naviserver-devel

[naviserver-devel] Fwd: [TCLCORE] TIP #265: A Convenient C-side Command Option Parser for Tcl

[Zoran V. <zv...@ar...>]

Hi!

It seems like Tcl is also going to do this.
Stephen, you might eventually comment on
that on tclcore list.

Cheers
Zoran

Anfang der weitergeleiteten E-Mail:

> Von: Sam Bromley <sa...@sa...>
> Datum: 4. April 2006 11:47:44 MESZ
> An: tcl...@li...
> Kopie: Sam Bromley <sa...@sa...>
> Betreff: [TCLCORE] TIP #265: A Convenient C-side Command Option  
> Parser for Tcl
> Antwort an: tcl...@li...
>
>
>  TIP #265: A CONVENIENT C-SIDE COMMAND OPTION PARSER FOR TCL
> =============================================================
>  Version:      $Revision: 1.2 $
>  Author:       Sam Bromley <sam_at_sambromley.com>
>  State:        Draft
>  Type:         Project
>  Tcl-Version:  8.5
>  Vote:         Pending
>  Created:      Monday, 03 April 2006
>  URL:          http://purl.org/tcl/tip/265.html
>  WebEdit:      http://purl.org/tcl/tip/edit/265
>  Post-History:
>
> ---------------------------------------------------------------------- 
> ---
>
>  ABSTRACT
> ==========
>
>  The Tk C library provides developers with a /Tk_ParseArgv/() function
>  that allows command line parsing of options of the "-option" form.
>  Archived discussions on <URL:news:comp.lang.tcl> and on the Wiki
>  indicate that a desire for similar functionality without Tk has  
> arisen
>  several times in the past. This TIP presents a Tk-free implementation
>  of /Tk_ParseArgv()/ named *Tcl_ParseArgv*, as well as a new function,
>  *Tcl_ParseArgvObj*, that developers can use to parse "-option" style
>  command options in C implementations of Tcl commands using the  
> Tcl_Obj
>  interface.
>
>  RATIONALE
> ===========
>
>  While the parsing of command options can be readily accomplished  
> on the
>  Tcl side, a uniform method for parsing "-option" formed options does
>  not exist on the C side. Many developers are familiar with the  
> ease of
>  use of libpopt-style command line parsing, but a similarly clean  
> method
>  does not currently exist in Tcl. The common approach is to use
>  /Tcl_GetIndexFromObj/(), yet this method alone does not allow the
>  flexibilty and ease of use of libpopt-style parsing.
>
>  One drawback of the classical /Tcl_GetIndexFromObj/()-only  
> approach is
>  the need to handle the specifies of your command option parsing for
>  each unique command. This leads to significant code duplication. A
>  libpopt-style approach is to bundle all of your parsing specifics  
> into
>  a single array of structures capturing the details, and then let a
>  specific parsing routine handle the parsing of every option for you.
>  The *Tcl_ParseArgvObj*() routine introduced in this TIP provides this
>  functionality, thereby allowing the removal of all parsing specifics
>  from the command implimentation other than that necessary to describe
>  each optional argument.
>
>  Additionally, a function *Tcl_ParseArgv* is provided to provide the
>  functionality of /Tk_ParseArgs/() to those who desire it. A  
> discussion
>  in 2002 on <URL:news:comp.lang.tcl>
>  [<URL:http://groups.google.com/group/comp.lang.tcl/browse_thread/ 
> thread/c4fea8f0346cf8ae/036961bf476a3b99? 
> q=tcl_parseargv&rnum=2#036961bf476a3b99>]
>  indicated that this is a desired feature. Arguments against a
>  *Tcl_ParseArgv* implementation include that it is better to do all
>  command line parsing on the Tcl side. However, this implies  
> writing two
>  wrapper functions: (i) A C implementation of a Tcl command; and  
> (ii) A
>  Tcl wrapper that pre-parses the options before calling the C command.
>  This can lead to significant duplication of effort when porting a  
> large
>  project to a Tcl enabled version. This point is particularly relevent
>  in the context of *Tcl_ParseArgvObj*(), as then one is not assuming
