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module.exports = FileStream
var debug = require('debug')('webtorrent:file-stream')
var inherits = require('inherits')
var stream = require('readable-stream')
inherits(FileStream, stream.Readable)
/**
* Readable stream of a torrent file
*
* @param {File} file
* @param {Object} opts
* @param {number} opts.start stream slice of file, starting from this byte (inclusive)
* @param {number} opts.end stream slice of file, ending with this byte (inclusive)
*/
function FileStream (file, opts) {
stream.Readable.call(this, opts)
this.destroyed = false
this._torrent = file._torrent
var start = (opts && opts.start) || 0
var end = (opts && opts.end && opts.end < file.length)
? opts.end
: file.length - 1
var pieceLength = file._torrent.pieceLength
this._startPiece = (start + file.offset) / pieceLength | 0
this._endPiece = (end + file.offset) / pieceLength | 0
this._piece = this._startPiece
this._offset = (start + file.offset) - (this._startPiece * pieceLength)
this._missing = end - start + 1
this._reading = false
this._notifying = false
this._criticalLength = Math.min((1024 * 1024 / pieceLength) | 0, 2)
}
FileStream.prototype._read = function () {
if (this._reading) return
this._reading = true
this._notify()
}
FileStream.prototype._notify = function () {
var self = this
if (!self._reading || self._missing === 0) return
if (!self._torrent.bitfield.get(self._piece)) {
return self._torrent.critical(self._piece, self._piece + self._criticalLength)
}
if (self._notifying) return
self._notifying = true
var p = self._piece
self._torrent.store.get(p, function (err, buffer) {
self._notifying = false
if (self.destroyed) return
if (err) return self._destroy(err)
debug('read %s (length %s) (err %s)', p, buffer.length, err && err.message)
if (self._offset) {
buffer = buffer.slice(self._offset)
self._offset = 0
}
if (self._missing < buffer.length) {
buffer = buffer.slice(0, self._missing)
}
self._missing -= buffer.length
debug('pushing buffer of length %s', buffer.length)
self._reading = false
self.push(buffer)
if (self._missing === 0) self.push(null)
})
self._piece += 1
}
FileStream.prototype.destroy = function (onclose) {
this._destroy(null, onclose)
}
FileStream.prototype._destroy = function (err, onclose) {
if (this.destroyed) return
this.destroyed = true
if (!this._torrent.destroyed) {
this._torrent.deselect(this._startPiece, this._endPiece, true)
}
if (err) this.emit('error', err)
this.emit('close')
if (onclose) onclose()
}
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