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node_modules/mongodb/lib/gridfs-stream/download.js

@@ -0,0 +1,415 @@
+'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);
+}