Refactor block parsing API

lib/coins.py

@@ -30,6 +30,7 @@ Anything coin-specific should go in this file and be subclassed where
 necessary for appropriate handling.
 '''
 
+from collections import namedtuple
 import re
 import struct
 from decimal import Decimal
@@ -40,6 +41,8 @@ from lib.hash import Base58, hash160, double_sha256, hash_to_str
 from lib.script import ScriptPubKey
 from lib.tx import Deserializer, DeserializerSegWit
 
+Block = namedtuple("Block", "header transactions")
+
 
 class CoinError(Exception):
     '''Exception raised for coin-related errors.'''
@@ -53,6 +56,8 @@ class Coin(object):
     RPC_URL_REGEX = re.compile('.+@(\[[0-9a-fA-F:]+\]|[^:]+)(:[0-9]+)?')
     VALUE_PER_COIN = 100000000
     CHUNK_SIZE = 2016
+    BASIC_HEADER_SIZE = 80
+    STATIC_BLOCK_HEADERS = True
     IRC_PREFIX = None
     IRC_SERVER = "irc.freenode.net"
     IRC_PORT = 6667
@@ -232,29 +237,33 @@ class Coin(object):
         return header[4:36]
 
     @classmethod
-    def header_offset(cls, height):
+    def static_header_offset(cls, height):
         '''Given a header height return its offset in the headers file.
 
         If header sizes change at some point, this is the only code
         that needs updating.'''
-        return height * 80
+        assert cls.STATIC_BLOCK_HEADERS
+        return height * cls.BASIC_HEADER_SIZE
 
     @classmethod
-    def header_len(cls, height):
+    def static_header_len(cls, height):
         '''Given a header height return its length.'''
-        return cls.header_offset(height + 1) - cls.header_offset(height)
+        return cls.static_header_offset(height + 1) \
+               - cls.static_header_offset(height)
 
     @classmethod
     def block_header(cls, block, height):
         '''Returns the block header given a block and its height.'''
-        return block[:cls.header_len(height)]
+        return block[:cls.static_header_len(height)]
 
     @classmethod
-    def block_txs(cls, block, height):
-        '''Returns a list of (deserialized_tx, tx_hash) pairs given a
+    def block_full(cls, block, height):
+        '''Returns (header, [(deserialized_tx, tx_hash), ...]) given a
         block and its height.'''
+        header = cls.block_header(block, height)
         deserializer = cls.deserializer()
-        return deserializer(block[cls.header_len(height):]).read_block()
+        txs = deserializer(block[len(header):]).read_tx_block()
+        return Block(header, txs)
 
     @classmethod
     def decimal_value(cls, value):
@@ -635,8 +644,9 @@ class FairCoin(Coin):
     P2PKH_VERBYTE = bytes.fromhex("5f")
     P2SH_VERBYTE = bytes.fromhex("24")
     WIF_BYTE = bytes.fromhex("df")
-    GENESIS_HASH=('1f701f2b8de1339dc0ec908f3fb6e9b0'
-                  'b870b6f20ba893e120427e42bbc048d7')
+    GENESIS_HASH = ('1f701f2b8de1339dc0ec908f3fb6e9b0'
+                    'b870b6f20ba893e120427e42bbc048d7')
+    BASIC_HEADER_SIZE = 108
     TX_COUNT = 1000
     TX_COUNT_HEIGHT = 1000
     TX_PER_BLOCK = 1
@@ -650,22 +660,14 @@ class FairCoin(Coin):
     ]
 
     @classmethod
-    def header_offset(cls, height):
-        '''Given a header height return its offset in the headers file.
-        If header sizes change at some point, this is the only code
-        that needs updating.'''
-        return height * 108
-
-    @classmethod
-    def block_txs(cls, block, height):
-        '''Returns a list of (deserialized_tx, tx_hash) pairs given a
+    def block_full(cls, block, height):
+        '''Returns (header, [(deserialized_tx, tx_hash), ...]) given a
         block and its height.'''
 
-        if height == 0:
-            return []
-
-        deserializer = cls.deserializer()
-        return deserializer(block[cls.header_len(height):]).read_block()
+        if height > 0:
+            return cls.block_full(block, height)
+        else:
+            return Block(cls.block_header(block, height), [])
 
     @classmethod
     def electrum_header(cls, header, height):

lib/tx.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2016-2017, Neil Booth
+# Copyright (c) 2017, the ElectrumX authors
 #
 # All rights reserved.
 #
@@ -105,10 +106,10 @@ class Deserializer(object):
             self._read_le_uint32()  # locktime
         ), double_sha256(self.binary[start:self.cursor])
 
-    def read_block(self):
+    def read_tx_block(self):
         '''Returns a list of (deserialized_tx, tx_hash) pairs.'''
         read_tx = self.read_tx
-        txs = [read_tx() for n in range(self._read_varint())]
+        txs = [read_tx() for _ in range(self._read_varint())]
         # Some coins have excess data beyond the end of the transactions
         return txs
 

server/block_processor.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2016-2017, Neil Booth
+# Copyright (c) 2017, the ElectrumX authors
 #
 # All rights reserved.
 #
@@ -231,15 +232,15 @@ class BlockProcessor(server.db.DB):
                                 .format(len(blocks), first, self.height + 1))
             return
 
