C++ and XML...
Kit Plummer
plug-devel@lists.PLUG.phoenix.az.us
Wed Jul 18 14:45:01 2001
Compiled the code. It works as advertised. I like the style...as if I
knew what good style is :}
-----
I have mentioned a Windoze-based laptop solution in past messages.
Well, I just remembered another reason why this would be something to
look into.
Many private pilots are using pen-based computers as replacements for
paper charts (the maps of airways and airports, approach plans, and
other flight information.) In addition, the pen-based computers can be
rigged with a GPS receiver to add moving-map functionality. However, it
would be relatively difficult to rig up the pilot's headset through the
laptop. In addition, in the event the laptop failed the pilot would be
without comm until he rerouted his headset to the main plugs.
-----
I am going to play around with adding some functionality to this for the
question and answer session...we'll see how it goes.
Kit
On 18 Jul 2001 16:02:37 -0700, Rob Wehrli wrote:
> Kit Plummer wrote:
> >
>
> Here is a very quick example in C that can easily be extended to produce
> results useful in prototyping your application. It uses expat, which is
> probably the easiest to use C-based, non-validating parser available.
> Expat is extremely fast and great for quickly parsing even huge XML
> files. (I've easily parsed 180MB files in a few seconds.)
>
> You can find expat at: http://www.jclark.com/xml/expat.html
>
> It compiles easily for Win32 and Linux. Note that you'll have to
> produce your own Linux library as the default installation doesn't do it
> for you. I think that I simply copied all of its .o files to a "lib"
> directory and used ar to create libexpat.a (as is used in the Makefile
> example below).
>
> You'll note that I didn't get far enough into it to put a lot of
> comments into it. You can see the commented out handler function calls
> that are not implemented, but easily could be given more time and
> perhaps a purpose... :) Note how the "Response" elements' data are not
> being reported as no handler is assigned. I could easily add the
> handler function to output it, but something more than just writing it
> to screen should be done...such as a function call to a TTS engine.
>
> You'll obviously note that this code simply parses the XML data file and
> does none of the application-specific work, but what else would you
> expect for a 20 minute hack?! :) Seriously, there would be a useful
> bit of code written that would use the functions implemented here to be
> a real application, but this should give you an idea of at least one way
> to successfully use Linux to rapidly parse through XML and handle it as
> desired. There are at least 50 different ways to handle element
> recognition and branching that I didn't implement here for brevity and
> simplicity, but I'd definitely recommend them for a "full-featured"
> application...however, at the same time, with just a few elements that
> are not likely to change names, hardcoding them isn't all bad! ;)
>
> If nothing else, at least you folks will get to see some of my "coding
> style" and have an opportunity to disagree with my use of braces, white
> space and other "religious" features! BTW...if anyone has any questions
> regarding the code, don't hesitate to ask.
>
> Take Care.
>
> Rob!
>
>
> ----------------checklist.xml----------------
>
> <?xml version="1.0"?>
> <CoPilot>
> <CheckList Name="PREFLIGHT" Identity="00000001">
> <!-- Preflight checklist prompts -->
> <Challenge Value="Aircraft Documents?">
> <Response>Check</Response>
> </Challenge>
> <Challenge Value="Battery On?">
> <Response>Check</Response>
> </Challenge>
> <Challenge Value="Flaps Down?">
> <Response>Check</Response>
> </Challenge>
> </CheckList>
> <CheckList Name="TAXI" Identity="00000002">
> <!-- Taxi checklist prompts -->
> <Challenge Value="Aircraft Documents?">
> <Response>Check</Response>
> </Challenge>
> <Challenge Value="Battery On?">
> <Response>Check</Response>
> </Challenge>
> <Challenge Value="Flaps Down?">
> <Response>Check</Response>
> </Challenge>
> </CheckList>
> <Response Value="Check" Invalid="0x10200FEA"/>
> </CoPilot>
>
> (Note that the last Response element can be stripped, or others changed
> similarly or the "0x10200FEA" can be replaced with other branching or
> prompt information.)
