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70行lua代码实现一个满足基本要求的模版引擎

2013-12-22 01:25 337 查看

以下内容仅供学习交流，未经严格考虑与测试，切勿用于生产环境。

ltemplate.lua

local insert = table.insert
local remove = table.remove
local concat = table.concat
local format = string.format

local loaded = {}
local partten = "(.-){#([^#].-[^#])#}()"

local content = {}
local cur_content = nil

local function ob_start()
cur_content = {}
insert(content, cur_content)
end

local function ob_get_clean()
local ret = concat(cur_content)
remove(content)
cur_content = content[#content]
return ret
end

local function echo(value)
insert(cur_content, value)
end

local function include(path, params)
local bitcode = loaded[path]

if not bitcode then
local fp = io.open(path, "rb")
local template = fp:read('*a')
fp:close()
local results = {}
local last_endpos = 0
for outside, inside, endpos in template:gmatch(partten) do
insert(results, format("echo(%q)", outside))
insert(results, inside)
last_endpos = endpos
end
insert(results, format("echo(%q)", template:sub(last_endpos)))
results = concat(results, "\n")
bitcode = assert(loadstring(results))
loaded[path] = bitcode
end

local env = {
include = include,
echo = echo,
ob_start = ob_start,
ob_get_clean = ob_get_clean
}
setmetatable(env, {__index = function(tb, k)
return params[k] or _G[k]
end})
setfenv(bitcode, env)
bitcode()
end

for i = 1, 100000 do
ob_start()
include(arg[1], {
params = {
a = '1234',
b = '4321'
}
})
ob_get_clean()
end

master.html

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang='zh-CN' xml:lang='zh-CN' xmlns='http://www.w3.org/1999/xhtml'>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
<meta http-equiv="Content-Language" content="zh-CN"/>
<meta name="robots" content="index, follow" />
<link rel="shortcut icon" type="image/x-icon" href="/img/favicon.ico" />
<title> child's personal page - 开源中国社区</title>
<link rel="stylesheet/less" href="http://my.oschina.net/lostchild/styles.less?ver=20131219&date=20131110185237" type="text/css" media="screen" />
<link rel="stylesheet" href="/js/2012/poshytip/tip-yellowsimple/tip-yellowsimple.css" type="text/css" />
<link rel="stylesheet" type="text/css" href="/js/2011/fancybox/jquery.fancybox-1.3.4.css" media="screen" />
<script type="text/javascript" src="/js/2012/jquery-1.7.1.min.js"></script>
<script type="text/javascript" src="/js/2012/jquery.form.js"></script>
<script type="text/javascript" src="/js/2011/fancybox/jquery.fancybox-1.3.4.pack.js"></script>
<script type="text/javascript" src="/js/2012/poshytip/jquery.poshytip.min.js"></script>
<script type="text/javascript" src="/js/2011/oschina.js?ver=20121007"></script>
<script type="text/javascript" src="/js/2012/less-1.3.0.min.js"></script>
<script type="text/javascript" src="/js/scrolltopcontrol.js"></script>
<script type='text/javascript' src='/js/jquery/jquery.atwho.js?ver=2013112501'></script>
<link rel="stylesheet" type="text/css" href="/js/jquery/jquery.atwho.css" />
<link rel="alternate" type="application/rss+xml" title="lostchild最新博客" href="http://my.oschina.net/lostchild/rss" />
<link rel="EditURI" type="application/rsd+xml" title="RSD" href="http://my.oschina.net/action/xmlrpc/rsd?space=1397642" />
<link rel="wlwmanifest" type="application/wlwmanifest+xml" href="http://my.oschina.net/action/xmlrpc/wlwmanifest?space=1397642" />
{# echo(header) #}
</head>
<body>
{# echo(content) #}
<body>
</html>

temp.html，继承master.html

{# ob_start() #}
<script>
alert("hello World")
</script>
{# local header = ob_get_clean() #}

{# ob_start() #}
<table>
{# for k, v in pairs(params) do #}
<tr>
<td>{# echo(k) #}</td>
<td>{# echo(v) #}</td>
</tr>
{# end #}
</table>
{# local content = ob_get_clean() #}

{# include('master.html', {header = header, content = content}) #}

循环十万次测试渲染速度（阿里云最便宜一款vps）

[root@AY130801221248587d02Z ~]# time lua ltemplate.lua temp.html

real    0m1.867s
user    0m1.862s
sys     0m0.004s

总结

由此可见渲染的速度还是非常快的，可以将此原型用于嵌入式设备中的页面上（用大量js实现的嵌入式设备页面兼容性不好）。而且嵌入式设备的界面需要简单明确，所以也不用太丰富的模版功能。

原理很简单：

1.用lua版的正则把模版内{#与#}之间的内容挖出来，原样输出成lua代码，其它部分则生成使用echo打印到某个缓冲区的lua代码。

2.将这个生成出来的代码使用loadstring编译。

3.通过setfenv实现loadstring后的模拟环境配置（用以提供模版内使用的echo，ob_start等函数，以及传入的参数）

4.执行这个编译后的函数即可。

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