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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
//
//===----------------------------------------------------------------------===//
#if swift(>=5.8)
@available(macOS 13.3, iOS 16.4, watchOS 9.4, tvOS 16.4, *)
extension BigString {
func _ingester(
forInserting input: __owned Substring,
at index: Index,
allowForwardPeek: Bool
) -> _Ingester {
let hint = allowForwardPeek ? input.unicodeScalars.first : nil
let state = self._breakState(upTo: index, nextScalarHint: hint)
return _Ingester(input, startState: state)
}
}
@available(macOS 13.3, iOS 16.4, watchOS 9.4, tvOS 16.4, *)
extension BigString {
internal struct _Ingester {
typealias _Chunk = BigString._Chunk
typealias Counts = BigString._Chunk.Counts
var input: Substring
/// The index of the beginning of the next chunk.
var start: String.Index
/// Grapheme breaking state at the start of the next chunk.
var state: _CharacterRecognizer
init(_ input: Substring) {
self.input = input
self.start = input.startIndex
self.state = _CharacterRecognizer()
}
init(_ input: Substring, startState: __owned _CharacterRecognizer) {
self.input = input
self.start = input.startIndex
self.state = startState
}
init(_ input: String) {
self.init(input[...])
}
init<S: StringProtocol>(_ input: S) {
self.init(Substring(input))
}
var isAtEnd: Bool {
start == input.endIndex
}
var remainingUTF8: Int {
input.utf8.distance(from: start, to: input.endIndex)
}
mutating func nextSlice(
maxUTF8Count: Int = _Chunk.maxUTF8Count
) -> _Chunk.Slice? {
guard let range = input.base._nextSlice(
after: start, limit: input.endIndex, maxUTF8Count: maxUTF8Count)
else {
assert(start == input.endIndex)
return nil
}
if range.isEmpty {
return nil // Not enough room.
}
assert(range.lowerBound == start && range.upperBound <= input.endIndex)
start = range.upperBound
var s = input[range]
let c8 = s.utf8.count
guard let r = state.firstBreak(in: s) else {
// Anomalous case -- chunk is entirely a continuation of a single character.
return (
string: s,
characters: 0,
prefix: c8,
suffix: c8)
}
let first = r.lowerBound
s = s.suffix(from: r.upperBound)
var characterCount = 1
var last = first
while let r = state.firstBreak(in: s) {
last = r.lowerBound
s = s.suffix(from: r.upperBound)
characterCount += 1
}
let prefixCount = input.utf8.distance(from: range.lowerBound, to: first)
let suffixCount = input.utf8.distance(from: last, to: range.upperBound)
return (
string: input[range],
characters: characterCount,
prefix: prefixCount,
suffix: suffixCount)
}
mutating func nextChunk(maxUTF8Count: Int = _Chunk.maxUTF8Count) -> _Chunk? {
guard let slice = nextSlice(maxUTF8Count: maxUTF8Count) else { return nil }
return _Chunk(slice)
}
static func desiredNextChunkSize(remaining: Int) -> Int {
if remaining <= _Chunk.maxUTF8Count {
return remaining
}
if remaining >= _Chunk.maxUTF8Count + _Chunk.minUTF8Count {
return _Chunk.maxUTF8Count
}
return remaining - _Chunk.minUTF8Count
}
mutating func nextWellSizedSlice(suffix: Int = 0) -> _Chunk.Slice? {
let desired = Self.desiredNextChunkSize(remaining: remainingUTF8 + suffix)
return nextSlice(maxUTF8Count: desired)
}
mutating func nextWellSizedChunk(suffix: Int = 0) -> _Chunk? {
guard let slice = nextWellSizedSlice(suffix: suffix) else { return nil }
return _Chunk(slice)
}
}
}
@available(macOS 13.3, iOS 16.4, watchOS 9.4, tvOS 16.4, *)
extension String {
func _nextSlice(
after i: Index,
limit: Index,
maxUTF8Count: Int
) -> Range<Index>? {
assert(maxUTF8Count >= 0)
assert(i._isKnownScalarAligned)
guard i < limit else { return nil }
let end = self.utf8.index(i, offsetBy: maxUTF8Count, limitedBy: limit) ?? limit
let j = self.unicodeScalars._index(roundingDown: end)
return Range(uncheckedBounds: (i, j))
}
}
@available(macOS 13.3, iOS 16.4, watchOS 9.4, tvOS 16.4, *)
extension BigString._Chunk {
init(_ string: String) {
guard !string.isEmpty else { self.init(); return }
assert(string.utf8.count <= Self.maxUTF8Count)
var ingester = BigString._Ingester(string)
self = ingester.nextChunk()!
assert(ingester.isAtEnd)
}
}
#endif
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