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Kasper Rynning-Tønnesen
310
server/node_modules/mongodb/lib/gridfs-stream/download.js
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310
server/node_modules/mongodb/lib/gridfs-stream/download.js
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var shallowClone = require('../utils').shallowClone;
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var stream = require('stream');
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var util = require('util');
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module.exports = GridFSBucketReadStream;
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/**
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* A readable stream that enables you to read buffers from GridFS.
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*
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* Do not instantiate this class directly. Use `openDownloadStream()` instead.
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*
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* @class
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* @param {Collection} chunks Handle for chunks collection
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* @param {Collection} files Handle for files collection
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* @param {Object} readPreference The read preference to use
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* @param {Object} filter The query to use to find the file document
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* @param {Object} [options=null] Optional settings.
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* @param {Number} [options.sort=null] Optional sort for the file find query
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* @param {Number} [options.skip=null] Optional skip for the file find query
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* @param {Number} [options.start=null] Optional 0-based offset in bytes to start streaming from
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* @param {Number} [options.end=null] Optional 0-based offset in bytes to stop streaming before
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* @fires GridFSBucketReadStream#error
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* @fires GridFSBucketReadStream#file
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* @return {GridFSBucketReadStream} a GridFSBucketReadStream instance.
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*/
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function GridFSBucketReadStream(chunks, files, readPreference, filter, options) {
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var _this = this;
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this.s = {
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bytesRead: 0,
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chunks: chunks,
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cursor: null,
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expected: 0,
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files: files,
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filter: filter,
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init: false,
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expectedEnd: 0,
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file: null,
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options: options,
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readPreference: readPreference
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};
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stream.Readable.call(this);
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}
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util.inherits(GridFSBucketReadStream, stream.Readable);
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/**
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* An error occurred
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*
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* @event GridFSBucketReadStream#error
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* @type {Error}
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*/
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/**
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* Fires when the stream loaded the file document corresponding to the
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* provided id.
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*
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* @event GridFSBucketReadStream#file
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* @type {object}
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*/
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/**
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* Reads from the cursor and pushes to the stream.
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* @method
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*/
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GridFSBucketReadStream.prototype._read = function() {
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var _this = this;
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waitForFile(_this, function() {
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doRead(_this);
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});
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};
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/**
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* Sets the 0-based offset in bytes to start streaming from. Throws
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* an error if this stream has entered flowing mode
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* (e.g. if you've already called `on('data')`)
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* @method
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* @param {Number} start Offset in bytes to start reading at
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* @return {GridFSBucketReadStream}
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*/
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GridFSBucketReadStream.prototype.start = function(start) {
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throwIfInitialized(this);
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this.s.options.start = start;
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return this;
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};
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/**
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* Sets the 0-based offset in bytes to start streaming from. Throws
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* an error if this stream has entered flowing mode
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* (e.g. if you've already called `on('data')`)
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* @method
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* @param {Number} end Offset in bytes to stop reading at
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* @return {GridFSBucketReadStream}
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*/
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GridFSBucketReadStream.prototype.end = function(end) {
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throwIfInitialized(this);
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this.s.options.end = end;
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return this;
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};
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/**
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* @ignore
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*/
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function throwIfInitialized(self) {
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if (self.s.init) {
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throw new Error('You cannot change options after the stream has entered' +
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'flowing mode!');
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}
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}
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/**
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* @ignore
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*/
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function doRead(_this) {
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_this.s.cursor.next(function(error, doc) {
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if (error) {
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return __handleError(_this, error);
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}
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if (!doc) {
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return _this.push(null);
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}
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var bytesRemaining = _this.s.file.length - _this.s.bytesRead;
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var expectedN = _this.s.expected++;
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var expectedLength = Math.min(_this.s.file.chunkSize,
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bytesRemaining);
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if (doc.n > expectedN) {
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var errmsg = 'ChunkIsMissing: Got unexpected n: ' + doc.n +
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', expected: ' + expectedN;
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return __handleError(_this, new Error(errmsg));
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}
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if (doc.n < expectedN) {
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var errmsg = 'ExtraChunk: Got unexpected n: ' + doc.n +
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', expected: ' + expectedN;
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return __handleError(_this, new Error(errmsg));
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}
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if (doc.data.length() !== expectedLength) {
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if (bytesRemaining <= 0) {
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var errmsg = 'ExtraChunk: Got unexpected n: ' + doc.n;
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return __handleError(_this, new Error(errmsg));
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}
