1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
|
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Extensions</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="Author" content="Mike Pall">
<meta name="Copyright" content="Copyright (C) 2005-2017, Mike Pall">
<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.exc {
line-height: 1.2;
}
tr.exchead td {
font-weight: bold;
}
td.excplatform {
width: 48%;
}
td.exccompiler {
width: 29%;
}
td.excinterop {
width: 23%;
}
</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>Extensions</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 class="current" href="extensions.html">Extensions</a>
<ul><li>
<a href="ext_ffi.html">FFI Library</a>
<ul><li>
<a 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>
LuaJIT is fully upwards-compatible with Lua 5.1. It supports all
<a href="http://www.lua.org/manual/5.1/manual.html#5"><span class="ext">»</span> standard Lua
library functions</a> and the full set of
<a href="http://www.lua.org/manual/5.1/manual.html#3"><span class="ext">»</span> Lua/C API
functions</a>.
</p>
<p>
LuaJIT is also fully ABI-compatible to Lua 5.1 at the linker/dynamic
loader level. This means you can compile a C module against the
standard Lua headers and load the same shared library from either Lua
or LuaJIT.
</p>
<p>
LuaJIT extends the standard Lua VM with new functionality and adds
several extension modules. Please note this page is only about
<em>functional</em> enhancements and not about performance enhancements,
such as the optimized VM, the faster interpreter or the JIT compiler.
</p>
<h2 id="modules">Extensions Modules</h2>
<p>
LuaJIT comes with several built-in extension modules:
</p>
<h3 id="bit"><tt>bit.*</tt> — Bitwise operations</h3>
<p>
LuaJIT supports all bitwise operations as defined by
<a href="http://bitop.luajit.org"><span class="ext">»</span> Lua BitOp</a>:
</p>
<pre class="code">
bit.tobit bit.tohex bit.bnot bit.band bit.bor bit.bxor
bit.lshift bit.rshift bit.arshift bit.rol bit.ror bit.bswap
</pre>
<p>
This module is a LuaJIT built-in — you don't need to download or
install Lua BitOp. The Lua BitOp site has full documentation for all
<a href="http://bitop.luajit.org/api.html"><span class="ext">»</span> Lua BitOp API functions</a>.
The FFI adds support for
<a href="ext_ffi_semantics.html#cdata_arith">64 bit bitwise operations</a>,
using the same API functions.
</p>
<p>
Please make sure to <tt>require</tt> the module before using any of
its functions:
</p>
<pre class="code">
local bit = require("bit")
</pre>
<p>
An already installed Lua BitOp module is ignored by LuaJIT.
This way you can use bit operations from both Lua and LuaJIT on a
shared installation.
</p>
<h3 id="ffi"><tt>ffi.*</tt> — FFI library</h3>
<p>
The <a href="ext_ffi.html">FFI library</a> allows calling external
C functions and the use of C data structures from pure Lua
code.
</p>
<h3 id="jit"><tt>jit.*</tt> — JIT compiler control</h3>
<p>
The functions in this module
<a href="ext_jit.html">control the behavior of the JIT compiler engine</a>.
</p>
<h3 id="c_api">C API extensions</h3>
<p>
LuaJIT adds some
<a href="ext_c_api.html">extra functions to the Lua/C API</a>.
</p>
<h3 id="profiler">Profiler</h3>
<p>
LuaJIT has an <a href="ext_profiler.html">integrated profiler</a>.
</p>
<h2 id="library">Enhanced Standard Library Functions</h2>
<h3 id="xpcall"><tt>xpcall(f, err [,args...])</tt> passes arguments</h3>
<p>
Unlike the standard implementation in Lua 5.1, <tt>xpcall()</tt>
passes any arguments after the error function to the function
which is called in a protected context.
</p>
<h3 id="load"><tt>loadfile()</tt> etc. handle UTF-8 source code</h3>
<p>
Non-ASCII characters are handled transparently by the Lua source code parser.
This allows the use of UTF-8 characters in identifiers and strings.
A UTF-8 BOM is skipped at the start of the source code.
</p>
<h3 id="tostring"><tt>tostring()</tt> etc. canonicalize NaN and ±Inf</h3>
<p>
All number-to-string conversions consistently convert non-finite numbers
to the same strings on all platforms. NaN results in <tt>"nan"</tt>,
positive infinity results in <tt>"inf"</tt> and negative infinity results
in <tt>"-inf"</tt>.
</p>
<h3 id="tonumber"><tt>tonumber()</tt> etc. use builtin string to number conversion</h3>
<p>
All string-to-number conversions consistently convert integer and
floating-point inputs in decimal, hexadecimal and binary on all platforms.
