fix get_block, add has_blockhash to chain

Author: Jan Xie

ethereum/casper_utils.py

@@ -55,6 +55,7 @@ def get_finalizer_code():
 casper_config['HOMESTEAD_FORK_BLKNUM'] = 0
 casper_config['METROPOLIS_FORK_BLKNUM'] = 0
 casper_config['SERENITY_FORK_BLKNUM'] = 0
+# config['CASPER_ADDR'] == config['SERENITY_HEADER_VERIFIER']
 casper_config['CASPER_ADDR'] = utils.int_to_addr(255)
 casper_config['RLP_DECODER_ADDR'] = utils.int_to_addr(253)
 casper_config['HASH_WITHOUT_BLOOM_ADDR'] = utils.int_to_addr(252)

ethereum/chain.py

@@ -131,7 +131,11 @@ def get_parent(self, block):
 
     def get_block(self, blockhash):
         try:
-            return rlp.decode(self.db.get(blockhash), Block)
+            block_rlp = self.db.get(blockhash)
+            if block_rlp == 'GENESIS':
+                return self.genesis
+            else:
+                return rlp.decode(block_rlp, Block)
         except:
             return None
 
@@ -312,6 +316,9 @@ def __contains__(self, blk):
     def has_block(self, block):
         return block in self
 
+    def has_blockhash(self, blockhash):
+        return blockhash in self.db
+
     def get_chain(self, frm=None, to=2**63 - 1):
         if frm is None:
             frm = int(self.db.get('GENESIS_NUMBER')) + 1