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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
//
//===----------------------------------------------------------------------===//
// MARK: - Element Consumer
/// An alternate formation of consumers: Don't bind collection type as we're just
/// consuming elements by classification or literal sequencing.
protocol ElementConsumer {
associatedtype Element
func consume<C: Collection>(
_ c: C, in: Range<C.Index>
) -> C.Index? where C.Element == Element
}
protocol CharacterConsumer: ElementConsumer
where Element == Character { }
protocol ScalarConsumer: ElementConsumer
where Element == Unicode.Scalar { }
protocol UTF8Consumer: ElementConsumer
where Element == UInt8 { }
protocol UTF16Consumer: ElementConsumer
where Element == UInt16 { }
// struct ...LiteralSequence: ...Consumer { ... }
// MARK: - Element Classes
protocol ElementClass: ElementConsumer {
func contains(_ e: Element) -> Bool
}
extension ElementClass {
func consume<C: Collection>(
_ c: C, in range: Range<C.Index>
) -> C.Index? where C.Element == Element {
// FIXME: empty ranges, etc...
let lower = range.lowerBound
return contains(c[lower]) ? c.index(after: lower) : nil
}
}
protocol ScalarClass: ElementClass, ScalarConsumer {}
protocol CharacterClass: ElementClass, CharacterConsumer {}
// MARK: Granularity adapters
/// Any higher-granularity consumer can be a lower-granularity
/// consumer by just consuming at its higher-granularity
struct _CharacterToScalar <
Characters: CharacterConsumer
>: ScalarConsumer {
var characters: Characters
func consume<C: Collection>(
_ c: C, in range: Range<C.Index>
) -> C.Index? where C.Element == Unicode.Scalar {
let str = String(c)
let r = c.convertByOffset(range, in: str)
guard let idx = characters.consume(str, in: r) else {
return nil
}
return str.convertByOffset(idx, in: c)
}
}
// ...
/// Any lower-granularity consumer can be a higher
/// granularity consumer by checking if the result falls on a
/// boundary.
struct _ScalarToCharacter <
Scalars: ScalarConsumer
>: CharacterConsumer {
var scalars: Scalars
func _consume(
_ str: String, in range: Range<String.Index>
) -> String.Index? {
guard let idx = scalars.consume(str.unicodeScalars, in: range),
str.isOnGraphemeClusterBoundary(idx)
else {
return nil
}
return idx
}
func consume<C: Collection>(
_ c: C, in range: Range<C.Index>
) -> C.Index? where C.Element == Character {
let str = String(c)
let r = c.convertByOffset(range, in: str)
guard let idx = _consume(str, in: r) else {
return nil
}
return str.convertByOffset(idx, in: c)
}
}
/// Any lower-granularity class can be a higher-granularity
/// class if we choose a semantic-extension style
struct _FirstScalarCharacters<
Scalars: ScalarClass
>: CharacterClass {
var scalars: Scalars
func contains(_ c: Character) -> Bool {
scalars.contains(c.unicodeScalars.first!)
}
}
struct _SingleScalarCharacters<
Scalars: ScalarClass
>: CharacterClass {
var scalars: Scalars
func contains(_ c: Character) -> Bool {
let scs = c.unicodeScalars
return scs.count == 1 && scalars.contains(scs.first!)
}
// NOTE: This would be equivalent to _ScalarToCharacter
// for any scalar consumer that consumes only one scalar
// at a time.
}
struct _AllScalarCharacters<
Scalars: ScalarClass
>: CharacterClass {
var scalars: Scalars
func contains(_ c: Character) -> Bool {
c.unicodeScalars.allSatisfy(scalars.contains)
}
}
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