Helpers for generalized_indices

SSZ provides a set of helper functions to manipulate generalized_indices

It comes with a WARNING

Usage note: functions outside this section should manipulate generalized indices using only functions inside this section. This is to make it easier for developers to implement generalized indices with underlying representations other than bigints.

  • concat_generalized_indices(*indices: GeneralizedIndex) -> GeneralizedIndex:
    • Given generalized indices i1 for A -> B, i2 for B -> C .... i_n for Y -> Z,
    • returns the generalized index for A -> Z.
    • o = GeneralizedIndex(1)

for i in indices:

o = GeneralizedIndex(o * get_power_of_two_floor(i) + (i - get_power_of_two_floor(i)))

return o
  • get_generalized_index_length(index: GeneralizedIndex) -> int:
    • Return the length of a path represented by a generalized index.
    • return int(log2(index))
  • get_generalized_index_bit(index: GeneralizedIndex, position: int) -> bool:
    • Return the given bit of a generalized index.
    • return (index & (1 << position)) > 0
  • generalized_index_sibling(index: GeneralizedIndex) -> GeneralizedIndex:
    • return GeneralizedIndex(index ^ 1)
  • generalized_index_child(index: GeneralizedIndex, right_side: bool) -> GeneralizedIndex:

return GeneralizedIndex(index * 2 + right_side)

  • generalized_index_parent(index: GeneralizedIndex) -> GeneralizedIndex:

    return GeneralizedIndex(index // 2)

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