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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2021 - 2024 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
//
//===----------------------------------------------------------------------===//
extension BitArray {
/// Initialize a bit array from a bit set.
///
/// The result contains exactly as many bits as the maximum item in
/// the source set, plus one. If the set is empty, the result will
/// be empty, too.
///
/// BitArray([] as BitSet) // (empty)
/// BitArray([0] as BitSet) // 1
/// BitArray([1] as BitSet) // 10
/// BitArray([1, 2, 4] as BitSet) // 1011
/// BitArray([7] as BitSet) // 1000000
///
/// - Complexity: O(1)
public init(_ set: BitSet) {
guard let l = set.last else { self.init(); return }
self.init(_storage: set._storage, count: l + 1)
}
/// Initialize a bit array from the binary representation of an integer.
/// The result will contain exactly `value.bitWidth` bits.
///
/// BitArray(bitPattern: 3 as UInt8) // 00000011
/// BitArray(bitPattern: 42 as Int8) // 00101010
/// BitArray(bitPattern: -1 as Int8) // 11111111
/// BitArray(bitPattern: 3 as Int16) // 0000000000000111
/// BitArray(bitPattern: 42 as Int16) // 0000000000101010
/// BitArray(bitPattern: -1 as Int16) // 1111111111111111
/// BitArray(bitPattern: 3 as Int) // 0000000000...0000000111
/// BitArray(bitPattern: 42 as Int) // 0000000000...0000101010
/// BitArray(bitPattern: -1 as Int) // 1111111111...1111111111
///
/// - Complexity: O(value.bitWidth)
public init(bitPattern value: some BinaryInteger) {
var words = value.words.map { _Word($0) }
let count = value.bitWidth
if words.isEmpty {
precondition(count == 0, "Inconsistent bitWidth")
} else {
let (w, b) = _UnsafeHandle._BitPosition(count).endSplit
precondition(words.count == w + 1, "Inconsistent bitWidth")
words[w].formIntersection(_Word(upTo: b))
}
self.init(_storage: words, count: count)
}
/// Creates a new, empty bit array with preallocated space for at least the
/// specified number of elements.
public init(minimumCapacity: Int) {
self.init()
reserveCapacity(minimumCapacity)
}
}
extension BinaryInteger {
@inlinable
internal static func _convert(
_ source: BitArray
) -> (value: Self, isNegative: Bool) {
var value: Self = .zero
let isNegative = source._foreachTwosComplementWordDownward(
isSigned: Self.isSigned
) { _, word in
value <<= UInt.bitWidth
value |= Self(truncatingIfNeeded: word)
return true
}
return (value, isNegative)
}
/// Creates a new instance by truncating or extending the bits in the given
/// bit array, as needed. The bit at position 0 in `source` will correspond
/// to the least-significant bit in the result.
///
/// If `Self` is an unsigned integer type, then the result will contain as
/// many bits from `source` it can accommodate, truncating off any extras.
///
/// UInt8(truncatingIfNeeded: "" as BitArray) // 0
/// UInt8(truncatingIfNeeded: "0" as BitArray) // 0
/// UInt8(truncatingIfNeeded: "1" as BitArray) // 1
/// UInt8(truncatingIfNeeded: "11" as BitArray) // 3
/// UInt8(truncatingIfNeeded: "11111111" as BitArray) // 255
/// UInt8(truncatingIfNeeded: "1100000001" as BitArray) // 1
/// UInt8(truncatingIfNeeded: "1100000101" as BitArray) // 5
///
/// If `Self` is a signed integer type, then the contents of the bit array
/// are interpreted to be a two's complement representation of a signed
/// integer value, with the last bit in the array representing the sign of
/// the result.
///
/// Int8(truncatingIfNeeded: "" as BitArray) // 0
/// Int8(truncatingIfNeeded: "0" as BitArray) // 0
/// Int8(truncatingIfNeeded: "1" as BitArray) // -1
/// Int8(truncatingIfNeeded: "01" as BitArray) // 1
/// Int8(truncatingIfNeeded: "101" as BitArray) // -3
/// Int8(truncatingIfNeeded: "0101" as BitArray) // 5
///
/// Int8(truncatingIfNeeded: "00000001" as BitArray) // 1
/// Int8(truncatingIfNeeded: "00000101" as BitArray) // 5
/// Int8(truncatingIfNeeded: "01111111" as BitArray) // 127
/// Int8(truncatingIfNeeded: "10000000" as BitArray) // -128
/// Int8(truncatingIfNeeded: "11111111" as BitArray) // -1
///
/// Int8(truncatingIfNeeded: "000011111111" as BitArray) // -1
/// Int8(truncatingIfNeeded: "111100000000" as BitArray) // 0
/// Int8(truncatingIfNeeded: "111100000001" as BitArray) // 1
@inlinable
public init(truncatingIfNeeded source: BitArray) {
self = Self._convert(source).value
}
/// Creates a new instance from the bits in the given bit array, if the
/// corresponding integer value can be represented exactly.
/// If the value is not representable exactly, then the result is `nil`.
///
/// If `Self` is an unsigned integer type, then the contents of the bit array
/// are interpreted to be the binary representation of a nonnegative
/// integer value. The bit array is allowed to contain bits in unrepresentable
/// positions, as long as they are all cleared.
