Foundation/NSIndexSet.swift - third_party/swift-corelibs-foundation - Git at Google

 // This source file is part of the Swift.org open source project
 //
 // Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See http://swift.org/LICENSE.txt for license information
 // See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 //


 /* Class for managing set of indexes. The set of valid indexes are 0 .. NSNotFound - 1; trying to use indexes outside this range is an error.  NSIndexSet uses NSNotFound as a return value in cases where the queried index doesn't exist in the set; for instance, when you ask firstIndex and there are no indexes; or when you ask for indexGreaterThanIndex: on the last index, and so on.

 The following code snippets can be used to enumerate over the indexes in an NSIndexSet:

     // Forward
     var currentIndex = set.firstIndex
     while currentIndex != NSNotFound {
         ...
         currentIndex = set.indexGreaterThanIndex(currentIndex)
     }

     // Backward
     var currentIndex = set.lastIndex
     while currentIndex != NSNotFound {
         ...
         currentIndex = set.indexLessThanIndex(currentIndex)
     }

 To enumerate without doing a call per index, you can use the method getIndexes:maxCount:inIndexRange:.
 */

 internal func __NSIndexSetRangeCount(_ indexSet: NSIndexSet) -> UInt {
     return UInt(indexSet._ranges.count)
 }

 internal func __NSIndexSetRangeAtIndex(_ indexSet: NSIndexSet, _ index: UInt, _ location : UnsafeMutablePointer<UInt>, _ length : UnsafeMutablePointer<UInt>) {
 //    if Int(index) >= indexSet._ranges.count {
 //        location.pointee = UInt(bitPattern: NSNotFound)
 //        length.pointee = UInt(0)
 //        return
 //    }
     let range = indexSet._ranges[Int(index)]
     location.pointee = UInt(range.location)
     length.pointee = UInt(range.length)
 }

 internal func __NSIndexSetIndexOfRangeContainingIndex(_ indexSet: NSIndexSet, _ index: UInt) -> UInt {
     var idx = 0
     while idx < indexSet._ranges.count {
         let range = indexSet._ranges[idx]
         if range.location <= Int(index) && Int(index) <= range.location + range.length {
             return UInt(idx)
         }
         idx += 1
     }
     return UInt(bitPattern: NSNotFound)
 }

 open class NSIndexSet : NSObject, NSCopying, NSMutableCopying, NSSecureCoding {
     // all instance variables are private

     internal var _ranges = [NSRange]()
     internal var _count = 0
     override public init() {
         _count = 0
         _ranges = []
     }
     public init(indexesIn range: NSRange) {
         _count = range.length
         _ranges = _count == 0 ? [] : [range]
     }
     public init(indexSet: IndexSet) {
         _ranges = indexSet.rangeView.map { NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound) }
         _count = indexSet.count
     }

     open override func copy() -> Any {
         return copy(with: nil)
     }

     open func copy(with zone: NSZone? = nil) -> Any {
         if type(of: self) === NSIndexSet.self {
             // return self for immutable type
             return self
         }
         return NSIndexSet(indexSet: self._bridgeToSwift())
     }

     open override func mutableCopy() -> Any {
         return mutableCopy(with: nil)
     }

     open func mutableCopy(with zone: NSZone? = nil) -> Any {
         let set = NSMutableIndexSet()
         enumerateRanges(options: []) {
             set.add(in: $0.0)
         }
         return set
     }

     public static var supportsSecureCoding: Bool { return true }

     public required init?(coder aDecoder: NSCoder)  { NSUnimplemented() }
     open func encode(with aCoder: NSCoder) {
         NSUnimplemented()
     }

     public convenience init(index value: Int) {
         self.init(indexesIn: NSMakeRange(value, 1))
     }

     open func isEqual(to indexSet: IndexSet) -> Bool {

         let otherRanges = indexSet.rangeView.map { NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound) }
         if _ranges.count != otherRanges.count {
             return false
         }
         for (r1, r2) in zip(_ranges, otherRanges) {
             if r1.length != r2.length || r1.location != r2.location {
                 return false
             }
         }
         return true
     }

     open var count: Int {
         return _count
     }

     /* The following six methods will return NSNotFound if there is no index in the set satisfying the query.
     */
     open var firstIndex: Int {
         return _ranges.first?.location ?? NSNotFound
     }
     open var lastIndex: Int {
         guard _ranges.count > 0 else {
             return NSNotFound
         }
         return NSMaxRange(_ranges.last!) - 1
     }

     internal func _indexAndRangeAdjacentToOrContainingIndex(_ idx : Int) -> (Int, NSRange)? {
         let count = _ranges.count
         guard count > 0 else {
             return nil
         }

         var min = 0
         var max = count - 1
         while min < max {
             let rIdx = (min + max) / 2
             let range = _ranges[rIdx]
             if range.location > idx {
                 max = rIdx
             } else if NSMaxRange(range) - 1 < idx {
                 min = rIdx + 1
             } else {
                 return (rIdx, range)
             }
         }
         return (min, _ranges[min])
     }

     internal func _indexOfRangeContainingIndex (_ idx : Int) -> Int? {
         if let (rIdx, range) = _indexAndRangeAdjacentToOrContainingIndex(idx) {
             return NSLocationInRange(idx, range) ? rIdx : nil
         } else {
             return nil
         }
     }

     internal func _indexOfRangeBeforeOrContainingIndex(_ idx : Int) -> Int? {
         if let (rIdx, range) = _indexAndRangeAdjacentToOrContainingIndex(idx) {
             if range.location <= idx {
                 return rIdx
             } else if rIdx > 0 {
                 return rIdx - 1
             } else {
                 return nil
             }
         } else {
             return nil
         }
     }

