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

annotate third_party/luajit/doc/ext_ffi_tutorial.html @ 195:f8f5004a920a

Merging back hg-web-tip

author	MrJuneJune <me@mrjunejune.com>
date	Tue, 27 Jan 2026 06:51:44 -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 Tutorial</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 <style type="text/css">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	11 table.idiomtable { font-size: 90%; line-height: 1.2; }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	12 table.idiomtable tt { font-size: 100%; }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	13 table.idiomtable td { vertical-align: top; }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	14 tr.idiomhead td { font-weight: bold; }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	15 td.idiomlua b { font-weight: normal; color: #2142bf; }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	16 </style>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	17 </head>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	18 <body>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	19 <div id="site">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	20 <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	21 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	22 <div id="head">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	23 <h1>FFI Tutorial</h1>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	24 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	25 <div id="nav">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	26 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	27 <a href="luajit.html">LuaJIT</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	28 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	29 <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	30 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	31 <a href="install.html">Installation</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	32 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	33 <a href="running.html">Running</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	34 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	35 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	36 <a href="extensions.html">Extensions</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	37 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	38 <a href="ext_ffi.html">FFI Library</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	39 <ul><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	40 <a class="current" href="ext_ffi_tutorial.html">FFI Tutorial</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_ffi_api.html">ffi.* API</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_ffi_semantics.html">FFI Semantics</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	45 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	46 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	47 <a href="ext_buffer.html">String Buffers</a>
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="ext_jit.html">jit.* Library</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="ext_c_api.html">Lua/C API</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="ext_profiler.html">Profiler</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 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	56 <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	57 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	58 <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	59 </li><li>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	60 <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	61 </li></ul>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	62 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	63 <div id="main">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	64 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	65 This page is intended to give you an overview of the features of the FFI
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	66 library by presenting a few use cases and guidelines.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	67 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	68 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	69 This page makes no attempt to explain all of the FFI library, though.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	70 You'll want to have a look at the <a href="ext_ffi_api.html">ffi.* API
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	71 function reference</a> and the <a href="ext_ffi_semantics.html">FFI
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	72 semantics</a> to learn more.
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
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	75 <h2 id="load">Loading the FFI Library</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	76 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	77 The FFI library is built into LuaJIT by default, but it's not loaded
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	78 and initialized by default. The suggested way to use the FFI library
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	79 is to add the following to the start of every Lua file that needs one
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	80 of its functions:
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 <pre class="code">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	83 local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	84 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	85 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	86 Please note, this doesn't define an <tt>ffi</tt> variable in the table
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	87 of globals — you really need to use the local variable. The
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	88 <tt>require</tt> function ensures the library is only loaded once.
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 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	91 Note: If you want to experiment with the FFI from the interactive prompt
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	92 of the command line executable, omit the <tt>local</tt>, as it doesn't
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	93 preserve local variables across lines.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	94 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	95
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	96 <h2 id="sleep">Accessing Standard System Functions</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	97 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	98 The following code explains how to access standard system functions.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	99 We slowly print two lines of dots by sleeping for 10 milliseconds
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	100 after each dot:
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 <pre class="code mark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	103 <span class="codemark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	104 ①
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	105
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	106
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	107
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	108
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	109
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	110 ②
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	111 ③
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	112 ④
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	113
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	114
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	115
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	116 ⑤
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	117
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	118
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	119
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	120
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	121
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	122 ⑥</span>local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	123 ffi.cdef[[
