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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
// Licensed under Apache License v2.0 with Runtime Library Exception
//
// See https://swift.org/LICENSE.txt for license information
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//
/// A simple bitmap of a fixed number of bits, implementing a sorted set of
/// small nonnegative Int values.
///
/// Because `_UnsafeBitset` implements a flat bit vector, it isn't suitable for
/// holding arbitrarily large integers. The maximal element a bitset can store
/// is fixed at its initialization.
@frozen
@usableFromInline // @testable
internal struct _UnsafeBitset {
@usableFromInline
internal let words: UnsafeMutablePointer<Word>
@usableFromInline
internal let wordCount: Int
@inlinable
@inline(__always)
internal init(words: UnsafeMutablePointer<Word>, wordCount: Int) {
self.words = words
self.wordCount = wordCount
}
}
@available(*, unavailable)
extension _UnsafeBitset: Sendable {}
extension _UnsafeBitset {
@inlinable
@inline(__always)
internal static func word(for element: Int) -> Int {
_internalInvariant(element >= 0)
// Note: We perform on UInts to get faster unsigned math (shifts).
let element = UInt(bitPattern: element)
let capacity = UInt(bitPattern: Word.capacity)
return Int(bitPattern: element / capacity)
}
@inlinable
@inline(__always)
internal static func bit(for element: Int) -> Int {
_internalInvariant(element >= 0)
// Note: We perform on UInts to get faster unsigned math (masking).
let element = UInt(bitPattern: element)
let capacity = UInt(bitPattern: Word.capacity)
return Int(bitPattern: element % capacity)
}
@inlinable
@inline(__always)
internal static func split(_ element: Int) -> (word: Int, bit: Int) {
return (word(for: element), bit(for: element))
}
@inlinable
@inline(__always)
internal static func join(word: Int, bit: Int) -> Int {
_internalInvariant(bit >= 0 && bit < Word.capacity)
return word &* Word.capacity &+ bit
}
}
extension _UnsafeBitset {
@inlinable
@inline(__always)
internal static func wordCount(forCapacity capacity: Int) -> Int {
return word(for: capacity &+ Word.capacity &- 1)
}
@inlinable
internal var capacity: Int {
@inline(__always)
get {
return wordCount &* Word.capacity
}
}
@inlinable
@inline(__always)
internal func isValid(_ element: Int) -> Bool {
return element >= 0 && element <= capacity
}
@inlinable
@inline(__always)
internal func uncheckedContains(_ element: Int) -> Bool {
_internalInvariant(isValid(element))
let (word, bit) = _UnsafeBitset.split(element)
return words[word].uncheckedContains(bit)
}
@inlinable
@inline(__always)
@discardableResult
internal func uncheckedInsert(_ element: Int) -> Bool {
_internalInvariant(isValid(element))
let (word, bit) = _UnsafeBitset.split(element)
return words[word].uncheckedInsert(bit)
}
@inlinable
@inline(__always)
@discardableResult
internal func uncheckedRemove(_ element: Int) -> Bool {
_internalInvariant(isValid(element))
let (word, bit) = _UnsafeBitset.split(element)
return words[word].uncheckedRemove(bit)
}
@inlinable
@inline(__always)
internal func clear() {
words.update(repeating: .empty, count: wordCount)
}
}
extension _UnsafeBitset: Sequence {
@usableFromInline
internal typealias Element = Int
@inlinable
internal var count: Int {
var count = 0
for w in 0 ..< wordCount {
count += words[w].count
}
return count
}
@inlinable
internal var underestimatedCount: Int {
return count
}
@inlinable
func makeIterator() -> Iterator {
return Iterator(self)
}
@usableFromInline
@frozen
internal struct Iterator: IteratorProtocol {
@usableFromInline
internal let bitset: _UnsafeBitset
@usableFromInline
internal var index: Int
@usableFromInline
internal var word: Word
@inlinable
internal init(_ bitset: _UnsafeBitset) {
self.bitset = bitset
self.index = 0
self.word = bitset.wordCount > 0 ? bitset.words[0] : .empty
}
@inlinable
internal mutating func next() -> Int? {
if let bit = word.next() {
return _UnsafeBitset.join(word: index, bit: bit)
}
while (index + 1) < bitset.wordCount {
index += 1
word = bitset.words[index]
if let bit = word.next() {
return _UnsafeBitset.join(word: index, bit: bit)
}
}
return nil
}
}
}
@available(*, unavailable)
extension _UnsafeBitset.Iterator: Sendable {}
////////////////////////////////////////////////////////////////////////////////
extension _UnsafeBitset {
@frozen
@usableFromInline
internal struct Word {
@usableFromInline
