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-rw-r--r--js/src/ds/FixedLengthVector.h111
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diff --git a/js/src/ds/FixedLengthVector.h b/js/src/ds/FixedLengthVector.h
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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:
+ * 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/. */
+
+#ifndef ds_FixedLengthVector_h
+#define ds_FixedLengthVector_h
+
+#include "mozilla/Assertions.h" // MOZ_ASSERT
+#include "mozilla/OperatorNewExtensions.h" // mozilla::KnownNotNull
+
+#include <stddef.h> // size_t
+
+#include "js/Utility.h" // js_free
+#include "vm/JSContext.h" // JSContext
+
+namespace js {
+
+// A dynamically-allocated fixed-length vector with bounds checking assertions.
+template <typename T>
+class FixedLengthVector {
+ // The pointer to the storage.
+ T* data_ = nullptr;
+
+ // The size of the storage.
+ size_t length_ = 0;
+
+ public:
+ FixedLengthVector() = default;
+
+ FixedLengthVector(FixedLengthVector&) = delete;
+ FixedLengthVector(FixedLengthVector&&) = default;
+
+ ~FixedLengthVector() {
+ if (initialized()) {
+ js_free(data_);
+ }
+ }
+
+ size_t length() const { return length_; }
+
+ bool initialized() const { return !!data_; }
+
+ // Allocate the storage with the given size, wihtout calling constructor.
+ //
+ // If the allocation fails, this returns false and sets the
+ // pending exception on the given context.
+ [[nodiscard]] bool allocateUninitialized(JSContext* cx, size_t length) {
+ MOZ_ASSERT(!initialized());
+
+ length_ = length;
+ data_ = cx->pod_malloc<T>(length);
+ if (MOZ_UNLIKELY(!data_)) {
+ return false;
+ }
+
+ return true;
+ }
+
+ // Allocate the storage with the given size and call default constructor.
+ //
+ // If the allocation fails, this returns false and sets the
+ // pending exception on the given context.
+ [[nodiscard]] bool allocate(JSContext* cx, size_t length) {
+ if (!allocateUninitialized(cx, length)) {
+ return false;
+ }
+
+ for (size_t i = 0; i < length; i++) {
+ new (mozilla::KnownNotNull, &data_[i]) T();
+ }
+ return true;
+ }
+
+ T* begin() {
+ MOZ_ASSERT(initialized());
+ return data_;
+ }
+
+ const T* begin() const {
+ MOZ_ASSERT(initialized());
+ return data_;
+ }
+
+ T* end() {
+ MOZ_ASSERT(initialized());
+ return data_ + length_;
+ }
+
+ const T* end() const {
+ MOZ_ASSERT(initialized());
+ return data_ + length_;
+ }
+
+ T& operator[](size_t index) {
+ MOZ_ASSERT(initialized());
+ MOZ_ASSERT(index < length_);
+ return begin()[index];
+ }
+
+ const T& operator[](size_t index) const {
+ MOZ_ASSERT(initialized());
+ MOZ_ASSERT(index < length_);
+ return begin()[index];
+ }
+};
+
+} // namespace js
+
+#endif // ds_FixedLengthVector_h