Implements BEP53 to allow file selection using &so in magnetURIs (#1396)

* Implements BEP53 to allow file selection using &so in magnetURI.

1 files changed, 15 insertions, 5 deletions

diff --git a/lib/torrent.js b/lib/torrent.js
index c0e8aaf..6d53ee9 100644
--- a/lib/torrent.js
+++ b/lib/torrent.js
@@ -30,6 +30,7 @@ var speedometer = require('speedometer')
 var uniq = require('uniq')
 var utMetadata = require('ut_metadata')
 var utPex = require('ut_pex') // browser exclude
+var parseRange = require('parse-numeric-range')
 
 var File = require('./file')
 var Peer = require('./peer')
@@ -482,11 +483,6 @@ Torrent.prototype._onMetadata = function (metadata) {
     })
   }
 
-  // start off selecting the entire torrent with low priority
-  if (self.pieces.length !== 0) {
-    self.select(0, self.pieces.length - 1, false)
-  }
-
   self._rarityMap = new RarityMap(self)
 
   self.store = new ImmediateChunkStore(
@@ -509,6 +505,20 @@ Torrent.prototype._onMetadata = function (metadata) {
     return new File(self, file)
   })
 
+  // Select only specified files (BEP53) http://www.bittorrent.org/beps/bep_0053.html
+  if (self.so) {
+    var selectOnlyFiles = parseRange.parse(self.so)
+
+    self.files.forEach(function (v, i) {
+      if (selectOnlyFiles.includes(i)) self.files[i].select(true)
+    })
+  } else {
+    // start off selecting the entire torrent with low priority
+    if (self.pieces.length !== 0) {
+      self.select(0, self.pieces.length - 1, false)
+    }
+  }
+
   self._hashes = self.pieces
 
   self.pieces = self.pieces.map(function (hash, i) {