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

annotate third_party/luajit/doc/ext_ffi_tutorial.html @ 279:b3b547563ec7

Add Google connector service and agent wiki Implement the C/Seobeo Google Drive and Gmail connector with encrypted OAuth storage, Zenbu authentication, browser testing, AI tool discovery, chunked HTTP decoding, and Bazel coverage. Consolidate repository guidance into progressive wiki documentation and enforce arena-first allocation for new first-party C code. Co-authored-by: Copilot <[email protected]> Copilot-Session: 84c338fd-0939-4bb3-b7f3-1062eb213e5d

author	MrJuneJune <me@mrjunejune.com>
date	Mon, 17 Aug 2026 22:22:36 -0700
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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