add headers init via checkpoints.json

lib/blockchain.py

@@ -310,7 +310,10 @@ class Blockchain(util.PrintError):
         elif height < len_checkpoints * CHUNK_LEN - POW_AVERAGING_WINDOW:
             assert (height+1) % CHUNK_LEN == 0, height
             index = height // CHUNK_LEN
-            h, t = self.checkpoints[index]
+            if index < len_checkpoints - 1:
+                h, t = self.checkpoints[index]
+            else:
+                h, t, extra_headers = self.checkpoints[index]
             return h
         else:
             return hash_header(self.read_header(height))

lib/constants.py

@@ -46,7 +46,7 @@ class BitcoinMainnet:
     GENESIS = "00040fe8ec8471911baa1db1266ea15dd06b4a8a5c453883c000b031973dce08"
     DEFAULT_PORTS = {'t': '50021', 's': '50022'}
     DEFAULT_SERVERS = read_json('servers.json', {})
-    CHECKPOINTS = []
+    CHECKPOINTS = read_json('checkpoints.json', [])
 
     XPRV_HEADERS = {
         'standard':    0x0488ade4,  # xprv
@@ -67,7 +67,7 @@ class BitcoinTestnet:
     GENESIS = "05a60a92d99d85997cce3b87616c089f6124d7342af37106edc76126334a2c38"
     DEFAULT_PORTS = {'t': '51021', 's': '51022'}
     DEFAULT_SERVERS = read_json('servers_testnet.json', {})
-    CHECKPOINTS = []
+    CHECKPOINTS = read_json('checkpoints_testnet.json', [])
 
     XPRV_HEADERS = {
         'standard':    0x04358394,  # tprv

lib/network.py

@@ -987,9 +987,11 @@ class Network(util.DaemonThread):
         length = HDR_LEN * len(constants.net.CHECKPOINTS) * CHUNK_LEN
         if not os.path.exists(filename) or os.path.getsize(filename) < length:
             with open(filename, 'wb') as f:
-                if length>0:
-                    f.seek(length-1)
-                    f.write(b'\x00')
+                if length > 0:
+                    for height, hd in b.checkpoints[-1][2]:
+                        f.seek(height*80)
+                        bd = bfh(hd)
+                        f.write(bd)
         with b.lock:
             b.update_size()