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authorDavid Walter Seikel2016-02-18 22:59:36 +1000
committerDavid Walter Seikel2016-02-18 22:59:36 +1000
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3<head> 3<head>
4</head> 4</head>
5<body bgcolor="black" text="white" alink="red" link="blue" vlink="purple"> 5<body bgcolor="black" text="white" alink="red" link="blue" vlink="purple">
6<p>LuaSL is a Lua based LSL scripting engine that will aim for LSL
7compatibility first, then adding Lua extensions. It aims to replace the
8woeful XEngine from OpenSim, and at a later stage, be the basis for a
9client side scripting engine.</p>
10<p>To compile this, you will need Enlightenment Foundation Libraries (EFL)
11installed in either /opt/e17 or /usr. These are typical places it get's
12installed in. You will also need flex. The rest of the dependencies
13are in the ../libraries directory.</p>
6<h1> write our own </h1> 14<h1> write our own </h1>
7<p>I had considered in the <a href="SledjHamr.html">SledjHamr</a> document writing a new script engine from scratch in Lua. This is what I wrote -</p> 15<p>I had considered in the <a href="SledjHamr.html">SledjHamr</a> document writing a new script engine from scratch in Lua. This is what I wrote -</p>
8<p>"I'd love to write a Lua implementation of LSL, I'm sure Alice would want to write a Scheme one."</p> 16<p>"I'd love to write a Lua implementation of LSL, I'm sure Alice would want to write a Scheme one."</p>
@@ -36,11 +44,120 @@
36<h2> Design </h2> 44<h2> Design </h2>
37<p>There are a number of ways we can go about this. Do we write the entire scripting engine in Lua, and only interface with C# for those things we really need to in order to get OpenSim to do in world stuff? Do we write a LSL to Lua translation layer that then compiles the Lua? The OpenSim engine I understand does that, translates LSL to C# then compiles that to .NET. Could we start with a higher level of Lua that interfaces with the existing LSL support functions in OpenSim? Can we even rely on those LSL support functions being a stable API? Should we start by experimenting with Lua's meta language features, see how close we can get it to look like LSL syntax? Perhaps concentrate on those parts of the job that don't require interfacing to OpenSim, and hope that SledjHamr can meet it half way to avoid the entire .NET thing?</p> 45<p>There are a number of ways we can go about this. Do we write the entire scripting engine in Lua, and only interface with C# for those things we really need to in order to get OpenSim to do in world stuff? Do we write a LSL to Lua translation layer that then compiles the Lua? The OpenSim engine I understand does that, translates LSL to C# then compiles that to .NET. Could we start with a higher level of Lua that interfaces with the existing LSL support functions in OpenSim? Can we even rely on those LSL support functions being a stable API? Should we start by experimenting with Lua's meta language features, see how close we can get it to look like LSL syntax? Perhaps concentrate on those parts of the job that don't require interfacing to OpenSim, and hope that SledjHamr can meet it half way to avoid the entire .NET thing?</p>
38<p>I choose to do those last two things - see how far I can get Lua to look like LSL, and concentrate on the parts that don't require interfacing to OpenSim, hoping that I can avoid the entire .NET thing.</p> 46<p>I choose to do those last two things - see how far I can get Lua to look like LSL, and concentrate on the parts that don't require interfacing to OpenSim, hoping that I can avoid the entire .NET thing.</p>
47
48<p>The basic design will be made up as I go along, but so far I have this -</p>
49
50<p>A parser parses an LSL script, validating it and reporting errors.</p>
51
52<p>A translator takes the result of the parse, and converts it into Lua
53source. Each LSL script becomes a Lua state. LSL states are handled as
54Lua tables, with each LSL state function being a table function in a
55common metatable. LL and OS functions are likely to be C or Lua
56functions. Careful testing should be done with LuaJIT FFI, sandboxing,
57and performance testing.</p>
58
59<p>The Lua source is compiled by the Lua compiler.</p>
60
61<p>LuaJIT is used as the Lua compiler, library, and runtime.</p>
62
63<p>Luaproc is used to start up operating system threads and hand Lua states
64between them. Luaproc messaging is also being used, but might need to
65change to edje messaging. Note - luaproc has been extensively rewritten
66for this project, mostly converting it to use EFL. That rewrite
67substantially shrunk the source code. Then it was all rewritten again
68to use EFL threads, and cooperative multitasking.</p>
69
70<p>THIS IS WHERE WE ARE RIGHT NOW.</p>
71
72<p>Should implement embedded Lua somehow. Probably the best thing to do is
73to have comments like -</p>
74
75<p>//Lua: local t = {1, 3, 42, x='something', 'something else}</p>
76/*Lua: print(t.x) */</p>
77
78<p>The LSL parser picks these up and stores them in the AST as Lua
79snippets, then the compiler output functions just inserts them in the
80Lua code it is generating. Obviously these Lua snippets can access the
81rest of the generated Lua code. They should also be able to access
82skang and thus do proper GUI stuff on viewers that support skang.</p>
83
84<p>Nails will be used to pump commands in and out of the LuaSL system.