internal var value: UInt
@inlinable
internal init(_ value: UInt) {
self.value = value
}
}
}
extension _UnsafeBitset.Word {
@inlinable
internal static var capacity: Int {
@inline(__always)
get {
return UInt.bitWidth
}
}
@inlinable
@inline(__always)
internal func uncheckedContains(_ bit: Int) -> Bool {
_internalInvariant(bit >= 0 && bit < UInt.bitWidth)
return value & (1 &<< bit) != 0
}
@inlinable
@inline(__always)
@discardableResult
internal mutating func uncheckedInsert(_ bit: Int) -> Bool {
_internalInvariant(bit >= 0 && bit < UInt.bitWidth)
let mask: UInt = 1 &<< bit
let inserted = value & mask == 0
value |= mask
return inserted
}
@inlinable
@inline(__always)
@discardableResult
internal mutating func uncheckedRemove(_ bit: Int) -> Bool {
_internalInvariant(bit >= 0 && bit < UInt.bitWidth)
let mask: UInt = 1 &<< bit
let removed = value & mask != 0
value &= ~mask
return removed
}
}
extension _UnsafeBitset.Word {
@inlinable
var minimum: Int? {
@inline(__always)
get {
guard value != 0 else { return nil }
return value.trailingZeroBitCount
}
}
@inlinable
var maximum: Int? {
@inline(__always)
get {
guard value != 0 else { return nil }
return _UnsafeBitset.Word.capacity &- 1 &- value.leadingZeroBitCount
}
}
@inlinable
var complement: _UnsafeBitset.Word {
@inline(__always)
get {
return _UnsafeBitset.Word(~value)
}
}
@inlinable
@inline(__always)
internal func subtracting(elementsBelow bit: Int) -> _UnsafeBitset.Word {
_internalInvariant(bit >= 0 && bit < _UnsafeBitset.Word.capacity)
let mask = UInt.max &<< bit
return _UnsafeBitset.Word(value & mask)
}
@inlinable
@inline(__always)
internal func intersecting(elementsBelow bit: Int) -> _UnsafeBitset.Word {
_internalInvariant(bit >= 0 && bit < _UnsafeBitset.Word.capacity)
let mask: UInt = (1 as UInt &<< bit) &- 1
return _UnsafeBitset.Word(value & mask)
}
@inlinable
@inline(__always)
internal func intersecting(elementsAbove bit: Int) -> _UnsafeBitset.Word {
_internalInvariant(bit >= 0 && bit < _UnsafeBitset.Word.capacity)
let mask = (UInt.max &<< bit) &<< 1
return _UnsafeBitset.Word(value & mask)
}
}
extension _UnsafeBitset.Word {
@inlinable
internal static var empty: _UnsafeBitset.Word {
@inline(__always)
get {
return _UnsafeBitset.Word(0)
}
}
@inlinable
internal static var allBits: _UnsafeBitset.Word {
@inline(__always)
get {
return _UnsafeBitset.Word(UInt.max)
}
}
}
// Word implements Sequence by using a copy of itself as its Iterator.
// Iteration with `next()` destroys the word's value; however, this won't cause
// problems in normal use, because `next()` is usually called on a separate
// iterator, not the original word.
extension _UnsafeBitset.Word: Sequence, IteratorProtocol {
#if $NoncopyableGenerics
@usableFromInline
typealias Element = Int
#endif
@inlinable
internal var count: Int {
return value.nonzeroBitCount
}
@inlinable
internal var underestimatedCount: Int {
return count
}
@inlinable
internal var isEmpty: Bool {
@inline(__always)
get {
return value == 0
}
}
/// Return the index of the lowest set bit in this word,
/// and also destructively clear it.
@inlinable
internal mutating func next() -> Int? {
guard value != 0 else { return nil }
let bit = value.trailingZeroBitCount
value &= value &- 1 // Clear lowest nonzero bit.
return bit
}
}
extension _UnsafeBitset {
@_alwaysEmitIntoClient
@inline(__always)
internal static func _withTemporaryUninitializedBitset<R>(
wordCount: Int,
body: (_UnsafeBitset) throws -> R
) rethrows -> R {
try withUnsafeTemporaryAllocation(
of: _UnsafeBitset.Word.self, capacity: wordCount
) { buffer in
let bitset = _UnsafeBitset(
words: buffer.baseAddress!, wordCount: buffer.count)
return try body(bitset)
}
}
@_alwaysEmitIntoClient
@inline(__always)
internal static func withTemporaryBitset<R>(
capacity: Int,
body: (_UnsafeBitset) throws -> R
) rethrows -> R {
let wordCount = Swift.max(1, Self.wordCount(forCapacity: capacity))
return try _withTemporaryUninitializedBitset(
wordCount: wordCount
) { bitset in
bitset.clear()
return try body(bitset)
}
}
}
extension _UnsafeBitset {
@_alwaysEmitIntoClient
@inline(__always)
internal static func withTemporaryCopy<R>(
of original: _UnsafeBitset,
body: (_UnsafeBitset) throws -> R
) rethrows -> R {
try _withTemporaryUninitializedBitset(
wordCount: original.wordCount
) { bitset in
bitset.words.initialize(from: original.words, count: original.wordCount)
return try body(bitset)
}
}
}
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