nimbus-eth1/fluffy/network/state/content/nibbles.nim

119 lines
3.0 KiB
Nim

# Fluffy
# Copyright (c) 2023-2024 Status Research & Development GmbH
# Licensed and distributed under either of
# * MIT license (license terms in the root directory or at https://opensource.org/licenses/MIT).
# * Apache v2 license (license terms in the root directory or at https://www.apache.org/licenses/LICENSE-2.0).
# at your option. This file may not be copied, modified, or distributed except according to those terms.
# As per spec:
# https://github.com/ethereum/portal-network-specs/blob/master/state-network.md#content-keys-and-content-ids
{.push raises: [].}
import
nimcrypto/hash,
results,
stint,
eth/common/eth_types,
ssz_serialization,
../../../common/common_types
export ssz_serialization, common_types, hash, results
const
MAX_PACKED_NIBBLES_LEN = 33
MAX_UNPACKED_NIBBLES_LEN = 64
type Nibbles* = List[byte, MAX_PACKED_NIBBLES_LEN]
type UnpackedNibbles* = seq[byte]
func init*(T: type Nibbles, packed: openArray[byte], isEven: bool): T =
doAssert(packed.len() <= MAX_PACKED_NIBBLES_LEN)
var output = newSeqOfCap[byte](packed.len() + 1)
if isEven:
output.add(0x00)
else:
doAssert(packed.len() > 0)
# set the first nibble to 1 and copy the second nibble from the input
output.add((packed[0] and 0x0F) or 0x10)
let startIdx = if isEven: 0 else: 1
for i in startIdx ..< packed.len():
output.add(packed[i])
Nibbles(output)
func empty*(T: type Nibbles): T =
Nibbles.init(@[], true)
func encode*(nibbles: Nibbles): seq[byte] =
SSZ.encode(nibbles)
func decode*(T: type Nibbles, bytes: openArray[byte]): Result[T, string] =
decodeSsz(bytes, T)
func packNibbles*(unpacked: openArray[byte]): Nibbles =
doAssert(
unpacked.len() <= MAX_UNPACKED_NIBBLES_LEN, "Can't pack more than 64 nibbles"
)
if unpacked.len() == 0:
return Nibbles(@[byte(0x00)])
let isEvenLength = unpacked.len() mod 2 == 0
var
output = newSeqOfCap[byte](unpacked.len() div 2 + 1)
highNibble = isEvenLength
currentByte: byte = 0
if isEvenLength:
output.add(0x00)
else:
currentByte = 0x10
for i, nibble in unpacked:
if highNibble:
currentByte = nibble shl 4
else:
output.add(currentByte or nibble)
currentByte = 0
highNibble = not highNibble
Nibbles(output)
func unpackNibbles*(packed: Nibbles): UnpackedNibbles =
doAssert(packed.len() <= MAX_PACKED_NIBBLES_LEN, "Packed nibbles length is too long")
var output = newSeqOfCap[byte](packed.len() * 2)
for i, pair in packed:
if i == 0 and pair == 0x00:
continue
let
first = (pair and 0xF0) shr 4
second = pair and 0x0F
if i == 0 and first == 0x01:
output.add(second)
else:
output.add(first)
output.add(second)
ensureMove(output)
func len(packed: Nibbles): int =
let lenExclPrefix = (packed.len() - 1) * 2
if packed[0] == 0x00: # is even length
lenExclPrefix
else:
lenExclPrefix + 1
func dropN*(unpacked: UnpackedNibbles, num: int): UnpackedNibbles =
var nibbles = unpacked
nibbles.setLen(nibbles.len() - num)
ensureMove(nibbles)