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	124 <span style="color:#00a000;">void Sleep(int ms);
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	125 int poll(struct pollfd *fds, unsigned long nfds, int timeout);</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	126 ]]
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	127
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	128 local sleep
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	129 if ffi.os == "Windows" then
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	130 function sleep(s)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	131 ffi.C.Sleep(s*1000)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	132 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	133 else
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	134 function sleep(s)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	135 ffi.C.poll(nil, 0, s*1000)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	136 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	137 end
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 for i=1,160 do
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	140 io.write("."); io.flush()
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	141 sleep(0.01)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	142 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	143 io.write("\n")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	144 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	145 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	146 Here's the step-by-step explanation:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	147 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	148 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	149 <span class="mark">①</span> This defines the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	150 C library functions we're going to use. The part inside the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	151 double-brackets (in green) is just standard C syntax. You can
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	152 usually get this info from the C header files or the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	153 documentation provided by each C library or C compiler.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	154 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	155 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	156 <span class="mark">②</span> The difficulty we're
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	157 facing here, is that there are different standards to choose from.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	158 Windows has a simple <tt>Sleep()</tt> function. On other systems there
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	159 are a variety of functions available to achieve sub-second sleeps, but
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	160 with no clear consensus. Thankfully <tt>poll()</tt> can be used for
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	161 this task, too, and it's present on most non-Windows systems. The
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	162 check for <tt>ffi.os</tt> makes sure we use the Windows-specific
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	163 function only on Windows systems.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	164 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	165 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	166 <span class="mark">③</span> Here we're wrapping the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	167 call to the C function in a Lua function. This isn't strictly
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	168 necessary, but it's helpful to deal with system-specific issues only
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	169 in one part of the code. The way we're wrapping it ensures the check
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	170 for the OS is only done during initialization and not for every call.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	171 </p>
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 <span class="mark">④</span> A more subtle point is
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	174 that we defined our <tt>sleep()</tt> function (for the sake of this
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	175 example) as taking the number of seconds, but accepting fractional
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	176 seconds. Multiplying this by 1000 gets us milliseconds, but that still
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	177 leaves it a Lua number, which is a floating-point value. Alas, the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	178 <tt>Sleep()</tt> function only accepts an integer value. Luckily for
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	179 us, the FFI library automatically performs the conversion when calling
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	180 the function (truncating the FP value towards zero, like in C).
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	181 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	182 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	183 Some readers will notice that <tt>Sleep()</tt> is part of
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	184 <tt>KERNEL32.DLL</tt> and is also a <tt>stdcall</tt> function. So how
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	185 can this possibly work? The FFI library provides the <tt>ffi.C</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	186 default C library namespace, which allows calling functions from
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	187 the default set of libraries, like a C compiler would. Also, the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	188 FFI library automatically detects <tt>stdcall</tt> functions, so you
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	189 don't need to declare them as such.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	190 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	191 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	192 <span class="mark">⑤</span> The <tt>poll()</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	193 function takes a couple more arguments we're not going to use. You can
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	194 simply use <tt>nil</tt> to pass a <tt>NULL</tt> pointer and <tt>0</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	195 for the <tt>nfds</tt> parameter. Please note, that the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	196 number <tt>0</tt> <em>does not convert to a pointer value</em>,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	197 unlike in C++. You really have to pass pointers to pointer arguments
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	198 and numbers to number arguments.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	199 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	200 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	201 The page on <a href="ext_ffi_semantics.html">FFI semantics</a> has all
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	202 of the gory details about
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	203 <a href="ext_ffi_semantics.html#convert">conversions between Lua
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	204 objects and C types</a>. For the most part you don't have to deal
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	205 with this, as it's performed automatically and it's carefully designed
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	206 to bridge the semantic differences between Lua and C.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	207 </p>
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 <span class="mark">⑥</span> Now that we have defined
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	210 our own <tt>sleep()</tt> function, we can just call it from plain Lua
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	211 code. That wasn't so bad, huh? Turning these boring animated dots into
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	212 a fascinating best-selling game is left as an exercise for the reader.
