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diff --git a/deps/LuaJIT/doc/ext_ffi_tutorial.html b/deps/LuaJIT/doc/ext_ffi_tutorial.html deleted file mode 100644 index e0b0821..0000000 --- a/deps/LuaJIT/doc/ext_ffi_tutorial.html +++ /dev/null @@ -1,602 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> -<html> -<head> -<title>FFI Tutorial</title> -<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> -<meta name="Copyright" content="Copyright (C) 2005-2018"> -<meta name="Language" content="en"> -<link rel="stylesheet" type="text/css" href="bluequad.css" media="screen"> -<link rel="stylesheet" type="text/css" href="bluequad-print.css" media="print"> -<style type="text/css"> -table.idiomtable { font-size: 90%; line-height: 1.2; } -table.idiomtable tt { font-size: 100%; } -table.idiomtable td { vertical-align: top; } -tr.idiomhead td { font-weight: bold; } -td.idiomlua b { font-weight: normal; color: #2142bf; } -</style> -</head> -<body> -<div id="site"> -<a href="http://luajit.org"><span>Lua<span id="logo">JIT</span></span></a> -</div> -<div id="head"> -<h1>FFI Tutorial</h1> -</div> -<div id="nav"> -<ul><li> -<a href="luajit.html">LuaJIT</a> -<ul><li> -<a href="http://luajit.org/download.html">Download <span class="ext">»</span></a> -</li><li> -<a href="install.html">Installation</a> -</li><li> -<a href="running.html">Running</a> -</li></ul> -</li><li> -<a href="extensions.html">Extensions</a> -<ul><li> -<a href="ext_ffi.html">FFI Library</a> -<ul><li> -<a class="current" href="ext_ffi_tutorial.html">FFI Tutorial</a> -</li><li> -<a href="ext_ffi_api.html">ffi.* API</a> -</li><li> -<a href="ext_ffi_semantics.html">FFI Semantics</a> -</li></ul> -</li><li> -<a href="ext_jit.html">jit.* Library</a> -</li><li> -<a href="ext_c_api.html">Lua/C API</a> -</li><li> -<a href="ext_profiler.html">Profiler</a> -</li></ul> -</li><li> -<a href="status.html">Status</a> -<ul><li> -<a href="changes.html">Changes</a> -</li></ul> -</li><li> -<a href="faq.html">FAQ</a> -</li><li> -<a href="http://luajit.org/performance.html">Performance <span class="ext">»</span></a> -</li><li> -<a href="http://wiki.luajit.org/">Wiki <span class="ext">»</span></a> -</li><li> -<a href="http://luajit.org/list.html">Mailing List <span class="ext">»</span></a> -</li></ul> -</div> -<div id="main"> -<p> -This page is intended to give you an overview of the features of the FFI -library by presenting a few use cases and guidelines. -</p> -<p> -This page makes no attempt to explain all of the FFI library, though. -You'll want to have a look at the <a href="ext_ffi_api.html">ffi.* API -function reference</a> and the <a href="ext_ffi_semantics.html">FFI -semantics</a> to learn more. -</p> - -<h2 id="load">Loading the FFI Library</h2> -<p> -The FFI library is built into LuaJIT by default, but it's not loaded -and initialized by default. The suggested way to use the FFI library -is to add the following to the start of every Lua file that needs one -of its functions: -</p> -<pre class="code"> -local ffi = require("ffi") -</pre> -<p> -Please note this doesn't define an <tt>ffi</tt> variable in the table -of globals — you really need to use the local variable. The -<tt>require</tt> function ensures the library is only loaded once. -</p> -<p style="font-size: 8pt;"> -Note: If you want to experiment with the FFI from the interactive prompt -of the command line executable, omit the <tt>local</tt>, as it doesn't -preserve local variables across lines. -</p> - -<h2 id="sleep">Accessing Standard System Functions</h2> -<p> -The following code explains how to access standard system functions. -We slowly print two lines of dots by sleeping for 10 milliseconds -after each dot: -</p> -<pre class="code mark"> -<span class="codemark"> -① - - - - - -② -③ -④ - - - -⑤ - - - - - -⑥</span>local ffi = require("ffi") -ffi.cdef[[ -<span style="color:#00a000;">void Sleep(int ms); -int poll(struct pollfd *fds, unsigned long nfds, int timeout);</span> -]] - -local sleep -if ffi.os == "Windows" then - function sleep(s) - ffi.C.Sleep(s*1000) - end -else - function sleep(s) - ffi.C.poll(nil, 0, s*1000) - end -end - -for i=1,160 do - io.write("."); io.flush() - sleep(0.01) -end -io.write("\n") -</pre> -<p> -Here's the step-by-step explanation: -</p> -<p> -<span class="mark">①</span> This defines the -C library functions we're going to use. The part inside the -double-brackets (in green) is just standard C syntax. You can -usually get this info from the C header files or the -documentation provided by each C library or C compiler. -</p> -<p> -<span class="mark">②</span> The difficulty we're -facing here, is that there are different standards to choose from. -Windows has a simple <tt>Sleep()</tt> function. On other systems there -are a variety of functions available to achieve sub-second sleeps, but -with no clear consensus. Thankfully <tt>poll()</tt> can be used for -this task, too, and it's present on most non-Windows systems. The -check for <tt>ffi.os</tt> makes sure we use the Windows-specific -function only on Windows systems. -</p> -<p> -<span class="mark">③</span> Here we're wrapping the -call to the C function in a Lua function. This isn't strictly -necessary, but it's helpful to deal with system-specific issues only -in one part of the code. The way we're wrapping it ensures the check -for the OS is only done during initialization and not for every call. -</p> -<p> -<span class="mark">④</span> A more subtle point is -that we defined our <tt>sleep()</tt> function (for the sake of this -example) as taking the number of seconds, but accepting fractional -seconds. Multiplying this by 1000 gets us milliseconds, but that still -leaves it a Lua number, which is a floating-point value. Alas, the -<tt>Sleep()</tt> function only accepts an integer value. Luckily for -us, the FFI library automatically performs the conversion when calling -the function (truncating the FP value towards zero, like in C). -</p> -<p style="font-size: 8pt;"> -Some readers will notice that <tt>Sleep()</tt> is part of -<tt>KERNEL32.DLL</tt> and is also a <tt>stdcall</tt> function. So how -can this possibly work? The FFI library provides the <tt>ffi.C</tt> -default C library namespace, which allows calling functions from -the default set of libraries, like a C compiler would. Also, the -FFI library automatically detects <tt>stdcall</tt> functions, so you -don't need to declare them as such. -</p> -<p> -<span class="mark">⑤</span> The <tt>poll()</tt> -function takes a couple more arguments we're not going to use. You can -simply use <tt>nil</tt> to pass a <tt>NULL</tt> pointer and <tt>0</tt> -for the <tt>nfds</tt> parameter. Please note that the -number <tt>0</tt> <em>does not convert to a pointer value</em>, -unlike in C++. You really have to pass pointers to pointer arguments -and numbers to number arguments. -</p> -<p style="font-size: 8pt;"> -The page on <a href="ext_ffi_semantics.html">FFI semantics</a> has all -of the gory details about -<a href="ext_ffi_semantics.html#convert">conversions between Lua -objects and C types</a>. For the most part you don't have to deal -with this, as it's performed automatically and it's carefully designed -to bridge the semantic differences between Lua and C. -</p> -<p> -<span class="mark">⑥</span> Now that we have defined -our own <tt>sleep()</tt> function, we can just call it from plain Lua -code. That wasn't so bad, huh? Turning these boring animated dots into -a fascinating best-selling game is left as an exercise for the reader. -:-) -</p> - -<h2 id="zlib">Accessing the zlib Compression Library</h2> -<p> -The following code shows how to access the <a -href="http://zlib.net/">zlib</a> compression library from Lua code. -We'll define two convenience wrapper functions that take a string and -compress or uncompress it to another string: -</p> -<pre class="code mark"> -<span class="codemark"> -① - - - - - - -② - - -③ - -④ - - -⑤ - - -⑥ - - - - - - - -⑦</span>local ffi = require("ffi") -ffi.cdef[[ -<span style="color:#00a000;">unsigned long compressBound(unsigned long sourceLen); -int compress2(uint8_t *dest, unsigned long *destLen, - const uint8_t *source, unsigned long sourceLen, int level); -int uncompress(uint8_t *dest, unsigned long *destLen, - const uint8_t *source, unsigned long sourceLen);</span> -]] -local zlib = ffi.load(ffi.os == "Windows" and "zlib1" or "z") - -local function compress(txt) - local n = zlib.compressBound(#txt) - local buf = ffi.new("uint8_t[?]", n) - local buflen = ffi.new("unsigned long[1]", n) - local res = zlib.compress2(buf, buflen, txt, #txt, 9) - assert(res == 0) - return ffi.string(buf, buflen[0]) -end - -local function uncompress(comp, n) - local buf = ffi.new("uint8_t[?]", n) - local buflen = ffi.new("unsigned long[1]", n) - local res = zlib.uncompress(buf, buflen, comp, #comp) - assert(res == 0) - return ffi.string(buf, buflen[0]) -end - --- Simple test code. -local txt = string.rep("abcd", 1000) -print("Uncompressed size: ", #txt) -local c = compress(txt) -print("Compressed size: ", #c) -local txt2 = uncompress(c, #txt) -assert(txt2 == txt) -</pre> -<p> -Here's the step-by-step explanation: -</p> -<p> -<span class="mark">①</span> This defines some of the -C functions provided by zlib. For the sake of this example, some -type indirections have been reduced and it uses the pre-defined -fixed-size integer types, while still adhering to the zlib API/ABI. -</p> -<p> -<span class="mark">②</span> This loads the zlib shared -library. On POSIX systems it's named <tt>libz.so</tt> and usually -comes pre-installed. Since <tt>ffi.load()</tt> automatically adds any -missing standard prefixes/suffixes, we can simply load the -<tt>"z"</tt> library. On Windows it's named <tt>zlib1.dll</tt> and -you'll have to download it first from the -<a href="http://zlib.net/"><span class="ext">»</span> zlib site</a>. The check for -<tt>ffi.os</tt> makes sure we pass the right name to -<tt>ffi.load()</tt>. -</p> -<p> -<span class="mark">③</span> First, the maximum size of -the compression buffer is obtained by calling the -<tt>zlib.compressBound</tt> function with the length of the -uncompressed string. The next line allocates a byte buffer of this -size. The <tt>[?]</tt> in the type specification indicates a -variable-length array (VLA). The actual number of elements of this -array is given as the 2nd argument to <tt>ffi.new()</tt>. -</p> -<p> -<span class="mark">④</span> This may look strange at -first, but have a look at the declaration of the <tt>compress2</tt> -function from zlib: the destination length is defined as a pointer! -This is because you pass in the maximum buffer size and get back the -actual length that was used. -</p> -<p> -In C you'd pass in the address of a local variable -(<tt>&buflen</tt>). But since there's no address-of operator in -Lua, we'll just pass in a one-element array. Conveniently it can be -initialized with the maximum buffer size in one step. Calling the -actual <tt>zlib.compress2</tt> function is then straightforward. -</p> -<p> -<span class="mark">⑤</span> We want to return the -compressed data as a Lua string, so we'll use <tt>ffi.string()</tt>. -It needs a pointer to the start of the data and the actual length. The -length has been returned in the <tt>buflen</tt> array, so we'll just -get it from there. -</p> -<p style="font-size: 8pt;"> -Note that since the function returns now, the <tt>buf</tt> and -<tt>buflen</tt> variables will eventually be garbage collected. This -is fine, because <tt>ffi.string()</tt> has copied the contents to a -newly created (interned) Lua string. If you plan to call this function -lots of times, consider reusing the buffers and/or handing back the -results in buffers instead of strings. This will reduce the overhead -for garbage collection and string interning. -</p> -<p> -<span class="mark">⑥</span> The <tt>uncompress</tt> -functions does the exact opposite of the <tt>compress</tt> function. -The compressed data doesn't include the size of the original string, -so this needs to be passed in. Otherwise no surprises here. -</p> -<p> -<span class="mark">⑦</span> The code, that makes use -of the functions we just defined, is just plain Lua code. It doesn't -need to know anything about the LuaJIT FFI — the convenience -wrapper functions completely hide it. -</p> -<p> -One major advantage of the LuaJIT FFI is that you are now able to -write those wrappers <em>in Lua</em>. And at a fraction of the time it -would cost you to create an extra C module using the Lua/C API. -Many of the simpler