stdlib: SE-0065: make UnsafeMutableAudioBufferListPointer a random-access collection again

Author: gribozavr

stdlib/public/SDK/CoreAudio/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_swift_library(swiftCoreAudio IS_SDK_OVERLAY
   CoreAudio.swift
+  ../../../public/core/WriteBackMutableSlice.swift
 
   TARGET_SDKS OSX IOS IOS_SIMULATOR TVOS TVOS_SIMULATOR
   SWIFT_MODULE_DEPENDS Dispatch

stdlib/public/SDK/CoreAudio/CoreAudio.swift

@@ -128,7 +128,11 @@ public struct UnsafeMutableAudioBufferListPointer {
 
 // FIXME: swift-3-indexing-model: conform to RandomAccessCollection
 // and update the test to reflect the change.
-extension UnsafeMutableAudioBufferListPointer : MutableCollection {
+extension UnsafeMutableAudioBufferListPointer
+  : MutableCollection, RandomAccessCollection {
+
+  public typealias Index = Int
+
   /// Always zero, which is the index of the first `AudioBuffer`.
   public var startIndex: Int {
     return 0
@@ -152,5 +156,21 @@ extension UnsafeMutableAudioBufferListPointer : MutableCollection {
       (_audioBuffersPointer + index).pointee = newValue
     }
   }
+
+  public subscript(bounds: Range<Int>)
+    -> MutableRandomAccessSlice<UnsafeMutableAudioBufferListPointer> {
+    get {
+      return MutableRandomAccessSlice(base: self, bounds: bounds)
+    }
+    set {
+      _writeBackMutableSlice(&self, bounds: bounds, slice: newValue)
+    }
+  }
+
+  public typealias Indices = CountableRange<Int>
+
+  public var indices: Indices {
+    return startIndex..<endIndex
+  }
 }
 

validation-test/stdlib/CoreAudio.swift

@@ -159,6 +159,16 @@ CoreAudioTestSuite.test("AudioBufferList.allocate(maximumBuffers: Int)/trap/over
   AudioBufferList.allocate(maximumBuffers: Int.max)
 }
 
+CoreAudioTestSuite.test("UnsafeMutableAudioBufferListPointer/AssociatedTypes") {
+  typealias Subject = UnsafeMutableAudioBufferListPointer
+  expectRandomAccessCollectionAssociatedTypes(
+    collectionType: Subject.self,
+    iteratorType: IndexingIterator<Subject>.self,
+    subSequenceType: MutableRandomAccessSlice<Subject>.self,
+    indexType: Int.self,
+    indexDistanceType: Int.self,
+    indicesType: CountableRange<Int>.self)
+}
 
 CoreAudioTestSuite.test(
   "UnsafeMutableAudioBufferListPointer.init(_: UnsafeMutablePointer<AudioBufferList>)," +
@@ -284,7 +294,7 @@ CoreAudioTestSuite.test("UnsafeMutableAudioBufferListPointer/Collection") {
   }
 
   // FIXME: use checkMutableRandomAccessCollection, when we have that function.
-  checkForwardCollection(expected, ablPtrWrapper)
+  checkRandomAccessCollection(expected, ablPtrWrapper)
   free(ablPtrWrapper.unsafeMutablePointer)
 }