[stdlib] Fixed bugs with string views

Fixes rdar://problem/18435682
Fixes rdar://problem/19238102

Swift SVN r24117

Author: mxswd

stdlib/core/StringUTF16.swift

@@ -12,7 +12,7 @@
 
 extension String {
   /// A collection of UTF-16 code units that encodes a `String` value.
-  public struct UTF16View : Sliceable, Reflectable {
+  public struct UTF16View : Sliceable, Reflectable, Printable, DebugPrintable {
     public struct Index {
       // Foundation needs access to these fields so it can expose
       // random access
@@ -144,6 +144,16 @@ extension String {
       return _UTF16ViewMirror(self)
     }
 
+    public var description: String {
+      let start = _toInternalIndex(0)
+      let end = _toInternalIndex(_length)
+      return String(_core[start..<end])
+    }
+
+    public var debugDescription: String {
+      return "StringUTF16(\(self.description.debugDescription))"
+    }
+
     var _offset: Int
     var _length: Int
     let _core: _StringCore

stdlib/core/StringUTF8.swift

@@ -83,11 +83,28 @@ extension _StringCore {
 
 extension String {
   /// A collection of UTF-8 code units that encodes a `String` value.
-  public struct UTF8View : CollectionType, Reflectable {
+  public struct UTF8View : CollectionType, Reflectable, Printable,
+    DebugPrintable {
     internal let _core: _StringCore
+    // These are optional as a work around for a compiler segfault.
+    internal let _startIndex: Index!
+    internal let _endIndex: Index!
 
     init(_ _core: _StringCore) {
       self._core = _core
+      self._endIndex = Index(_core, _core.endIndex, Index._emptyBuffer)
+      if _fastPath(_core.count != 0) {
+        let (_, buffer) = _core._encodeSomeUTF8(0)
+        self._startIndex = Index(_core, 0, buffer)
+      } else {
+        self._startIndex = self._endIndex
+      }
+    }
+
+    init(_ _core: _StringCore, _ s: Index, _ e: Index) {
+      self._core = _core
+      self._startIndex = s
+      self._endIndex = e
     }
 
     /// A position in a `String.UTF8View`
@@ -179,11 +196,7 @@ extension String {
     /// The position of the first code unit if the `String` is
     /// non-empty; identical to `endIndex` otherwise.
     public var startIndex: Index {
-      if _fastPath(_core.count != 0) {
-        let (_, buffer) = _core._encodeSomeUTF8(0)
-        return Index(_core, 0, buffer)
-      }
-      return endIndex
+      return self._startIndex
     }
 
     /// The "past the end" position.
@@ -192,7 +205,7 @@ extension String {
     /// reachable from `startIndex` by zero or more applications of
     /// `successor()`.
     public var endIndex: Index {
-      return Index(_core, _core.endIndex, Index._emptyBuffer)
+      return self._endIndex
     }
 
     /// Access the element at `position`.
@@ -205,6 +218,15 @@ extension String {
       return result
     }
 
+    /// Access the elements delimited by the given half-open range of
+    /// indices.
+    ///
+    /// Complexity: O(1) unless bridging from Objective-C requires an
+    /// O(N) conversion.
+    public subscript(subRange: Range<Index>) -> UTF8View {
+      return UTF8View(_core, subRange.startIndex, subRange.endIndex)
+    }
+
     /// Return a *generator* over the code points that comprise this
     /// *sequence*.
     ///
@@ -217,6 +239,14 @@ extension String {
     public func getMirror() -> MirrorType {
       return _UTF8ViewMirror(self)
     }
+    
+    public var description: String {
+      return String._fromCodeUnitSequenceWithRepair(UTF8.self, input: self).0
+    }
+
+    public var debugDescription: String {
+      return "UTF8View(\(self.description.debugDescription))"
+    }
   }
 
   /// A UTF-8 encoding of `self`.

stdlib/core/StringUTFViewsMirrors.swift.gyb

@@ -32,7 +32,7 @@ extension String {
         return ("[\(i)]", reflect(_value[advance(_value.startIndex, i)]))
       }
 
-      var summary: String { return String(_value._core) }
+      var summary: String { return _value.description }
 
       var quickLookObject: QuickLookObject? { return .Some(.Text(summary)) }
   }

stdlib/core/StringUnicodeScalarView.swift

@@ -28,7 +28,8 @@ extension String {
   /// A collection of `Unicode scalar values
   /// <http://www.unicode.org/glossary/#unicode_scalar_value>`_ that
   /// encode a `String` .
-  public struct UnicodeScalarView : Sliceable, SequenceType, Reflectable {
+  public struct UnicodeScalarView : Sliceable, SequenceType, Reflectable,
+    Printable, DebugPrintable {
     init(_ _core: _StringCore) {
       self._core = _core
     }
@@ -210,6 +211,14 @@ extension String {
       return _UnicodeScalarViewMirror(self)
     }
 
+    public var description: String {
+      return String(_core[self.startIndex._position..<self.endIndex._position])
+    }
+
+    public var debugDescription: String {
+      return "StringUnicodeScalarView(\(self.description.debugDescription))"
+    }
+
     var _core: _StringCore
   }
 

test/1_stdlib/String.swift

@@ -964,5 +964,40 @@ StringTests.test("uppercaseString") {
   expectEqual("\u{0046}\u{0049}", "\u{fb01}".uppercaseString)
 }
 
+StringTests.test("unicodeViews") {
+  // Check the UTF views work with slicing
+
+  // U+FFFD REPLACEMENT CHARACTER
+  // U+1F3C2 SNOWBOARDER
+  // U+2603 SNOWMAN
+  let winter = "\u{1F3C2}\u{2603}"
+
+  // slices
+  // It is 4 bytes long, so it should return a replacement character.
+  expectEqual("\u{FFFD}", toString(winter.utf8[winter.utf8.startIndex ..<
+    winter.utf8.startIndex.successor().successor()]))
+  expectEqual("\u{1F3C2}", toString(winter.utf8[winter.utf8.startIndex ..<
+    advance(winter.utf8.startIndex, 4)]))
+
+  expectEqual("\u{1F3C2}", toString(winter.utf16[winter.utf16.startIndex ..<
+    advance(winter.utf16.startIndex, 2)]))
+  expectEqual("\u{1F3C2}", toString(winter.unicodeScalars[
+    winter.unicodeScalars.startIndex ..<
+    winter.unicodeScalars.startIndex.successor()]))
+
+  // views
+  expectEqual(winter, toString(winter.utf8[winter.utf8.startIndex ..<
+    advance(winter.utf8.startIndex, 7)]))
+  expectEqual(winter, toString(winter.utf16[winter.utf16.startIndex ..<
+    advance(winter.utf16.startIndex, 3)]))
+  expectEqual(winter, toString(
+    winter.unicodeScalars[winter.unicodeScalars.startIndex ..<
+    advance(winter.unicodeScalars.startIndex, 2)]))
+
+  let ga = "\u{304b}\u{3099}"
+  expectEqual(ga, toString(ga.utf8[ga.utf8.startIndex ..<
+    advance(ga.utf8.startIndex, 6)]))
+}
+
 runAllTests()