Posts in category ‘Templates’.
Thoughts about template system
After looking how ASP.Net and J2EE work I thought a lot about current template system.
Today, CppCMS template system is dynamic typed. For example in order to render template:
<% template mycontent %>
<p>You have <% number %> of <% something %></p>
<% end %>
I write something like that (not correct code but idea):
map<boost::any> content;
content["something"]=string("orange");
content["number"]=10;
template.render(content,output);
The template is compiled to bytecode and than interpreted in rendering engine.
If variable title required it checks its type and renders its content.
Another possible approach it to make is statically typed :
So, I create a view interface for template:
struct mycontent: public content {
string something;
int number;
};
And then the above template is compiled to following C++ code:
void mycontent::render()
{
cout<<"<p>You have "<<number<<" of "<<escape(something)<<"</p>\n";
}
That is compiled to shared object that I can load dynamically. And render template as following:
auto_ptr<my_content> content(template.get("my_content"));
content->number=10;
content->something="orange";
content->render(output);
Thread Safe Implementation of GNU gettext
There is widely available software internationalization tool called GNU gettext. Is is used as base for almost all FOSS software tools. It has binding to almost every language and supports many platforms including Win32.
How does it works? In any place you need to display a string that may potentially show in other language then English you just write:
printf(gettext("Hello World\n"));
And you get the required translation for this string (if available).
In 99% of cases this is good enough. However, as you can see, there is no parameter "target language". It is defined for entry application.
What happends if you need to display this string in different languages? You need to switch locale, and this operation is not thread safe. In most of cases you do not need to do this, because almost all applications will "talk" in single language that user had asked. However this is not the case of web based applications.
Certain web application allow you to display content in several languages: think of government site that should display information in three languages: Hebrew, Arabic and English. So you may need to define the translation per each session you open or use.
So, if you write a multithreaded FastCGI application that supports different languages is signle instance you can’t use gettext.
more...The Roadmap to The First Beta Version of CppCMS
After quite a long period of development I had decided to get prepared to first public beta release of CppCMS.
The major components of this blog and the framework I want to introduce in first beta are following:
- Implementation of Django style templates inheritance, filters (done 70%)
- Introduce powerful cache system (done 100%)
- Replace SOCI by LibDBI (done 100%)
- Improve blog: true markdown, LaTeX equations, categories etc. (done 100%)
- Write Documentation (done 20%)
- Migrate my Hebrew blog from Word Press to CppCMS (done 100%)
There are lots of work to do, but CppCMS now looks much mature then before.
more...New Templates System
New templates system was introduces to the CppCMS framework. It is based on ideas of dynamic typed languages inside static typed C++.
The original template system had several problems:
- The each template variable was referenced by and integer key that was generated during compilation of templates.
- The rendering process required from the developer some kind of activity – update content values according to requests from rendering engine.
- The values of the entries where limited to string, integer and boolean values.
In any case, the design of the first template system was just unacceptable, thus new template system was build.
It introduced following features:
- Dynamic typed variable values using boost::any. They allow assigning of any kind of objects to the variables and rendering them to the templates using custom engines.
- All the variables are references by their names.
- Content now has hierarchical structure when each variable can include list of items or callbacks that allow one step template rendering.
- The design of the engine is now much more modular.
Additional features I'm still working on them are:
- Support of different filters like "html escaping", "urlizing" etc.
- Support of custom filters, including filter chains.
- Support of localization and translation.
Next Step - Caching
As we had seen in previous article, the benchmarks had shown an ability of CppCMS to produce about 630 compressed pages per second and an output of about 20Mbit/s. Is this enough?
For most of cases it is… But as we had seen I want to use every cycle of the CPU as smart as I can. Even, if the model I had suggested, was able to show "a prove of concept" there is an important point that was missed: "Why should I create same page so many times?"
Caching
This is the next logical step in the development of high performance web development framework.
First of all we should understand a requirements of the caching system:
- Efficiency
- Support of "dropping cache on update"
- Support of drop the cache by timeout
- Work using three models: single process cache, shared cache between processes, shared over the network.
- Support of caching on entry page level and single view level as well
- Transparent storage of compressed content
Lets describe each one of them:
more...