Bug 1575425 - Part 2: Merge ArrayBuffer and SharedArrayBuffer in DOM binding; r=bzbarsky,jwalden

We need this for upcoming change which supports having [AllowShared] on
ArrayBuffer type in WebIDL.

Differential Revision: https://phabricator.services.mozilla.com/D59989

--HG--
extra : moz-landing-system : lando

dom/bindings/TypedArray.h

@@ -10,6 +10,7 @@
 #include <utility>
 
 #include "js/ArrayBuffer.h"
+#include "js/ArrayBufferMaybeShared.h"
 #include "js/GCAPI.h"       // JS::AutoCheckCannotGC
 #include "js/RootingAPI.h"  // JS::Rooted
 #include "js/SharedArrayBuffer.h"
@@ -282,15 +283,12 @@ typedef ArrayBufferView_base<js::UnwrapArrayBufferView,
                              js::GetArrayBufferViewLengthAndData,
                              JS_GetArrayBufferViewType>
     ArrayBufferView;
-typedef TypedArray<uint8_t, JS::UnwrapArrayBuffer, JS::GetArrayBufferData,
-                   JS::GetArrayBufferLengthAndData, JS::NewArrayBuffer>
+typedef TypedArray<uint8_t, JS::UnwrapArrayBufferMaybeShared,
+                   JS::GetArrayBufferMaybeSharedData,
+                   JS::GetArrayBufferMaybeSharedLengthAndData,
+                   JS::NewArrayBuffer>
     ArrayBuffer;
 
-typedef TypedArray<
-    uint8_t, JS::UnwrapSharedArrayBuffer, JS::GetSharedArrayBufferData,
-    JS::GetSharedArrayBufferLengthAndData, JS::NewSharedArrayBuffer>
-    SharedArrayBuffer;
-
 // A class for converting an nsTArray to a TypedArray
 // Note: A TypedArrayCreator must not outlive the nsTArray it was created from.
 //       So this is best used to pass from things that understand nsTArray to

js/public/ArrayBufferMaybeShared.h

@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * Functions for working with either ArrayBuffer or SharedArrayBuffer objects
+ * in agnostic fashion.
+ */
+
+#ifndef js_ArrayBufferMaybeShared_h
+#define js_ArrayBufferMaybeShared_h
+
+#include <stdint.h>  // uint8_t, uint32_t
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+struct JS_PUBLIC_API JSContext;
+class JS_PUBLIC_API JSObject;
+
+namespace JS {
+
+class JS_PUBLIC_API AutoRequireNoGC;
+
+// TYPE TESTING
+
+/**
+ * Check whether obj supports the JS::GetArrayBufferMaybeShared* APIs.  Note
+ * that this may return false if a security wrapper is encountered that denies
+ * the unwrapping. If this test succeeds, then it is safe to call the various
+ * predicate and accessor JSAPI calls defined below.
+ */
+extern JS_PUBLIC_API bool IsArrayBufferObjectMaybeShared(JSObject* obj);
+
+// ACCESSORS
+
+/*
+ * Test for ArrayBufferMaybeShared subtypes and return the unwrapped object if
+ * so, else nullptr. Never throws.
+ */
+extern JS_PUBLIC_API JSObject* UnwrapArrayBufferMaybeShared(JSObject* obj);
+
+/**
+ * Get the length, sharedness, and data from an ArrayBufferMaybeShared subtypes.
+ *
+ * The computed length and data pointer may be invalidated by a GC or by an
+ * unshared array buffer becoming detached. Callers must take care not to
+ * perform any actions that could trigger a GC or result in an unshared array
+ * buffer becoming detached. If such actions nonetheless must be performed,
+ * callers should perform this call a second time (and sensibly handle results
+ * that may be different from those returned the first time). (Sharedness is an
+ * immutable characteristic of an array buffer or shared array buffer, so that
+ * boolean remains valid across GC or detaching.)
+ *
+ * |obj| must be an ArrayBufferMaybeShared subtype: an ArrayBuffer or a
+ * SharedArrayBuffer.
+ *
+ * |*length| will be set to bytes in the buffer.
+ *
+ * |*isSharedMemory| will be set to true if it is a SharedArrayBuffer, otherwise
+ * to false.
+ *
+ * |*data| will be set to a pointer to the bytes in the buffer.
+ */
+extern JS_PUBLIC_API void GetArrayBufferMaybeSharedLengthAndData(
+    JSObject* obj, uint32_t* length, bool* isSharedMemory, uint8_t** data);
+
+/**
+ * Return a pointer to the start of the array buffer's data, and indicate
+ * whether the data is from a shared array buffer through an outparam.
+ *
+ * The returned data pointer may be invalidated by a GC or by an unshared array
+ * buffer becoming detached. Callers must take care not to perform any actions
+ * that could trigger a GC or result in an unshared array buffer becoming
+ * detached. If such actions nonetheless must be performed, callers should
+ * perform this call a second time (and sensibly handle results that may be
+ * different from those returned the first time). (Sharedness is an immutable
+ * characteristic of an array buffer or shared array buffer, so that boolean
+ * remains valid across GC or detaching.)
+ *
+ * |obj| must have passed a JS::IsArrayBufferObjectMaybeShared test, or somehow
+ * be known that it would pass such a test: it is an ArrayBuffer or
+ * SharedArrayBuffer or a wrapper of an ArrayBuffer/SharedArrayBuffer, and the
+ * unwrapping will succeed.
+ *
+ * |*isSharedMemory| will be set to true if the typed array maps a
+ * SharedArrayBuffer, otherwise to false.
+ */
+extern JS_PUBLIC_API uint8_t* GetArrayBufferMaybeSharedData(
+    JSObject* obj, bool* isSharedMemory, const AutoRequireNoGC&);
+
+}  // namespace JS
+
+#endif /* js_ArrayBufferMaybeShared_h */