85Incoming commands invoke LSL events via the LuaSL state metatable. LL
86and OS functions that impact the world will be converted to nails
87commands sent to the command pump.</p>
88
89<p>Initially, since this is the first thing being written, a nails command
90pump client needs to be installed into OpenSim's C# stuff. Though it
91might be possible to talk directly to ROBUST instead. Think I'll try
92the ROBUST route, see how far I can get. That's the general principle
93applying in all of this - try to avoid C# and see how for we can get.
94lol</p>
95
96<p>On the other hand, might be better to leverage the existing C#
97implementations of LSL functions, just to get things up and running
98quickly. To that end, a protocol involving exchanging snippets of Lua
99over a network socket has been developed, and the next step is to write
100the C# side. sigh</p>
101
102<p>A watchdog thread should be used to make sure no LuaSL script spends
103forever processing any event.</p>
104
105<p>Some form of serialization will need to be created for saving script
106state during shutdowns, passing script state to other threads /
107processes / computers. Apparently Lua is good at this.</p>
108
109<p>There will have to be a MySQL (and maybe SQLite) client in the system,
110so we can talk directly to the local sim database. Esskyuehl may be
111suitable, though it's still in the prototype stage.</p>
112
113<p>Email, HTTP, and XML-RPC might need to be dealt with by us. A ROBUST
114client will be needed to. Azy might be suitable, but it's also in
115prototype.</p>
116
117<p>An object is a file system directory, full of LSL scripts as text files,
118notecards as text files, animations as BVH (or later BVJ) files, etc.
119There will be some sort of metadata in place. This could be created by
120our own OpenSim compatible cache module.</p>
121
122
123<p>Test harness.</p>
124-------------</p>
125
126<p>I'll build a test harness. It will be based on EFL Edje Lua, with
127buttons for triggering LSL events, SL style dialogs, and other goodies.</p>
128
129<p>The initial goal will be to run standard MLP scripts. They have minimal
130interface to the world, and exercise quite a bit of the rest of LSL.
131They are also quite common, and sometimes responsible for a lot of the
132script running load.</p>
133
134<p>Later I should add stock standard OpenCollar scripts from SL. They are
135a bitch to get working under OpenSim, so would be good compatability
136tests.</p>
137
138<p>Various eina logging domains might be used to handle whisper, say, shout,
139etc.</p>
140
141<p>Performance testing will have to be done on 5000 scripts, to see how
142that compares against XEngine.</p>
143
144<p>The test harness became the love world server.</p>
145
146
147<p>TODO</p>
148<p>----</p>
149
150<p>Useful for limiting the amount of time scripts use -
151<p>https://groups.google.com/forum/#!topic/lua-alchemy-dev/3bDPk2aQ8FE</p>
152<p>http://stackoverflow.com/questions/862256/how-can-i-end-a-lua-thread-cleanly</p>
153
154
155
39<p>&nbsp;</p> 156<p>&nbsp;</p>
40<h1> onefangs implementation ideas </h1> 157<h1> onefangs implementation ideas </h1>
41<p>I'm gonna write an LSL script engine in Lua and C. At least initially, I'll pretend I can use SledjHamr instead of OpenSim, and see how far I get. The source is at <a href="https://github.com/onefang/SledjHamr">https://github.com/onefang/SledjHamr</a> on the experimental branch.</p> 158<p>I'm gonna write an LSL script engine in Lua and C. At least initially, I'll pretend I can use SledjHamr instead of OpenSim, and see how far I get. The source is at <a href="https://github.com/onefang/SledjHamr">https://github.com/onefang/SledjHamr</a> on the experimental branch.</p>
42<p>&nbsp;</p> 159<p>&nbsp;</p>
43<h2> You’re in a maze of twisty little quirks, all different. </h2> 160<h2> You're in a maze of twisty little quirks, all different. </h2>
44<p>LSL is known for being more quirks than features. Some of the quirks are just limitations that we can get rid of. Some we will have to replicate just to be compatible. OpenSim adds it's own quirks on top of those, but one of the points of doing this is to avoid that particular set of quirks. I'll create two variations, using the first line comment hack OpenSim invented to choose between them. The default is to use the quirky one, where an effort is made to replicate the full quirkiness of LSL. The other choice has no quirks at all, and even lets Lua features be mixed in. This Lua flavoured LSL will be the first one to work on, as it will be a lot easier.</p> 161<p>LSL is known for being more quirks than features. Some of the quirks are just limitations that we can get rid of. Some we will have to replicate just to be compatible. OpenSim adds it's own quirks on top of those, but one of the points of doing this is to avoid that particular set of quirks. I'll create two variations, using the first line comment hack OpenSim invented to choose between them. The default is to use the quirky one, where an effort is made to replicate the full quirkiness of LSL. The other choice has no quirks at all, and even lets Lua features be mixed in. This Lua flavoured LSL will be the first one to work on, as it will be a lot easier.</p>
45<p>&nbsp;</p> 162<p>&nbsp;</p>
46<h2> Making Lua look like LSL </h2> 163<h2> Making Lua look like LSL </h2>
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