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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 js_WaitCallbacks_h
#define js_WaitCallbacks_h
#include <stddef.h>
#include <stdint.h>
#include "jstypes.h"
struct JS_PUBLIC_API JSRuntime;
namespace JS {
/**
* When the JSRuntime is about to block in an Atomics.wait() JS call or in a
* `wait` instruction in WebAssembly, it can notify the host by means of a call
* to BeforeWaitCallback. After the wait, it can notify the host by means of a
* call to AfterWaitCallback. Both callbacks must be null, or neither.
*
* (If you change the callbacks from null to not-null or vice versa while some
* thread on the runtime is in a wait, you will be sorry.)
*
* The argument to the BeforeWaitCallback is a pointer to uninitialized
* stack-allocated working memory of size WAIT_CALLBACK_CLIENT_MAXMEM bytes.
* The caller of SetWaitCallback() must pass the amount of memory it will need,
* and this amount will be checked against that limit and the process will crash
* reliably if the check fails.
*
* The value returned by the BeforeWaitCallback will be passed to the
* AfterWaitCallback.
*
* The AfterWaitCallback will be called even if the wakeup is spurious and the
* thread goes right back to waiting again. Of course the thread will call the
* BeforeWaitCallback once more before it goes to sleep in this situation.
*/
static constexpr size_t WAIT_CALLBACK_CLIENT_MAXMEM = 32;
using BeforeWaitCallback = void* (*)(uint8_t* memory);
using AfterWaitCallback = void (*)(void* cookie);
extern JS_PUBLIC_API void SetWaitCallback(JSRuntime* rt,
BeforeWaitCallback beforeWait,
AfterWaitCallback afterWait,
size_t requiredMemory);
} // namespace JS
#endif // js_WaitCallbacks_h
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