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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift Collections open source project
//
// Copyright (c) 2023 - 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: LosslessStringConvertible {
/// Initializes a new bit array from a string representation.
///
/// The string given is interpreted as if it was the binary representation
/// of an integer value, consisting of the digits `0` and `1`, with the
/// highest digits appearing first.
///
/// BitArray("") // []
/// BitArray("001") // [true, false, false]
/// BitArray("1110") // [false, true, true, true]
/// BitArray("42") // nil
/// BitArray("Foo") // nil
///
/// To accept the display format used by `description`, the digits in the
/// input string are also allowed to be surrounded by a single pair of ASCII
/// angle brackets:
///
/// let bits: BitArray = [false, false, true, true]
/// let string = bits.description // "<1100>"
/// let sameBits = BitArray(string)! // [false, false, true, true]
///
public init?(_ description: String) {
var digits = description[...]
if digits.utf8.first == ._asciiLT, digits.utf8.last == ._asciiGT {
digits = digits.dropFirst().dropLast()
}
let bits: BitArray? = digits.utf8.withContiguousStorageIfAvailable { buffer in
Self(_utf8Digits: buffer)
} ?? Self(_utf8Digits: description.utf8)
guard let bits = bits else {
return nil
}
self = bits
}
internal init?(_utf8Digits utf8: some Collection<UInt8>) {
let c = utf8.count
self.init(repeating: false, count: c)
var i = c &- 1
let success = _update { handle in
for byte in utf8 {
if byte == ._ascii1 {
handle.set(at: i)
} else {
guard byte == ._ascii0 else { return false }
}
i &-= 1
}
return true
}
guard success else { return nil }
}
}
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