>
> ----------------CoPilot.c----------------
>
> /******************************************************
> *
> * FILENAME: CoPilot.c
> * AUTHOR: Rob Wehrli
> * DATE: 18 JULY 2001
> * COPYRIGHT: Copyright 2001 by Rob Wehrli
> * LICENSE: GPL v2.0 or later
> * PURPOSE: Implementation of CoPilot Application
> *
> ******************************************************/
>
> #ifndef _CoPilot_h_
> #include "CoPilot.h"
> #endif /* _CoPilot_h_ */
>
> /* Globals */
> XML_Parser g_parser = NULL;
> FILE *g_InFile = NULL;
> FILE *g_OutFile = NULL;
>
> /******************************************************
> *
> * StartElement()
> *
> ******************************************************/
> void StartElement( void *userData, const char *name, const char **atts )
> {
> int iAttributes = XML_GetSpecifiedAttributeCount( g_parser );
> if( strcmp( name, "CoPilot" ) == 0 )
> {
> printf( "CoPilot\n" );
> return;
> }
>
> if( strcmp( name, "CheckList" ) == 0 )
> {
> printf( "CheckList\n" );
> if( iAttributes )
> ShowAttributes( iAttributes, atts );
> return;
> }
>
> if( strcmp( name, "Challenge" ) == 0 )
> {
> printf( "Challenge\n" );
> if( iAttributes )
> ShowAttributes( iAttributes, atts );
> /* XML_SetCharacterDataHandler( g_parser, ChallengeDataHandler ); */
> return;
> }
>
> if( strcmp( name, "Response" ) == 0 )
> {
> printf( "Response\n" );
> if( iAttributes )
> ShowAttributes( iAttributes, atts );
> /* XML_SetCharacterDataHandler( g_parser, ResponseDataHandler ); */
> return;
> }
>
> return;
> }
>
> /******************************************************
> *
> * EndElement()
> *
> ******************************************************/
> void EndElement( void *userData, const char *name )
> {
>
> }
>
> /******************************************************
> *
> * ElementData()
> *
> ******************************************************/
> void ElementData( void *userData, const XML_Char *s, int len )
> {
> char* str = (char*)malloc( len + sizeof( char ) );
> memset( str, '\0', len + sizeof( char ) );
> strncpy( str, s, len );
> /* printf( "%s\n", str ); */
> /* fprintf( g_OutFile, str ); */
> free( str );
> }
>
> /******************************************************
> *
> * DataHandler()
> *
> ******************************************************/
>
> void DataHandler( void *userData, const XML_Char *s, int len )
> {
> char* str = (char*)malloc( len + 1 );
> memset( str, '\0', len + 1 );
> strncpy( str, s, len );
> fprintf( g_OutFile, "\t Data: " );
> fprintf( g_OutFile, str );
> fprintf( g_OutFile, CRLF );
> free( str );
>
> XML_SetCharacterDataHandler( g_parser, ElementData );
> }
>
> /******************************************************
> *
> * ShowAttributes()
> *
> ******************************************************/
> void ShowAttributes( int iAttributes, const char **atts )
> {
> int i = 0;
> for( i; i < iAttributes; i++ )
> {
> printf( "Attribute: %s\n", atts[i] );
> }
> }
>
> /******************************************************
> *
> * Usage()
> *
> ******************************************************/
> int Usage()
> {
> printf( "Usage: CoPilot infile.xml outfile.log\n" );
> return -1;
> }
>
> /******************************************************
> *
> * main()
> *
> ******************************************************/
> int main( int argc, char *argv[] )
> {
> char buf[BUFSIZ];
