: 'rename', promises: true },
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{ name: 'readlink', promises: true },
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{ name: 'symlink', promises: true },
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{ name: 'lstat', promises: true },
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{ name: 'truncate', promises: true },
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{ name: 'ftruncate' },
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{ name: 'utimes', promises: true },
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{ name: 'futimes' },
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{ name: 'setxattr', promises: true },
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{ name: 'getxattr', promises: true },
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{ name: 'fsetxattr' },
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{ name: 'fgetxattr' },
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{ name: 'removexattr', promises: true },
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{ name: 'fremovexattr' }
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].forEach(function(method) {
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var methodName = method.name;
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var shouldPromisify = method.promises === true;
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FileSystem.prototype[methodName] = function() {
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var fs = this;
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var args = Array.prototype.slice.call(arguments, 0);
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var lastArgIndex = args.length - 1;
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// We may or may not get a callback, and since node.js supports
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// fire-and-forget style fs operations, we have to dance a bit here.
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var missingCallback = typeof args[lastArgIndex] !== 'function';
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var callback = maybeCallback(args[lastArgIndex]);
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var error = fs.queueOrRun(function() {
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var context = fs.provider.openReadWriteContext();
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// Fail early if the filesystem is in an error state (e.g.,
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// provider failed to open.
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if(FS_ERROR === fs.readyState) {
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var err = new Errors.EFILESYSTEMERROR('filesystem unavailable, operation canceled');
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return callback.call(fs, err);
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}
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// Wrap the callback so we can explicitly close the context
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function complete() {
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context.close();
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callback.apply(fs, arguments);
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}
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// Either add or replace the callback with our wrapper complete()
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if(missingCallback) {
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args.push(complete);
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} else {
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args[lastArgIndex] = complete;
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}
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// Forward this call to the impl's version, using the following
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// call signature, with complete() as the callback/last-arg now:
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// fn(fs, context, arg0, arg1, ... , complete);
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var fnArgs = [fs, context].concat(args);
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impl[methodName].apply(null, fnArgs);
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});
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if(error) {
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callback(error);
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}
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};
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// Add to fs.promises if appropriate
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if(shouldPromisify) {
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FileSystem.prototype.promises[methodName] = promisify(FileSystem.prototype[methodName].bind(fs));
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}
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});
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}
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// Expose storage providers on FileSystem constructor
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FileSystem.providers = providers;
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module.exports = FileSystem;
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