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//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 2023 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 String {
struct _BlockSearchingOptions : OptionSet {
let rawValue: Int
static let findStart = Self(rawValue: 1 << 0)
static let findEnd = Self(rawValue: 1 << 1)
static let findContentsEnd = Self(rawValue: 1 << 2)
static let stopAtLineSeparators = Self(rawValue: 1 << 3)
}
static let paragraphSeparators : [[UTF8.CodeUnit]] = [
[0xE2, 0x80, 0xA9] // U+2029 Paragraph Separator
]
static let lineSeparators : [[UTF8.CodeUnit]] = paragraphSeparators + [
[0xE2, 0x80, 0xA8], // U+2028 Line Separator
[0xC2, 0x85] // U+0085 <Next Line> (NEL)
]
}
struct _StringBlock<Index> {
let start: Index?
let end: Index?
let contentsEnd: Index?
}
extension BidirectionalCollection where Element == UTF8.CodeUnit {
// Returns the index range the separator if a match is found. This always rewinds the start index to that of "\r" in the case where "\r\n" is present.
private func _matchesSeparators(_ separators: [[UTF8.CodeUnit]], from start: Index, reverse: Bool = false) -> Range<Index>? {
let startingCharacter = self[start]
// Special case when startingCharacter is "\r" or "\n" in "\r\n"
if startingCharacter == .carriageReturn {
let next = index(after: start)
if next < endIndex && self[next] == .newline {
return start..<index(after: next)
} else {
return start..<index(after: start)
}
} else if startingCharacter == .newline {
if start > startIndex {
let idxBefore = index(before: start)
if self[idxBefore] == .carriageReturn {
return idxBefore..<index(after: start)
} else {
return start..<index(after: start)
}
} else {
return start..<index(after: start)
}
}
if reverse {
if startingCharacter < 0x85 || startingCharacter > 0xA9 {
return nil
}
} else {
if startingCharacter < 0xC2 || startingCharacter > 0xE2 {
return nil
}
}
for separator in separators {
var strIdx = start
var separatorIdx = reverse ? separator.count - 1 : 0
let offset = reverse ? -1 : 1
let strLimit = reverse ? startIndex : index(before: endIndex)
let sepLimit = reverse ? 0 : separator.count - 1
while separator[separatorIdx] == self[strIdx] {
if !separator.formIndex(&separatorIdx, offsetBy: offset, limitedBy: sepLimit) {
// We've fully matched the separator, return the appropriate range
return (reverse ? strIdx ... start : start ... strIdx).relative(to: self)
}
if !formIndex(&strIdx, offsetBy: offset, limitedBy: strLimit) {
// We've run off the end of the string and haven't finished the separator, break out
break
}
}
}
return nil
}
// Based on -[NSString _getBlockStart:end:contentsEnd:forRange:]
func _getBlock(
for options: String._BlockSearchingOptions,
in inputRangeExpr: some RangeExpression<Index>
) -> _StringBlock<Index> {
let range = inputRangeExpr.relative(to: self)
return _getBlock(for: options, in: range)
}
func _getBlock(
for options: String._BlockSearchingOptions,
in range: Range<Index>
) -> _StringBlock<Index> {
let fullStringRange = startIndex ..< endIndex
guard !(range == fullStringRange && !options.contains(.findContentsEnd)) else {
return _StringBlock(start: startIndex, end: endIndex, contentsEnd: nil)
}
guard range.lowerBound >= startIndex && range.upperBound <= endIndex else {
return _StringBlock(start: startIndex, end: endIndex, contentsEnd: endIndex)
}
let separatorCharacters = options.contains(.stopAtLineSeparators) ? String.lineSeparators : String.paragraphSeparators
var start: Index? = nil
if options.contains(.findStart) {
if range.lowerBound == startIndex {
start = startIndex
} else {
var idx = index(before: range.lowerBound)
// Special case where start is between \r and \n
if range.lowerBound < endIndex && self[range.lowerBound] == .newline && self[idx] == .carriageReturn {
if idx > startIndex {
idx = index(before: idx)
} else {
start = startIndex
}
}
while start == nil, idx >= startIndex, idx < endIndex {
if let _ = _matchesSeparators(separatorCharacters, from: idx, reverse: true) {
start = index(after: idx)
break
}
if idx > startIndex {
idx = index(before: idx)
} else {
start = startIndex
break
}
}
if start == nil {
start = idx
}
}
}
var end: Index? = nil
var contentsEnd: Index? = nil
if options.contains(.findEnd) || options.contains(.findContentsEnd) {
var idx = range.upperBound
if !range.isEmpty {
idx = index(before: idx)
}
if idx < endIndex, let separatorR = _matchesSeparators(separatorCharacters, from: idx, reverse: true) {
// When range.upperBound falls on the end of a multi-code-unit separator, walk backwards to find the start of the separator
end = separatorR.upperBound
contentsEnd = separatorR.lowerBound
} else {
while idx < endIndex {
if let separatorR = _matchesSeparators(separatorCharacters, from: idx) {
contentsEnd = separatorR.lowerBound
end = separatorR.upperBound
break
}
idx = index(after: idx)
}
if idx == endIndex {
contentsEnd = idx
end = idx
}
}
}
return _StringBlock(start: start, end: end, contentsEnd: contentsEnd)
}
}
extension Substring.UTF8View {
// Note: we could have these defined on BidirectionalCollection<UInt8>, like _getBlock.
// However, all current call sites are funneling through Substring.UTF8View, and it makes
// sense to avoid dealing with generics unless we're forced to. Feel free to convert these
// utilities to generic functions if needed.
internal func _lineBounds(
around range: Range<Index>
) -> (start: Index, end: Index, contentsEnd: Index) {
let result = _getBlock(
for: [.findStart, .findEnd, .findContentsEnd, .stopAtLineSeparators], in: range)
return (result.start!, result.end!, result.contentsEnd!)
}
internal func _paragraphBounds(
around range: Range<Index>
) -> (start: Index, end: Index, contentsEnd: Index) {
let result = _getBlock(
for: [.findStart, .findEnd, .findContentsEnd], in: range)
return (result.start!, result.end!, result.contentsEnd!)
}
}
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