filer/src/providers/memory.js

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var FILE_SYSTEM_NAME = require('../constants.js').FILE_SYSTEM_NAME;
// NOTE: prefer setImmediate to nextTick for proper recursion yielding.
// see https://github.com/js-platform/filer/pull/24
var asyncCallback = require('../../lib/async.js').setImmediate;
/**
* Make shared in-memory DBs possible when using the same name.
*/
var createDB = (function() {
var pool = {};
return function getOrCreate(name) {
if(!pool.hasOwnProperty(name)) {
pool[name] = {};
}
return pool[name];
};
}());
function MemoryContext(db, readOnly) {
this.readOnly = readOnly;
this.objectStore = db;
}
MemoryContext.prototype.clear = function(callback) {
if(this.readOnly) {
asyncCallback(function() {
callback("[MemoryContext] Error: write operation on read only context");
});
return;
}
var objectStore = this.objectStore;
Object.keys(objectStore).forEach(function(key){
delete objectStore[key];
});
asyncCallback(callback);
};
// Memory context doesn't care about differences between Object and Buffer
MemoryContext.prototype.getObject =
MemoryContext.prototype.getBuffer =
function(key, callback) {
var that = this;
asyncCallback(function() {
callback(null, that.objectStore[key]);
});
};
MemoryContext.prototype.putObject =
MemoryContext.prototype.putBuffer =
function(key, value, callback) {
if(this.readOnly) {
asyncCallback(function() {
callback("[MemoryContext] Error: write operation on read only context");
});
return;
}
this.objectStore[key] = value;
asyncCallback(callback);
};
MemoryContext.prototype.delete = function(key, callback) {
if(this.readOnly) {
asyncCallback(function() {
callback("[MemoryContext] Error: write operation on read only context");
});
return;
}
delete this.objectStore[key];
asyncCallback(callback);
};
function Memory(name) {
this.name = name || FILE_SYSTEM_NAME;
}
Memory.isSupported = function() {
return true;
};
Memory.prototype.open = function(callback) {
this.db = createDB(this.name);
asyncCallback(callback);
};
Memory.prototype.getReadOnlyContext = function() {
return new MemoryContext(this.db, true);
};
Memory.prototype.getReadWriteContext = function() {
return new MemoryContext(this.db, false);
};
module.exports = Memory;