1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- 2 * vim: set ts=8 sts=2 et sw=2 tw=80: 3 * 4 * Copyright 2021 Mozilla Foundation 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 #ifndef wasm_shareable_h 20 #define wasm_shareable_h 21 22 #include "mozilla/RefPtr.h" 23 #include "js/RefCounted.h" 24 #include "wasm/WasmTypeDecls.h" 25 26 namespace js { 27 namespace wasm { 28 29 using mozilla::MallocSizeOf; 30 31 // This reusable base class factors out the logic for a resource that is shared 32 // by multiple instances/modules but should only be counted once when computing 33 // about:memory stats. 34 35 template <class T> 36 struct ShareableBase : AtomicRefCounted<T> { 37 using SeenSet = HashSet<const T*, DefaultHasher<const T*>, SystemAllocPolicy>; 38 sizeOfIncludingThisIfNotSeenShareableBase39 size_t sizeOfIncludingThisIfNotSeen(MallocSizeOf mallocSizeOf, 40 SeenSet* seen) const { 41 const T* self = static_cast<const T*>(this); 42 typename SeenSet::AddPtr p = seen->lookupForAdd(self); 43 if (p) { 44 return 0; 45 } 46 bool ok = seen->add(p, self); 47 (void)ok; // oh well 48 return mallocSizeOf(self) + self->sizeOfExcludingThis(mallocSizeOf); 49 } 50 }; 51 52 // ShareableBytes is a reference-counted Vector of bytes. 53 54 struct ShareableBytes : ShareableBase<ShareableBytes> { 55 // Vector is 'final', so instead make Vector a member and add boilerplate. 56 Bytes bytes; 57 58 ShareableBytes() = default; ShareableBytesShareableBytes59 explicit ShareableBytes(Bytes&& bytes) : bytes(std::move(bytes)) {} sizeOfExcludingThisShareableBytes60 size_t sizeOfExcludingThis(MallocSizeOf mallocSizeOf) const { 61 return bytes.sizeOfExcludingThis(mallocSizeOf); 62 } beginShareableBytes63 const uint8_t* begin() const { return bytes.begin(); } endShareableBytes64 const uint8_t* end() const { return bytes.end(); } lengthShareableBytes65 size_t length() const { return bytes.length(); } appendShareableBytes66 bool append(const uint8_t* start, size_t len) { 67 return bytes.append(start, len); 68 } 69 }; 70 71 using MutableBytes = RefPtr<ShareableBytes>; 72 using SharedBytes = RefPtr<const ShareableBytes>; 73 74 } // namespace wasm 75 } // namespace js 76 77 #endif // wasm_shareable_h 78