/home/mrjunejune/zenbu: third_party/luajit/doc/ext

annotate third_party/luajit/doc/ext_ffi.html @ 210:0abed117e623

Updated manifest color.

author	MrJuneJune <me@mrjunejune.com>
date	Sun, 15 Feb 2026 15:47:38 -0800
parents	94705b5986b3
children

rev	line source
178 94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	1 <!DOCTYPE html>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	2 <html>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	3 <head>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	4 <title>FFI Library</title>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	5 <meta charset="utf-8">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	6 <meta name="Copyright" content="Copyright (C) 2005-2023">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	7 <meta name="Language" content="en">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	8 <link rel="stylesheet" type="text/css" href="bluequad.css" media="screen">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	9 <link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	10 </head>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	11 <body>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	12 <div id="site">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	13 <a href="https://luajit.org"><span>Lua<span id="logo">JIT</span></span></a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	14 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	15 <div id="head">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	16 <h1>FFI Library</h1>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	17 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	18 <div id="nav">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	19 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	20 <a href="luajit.html">LuaJIT</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	21 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	22 <a href="https://luajit.org/download.html">Download <span class="ext">»</span></a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	23 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	24 <a href="install.html">Installation</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	25 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	26 <a href="running.html">Running</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	27 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	28 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	29 <a href="extensions.html">Extensions</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	30 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	31 <a class="current" href="ext_ffi.html">FFI Library</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	32 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	33 <a href="ext_ffi_tutorial.html">FFI Tutorial</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	34 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	35 <a href="ext_ffi_api.html">ffi.* API</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	36 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	37 <a href="ext_ffi_semantics.html">FFI Semantics</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	38 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	39 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	40 <a href="ext_buffer.html">String Buffers</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	41 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	42 <a href="ext_jit.html">jit.* Library</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	43 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	44 <a href="ext_c_api.html">Lua/C API</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	45 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	46 <a href="ext_profiler.html">Profiler</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	47 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	48 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	49 <a href="https://luajit.org/status.html">Status <span class="ext">»</span></a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	50 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	51 <a href="https://luajit.org/faq.html">FAQ <span class="ext">»</span></a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	52 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	53 <a href="https://luajit.org/list.html">Mailing List <span class="ext">»</span></a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	54 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	55 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	56 <div id="main">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	57 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	58
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	59 The FFI library allows <b>calling external C functions</b> and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	60 <b>using C data structures</b> from pure Lua code.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	61
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	62 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	63 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	64
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	65 The FFI library largely obviates the need to write tedious manual
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	66 Lua/C bindings in C. No need to learn a separate binding language
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	67 — <b>it parses plain C declarations!</b> These can be
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	68 cut-n-pasted from C header files or reference manuals. It's up to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	69 the task of binding large libraries without the need for dealing with
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	70 fragile binding generators.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	71
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	72 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	73 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	74 The FFI library is tightly integrated into LuaJIT (it's not available
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	75 as a separate module). The code generated by the JIT-compiler for
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	76 accesses to C data structures from Lua code is on par with the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	77 code a C compiler would generate. Calls to C functions can
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	78 be inlined in JIT-compiled code, unlike calls to functions bound via
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	79 the classic Lua/C API.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	80 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	81 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	82 This page gives a short introduction to the usage of the FFI library.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	83 <em>Please use the FFI sub-topics in the navigation bar to learn more.</em>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	84 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	85
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	86 <h2 id="call">Motivating Example: Calling External C Functions</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	87 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	88 It's really easy to call an external C library function:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	89 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	90 <pre class="code mark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	91 <span class="codemark">①
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	92 ②
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	93
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	94
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	95 ③</span>local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	96 ffi.cdef[[
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	97 <span style="color:#00a000;">int printf(const char *fmt, ...);</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	98 ]]
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	99 ffi.C.printf("Hello %s!", "world")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	100 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	101 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	102 So, let's pick that apart:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	103 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	104 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	105 <span class="mark">①</span> Load the FFI library.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	106 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	107 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	108 <span class="mark">②</span> Add a C declaration
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	109 for the function. The part inside the double-brackets (in green) is
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	110 just standard C syntax.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	111 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	112 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	113 <span class="mark">③</span> Call the named
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	114 C function — Yes, it's that simple!