<tt>strtod()</tt> is <em>not</em> used anymore, which avoids numerous
problems with poor C library implementations. The builtin conversion
function provides full precision according to the IEEE-754 standard, it
works independently of the current locale and it supports hex floating-point
numbers (e.g. <tt>0x1.5p-3</tt>).
</p>
<h3 id="string_dump"><tt>string.dump(f [,strip])</tt> generates portable bytecode</h3>
<p>
An extra argument has been added to <tt>string.dump()</tt>. If set to
<tt>true</tt>, 'stripped' bytecode without debug information is
generated. This speeds up later bytecode loading and reduces memory
usage. See also the
<a href="running.html#opt_b"><tt>-b</tt> command line option</a>.
</p>
<p>
The generated bytecode is portable and can be loaded on any architecture
that LuaJIT supports, independent of word size or endianess. However the
bytecode compatibility versions must match. Bytecode stays compatible
for dot releases (x.y.0 → x.y.1), but may change with major or
minor releases (2.0 → 2.1) or between any beta release. Foreign
bytecode (e.g. from Lua 5.1) is incompatible and cannot be loaded.
</p>
<p>
Note: <tt>LJ_GC64</tt> mode requires a different frame layout, which implies
a different, incompatible bytecode format for ports that use this mode (e.g.
ARM64 or MIPS64) or when explicitly enabled for x64. This may be rectified
in the future.
</p>
<h3 id="table_new"><tt>table.new(narray, nhash)</tt> allocates a pre-sized table</h3>
<p>
An extra library function <tt>table.new()</tt> can be made available via
<tt>require("table.new")</tt>. This creates a pre-sized table, just like
the C API equivalent <tt>lua_createtable()</tt>. This is useful for big
tables if the final table size is known and automatic table resizing is
too expensive.
</p>
<h3 id="table_clear"><tt>table.clear(tab)</tt> clears a table</h3>
<p>
An extra library function <tt>table.clear()</tt> can be made available
via <tt>require("table.clear")</tt>. This clears all keys and values
from a table, but preserves the allocated array/hash sizes. This is
useful when a table, which is linked from multiple places, needs to be
cleared and/or when recycling a table for use by the same context. This
avoids managing backlinks, saves an allocation and the overhead of
incremental array/hash part growth.
</p>
<p>
Please note this function is meant for very specific situations. In most
cases it's better to replace the (usually single) link with a new table
and let the GC do its work.
</p>
<h3 id="math_random">Enhanced PRNG for <tt>math.random()</tt></h3>
<p>
LuaJIT uses a Tausworthe PRNG with period 2^223 to implement
<tt>math.random()</tt> and <tt>math.randomseed()</tt>. The quality of
the PRNG results is much superior compared to the standard Lua
implementation which uses the platform-specific ANSI rand().
</p>
<p>
The PRNG generates the same sequences from the same seeds on all
platforms and makes use of all bits in the seed argument.
<tt>math.random()</tt> without arguments generates 52 pseudo-random bits
for every call. The result is uniformly distributed between 0.0 and 1.0.
It's correctly scaled up and rounded for <tt>math.random(n [,m])</tt> to
preserve uniformity.
</p>
<h3 id="io"><tt>io.*</tt> functions handle 64 bit file offsets</h3>
<p>
The file I/O functions in the standard <tt>io.*</tt> library handle
64 bit file offsets. In particular this means it's possible
to open files larger than 2 Gigabytes and to reposition or obtain
the current file position for offsets beyond 2 GB
(<tt>fp:seek()</tt> method).
</p>
<h3 id="debug_meta"><tt>debug.*</tt> functions identify metamethods</h3>
<p>
<tt>debug.getinfo()</tt> and <tt>lua_getinfo()</tt> also return information
about invoked metamethods. The <tt>namewhat</tt> field is set to
<tt>"metamethod"</tt> and the <tt>name</tt> field has the name of
the corresponding metamethod (e.g. <tt>"__index"</tt>).
</p>
<h2 id="resumable">Fully Resumable VM</h2>
<p>
The LuaJIT VM is fully resumable. This means you can yield from a
coroutine even across contexts, where this would not possible with
the standard Lua 5.1 VM: e.g. you can yield across <tt>pcall()</tt>
and <tt>xpcall()</tt>, across iterators and across metamethods.
</p>
<h2 id="lua52">Extensions from Lua 5.2</h2>
<p>
LuaJIT supports some language and library extensions from Lua 5.2.
