[PATCH 05/12] index: NewIndex(): don't use separate read-lock to check if index is present

[Simon Ruderich]

The new index is random making collisions very unlikely, therefore
taking a separate read-only lock before taking the full lock in most
cases anyway will not improve performance and only makes the code more
complicated. However I didn't benchmark this change.
---
 src/index.go | 12 +++---------
 1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/src/index.go b/src/index.go
index 13e8693..bf8f0a0 100644
--- a/src/index.go
+++ b/src/index.go
@@ -63,21 +63,15 @@ func (table *IndexTable) NewIndex(peer *Peer) (uint32, error) {
 
 		// check if index used
 
-		table.mutex.RLock()
-		_, ok := table.table[index]
-		table.mutex.RUnlock()
-		if ok {
-			continue
-		}
-
-		// map index to handshake
-
 		table.mutex.Lock()
 		_, found := table.table[index]
 		if found {
 			table.mutex.Unlock()
 			continue
 		}
+
+		// map index to handshake
+
 		table.table[index] = IndexTableEntry{
 			peer:      peer,
 			handshake: &peer.handshake,
-- 
2.15.1