index on master: d94b498 Merge pull request swiftlang#9775 from eeckstein/fix-bench

Author: Dave Abrahams

stdlib/public/core/StringIndex.swift

@@ -0,0 +1,53 @@
+//===--- StringIndex.swift ------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 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
+//
+//===----------------------------------------------------------------------===//
+extension String {
+  public struct Index {
+    internal var _compoundOffset : UInt64
+    internal var _cache: _Cache
+    
+    internal enum _Cache {
+    case utf16
+    case utf8(encodedScalar: Unicode.UTF8.EncodedScalar)
+    case character(stride: UInt16)
+    case unicodeScalar(value: Unicode.Scalar)
+    }
+  }
+}
+
+extension String.Index : Equatable {
+  public static func == (lhs: String.Index, rhs: String.Index) -> Bool {
+    return lhs._compoundOffset == rhs._compoundOffset
+  }
+}
+
+extension String.Index : Comparable {
+  public static func < (lhs: String.Index, rhs: String.Index) -> Bool {
+    return lhs._compoundOffset < rhs._compoundOffset
+  }
+}
+
+extension String.Index {
+  internal init(_ c: Cache, atEncodedOffset o: Int) {
+    self._compoundOffset = UInt64(o << _strideBits)
+    self.cache = c
+  }
+  
+  internal var _strideBits : Int { return 16 }
+
+  internal mutating func _setEncodedOffset(_ x: Int) {
+    _compoundOffset = UInt64(x << _strideBits)
+  }
+  
+  public var encodedOffset : Int {
+    return Int(_compoundOffset >> _strideBits)
+  }
+}