| //===--- RangeSelection.swift ---------------------------------------------===// |
| // |
| // This source file is part of the Swift.org open source project |
| // |
| // Copyright (c) 2014 - 2020 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 |
| // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors |
| // |
| //===----------------------------------------------------------------------===// |
| |
| import StdlibUnittest |
| |
| public enum RangeSelection { |
| case emptyRange |
| case leftEdge |
| case rightEdge |
| case middle |
| case leftHalf |
| case rightHalf |
| case full |
| case offsets(Int, Int) |
| |
| public var isEmpty: Bool { |
| switch self { |
| case .emptyRange: return true |
| default: return false |
| } |
| } |
| |
| public func range<C : Collection>(in c: C) -> Range<C.Index> { |
| switch self { |
| case .emptyRange: return c.endIndex..<c.endIndex |
| case .leftEdge: return c.startIndex..<c.startIndex |
| case .rightEdge: return c.endIndex..<c.endIndex |
| case .middle: |
| let start = c.index(c.startIndex, offsetBy: c.count / 4) |
| let end = c.index(c.startIndex, offsetBy: 3 * c.count / 4 + 1) |
| return start..<end |
| case .leftHalf: |
| let start = c.startIndex |
| let end = c.index(start, offsetBy: c.count / 2) |
| return start..<end |
| case .rightHalf: |
| let start = c.index(c.startIndex, offsetBy: c.count / 2) |
| let end = c.endIndex |
| return start..<end |
| case .full: |
| return c.startIndex..<c.endIndex |
| case let .offsets(lowerBound, upperBound): |
| let start = c.index(c.startIndex, offsetBy: lowerBound) |
| let end = c.index(c.startIndex, offsetBy: upperBound) |
| return start..<end |
| } |
| } |
| |
| public func closedRange<C : Collection>(in c: C) -> ClosedRange<C.Index> { |
| switch self { |
| case .emptyRange: fatalError("Closed range cannot be empty") |
| case .leftEdge: return c.startIndex...c.startIndex |
| case .rightEdge: |
| let beforeEnd = c.index(c.startIndex, offsetBy: c.count - 1) |
| return beforeEnd...beforeEnd |
| case .middle: |
| let start = c.index(c.startIndex, offsetBy: c.count / 4) |
| let end = c.index(c.startIndex, offsetBy: 3 * c.count / 4) |
| return start...end |
| case .leftHalf: |
| let start = c.startIndex |
| let end = c.index(start, offsetBy: c.count / 2 - 1) |
| return start...end |
| case .rightHalf: |
| let start = c.index(c.startIndex, offsetBy: c.count / 2) |
| let beforeEnd = c.index(c.startIndex, offsetBy: c.count - 1) |
| return start...beforeEnd |
| case .full: |
| let beforeEnd = c.index(c.startIndex, offsetBy: c.count - 1) |
| return c.startIndex...beforeEnd |
| case let .offsets(lowerBound, upperBound): |
| let start = c.index(c.startIndex, offsetBy: lowerBound) |
| let end = c.index(c.startIndex, offsetBy: upperBound) |
| return start...end |
| } |
| } |
| } |