Features that are unlikely to break existing code are unconditionally
enabled:
</p>
<ul>
<li><tt>goto</tt> and <tt>::labels::</tt>.</li>
<li>Hex escapes <tt>'\x3F'</tt> and <tt>'\*'</tt> escape in strings.</li>
<li><tt>load(string|reader [, chunkname [,mode [,env]]])</tt>.</li>
<li><tt>loadstring()</tt> is an alias for <tt>load()</tt>.</li>
<li><tt>loadfile(filename [,mode [,env]])</tt>.</li>
<li><tt>math.log(x [,base])</tt>.</li>
<li><tt>string.rep(s, n [,sep])</tt>.</li>
<li><tt>string.format()</tt>: <tt>%q</tt> reversible.
<tt>%s</tt> checks <tt>__tostring</tt>.
<tt>%a</tt> and <tt>"%A</tt> added.</li>
<li>String matching pattern <tt>%g</tt> added.</li>
<li><tt>io.read("*L")</tt>.</li>
<li><tt>io.lines()</tt> and <tt>file:lines()</tt> process
<tt>io.read()</tt> options.</li>
<li><tt>os.exit(status|true|false [,close])</tt>.</li>
<li><tt>package.searchpath(name, path [, sep [, rep]])</tt>.</li>
<li><tt>package.loadlib(name, "*")</tt>.</li>
<li><tt>debug.getinfo()</tt> returns <tt>nparams</tt> and <tt>isvararg</tt>
for option <tt>"u"</tt>.</li>
<li><tt>debug.getlocal()</tt> accepts function instead of level.</li>
<li><tt>debug.getlocal()</tt> and <tt>debug.setlocal()</tt> accept negative
indexes for varargs.</li>
<li><tt>debug.getupvalue()</tt> and <tt>debug.setupvalue()</tt> handle
C functions.</li>
<li><tt>debug.upvalueid()</tt> and <tt>debug.upvaluejoin()</tt>.</li>
<li>Lua/C API extensions:
<tt>lua_version()</tt>
<tt>lua_upvalueid()</tt>
<tt>lua_upvaluejoin()</tt>
<tt>lua_loadx()</tt>
<tt>lua_copy()</tt>
<tt>lua_tonumberx()</tt>
<tt>lua_tointegerx()</tt>
<tt>luaL_fileresult()</tt>
<tt>luaL_execresult()</tt>
<tt>luaL_loadfilex()</tt>
<tt>luaL_loadbufferx()</tt>
<tt>luaL_traceback()</tt>
<tt>luaL_setfuncs()</tt>
<tt>luaL_pushmodule()</tt>
<tt>luaL_newlibtable()</tt>
<tt>luaL_newlib()</tt>
<tt>luaL_testudata()</tt>
<tt>luaL_setmetatable()</tt>
</li>
<li>Command line option <tt>-E</tt>.</li>
<li>Command line checks <tt>__tostring</tt> for errors.</li>
</ul>
<p>
Other features are only enabled, if LuaJIT is built with
<tt>-DLUAJIT_ENABLE_LUA52COMPAT</tt>:
</p>
<ul>
<li><tt>goto</tt> is a keyword and not a valid variable name anymore.</li>
<li><tt>break</tt> can be placed anywhere. Empty statements (<tt>;;</tt>)
are allowed.</li>
<li><tt>__lt</tt>, <tt>__le</tt> are invoked for mixed types.</li>
<li><tt>__len</tt> for tables. <tt>rawlen()</tt> library function.</li>
<li><tt>pairs()</tt> and <tt>ipairs()</tt> check for <tt>__pairs</tt> and
<tt>__ipairs</tt>.</li>
<li><tt>coroutine.running()</tt> returns two results.</li>
<li><tt>table.pack()</tt> and <tt>table.unpack()</tt>
(same as <tt>unpack()</tt>).</li>
<li><tt>io.write()</tt> and <tt>file:write()</tt> return file handle
instead of <tt>true</tt>.</li>
<li><tt>os.execute()</tt> and <tt>pipe:close()</tt> return detailed
exit status.</li>
<li><tt>debug.setmetatable()</tt> returns object.</li>
<li><tt>debug.getuservalue()</tt> and <tt>debug.setuservalue()</tt>.</li>
<li>Remove <tt>math.mod()</tt>, <tt>string.gfind()</tt>.</li>
<li><tt>package.searchers</tt>.</li>
<li><tt>module()</tt> returns the module table.</li>
</ul>
<p>
Note: this provides only partial compatibility with Lua 5.2 at the
language and Lua library level. LuaJIT is API+ABI-compatible with
Lua 5.1, which prevents implementing features that would otherwise
break the Lua/C API and ABI (e.g. <tt>_ENV</tt>).
