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node_modules/mongodb/lib/gridfs/chunk.js

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+'use strict';
+
+var Binary = require('mongodb-core').BSON.Binary,
+  ObjectID = require('mongodb-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:
+ *
+ *        <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;