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 </p>
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 <h2 id="zlib">Accessing the zlib Compression Library</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	217 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	218 The following code shows how to access the <a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	219 href="https://zlib.net/"><span class="ext">»</span> zlib</a> compression library from Lua code.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	220 We'll define two convenience wrapper functions that take a string and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	221 compress or uncompress it to another string:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	222 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	223 <pre class="code mark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	224 <span class="codemark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	225 ①
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	226
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	227
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	228
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	229
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	230
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 ②
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	233
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	234
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	235 ③
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	236
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	237 ④
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	238
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	239
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	240 ⑤
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
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	243 ⑥
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	244
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	245
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	246
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	247
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
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	250
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	251 ⑦</span>local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	252 ffi.cdef[[
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	253 <span style="color:#00a000;">unsigned long compressBound(unsigned long sourceLen);
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	254 int compress2(uint8_t dest, unsigned long destLen,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	255 const uint8_t *source, unsigned long sourceLen, int level);
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	256 int uncompress(uint8_t dest, unsigned long destLen,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	257 const uint8_t *source, unsigned long sourceLen);</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	258 ]]
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	259 local zlib = ffi.load(ffi.os == "Windows" and "zlib1" or "z")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	260
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	261 local function compress(txt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	262 local n = zlib.compressBound(#txt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	263 local buf = ffi.new("uint8_t[?]", n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	264 local buflen = ffi.new("unsigned long[1]", n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	265 local res = zlib.compress2(buf, buflen, txt, #txt, 9)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	266 assert(res == 0)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	267 return ffi.string(buf, buflen[0])
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	268 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	269
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	270 local function uncompress(comp, n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	271 local buf = ffi.new("uint8_t[?]", n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	272 local buflen = ffi.new("unsigned long[1]", n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	273 local res = zlib.uncompress(buf, buflen, comp, #comp)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	274 assert(res == 0)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	275 return ffi.string(buf, buflen[0])
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	276 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	277
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	278 -- Simple test code.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	279 local txt = string.rep("abcd", 1000)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	280 print("Uncompressed size: ", #txt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	281 local c = compress(txt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	282 print("Compressed size: ", #c)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	283 local txt2 = uncompress(c, #txt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	284 assert(txt2 == txt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	285 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	286 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	287 Here's the step-by-step explanation:
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 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	290 <span class="mark">①</span> This defines some of the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	291 C functions provided by zlib. For the sake of this example, some
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	292 type indirections have been reduced and it uses the predefined
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	293 fixed-size integer types, while still adhering to the zlib API/ABI.
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 <span class="mark">②</span> This loads the zlib shared
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	297 library. On POSIX systems, it's named <tt>libz.so</tt> and usually
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	298 comes pre-installed. Since <tt>ffi.load()</tt> automatically adds any
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	299 missing standard prefixes/suffixes, we can simply load the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	300 <tt>"z"</tt> library. On Windows it's named <tt>zlib1.dll</tt> and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	301 you'll have to download it first from the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	302 <a href="https://zlib.net/"><span class="ext">»</span> zlib site</a>. The check for
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	303 <tt>ffi.os</tt> makes sure we pass the right name to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	304 <tt>ffi.load()</tt>.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	305 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	306 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	307 <span class="mark">③</span> First, the maximum size of
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	308 the compression buffer is obtained by calling the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	309 <tt>zlib.compressBound</tt> function with the length of the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	310 uncompressed string. The next line allocates a byte buffer of this
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	311 size. The <tt>[?]</tt> in the type specification indicates a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	312 variable-length array (VLA). The actual number of elements of this
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	313 array is given as the 2nd argument to <tt>ffi.new()</tt>.
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 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	316 <span class="mark">④</span> This may look strange at
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	317 first, but have a look at the declaration of the <tt>compress2</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	318 function from zlib: the destination length is defined as a pointer!
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	319 This is because you pass in the maximum buffer size and get back the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	320 actual length that was used.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	321 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	322 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	323 In C you'd pass in the address of a local variable
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	324 (<tt>&buflen</tt>). But since there's no address-of operator in
