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// Copyright 2021-2023 Protocol Labs
// Copyright 2019-2022 ChainSafe Systems
// SPDX-License-Identifier: Apache-2.0, MIT
// disable this lint because it can actually cause performance regressions, and usually leads to
// hard to read code.
#![allow(clippy::comparison_chain)]
pub mod iter;
mod ops;
mod range;
mod rleplus;
mod unvalidated;
use std::collections::BTreeSet;
use std::ops::Range;
use iter::{ranges_from_bits, RangeIterator};
pub(crate) use range::RangeSize;
pub use rleplus::Error;
use thiserror::Error;
pub use unvalidated::{UnvalidatedBitField, Validate};
/// MaxEncodedSize is the maximum encoded size of a bitfield. When expanded into
/// a slice of runs, a bitfield of this size should not exceed 2MiB of memory.
///
/// This bitfield can fit at least 3072 sparse elements.
pub(crate) const MAX_ENCODED_SIZE: usize = 32 << 10;
#[derive(Clone, Error, Debug)]
#[error("bitfields may not include u64::MAX")]
pub struct OutOfRangeError;
impl From<OutOfRangeError> for Error {
fn from(_: OutOfRangeError) -> Self {
Error::RLEOverflow
}
}
/// A bit field with buffered insertion/removal that serializes to/from RLE+. Similar to
/// `HashSet<u64>`, but more memory-efficient when long runs of 1s and 0s are present.
#[derive(Debug, Default, Clone)]
pub struct BitField {
/// The underlying ranges of 1s.
ranges: Vec<Range<u64>>,
/// Bits set to 1. Never overlaps with `unset`.
set: BTreeSet<u64>,
/// Bits set to 0. Never overlaps with `set`.
unset: BTreeSet<u64>,
}
impl PartialEq for BitField {
fn eq(&self, other: &Self) -> bool {
Iterator::eq(self.ranges(), other.ranges())
}
}
/// Possibly a valid bitfield, or an out of bounds error. Ideally we'd just use a result, but we
/// can't implement [`FromIterator`] on a [`Result`] due to coherence.
///
/// You probably want to call [`BitField::try_from_bits`] instead of using this directly.
#[doc(hidden)]
pub enum MaybeBitField {
/// A valid bitfield.
Ok(BitField),
/// Out of bounds.
OutOfBounds,
}
impl MaybeBitField {
pub fn unwrap(self) -> BitField {
use MaybeBitField::*;
match self {
Ok(bf) => bf,
OutOfBounds => panic!("bitfield bit out of bounds"),
}
}
pub fn expect(self, message: &str) -> BitField {
use MaybeBitField::*;
match self {
Ok(bf) => bf,
OutOfBounds => panic!("{}", message),
}
}
}
impl TryFrom<MaybeBitField> for BitField {
type Error = OutOfRangeError;
fn try_from(value: MaybeBitField) -> Result<Self, Self::Error> {
match value {
MaybeBitField::Ok(bf) => Ok(bf),
MaybeBitField::OutOfBounds => Err(OutOfRangeError),
}
}
}
impl FromIterator<bool> for MaybeBitField {
fn from_iter<T: IntoIterator<Item = bool>>(iter: T) -> MaybeBitField {
let mut iter = iter.into_iter().fuse();
let bits = (0u64..u64::MAX)
.zip(&mut iter)
.filter(|&(_, b)| b)
.map(|(i, _)| i);
let bf = BitField::from_ranges(ranges_from_bits(bits));
// Now, if we have remaining bits, raise an error. Otherwise, we're good.
if iter.next().is_some() {
MaybeBitField::OutOfBounds
} else {
MaybeBitField::Ok(bf)
}
}
}
impl FromIterator<u64> for MaybeBitField {
fn from_iter<T: IntoIterator<Item = u64>>(iter: T) -> MaybeBitField {
let mut vec: Vec<_> = iter.into_iter().collect();
if vec.is_empty() {
MaybeBitField::Ok(BitField::new())
} else {
vec.sort_unstable();
vec.dedup();
if vec.last() == Some(&u64::MAX) {
MaybeBitField::OutOfBounds
} else {
MaybeBitField::Ok(BitField::from_ranges(ranges_from_bits(vec)))
}
}
}
}
impl BitField {
/// Creates an empty bit field.