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	115 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	116 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	117 Actually, what goes on behind the scenes is far from simple: <span
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	118 style="color:#4040c0;">③</span> makes use of the standard
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	119 C library namespace <tt>ffi.C</tt>. Indexing this namespace with
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	120 a symbol name (<tt>"printf"</tt>) automatically binds it to the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	121 standard C library. The result is a special kind of object which,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	122 when called, runs the <tt>printf</tt> function. The arguments passed
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	123 to this function are automatically converted from Lua objects to the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	124 corresponding C types.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	125 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	126 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	127 Ok, so maybe the use of <tt>printf()</tt> wasn't such a spectacular
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	128 example. You could have done that with <tt>io.write()</tt> and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	129 <tt>string.format()</tt>, too. But you get the idea ...
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	130 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	131 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	132 So here's something to pop up a message box on Windows:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	133 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	134 <pre class="code">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	135 local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	136 ffi.cdef[[
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	137 <span style="color:#00a000;">int MessageBoxA(void w, const char txt, const char *cap, int type);</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	138 ]]
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	139 ffi.C.MessageBoxA(nil, "Hello world!", "Test", 0)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	140 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	141 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	142 Bing! Again, that was far too easy, no?
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	143 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	144 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	145 Compare this with the effort required to bind that function using the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	146 classic Lua/C API: create an extra C file, add a C function
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	147 that retrieves and checks the argument types passed from Lua and calls
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	148 the actual C function, add a list of module functions and their
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	149 names, add a <tt>luaopen_*</tt> function and register all module
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	150 functions, compile and link it into a shared library (DLL), move it to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	151 the proper path, add Lua code that loads the module aaaand ... finally
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	152 call the binding function. Phew!
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	153 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	154
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	155 <h2 id="cdata">Motivating Example: Using C Data Structures</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	156 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	157 The FFI library allows you to create and access C data
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	158 structures. Of course, the main use for this is for interfacing with
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	159 C functions. But they can be used stand-alone, too.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	160 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	161 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	162 Lua is built upon high-level data types. They are flexible, extensible
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	163 and dynamic. That's why we all love Lua so much. Alas, this can be
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	164 inefficient for certain tasks, where you'd really want a low-level
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	165 data type. E.g. a large array of a fixed structure needs to be
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	166 implemented with a big table holding lots of tiny tables. This imposes
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	167 both a substantial memory overhead as well as a performance overhead.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	168 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	169 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	170 Here's a sketch of a library that operates on color images, plus a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	171 simple benchmark. First, the plain Lua version:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	172 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	173 <pre class="code">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	174 local floor = math.floor
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	175
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	176 local function image_ramp_green(n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	177 local img = {}
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	178 local f = 255/(n-1)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	179 for i=1,n do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	180 img[i] = { red = 0, green = floor((i-1)*f), blue = 0, alpha = 255 }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	181 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	182 return img
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	183 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	184
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	185 local function image_to_gray(img, n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	186 for i=1,n do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	187 local y = floor(0.3img[i].red + 0.59img[i].green + 0.11*img[i].blue)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	188 img[i].red = y; img[i].green = y; img[i].blue = y
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	189 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	190 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	191
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	192 local N = 400*400
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	193 local img = image_ramp_green(N)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	194 for i=1,1000 do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	195 image_to_gray(img, N)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	196 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	197 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	198 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	199 This creates a table with 160.000 pixels, each of which is a table
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	200 holding four number values in the range of 0-255. First, an image with
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	201 a green ramp is created (1D for simplicity), then the image is
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	202 converted to grayscale 1000 times. Yes, that's silly, but I was in
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	203 need of a simple example ...