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	325 Lua, we'll just pass in a one-element array. Conveniently, it can be
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	326 initialized with the maximum buffer size in one step. Calling the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	327 actual <tt>zlib.compress2</tt> function is then straightforward.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	328 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	329 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	330 <span class="mark">⑤</span> We want to return the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	331 compressed data as a Lua string, so we'll use <tt>ffi.string()</tt>.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	332 It needs a pointer to the start of the data and the actual length. The
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	333 length has been returned in the <tt>buflen</tt> array, so we'll just
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	334 get it from there.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	335 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	336 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	337 Note that since the function returns now, the <tt>buf</tt> and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	338 <tt>buflen</tt> variables will eventually be garbage collected. This
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	339 is fine, because <tt>ffi.string()</tt> has copied the contents to a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	340 newly created (interned) Lua string. If you plan to call this function
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	341 lots of times, consider reusing the buffers and/or handing back the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	342 results in buffers instead of strings. This will reduce the overhead
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	343 for garbage collection and string interning.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	344 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	345 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	346 <span class="mark">⑥</span> The <tt>uncompress</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	347 functions does the exact opposite of the <tt>compress</tt> function.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	348 The compressed data doesn't include the size of the original string,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	349 so this needs to be passed in. Otherwise, no surprises here.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	350 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	351 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	352 <span class="mark">⑦</span> The code, that makes use
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	353 of the functions we just defined, is just plain Lua code. It doesn't
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	354 need to know anything about the LuaJIT FFI — the convenience
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	355 wrapper functions completely hide it.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	356 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	357 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	358 One major advantage of the LuaJIT FFI is that you are now able to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	359 write those wrappers <em>in Lua</em>. And at a fraction of the time it
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	360 would cost you to create an extra C module using the Lua/C API.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	361 Many of the simpler C functions can probably be used directly
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	362 from your Lua code, without any wrappers.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	363 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	364 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	365 Side note: the zlib API uses the <tt>long</tt> type for passing
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	366 lengths and sizes around. But all those zlib functions actually only
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	367 deal with 32 bit values. This is an unfortunate choice for a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	368 public API, but may be explained by zlib's history — we'll just
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	369 have to deal with it.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	370 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	371 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	372 First, you should know that a <tt>long</tt> is a 64 bit type e.g.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	373 on POSIX/x64 systems, but a 32 bit type on Windows/x64 and on
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	374 32 bit systems. Thus a <tt>long</tt> result can be either a plain
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	375 Lua number or a boxed 64 bit integer cdata object, depending on
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	376 the target system.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	377 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	378 <p style="font-size: 8pt;">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	379 Ok, so the <tt>ffi.*</tt> functions generally accept cdata objects
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	380 wherever you'd want to use a number. That's why we get a away with
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	381 passing <tt>n</tt> to <tt>ffi.string()</tt> above. But other Lua
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	382 library functions or modules don't know how to deal with this. So for
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	383 maximum portability, one needs to use <tt>tonumber()</tt> on returned
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	384 <tt>long</tt> results before passing them on. Otherwise the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	385 application might work on some systems, but would fail in a POSIX/x64
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	386 environment.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	387 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	388
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	389 <h2 id="metatype">Defining Metamethods for a C Type</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	390 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	391 The following code explains how to define metamethods for a C type.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	392 We define a simple point type and add some operations to it:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	393 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	394 <pre class="code mark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	395 <span class="codemark">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	396 ①
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	397
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	398
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	399
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	400 ②
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	401
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	402 ③
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	403
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	404 ④
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	405
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	406
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	407
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	408 ⑤
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	409
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	410 ⑥</span>local ffi = require("ffi")
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	411 ffi.cdef[[
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	412 <span style="color:#00a000;">typedef struct { double x, y; } point_t;</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	413 ]]
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	414
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	415 local point
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	416 local mt = {
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	417 __add = function(a, b) return point(a.x+b.x, a.y+b.y) end,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	418 __len = function(a) return math.sqrt(a.xa.x + a.ya.y) end,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	419 __index = {
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	420 area = function(a) return a.xa.x + a.ya.y end,
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	421 },
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	422 }
