summaryrefslogtreecommitdiffstats
path: root/js/public/ForOfIterator.h
diff options
context:
space:
mode:
authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-19 00:47:55 +0000
commit26a029d407be480d791972afb5975cf62c9360a6 (patch)
treef435a8308119effd964b339f76abb83a57c29483 /js/public/ForOfIterator.h
parentInitial commit. (diff)
downloadfirefox-26a029d407be480d791972afb5975cf62c9360a6.tar.xz
firefox-26a029d407be480d791972afb5975cf62c9360a6.zip
Adding upstream version 124.0.1.upstream/124.0.1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--js/public/ForOfIterator.h118
1 files changed, 118 insertions, 0 deletions
diff --git a/js/public/ForOfIterator.h b/js/public/ForOfIterator.h
new file mode 100644
index 0000000000..db0a099e5e
--- /dev/null
+++ b/js/public/ForOfIterator.h
@@ -0,0 +1,118 @@
+/* -*- 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/. */
+
+/*
+ * A convenience class that makes it easy to perform the operations of a for-of
+ * loop.
+ */
+
+#ifndef js_ForOfIterator_h
+#define js_ForOfIterator_h
+
+#include "mozilla/Attributes.h" // MOZ_STACK_CLASS
+
+#include <stdint.h> // UINT32_MAX, uint32_t
+
+#include "jstypes.h" // JS_PUBLIC_API
+
+#include "js/RootingAPI.h" // JS::{Handle,Rooted}
+#include "js/Value.h" // JS::Value, JS::{,Mutable}Handle<JS::Value>
+
+struct JS_PUBLIC_API JSContext;
+class JS_PUBLIC_API JSObject;
+
+namespace JS {
+
+/**
+ * A convenience class for imitating a JS for-of loop. Typical usage:
+ *
+ * JS::ForOfIterator it(cx);
+ * if (!it.init(iterable)) {
+ * return false;
+ * }
+ * JS::Rooted<JS::Value> val(cx);
+ * while (true) {
+ * bool done;
+ * if (!it.next(&val, &done)) {
+ * return false;
+ * }
+ * if (done) {
+ * break;
+ * }
+ * if (!DoStuff(cx, val)) {
+ * return false;
+ * }
+ * }
+ */
+class MOZ_STACK_CLASS JS_PUBLIC_API ForOfIterator {
+ protected:
+ JSContext* cx_;
+
+ // Use the ForOfPIC on the global object (see vm/GlobalObject.h) to try to
+ // optimize iteration across arrays.
+ //
+ // Case 1: Regular Iteration
+ // iterator - pointer to the iterator object.
+ // nextMethod - value of |iterator|.next.
+ // index - fixed to NOT_ARRAY (== UINT32_MAX)
+ //
+ // Case 2: Optimized Array Iteration
+ // iterator - pointer to the array object.
+ // nextMethod - the undefined value.
+ // index - current position in array.
+ //
+ // The cases are distinguished by whether |index == NOT_ARRAY|.
+ Rooted<JSObject*> iterator;
+ Rooted<Value> nextMethod;
+
+ static constexpr uint32_t NOT_ARRAY = UINT32_MAX;
+
+ uint32_t index = NOT_ARRAY;
+
+ ForOfIterator(const ForOfIterator&) = delete;
+ ForOfIterator& operator=(const ForOfIterator&) = delete;
+
+ public:
+ explicit ForOfIterator(JSContext* cx)
+ : cx_(cx), iterator(cx), nextMethod(cx) {}
+
+ enum NonIterableBehavior { ThrowOnNonIterable, AllowNonIterable };
+
+ /**
+ * Initialize the iterator. If AllowNonIterable is passed then if getting
+ * the @@iterator property from iterable returns undefined init() will just
+ * return true instead of throwing. Callers must then check
+ * valueIsIterable() before continuing with the iteration.
+ */
+ [[nodiscard]] bool init(
+ Handle<Value> iterable,
+ NonIterableBehavior nonIterableBehavior = ThrowOnNonIterable);
+
+ /**
+ * Get the next value from the iterator. If false *done is true
+ * after this call, do not examine val.
+ */
+ [[nodiscard]] bool next(MutableHandle<Value> val, bool* done);
+
+ /**
+ * Close the iterator.
+ * For the case that completion type is throw.
+ */
+ void closeThrow();
+
+ /**
+ * If initialized with throwOnNonCallable = false, check whether
+ * the value is iterable.
+ */
+ bool valueIsIterable() const { return iterator; }
+
+ private:
+ inline bool nextFromOptimizedArray(MutableHandle<Value> val, bool* done);
+};
+
+} // namespace JS
+
+#endif // js_ForOfIterator_h