     internal func _indexOfRangeAfterOrContainingIndex(_ idx : Int) -> Int? {
         if let (rIdx, range) = _indexAndRangeAdjacentToOrContainingIndex(idx) {
             if NSMaxRange(range) - 1 >= idx {
                 return rIdx
             } else if rIdx + 1 < _ranges.count {
                 return rIdx + 1
             } else {
                 return nil
             }
         } else {
             return nil
         }
     }

     internal func _indexClosestToIndex(_ idx: Int, equalAllowed : Bool, following: Bool) -> Int? {
         guard _count > 0 else {
             return nil
         }

         if following {
             var result = idx
             if !equalAllowed {
                 guard idx < NSNotFound else {
                     return nil
                 }
                 result += 1
             }

             if let rangeIndex = _indexOfRangeAfterOrContainingIndex(result) {
                 let range = _ranges[rangeIndex]
                 return NSLocationInRange(result, range) ? result : range.location
             }
         } else {
             var result = idx
             if !equalAllowed {
                 guard idx > 0 else {
                     return nil
                 }
                 result -= 1
             }

             if let rangeIndex = _indexOfRangeBeforeOrContainingIndex(result) {
                 let range = _ranges[rangeIndex]
                 return NSLocationInRange(result, range) ? result : (NSMaxRange(range) - 1)
             }
         }
         return nil
     }

     open func indexGreaterThanIndex(_ value: Int) -> Int {
         return _indexClosestToIndex(value, equalAllowed: false, following: true) ?? NSNotFound
     }
     open func indexLessThanIndex(_ value: Int) -> Int {
         return _indexClosestToIndex(value, equalAllowed: false, following: false) ?? NSNotFound
     }
     open func indexGreaterThanOrEqual(to value: Int) -> Int {
         return _indexClosestToIndex(value, equalAllowed: true, following: true) ?? NSNotFound
     }
     open func indexLessThanOrEqual(to value: Int) -> Int {
         return _indexClosestToIndex(value, equalAllowed: true, following: false) ?? NSNotFound
     }

     /* Fills up to bufferSize indexes in the specified range into the buffer and returns the number of indexes actually placed in the buffer; also modifies the optional range passed in by pointer to be "positioned" after the last index filled into the buffer.Example: if the index set contains the indexes 0, 2, 4, ..., 98, 100, for a buffer of size 10 and the range (20, 80) the buffer would contain 20, 22, ..., 38 and the range would be modified to (40, 60).
     */
     open func getIndexes(_ indexBuffer: UnsafeMutablePointer<Int>, maxCount bufferSize: Int, inIndexRange range: NSRangePointer?) -> Int {
         let minIndex : Int
         let maxIndex : Int
         if let initialRange = range {
             minIndex = initialRange.pointee.location
             maxIndex = NSMaxRange(initialRange.pointee) - 1
         } else {
             minIndex = firstIndex
             maxIndex = lastIndex
         }
         guard minIndex <= maxIndex else {
             return 0
         }

         if let initialRangeIndex = self._indexOfRangeAfterOrContainingIndex(minIndex) {
             var rangeIndex = initialRangeIndex
             let rangeCount = _ranges.count
             var counter = 0
             var idx = minIndex
             var offset = 0
             while rangeIndex < rangeCount && idx <= maxIndex && counter < bufferSize {
                 let currentRange = _ranges[rangeIndex]
                 if currentRange.location <= minIndex {
                     idx = minIndex
                     offset = minIndex - currentRange.location
                 } else {
                     idx = currentRange.location
                 }

                 while idx <= maxIndex && counter < bufferSize && offset < currentRange.length {
                     indexBuffer.advanced(by: counter).pointee = idx
                     counter += 1
                     idx += 1
                     offset += 1
                 }
                 if offset >= currentRange.length {
                     rangeIndex += 1
                     offset = 0
                 }
             }

             if counter > 0, let resultRange = range {
                 let delta = indexBuffer.advanced(by: counter - 1).pointee - minIndex + 1
                 resultRange.pointee.location += delta
                 resultRange.pointee.length -= delta
             }
             return counter
         } else {
             return 0
         }
     }

     open func countOfIndexes(in range: NSRange) -> Int {
         guard _count > 0 && range.length > 0 else {
             return 0
         }

         if let initialRangeIndex = self._indexOfRangeAfterOrContainingIndex(range.location) {
             var rangeIndex = initialRangeIndex
             let maxRangeIndex = NSMaxRange(range) - 1

             var result = 0
             let firstRange = _ranges[rangeIndex]
             if firstRange.location < range.location {
                 if NSMaxRange(firstRange) - 1 >= maxRangeIndex {
                     return range.length
                 }
                 result = NSMaxRange(firstRange) - range.location
                 rangeIndex += 1
             }

             for curRange in _ranges.suffix(from: rangeIndex) {
                 if NSMaxRange(curRange) - 1 > maxRangeIndex {
                     if curRange.location <= maxRangeIndex {
                         result += maxRangeIndex + 1 - curRange.location
                     }
                     break
                 }
                 result += curRange.length
             }
             return result
         } else {
             return 0
         }
     }

     open func contains(_ value: Int) -> Bool {
         return _indexOfRangeContainingIndex(value) != nil
     }
     open func contains(in range: NSRange) -> Bool {
         guard range.length > 0 else {
             return false
         }
         if let rIdx = self._indexOfRangeContainingIndex(range.location) {
             return NSMaxRange(_ranges[rIdx]) >= NSMaxRange(range)
         } else {
             return false
         }
     }
     open func contains(_ indexSet: IndexSet) -> Bool {
         var result = true
         enumerateRanges(options: []) { range, stop in
             if !self.contains(in: range) {
                 result = false
                 stop.pointee = true
             }
         }
         return result
     }

     open func intersects(in range: NSRange) -> Bool {
         guard range.length > 0 else {
             return false
         }

