contrib: refactor: simplify block header string routine in linearize-data.py

The string representation of a block header hash is simply the
hexlified byte-reversed double SHA256 hash of its serialization.

Author: theStack

contrib/linearize/linearize-data.py

@@ -25,44 +25,9 @@ def hex_switchEndian(s):
     pairList = [s[i:i+2].encode() for i in range(0, len(s), 2)]
     return b''.join(pairList[::-1]).decode()
 
-def uint32(x):
-    return x & 0xffffffff
-
-def bytereverse(x):
-    return uint32(( ((x) << 24) | (((x) << 8) & 0x00ff0000) |
-               (((x) >> 8) & 0x0000ff00) | ((x) >> 24) ))
-
-def bufreverse(in_buf):
-    out_words = []
-    for i in range(0, len(in_buf), 4):
-        word = struct.unpack('@I', in_buf[i:i+4])[0]
-        out_words.append(struct.pack('@I', bytereverse(word)))
-    return b''.join(out_words)
-
-def wordreverse(in_buf):
-    out_words = []
-    for i in range(0, len(in_buf), 4):
-        out_words.append(in_buf[i:i+4])
-    out_words.reverse()
-    return b''.join(out_words)
-
-def calc_hdr_hash(blk_hdr):
-    hash1 = hashlib.sha256()
-    hash1.update(blk_hdr)
-    hash1_o = hash1.digest()
-
-    hash2 = hashlib.sha256()
-    hash2.update(hash1_o)
-    hash2_o = hash2.digest()
-
-    return hash2_o
-
 def calc_hash_str(blk_hdr):
-    hash = calc_hdr_hash(blk_hdr)
-    hash = bufreverse(hash)
-    hash = wordreverse(hash)
-    hash_str = hash.hex()
-    return hash_str
+    blk_hdr_hash = hashlib.sha256(hashlib.sha256(blk_hdr).digest()).digest()
+    return blk_hdr_hash[::-1].hex()
 
 def get_blk_dt(blk_hdr):
     members = struct.unpack("<I", blk_hdr[68:68+4])