'use strict';
var stream = require('stream'),
util = require('util');
module.exports = GridFSBucketReadStream;
/**
* A readable stream that enables you to read buffers from GridFS.
*
* Do not instantiate this class directly. Use `openDownloadStream()` instead.
*
* @class
* @param {Collection} chunks Handle for chunks collection
* @param {Collection} files Handle for files collection
* @param {Object} readPreference The read preference to use
* @param {Object} filter The query to use to find the file document
* @param {Object} [options] Optional settings.
* @param {Number} [options.sort] Optional sort for the file find query
* @param {Number} [options.skip] Optional skip for the file find query
* @param {Number} [options.start] Optional 0-based offset in bytes to start streaming from
* @param {Number} [options.end] Optional 0-based offset in bytes to stop streaming before
* @fires GridFSBucketReadStream#error
* @fires GridFSBucketReadStream#file
* @return {GridFSBucketReadStream} a GridFSBucketReadStream instance.
*/
function GridFSBucketReadStream(chunks, files, readPreference, filter, options) {
this.s = {
bytesRead: 0,
chunks: chunks,
cursor: null,
expected: 0,
files: files,
filter: filter,
init: false,
expectedEnd: 0,
file: null,
options: options,
readPreference: readPreference
};
stream.Readable.call(this);
}
util.inherits(GridFSBucketReadStream, stream.Readable);
/**
* An error occurred
*
* @event GridFSBucketReadStream#error
* @type {Error}
*/
/**
* Fires when the stream loaded the file document corresponding to the
* provided id.
*
* @event GridFSBucketReadStream#file
* @type {object}
*/
/**
* Emitted when a chunk of data is available to be consumed.
*
* @event GridFSBucketReadStream#data
* @type {object}
*/
/**
* Fired when the stream is exhausted (no more data events).
*
* @event GridFSBucketReadStream#end
* @type {object}
*/
/**
* Fired when the stream is exhausted and the underlying cursor is killed
*
* @event GridFSBucketReadStream#close
* @type {object}
*/
/**
* Reads from the cursor and pushes to the stream.
* @method
*/
GridFSBucketReadStream.prototype._read = function() {
var _this = this;
if (this.destroyed) {
return;
}
waitForFile(_this, function() {
doRead(_this);
});
};
/**
* Sets the 0-based offset in bytes to start streaming from. Throws
* an error if this stream has entered flowing mode
* (e.g. if you've already called `on('data')`)
* @method
* @param {Number} start Offset in bytes to start reading at
* @return {GridFSBucketReadStream}
*/
GridFSBucketReadStream.prototype.start = function(start) {
throwIfInitialized(this);
this.s.options.start = start;
return this;
};
/**
* Sets the 0-based offset in bytes to start streaming from. Throws
* an error if this stream has entered flowing mode
* (e.g. if you've already called `on('data')`)
* @method
* @param {Number} end Offset in bytes to stop reading at
* @return {GridFSBucketReadStream}
*/
GridFSBucketReadStream.prototype.end = function(end) {
throwIfInitialized(this);
this.s.options.end = end;
return this;
};
/**
* Marks this stream as aborted (will never push another `data` event)
* and kills the underlying cursor. Will emit the 'end' event, and then
* the 'close' event once the cursor is successfully killed.
*
* @method
* @param {GridFSBucket~errorCallback} [callback] called when the cursor is successfully closed or an error occurred.
* @fires GridFSBucketWriteStream#close
* @fires GridFSBucketWriteStream#end
*/
GridFSBucketReadStream.prototype.abort = function(callback) {
var _this = this;
this.push(null);
this.destroyed = true;
if (this.s.cursor) {
this.s.cursor.close(function(error) {
_this.emit('close');
callback && callback(error);
});
} else {
if (!this.s.init) {
// If not initialized, fire close event because we will never
// get a cursor
_this.emit('close');
}
callback && callback();
}
};
/**
* @ignore
*/
function throwIfInitialized(self) {
if (self.s.init) {
throw new Error('You cannot change options after the stream has entered' + 'flowing mode!');
}
}
/**
* @ignore
*/
function doRead(_this) {
if (_this.destroyed) {
return;
}
_this.s.cursor.next(function(error, doc) {
if (_this.destroyed) {
return;
}
if (error) {
return __handleError(_this, error);
}
if (!doc) {
_this.push(null);
return _this.s.cursor.close(function(error) {
if (error) {
return __handleError(_this, error);
}
_this.emit('close');
});
}
var bytesRemaining = _this.s.file.length - _this.s.bytesRead;
var expectedN = _this.s.expected++;
var expectedLength = Math.min(_this.s.file.chunkSize, bytesRemaining);
if (doc.n> expectedN) {
var errmsg = 'ChunkIsMissing: Got unexpected n: ' + doc.n + ', expected: ' + expectedN;
return __handleError(_this, new Error(errmsg));
}
if (doc.n < expectedN) {