         if let rIdx = _indexOfRangeBeforeOrContainingIndex(range.location) {
             if NSMaxRange(_ranges[rIdx]) - 1 >= range.location {
                 return true
             }
         }
         if let rIdx = _indexOfRangeAfterOrContainingIndex(range.location) {
             if NSMaxRange(range) - 1 >= _ranges[rIdx].location {
                 return true
             }
         }
         return false
     }

     internal func _enumerateWithOptions<P, R>(_ opts : NSEnumerationOptions, range: NSRange, paramType: P.Type, returnType: R.Type, block: (P, UnsafeMutablePointer<ObjCBool>) -> R) -> Int? {
         guard !opts.contains(.concurrent) else {
             NSUnimplemented()
         }

         guard let startRangeIndex = self._indexOfRangeAfterOrContainingIndex(range.location), let endRangeIndex = _indexOfRangeBeforeOrContainingIndex(NSMaxRange(range) - 1) else {
             return nil
         }

         var result : Int? = nil
         let reverse = opts.contains(.reverse)
         let passRanges = paramType == NSRange.self
         let findIndex = returnType == Bool.self
         var stop = false
         let ranges = _ranges[startRangeIndex...endRangeIndex]
         let rangeSequence = (reverse ? AnySequence(ranges.reversed()) : AnySequence(ranges))
         outer: for curRange in rangeSequence {
             let intersection = NSIntersectionRange(curRange, range)
             if passRanges {
                 if intersection.length > 0 {
                     let _ = block(intersection as! P, &stop)
                 }
                 if stop {
                     break outer
                 }
             } else if intersection.length > 0 {
                 let maxIndex = NSMaxRange(intersection) - 1
                 let indexes = reverse ? stride(from: maxIndex, through: intersection.location, by: -1) : stride(from: intersection.location, through: maxIndex, by: 1)
                 for idx in indexes {
                     if findIndex {
                         let found : Bool = block(idx as! P, &stop) as! Bool
                         if found {
                             result = idx
                             stop = true
                         }
                     } else {
                         let _ = block(idx as! P, &stop)
                     }
                     if stop {
                         break outer
                     }
                 }
             } // else, continue
         }

         return result
     }

     open func enumerate(_ block: (Int, UnsafeMutablePointer<ObjCBool>) -> Void) {
         enumerate(options: [], using: block)
     }
     open func enumerate(options opts: NSEnumerationOptions = [], using block: (Int, UnsafeMutablePointer<ObjCBool>) -> Void) {
         let _ = _enumerateWithOptions(opts, range: NSMakeRange(0, Int.max), paramType: Int.self, returnType: Void.self, block: block)
     }
     open func enumerate(in range: NSRange, options opts: NSEnumerationOptions = [], using block: (Int, UnsafeMutablePointer<ObjCBool>) -> Void) {
         let _ = _enumerateWithOptions(opts, range: range, paramType: Int.self, returnType: Void.self, block: block)
     }

     open func index(passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> Int {
         return index(options: [], passingTest: predicate)
     }
     open func index(options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> Int {
         return _enumerateWithOptions(opts, range: NSMakeRange(0, Int.max), paramType: Int.self, returnType: Bool.self, block: predicate) ?? NSNotFound
     }
     open func index(in range: NSRange, options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> Int {
         return _enumerateWithOptions(opts, range: range, paramType: Int.self, returnType: Bool.self, block: predicate) ?? NSNotFound
     }

     open func indexes(passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> IndexSet {
         return indexes(in: NSMakeRange(0, Int.max), options: [], passingTest: predicate)
     }
     open func indexes(options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> IndexSet {
         return indexes(in: NSMakeRange(0, Int.max), options: opts, passingTest: predicate)
     }
     open func indexes(in range: NSRange, options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> IndexSet {
         var result = IndexSet()
         let _ = _enumerateWithOptions(opts, range: range, paramType: Int.self, returnType: Void.self) { idx, stop in
             if predicate(idx, stop) {
                 result.insert(idx)
             }
         }
         return result
     }

     /*
      The following three convenience methods allow you to enumerate the indexes in the receiver by ranges of contiguous indexes. The performance of these methods is not guaranteed to be any better than if they were implemented with enumerateIndexesInRange:options:usingBlock:. However, depending on the receiver's implementation, they may perform better than that.

      If the specified range for enumeration intersects a range of contiguous indexes in the receiver, then the block will be invoked with the intersection of those two ranges.
     */
     open func enumerateRanges(_ block: (NSRange, UnsafeMutablePointer<ObjCBool>) -> Void) {
         enumerateRanges(options: [], using: block)
     }
     open func enumerateRanges(options opts: NSEnumerationOptions = [], using block: (NSRange, UnsafeMutablePointer<ObjCBool>) -> Void) {
         let _ = _enumerateWithOptions(opts, range: NSMakeRange(0, Int.max), paramType: NSRange.self, returnType: Void.self, block: block)
     }
     open func enumerateRanges(in range: NSRange, options opts: NSEnumerationOptions = [], using block: (NSRange, UnsafeMutablePointer<ObjCBool>) -> Void) {
         let _ = _enumerateWithOptions(opts, range: range, paramType: NSRange.self, returnType: Void.self, block: block)
     }
 }

 public struct NSIndexSetIterator : IteratorProtocol {
     public typealias Element = Int
     internal let _set: NSIndexSet
     internal var _first: Bool = true
     internal var _current: Element?

