The Need for Code Generation
Have you ever wanted to generate code like the wizards do, i.e. start with a
template, mix in some symbols and boom, out comes the code? If you’re building
a custom AppWizard, you define code like so:
int WINAPI WinMain(HINSTANCE hinst, HINSTANCE, LPSTR, int nShow) {
$$IF(coinit)
// Initialize COM
CoInitialize(0);
$$ENDIF
// Initialize the ATL module
_Module.Init(0, hinst);
$$IF(axhost)
// Initialize support for control containment
AtlAxWinInit();
$$ENDIF
// Create and show the main window
HMENU hMenu = LoadMenu(_Module.GetResourceInstance(),
MAKEINTRESOURCE(IDR_$$ROOT$$));
...
This is fine if you’ve got the MFC-based interpreter building your code and
you’re willing to live within the boundaries of a very small set of features.
The ATL Object Wizard-style of generation is similar, i.e.
class [!ClassName] :
public CAxDialogImpl<[!ClassName]>
{
public:
[!ClassName]()
{
}
[!crlf]
...
Again, only good if you’re running under the ObjectWizard and again, somewhat
limited. What you really want is to be able to do things ASP-style, e.g.
<%@ language=vbscript %>
<% ' test.cpp.asp %>
<%
greeting = Request.QueryString("greeting")
if len(greeting) = 0 then greeting = "Hello, World."
%>
// test.cpp
<% if Request.QueryString("iostream") <> "" then %>
#include <iostream>
using namespace std;
<% else %>
#include <stdio.h>
<% end if %>
int main()
{
<% if Request.QueryString("iostream") <> "" then %>
cout << "<%= greeting %>" << endl;
<% else %>
printf("<%= greeting %>\n");
<% end if %>
return 0;
}
In this case, you get the same effect as the other two, but you’ve got the full
power of a scripting language. However, for this to work, you had to run under
ASP… until now…
TextBox
TextBox is a ASP-like script host that will process any file you give it
looking for:
-
text blocks
-
script blocks (<% script %>)
-
output blocks (<%= output %>)
-
An optional language block as the first line in the file only (<%@
language= language %>)
(TextBox defaults to vbscript and currently only works with vbscript and
jscript).
TextBox pre-processes the text to turn the whole thing into into script and
hands it to the scripting engine for execution, outputting the result to
standard out. Whatever features of the scripting language you want to use, feel
free.
Usage
To provide for I/O, TextBox emulates ASP somewhat. It provides two intrinsics,
the request object and the response object. The Request object has a single
property, QueryString, that works just like ASP. The Response object has a
single property, Write, just like ASP. In fact, if you only use
Request.QueryString and Response.Write, you should be able to test your script
files using ASP.
To set name/value pairs for use by the script via the Request object, the usage
of TextBox is like so:
usage: textbox <file> [name=value]
For example, to interpret the file above, any of the following command lines
would work:
textbox test.cpp.asp
textbox test.cpp.asp greeting="Double Wahoo!"
textbox test.cpp.asp iostream=true greeting="Double Wahoo!"
The first would yield the following output:
// test.cpp
#include <stdio.h>
int main()
{
printf("Hello, World.\n");
return 0;
}
while the last would yield the following:
// test.cpp
#include <iostream>
using namespace std;
int main()
{
cout << "Double Wahoo!" << endl;
return 0;
}
Errors and Debugging
If the scripting engine finds an error, it will notify TextBox, who will notify
you. However, if you’ve got script debugging enabled on your machine, the
scripting engine will ask you if you’d like to fire up the debugger, showing
you exactly the offending code.
Not Just Code
Of course, TextBox is good for the generation of any text, not just code.
Download
TextBox is available for download. It’s just a
prototype, so please adjust your expectations accordingly. If you have any
comments, please send them to
csells@sellsbrothers.com.
Copyright
Copyright (c) 1998-2001, Chris Sells All rights reserved. NO WARRANTIES
EXTENDED. Use at your own risk.
