Migrating C Code to C++ Builder

[BugHunter]

Hello C/C++ Gurus,

Could someone give me a quick hint, how to make this piece of C code Borland Builder-worthy? Or just explain the meaning of this piece of code. I try to compile a cross-plattform application named JSBSim (jsbsim.sourceforge.net) with Borland Builder 6 and the compiler came up with following syntax intepretation problem:

const ENCODING *
NS(XmlGetUtf8InternalEncoding)(void)
{
  return &ns(internal_utf8_encoding).enc;
}
 

I coded with delphi untill now and don't understand this syntactic construct.


Many thanks in advance

[Banfa]

You haven't provide enough context to make an answer possible.

This code is declaring a function returning const ENCODING * and taking no parameters. The function name is NS(XmlGetUtf8InternalEncoding). However ( and ) are not valid identifiers in a function name so something sneaky must be going on, I would assume that NS is a macro, you will need to find it to work out what it is doing, some possibilities are (but not limited to)

#define NS(x) x
#define NS(x) NS_##x

The function returns &ns(internal_utf8_encoding).enc;

In English this would be a pointer (&) to the enc member (.enc) of a structure, union or class returned from the function ns (ns(...)) when it is passed the value internal_utf8_encoding.

Unless, of course, ns is also a macro (although normally by convention most people use upper case for macros) in which case it could be something else.

[BugHunter]

Thanks for the quick responce, Banfa.

The code i reference here is expat XML parser integrated per include into JSBSim cross-plattform FDM application. here is the entire code of the "xmltok_ns.c":

const ENCODING *
NS(XmlGetUtf8InternalEncoding)(void)
{
  return &ns(internal_utf8_encoding).enc;
}
 
const ENCODING *
NS(XmlGetUtf16InternalEncoding)(void)
{
#if BYTEORDER == 1234
  return &ns(internal_little2_encoding).enc;
#elif BYTEORDER == 4321
  return &ns(internal_big2_encoding).enc;
#else
  const short n = 1;
  return (*(const char *)&n
          ? &ns(internal_little2_encoding).enc
          : &ns(internal_big2_encoding).enc);
#endif
}
 
static const ENCODING *NS(encodings)[] = {
  &ns(latin1_encoding).enc,
  &ns(ascii_encoding).enc,
  &ns(utf8_encoding).enc,
  &ns(big2_encoding).enc,
  &ns(big2_encoding).enc,
  &ns(little2_encoding).enc,
  &ns(utf8_encoding).enc /* NO_ENC */
};
 
static int PTRCALL
NS(initScanProlog)(const ENCODING *enc, const char *ptr, const char *end,
                   const char **nextTokPtr)
{
  return initScan(NS(encodings), (const INIT_ENCODING *)enc,
                  XML_PROLOG_STATE, ptr, end, nextTokPtr);
}
 
static int PTRCALL
NS(initScanContent)(const ENCODING *enc, const char *ptr, const char *end,
                    const char **nextTokPtr)
{
  return initScan(NS(encodings), (const INIT_ENCODING *)enc,
                  XML_CONTENT_STATE, ptr, end, nextTokPtr);
}
 
int
NS(XmlInitEncoding)(INIT_ENCODING *p, const ENCODING **encPtr,
                    const char *name)
{
  int i = getEncodingIndex(name);
  if (i == UNKNOWN_ENC)
    return 0;
  SET_INIT_ENC_INDEX(p, i);
  p->initEnc.scanners[XML_PROLOG_STATE] = NS(initScanProlog);
  p->initEnc.scanners[XML_CONTENT_STATE] = NS(initScanContent);
  p->initEnc.updatePosition = initUpdatePosition;
  p->encPtr = encPtr;
  *encPtr = &(p->initEnc);
  return 1;
}
 
static const ENCODING *NS(findEncoding)(const ENCODING *enc, const char *ptr, const char *end){
#define ENCODING_MAX 128
  char buf[ENCODING_MAX];
  char *p = buf;
  int i;
  XmlUtf8Convert(enc, &ptr, end, &p, p + ENCODING_MAX - 1);
  if (ptr != end)
    return 0;
  *p = 0;
  if (streqci(buf, KW_UTF_16) && enc->minBytesPerChar == 2)
    return enc;
  i = getEncodingIndex(buf);
  if (i == UNKNOWN_ENC)
    return 0;
  return NS(encodings)[i];
}
 
int NS(XmlParseXmlDecl)(int isGeneralTextEntity,
                    const ENCODING *enc,
                    const char *ptr,
                    const char *end,
                    const char **badPtr,
                    const char **versionPtr,
                    const char **versionEndPtr,
                    const char **encodingName,
                    const ENCODING **encoding,
                    int *standalone){
  return doParseXmlDecl(NS(findEncoding),
                        isGeneralTextEntity,
                        enc,
                        ptr,
                        end,
                        badPtr,
                        versionPtr,
                        versionEndPtr,
                        encodingName,
                        encoding,
                        standalone);
}
 