pub const fn new() -> Self {
Self {
ranges: Vec::new(),
set: BTreeSet::new(),
unset: BTreeSet::new(),
}
}
/// Creates a new bit field from a `RangeIterator`.
pub fn from_ranges(iter: impl RangeIterator) -> Self {
Self {
ranges: iter.collect(),
..Default::default()
}
}
/// Tries to create a new bitfield from a bit iterator. It fails if the resulting bitfield would
/// contain values not in the range `0..u64::MAX` (non-inclusive).
pub fn try_from_bits<I>(iter: I) -> Result<Self, OutOfRangeError>
where
I: IntoIterator,
MaybeBitField: FromIterator<I::Item>,
{
iter.into_iter().collect::<MaybeBitField>().try_into()
}
/// Adds the bit at a given index to the bit field, panicing if it's out of range.
///
/// # Panics
///
/// Panics if `bit` is `u64::MAX`.
pub fn set(&mut self, bit: u64) {
self.try_set(bit).unwrap()
}
/// Adds the bit at a given index to the bit field, returning an error if it's out of range.
pub fn try_set(&mut self, bit: u64) -> Result<(), OutOfRangeError> {
if bit == u64::MAX {
return Err(OutOfRangeError);
}
self.unset.remove(&bit);
self.set.insert(bit);
Ok(())
}
/// Removes the bit at a given index from the bit field.
pub fn unset(&mut self, bit: u64) {
if bit == u64::MAX {
return;
}
self.set.remove(&bit);
self.unset.insert(bit);
}
/// Returns `true` if the bit field contains the bit at a given index.
pub fn get(&self, index: u64) -> bool {
if self.set.contains(&index) {
true
} else if self.unset.contains(&index) {
false
} else {
// since `self.ranges` is ordered, we can use a binary search to find out if
// any range in `self.ranges` contains `index`
use std::cmp::Ordering;
self.ranges
.binary_search_by(|range| {
if index < range.start {
Ordering::Greater
} else if index >= range.end {
Ordering::Less
} else {
// `index` is contained by this range
Ordering::Equal
}
})
// Ok(range) is returned if the closure returns `Equal` for a certain range,
// meaning a range in `self.ranges` contains the given index
.is_ok()
}
}
/// Returns the index of the lowest bit present in the bit field.
pub fn first(&self) -> Option<u64> {
match (
self.set.iter().min().copied(),
self.ranges
.iter()
.find_map(|r| r.clone().find(|i| !self.unset.contains(i))),
) {
(None, None) => None,
(Some(v), None) | (None, Some(v)) => Some(v),
(Some(a), Some(b)) => Some(std::cmp::min(a, b)),
}
}
/// Returns the index of the highest bit present in the bit field.
pub fn last(&self) -> Option<u64> {
match (
self.set.iter().max().copied(),
self.ranges
.iter()
// Last range first
.rev()
// Then reverse the ranges themselves and flatten.
.flat_map(|range| range.clone().rev())
// Finally find the first bit that isn't explicitly _unset_.
.find(|i| !self.unset.contains(i)),
) {
(None, None) => None,
(Some(v), None) | (None, Some(v)) => Some(v),
(Some(a), Some(b)) => Some(std::cmp::max(a, b)),
}
}
/// Returns an iterator over the indices of the bit field's set bits.
pub fn iter(&self) -> impl Iterator<Item = u64> + '_ {
// this code results in the same values as `self.ranges().flatten()`, but there's
// a key difference:
//
// `ranges()` needs to traverse both `self.set` and `self.unset` up front (so before
// iteration starts) in order to not have to visit each individual bit of `self.bitvec`
// during iteration, while here we can get away with only traversing `self.set` up
// front and checking `self.unset` containment for the candidate bits on the fly
// because we're visiting all bits either way
//
// consequently, the time complexity of `self.first()` is only linear in the length of
// `self.set`, not in the length of `self.unset` (as opposed to getting the first range
// with `self.ranges().next()` which is linear in both)
self.inner_ranges()
// set returns a sorted iterator.
