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c40e81a2e9
Differential Revision: https://phabricator.services.mozilla.com/D24257 --HG-- rename : js/src/jsapi.h => js/public/ForOfIterator.h extra : moz-landing-system : lando
119 lines
3.3 KiB
C++
119 lines
3.3 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
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* vim: set ts=8 sts=2 et sw=2 tw=80:
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/*
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* A convenience class that makes it easy to perform the operations of a for-of
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* loop.
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*/
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#ifndef js_ForOfIterator_h
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#define js_ForOfIterator_h
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#include "mozilla/Attributes.h" // MOZ_MUST_USE, MOZ_STACK_CLASS
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#include <stdint.h> // UINT32_MAX, uint32_t
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#include "jstypes.h" // JS_PUBLIC_API
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#include "js/RootingAPI.h" // JS::{Handle,Rooted}
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#include "js/Value.h" // JS::Value, JS::{,Mutable}Handle<JS::Value>
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struct JSContext;
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class JSObject;
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namespace JS {
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/**
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* A convenience class for imitating a JS for-of loop. Typical usage:
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*
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* JS::ForOfIterator it(cx);
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* if (!it.init(iterable)) {
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* return false;
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* }
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* JS::Rooted<JS::Value> val(cx);
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* while (true) {
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* bool done;
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* if (!it.next(&val, &done)) {
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* return false;
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* }
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* if (done) {
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* break;
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* }
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* if (!DoStuff(cx, val)) {
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* return false;
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* }
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* }
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*/
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class MOZ_STACK_CLASS JS_PUBLIC_API ForOfIterator {
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protected:
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JSContext* cx_;
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// Use the ForOfPIC on the global object (see vm/GlobalObject.h) to try to
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// optimize iteration across arrays.
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//
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// Case 1: Regular Iteration
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// iterator - pointer to the iterator object.
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// nextMethod - value of |iterator|.next.
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// index - fixed to NOT_ARRAY (== UINT32_MAX)
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//
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// Case 2: Optimized Array Iteration
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// iterator - pointer to the array object.
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// nextMethod - the undefined value.
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// index - current position in array.
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//
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// The cases are distinguished by whether |index == NOT_ARRAY|.
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Rooted<JSObject*> iterator;
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Rooted<Value> nextMethod;
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static constexpr uint32_t NOT_ARRAY = UINT32_MAX;
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uint32_t index = NOT_ARRAY;
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ForOfIterator(const ForOfIterator&) = delete;
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ForOfIterator& operator=(const ForOfIterator&) = delete;
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public:
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explicit ForOfIterator(JSContext* cx)
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: cx_(cx), iterator(cx), nextMethod(cx) {}
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enum NonIterableBehavior { ThrowOnNonIterable, AllowNonIterable };
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/**
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* Initialize the iterator. If AllowNonIterable is passed then if getting
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* the @@iterator property from iterable returns undefined init() will just
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* return true instead of throwing. Callers must then check
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* valueIsIterable() before continuing with the iteration.
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*/
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MOZ_MUST_USE bool init(
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Handle<Value> iterable,
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NonIterableBehavior nonIterableBehavior = ThrowOnNonIterable);
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/**
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* Get the next value from the iterator. If false *done is true
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* after this call, do not examine val.
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*/
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MOZ_MUST_USE bool next(MutableHandle<Value> val, bool* done);
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/**
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* Close the iterator.
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* For the case that completion type is throw.
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*/
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void closeThrow();
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/**
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* If initialized with throwOnNonCallable = false, check whether
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* the value is iterable.
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*/
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bool valueIsIterable() const { return iterator; }
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private:
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inline bool nextFromOptimizedArray(MutableHandle<Value> val, bool* done);
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};
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} // namespace JS
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#endif // js_ForOfIterator_h
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