TIP #83: AUGMENT TCL_EVALFILE WITH TCL_EVALCHANNEL AND TCL_EVALURL 
====================================================================
 Version:      $Revision: 1.6 $
 Author:       Marian Szczepkowski <marian_at_mail.jozep.com.au>
               <dgp_at_users.sf.net>
 State:        Withdrawn
 Type:         Project
 Tcl-Version:  8.5
 Vote:         Pending
 Created:      Thursday, 24 January 2002
 URL:          https://tip.tcl-lang.org83.html
 Post-History: 

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 ABSTRACT 
==========

 This TIP adds the ability to load Tcl files directly from URLs to the 
 core, together with a basic mechanism to simply evaluate a stream of 
 characters from a channel. 

 PROPOSAL 
==========

 I propose to split the /Tcl_EvalFile/ function into two components to 
 enable the [source] command to use URL's to obtain source material. 

 This will mean splitting /Tcl_EvalFile/ into /Tcl_EvalFile/ and 
 /Tcl_EvalChannel/ which are the two logical entities. Maintaining 
 /Tcl_EvalFile/ will preserve backward compatability. 

 Creating /Tcl_EvalChannel/ will provide generic functionality for 
 future use. 

 Adding /Tcl_EvalUrl/ will enable handling standard URL format strings. 

 This would enable this [source <URL:http://anywhere.com/file.tcl>] to 
 be used. 

 Code will also need to be added to /Tcl_SourceObjCmd/ to select 
 functionality requested. 

 PRO. 
======

 In a corporate environment where scripts are subject to change but the 
 interface is not, this allows scripts to be stored remotely on a 
 central server. 

 This also allows Tcl to interwork in a networked environment. 

 CON. 
======

 Security!!!! 

 This may mean in the long run adding a signing layer, but don't use it 
 if you don't want to. 

 SAMPLE 
========

 I figure it looking something like this. Snipped from 8.3 source. 

 TCL_SOURCEOBJCMD 
==================

   int
   Tcl_SourceObjCmd(dummy, interp, objc, objv)
       ClientData dummy;           /* Not used. */
       Tcl_Interp *interp;         /* Current interpreter. */
       int objc;                   /* Number of arguments. */
       Tcl_Obj *CONST objv[];      /* Argument objects. */
   {
       char *bytes;
       int result;
   
       if (objc != 2) {
           Tcl_WrongNumArgs(interp, 1, objv, "fileName");
           return TCL_ERROR;
       }
   
       bytes = Tcl_GetString(objv[1]);
       if (strstr(ptr,"://")) {
           result = Tcl_EvalFile(interp, bytes);
       } else {
           result = Tcl_EvalUrl(interp, bytes);
       }
       return result;
   }

 TCL_EVALFILE 
==============

   int
   Tcl_EvalFile(interp, fileName)
       Tcl_Interp *interp;         /* Interpreter in which to process file. */
       char *fileName;             /* Name of file to process.  Tilde-substitution
                                    * will be performed on this name. */
   {
       int result, length;
       struct stat statBuf;
       Interp *iPtr;
       Tcl_DString nameString;
       char *name, *string;
       Tcl_Channel chan;
       Tcl_Obj *objPtr;
   
       name = Tcl_TranslateFileName(interp, fileName, &nameString);
       if (name == NULL) {
           return TCL_ERROR;
       }
   
       result = TCL_ERROR;
   
       if (TclStat(name, &statBuf) == -1) {
           Tcl_SetErrno(errno);
           Tcl_AppendResult(interp, "couldn't read file \"", fileName,
                   "\": ", Tcl_PosixError(interp), (char *) NULL);
           goto end;
       }
   
       chan = Tcl_OpenFileChannel(interp, name, "r", 0644);
       if (chan == (Tcl_Channel) NULL) {
           Tcl_ResetResult(interp);
           Tcl_AppendResult(interp, "couldn't read file \"", fileName,
                   "\": ", Tcl_PosixError(interp), (char *) NULL);
           goto end;
       }
   
       result = Tcl_EvalChannel(interp, chan);
   
     end:
       Tcl_DStringFree(&nameString);
       return result;
   }

 TCL_EVALURL 
=============

   int
   Tcl_EvalUrl(interp, fileName)
       Tcl_Interp *interp; /* Interpreter in which to process file. */
       char *fileName;     /* Name of URL to process. */
   {
       return TCL_ERROR;
   }

 TCL_EVALCHANNEL 
=================

   int
   Tcl_EvalChannel(interp, chan)
       Tcl_Interp *interp; /* Interpreter in which to process file. */
       Tcl_Channel chan;   /* Name of file to process. */
   {
       int result, length;
       struct stat statBuf;
       char *oldScriptFile;
       Interp *iPtr;
       char *name, *string;
       Tcl_Obj *objPtr;
   
       result = TCL_ERROR;
       objPtr = Tcl_NewObj();
   
       if (Tcl_ReadChars(chan, objPtr, -1, 0) < 0) {
           Tcl_Close(interp, chan);
           Tcl_AppendResult(interp, "couldn't read file \"", fileName,
                   "\": ", Tcl_PosixError(interp), (char *) NULL);
           goto end;
       }
       if (Tcl_Close(interp, chan) != TCL_OK) {
           goto end;
       }
   
       iPtr = (Interp *) interp;
       oldScriptFile = iPtr->scriptFile;
       iPtr->scriptFile = fileName;
       string = Tcl_GetStringFromObj(objPtr, &length);
       result = Tcl_EvalEx(interp, string, length, 0);
       iPtr->scriptFile = oldScriptFile;
   
       if (result == TCL_RETURN) {
           result = TclUpdateReturnInfo(iPtr);
       } else if (result == TCL_ERROR) {
           char msg[200 + TCL_INTEGER_SPACE];
   
           /*
            * Record information telling where the error occurred.
            */
   
           sprintf(msg, "\n    (file \"%.150s\" line %d)", fileName,
                   interp->errorLine);
           Tcl_AddErrorInfo(interp, msg);
       }
   
     end:
       Tcl_DecrRefCount(objPtr);
       return result;
   }

 COMMENTS 
==========

 The VFS extension interface of Tcl 8.4 plus the tclvfs and vfs::http 
 packages provide the ability to [source] an URL. I believe that makes 
 this proposal out of date. 

 COPYRIGHT 
===========

 This document has been placed in the public domain. 

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