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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2021-2022 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
//
//===----------------------------------------------------------------------===//
struct FixedPatternConsumer<Consumed: Collection, Pattern: Sequence>
where Consumed.Element: Equatable, Pattern.Element == Consumed.Element
{
let pattern: Pattern
}
extension FixedPatternConsumer: CollectionConsumer {
func consuming(
_ consumed: Consumed,
in range: Range<Consumed.Index>
) -> Consumed.Index? {
var index = range.lowerBound
var patternIterator = pattern.makeIterator()
while let element = patternIterator.next() {
if index == range.upperBound || consumed[index] != element {
return nil
}
consumed.formIndex(after: &index)
}
return index
}
}
extension FixedPatternConsumer: BidirectionalCollectionConsumer
where Consumed: BidirectionalCollection, Pattern: BidirectionalCollection
{
func consumingBack(
_ consumed: Consumed,
in range: Range<Consumed.Index>
) -> Consumed.Index? {
var index = range.upperBound
var patternIndex = pattern.endIndex
while true {
if patternIndex == pattern.startIndex {
return index
}
if index == range.lowerBound {
return nil
}
consumed.formIndex(before: &index)
pattern.formIndex(before: &patternIndex)
if consumed[index] != pattern[patternIndex] {
return nil
}
}
}
}
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