     internal init(_ set: NSIndexSet) {
         self._set = set
         self._current = nil
     }

     public mutating func next() -> Element? {
         if _first {
             _current = _set.firstIndex
             _first = false
         } else if let c = _current {
             _current = _set.indexGreaterThanIndex(c)
         }
         if _current == NSNotFound {
             _current = nil
         }
         return _current
     }
 }

 extension NSIndexSet : Sequence {
     public func makeIterator() -> NSIndexSetIterator {
         return NSIndexSetIterator(self)
     }
 }

 open class NSMutableIndexSet : NSIndexSet {

     open func add(_ indexSet: IndexSet) {
         indexSet.rangeView.forEach { add(in: NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound)) }
     }

     open override func copy(with zone: NSZone? = nil) -> Any {
         if type(of: self) === NSMutableIndexSet.self {
             let indexSet = NSMutableIndexSet()
             indexSet._ranges = self._ranges
             indexSet._count = self._count
             return indexSet
         }
         return NSMutableIndexSet(indexSet: self._bridgeToSwift())
     }

     open func remove(_ indexSet: IndexSet) {
         indexSet.rangeView.forEach { remove(in: NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound)) }
     }

     open func removeAllIndexes() {
         _ranges = []
         _count = 0
     }

     open func add(_ value: Int) {
         add(in: NSMakeRange(value, 1))
     }

     open func remove(_ value: Int) {
         remove(in: NSMakeRange(value, 1))
     }

     internal func _insertRange(_ range: NSRange, atIndex index: Int) {
         _ranges.insert(range, at: index)
         _count += range.length
     }

     internal func _replaceRangeAtIndex(_ index: Int, withRange range: NSRange?) {
         let oldRange = _ranges[index]
         if let range = range {
             _ranges[index] = range
             _count += range.length - oldRange.length
         } else {
             _ranges.remove(at: index)
             _count -= oldRange.length
         }
     }

     internal func _mergeOverlappingRangesStartingAtIndex(_ index: Int) {
         var rangeIndex = index
         while _ranges.count > 0 && rangeIndex < _ranges.count - 1 {
             let curRange = _ranges[rangeIndex]
             let nextRange = _ranges[rangeIndex + 1]
             let curEnd = NSMaxRange(curRange)
             let nextEnd = NSMaxRange(nextRange)
             if curEnd >= nextRange.location {
                 // overlaps
                 if curEnd < nextEnd {
                     self._replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(nextEnd - curRange.location, curRange.length))
                     rangeIndex += 1
                 }
                 self._replaceRangeAtIndex(rangeIndex + 1, withRange: nil)
             } else {
                 break
             }
         }
     }

     open func add(in range: NSRange) {
         guard range.length > 0 else {
             return
         }
         let addEnd = NSMaxRange(range)
         let startRangeIndex = _indexOfRangeBeforeOrContainingIndex(range.location) ?? 0
         var replacedRangeIndex : Int?
         var rangeIndex = startRangeIndex
         while rangeIndex < _ranges.count {
             let curRange = _ranges[rangeIndex]
             let curEnd = NSMaxRange(curRange)
             if addEnd < curRange.location {
                 _insertRange(range, atIndex: rangeIndex)
                 // Done. No need to merge
                 return
             } else if range.location < curRange.location && addEnd >= curRange.location {
                 if addEnd > curEnd {
                     _replaceRangeAtIndex(rangeIndex, withRange: range)
                 } else {
                     _replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(range.location, curEnd - range.location))
                 }
                 replacedRangeIndex = rangeIndex
                 // Proceed to merging
                 break
             } else if range.location >= curRange.location && addEnd < curEnd {
                 // Nothing to add
                 return
             } else if range.location >= curRange.location && range.location <= curEnd && addEnd > curEnd {
                 _replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(curRange.location, addEnd - curRange.location))
                 replacedRangeIndex = rangeIndex
                 // Proceed to merging
                 break
             }
             rangeIndex += 1
         }
         if let r = replacedRangeIndex {
             _mergeOverlappingRangesStartingAtIndex(r)
         } else {
             _insertRange(range, atIndex: _ranges.count)
         }
     }

     open func remove(in range: NSRange) {
         guard range.length > 0 else {
             return
         }
         guard let startRangeIndex = (range.location > 0) ? _indexOfRangeAfterOrContainingIndex(range.location) : 0 else {
             return
         }
         let removeEnd = NSMaxRange(range)
         var rangeIndex = startRangeIndex
         while rangeIndex < _ranges.count {
             let curRange = _ranges[rangeIndex]
             let curEnd = NSMaxRange(curRange)

             if removeEnd < curRange.location {
                 // Nothing to remove
                 return
             } else if range.location <= curRange.location && removeEnd >= curRange.location {
                 if removeEnd >= curEnd {
                     _replaceRangeAtIndex(rangeIndex, withRange: nil)
                     // Don't increment rangeIndex
                     continue
                 } else {
                     self._replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(removeEnd, curEnd - removeEnd))
                     return
                 }
             } else if range.location > curRange.location && removeEnd < curEnd {
                 let firstPiece = NSMakeRange(curRange.location, range.location - curRange.location)
                 let secondPiece = NSMakeRange(removeEnd, curEnd - removeEnd)
                 _replaceRangeAtIndex(rangeIndex, withRange: secondPiece)
                 _insertRange(firstPiece, atIndex: rangeIndex)
             } else if range.location > curRange.location && range.location < curEnd && removeEnd >= curEnd {
                 _replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(curRange.location, range.location - curRange.location))
             }
             rangeIndex += 1
         }

     }

     /* For a positive delta, shifts the indexes in [index, INT_MAX] to the right, thereby inserting an "empty space" [index, delta], for a negative delta, shifts the indexes in [index, INT_MAX] to the left, thereby deleting the indexes in the range [index - delta, delta].
     */
     open func shiftIndexesStarting(at index: Int, by delta: Int) { NSUnimplemented() }
 }

 extension NSIndexSet : _StructTypeBridgeable {
     public typealias _StructType = IndexSet

     public func _bridgeToSwift() -> IndexSet {
         return IndexSet._unconditionallyBridgeFromObjectiveC(self)
     }
 }
	// This source file is part of the Swift.org open source project
	//
	// Copyright (c) 2014 - 2016 Apple Inc. and the Swift project authors
	// Licensed under Apache License v2.0 with Runtime Library Exception
	//
	// See http://swift.org/LICENSE.txt for license information
	// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
	//


	/* Class for managing set of indexes. The set of valid indexes are 0 .. NSNotFound - 1; trying to use indexes outside this range is an error. NSIndexSet uses NSNotFound as a return value in cases where the queried index doesn't exist in the set; for instance, when you ask firstIndex and there are no indexes; or when you ask for indexGreaterThanIndex: on the last index, and so on.