C functions can probably be used directly -from your Lua code, without any wrappers. -</p> -<p style="font-size: 8pt;"> -Side note: the zlib API uses the <tt>long</tt> type for passing -lengths and sizes around. But all those zlib functions actually only -deal with 32 bit values. This is an unfortunate choice for a -public API, but may be explained by zlib's history — we'll just -have to deal with it. -</p> -<p style="font-size: 8pt;"> -First, you should know that a <tt>long</tt> is a 64 bit type e.g. -on POSIX/x64 systems, but a 32 bit type on Windows/x64 and on -32 bit systems. Thus a <tt>long</tt> result can be either a plain -Lua number or a boxed 64 bit integer cdata object, depending on -the target system. -</p> -<p style="font-size: 8pt;"> -Ok, so the <tt>ffi.*</tt> functions generally accept cdata objects -wherever you'd want to use a number. That's why we get a away with -passing <tt>n</tt> to <tt>ffi.string()</tt> above. But other Lua -library functions or modules don't know how to deal with this. So for -maximum portability one needs to use <tt>tonumber()</tt> on returned -<tt>long</tt> results before passing them on. Otherwise the -application might work on some systems, but would fail in a POSIX/x64 -environment. -</p> - -<h2 id="metatype">Defining Metamethods for a C Type</h2> -<p> -The following code explains how to define metamethods for a C type. -We define a simple point type and add some operations to it: -</p> -<pre class="code mark"> -<span class="codemark"> -① - - - -② - -③ - -④ - - - -⑤ - -⑥</span>local ffi = require("ffi") -ffi.cdef[[ -<span style="color:#00a000;">typedef struct { double x, y; } point_t;</span> -]] - -local point -local mt = { - __add = function(a, b) return point(a.x+b.x, a.y+b.y) end, - __len = function(a) return math.sqrt(a.x*a.x + a.y*a.y) end, - __index = { - area = function(a) return a.x*a.x + a.y*a.y end, - }, -} -point = ffi.metatype("point_t", mt) - -local a = point(3, 4) -print(a.x, a.y) --> 3 4 -print(#a) --> 5 -print(a:area()) --> 25 -local b = a + point(0.5, 8) -print(#b) --> 12.5 -</pre> -<p> -Here's the step-by-step explanation: -</p> -<p> -<span class="mark">①</span> This defines the C type for a -two-dimensional point object. -</p> -<p> -<span class="mark">②</span> We have to declare the variable -holding the point constructor first, because it's used inside of a -metamethod. -</p> -<p> -<span class="mark">③</span> Let's define an <tt>__add</tt> -metamethod which adds the coordinates of two points and creates a new -point object. For simplicity, this function assumes that both arguments -are points. But it could be any mix of objects, if at least one operand -is of the required type (e.g. adding a point plus a number or vice -versa). Our <tt>__len</tt> metamethod returns the distance of a point to -the origin. -</p> -<p> -<span class="mark">④</span> If we run out of operators, we can -define named methods, too. Here the <tt>__index</tt> table defines an -<tt>area</tt> function. For custom indexing needs, one might want to -define <tt>__index</tt> and <tt>__newindex</tt> <em>functions</em> instead. -</p> -<p> -<span class="mark">⑤</span> This associates the metamethods with -our C type. This only needs to be done once. For convenience, a -constructor is returned by -<a href="ext_ffi_api.html#ffi_metatype"><tt>ffi.metatype()</tt></a>. -We're not required to use it, though. The original C type can still -be used e.g. to create an array of points. The metamethods automatically -apply to any and all uses of this type. -</p> -<p> -Please note that the association with a metatable is permanent and -<b>the metatable must not be modified afterwards!