Generate default peerExtensionBytes using helpers

client.go

@@ -278,7 +278,7 @@ func NewClient(cfg *Config) (cl *Client, err error) {
 	} else {
 		cl.downloadLimit = cfg.DownloadRateLimiter
 	}
-	missinggo.CopyExact(&cl.extensionBytes, defaultExtensionBytes)
+	cl.extensionBytes = defaultPeerExtensionBytes()
 	cl.event.L = &cl.mu
 	storageImpl := cfg.DefaultStorage
 	if storageImpl == nil {

global.go

@@ -10,25 +10,16 @@ const (
 	maxRequests      = 250    // Maximum pending requests we allow peers to send us.
 	defaultChunkSize = 0x4000 // 16KiB
 
-	// Justification for set bits follows.
-	//
-	// Extension protocol ([5]|=0x10):
-	// http://www.bittorrent.org/beps/bep_0010.html
-	//
-	// Fast Extension ([7]|=0x04):
-	// http://bittorrent.org/beps/bep_0006.html.
-	// Disabled until AllowedFast is implemented. TODO
-	//
-	// DHT ([7]|=1):
-	// http://www.bittorrent.org/beps/bep_0005.html
-	defaultExtensionBytes = "\x00\x00\x00\x00\x00\x10\x00\x01"
-
 	// These are our extended message IDs. Peers will use these values to
 	// select which extension a message is intended for.
 	metadataExtendedId = iota + 1 // 0 is reserved for deleting keys
 	pexExtendedId
 )
 
+func defaultPeerExtensionBytes() peerExtensionBytes {
+	return newPeerExtensionBytes(ExtensionBitDHT, ExtensionBitExtended)
+}
+
 // I could move a lot of these counters to their own file, but I suspect they
 // may be attached to a Client someday.
 var (

handshake.go

@@ -38,6 +38,13 @@ type (
 	peerExtensionBytes [8]byte
 )
 
+func newPeerExtensionBytes(bits ...ExtensionBit) (ret peerExtensionBytes) {
+	for _, b := range bits {
+		ret.SetBit(b)
+	}
+	return
+}
+
 func (pex peerExtensionBytes) SupportsExtended() bool {
 	return pex.GetBit(ExtensionBitExtended)
 }

handshake_test.go

@@ -9,7 +9,7 @@ import (
 
 func TestDefaultExtensionBytes(t *testing.T) {
 	var pex peerExtensionBytes
-	missinggo.CopyExact(&pex, defaultExtensionBytes)
+	missinggo.CopyExact(&pex, defaultPeerExtensionBytes())
 	assert.True(t, pex.SupportsDHT())
 	assert.True(t, pex.SupportsExtended())
 	assert.False(t, pex.SupportsFast())