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module.exports = WebConn
var BitField = require('bitfield')
var Buffer = require('safe-buffer').Buffer
var debug = require('debug')('webtorrent:webconn')
var get = require('simple-get')
var inherits = require('inherits')
var sha1 = require('simple-sha1')
var Wire = require('bittorrent-protocol')
var VERSION = require('../package.json').version
inherits(WebConn, Wire)
/**
* Converts requests for torrent blocks into http range requests.
* @param {string} url web seed url
* @param {Object} torrent
*/
function WebConn (url, torrent) {
Wire.call(this)
this.url = url
this.webPeerId = sha1.sync(url)
this._torrent = torrent
this._init()
}
WebConn.prototype._init = function () {
var self = this
self.setKeepAlive(true)
self.once('handshake', function (infoHash, peerId) {
if (self.destroyed) return
self.handshake(infoHash, self.webPeerId)
var numPieces = self._torrent.pieces.length
var bitfield = new BitField(numPieces)
for (var i = 0; i <= numPieces; i++) {
bitfield.set(i, true)
}
self.bitfield(bitfield)
})
self.once('interested', function () {
debug('interested')
self.unchoke()
})
self.on('uninterested', function () { debug('uninterested') })
self.on('choke', function () { debug('choke') })
self.on('unchoke', function () { debug('unchoke') })
self.on('bitfield', function () { debug('bitfield') })
self.on('request', function (pieceIndex, offset, length, callback) {
debug('request pieceIndex=%d offset=%d length=%d', pieceIndex, offset, length)
self.httpRequest(pieceIndex, offset, length, callback)
})
}
WebConn.prototype.httpRequest = function (pieceIndex, offset, length, cb) {
var self = this
var pieceOffset = pieceIndex * self._torrent.pieceLength
var rangeStart = pieceOffset + offset /* offset within whole torrent */
var rangeEnd = rangeStart + length - 1
// Web seed URL format:
// For single-file torrents, make HTTP range requests directly to the web seed URL
// For multi-file torrents, add the torrent folder and file name to the URL
var files = self._torrent.files
var requests
if (files.length <= 1) {
requests = [{
url: self.url,
start: rangeStart,
end: rangeEnd
}]
} else {
var requestedFiles = files.filter(function (file) {
return file.offset <= rangeEnd && (file.offset + file.length) > rangeStart
})
if (requestedFiles.length < 1) {
return cb(new Error('Could not find file corresponnding to web seed range request'))
}
requests = requestedFiles.map(function (requestedFile) {
var fileEnd = requestedFile.offset + requestedFile.length - 1
var url = self.url +
(self.url[self.url.length - 1] === '/' ? '' : '/') +
requestedFile.path
return {
url: url,
fileOffsetInRange: Math.max(requestedFile.offset - rangeStart, 0),
start: Math.max(rangeStart - requestedFile.offset, 0),
end: Math.min(fileEnd, rangeEnd - requestedFile.offset)
}
})
}
// Now make all the HTTP requests we need in order to load this piece
// Usually that's one requests, but sometimes it will be multiple
// Send requests in parallel and wait for them all to come back
var numRequestsSucceeded = 0
var hasError = false
var ret
if (requests.length > 1) {
ret = Buffer.alloc(length)
}
requests.forEach(function (request) {
var url = request.url
var start = request.start
var end = request.end
debug(
'Requesting url=%s pieceIndex=%d offset=%d length=%d start=%d end=%d',
url, pieceIndex, offset, length, start, end
)
var opts = {
url: url,
method: 'GET',
headers: {
'user-agent': 'WebTorrent/' + VERSION + ' (https://webtorrent.io)',
range: 'bytes=' + start + '-' + end
}
}
function onResponse (res, data) {
if (res.statusCode < 200 || res.statusCode >= 300) {
hasError = true
return cb(new Error('Unexpected HTTP status code ' + res.statusCode))
}
debug('Got data of length %d', data.length)
if (requests.length === 1) {
// Common case: fetch piece in a single HTTP request, return directly
cb(null, data)
} else {
// Rare case: reconstruct multiple HTTP requests across 2+ files into one
// piece buffer
data.copy(ret, request.fileOffsetInRange)
if (++numRequestsSucceeded === requests.length) {
cb(null, ret)
}
}
}
get.concat(opts, function (err, res, data) {
if (hasError) return
if (err) {
// Browsers allow HTTP redirects for simple cross-origin
// requests but not for requests that require preflight.
// Use a simple request to unravel any redirects and get the
// final URL. Retry the original request with the new URL if
// it's different.
//
// This test is imperfect but it's simple and good for common
// cases. It catches all cross-origin cases but matches a few
// same-origin cases too.
if (typeof window === 'undefined' || url.startsWith(window.location.origin + '/')) {
hasError = true
return cb(err)
}
return get.head(url, function (errHead, res) {
if (hasError) return
if (errHead) {
hasError = true
return cb(errHead)
}
if (res.statusCode < 200 || res.statusCode >= 300) {
hasError = true
return cb(new Error('Unexpected HTTP status code ' + res.statusCode))
}
if (res.url === url) {
hasError = true
return cb(err)
}
opts.url = res.url
get.concat(opts, function (err, res, data) {
if (hasError) return
if (err) {
hasError = true
return cb(err)
}
onResponse(res, data)
})
})
}
onResponse(res, data)
})
})
}
WebConn.prototype.destroy = function () {
Wire.prototype.destroy.call(this)
this._torrent = null
}
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