Fixed homestead diff adjustment change

Author: vub

ethereum/blocks.py

@@ -39,10 +39,10 @@
 def calc_difficulty(parent, timestamp):
     config = parent.config
     offset = parent.difficulty // config['BLOCK_DIFF_FACTOR']
-    if parent.number < config['HOMESTEAD_FORK_BLKNUM']:
-        sign = 1 if timestamp - parent.timestamp < config['DIFF_ADJUSTMENT_CUTOFF'] else -1
-    else:
+    if parent.number >= (config['HOMESTEAD_FORK_BLKNUM'] - 1):
         sign = max(1 - 2 * ((timestamp - parent.timestamp) // config['HOMESTEAD_DIFF_ADJUSTMENT_CUTOFF']), -99)
+    else:
+        sign = 1 if timestamp - parent.timestamp < config['DIFF_ADJUSTMENT_CUTOFF'] else -1
     # If we enter a special mode where the genesis difficulty starts off below
     # the minimal difficulty, we allow low-difficulty blocks (this will never
     # happen in the official protocol)