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use codec::{
Compact,
Input,
};
use scale_bits::{
scale::format::{
Format,
OrderFormat,
StoreFormat,
},
Bits,
};
use std::marker::PhantomData;
macro_rules! store {
($ident: ident; $(($ty: ident, $wrapped: ty)),*) => {
pub trait $ident {
const FORMAT: StoreFormat;
const BITS: u32;
}
$(
impl $ident for $wrapped {
const FORMAT: StoreFormat = StoreFormat::$ty;
const BITS: u32 = <$wrapped>::BITS;
}
)*
};
}
macro_rules! order {
($ident: ident; $($ty: ident),*) => {
pub trait $ident {
const FORMAT: OrderFormat;
}
$(
#[doc = concat!("Type-level value that corresponds to `scale_bits::OrderFormat::", stringify!($ty), "` at run-time")]
#[doc = concat!(" and `bitvec::order::BitOrder::", stringify!($ty), "` at the type level.")]
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum $ty {}
impl $ident for $ty {
const FORMAT: OrderFormat = OrderFormat::$ty;
}
)*
};
}
store!(BitStore; (U8, u8), (U16, u16), (U32, u32), (U64, u64));
order!(BitOrder; Lsb0, Msb0);
fn bit_format<Store: BitStore, Order: BitOrder>() -> Format {
Format {
order: Order::FORMAT,
store: Store::FORMAT,
}
}
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct DecodedBits<Store: BitStore, Order: BitOrder>(
Bits,
PhantomData<Store>,
PhantomData<Order>,
);
impl<Store: BitStore, Order: BitOrder> DecodedBits<Store, Order> {
pub fn into_bits(self) -> Bits {
self.0
}
pub fn as_bits(&self) -> &Bits {
&self.0
}
}
impl<Store: BitStore, Order: BitOrder> core::iter::FromIterator<bool>
for DecodedBits<Store, Order>
{
fn from_iter<T: IntoIterator<Item = bool>>(iter: T) -> Self {
DecodedBits(Bits::from_iter(iter), PhantomData, PhantomData)
}
}
impl<Store: BitStore, Order: BitOrder> codec::Decode for DecodedBits<Store, Order> {
fn decode<I: Input>(input: &mut I) -> Result<Self, codec::Error> {
const ARCH32BIT_BITSLICE_MAX_BITS: u32 = 0x1fff_ffff;
let Compact(bits) = <Compact<u32>>::decode(input)?;
if bits > ARCH32BIT_BITSLICE_MAX_BITS {
return Err("Attempt to decode a BitVec with too many bits".into())
}
let elements = (bits / Store::BITS) + u32::from(bits % Store::BITS != 0);
let bytes_in_elem = Store::BITS.saturating_div(u8::BITS);
let bytes_needed = (elements * bytes_in_elem) as usize;
let mut storage = codec::Encode::encode(&Compact(bits));
let prefix_len = storage.len();
storage.reserve_exact(bytes_needed);
storage.extend(vec![0; bytes_needed]);
input.read(&mut storage[prefix_len..])?;
let decoder =
scale_bits::decode_using_format_from(&storage, bit_format::<Store, Order>())?;
let bits = decoder.collect::<Result<Vec<_>, _>>()?;
let bits = Bits::from_iter(bits);
Ok(DecodedBits(bits, PhantomData, PhantomData))
}
}
impl<Store: BitStore, Order: BitOrder> codec::Encode for DecodedBits<Store, Order> {
fn size_hint(&self) -> usize {
self.0.size_hint()
}
fn encoded_size(&self) -> usize {
self.0.encoded_size()
}
fn encode(&self) -> Vec<u8> {
scale_bits::encode_using_format(self.0.iter(), bit_format::<Store, Order>())
}
}
#[cfg(test)]
mod tests {
use super::*;
use core::fmt::Debug;
use bitvec::vec::BitVec;
use codec::Decode as _;
trait ToBitVec {
type Order: bitvec::order::BitOrder;
}
impl ToBitVec for Lsb0 {
type Order = bitvec::order::Lsb0;
}
impl ToBitVec for Msb0 {
type Order = bitvec::order::Msb0;
}
fn scales_like_bitvec_and_roundtrips<
'a,
Store: BitStore + bitvec::store::BitStore + PartialEq,
Order: BitOrder + ToBitVec + Debug + PartialEq,
>(
input: impl IntoIterator<Item = &'a bool>,
) where
BitVec<Store, <Order as ToBitVec>::Order>: codec::Encode + codec::Decode,
{
let input: Vec<_> = input.into_iter().copied().collect();
let decoded_bits = DecodedBits::<Store, Order>::from_iter(input.clone());
let bitvec = BitVec::<Store, <Order as ToBitVec>::Order>::from_iter(input);
let decoded_bits_encoded = codec::Encode::encode(&decoded_bits);
let bitvec_encoded = codec::Encode::encode(&bitvec);
assert_eq!(decoded_bits_encoded, bitvec_encoded);
let decoded_bits_decoded =
DecodedBits::<Store, Order>::decode(&mut &decoded_bits_encoded[..])
.expect("SCALE-encoding DecodedBits to roundtrip");
let bitvec_decoded =
BitVec::<Store, <Order as ToBitVec>::Order>::decode(&mut &bitvec_encoded[..])
.expect("SCALE-encoding BitVec to roundtrip");
assert_eq!(decoded_bits, decoded_bits_decoded);
assert_eq!(bitvec, bitvec_decoded);
}
#[test]
fn decoded_bitvec_scales_and_roundtrips() {
let test_cases = [
vec![],
vec![true],
vec![false],
vec![true, false, true],
vec![true, false, true, false, false, false, false, false, true],
[vec![true; 5], vec![false; 5], vec![true; 1], vec![false; 3]].concat(),
[vec![true; 9], vec![false; 9], vec![true; 9], vec![false; 9]].concat(),
];
for test_case in &test_cases {
scales_like_bitvec_and_roundtrips::<u8, Lsb0>(test_case);
scales_like_bitvec_and_roundtrips::<u16, Lsb0>(test_case);
scales_like_bitvec_and_roundtrips::<u32, Lsb0>(test_case);
scales_like_bitvec_and_roundtrips::<u64, Lsb0>(test_case);
scales_like_bitvec_and_roundtrips::<u8, Msb0>(test_case);
scales_like_bitvec_and_roundtrips::<u16, Msb0>(test_case);
scales_like_bitvec_and_roundtrips::<u32, Msb0>(test_case);
scales_like_bitvec_and_roundtrips::<u64, Msb0>(test_case);
}
}
}