///
/// UInt8(exactly: "" as BitArray) // 0
/// UInt8(exactly: "0" as BitArray) // 0
/// UInt8(exactly: "1" as BitArray) // 1
/// UInt8(exactly: "10" as BitArray) // 2
/// UInt8(exactly: "00000000" as BitArray) // 0
/// UInt8(exactly: "11111111" as BitArray) // 255
/// UInt8(exactly: "0000000000000" as BitArray) // 0
/// UInt8(exactly: "0000011111111" as BitArray) // 255
/// UInt8(exactly: "0000100000000" as BitArray) // nil
/// UInt8(exactly: "1111111111111" as BitArray) // nil
///
/// If `Self` is a signed integer type, then the contents of the bit array
/// are interpreted to be a two's complement representation of a signed
/// integer value, with the last bit in the array representing the sign of
/// the result.
///
/// Int8(exactly: "" as BitArray) // 0
/// Int8(exactly: "0" as BitArray) // 0
/// Int8(exactly: "1" as BitArray) // -1
/// Int8(exactly: "01" as BitArray) // 1
/// Int8(exactly: "101" as BitArray) // -3
/// Int8(exactly: "0101" as BitArray) // 5
///
/// Int8(exactly: "00000001" as BitArray) // 1
/// Int8(exactly: "00000101" as BitArray) // 5
/// Int8(exactly: "01111111" as BitArray) // 127
/// Int8(exactly: "10000000" as BitArray) // -128
/// Int8(exactly: "11111111" as BitArray) // -1
///
/// Int8(exactly: "00000000000" as BitArray) // 0
/// Int8(exactly: "00001111111" as BitArray) // 127
/// Int8(exactly: "00010000000" as BitArray) // nil
/// Int8(exactly: "11101111111" as BitArray) // nil
/// Int8(exactly: "11110000000" as BitArray) // -128
/// Int8(exactly: "11111111111" as BitArray) // -1
@inlinable
public init?(exactly source: BitArray) {
let (value, isNegative) = Self._convert(source)
guard isNegative == (value < 0) else { return nil }
let words = value.words
var equal = true
_ = source._foreachTwosComplementWordDownward(isSigned: Self.isSigned) { i, word in
assert(equal)
let w = (
i < words.count ? words[i]
: isNegative ? UInt.max
: UInt.zero)
equal = (w == word)
return equal
}
guard equal else { return nil }
self = value
}
/// Creates a new instance from the bits in the given bit array, if the
/// corresponding integer value can be represented exactly.
/// If the value is not representable exactly, then a runtime error will
/// occur.
///
/// If `Self` is an unsigned integer type, then the contents of the bit array
/// are interpreted to be the binary representation of a nonnegative
/// integer value. The bit array is allowed to contain bits in unrepresentable
/// positions, as long as they are all cleared.
///
/// UInt8("" as BitArray) // 0
/// UInt8("0" as BitArray) // 0
/// UInt8("1" as BitArray) // 1
/// UInt8("10" as BitArray) // 2
/// UInt8("00000000" as BitArray) // 0
/// UInt8("11111111" as BitArray) // 255
/// UInt8("0000000000000" as BitArray) // 0
/// UInt8("0000011111111" as BitArray) // 255
/// UInt8("0000100000000" as BitArray) // ERROR
/// UInt8("1111111111111" as BitArray) // ERROR
///
/// If `Self` is a signed integer type, then the contents of the bit array
/// are interpreted to be a two's complement representation of a signed
/// integer value, with the last bit in the array representing the sign of
/// the result.
///
/// Int8("" as BitArray) // 0
/// Int8("0" as BitArray) // 0
/// Int8("1" as BitArray) // -1
/// Int8("01" as BitArray) // 1
/// Int8("101" as BitArray) // -3
/// Int8("0101" as BitArray) // 5
///
/// Int8("00000001" as BitArray) // 1
/// Int8("00000101" as BitArray) // 5
/// Int8("01111111" as BitArray) // 127
/// Int8("10000000" as BitArray) // -128
/// Int8("11111111" as BitArray) // -1
///
/// Int8("00000000000" as BitArray) // 0
/// Int8("00001111111" as BitArray) // 127
/// Int8("00010000000" as BitArray) // ERROR
/// Int8("11101111111" as BitArray) // ERROR
/// Int8("11110000000" as BitArray) // -128
/// Int8("11111111111" as BitArray) // -1
@inlinable
public init(_ source: BitArray) {
guard let value = Self(exactly: source) else {
fatalError("""
BitArray value cannot be converted to \(Self.self) because it is \
outside the representable range
""")
}
self = value
}
}
extension BitArray {
@usableFromInline
internal func _foreachTwosComplementWordDownward(
isSigned: Bool,
body: (Int, UInt) -> Bool
) -> Bool {
self._read {
guard $0._words.count > 0 else { return false }
var isNegative = false
let end = $0.end.endSplit
assert(end.bit > 0)
let last = $0._words[end.word]
if isSigned, last.contains(end.bit - 1) {
// Sign extend last word
isNegative = true
if !body(end.word, last.union(_Word(upTo: end.bit).complement()).value) {
return isNegative
}
} else if !body(end.word, last.value) {
return isNegative
}
for i in stride(from: end.word - 1, through: 0, by: -1) {
if !body(i, $0._words[i].value) { return isNegative }
}
return isNegative
}
}
}
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