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var errmsg = 'ChunkIsWrongSize: Got unexpected length: ' +
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doc.data.length() + ', expected: ' + expectedLength;
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return __handleError(_this, new Error(errmsg));
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}
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_this.s.bytesRead += doc.data.length();
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if (doc.data.buffer.length === 0) {
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return _this.push(null);
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}
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var sliceStart = null;
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var sliceEnd = null;
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var buf = doc.data.buffer;
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if (_this.s.bytesToSkip != null) {
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sliceStart = _this.s.bytesToSkip;
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_this.s.bytesToSkip = 0;
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}
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if (expectedN === _this.s.expectedEnd && _this.s.bytesToTrim != null) {
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sliceEnd = _this.s.bytesToTrim;
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}
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if (sliceStart != null || sliceEnd != null) {
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buf = buf.slice(sliceStart || 0, sliceEnd || buf.length);
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}
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_this.push(buf);
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});
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};
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/**
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* @ignore
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*/
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function init(self) {
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var findOneOptions = {};
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if (self.s.readPreference) {
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findOneOptions.readPreference = self.s.readPreference;
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}
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if (self.s.options && self.s.options.sort) {
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findOneOptions.sort = self.s.options.sort;
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}
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if (self.s.options && self.s.options.skip) {
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findOneOptions.skip = self.s.options.skip;
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}
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self.s.files.findOne(self.s.filter, findOneOptions, function(error, doc) {
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if (error) {
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return __handleError(self, error);
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}
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if (!doc) {
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var identifier = self.s.filter._id ?
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self.s.filter._id.toString() : self.s.filter.filename;
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var errmsg = 'FileNotFound: file ' + identifier + ' was not found';
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return __handleError(self, new Error(errmsg));
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}
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// If document is empty, kill the stream immediately and don't
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// execute any reads
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if (doc.length <= 0) {
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self.push(null);
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return;
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}
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self.s.cursor = self.s.chunks.find({ files_id: doc._id }).sort({ n: 1 });
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if (self.s.readPreference) {
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self.s.cursor.setReadPreference(self.s.readPreference);
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}
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self.s.expectedEnd = Math.ceil(doc.length / doc.chunkSize);
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self.s.file = doc;
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self.s.bytesToSkip = handleStartOption(self, doc, self.s.cursor,
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self.s.options);
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self.s.bytesToTrim = handleEndOption(self, doc, self.s.cursor,
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self.s.options);
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self.emit('file', doc);
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});
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}
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/**
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* @ignore
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*/
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function waitForFile(_this, callback) {
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if (_this.s.file) {
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return callback();
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}
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if (!_this.s.init) {
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init(_this);
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_this.s.init = true;
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}
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_this.once('file', function() {
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callback();
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});
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};
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/**
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* @ignore
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*/
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function handleStartOption(stream, doc, cursor, options) {
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if (options && options.start != null) {
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if (options.start > doc.length) {
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throw new Error('Stream start (' + options.start + ') must not be ' +
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'more than the length of the file (' + doc.length +')')
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}
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if (options.start < 0) {
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throw new Error('Stream start (' + options.start + ') must not be ' +
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'negative');
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}
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if (options.end != null && options.end < options.start) {
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throw new Error('Stream start (' + options.start + ') must not be ' +
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'greater than stream end (' + options.end + ')');
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}
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cursor.skip(Math.floor(options.start / doc.chunkSize));
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stream.s.bytesRead = Math.floor(options.start / doc.chunkSize) *
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doc.chunkSize;
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stream.s.expected = Math.floor(options.start / doc.chunkSize);
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return options.start - stream.s.bytesRead;
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}
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}
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/**
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* @ignore
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*/
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function handleEndOption(stream, doc, cursor, options) {
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if (options && options.end != null) {
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if (options.end > doc.length) {
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throw new Error('Stream end (' + options.end + ') must not be ' +
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'more than the length of the file (' + doc.length +')')
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}
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if (options.start < 0) {
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throw new Error('Stream end (' + options.end + ') must not be ' +
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'negative');
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}
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var start = options.start != null ?
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Math.floor(options.start / doc.chunkSize) :
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0;
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cursor.limit(Math.ceil(options.end / doc.chunkSize) - start);
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stream.s.expectedEnd = Math.ceil(options.end / doc.chunkSize);
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return (Math.ceil(options.end / doc.chunkSize) * doc.chunkSize) -
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options.end;
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}
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}
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/**
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* @ignore
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*/
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function __handleError(_this, error) {
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_this.emit('error', error);
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}
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