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"use strict";
var Binary = require('mongodb-core').BSON.Binary,
ObjectID = require('mongodb-core').BSON.ObjectID;
/**
* 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 = new Buffer(mongoObjectFinal.data.length);
buffer.write(mongoObjectFinal.data, 0, mongoObjectFinal.data.length, 'binary');
this.data = new Binary(buffer);
} else if(Array.isArray(mongoObjectFinal.data)) {
buffer = new Buffer(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 = new Buffer(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:
*
* <pre><code>
* {
* '_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
* }
* </code></pre>
*
* @see <a href="http://www.mongodb.org/display/DOCS/GridFS+Specification#GridFSSpecification-{{chunks}}">MongoDB GridFS Chunk Object Structure</a>
*/
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;
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