	The following code snippets can be used to enumerate over the indexes in an NSIndexSet:

	// Forward
	var currentIndex = set.firstIndex
	while currentIndex != NSNotFound {
	...
	currentIndex = set.indexGreaterThanIndex(currentIndex)
	}

	// Backward
	var currentIndex = set.lastIndex
	while currentIndex != NSNotFound {
	...
	currentIndex = set.indexLessThanIndex(currentIndex)
	}

	To enumerate without doing a call per index, you can use the method getIndexes:maxCount:inIndexRange:.
	*/

	internal func __NSIndexSetRangeCount(_ indexSet: NSIndexSet) -> UInt {
	return UInt(indexSet._ranges.count)
	}

	internal func __NSIndexSetRangeAtIndex(_ indexSet: NSIndexSet, _ index: UInt, _ location : UnsafeMutablePointer<UInt>, _ length : UnsafeMutablePointer<UInt>) {
	// if Int(index) >= indexSet._ranges.count {
	// location.pointee = UInt(bitPattern: NSNotFound)
	// length.pointee = UInt(0)
	// return
	// }
	let range = indexSet._ranges[Int(index)]
	location.pointee = UInt(range.location)
	length.pointee = UInt(range.length)
	}

	internal func __NSIndexSetIndexOfRangeContainingIndex(_ indexSet: NSIndexSet, _ index: UInt) -> UInt {
	var idx = 0
	while idx < indexSet._ranges.count {
	let range = indexSet._ranges[idx]
	if range.location <= Int(index) && Int(index) <= range.location + range.length {
	return UInt(idx)
	}
	idx += 1
	}
	return UInt(bitPattern: NSNotFound)
	}

	open class NSIndexSet : NSObject, NSCopying, NSMutableCopying, NSSecureCoding {
	// all instance variables are private

	internal var _ranges = [NSRange]()
	internal var _count = 0
	override public init() {
	_count = 0
	_ranges = []
	}
	public init(indexesIn range: NSRange) {
	_count = range.length
	_ranges = _count == 0 ? [] : [range]
	}
	public init(indexSet: IndexSet) {
	_ranges = indexSet.rangeView.map { NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound) }
	_count = indexSet.count
	}

	open override func copy() -> Any {
	return copy(with: nil)
	}

	open func copy(with zone: NSZone? = nil) -> Any {
	if type(of: self) === NSIndexSet.self {
	// return self for immutable type
	return self
	}
	return NSIndexSet(indexSet: self._bridgeToSwift())
	}

	open override func mutableCopy() -> Any {
	return mutableCopy(with: nil)
	}

	open func mutableCopy(with zone: NSZone? = nil) -> Any {
	let set = NSMutableIndexSet()
	enumerateRanges(options: []) {
	set.add(in: $0.0)
	}
	return set
	}

	public static var supportsSecureCoding: Bool { return true }

	public required init?(coder aDecoder: NSCoder) { NSUnimplemented() }
	open func encode(with aCoder: NSCoder) {
	NSUnimplemented()
	}

	public convenience init(index value: Int) {
	self.init(indexesIn: NSMakeRange(value, 1))
	}

	open func isEqual(to indexSet: IndexSet) -> Bool {

	let otherRanges = indexSet.rangeView.map { NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound) }
	if _ranges.count != otherRanges.count {
	return false
	}
	for (r1, r2) in zip(_ranges, otherRanges) {
	if r1.length != r2.length \|\| r1.location != r2.location {
	return false
	}
	}
	return true
	}

	open var count: Int {
	return _count
	}

	/* The following six methods will return NSNotFound if there is no index in the set satisfying the query.
	*/
	open var firstIndex: Int {
	return _ranges.first?.location ?? NSNotFound
	}
	open var lastIndex: Int {
	guard _ranges.count > 0 else {
	return NSNotFound
	}
	return NSMaxRange(_ranges.last!) - 1
	}

	internal func _indexAndRangeAdjacentToOrContainingIndex(_ idx : Int) -> (Int, NSRange)? {
	let count = _ranges.count
	guard count > 0 else {
	return nil
	}

	var min = 0
	var max = count - 1
	while min < max {
	let rIdx = (min + max) / 2
	let range = _ranges[rIdx]
	if range.location > idx {
	max = rIdx
	} else if NSMaxRange(range) - 1 < idx {
	min = rIdx + 1
	} else {
	return (rIdx, range)
	}
	}
	return (min, _ranges[min])
	}

	internal func _indexOfRangeContainingIndex (_ idx : Int) -> Int? {
	if let (rIdx, range) = _indexAndRangeAdjacentToOrContainingIndex(idx) {
	return NSLocationInRange(idx, range) ? rIdx : nil
	} else {
	return nil
	}
	}

	internal func _indexOfRangeBeforeOrContainingIndex(_ idx : Int) -> Int? {
	if let (rIdx, range) = _indexAndRangeAdjacentToOrContainingIndex(idx) {
	if range.location <= idx {
	return rIdx
	} else if rIdx > 0 {
	return rIdx - 1
	} else {
	return nil
	}
	} else {
	return nil
	}
	}

