Changeset 10851 for dotorg/trunk

Timestamp:

02/15/2008 03:04:41 PM (9 months ago)

Author:

dave

Message:

Fix in example python that causes incorrect results when returned peer
list wraps end of tracker peer list.

Location:

dotorg/trunk/html/beps

Files:

• bep_0008.py (modified) (1 diff)
• bep_0008.rst (modified) (1 diff)

dotorg/trunk/html/beps/bep_0008.py

@@ -54 +54 @@
   response['iv'] = iv
   numwant = min(numwant, MAX_PEERS)
-  if numwant > num_peers:
+  if numwant >= num_peers:
     response['peers'] = obfuscated_tracker_peer_list
     return response
 
-  i = randint(0,num_peers)
+  i = randint(0,num_peers-numwant) 
   response['i'] = xor(i,x) 
   response['n'] = n_xor_y
-  response['peers'] = obfuscated_tracker_peer_list[i*6:(i+numwant)*6]
-  
-  if len(response['peers']) < numwant * 6:
-    r = numwant - len(response['peers']) / 6
-    response['peers'] = response['peers'] + obfuscated_tracker_peer_list[:r] 
+  # peers at end of tracker peer list have lower probability of being picked,
+  # but this requires only one copy.
+  response['peers'] = obfuscated_tracker_peer_list[i*6:(i+numwant)*6]  
   return response 
 

dotorg/trunk/html/beps/bep_0008.rst

@@ -432 +432 @@
     response['iv'] = iv
     numwant = min(numwant, MAX_PEERS)
-    if numwant > num_peers:
+    if numwant >= num_peers:
       response['peers'] = obfuscated_tracker_peer_list
       return response
-    i = randint(0,num_peers)
-    response['i'] = xor(i,x) 
+  
+    i = randint(0,num_peers-numwant)
+    response['i'] = xor(i,x)
     response['n'] = n_xor_y
+    # peers at end of tracker peer list have lower probability of being picked,
+    # but this requires only one copy.
     response['peers'] = obfuscated_tracker_peer_list[i*6:(i+numwant)*6]
-    if len(response['peers']) < numwant * 6:
-      r = numwant - len(response['peers']) / 6
-      response['peers'] = response['peers'] + obfuscated_tracker_peer_list[:r] 
-    return response 
+    return response
   
   init()