.union(ranges_from_bits(self.set.iter().copied()))
.flatten()
.filter(move |i| !self.unset.contains(i))
}
/// Returns an iterator over the indices of the bit field's set bits if the number
/// of set bits in the bit field does not exceed `max`. Returns `None` otherwise.
pub fn bounded_iter(&self, max: u64) -> Option<impl Iterator<Item = u64> + '_> {
if self.len() <= max {
Some(self.iter())
} else {
None
}
}
/// Returns an iterator over the ranges without applying the set/unset bits.
fn inner_ranges(&self) -> impl RangeIterator + '_ {
iter::Ranges::new(self.ranges.iter().cloned())
}
/// Returns an iterator over the ranges of set bits that make up the bit field. The
/// ranges are in ascending order, are non-empty, and don't overlap.
pub fn ranges(&self) -> impl RangeIterator + '_ {
self.inner_ranges()
.union(ranges_from_bits(self.set.iter().copied()))
.difference(ranges_from_bits(self.unset.iter().copied()))
}
/// Returns `true` if the bit field is empty.
pub fn is_empty(&self) -> bool {
self.set.is_empty()
&& self
.inner_ranges()
.flatten()
.all(|bit| self.unset.contains(&bit))
}
/// Returns `true` if the bit field is _trivially_ empty. This is significantly faster than
/// checking if it's actually empty, but can be used to short-circuite certain operations.
fn is_trivially_empty(&self) -> bool {
self.set.is_empty() && self.ranges.is_empty()
}
/// Returns a slice of the bit field with the start index of set bits
/// and number of bits to include in the slice. Returns `None` if the bit
/// field contains fewer than `start + len` set bits.
pub fn slice(&self, start: u64, len: u64) -> Option<Self> {
let slice = BitField::from_ranges(self.ranges().skip_bits(start).take_bits(len));
if slice.len() == len {
Some(slice)
} else {
None
}
}
/// Returns the number of set bits in the bit field.
pub fn len(&self) -> u64 {
self.ranges().map(|range| range.size()).sum()
}
/// Returns a new bit field containing the bits in `self` that remain
/// after "cutting" out the bits in `other`, and shifting remaining
/// bits to the left if necessary. For example:
///
/// ```txt
/// lhs: xx-xxx--x
/// rhs: -xx-x----
///
/// cut: x x x--x
/// output: xxx--x
/// ```
pub fn cut(&self, other: &Self) -> Self {
Self::from_ranges(self.ranges().cut(other.ranges()))
}
/// Returns the union of the given bit fields as a new bit field.
pub fn union<'a>(bitfields: impl IntoIterator<Item = &'a Self>) -> Self {
bitfields.into_iter().fold(Self::new(), |a, b| a | b)
}
/// Returns true if `self` overlaps with `other`.
pub fn contains_any(&self, other: &BitField) -> bool {
!(self.is_trivially_empty() || other.is_trivially_empty())
&& self.ranges().intersection(other.ranges()).next().is_some()
}
/// Returns true if the `self` is a superset of `other`.
pub fn contains_all(&self, other: &BitField) -> bool {
other.is_trivially_empty() || other.ranges().difference(self.ranges()).next().is_none()
}
}
/// Constructs a `BitField` from a given list of 1s and 0s.