	internal func _indexOfRangeAfterOrContainingIndex(_ idx : Int) -> Int? {
	if let (rIdx, range) = _indexAndRangeAdjacentToOrContainingIndex(idx) {
	if NSMaxRange(range) - 1 >= idx {
	return rIdx
	} else if rIdx + 1 < _ranges.count {
	return rIdx + 1
	} else {
	return nil
	}
	} else {
	return nil
	}
	}

	internal func _indexClosestToIndex(_ idx: Int, equalAllowed : Bool, following: Bool) -> Int? {
	guard _count > 0 else {
	return nil
	}

	if following {
	var result = idx
	if !equalAllowed {
	guard idx < NSNotFound else {
	return nil
	}
	result += 1
	}

	if let rangeIndex = _indexOfRangeAfterOrContainingIndex(result) {
	let range = _ranges[rangeIndex]
	return NSLocationInRange(result, range) ? result : range.location
	}
	} else {
	var result = idx
	if !equalAllowed {
	guard idx > 0 else {
	return nil
	}
	result -= 1
	}

	if let rangeIndex = _indexOfRangeBeforeOrContainingIndex(result) {
	let range = _ranges[rangeIndex]
	return NSLocationInRange(result, range) ? result : (NSMaxRange(range) - 1)
	}
	}
	return nil
	}

	open func indexGreaterThanIndex(_ value: Int) -> Int {
	return _indexClosestToIndex(value, equalAllowed: false, following: true) ?? NSNotFound
	}
	open func indexLessThanIndex(_ value: Int) -> Int {
	return _indexClosestToIndex(value, equalAllowed: false, following: false) ?? NSNotFound
	}
	open func indexGreaterThanOrEqual(to value: Int) -> Int {
	return _indexClosestToIndex(value, equalAllowed: true, following: true) ?? NSNotFound
	}
	open func indexLessThanOrEqual(to value: Int) -> Int {
	return _indexClosestToIndex(value, equalAllowed: true, following: false) ?? NSNotFound
	}

	/* Fills up to bufferSize indexes in the specified range into the buffer and returns the number of indexes actually placed in the buffer; also modifies the optional range passed in by pointer to be "positioned" after the last index filled into the buffer.Example: if the index set contains the indexes 0, 2, 4, ..., 98, 100, for a buffer of size 10 and the range (20, 80) the buffer would contain 20, 22, ..., 38 and the range would be modified to (40, 60).
	*/
	open func getIndexes(_ indexBuffer: UnsafeMutablePointer<Int>, maxCount bufferSize: Int, inIndexRange range: NSRangePointer?) -> Int {
	let minIndex : Int
	let maxIndex : Int
	if let initialRange = range {
	minIndex = initialRange.pointee.location
	maxIndex = NSMaxRange(initialRange.pointee) - 1
	} else {
	minIndex = firstIndex
	maxIndex = lastIndex
	}
	guard minIndex <= maxIndex else {
	return 0
	}

	if let initialRangeIndex = self._indexOfRangeAfterOrContainingIndex(minIndex) {
	var rangeIndex = initialRangeIndex
	let rangeCount = _ranges.count
	var counter = 0
	var idx = minIndex
	var offset = 0
	while rangeIndex < rangeCount && idx <= maxIndex && counter < bufferSize {
	let currentRange = _ranges[rangeIndex]
	if currentRange.location <= minIndex {
	idx = minIndex
	offset = minIndex - currentRange.location
	} else {
	idx = currentRange.location
	}

	while idx <= maxIndex && counter < bufferSize && offset < currentRange.length {
	indexBuffer.advanced(by: counter).pointee = idx
	counter += 1
	idx += 1
	offset += 1
	}
	if offset >= currentRange.length {
	rangeIndex += 1
	offset = 0
	}
	}

	if counter > 0, let resultRange = range {
	let delta = indexBuffer.advanced(by: counter - 1).pointee - minIndex + 1
	resultRange.pointee.location += delta
	resultRange.pointee.length -= delta
	}
	return counter
	} else {
	return 0
	}
	}

	open func countOfIndexes(in range: NSRange) -> Int {
	guard _count > 0 && range.length > 0 else {
	return 0
	}

	if let initialRangeIndex = self._indexOfRangeAfterOrContainingIndex(range.location) {
	var rangeIndex = initialRangeIndex
	let maxRangeIndex = NSMaxRange(range) - 1

	var result = 0
	let firstRange = _ranges[rangeIndex]
	if firstRange.location < range.location {
	if NSMaxRange(firstRange) - 1 >= maxRangeIndex {
	return range.length
	}
	result = NSMaxRange(firstRange) - range.location
	rangeIndex += 1
	}

	for curRange in _ranges.suffix(from: rangeIndex) {
	if NSMaxRange(curRange) - 1 > maxRangeIndex {
	if curRange.location <= maxRangeIndex {
	result += maxRangeIndex + 1 - curRange.location
	}
	break
	}
	result += curRange.length
	}
	return result
	} else {
	return 0
	}
	}

	open func contains(_ value: Int) -> Bool {
	return _indexOfRangeContainingIndex(value) != nil
	}
	open func contains(in range: NSRange) -> Bool {
	guard range.length > 0 else {
	return false
	}
	if let rIdx = self._indexOfRangeContainingIndex(range.location) {
	return NSMaxRange(_ranges[rIdx]) >= NSMaxRange(range)
	} else {
	return false
	}
	}
	open func contains(_ indexSet: IndexSet) -> Bool {
	var result = true
	enumerateRanges(options: []) { range, stop in
	if !self.contains(in: range) {
	result = false
	stop.pointee = true
	}
	}
	return result
	}

	open func intersects(in range: NSRange) -> Bool {
	guard range.length > 0 else {
	return false
	}

