'use strict'; var Binary = require('../core').BSON.Binary, ObjectID = require('../core').BSON.ObjectID; var Buffer = require('safe-buffer').Buffer; /** * Class for representing a single chunk in GridFS. * * @class * * @param file {GridStore} The {@link GridStore} object holding this chunk. * @param mongoObject {object} The mongo object representation of this chunk. * * @throws Error when the type of data field for {@link mongoObject} is not * supported. Currently supported types for data field are instances of * {@link String}, {@link Array}, {@link Binary} and {@link Binary} * from the bson module * * @see Chunk#buildMongoObject */ var Chunk = function(file, mongoObject, writeConcern) { if (!(this instanceof Chunk)) return new Chunk(file, mongoObject); this.file = file; var mongoObjectFinal = mongoObject == null ? {} : mongoObject; this.writeConcern = writeConcern || { w: 1 }; this.objectId = mongoObjectFinal._id == null ? new ObjectID() : mongoObjectFinal._id; this.chunkNumber = mongoObjectFinal.n == null ? 0 : mongoObjectFinal.n; this.data = new Binary(); if (typeof mongoObjectFinal.data === 'string') { var buffer = Buffer.alloc(mongoObjectFinal.data.length); buffer.write(mongoObjectFinal.data, 0, mongoObjectFinal.data.length, 'binary'); this.data = new Binary(buffer); } else if (Array.isArray(mongoObjectFinal.data)) { buffer = Buffer.alloc(mongoObjectFinal.data.length); var data = mongoObjectFinal.data.join(''); buffer.write(data, 0, data.length, 'binary'); this.data = new Binary(buffer); } else if (mongoObjectFinal.data && mongoObjectFinal.data._bsontype === 'Binary') { this.data = mongoObjectFinal.data; } else if (!Buffer.isBuffer(mongoObjectFinal.data) && !(mongoObjectFinal.data == null)) { throw Error('Illegal chunk format'); } // Update position this.internalPosition = 0; }; /** * Writes a data to this object and advance the read/write head. * * @param data {string} the data to write * @param callback {function(*, GridStore)} This will be called after executing * this method. The first parameter will contain null and the second one * will contain a reference to this object. */ Chunk.prototype.write = function(data, callback) { this.data.write(data, this.internalPosition, data.length, 'binary'); this.internalPosition = this.data.length(); if (callback != null) return callback(null, this); return this; }; /** * Reads data and advances the read/write head. * * @param length {number} The length of data to read. * * @return {string} The data read if the given length will not exceed the end of * the chunk. Returns an empty String otherwise. */ Chunk.prototype.read = function(length) { // Default to full read if no index defined length = length == null || length === 0 ? this.length() : length; if (this.length() - this.internalPosition + 1 >= length) { var data = this.data.read(this.internalPosition, length); this.internalPosition = this.internalPosition + length; return data; } else { return ''; } }; Chunk.prototype.readSlice = function(length) { if (this.length() - this.internalPosition >= length) { var data = null; if (this.data.buffer != null) { //Pure BSON data = this.data.buffer.slice(this.internalPosition, this.internalPosition + length); } else { //Native BSON data = Buffer.alloc(length); length = this.data.readInto(data, this.internalPosition); } this.internalPosition = this.internalPosition + length; return data; } else { return null; } }; /** * Checks if the read/write head is at the end. * * @return {boolean} Whether the read/write head has reached the end of this * chunk. */ Chunk.prototype.eof = function() { return this.internalPosition === this.length() ? true : false; }; /** * Reads one character from the data of this chunk and advances the read/write * head. * * @return {string} a single character data read if the the read/write head is * not at the end of the chunk. Returns an empty String otherwise. */ Chunk.prototype.getc = function() { return this.read(1); }; /** * Clears the contents of the data in this chunk and resets the read/write head * to the initial position. */ Chunk.prototype.rewind = function() { this.internalPosition = 0; this.data = new Binary(); }; /** * Saves this chunk to the database. Also overwrites existing entries having the * same id as this chunk. * * @param callback {function(*, GridStore)} This will be called after executing * this method. The first parameter will contain null and the second one * will contain a reference to this object. */ Chunk.prototype.save = function(options, callback) { var self = this; if (typeof options === 'function') { callback = options; options = {}; } self.file.chunkCollection(function(err, collection) { if (err) return callback(err); // Merge the options var writeOptions = { upsert: true }; for (var name in options) writeOptions[name] = options[name]; for (name in self.writeConcern) writeOptions[name] = self.writeConcern[name]; if (self.data.length() > 0) { self.buildMongoObject(function(mongoObject) { var options = { forceServerObjectId: true }; for (var name in self.writeConcern) { options[name] = self.writeConcern[name]; } collection.replaceOne({ _id: self.objectId }, mongoObject, writeOptions, function(err) { callback(err, self); }); }); } else { callback(null, self); } // }); }); }; /** * Creates a mongoDB object representation of this chunk. * * @param callback {function(Object)} This will be called after executing this * method. The object will be passed to the first parameter and will have * the structure: * *

 *        {
 *          '_id' : , // {number} id for this chunk
 *          'files_id' : , // {number} foreign key to the file collection
 *          'n' : , // {number} chunk number
 *          'data' : , // {bson#Binary} the chunk data itself
 *        }
 *        
* * @see MongoDB GridFS Chunk Object Structure */ Chunk.prototype.buildMongoObject = function(callback) { var mongoObject = { files_id: this.file.fileId, n: this.chunkNumber, data: this.data }; // If we are saving using a specific ObjectId if (this.objectId != null) mongoObject._id = this.objectId; callback(mongoObject); }; /** * @return {number} the length of the data */ Chunk.prototype.length = function() { return this.data.length(); }; /** * The position of the read/write head * @name position * @lends Chunk# * @field */ Object.defineProperty(Chunk.prototype, 'position', { enumerable: true, get: function() { return this.internalPosition; }, set: function(value) { this.internalPosition = value; } }); /** * The default chunk size * @constant */ Chunk.DEFAULT_CHUNK_SIZE = 1024 * 255; module.exports = Chunk;