new_contents: #!/usr/bin/env python3
  # Copyright (c) 2022 The Bitcoin Core developers
  # Distributed under the MIT software license, see the accompanying
  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
  """Helper routines relevant for compact block filters (BIP158).
  """
  from .siphash import siphash
  
  
  def bip158_basic_element_hash(script_pub_key, N, block_hash):
      """ Calculates the ranged hash of a filter element as defined in BIP158:
  
      'The first step in the filter construction is hashing the variable-sized
      raw items in the set to the range [0, F), where F = N * M.'
  
      'The items are first passed through the pseudorandom function SipHash, which takes a
      128-bit key k and a variable-sized byte vector and produces a uniformly random 64-bit
      output. Implementations of this BIP MUST use the SipHash parameters c = 2 and d = 4.'
  
      'The parameter k MUST be set to the first 16 bytes of the hash (in standard
      little-endian representation) of the block for which the filter is constructed. This
      ensures the key is deterministic while still varying from block to block.'
      """
      M = 784931
      block_hash_bytes = bytes.fromhex(block_hash)[::-1]
      k0 = int.from_bytes(block_hash_bytes[0:8], 'little')
      k1 = int.from_bytes(block_hash_bytes[8:16], 'little')
      return (siphash(k0, k1, script_pub_key) * (N * M)) >> 64
  
  
  def bip158_relevant_scriptpubkeys(node, block_hash):
      """ Determines the basic filter relvant scriptPubKeys as defined in BIP158:
  
      'A basic filter MUST contain exactly the following items for each transaction in a block:
         - The previous output script (the script being spent) for each input, except for
           the coinbase transaction.
         - The scriptPubKey of each output, aside from all OP_RETURN output scripts.'
      """
      spks = set()
      for tx in node.getblock(blockhash=block_hash, verbosity=3)['tx']:
          # gather prevout scripts
          for i in tx['vin']:
              if 'prevout' in i:
                  spks.add(bytes.fromhex(i['prevout']['scriptPubKey']['hex']))
          # gather output scripts
          for o in tx['vout']:
              if o['scriptPubKey']['type'] != 'nulldata':
                  spks.add(bytes.fromhex(o['scriptPubKey']['hex']))
      return spks
  
subject: add compact block filter (BIP158) helper routines