>  that one can simply replace the main() routine with Tcl, but rather
>  that one is truly embedding the C side in a larger system.
>
>  *Tcl_ParseArgvObj*() offers a clean method to enable flexible command
>  line parsing to C implementations of Tcl commands.
>
>  SPECIFICATION
> ===============
>
>  This document proposes the following changes to Tcl core:
>
>     1. Add /generic/tclArgv.c/ and /generic/tclArgv.h/ which  
> provide the
>        new library functions /Tcl_ParseArgv()/ and /Tcl_ParseArgvObj 
> ()/.
>
>     2. Modify /tcl.h/ to declare object types and functions needed by
>        /tclArgv.c/.
>
>  The function signatures of *Tcl_ParseArgv* and *Tcl_ParseArgsObjv*
>  shall be:
>
>        int *Tcl_ParseArgv*(Tcl_Interp */interp/, int */argcPtr/, char
>        **/argv/, const Tcl_ArgvInfo */argTable/, int /flags/)
>
>        int *Tcl_ParseArgsObjv*(Tcl_Interp */interp/, int */objcPtr/,
>        Tcl_Obj **/objv/, const Tcl_ArgvInfo */argTable/, int /flags/)
>
>  *Note* that the count of arguments (referred to by /argcPtr/ or
>  /objcPtr/) will be modified, as will the arrays indicated by / 
> argv/ and
>  /objv/. In particular, the arrays of arguments /must not/ be those
>  passed into the calling command.
>
>  REFERENCE IMPLEMENTATION
> ==========================
>
>  A working implementation has been submitted to the Feature Request
>  Tracker at SourceForge
>  [<URL:http://sf.net/tracker/? 
> func=detail&aid=1446696&group_id=10894&atid=360894>].
>
>  EXAMPLE OF USE
> ================
>
>    #include <tcl.h>
>    #include <tclArgv.h> /* not needed if subsumed into core */
>
>    int g_test_cmd(ClientData clientData, Tcl_Interp *interp,
>        int objc, Tcl_Obj *CONST objv[])
>    {
>      char *gname,*filename;
>      int i;
>      int numRepeat;
>      double scalar;
>      int doErase = 0;
>      size_t size;
>
>      /* this table specifies the possible options, all in one place.*/
>      Tcl_ArgvInfo argTable[] = {
>        {"-erase", TCL_ARGV_CONSTANT, (void *) 1, &doErase,
>          "erase image before plotting"},
>        {"-numRepeat", TCL_ARGV_INT, NULL, &numRepeat,
>          "number of times to repeat test"},
>        {"-scalar", TCL_ARGV_FLOAT, NULL, &scalar,
>          "scalar multiple to use for test"},
>        {"-outfile", TCL_ARGV_STRING, NULL, &filename,
>          "name of file to which to dump result"},
>        {NULL, TCL_ARGV_END, NULL, NULL, NULL}
>      };
>
>      /* need a local copy of Tcl_Obj array for manipulation */
>      size = (unsigned) (objc+1) * sizeof(Tcl_Obj*);
>      Tcl_Obj **private_objv = (Tcl_Obj**) ckalloc(size);
>      memcpy(private_objv, objv, size);
>
>      /* Call Tcl_ParseArgObjv to do all the parsing! */
>      if (Tcl_ParseArgsObjv(interp,&objc,private_objv,argTable,0) !=  
> TCL_OK) {
>         /* something went wrong. Error stored in interp's result */
>         ckfree(private_objv);
>         return TCL_ERROR;
>      }
>
>      /* at this point, any unhandled options are repacked in  
> private_objv */
>      gname = Tcl_GetString(private_obj[1]);
>
>      /* all done */
>      ckfree(private_objv);
>
>      /* rest of code continues here...*/
>
>      return TCL_OK;
>    }
>
>  COPYRIGHT
> ===========
>
>  This document has been placed in the public domain.
>
> ---------------------------------------------------------------------- 
> ---
>
>  TIP AutoGenerator - written by Donal K. Fellows
>
>
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Re: [naviserver-devel] Fwd: [TCLCORE] TIP #265: A Convenient C-side Command Option Parser for Tcl

[Stephen D. <sd...@gm...>]

Thanks, I'll take a look.


On 4/4/06, Zoran Vasiljevic <zv...@ar...> wrote:
> Hi!
>
> It seems like Tcl is also going to do this.
> Stephen, you might eventually comment on
> that on tclcore list.
>
> Cheers
> Zoran