X39 – User talk

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{{warning|If you came here because you have been said to install an extension, be warned! Extensions are just like executables. They may contain viruses etc.. More on that, in the [[#FAQ]] section}}


__TOC__
=FAQ=
====Where to put Extensions?====
Arma will look at the following places to find your extension files:
* In your arma installation folder (for example: ''..\arma3\yourextension.dll'').
* In your current windows system folder.
* In your current windows folder.
* In all folders listen inside the PATH variable.
* In all loaded mods root folders (for example: ''..\arma3\@ModXYZ\yourextension.dll'').
At best, you place your extensions inside some mod folder and load it.
At worst, you just throw it where the arma executable is located.
====What are Extensions?====
Extensions are ''Dynamic Link Library'' (DLL) files written in, for example, C.
====What do i have to look out for?====
Extensions fall under the same rules as executable files.
They may require additional runtime libraries or cause the game to crash.
Worst case: They contain malicious code.
====How to know which extensions can be trusted?====
Theoretically, never trust anything! Including Arma.
Technically however, this would make a boring experience, though ... some may have fun with just the windows stock programs like the glorious texteditor notepad.
Thus a better rule is: If the are sources freely available, you probably can trust the extension.
Even if you cannot read the source code, chances are that somebody out there can and would find something odd.
That will not protect you! Even someone with good reputation might add malicious code, though he does not always needs to be aware of that fact as the developer himself might be infected already and another virus just writes itself in a DLL file.
Generally spoken, avoid extensions wherever you can.
====When i call the extension method, arma freezes====
This is most likely caused by the extension taking too much time.
Due to the nature of how actual code works, an extension cannot be suspended even if used from a spawn.
You should notify the developer of said extension about this freezing issue or use the extension less extensively.
====Can i join BattleEye protected servers with my extension?====
You should avoid joining BattleEye protected servers with extensions unless the mod author explicitly states that his extension is whitelisted by BattleEye.
====Can i use extensions in my mission?====
Yes, you can use extensions in your missions, but you should consider if it is worth it.
Using extensions requires that all hosts (servers and clients) which use the extension have it installed.
Important to know here: If only the server is using the extension, the clients do not need it.
Extensions are not packed into the mission pbo.
=Creating Extensions=
==Preamble==
Before we start, consider the following:
* Can what you're trying to achieve be done in pure sqf?
* Making an extension requires knowledge of a programming language. Are you capable of doing so?
* Why should a user trust you and use your extension. Is your reputation enough?
* Is it worth adding an extension for the feature you want to implement?
If the answer to any question was no, you probably should not proceed to create an extension but rather use plain SQF.
==Getting Started==
At first, we have to choose what language we want to use.
<!-- If you plan on adding another language, make sure you can provide code snippets for ALL examples required! -->
This wiki currently covers the following: '''C''', '''C++''', '''C#'''
Snippets contain code that may only work on windows.
===Preparations C#===
C# requires you to install additional dependencies to work out of the box.
The snippets in here all are using [https://www.nuget.org/packages/UnmanagedExports DllExport] ([https://github.com/3F/DllExport sources]) which can be installed using NuGet.
==Available Interfaces==
===C/C++===
<source lang="c">
//--- Engine called on extension load
__declspec (dllexport) void __stdcall RVExtensionVersion(char *output, int outputSize);
//--- STRING callExtension STRING
__declspec (dllexport) void __stdcall RVExtension(char *output, int outputSize, const char *function);
//--- STRING callExtension ARRAY
__declspec (dllexport) int __stdcall RVExtensionArgs(char *output, int outputSize, const char *function, const char **args, int argsCnt);
</source>
===C#===
<source lang="c#">
        /// <summary>
        /// Gets called when arma starts up and loads all extension.
        /// It's perfect to load in static objects in a seperate thread so that the extension doesn't needs any seperate initalization
        /// </summary>
        /// <param name="output">The string builder object that contains the result of the function</param>
        /// <param name="outputSize">The maximum size of bytes that can be returned</param>
#if WIN64
        [DllExport("RVExtensionVersion", CallingConvention = CallingConvention.Winapi)]
#else
        [DllExport("_RVExtensionVersion@8", CallingConvention = CallingConvention.Winapi)]
#endif
        public static void RvExtensionVersion(StringBuilder output, int outputSize) { }
        /// <summary>
        /// The entry point for the default callExtension command.
        /// </summary>
        /// <param name="output">The string builder object that contains the result of the function</param>
        /// <param name="outputSize">The maximum size of bytes that can be returned</param>
        /// <param name="function">The string argument that is used along with callExtension</param>
#if WIN64
        [DllExport("RVExtension", CallingConvention = CallingConvention.Winapi)]
#else
        [DllExport("_RVExtension@12", CallingConvention = CallingConvention.Winapi)]
#endif
        public static void RvExtension(StringBuilder output, int outputSize, [MarshalAs(UnmanagedType.LPStr)] string function) { }
        /// <summary>
        /// The entry point for the callExtensionArgs command.
        /// </summary>
        /// <param name="output">The string builder object that contains the result of the function</param>
        /// <param name="outputSize">The maximum size of bytes that can be returned</param>
        /// <param name="function">The string argument that is used along with callExtension</param>
        /// <param name="args">The args passed to callExtension as a string array</param>
        /// <param name="argsCount">The size of the string array args</param>
        /// <returns>The result code</returns>
#if WIN64
        [DllExport("RVExtensionArgs", CallingConvention = CallingConvention.Winapi)]
#else
        [DllExport("_RVExtensionArgs@20", CallingConvention = CallingConvention.Winapi)]
#endif
        public static int RvExtensionArgs(StringBuilder output, int outputSize, [MarshalAs(UnmanagedType.LPStr)] string function, [MarshalAs(UnmanagedType.LPArray, ArraySubType = UnmanagedType.LPStr, SizeParamIndex = 4)] string[] args, int argCount) { }
</source>

Latest revision as of 21:12, 18 November 2019

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