	if let rIdx = _indexOfRangeBeforeOrContainingIndex(range.location) {
	if NSMaxRange(_ranges[rIdx]) - 1 >= range.location {
	return true
	}
	}
	if let rIdx = _indexOfRangeAfterOrContainingIndex(range.location) {
	if NSMaxRange(range) - 1 >= _ranges[rIdx].location {
	return true
	}
	}
	return false
	}

	internal func _enumerateWithOptions<P, R>(_ opts : NSEnumerationOptions, range: NSRange, paramType: P.Type, returnType: R.Type, block: (P, UnsafeMutablePointer<ObjCBool>) -> R) -> Int? {
	guard !opts.contains(.concurrent) else {
	NSUnimplemented()
	}

	guard let startRangeIndex = self._indexOfRangeAfterOrContainingIndex(range.location), let endRangeIndex = _indexOfRangeBeforeOrContainingIndex(NSMaxRange(range) - 1) else {
	return nil
	}

	var result : Int? = nil
	let reverse = opts.contains(.reverse)
	let passRanges = paramType == NSRange.self
	let findIndex = returnType == Bool.self
	var stop = false
	let ranges = _ranges[startRangeIndex...endRangeIndex]
	let rangeSequence = (reverse ? AnySequence(ranges.reversed()) : AnySequence(ranges))
	outer: for curRange in rangeSequence {
	let intersection = NSIntersectionRange(curRange, range)
	if passRanges {
	if intersection.length > 0 {
	let _ = block(intersection as! P, &stop)
	}
	if stop {
	break outer
	}
	} else if intersection.length > 0 {
	let maxIndex = NSMaxRange(intersection) - 1
	let indexes = reverse ? stride(from: maxIndex, through: intersection.location, by: -1) : stride(from: intersection.location, through: maxIndex, by: 1)
	for idx in indexes {
	if findIndex {
	let found : Bool = block(idx as! P, &stop) as! Bool
	if found {
	result = idx
	stop = true
	}
	} else {
	let _ = block(idx as! P, &stop)
	}
	if stop {
	break outer
	}
	}
	} // else, continue
	}

	return result
	}

	open func enumerate(_ block: (Int, UnsafeMutablePointer<ObjCBool>) -> Void) {
	enumerate(options: [], using: block)
	}
	open func enumerate(options opts: NSEnumerationOptions = [], using block: (Int, UnsafeMutablePointer<ObjCBool>) -> Void) {
	let _ = _enumerateWithOptions(opts, range: NSMakeRange(0, Int.max), paramType: Int.self, returnType: Void.self, block: block)
	}
	open func enumerate(in range: NSRange, options opts: NSEnumerationOptions = [], using block: (Int, UnsafeMutablePointer<ObjCBool>) -> Void) {
	let _ = _enumerateWithOptions(opts, range: range, paramType: Int.self, returnType: Void.self, block: block)
	}

	open func index(passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> Int {
	return index(options: [], passingTest: predicate)
	}
	open func index(options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> Int {
	return _enumerateWithOptions(opts, range: NSMakeRange(0, Int.max), paramType: Int.self, returnType: Bool.self, block: predicate) ?? NSNotFound
	}
	open func index(in range: NSRange, options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> Int {
	return _enumerateWithOptions(opts, range: range, paramType: Int.self, returnType: Bool.self, block: predicate) ?? NSNotFound
	}

	open func indexes(passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> IndexSet {
	return indexes(in: NSMakeRange(0, Int.max), options: [], passingTest: predicate)
	}
	open func indexes(options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> IndexSet {
	return indexes(in: NSMakeRange(0, Int.max), options: opts, passingTest: predicate)
	}
	open func indexes(in range: NSRange, options opts: NSEnumerationOptions = [], passingTest predicate: (Int, UnsafeMutablePointer<ObjCBool>) -> Bool) -> IndexSet {
	var result = IndexSet()
	let _ = _enumerateWithOptions(opts, range: range, paramType: Int.self, returnType: Void.self) { idx, stop in
	if predicate(idx, stop) {
	result.insert(idx)
	}
	}
	return result
	}

	/*
	The following three convenience methods allow you to enumerate the indexes in the receiver by ranges of contiguous indexes. The performance of these methods is not guaranteed to be any better than if they were implemented with enumerateIndexesInRange:options:usingBlock:. However, depending on the receiver's implementation, they may perform better than that.

	If the specified range for enumeration intersects a range of contiguous indexes in the receiver, then the block will be invoked with the intersection of those two ranges.
	*/
	open func enumerateRanges(_ block: (NSRange, UnsafeMutablePointer<ObjCBool>) -> Void) {
	enumerateRanges(options: [], using: block)
	}
	open func enumerateRanges(options opts: NSEnumerationOptions = [], using block: (NSRange, UnsafeMutablePointer<ObjCBool>) -> Void) {
	let _ = _enumerateWithOptions(opts, range: NSMakeRange(0, Int.max), paramType: NSRange.self, returnType: Void.self, block: block)
	}
	open func enumerateRanges(in range: NSRange, options opts: NSEnumerationOptions = [], using block: (NSRange, UnsafeMutablePointer<ObjCBool>) -> Void) {
	let _ = _enumerateWithOptions(opts, range: range, paramType: NSRange.self, returnType: Void.self, block: block)
	}
	}

	public struct NSIndexSetIterator : IteratorProtocol {
	public typealias Element = Int
	internal let _set: NSIndexSet
	internal var _first: Bool = true
	internal var _current: Element?

