Allow linearization scripts to support hash byte reversal

Currently, the linearization scripts require input hashes to be in one endian form. Add support for byte reversal.

Author: droark

contrib/linearize/README.md

@@ -1,33 +1,43 @@
 # Linearize
-Construct a linear, no-fork, best version of the blockchain.
+Construct a linear, no-fork, best version of the Bitcoin blockchain.
 
 ## Step 1: Download hash list
 
     $ ./linearize-hashes.py linearize.cfg > hashlist.txt
 
 Required configuration file settings for linearize-hashes:
-* RPC: rpcuser, rpcpassword
+* RPC: `rpcuser`, `rpcpassword`
 
 Optional config file setting for linearize-hashes:
-* RPC: host, port
-* Block chain: min_height, max_height
+* RPC: `host`, `port`  (Default: `127.0.0.1:8332`)
+* Blockchain: `min_height`, `max_height`
+* `rev_hash_bytes`: If true, the written block hash list will be
+byte-reversed. (In other words, the hash returned by getblockhash will have its
+bytes reversed.) False by default. Intended for generation of
+standalone hash lists but safe to use with linearize-data.py, which will output
+the same data no matter which byte format is chosen.
 
 ## Step 2: Copy local block data
 
     $ ./linearize-data.py linearize.cfg
 
 Required configuration file settings:
-* "input": bitcoind blocks/ directory containing blkNNNNN.dat
-* "hashlist": text file containing list of block hashes, linearized-hashes.py
-output.
-* "output_file": bootstrap.dat
+* `output_file`: The file that will contain the final blockchain.
       or
-* "output": output directory for linearized blocks/blkNNNNN.dat output
+* `output`: Output directory for linearized blocks/blkNNNNN.dat output.
 
 Optional config file setting for linearize-data:
-* "netmagic": network magic number
-* "max_out_sz": maximum output file size (default `1000*1000*1000`)
-* "split_timestamp": Split files when a new month is first seen, in addition to
-reaching a maximum file size.
-* "file_timestamp": Set each file's last-modified time to that of the
-most recent block in that file.
+* `file_timestamp`: Set each file's last-modified time to that of the most
+recent block in that file.
+* `genesis`: The hash of the genesis block in the blockchain.
+* `input: bitcoind blocks/ directory containing blkNNNNN.dat
+* `hashlist`: text file containing list of block hashes created by
+linearize-hashes.py.
+* `max_out_sz`: Maximum size for files created by the `output_file` option.
+(Default: `1000*1000*1000 bytes`)
+* `netmagic`: Network magic number.
+* `rev_hash_bytes`: If true, the block hash list written by linearize-hashes.py
+will be byte-reversed when read by linearize-data.py. See the linearize-hashes
+entry for more information.
+* `split_timestamp`: Split blockchain files when a new month is first seen, in
+addition to reaching a maximum file size (`max_out_sz`).

contrib/linearize/example-linearize.cfg

@@ -23,7 +23,9 @@ input=/home/example/.bitcoin/blocks
 
 output_file=/home/example/Downloads/bootstrap.dat
 hashlist=hashlist.txt
-split_year=1
 
 # Maxmimum size in bytes of out-of-order blocks cache in memory
 out_of_order_cache_sz = 100000000
+
+# Do we want the reverse the hash bytes coming from getblockhash?
+rev_hash_bytes = False

contrib/linearize/linearize-data.py

@@ -23,6 +23,12 @@
 
 settings = {}
 
+##### Switch endian-ness #####
+def hex_switchEndian(s):
+	""" Switches the endianness of a hex string (in pairs of hex chars) """
+	pairList = [s[i]+s[i+1] for i in range(0,len(s),2)]
+	return ''.join(pairList[::-1])
+
 def uint32(x):
 	return x & 0xffffffffL
 
@@ -69,17 +75,21 @@ def get_blk_dt(blk_hdr):
 	dt_ym = datetime.datetime(dt.year, dt.month, 1)
 	return (dt_ym, nTime)
 
+# When getting the list of block hashes, undo any byte reversals.
 def get_block_hashes(settings):
 	blkindex = []
 	f = open(settings['hashlist'], "r")
 	for line in f:
 		line = line.rstrip()
+		if settings['rev_hash_bytes'] == 'true':
+			line = hex_switchEndian(line)
 		blkindex.append(line)
 
 	print("Read " + str(len(blkindex)) + " hashes")
 
 	return blkindex
 
+# The block map shouldn't give or receive byte-reversed hashes.
 def mkblockmap(blkindex):
 	blkmap = {}
 	for height,hash in enumerate(blkindex):
@@ -265,6 +275,12 @@ def run(self):
 		settings[m.group(1)] = m.group(2)
 	f.close()
 
+	# Force hash byte format setting to be lowercase to make comparisons easier.
+	# Also place upfront in case any settings need to know about it.
+	if 'rev_hash_bytes' not in settings:
+		settings['rev_hash_bytes'] = 'false'
+	settings['rev_hash_bytes'] = settings['rev_hash_bytes'].lower()
+
 	if 'netmagic' not in settings:
 		settings['netmagic'] = 'f9beb4d9'
 	if 'genesis' not in settings:
@@ -295,9 +311,8 @@ def run(self):
 	blkindex = get_block_hashes(settings)
 	blkmap = mkblockmap(blkindex)
 
+	# Block hash map won't be byte-reversed. Neither should the genesis hash.
 	if not settings['genesis'] in blkmap:
 		print("Genesis block not found in hashlist")
 	else:
 		BlockDataCopier(settings, blkindex, blkmap).run()
-
-

contrib/linearize/linearize-hashes.py

@@ -17,6 +17,12 @@
 
 settings = {}
 
+##### Switch endian-ness #####
+def hex_switchEndian(s):
+	""" Switches the endianness of a hex string (in pairs of hex chars) """
+	pairList = [s[i]+s[i+1] for i in range(0,len(s),2)]
+	return ''.join(pairList[::-1])
+
 class BitcoinRPC:
 	def __init__(self, host, port, username, password):
 		authpair = "%s:%s" % (username, password)
@@ -70,6 +76,8 @@ def get_block_hashes(settings, max_blocks_per_call=10000):
 				print('JSON-RPC: error at height', height+x, ': ', resp_obj['error'], file=sys.stderr)
 				exit(1)
 			assert(resp_obj['id'] == x) # assume replies are in-sequence
+			if settings['rev_hash_bytes'] == 'true':
+				resp_obj['result'] = hex_switchEndian(resp_obj['result'])
 			print(resp_obj['result'])
 
 		height += num_blocks
@@ -101,6 +109,8 @@ def get_block_hashes(settings, max_blocks_per_call=10000):
 		settings['min_height'] = 0
 	if 'max_height' not in settings:
 		settings['max_height'] = 313000
+	if 'rev_hash_bytes' not in settings:
+		settings['rev_hash_bytes'] = 'false'
 	if 'rpcuser' not in settings or 'rpcpassword' not in settings:
 		print("Missing username and/or password in cfg file", file=stderr)
 		sys.exit(1)
@@ -109,5 +119,7 @@ def get_block_hashes(settings, max_blocks_per_call=10000):
 	settings['min_height'] = int(settings['min_height'])
 	settings['max_height'] = int(settings['max_height'])
 
-	get_block_hashes(settings)
+	# Force hash byte format setting to be lowercase to make comparisons easier.
+	settings['rev_hash_bytes'] = settings['rev_hash_bytes'].lower()
 
+	get_block_hashes(settings)