///
/// # Examples
///
/// ```
/// use fvm_ipld_bitfield::bitfield;
///
/// let mut bf = bitfield![0, 1, 1, 0, 1, 0, 0, 0, 1, 1];
/// assert!(bf.get(1));
/// assert!(!bf.get(3));
/// bf.set(3);
/// assert_eq!(bf.len(), 6);
/// assert_eq!(bf.ranges().next(), Some(1..5));
/// ```
#[macro_export]
macro_rules! bitfield {
(@iter) => {
std::iter::empty::<bool>()
};
(@iter $head:literal $(, $tail:literal)*) => {
std::iter::once($head != 0_u32).chain(bitfield!(@iter $($tail),*))
};
($($val:literal),* $(,)?) => {
bitfield!(@iter $($val),*).collect::<$crate::MaybeBitField>().unwrap()
};
}
#[cfg(feature = "json")]
pub mod json {
use serde::ser::SerializeSeq;
use serde::{Deserialize, Deserializer, Serialize, Serializer};
use super::*;
use crate::iter::Ranges;
#[derive(Deserialize, Serialize, Debug, PartialEq)]
#[serde(transparent)]
pub struct BitFieldJson(#[serde(with = "self")] pub BitField);
/// Wrapper for serializing a UnsignedMessage reference to JSON.
#[derive(Serialize)]
#[serde(transparent)]
pub struct BitFieldJsonRef<'a>(#[serde(with = "self")] pub &'a BitField);
impl From<BitFieldJson> for BitField {
fn from(wrapper: BitFieldJson) -> Self {
wrapper.0
}
}
impl From<BitField> for BitFieldJson {
fn from(wrapper: BitField) -> Self {
BitFieldJson(wrapper)
}
}
fn serialize<S>(m: &BitField, serializer: S) -> std::result::Result<S::Ok, S::Error>
where
S: Serializer,
{
if !m.is_empty() {
let mut seq = serializer.serialize_seq(None)?;
m.ranges().try_fold(0, |last_index, range| {
let zero_index = range.start - last_index;
let nonzero_index = range.end - range.start;
seq.serialize_element(&zero_index)?;
seq.serialize_element(&nonzero_index)?;
Ok(range.end)
})?;
seq.end()
} else {
let mut seq = serializer.serialize_seq(Some(1))?;
seq.serialize_element(&0)?;
seq.end()
}
}
fn deserialize<'de, D>(deserializer: D) -> std::result::Result<BitField, D::Error>
where
D: Deserializer<'de>,
{
let bitfield_bytes: Vec<u64> = Deserialize::deserialize(deserializer)?;
let mut ranges: Vec<Range<u64>> = Vec::new();
bitfield_bytes.iter().fold((false, 0), |last, index| {
let (should_set, last_index) = last;
let ending_index = index + last_index;
if should_set {
ranges.push(Range {
start: last_index,
end: ending_index,
})
}
(!should_set, ending_index)
});
let ranges = Ranges::new(ranges.iter().cloned());
Ok(BitField::from_ranges(ranges))
}
#[test]
fn serialization_starts_with_zeros() {
let bf = BitFieldJson(bitfield![0, 0, 1, 1, 1, 1, 0, 0, 0, 1, 1]);
let j = serde_json::to_string(&bf).unwrap();
assert_eq!(j, "[2,4,3,2]");
let bitfield: BitFieldJson = serde_json::from_str(&j).unwrap();
assert_eq!(bf, bitfield);
}
#[test]
fn serialization_starts_with_ones() {
let bf = BitFieldJson(bitfield![1, 1, 1, 1, 1, 1, 0, 0, 0, 1, 1]);
let j = serde_json::to_string(&bf).unwrap();
assert_eq!(j, "[0,6,3,2]");
let bitfield: BitFieldJson = serde_json::from_str(&j).unwrap();
assert_eq!(bf, bitfield);
}
#[test]
fn serialization_with_single_unut() {
let bf = BitFieldJson(bitfield![]);
let j = serde_json::to_string(&bf).unwrap();
assert_eq!(j, "[0]");
let bitfield: BitFieldJson = serde_json::from_str(&j).unwrap();
assert_eq!(bf, bitfield);
}
}