Bug 1831120: feat(webgpu): add `GPUBuffer` attributes r=webgpu-reviewers,webidl,saschanaz,jimb

Differential Revision: https://phabricator.services.mozilla.com/D177055

dom/webgpu/Buffer.cpp

@@ -332,4 +332,17 @@ void Buffer::Destroy(JSContext* aCx, ErrorResult& aRv) {
   // examples
 }
 
+dom::GPUBufferMapState Buffer::MapState() const {
+  // Implementation reference:
+  // <https://gpuweb.github.io/gpuweb/#dom-gpubuffer-mapstate>.
+
+  if (mMapped) {
+    return dom::GPUBufferMapState::Mapped;
+  }
+  if (mMapRequest) {
+    return dom::GPUBufferMapState::Pending;
+  }
+  return dom::GPUBufferMapState::Unmapped;
+}
+
 }  // namespace mozilla::webgpu

dom/webgpu/Buffer.h

@@ -21,6 +21,7 @@ namespace dom {
 struct GPUBufferDescriptor;
 template <typename T>
 class Optional;
+enum class GPUBufferMapState : uint8_t;
 }  // namespace dom
 
 namespace webgpu {
@@ -59,6 +60,10 @@ class Buffer final : public ObjectBase, public ChildOf<Device> {
 
   const RawId mId;
 
+  uint64_t Size() const { return mSize; }
+  uint32_t Usage() const { return mUsage; }
+  dom::GPUBufferMapState MapState() const;
+
  private:
   Buffer(Device* const aParent, RawId aId, BufferAddress aSize, uint32_t aUsage,
          ipc::WritableSharedMemoryMapping&& aShmem);

dom/webidl/WebGPU.webidl

@@ -166,6 +166,13 @@ GPUDevice includes GPUObjectBase;
 [Pref="dom.webgpu.enabled",
  Exposed=(Window /* ,DedicatedWorker */), SecureContext]
 interface GPUBuffer {
+    // TODO: s/unsigned long long/GPUSize64/: https://github.com/gpuweb/gpuweb/issues/4080
+    readonly attribute unsigned long long size;
+    // TODO: s/unsigned long/GPUBufferUsageFlags/: https://github.com/gpuweb/gpuweb/issues/4080
+    readonly attribute unsigned long usage;
+
+    readonly attribute GPUBufferMapState mapState;
+
     [NewObject]
     Promise<undefined> mapAsync(GPUMapModeFlags mode, optional GPUSize64 offset = 0, optional GPUSize64 size);
     [NewObject, Throws]
@@ -177,6 +184,12 @@ interface GPUBuffer {
 };
 GPUBuffer includes GPUObjectBase;
 
+enum GPUBufferMapState {
+    "unmapped",
+    "pending",
+    "mapped"
+};
+
 dictionary GPUBufferDescriptor : GPUObjectDescriptorBase {
     required GPUSize64 size;
     required GPUBufferUsageFlags usage;