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	423 point = ffi.metatype("point_t", mt)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	424
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	425 local a = point(3, 4)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	426 print(a.x, a.y) --> 3 4
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	427 print(#a) --> 5
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	428 print(a:area()) --> 25
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	429 local b = a + point(0.5, 8)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	430 print(#b) --> 12.5
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	431 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	432 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	433 Here's the step-by-step explanation:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	434 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	435 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	436 <span class="mark">①</span> This defines the C type for a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	437 two-dimensional point object.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	438 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	439 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	440 <span class="mark">②</span> We have to declare the variable
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	441 holding the point constructor first, because it's used inside of a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	442 metamethod.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	443 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	444 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	445 <span class="mark">③</span> Let's define an <tt>__add</tt>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	446 metamethod which adds the coordinates of two points and creates a new
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	447 point object. For simplicity, this function assumes that both arguments
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	448 are points. But it could be any mix of objects, if at least one operand
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	449 is of the required type (e.g. adding a point plus a number or vice
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	450 versa). Our <tt>__len</tt> metamethod returns the distance of a point to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	451 the origin.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	452 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	453 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	454 <span class="mark">④</span> If we run out of operators, we can
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	455 define named methods, too. Here, the <tt>__index</tt> table defines an
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	456 <tt>area</tt> function. For custom indexing needs, one might want to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	457 define <tt>__index</tt> and <tt>__newindex</tt> <em>functions</em> instead.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	458 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	459 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	460 <span class="mark">⑤</span> This associates the metamethods with
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	461 our C type. This only needs to be done once. For convenience, a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	462 constructor is returned by
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	463 <a href="ext_ffi_api.html#ffi_metatype"><tt>ffi.metatype()</tt></a>.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	464 We're not required to use it, though. The original C type can still
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	465 be used e.g. to create an array of points. The metamethods automatically
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	466 apply to any and all uses of this type.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	467 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	468 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	469 Please note, that the association with a metatable is permanent and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	470 <b>the metatable must not be modified afterwards!</b> Ditto for the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	471 <tt>__index</tt> table.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	472 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	473 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	474 <span class="mark">⑥</span> Here are some simple usage examples
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	475 for the point type and their expected results. The predefined
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	476 operations (such as <tt>a.x</tt>) can be freely mixed with the newly
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	477 defined metamethods. Note that <tt>area</tt> is a method and must be
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	478 called with the Lua syntax for methods: <tt>a:area()</tt>, not
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	479 <tt>a.area()</tt>.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	480 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	481 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	482 The C type metamethod mechanism is most useful when used in
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	483 conjunction with C libraries that are written in an object-oriented
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	484 style. Creators return a pointer to a new instance, and methods take an
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	485 instance pointer as the first argument. Sometimes you can just point
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	486 <tt>__index</tt> to the library namespace and <tt>__gc</tt> to the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	487 destructor and you're done. But often enough you'll want to add
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	488 convenience wrappers, e.g. to return actual Lua strings or when
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	489 returning multiple values.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	490 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	491 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	492 Some C libraries only declare instance pointers as an opaque
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	493 <tt>void *</tt> type. In this case you can use a fake type for all
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	494 declarations, e.g. a pointer to a named (incomplete) struct will do:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	495 <tt>typedef struct foo_type *foo_handle</tt>. The C side doesn't
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	496 know what you declare with the LuaJIT FFI, but as long as the underlying
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	497 types are compatible, everything still works.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	498 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	499
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	500 <h2 id="idioms">Translating C Idioms</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	501 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	502 Here's a list of common C idioms and their translation to the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	503 LuaJIT FFI:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	504 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	505 <table class="idiomtable">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	506 <tr class="idiomhead">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	507 <td class="idiomdesc">Idiom</td>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	508 <td class="idiomc">C code</td>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	509 <td class="idiomlua">Lua code</td>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	510 </tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	511 <tr class="odd separate">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	512 <td class="idiomdesc">Pointer dereference<br><tt>int p;</tt></td><td class="idiomc"><tt>x = p;<br>*p = y;</tt></td><td class="idiomlua"><tt>x = <b>p[0]</b><br><b>p[0]</b> = y</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	513 <tr class="even">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	514 <td class="idiomdesc">Pointer indexing<br><tt>int i, *p;</tt></td><td class="idiomc"><tt>x = p[i];<br>p[i+1] = y;</tt></td><td class="idiomlua"><tt>x = p[i]<br>p[i+1] = y</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	515 <tr class="odd">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	516 <td class="idiomdesc">Array indexing<br><tt>int i, a[];</tt></td><td class="idiomc"><tt>x = a[i];<br>a[i+1] = y;</tt></td><td class="idiomlua"><tt>x = a[i]<br>a[i+1] = y</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	517 <tr class="even separate">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	518 <td class="idiomdesc"><tt>struct</tt>/<tt>union</tt> dereference<br><tt>struct foo s;</tt></td><td class="idiomc"><tt>x = s.field;<br>s.field = y;</tt></td><td class="idiomlua"><tt>x = s.field<br>s.field = y</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	519 <tr class="odd">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	520 <td class="idiomdesc"><tt>struct</tt>/<tt>union</tt> pointer deref.