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/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim:set ts=2 sw=2 sts=2 et filetype=javascript
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
"use strict";
module.metadata = {
"stability": "stable"
};
const { Cc, Ci } = require("chrome");
const file = require("./io/file");
const prefs = require("./preferences/service");
const jpSelf = require("./self");
const timer = require("./timers");
const unload = require("./system/unload");
const { emit, on, off } = require("./event/core");
const WRITE_PERIOD_PREF = "extensions.addon-sdk.simple-storage.writePeriod";
const WRITE_PERIOD_DEFAULT = 300000; // 5 minutes
const QUOTA_PREF = "extensions.addon-sdk.simple-storage.quota";
const QUOTA_DEFAULT = 5242880; // 5 MiB
const JETPACK_DIR_BASENAME = "jetpack";
Object.defineProperties(exports, {
storage: {
enumerable: true,
get: function() { return manager.root; },
set: function(value) { manager.root = value; }
},
quotaUsage: {
get: function() { return manager.quotaUsage; }
}
});
// A generic JSON store backed by a file on disk. This should be isolated
// enough to move to its own module if need be...
function JsonStore(options) {
this.filename = options.filename;
this.quota = options.quota;
this.writePeriod = options.writePeriod;
this.onOverQuota = options.onOverQuota;
this.onWrite = options.onWrite;
unload.ensure(this);
this.writeTimer = timer.setInterval(this.write.bind(this),
this.writePeriod);
}
JsonStore.prototype = {
// The store's root.
get root() {
return this.isRootInited ? this._root : {};
},
// Performs some type checking.
set root(val) {
let types = ["array", "boolean", "null", "number", "object", "string"];
if (types.indexOf(typeof(val)) < 0) {
throw new Error("storage must be one of the following types: " +
types.join(", "));
}
this._root = val;
return val;
},
// True if the root has ever been set (either via the root setter or by the
// backing file's having been read).
get isRootInited() {
return this._root !== undefined;
},
// Percentage of quota used, as a number [0, Inf). > 1 implies over quota.
// Undefined if there is no quota.
get quotaUsage() {
return this.quota > 0 ?
JSON.stringify(this.root).length / this.quota :
undefined;
},
// Removes the backing file and all empty subdirectories.
purge: function JsonStore_purge() {
try {
// This'll throw if the file doesn't exist.
file.remove(this.filename);
let parentPath = this.filename;
do {
parentPath = file.dirname(parentPath);
// This'll throw if the dir isn't empty.
file.rmdir(parentPath);
} while (file.basename(parentPath) !== JETPACK_DIR_BASENAME);
}
catch (err) {}
},
// Initializes the root by reading the backing file.
read: function JsonStore_read() {
try {
let str = file.read(this.filename);
// Ideally we'd log the parse error with console.error(), but logged
// errors cause tests to fail. Supporting "known" errors in the test
// harness appears to be non-trivial. Maybe later.
this.root = JSON.parse(str);
}
catch (err) {
this.root = {};
}
},
// If the store is under quota, writes the root to the backing file.
// Otherwise quota observers are notified and nothing is written.
write: function JsonStore_write() {
if (this.quotaUsage > 1)
this.onOverQuota(this);
else
this._write();
},
// Cleans up on unload. If unloading because of uninstall, the store is
// purged; otherwise it's written.
unload: function JsonStore_unload(reason) {
timer.clearInterval(this.writeTimer);
this.writeTimer = null;
if (reason === "uninstall")
this.purge();
else
this._write();
},
// True if the root is an empty object.
get _isEmpty() {
if (this.root && typeof(this.root) === "object") {
let empty = true;
for (let key in this.root) {
empty = false;
break;
}
return empty;
}
return false;
},
// Writes the root to the backing file, notifying write observers when
// complete. If the store is over quota or if it's empty and the store has
// never been written, nothing is written and write observers aren't notified.
_write: function JsonStore__write() {
// Don't write if the root is uninitialized or if the store is empty and the
// backing file doesn't yet exist.
if (!this.isRootInited || (this._isEmpty && !file.exists(this.filename)))
return;
// If the store is over quota, don't write. The current under-quota state
// should persist.
if (this.quotaUsage > 1)
return;
// Finally, write.
let stream = file.open(this.filename, "w");
try {
stream.writeAsync(JSON.stringify(this.root), function writeAsync(err) {
if (err)
console.error("Error writing simple storage file: " + this.filename);
else if (this.onWrite)
this.onWrite(this);
}.bind(this));
}
catch (err) {
// writeAsync closes the stream after it's done, so only close on error.
stream.close();
}
}
};
// This manages a JsonStore singleton and tailors its use to simple storage.
// The root of the JsonStore is lazy-loaded: The backing file is only read the
// first time the root's gotten.
let manager = ({
jsonStore: null,
// The filename of the store, based on the profile dir and extension ID.
get filename() {
let storeFile = Cc["@mozilla.org/file/directory_service;1"].
getService(Ci.nsIProperties).
get("ProfD", Ci.nsIFile);
storeFile.append(JETPACK_DIR_BASENAME);
storeFile.append(jpSelf.id);
storeFile.append("simple-storage");
file.mkpath(storeFile.path);
storeFile.append("store.json");
return storeFile.path;
},
get quotaUsage() {
return this.jsonStore.quotaUsage;
},
get root() {
if (!this.jsonStore.isRootInited)
this.jsonStore.read();
return this.jsonStore.root;
},
set root(val) {
return this.jsonStore.root = val;
},
unload: function manager_unload() {
off(this);
},
new: function manager_constructor() {
let manager = Object.create(this);
unload.ensure(manager);
manager.jsonStore = new JsonStore({
filename: manager.filename,
writePeriod: prefs.get(WRITE_PERIOD_PREF, WRITE_PERIOD_DEFAULT),
quota: prefs.get(QUOTA_PREF, QUOTA_DEFAULT),
onOverQuota: emit.bind(null, exports, "OverQuota")
});
return manager;
}
}).new();
exports.on = on.bind(null, exports);
exports.removeListener = function(type, listener) {
off(exports, type, listener);
};
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