-        headers = [self.coin.block_header(block, first + n)
-                   for n, block in enumerate(blocks)]
+        blocks = [self.coin.block_full(block, first + n)
+                         for n, block in enumerate(blocks)]
+        headers = [b.header for b in blocks]
         hprevs = [self.coin.header_prevhash(h) for h in headers]
         chain = [self.tip] + [self.coin.header_hash(h) for h in headers[:-1]]
 
         if hprevs == chain:
             start = time.time()
-            await self.controller.run_in_executor(self.advance_blocks,
-                                                  blocks, headers)
+            await self.controller.run_in_executor(self.advance_blocks, blocks)
             if not self.first_sync:
                 s = '' if len(blocks) == 1 else 's'
                 self.logger.info('processed {:,d} block{} in {:.1f}s'
@@ -479,18 +480,18 @@ class BlockProcessor(server.db.DB):
         if utxo_MB + hist_MB >= self.cache_MB or hist_MB >= self.cache_MB // 5:
             self.flush(utxo_MB >= self.cache_MB * 4 // 5)
 
-    def advance_blocks(self, blocks, headers):
+    def advance_blocks(self, blocks):
         '''Synchronously advance the blocks.
 
         It is already verified they correctly connect onto our tip.
         '''
-        block_txs = self.coin.block_txs
+        headers = [block.header for block in blocks]
         min_height = self.min_undo_height(self.daemon.cached_height())
         height = self.height
 
         for block in blocks:
             height += 1
-            undo_info = self.advance_txs(block_txs(block, height))
+            undo_info = self.advance_txs(block.transactions)
             if height >= min_height:
                 self.undo_infos.append((undo_info, height))
 
@@ -568,14 +569,14 @@ class BlockProcessor(server.db.DB):
         coin = self.coin
         for block in blocks:
             # Check and update self.tip
-            header = coin.block_header(block, self.height)
+            header, txs = coin.block_full(block, self.height)
             header_hash = coin.header_hash(header)
             if header_hash != self.tip:
                 raise ChainError('backup block {} not tip {} at height {:,d}'
                                  .format(hash_to_str(header_hash),
                                          hash_to_str(self.tip), self.height))
             self.tip = coin.header_prevhash(header)
-            self.backup_txs(coin.block_txs(block, self.height))
+            self.backup_txs(txs)
             self.height -= 1
             self.tx_counts.pop()
 

server/db.py

@@ -1,4 +1,5 @@
 # Copyright (c) 2016, Neil Booth
+# Copyright (c) 2017, the ElectrumX authors
 #
 # All rights reserved.
 #
@@ -44,6 +45,13 @@ class DB(util.LoggedClass):
         self.env = env
         self.coin = env.coin
 
+        # Setup block header size handlers
+        if self.coin.STATIC_BLOCK_HEADERS:
+            self.header_offset = self.coin.static_header_offset
+            self.header_len = self.coin.static_header_len
+        else:
+            raise Exception("Non static headers are not supported")
+
         self.logger.info('switching current directory to {}'
                          .format(env.db_dir))
         os.chdir(env.db_dir)
@@ -191,24 +199,25 @@ class DB(util.LoggedClass):
         updated.  These arrays are all append only, so in a crash we
         just pick up again from the DB height.
         '''
-        blocks_done = len(self.headers)
+        blocks_done = len(headers)
+        height_start = fs_height + 1
         new_height = fs_height + blocks_done
         prior_tx_count = (self.tx_counts[fs_height] if fs_height >= 0 else 0)
         cur_tx_count = self.tx_counts[-1] if self.tx_counts else 0
         txs_done = cur_tx_count - prior_tx_count
 
-        assert len(self.tx_hashes) == blocks_done
+        assert len(block_tx_hashes) == blocks_done
         assert len(self.tx_counts) == new_height + 1
         hashes = b''.join(block_tx_hashes)
         assert len(hashes) % 32 == 0
         assert len(hashes) // 32 == txs_done
 
         # Write the headers, tx counts, and tx hashes
-        offset = self.coin.header_offset(fs_height + 1)
+        offset = self.header_offset(height_start)
         self.headers_file.write(offset, b''.join(headers))
-        offset = (fs_height + 1) * self.tx_counts.itemsize
+        offset = height_start * self.tx_counts.itemsize
         self.tx_counts_file.write(offset,
-                                  self.tx_counts[fs_height + 1:].tobytes())
+                                  self.tx_counts[height_start:].tobytes())
         offset = prior_tx_count * 32
         self.hashes_file.write(offset, hashes)
 
@@ -220,8 +229,8 @@ class DB(util.LoggedClass):
             raise self.DBError('{:,d} headers starting at {:,d} not on disk'
                                .format(count, start))
         if disk_count:
-            offset = self.coin.header_offset(start)
-            size = self.coin.header_offset(start + disk_count) - offset
+            offset = self.header_offset(start)
+            size = self.header_offset(start + disk_count) - offset
             return self.headers_file.read(offset, size)
         return b''
 
@@ -241,7 +250,7 @@ class DB(util.LoggedClass):
         offset = 0
         headers = []
         for n in range(count):
-            hlen = self.coin.header_len(height + n)
+            hlen = self.header_len(height + n)
             headers.append(headers_concat[offset:offset + hlen])
             offset += hlen