Merge pull request #1579 from fanatid/blockchain

Small blockchain.py changes

lib/blockchain.py

@@ -28,7 +28,7 @@ class Blockchain(util.PrintError):
     def __init__(self, config, network):
         self.config = config
         self.network = network
-        self.headers_url = 'https://headers.electrum.org/blockchain_headers'
+        self.headers_url = "https://headers.electrum.org/blockchain_headers"
         self.local_height = 0
         self.set_local_height()
 
@@ -40,7 +40,7 @@ class Blockchain(util.PrintError):
         self.set_local_height()
         self.print_error("%d blocks" % self.local_height)
 
-    def verify_headers(self, header, prev_header, bits, target):
+    def verify_header(self, header, prev_header, bits, target):
         prev_hash = self.hash_header(prev_header)
         assert prev_hash == header.get('prev_block_hash'), "prev hash mismatch: %s vs %s" % (prev_hash, header.get('prev_block_hash'))
         assert bits == header.get('bits'), "bits mismatch: %s vs %s" % (bits, header.get('bits'))
@@ -53,21 +53,21 @@ class Blockchain(util.PrintError):
         for header in chain:
             height = header.get('block_height')
             bits, target = self.get_target(height / 2016, chain)
-            self.verify_headers(header, prev_header, bits, target)
+            self.verify_header(header, prev_header, bits, target)
             prev_header = header
 
     def verify_chunk(self, index, hexdata):
         data = hexdata.decode('hex')
         num = len(data) / 80
-        prev_header = None if index == 0 else self.read_header(index*2016-1)
+        prev_header = None
+        if index != 0:
+            prev_header = self.read_header(index*2016 - 1)
         bits, target = self.get_target(index)
         for i in range(num):
             raw_header = data[i*80:(i+1) * 80]
             header = self.deserialize_header(raw_header)
-            self.verify_headers(header, prev_header, bits, target)
+            self.verify_header(header, prev_header, bits, target)
             prev_header = header
-        self.save_chunk(index, data)
-        self.print_error("validated chunk %d" % index)
 
     def serialize_header(self, res):
         s = int_to_hex(res.get('version'), 4) \
@@ -90,7 +90,9 @@ class Blockchain(util.PrintError):
         return h
 
     def hash_header(self, header):
-        return "0"*64 if header is None else rev_hex(Hash(self.serialize_header(header).decode('hex')).encode('hex'))
+        if header is None:
+            return '0' * 64
+        return hash_encode(Hash(self.serialize_header(header).decode('hex')))
 
     def path(self):
         return os.path.join(self.config.path, 'blockchain_headers')
@@ -213,6 +215,8 @@ class Blockchain(util.PrintError):
     def connect_chunk(self, idx, chunk):
         try:
             self.verify_chunk(idx, chunk)
+            self.print_error("validated chunk %d" % index)
+            self.save_chunk(index, data)
             return idx + 1
         except BaseException as e:
             self.print_error('verify_chunk failed', str(e))