</p>
<h2 id="lua53">Extensions from Lua 5.3</h2>
<p>
LuaJIT supports some extensions from Lua 5.3:
<ul>
<li>Unicode escape <tt>'\u{XX...}'</tt> embeds the UTF-8 encoding in string literals.</li>
<li>The argument table <tt>arg</tt> can be read (and modified) by <tt>LUA_INIT</tt> and <tt>-e</tt> chunks.</li>
<li><tt>io.read()</tt> and <tt>file:read()</tt> accept formats with or without a leading <tt>*</tt>.</li>
<li><tt>table.move(a1, f, e, t [,a2])</tt>.</li>
<li><tt>coroutine.isyieldable()</tt>.</li>
<li>Lua/C API extensions:
<tt>lua_isyieldable()</tt>
</li>
</ul>
<h2 id="exceptions">C++ Exception Interoperability</h2>
<p>
LuaJIT has built-in support for interoperating with C++ exceptions.
The available range of features depends on the target platform and
the toolchain used to compile LuaJIT:
</p>
<table class="exc">
<tr class="exchead">
<td class="excplatform">Platform</td>
<td class="exccompiler">Compiler</td>
<td class="excinterop">Interoperability</td>
</tr>
<tr class="odd separate">
<td class="excplatform">POSIX/x64, DWARF2 unwinding</td>
<td class="exccompiler">GCC 4.3+, Clang</td>
<td class="excinterop"><b style="color: #00a000;">Full</b></td>
</tr>
<tr class="even">
<td class="excplatform">ARM <tt>-DLUAJIT_UNWIND_EXTERNAL</tt></td>
<td class="exccompiler">GCC, Clang</td>
<td class="excinterop"><b style="color: #00a000;">Full</b></td>
</tr>
<tr class="odd">
<td class="excplatform">Other platforms, DWARF2 unwinding</td>
<td class="exccompiler">GCC, Clang</td>
<td class="excinterop"><b style="color: #c06000;">Limited</b></td>
</tr>
<tr class="even">
<td class="excplatform">Windows/x64</td>
<td class="exccompiler">MSVC or WinSDK</td>
<td class="excinterop"><b style="color: #00a000;">Full</b></td>
</tr>
<tr class="odd">
<td class="excplatform">Windows/x86</td>
<td class="exccompiler">Any</td>
<td class="excinterop"><b style="color: #00a000;">Full</b></td>
</tr>
<tr class="even">
<td class="excplatform">Other platforms</td>
<td class="exccompiler">Other compilers</td>
<td class="excinterop"><b style="color: #a00000;">No</b></td>
</tr>
</table>
<p>
<b style="color: #00a000;">Full interoperability</b> means:
</p>
<ul>
<li>C++ exceptions can be caught on the Lua side with <tt>pcall()</tt>,
<tt>lua_pcall()</tt> etc.</li>
<li>C++ exceptions will be converted to the generic Lua error
<tt>"C++ exception"</tt>, unless you use the
<a href="ext_c_api.html#mode_wrapcfunc">C call wrapper</a> feature.</li>
<li>It's safe to throw C++ exceptions across non-protected Lua frames
on the C stack. The contents of the C++ exception object
pass through unmodified.</li>
<li>Lua errors can be caught on the C++ side with <tt>catch(...)</tt>.
The corresponding Lua error message can be retrieved from the Lua stack.</li>
<li>Throwing Lua errors across C++ frames is safe. C++ destructors
will be called.</li>
</ul>
<p>
<b style="color: #c06000;">Limited interoperability</b> means:
</p>
<ul>
<li>C++ exceptions can be caught on the Lua side with <tt>pcall()</tt>,
<tt>lua_pcall()</tt> etc.</li>
<li>C++ exceptions will be converted to the generic Lua error
<tt>"C++ exception"</tt>, unless you use the
<a href="ext_c_api.html#mode_wrapcfunc">C call wrapper</a> feature.</li>
<li>C++ exceptions will be caught by non-protected Lua frames and
are rethrown as a generic Lua error. The C++ exception object will
be destroyed.</li>
<li>Lua errors <b>cannot</b> be caught on the C++ side.</li>
<li>Throwing Lua errors across C++ frames will <b>not</b> call
C++ destructors.</li>
</ul>
<p>
<b style="color: #a00000;">No interoperability</b> means:
</p>
<ul>
<li>It's <b>not</b> safe to throw C++ exceptions across Lua frames.</li>
<li>C++ exceptions <b>cannot</b> be caught on the Lua side.</li>
<li>Lua errors <b>cannot</b> be caught on the C++ side.</li>
<li>Throwing Lua errors across C++ frames will <b>not</b> call
C++ destructors.</li>
</ul>
<br class="flush">
</div>
<div id="foot">
<hr class="hide">
Copyright © 2005-2017 Mike Pall
<span class="noprint">
·
<a href="contact.html">Contact</a>
</span>
</div>
</body>
</html>
|