</b> Ditto for the -<tt>__index</tt> table. -</p> -<p> -<span class="mark">⑥</span> Here are some simple usage examples -for the point type and their expected results. The pre-defined -operations (such as <tt>a.x</tt>) can be freely mixed with the newly -defined metamethods. Note that <tt>area</tt> is a method and must be -called with the Lua syntax for methods: <tt>a:area()</tt>, not -<tt>a.area()</tt>. -</p> -<p> -The C type metamethod mechanism is most useful when used in -conjunction with C libraries that are written in an object-oriented -style. Creators return a pointer to a new instance and methods take an -instance pointer as the first argument. Sometimes you can just point -<tt>__index</tt> to the library namespace and <tt>__gc</tt> to the -destructor and you're done. But often enough you'll want to add -convenience wrappers, e.g. to return actual Lua strings or when -returning multiple values. -</p> -<p> -Some C libraries only declare instance pointers as an opaque -<tt>void *</tt> type. In this case you can use a fake type for all -declarations, e.g. a pointer to a named (incomplete) struct will do: -<tt>typedef struct foo_type *foo_handle</tt>. The C side doesn't -know what you declare with the LuaJIT FFI, but as long as the underlying -types are compatible, everything still works. -</p> - -<h2 id="idioms">Translating C Idioms</h2> -<p> -Here's a list of common C idioms and their translation to the -LuaJIT FFI: -</p> -<table class="idiomtable"> -<tr class="idiomhead"> -<td class="idiomdesc">Idiom</td> -<td class="idiomc">C code</td> -<td class="idiomlua">Lua code</td> -</tr> -<tr class="odd separate"> -<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> -<tr class="even"> -<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> -<tr class="odd"> -<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> -<tr class="even separate"> -<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> -<tr class="odd"> -<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> -<tr class="even separate"> -<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> -<tr class="odd"> -<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> -<tr class="even"> -<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> -<tr class="odd"> -<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> -<tr class="even separate"> -<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> -<tr class="odd"> -<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> -</table> - -<h2 id="cache">To Cache or Not to Cache</h2> -<p> -It's a common Lua idiom to cache library functions in local variables -or upvalues, e.g.: -</p> -<pre class="code"> -local byte, char = string.byte, string.char -local function foo(x) - return char(byte(x)+1) -end -</pre> -<p> -This replaces several hash-table lookups with a (faster) direct use of -a local or an upvalue. This is less important with LuaJIT, since the -JIT compiler optimizes hash-table lookups a lot and is even able to -hoist most of them out of the inner loops. It can't eliminate -<em>all</em> of them, though, and it saves some typing for often-used -functions. So there's still a place for this, even with LuaJIT. -</p> -<p> -The situation is a bit different with C function calls via the -FFI library. The JIT compiler has special logic to eliminate <em>all -of the lookup overhead</em> for functions resolved from a -<a href="ext_ffi_semantics.html#clib">C library namespace</a>! -Thus it's not helpful and actually counter-productive to cache -individual C functions like this: -</p> -<pre class="code"> -local <b>funca</b>, <b>funcb</b> = ffi.C.funca, ffi.C.funcb -- <span style="color:#c00000;">Not helpful!</span> -local function foo(x, n) - for i=1,n do <b>funcb</b>(<b>funca</b>(x, i), 1) end -end -</pre> -<p> -This turns them into indirect calls and generates bigger and slower -machine code. Instead you'll want to cache the namespace itself and -rely on the JIT compiler to eliminate the lookups: -</p> -<pre class="code"> -local <b>C</b> = ffi.C -- <span style="color:#00a000;">Instead use this!</span> -local function foo(x, n) - for i=1,n do <b>C.funcb</b>(<b>C.funca</b>(x, i), 1) end -end -</pre> -<p> -This generates both shorter and faster code. So <b>don't cache -C functions</b>, but <b>do</b> cache namespaces! Most often the -namespace is already in a local variable at an outer scope, e.g. from -<tt>local lib = ffi.load(...)</tt>. Note that copying -it to a local variable in the function scope is unnecessary. -</p> -<br class="flush"> -</div> -<div id="foot"> -<hr class="hide"> -Copyright © 2005-2018 -<span class="noprint"> -· -<a href="contact.html">Contact</a> -</span> -</div> -</body> -</html> |