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/* Copyright (C) 2024 Wildfire Games.
* This file is part of 0 A.D.
*
* 0 A.D. is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 2 of the License, or
* (at your option) any later version.
*
* 0 A.D. is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef INCLUDED_SCRIPTCONTEXT
#define INCLUDED_SCRIPTCONTEXT
#include "ScriptTypes.h"
#include "ScriptExtraHeaders.h"
#include <list>
// Those are minimal defaults. The runtime for the main game is larger and GCs upon a larger growth.
constexpr int DEFAULT_CONTEXT_SIZE = 16 * 1024 * 1024;
constexpr uint32_t DEFAULT_HEAP_GROWTH_BYTES_GCTRIGGER = 2 * 1024 * 1024;
namespace Script
{
class JobQueue;
}
/**
* Abstraction around a SpiderMonkey JSContext.
*
* A single ScriptContext, with the associated context,
* should only be used on a single thread.
*
* (One means to share data between threads and contexts is to create
* a Script::StructuredClone.)
*/
class ScriptContext
{
public:
ScriptContext(int contextSize, uint32_t heapGrowthBytesGCTrigger);
~ScriptContext();
/**
* Returns a context, in which any number of ScriptInterfaces compartments can live.
* Each context should only ever be used on a single thread.
* @param parentContext Parent context from the parent thread, with which we share some thread-safe data
* @param contextSize Maximum size in bytes of the new context
* @param heapGrowthBytesGCTrigger Size in bytes of cumulated allocations after which a GC will be triggered
*/
static std::shared_ptr<ScriptContext> CreateContext(
int contextSize = DEFAULT_CONTEXT_SIZE,
uint32_t heapGrowthBytesGCTrigger = DEFAULT_HEAP_GROWTH_BYTES_GCTRIGGER);
/**
* MaybeIncrementalGC checks if running a GC is worth the time that will take.
* The logic is custom as Spidermonkey tends to assume 'idle time' will exist,
* which is a thing in websites but not really in 0 A.D.
* This can have a few behaviours:
* - doing nothing
* - starting a new incremental GC
* - running a GC slice
* - finishing the incremental GC
* For details, check the SM doc in e.g. GC.cpp and GCapi.cpp
*/
void MaybeIncrementalGC();
/**
* Does a non-incremental, shrinking GC.
* A shrinking GC dumps JIT code and tries to defragment memory.
*/
void ShrinkingGC();
/**
* This is used to keep track of realms which should be prepared for a GC.
*/
void RegisterRealm(JS::Realm* realm);
void UnRegisterRealm(JS::Realm* realm);
/**
* Runs the promise continuation.
* On contexts where promises can be used this function has to be
* called.
* This function has to be called frequently.
*/
void RunJobs();
/**
* GetGeneralJSContext returns the context without starting a GC request and without
* entering any compartment. It should only be used in specific situations, such as
* creating a new compartment, or when initializing a persistent rooted.
* If you need the compartmented context of a ScriptInterface, you should create a
* ScriptRequest and use the context from that.
*/
JSContext* GetGeneralJSContext() const { return m_cx; }
private:
JSContext* m_cx;
const std::unique_ptr<Script::JobQueue> m_JobQueue;
void PrepareZonesForIncrementalGC() const;
std::list<JS::Realm*> m_Realms;
int m_ContextSize;
uint32_t m_HeapGrowthBytesGCTrigger;
uint32_t m_LastGCBytes{0};
};
// Using a global object for the context is a workaround until Simulation, AI, etc,
// use their own threads and also their own contexts.
extern thread_local std::shared_ptr<ScriptContext> g_ScriptContext;
#endif // INCLUDED_SCRIPTCONTEXT
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