> int done;
> int depth = 0;
>
> if( argc < 3 )
> return Usage();
>
> g_InFile = fopen( argv[1], "r" );
> g_OutFile = fopen( argv[2], "w" );
>
> if( !g_InFile || !g_OutFile )
> return -1;
>
> g_parser = XML_ParserCreate( NULL );
>
> XML_SetUserData( g_parser, &depth );
> XML_SetElementHandler( g_parser, StartElement, EndElement );
> XML_SetCharacterDataHandler( g_parser, ElementData );
> do
> {
> size_t len = fread( buf, 1, sizeof( buf ), g_InFile );
> done = len < sizeof( buf );
> if( !XML_Parse( g_parser, buf, len, done ) )
> {
> fprintf( g_OutFile, "%s at line %d\n",
> XML_ErrorString( XML_GetErrorCode( g_parser ) ),
> XML_GetCurrentLineNumber( g_parser ) );
> return 1;
> }
> } while( !done );
> XML_ParserFree( g_parser );
> if( g_InFile )
> fclose( g_InFile );
> if( g_OutFile )
> fclose( g_OutFile );
> return 0;
> }
>
> ----------------CoPilot.h----------------
>
> /******************************************************
> *
> * FILENAME: CoPilot.h
> * AUTHOR: Rob Wehrli
> * DATE: 18 JULY 2001
> * COPYRIGHT: Copyright 2001 by Rob Wehrli
> * LICENSE: GPL v2.0 or later
> * PURPOSE: Definitions for CoPilot Application
> *
> ******************************************************/
>
> #ifndef _CoPilot_h_
> #define _CoPilot_h_
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <string.h>
>
> /*
> Expat Freeware C XML Parser
> See include file for open licensing agreement
> */
> #include <xmlparse.h>
>
> #define TAG_SLASH "/"
> #define TAG_GT ">"
> #define TAG_LT "<"
>
> #define CRLF "\r\n"
>
> /*
> Function Declarations
> */
> void StartElement( void *userData, const char *name, const char **atts
> );
> void ElementData( void *userData, const XML_Char *s, int len );
> void EndElement( void *userData, const char *name );
>
> void ShowAttributes( int iAttributes, const char **atts );
>
> int Usage();
> int main( int argc, char *argv[] );
>
>
> #endif /* _CoPilot_h_ */
>
>
> ----------------output----------------
>
> CoPilot
> CheckList
> Attribute: Name
> Attribute: PREFLIGHT
> Attribute: Identity
> Attribute: 00000001
> Challenge
> Attribute: Value
> Attribute: Aircraft Documents?
> Response
> Challenge
> Attribute: Value
> Attribute: Battery On?
> Response
> Challenge
> Attribute: Value
> Attribute: Flaps Down?
> Response
> CheckList
> Attribute: Name
> Attribute: TAXI
> Attribute: Identity
> Attribute: 00000002
> Challenge
> Attribute: Value
> Attribute: Aircraft Documents?
> Response
> Challenge
> Attribute: Value
> Attribute: Battery On?
> Response
> Challenge
> Attribute: Value
> Attribute: Flaps Down?
> Response
> Response
> Attribute: Value
> Attribute: Check
> Attribute: Invalid
> Attribute: 0x10200FEA
>
> ----------------Makefile----------------
>
> ###############################################
> # FILENAME: Makefile
> # AUTHOR: Rob Wehrli
> # COPYRIGHT: Copyright 2001 by Rob Wehrli
> # LICENSE: GPL v2.0 or later
> # PURPOSE: Makefile for CoPilot
> ###############################################
>
> CC = gcc
> CFLAGS = -g
>
> # change to your expat install location
> EXPAT = ../../expat/
>
> INCLUDE = -I$(EXPAT)include/
> LIBPATH = -L$(EXPAT)lib/
> LIBRARY = -lexpat
>
> EXE = CoPilot
>
> all: clean $(EXE)
>
> $(EXE): $(EXE).c $(EXE).h
> $(CC) $(CFLAGS) $(INCLUDE) -o $(EXE) $(EXE).c $(LIBPATH) $(LIBRARY)
>
> clean:
> rm -f $(EXE) $(EXE).o
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