js/src/moz.build

@@ -125,6 +125,7 @@ EXPORTS.js += [
     '../public/AllocPolicy.h',
     '../public/Array.h',
     '../public/ArrayBuffer.h',
+    '../public/ArrayBufferMaybeShared.h',
     '../public/BinASTFormat.h',
     '../public/BuildId.h',
     '../public/CallArgs.h',
@@ -293,6 +294,7 @@ UNIFIED_SOURCES += [
     'vm/Activation.cpp',
     'vm/ArgumentsObject.cpp',
     'vm/ArrayBufferObject.cpp',
+    'vm/ArrayBufferObjectMaybeShared.cpp',
     'vm/ArrayBufferViewObject.cpp',
     'vm/AsyncFunction.cpp',
     'vm/AsyncIteration.cpp',

js/src/vm/ArrayBufferObjectMaybeShared.cpp

@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+
+#include <stdint.h>  // uint8_t, uint32_t
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+#include "js/ArrayBufferMaybeShared.h"
+#include "vm/ArrayBufferObject.h"  // js::ArrayBufferObject
+#include "vm/JSObject.h"           // JSObject
+#include "vm/SharedArrayObject.h"  // js::SharedArrayBufferObject
+#include "vm/SharedMem.h"          // SharedMem
+
+using namespace js;
+
+JS_PUBLIC_API bool JS::IsArrayBufferObjectMaybeShared(JSObject* obj) {
+  return obj->canUnwrapAs<ArrayBufferObjectMaybeShared>();
+}
+
+JS_PUBLIC_API JSObject* JS::UnwrapArrayBufferMaybeShared(JSObject* obj) {
+  return obj->maybeUnwrapIf<ArrayBufferObjectMaybeShared>();
+}
+
+JS_PUBLIC_API void JS::GetArrayBufferMaybeSharedLengthAndData(
+    JSObject* obj, uint32_t* length, bool* isSharedMemory, uint8_t** data) {
+  MOZ_ASSERT(obj->is<ArrayBufferObjectMaybeShared>());
+
+  bool isSharedArrayBuffer = obj->is<SharedArrayBufferObject>();
+  *length = isSharedArrayBuffer
+                ? obj->as<SharedArrayBufferObject>().byteLength()
+                : obj->as<ArrayBufferObject>().byteLength();
+  *data = isSharedArrayBuffer
+              ? obj->as<SharedArrayBufferObject>().dataPointerShared().unwrap()
+              : obj->as<ArrayBufferObject>().dataPointer();
+  *isSharedMemory = isSharedArrayBuffer;
+}
+
+JS_PUBLIC_API uint8_t* JS::GetArrayBufferMaybeSharedData(
+    JSObject* obj, bool* isSharedMemory, const JS::AutoRequireNoGC&) {
+  MOZ_ASSERT(obj->maybeUnwrapIf<ArrayBufferObjectMaybeShared>());
+
+  if (ArrayBufferObject* aobj = obj->maybeUnwrapIf<ArrayBufferObject>()) {
+    *isSharedMemory = false;
+    return aobj->dataPointer();
+  } else if (SharedArrayBufferObject* saobj =
+                 obj->maybeUnwrapIf<SharedArrayBufferObject>()) {
+    *isSharedMemory = true;
+    return saobj->dataPointerShared().unwrap();
+  }
+
+  return nullptr;
+}