<br><tt>struct foo *sp;</tt></td><td class="idiomc"><tt>x = sp->field;<br>sp->field = y;</tt></td><td class="idiomlua"><tt>x = <b>s.field</b><br><b>s.field</b> = y</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	521 <tr class="even separate">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	522 <td class="idiomdesc">Pointer arithmetic<br><tt>int i, *p;</tt></td><td class="idiomc"><tt>x = p + i;<br>y = p - i;</tt></td><td class="idiomlua"><tt>x = p + i<br>y = p - i</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	523 <tr class="odd">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	524 <td class="idiomdesc">Pointer difference<br><tt>int p1, p2;</tt></td><td class="idiomc"><tt>x = p1 - p2;</tt></td><td class="idiomlua"><tt>x = p1 - p2</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	525 <tr class="even">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	526 <td class="idiomdesc">Array element pointer<br><tt>int i, a[];</tt></td><td class="idiomc"><tt>x = &a[i];</tt></td><td class="idiomlua"><tt>x = <b>a+i</b></tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	527 <tr class="odd">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	528 <td class="idiomdesc">Cast pointer to address<br><tt>int *p;</tt></td><td class="idiomc"><tt>x = (intptr_t)p;</tt></td><td class="idiomlua"><tt>x = <b>tonumber(<br> ffi.cast("intptr_t",<br>          p))</b></tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	529 <tr class="even separate">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	530 <td class="idiomdesc">Functions with outargs<br><tt>void foo(int *inoutlen);</tt></td><td class="idiomc"><tt>int len = x;<br>foo(&len);<br>y = len;</tt></td><td class="idiomlua"><tt><b>local len =<br>  ffi.new("int[1]", x)<br>foo(len)<br>y = len[0]</b></tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	531 <tr class="odd">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	532 <td class="idiomdesc"><a href="ext_ffi_semantics.html#convert_vararg">Vararg conversions</a><br><tt>int printf(char *fmt, ...);</tt></td><td class="idiomc"><tt>printf("%g", 1.0);<br>printf("%d", 1);<br> </tt></td><td class="idiomlua"><tt>printf("%g", 1);<br>printf("%d",<br>  <b>ffi.new("int", 1)</b>)</tt></td></tr>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	533 </table>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	534
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	535 <h2 id="cache">To Cache or Not to Cache</h2>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	536 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	537 It's a common Lua idiom to cache library functions in local variables
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	538 or upvalues, e.g.:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	539 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	540 <pre class="code">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	541 local byte, char = string.byte, string.char
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	542 local function foo(x)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	543 return char(byte(x)+1)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	544 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	545 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	546 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	547 This replaces several hash-table lookups with a (faster) direct use of
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	548 a local or an upvalue. This is less important with LuaJIT, since the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	549 JIT compiler optimizes hash-table lookups a lot and is even able to
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	550 hoist most of them out of the inner loops. It can't eliminate
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	551 <em>all</em> of them, though, and it saves some typing for often-used
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	552 functions. So there's still a place for this, even with LuaJIT.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	553 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	554 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	555 The situation is a bit different with C function calls via the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	556 FFI library. The JIT compiler has special logic to eliminate <em>all
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	557 of the lookup overhead</em> for functions resolved from a
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	558 <a href="ext_ffi_semantics.html#clib">C library namespace</a>!
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	559 Thus it's not helpful and actually counter-productive to cache
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	560 individual C functions like this:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	561 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	562 <pre class="code">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	563 local <b>funca</b>, <b>funcb</b> = ffi.C.funca, ffi.C.funcb -- <span style="color:#c00000;">Not helpful!</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	564 local function foo(x, n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	565 for i=1,n do <b>funcb</b>(<b>funca</b>(x, i), 1) end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	566 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	567 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	568 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	569 This turns them into indirect calls and generates bigger and slower
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	570 machine code. Instead, you'll want to cache the namespace itself and
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	571 rely on the JIT compiler to eliminate the lookups:
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	572 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	573 <pre class="code">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	574 local <b>C</b> = ffi.C -- <span style="color:#00a000;">Instead use this!</span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	575 local function foo(x, n)
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	576 for i=1,n do <b>C.funcb</b>(<b>C.funca</b>(x, i), 1) end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	577 end
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	578 </pre>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	579 <p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	580 This generates both shorter and faster code. So <b>don't cache
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	581 C functions</b>, but <b>do</b> cache namespaces! Most often the
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	582 namespace is already in a local variable at an outer scope, e.g. from
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	583 <tt>local lib = ffi.load(...)</tt>. Note that copying
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	584 it to a local variable in the function scope is unnecessary.
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	585 </p>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	586 <br class="flush">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	587 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	588 <div id="foot">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	589 <hr class="hide">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	590 Copyright © 2005-2023
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	591 <span class="noprint">
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	592 ·
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	593 <a href="contact.html">Contact</a>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	594 </span>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	595 </div>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	596 </body>
94705b5986b3 [ThirdParty] Added WRK and luajit for load testing. MrJuneJune <me@mrjunejune.com> parents: diff changeset	597 </html>

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