	internal init(_ set: NSIndexSet) {
	self._set = set
	self._current = nil
	}

	public mutating func next() -> Element? {
	if _first {
	_current = _set.firstIndex
	_first = false
	} else if let c = _current {
	_current = _set.indexGreaterThanIndex(c)
	}
	if _current == NSNotFound {
	_current = nil
	}
	return _current
	}
	}

	extension NSIndexSet : Sequence {
	public func makeIterator() -> NSIndexSetIterator {
	return NSIndexSetIterator(self)
	}
	}

	open class NSMutableIndexSet : NSIndexSet {

	open func add(_ indexSet: IndexSet) {
	indexSet.rangeView.forEach { add(in: NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound)) }
	}

	open override func copy(with zone: NSZone? = nil) -> Any {
	if type(of: self) === NSMutableIndexSet.self {
	let indexSet = NSMutableIndexSet()
	indexSet._ranges = self._ranges
	indexSet._count = self._count
	return indexSet
	}
	return NSMutableIndexSet(indexSet: self._bridgeToSwift())
	}

	open func remove(_ indexSet: IndexSet) {
	indexSet.rangeView.forEach { remove(in: NSRange(location: $0.lowerBound, length: $0.upperBound - $0.lowerBound)) }
	}

	open func removeAllIndexes() {
	_ranges = []
	_count = 0
	}

	open func add(_ value: Int) {
	add(in: NSMakeRange(value, 1))
	}

	open func remove(_ value: Int) {
	remove(in: NSMakeRange(value, 1))
	}

	internal func _insertRange(_ range: NSRange, atIndex index: Int) {
	_ranges.insert(range, at: index)
	_count += range.length
	}

	internal func _replaceRangeAtIndex(_ index: Int, withRange range: NSRange?) {
	let oldRange = _ranges[index]
	if let range = range {
	_ranges[index] = range
	_count += range.length - oldRange.length
	} else {
	_ranges.remove(at: index)
	_count -= oldRange.length
	}
	}

	internal func _mergeOverlappingRangesStartingAtIndex(_ index: Int) {
	var rangeIndex = index
	while _ranges.count > 0 && rangeIndex < _ranges.count - 1 {
	let curRange = _ranges[rangeIndex]
	let nextRange = _ranges[rangeIndex + 1]
	let curEnd = NSMaxRange(curRange)
	let nextEnd = NSMaxRange(nextRange)
	if curEnd >= nextRange.location {
	// overlaps
	if curEnd < nextEnd {
	self._replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(nextEnd - curRange.location, curRange.length))
	rangeIndex += 1
	}
	self._replaceRangeAtIndex(rangeIndex + 1, withRange: nil)
	} else {
	break
	}
	}
	}

	open func add(in range: NSRange) {
	guard range.length > 0 else {
	return
	}
	let addEnd = NSMaxRange(range)
	let startRangeIndex = _indexOfRangeBeforeOrContainingIndex(range.location) ?? 0
	var replacedRangeIndex : Int?
	var rangeIndex = startRangeIndex
	while rangeIndex < _ranges.count {
	let curRange = _ranges[rangeIndex]
	let curEnd = NSMaxRange(curRange)
	if addEnd < curRange.location {
	_insertRange(range, atIndex: rangeIndex)
	// Done. No need to merge
	return
	} else if range.location < curRange.location && addEnd >= curRange.location {
	if addEnd > curEnd {
	_replaceRangeAtIndex(rangeIndex, withRange: range)
	} else {
	_replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(range.location, curEnd - range.location))
	}
	replacedRangeIndex = rangeIndex
	// Proceed to merging
	break
	} else if range.location >= curRange.location && addEnd < curEnd {
	// Nothing to add
	return
	} else if range.location >= curRange.location && range.location <= curEnd && addEnd > curEnd {
	_replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(curRange.location, addEnd - curRange.location))
	replacedRangeIndex = rangeIndex
	// Proceed to merging
	break
	}
	rangeIndex += 1
	}
	if let r = replacedRangeIndex {
	_mergeOverlappingRangesStartingAtIndex(r)
	} else {
	_insertRange(range, atIndex: _ranges.count)
	}
	}

	open func remove(in range: NSRange) {
	guard range.length > 0 else {
	return
	}
	guard let startRangeIndex = (range.location > 0) ? _indexOfRangeAfterOrContainingIndex(range.location) : 0 else {
	return
	}
	let removeEnd = NSMaxRange(range)
	var rangeIndex = startRangeIndex
	while rangeIndex < _ranges.count {
	let curRange = _ranges[rangeIndex]
	let curEnd = NSMaxRange(curRange)

	if removeEnd < curRange.location {
	// Nothing to remove
	return
	} else if range.location <= curRange.location && removeEnd >= curRange.location {
	if removeEnd >= curEnd {
	_replaceRangeAtIndex(rangeIndex, withRange: nil)
	// Don't increment rangeIndex
	continue
	} else {
	self._replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(removeEnd, curEnd - removeEnd))
	return
	}
	} else if range.location > curRange.location && removeEnd < curEnd {
	let firstPiece = NSMakeRange(curRange.location, range.location - curRange.location)
	let secondPiece = NSMakeRange(removeEnd, curEnd - removeEnd)
	_replaceRangeAtIndex(rangeIndex, withRange: secondPiece)
	_insertRange(firstPiece, atIndex: rangeIndex)
	} else if range.location > curRange.location && range.location < curEnd && removeEnd >= curEnd {
	_replaceRangeAtIndex(rangeIndex, withRange: NSMakeRange(curRange.location, range.location - curRange.location))
	}
	rangeIndex += 1
	}

	}

	/* For a positive delta, shifts the indexes in [index, INT_MAX] to the right, thereby inserting an "empty space" [index, delta], for a negative delta, shifts the indexes in [index, INT_MAX] to the left, thereby deleting the indexes in the range [index - delta, delta].
	*/
	open func shiftIndexesStarting(at index: Int, by delta: Int) { NSUnimplemented() }
	}

	extension NSIndexSet : _StructTypeBridgeable {
	public typealias _StructType = IndexSet

	public func _bridgeToSwift() -> IndexSet {
	return IndexSet._unconditionallyBridgeFromObjectiveC(self)
	}
	}