 

[Banfa]

here is the entire code of the "xmltok_ns.c":

I find this statement hard to believe, I would have expected to see some

#include

statements at the top of the file.

You need to find the definition of NS which is clearly not in this file so must be in another file.

[BugHunter]

Hello Banfa,

This will hopefully solve the problem. The most helpfull hint is your explanation about the syntax meaning here. Many thanks!

I find this statement hard to believe, I would have expected to see some

BTW, try following: copy/paste the first line of the code and "google" for it. One of the first pages is the expat XML cvs web view and the source file looks exactly the same way as my copy. Should i fail in assembling broken pieces together, i just throw away entire XML parser thingy and'll try it my way.

Thanks again!

[Banfa]

Right that makes things clearer, this file is not meant to be compiled stand alone, you have chosen to ask about 1 file out of context.

The context of this file is that it is included into xmltok.c and it is included like this

#define NS(x) x
#define ns(x) x
#include "xmltok_ns.c"
#undef NS
#undef ns
 

The definitions result in the code in xmltok_ns.c taking a compilable form.

Are you familar with #define and what it does?

Anyway the code for the expat module compiles for me straight out of the box, so I guess that it's worth using.

You should not try to be compiling

xmltok_ns.c
xmltok_impl.c

they are not meant for direct compilation but for inclusion into xmltok.c

[BugHunter]

Wow Banfa,

I really didn't hope to solve my problem that easy :D. The project i try to compile is JSBSim, which uses expat to read in flight dynamics (XML tables).

I attempt to compile it with Borland Builder and have no project file for this compiler, in other words i set the inclusion paths and include sources into the project file one by one referencing the compiler error messages. So far, i was lucky to recreate entire JSBSim project, but as soon as it got to expat inclusion i stuck :D. No it won't be a problem at all i guess.

This is what i call the perfect refernce and helper board! Thank you very much!

P.S. I will get on configured PC tonight and give a try. Most probably it will work, i'll let you know tomorrow :).

P.P.S. I should learn C++. It's one of the languages looking elegant and powerfull for coding more complex stuff. Sofar i have been involved in some Delphi projects and the class architecture in Object Pascal appeared to be not that way flexible as it is in C++ (templating'n stuff).

[BugHunter]

Hello Banfa,
I changed the inclusion strategy in the project file and digged for DEFINES in the Visual Studio project file used to compile FlightGear (JSBSim is used here as a subset). As expected, after inserting the defines the compilation went totally diferent way but stuck again at the xmltok_ns.c. This time compiler was unable to handle constant symbol findEncoding: this string (my most basic description for this code-beeing) doesn't exist in any other source file. I also tried to grep for it in original expat 1.9... and 2.0.0: without any luck. This textual element appears to exist only in this source file and should probably belong to external source like compiler header library... will see... exploration goes on.

[SimBuilder]

BugHunter (and Banfa),

Thanks for pursuing this problem. I just happened to Google the web with the same problem that BugHunter is having. However, I'm building JSBSim in a Microsoft Visual C++ (v7.1) environment.

Here's what's going on:
The file that you are having the problem building is xmltok_ns.c . This is not a "complete" C file, rather it is only part of a file that is included by xmltok.c, as showin the in following section of xmltok.c

#define NS(x) x
#define ns(x) x
#include "xmltok_ns.c"
#undef NS
#undef ns

#ifdef XML_NS

#define NS(x) x ## NS
#define ns(x) x ## _ns

#include "xmltok_ns.c"

#undef NS
#undef ns

Solution: Remove xmltok_ns.c from your build list and just build xmltok.c . Also, make sure you have the correct includes at the top of xmltok.c (i.e., COMPILED_FROM_DSP for Win32 platforms).
FYI: It took two people to track down this little "trick" by the author...