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	204 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	205 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	206 And here's the FFI version. The modified parts have been marked in
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	207 bold:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	208 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	209 <pre class="code mark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	210 <span class="codemark">①
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	211
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	212
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	213
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	214
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	215
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	216 ②
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	217
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	218 ③
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	219 ④
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	220
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	221
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	222
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	223
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	224
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	225
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	226 ③
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	227 ⑤</span><b>local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	228 ffi.cdef[[
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	229 </b><span style="color:#00a000;">typedef struct { uint8_t red, green, blue, alpha; } rgba_pixel;</span><b>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	230 ]]</b>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	231
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	232 local function image_ramp_green(n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	233 <b>local img = ffi.new("rgba_pixel[?]", n)</b>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	234 local f = 255/(n-1)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	235 for i=<b>0,n-1</b> do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	236 <b>img[i].green = i*f</b>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	237 <b>img[i].alpha = 255</b>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	238 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	239 return img
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	240 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	241
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	242 local function image_to_grey(img, n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	243 for i=<b>0,n-1</b> do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	244 local y = <b>0.3img[i].red + 0.59img[i].green + 0.11*img[i].blue</b>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	245 img[i].red = y; img[i].green = y; img[i].blue = y
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	246 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	247 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	248
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	249 local N = 400*400
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	250 local img = image_ramp_green(N)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	251 for i=1,1000 do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	252 image_to_grey(img, N)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	253 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	254 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	255 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	256 Ok, so that wasn't too difficult:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	257 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	258 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	259 <span class="mark">①</span> First, load the FFI
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	260 library and declare the low-level data type. Here we choose a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	261 <tt>struct</tt> which holds four byte fields, one for each component
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	262 of a 4x8 bit RGBA pixel.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	263 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	264 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	265 <span class="mark">②</span> Creating the data
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	266 structure with <tt>ffi.new()</tt> is straightforward — the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	267 <tt>'?'</tt> is a placeholder for the number of elements of a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	268 variable-length array.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	269 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	270 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	271 <span class="mark">③</span> C arrays are
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	272 zero-based, so the indexes have to run from <tt>0</tt> to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	273 <tt>n-1</tt>. One might want to allocate one more element instead to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	274 simplify converting legacy code.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	275 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	276 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	277 <span class="mark">④</span> Since <tt>ffi.new()</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	278 zero-fills the array by default, we only need to set the green and the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	279 alpha fields.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	280 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	281 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	282 <span class="mark">⑤</span> The calls to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	283 <tt>math.floor()</tt> can be omitted here, because floating-point
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	284 numbers are already truncated towards zero when converting them to an
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	285 integer. This happens implicitly when the number is stored in the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	286 fields of each pixel.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	287 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	288 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	289 Now let's have a look at the impact of the changes: first, memory
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	290 consumption for the image is down from 22 Megabytes to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	291 640 Kilobytes (4004004 bytes). That's a factor of 35x less! So,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	292 yes, tables do have a noticeable overhead. BTW: The original program
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	293 would consume 40 Megabytes in plain Lua (on x64).
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	294 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	295 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	296 Next, performance: the pure Lua version runs in 9.57 seconds (52.9
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	297 seconds with the Lua interpreter) and the FFI version runs in 0.48
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	298 seconds on my machine (YMMV). That's a factor of 20x faster (110x
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	299 faster than the Lua interpreter).
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	300 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	301 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	302 The avid reader may notice that converting the pure Lua version over
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	303 to use array indexes for the colors (<tt>[1]</tt> instead of
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	304 <tt>.red</tt>, <tt>[2]</tt> instead of <tt>.green</tt> etc.) ought to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	305 be more compact and faster. This is certainly true (by a factor of
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	306 ~1.7x). Switching to a struct-of-arrays would help, too.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	307 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	308 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	309 However, the resulting code would be less idiomatic and rather
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	310 error-prone. And it still doesn't get even close to the performance of
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	311 the FFI version of the code. Also, high-level data structures cannot
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	312 be easily passed to other C functions, especially I/O functions,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	313 without undue conversion penalties.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	314 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	315 <br class="flush">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	316 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	317 <div id="foot">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	318 <hr class="hide">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	319 Copyright © 2005-2023
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	320 <span class="noprint">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	321 ·
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	322 <a href="contact.html">Contact</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	323 </span>
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