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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
*
* Copyright 2021 Mozilla Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef wasm_shareable_h
#define wasm_shareable_h
#include "mozilla/RefPtr.h"
#include "js/RefCounted.h"
#include "wasm/WasmTypeDecls.h"
namespace js {
namespace wasm {
// This reusable base class factors out the logic for a resource that is shared
// by multiple instances/modules but should only be counted once when computing
// about:memory stats.
template <class T>
using SeenSet = HashSet<const T*, DefaultHasher<const T*>, SystemAllocPolicy>;
template <class T>
struct ShareableBase : AtomicRefCounted<T> {
using SeenSet = wasm::SeenSet<T>;
size_t sizeOfIncludingThisIfNotSeen(mozilla::MallocSizeOf mallocSizeOf,
SeenSet* seen) const {
const T* self = static_cast<const T*>(this);
typename SeenSet::AddPtr p = seen->lookupForAdd(self);
if (p) {
return 0;
}
bool ok = seen->add(p, self);
(void)ok; // oh well
return mallocSizeOf(self) + self->sizeOfExcludingThis(mallocSizeOf);
}
};
// ShareableBytes is a reference-counted Vector of bytes.
// Vector is 'final' and cannot be inherited to combine with ShareableBase, so
// we need to define a wrapper class with boilerplate methods.
template <typename T, size_t MinInlineCapacity, class AllocPolicy>
struct ShareableVector
: public ShareableBase<ShareableVector<T, MinInlineCapacity, AllocPolicy>> {
using VecT = mozilla::Vector<T, MinInlineCapacity, AllocPolicy>;
VecT vector;
size_t length() const { return vector.length(); }
bool empty() const { return vector.empty(); }
T* begin() { return vector.begin(); }
T* end() { return vector.end(); }
const T* begin() const { return vector.begin(); }
const T* end() const { return vector.end(); }
mozilla::Span<const T> span() const {
return mozilla::Span<const T>(begin(), end());
}
size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
return vector.sizeOfExcludingThis(mallocSizeOf);
}
bool append(const T* start, size_t len) { return vector.append(start, len); }
bool appendAll(const VecT& other) { return vector.appendAll(other); }
void shrinkTo(size_t len) { return vector.shrinkTo(len); }
ShareableVector() = default;
explicit ShareableVector(VecT&& vector) : vector(std::move(vector)) {}
static const ShareableVector* fromSpan(mozilla::Span<const T> span) {
ShareableVector* vector = js_new<ShareableVector>();
if (!vector) {
return nullptr;
}
// If we succeed in allocating the vector but fail to append something to
// it, we need to delete this vector before returning.
if (!vector->append(span.data(), span.size())) {
js_free(vector);
return nullptr;
}
return vector;
}
};
using ShareableBytes = ShareableVector<uint8_t, 0, SystemAllocPolicy>;
using MutableBytes = RefPtr<ShareableBytes>;
using SharedBytes = RefPtr<const ShareableBytes>;
struct ShareableChars : public ShareableBase<ShareableChars> {
UniqueChars chars;
ShareableChars() = default;
explicit ShareableChars(UniqueChars&& chars) : chars(std::move(chars)) {}
};
using SharedChars = RefPtr<const ShareableChars>;
} // namespace wasm
} // namespace js
#endif // wasm_shareable_h