add genesis block for mainnet/testnet and some parsing tests to make sure it looks good

Author: karpathy

cryptos/block.py

@@ -11,6 +11,12 @@
 
 from .sha256 import sha256
 
+# -----------------------------------------------------------------------------
+# Block headers, 80 bytes
+GENESIS_BLOCK = {
+    'main': bytes.fromhex('0100000000000000000000000000000000000000000000000000000000000000000000003ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4a29ab5f49ffff001d1dac2b7c'),
+    'test': bytes.fromhex('0100000000000000000000000000000000000000000000000000000000000000000000003ba3edfd7a7b12b27ac72c3e67768f617fc81bc3888a51323a9fb8aa4b1e5e4adae5494dffff001d1aa4ae18'),
+}
 # -----------------------------------------------------------------------------
 # helper functions
 

tests/test_block.py

@@ -5,6 +5,7 @@
 from io import BytesIO
 
 from cryptos.block import Block, calculate_new_bits, bits_to_target, target_to_bits
+from cryptos.block import GENESIS_BLOCK
 
 def test_block():
 
@@ -47,3 +48,25 @@ def test_calculate_bits():
         target = bits_to_target(bits)
         bits2 = target_to_bits(target)
         assert bits == bits2
+
+def test_genesis_block():
+    """
+    Validate the Bitcoin mainnet genesis block header
+    Reference: https://en.bitcoin.it/wiki/Genesis_block
+    Original code: https://sourceforge.net/p/bitcoin/code/133/tree/trunk/main.cpp#l1613
+    """
+    block_bytes = GENESIS_BLOCK['main']
+    assert len(block_bytes) == 80
+    block = Block.decode(BytesIO(block_bytes))
+
+    assert block.version == 1
+    assert block.prev_block == b'\x00'*32 # ;)
+    assert block.merkle_root.hex() == '4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b'
+    assert block.timestamp == 1231006505
+    assert block.bits[::-1].hex() == '1d00ffff'
+    assert int.from_bytes(block.nonce, 'little') == 2083236893
+
+    # validate proof of work. by two extra zeros, too!
+    assert block.id()                     == '000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f'
+    assert format(block.target(), '064x') == '00000000ffff0000000000000000000000000000000000000000000000000000'
+    assert block.validate()