errmsg = 'ExtraChunk: Got unexpected n: ' + doc.n + ', expected: ' + expectedN;
return __handleError(_this, new Error(errmsg));
}
var buf = Buffer.isBuffer(doc.data) ? doc.data : doc.data.buffer;
if (buf.length !== expectedLength) {
if (bytesRemaining <= 0) {
errmsg = 'ExtraChunk: Got unexpected n: ' + doc.n;
return __handleError(_this, new Error(errmsg));
}
errmsg =
'ChunkIsWrongSize: Got unexpected length: ' + buf.length + ', expected: ' + expectedLength;
return __handleError(_this, new Error(errmsg));
}
_this.s.bytesRead += buf.length;
if (buf.length === 0) {
return _this.push(null);
}
var sliceStart = null;
var sliceEnd = null;
if (_this.s.bytesToSkip != null) {
sliceStart = _this.s.bytesToSkip;
_this.s.bytesToSkip = 0;
}
if (expectedN === _this.s.expectedEnd && _this.s.bytesToTrim != null) {
sliceEnd = _this.s.bytesToTrim;
}
// If the remaining amount of data left is < chunkSize read the right amount of data
if (_this.s.options.end && _this.s.options.end - _this.s.bytesToSkip < buf.length) {
sliceEnd = _this.s.options.end - _this.s.bytesToSkip;
}
if (sliceStart != null || sliceEnd != null) {
buf = buf.slice(sliceStart || 0, sliceEnd || buf.length);
}
_this.push(buf);
});
}
/**
* @ignore
*/
function init(self) {
var findOneOptions = {};
if (self.s.readPreference) {
findOneOptions.readPreference = self.s.readPreference;
}
if (self.s.options && self.s.options.sort) {
findOneOptions.sort = self.s.options.sort;
}
if (self.s.options && self.s.options.skip) {
findOneOptions.skip = self.s.options.skip;
}
self.s.files.findOne(self.s.filter, findOneOptions, function(error, doc) {
if (error) {
return __handleError(self, error);
}
if (!doc) {
var identifier = self.s.filter._id ? self.s.filter._id.toString() : self.s.filter.filename;
var errmsg = 'FileNotFound: file ' + identifier + ' was not found';
var err = new Error(errmsg);
err.code = 'ENOENT';
return __handleError(self, err);
}
// If document is empty, kill the stream immediately and don't
// execute any reads
if (doc.length <= 0) {
self.push(null);
return;
}
if (self.destroyed) {
// If user destroys the stream before we have a cursor, wait
// until the query is done to say we're 'closed' because we can't
// cancel a query.
self.emit('close');
return;
}
self.s.bytesToSkip = handleStartOption(self, doc, self.s.options);
var filter = { files_id: doc._id };
// Currently (MongoDB 3.4.4) skip function does not support the index,
// it needs to retrieve all the documents first and then skip them. (CS-25811)
// As work around we use $gte on the "n" field.
if (self.s.options && self.s.options.start != null) {
var skip = Math.floor(self.s.options.start / doc.chunkSize);
if (skip> 0) {
filter['n'] = { $gte: skip };
}
}
self.s.cursor = self.s.chunks.find(filter).sort({ n: 1 });
if (self.s.readPreference) {
self.s.cursor.setReadPreference(self.s.readPreference);
}
self.s.expectedEnd = Math.ceil(doc.length / doc.chunkSize);
self.s.file = doc;
self.s.bytesToTrim = handleEndOption(self, doc, self.s.cursor, self.s.options);
self.emit('file', doc);
});
}
/**
* @ignore
*/
function waitForFile(_this, callback) {
if (_this.s.file) {
return callback();
}
if (!_this.s.init) {
init(_this);
_this.s.init = true;
}
_this.once('file', function() {
callback();
});
}
/**
* @ignore
*/
function handleStartOption(stream, doc, options) {
if (options && options.start != null) {
if (options.start> doc.length) {
throw new Error(
'Stream start (' +
options.start +
') must not be ' +
'more than the length of the file (' +
doc.length +
')'
);
}
if (options.start < 0) {
throw new Error('Stream start (' + options.start + ') must not be ' + 'negative');
}
if (options.end != null && options.end < options.start) {
throw new Error(
'Stream start (' +
options.start +
') must not be ' +
'greater than stream end (' +
options.end +
')'
);
}
stream.s.bytesRead = Math.floor(options.start / doc.chunkSize) * doc.chunkSize;
stream.s.expected = Math.floor(options.start / doc.chunkSize);
return options.start - stream.s.bytesRead;
}
}
/**
* @ignore
*/
function handleEndOption(stream, doc, cursor, options) {
if (options && options.end != null) {
if (options.end> doc.length) {
throw new Error(
'Stream end (' +
options.end +
') must not be ' +
'more than the length of the file (' +
doc.length +
')'
);
}
if (options.start < 0) {
throw new Error('Stream end (' + options.end + ') must not be ' + 'negative');
}
var start = options.start != null ? Math.floor(options.start / doc.chunkSize) : 0;
cursor.limit(Math.ceil(options.end / doc.chunkSize) - start);
stream.s.expectedEnd = Math.ceil(options.end / doc.chunkSize);
return Math.ceil(options.end / doc.chunkSize) * doc.chunkSize - options.end;
}
}
/**
* @ignore
*/
function __handleError(_this, error) {
_this.emit('error', error);
}