mirror of
https://github.com/status-im/nimbus-eth2.git
synced 2025-01-09 22:06:21 +00:00
4d6b068697
* add `on_startup` genesis state constructor * update state transition to use ssz * update validator adder
80 lines
3.0 KiB
Nim
80 lines
3.0 KiB
Nim
# beacon_chain
|
|
# Copyright (c) 2018 Status Research & Development GmbH
|
|
# Licensed and distributed under either of
|
|
# * MIT license (license terms in the root directory or at http://opensource.org/licenses/MIT).
|
|
# * Apache v2 license (license terms in the root directory or at http://www.apache.org/licenses/LICENSE-2.0).
|
|
# at your option. This file may not be copied, modified, or distributed except according to those terms.
|
|
|
|
# Uncategorized helper functions from the spec
|
|
|
|
import ./datatypes, ./digest, sequtils, math
|
|
|
|
func shuffle*[T](values: seq[T], seed: Eth2Digest): seq[T] =
|
|
## Returns the shuffled ``values`` with seed as entropy.
|
|
## TODO: this calls out for tests, but I odn't particularly trust spec
|
|
## right now.
|
|
|
|
let values_count = values.len
|
|
|
|
const
|
|
# Entropy is consumed from the seed in 3-byte (24 bit) chunks.
|
|
rand_bytes = 3
|
|
# The highest possible result of the RNG.
|
|
rand_max = 2^(rand_bytes * 8) - 1
|
|
|
|
# The range of the RNG places an upper-bound on the size of the list that
|
|
# may be shuffled. It is a logic error to supply an oversized list.
|
|
assert values_count < rand_max
|
|
|
|
result = values
|
|
var
|
|
source = seed
|
|
index = 0
|
|
while index < values_count - 1:
|
|
# Re-hash the `source` to obtain a new pattern of bytes.
|
|
source = eth2hash source.data
|
|
|
|
# Iterate through the `source` bytes in 3-byte chunks.
|
|
for pos in countup(0, 29, 3):
|
|
let remaining = values_count - index
|
|
if remaining == 1:
|
|
break
|
|
|
|
# Read 3-bytes of `source` as a 24-bit big-endian integer.
|
|
let sample_from_source =
|
|
source.data[pos].Uint24 shl 16 or
|
|
source.data[pos+1].Uint24 shl 8 or
|
|
source.data[pos+2].Uint24
|
|
|
|
# Sample values greater than or equal to `sample_max` will cause
|
|
# modulo bias when mapped into the `remaining` range.
|
|
let sample_max = rand_max - rand_max mod remaining
|
|
|
|
# Perform a swap if the consumed entropy will not cause modulo bias.
|
|
if sample_from_source < sample_max:
|
|
# Select a replacement index for the current index.
|
|
let replacement_position = sample_from_source mod remaining + index
|
|
swap result[index], result[replacement_position]
|
|
inc index
|
|
|
|
func split*[T](lst: openArray[T], N: Positive): seq[seq[T]] =
|
|
## split lst in N pieces, with each piece having `len(lst) div N` or
|
|
## `len(lst) div N + 1` pieces
|
|
# TODO: implement as an iterator
|
|
result = newSeq[seq[T]](N)
|
|
for i in 0 ..< N:
|
|
result[i] = lst[lst.len * i div N ..< lst.len * (i+1) div N] # TODO: avoid alloc via toOpenArray
|
|
|
|
func get_new_recent_block_hashes*(old_block_hashes: seq[Eth2Digest],
|
|
parent_slot, current_slot: int64,
|
|
parent_hash: Eth2Digest
|
|
): seq[Eth2Digest] =
|
|
|
|
# Should throw for `current_slot - CYCLE_LENGTH * 2 - 1` according to spec comment
|
|
let d = current_slot - parent_slot
|
|
result = old_block_hashes[d .. ^1]
|
|
for _ in 0 ..< min(d, old_block_hashes.len):
|
|
result.add parent_hash
|
|
|
|
func ceil_div8*(v: int): int = (v + 7) div 8
|