HTML Document Templates

HTML Document Templates


	html++ makes it convenient to substitute html++ objects within regular HTML template files. The following example creates a LoadTemplate() routine that loads an HTML file as a template. As it's loaded, the routine locates any dollar-sign prefixed names and matches them with a list of objects for substitution.


	#include <stdio.h>
	#include <stdlib.h>
	#include <dcmicro/htmlpp/htmlpp.h>


	// Load the specified document template into memory, substituting "$"
	// macros with their form/calculated values.
	void LoadTemplate( const String& document,
	htmlContainer& page,
	htmlServer& server,
	CLinkedList& object_list )
	{
	FILE * file ;
	char buffer[ 8096 ] ;
	String filename ;
	String raw ;
	String converted ;
	String token ;
	String field ;
	String value ;
	int pos ;
	Boolean perform_substitution ;
	Boolean object_substitution ;

	// temporarily convert document name to uppercase for easy comparison
	raw = document ;
	raw.ToUpper() ;

	filename = document ;
	file = fopen( (char *) filename, "rt" ) ;
	if ( file != (FILE *) NULL )
	{
	// loop for all lines in the file
	while ( fgets( buffer, sizeof(buffer), file ) != NULL )
	{
	raw = buffer ;
	converted = "" ;

	while ( ( pos = raw.HasSubstring( "$" ) ) != String::NO_SUBSTRING )
	{
	String temp = raw.Left( pos ) ;
	converted += temp ;
	raw -= temp ;

	// look for end of token; first non-alpha or
	// non-digit character, or end of string
	for ( pos = 1 ; pos < raw.GetLength() ; pos++ )
	{
	if ( !( isalpha(raw[pos])
	\|\| isdigit(raw[pos])
	\|\| raw[pos]=='_') )
	{
	// found next character past end of token
	break ;
	}
	}

	token = raw.Left( pos ) ;
	raw -= token ;

	perform_substitution = FALSE ;
	object_substitution = FALSE ;
	token -= "$" ; // strip off leading $ character

	String temp_token = token ;
	temp_token.ToUpper() ;

	// First, check to see if the field appears as a CGI
	// name/value pair. If so, use it's value for the
	// substitution.
	Boolean good_data = server.Enumerate( field, value, TRUE ) ;
	while ( good_data )
	{
	field.ToUpper() ;
	if ( field == temp_token )
	{
	perform_substitution = TRUE ;
	break ;
	}
	good_data = server.Enumerate( field, value ) ;
	}

	// The field is not a CGI name/value pair, so
	// search the object_list
	if ( ! perform_substitution )
	{
	CListItem FAR * item ;
	PObjectDef object ;

	item = object_list.First() ;
	while ( item )
	{
	object = (PObjectDef) item->Item_Data ;
	object->name.ToUpper() ;

	// Bingo -- insert the appropriate object
	if ( object->name == temp_token )
	{
	object_substitution = TRUE ;
	page << htmlLiteral( converted ) ;
	converted = "" ;
	page << *object->element_ptr ;
	break ;
	}

	item = object_list.Next( item ) ;
	}
	}

	// If token is a form field
	if ( perform_substitution )
	{
	value = server( token ) ;
	value.RTrim() ;

	converted += value ;
	}
	else if ( ! object_substitution )
	{
	// put raw token back into output string
	converted += "$" + token ;
	}
	}

	// append any remaining raw data
	converted += raw ;
	page << htmlLiteral( converted ) ;
	}

	fclose( file ) ;
	}
	else
	{
	htmlContainer error_page ;
	error_page << htmlBreak()
	<< "Unable to open document template file: "
	<< htmlText(filename)
	<< htmlBreak() ;
	page << error_page ;
	}
	}

	int main( void )
	{
	htmlCgi server( cin ) ;
	htmlPage page ;

	CLinkedList object_list ;

	// Create an object that represents the contents to
	// be included in the template document. This could be
	// as complex as you like, including entire tables, text,
	// or any other document.
	htmlContainer msg ;
	msg << htmlBold( "This is the substituted message" ) ;

	// Create an object that will replace the
	// "$Message" string in the document template file.
	PObjectDef object_ptr = new ObjectDef ;
	if ( object_ptr )
	{
	object_ptr->name = "Message" ;
	object_ptr->element_ptr = &msg ;
	object_list.Add( new CListItem( (DWord) object_ptr ) ) ;
	}

	// Load the HTML document template, specifying
	// the list of objects that are available for
	// substitution. This will replace any occurance
	// of "$Message" in the template with the msg object.
	htmlContainer dynamic_doc ;
	LoadTemplate( error_page, dynamic_doc,
	server, object_list ) ;

	// Output the new dymanically created page
	page << dynamic_doc ;
	server << page ;
	return 0 ;
	}