/*

  * tclResolve.c --

  *

  *      Contains hooks for customized command/variable name resolution

  *      schemes.  These hooks allow extensions like [incr Tcl] to add

  *      their own name resolution rules to the Tcl language.  Rules can

  *      be applied to a particular namespace, to the interpreter as a

  *      whole, or both.

  *

  * Copyright (c) 1998 Lucent Technologies, Inc.

  *

  * See the file "license.terms" for information on usage and redistribution

  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.

  *

  * RCS: @(#) $Id: tclResolve.c,v 1.4 2002/01/25 22:01:32 dgp Exp $

  */

 #include "tclInt.h"

 /*

  * Declarations for procedures local to this file:

  */

 static void		BumpCmdRefEpochs _ANSI_ARGS_((Namespace *nsPtr));

 /*

  *----------------------------------------------------------------------

  *

  * Tcl_AddInterpResolvers --

  *

  *	Adds a set of command/variable resolution procedures to an

  *	interpreter.  These procedures are consulted when commands

  *	are resolved in Tcl_FindCommand, and when variables are

  *	resolved in TclLookupVar and LookupCompiledLocal.  Each

  *	namespace may also have its own set of resolution procedures

  *	which take precedence over those for the interpreter.

  *

  *	When a name is resolved, it is handled as follows.  First,

  *	the name is passed to the resolution procedures for the

  *	namespace.  If not resolved, the name is passed to each of

  *	the resolution procedures added to the interpreter.  Finally,

  *	if still not resolved, the name is handled using the default

  *	Tcl rules for name resolution.

  *

  * Results:

  *	Returns pointers to the current name resolution procedures

  *	in the cmdProcPtr, varProcPtr and compiledVarProcPtr

  *	arguments.

  *

  * Side effects:

  *	If a compiledVarProc is specified, this procedure bumps the

  *	compileEpoch for the interpreter, forcing all code to be

  *	recompiled.  If a cmdProc is specified, this procedure bumps

  *	the cmdRefEpoch in all namespaces, forcing commands to be

  *	resolved again using the new rules.

  *

  *----------------------------------------------------------------------

  */

 void

 Tcl_AddInterpResolvers(interp, name, cmdProc, varProc, compiledVarProc)

     Tcl_Interp *interp;			/* Interpreter whose name resolution

 					 * rules are being modified. */

     CONST char *name;			/* Name of this resolution scheme. */

     Tcl_ResolveCmdProc *cmdProc;	/* New procedure for command

 					 * resolution */

     Tcl_ResolveVarProc *varProc;	/* Procedure for variable resolution

 					 * at runtime */

     Tcl_ResolveCompiledVarProc *compiledVarProc;

 					/* Procedure for variable resolution

 					 * at compile time. */

 {

     Interp *iPtr = (Interp*)interp;

     ResolverScheme *resPtr;

     /*

      *  Since we're adding a new name resolution scheme, we must force

      *  all code to be recompiled to use the new scheme.  If there

      *  are new compiled variable resolution rules, bump the compiler

      *  epoch to invalidate compiled code.  If there are new command

      *  resolution rules, bump the cmdRefEpoch in all namespaces.

      */

     if (compiledVarProc) {

         iPtr->compileEpoch++;

     }

     if (cmdProc) {

         BumpCmdRefEpochs(iPtr->globalNsPtr);

     }

     /*

      *  Look for an existing scheme with the given name.  If found,

      *  then replace its rules.

      */

     for (resPtr = iPtr->resolverPtr; resPtr != NULL; resPtr = resPtr->nextPtr) {

         if (*name == *resPtr->name && strcmp(name, resPtr->name) == 0) {

             resPtr->cmdResProc = cmdProc;

             resPtr->varResProc = varProc;

             resPtr->compiledVarResProc = compiledVarProc;

             return;

         }

     }

     /*

      *  Otherwise, this is a new scheme.  Add it to the FRONT

      *  of the linked list, so that it overrides existing schemes.

      */

     resPtr = (ResolverScheme *) ckalloc(sizeof(ResolverScheme));

     resPtr->name = (char*)ckalloc((unsigned)(strlen(name)+1));

     strcpy(resPtr->name, name);

     resPtr->cmdResProc = cmdProc;

     resPtr->varResProc = varProc;

     resPtr->compiledVarResProc = compiledVarProc;

     resPtr->nextPtr = iPtr->resolverPtr;

     iPtr->resolverPtr = resPtr;

 }

 /*

  *----------------------------------------------------------------------

  *

  * Tcl_GetInterpResolvers --

  *

  *	Looks for a set of command/variable resolution procedures with

  *	the given name in an interpreter.  These procedures are

  *	registered by calling Tcl_AddInterpResolvers.

  *

  * Results:

  *	If the name is recognized, this procedure returns non-zero,

  *	along with pointers to the name resolution procedures in

  *	the Tcl_ResolverInfo structure.  If the name is not recognized,

  *	this procedure returns zero.

  *

  * Side effects:

  *	None.

  *

  *----------------------------------------------------------------------

  */

 int

 Tcl_GetInterpResolvers(interp, name, resInfoPtr)

     Tcl_Interp *interp;			/* Interpreter whose name resolution

 					 * rules are being queried. */

     CONST char *name;                   /* Look for a scheme with this name. */

     Tcl_ResolverInfo *resInfoPtr;	/* Returns pointers to the procedures,

 					 * if found */

 {

     Interp *iPtr = (Interp*)interp;

     ResolverScheme *resPtr;

     /*

      *  Look for an existing scheme with the given name.  If found,

      *  then return pointers to its procedures.

      */

     for (resPtr = iPtr->resolverPtr; resPtr != NULL; resPtr = resPtr->nextPtr) {

         if (*name == *resPtr->name && strcmp(name, resPtr->name) == 0) {

 	    resInfoPtr->cmdResProc = resPtr->cmdResProc;

 	    resInfoPtr->varResProc = resPtr->varResProc;

 	    resInfoPtr->compiledVarResProc = resPtr->compiledVarResProc;

             return 1;

         }

     }

     return 0;

 }

 /*

  *----------------------------------------------------------------------

  *

  * Tcl_RemoveInterpResolvers --

  *

  *	Removes a set of command/variable resolution procedures

  *	previously added by Tcl_AddInterpResolvers.  The next time

  *	a command/variable name is resolved, these procedures

  *	won't be consulted.

  *

  * Results:

  *	Returns non-zero if the name was recognized and the

  *	resolution scheme was deleted.  Returns zero otherwise.

  *

  * Side effects:

  *	If a scheme with a compiledVarProc was deleted, this procedure

  *	bumps the compileEpoch for the interpreter, forcing all code

  *	to be recompiled.  If a scheme with a cmdProc was deleted,

  *	this procedure bumps the cmdRefEpoch in all namespaces,

  *	forcing commands to be resolved again using the new rules.

  *

  *----------------------------------------------------------------------

  */

 int

 Tcl_RemoveInterpResolvers(interp, name)

     Tcl_Interp *interp;			/* Interpreter whose name resolution

 					 * rules are being modified. */

     CONST char *name;                   /* Name of the scheme to be removed. */

 {

     Interp *iPtr = (Interp*)interp;

     ResolverScheme **prevPtrPtr, *resPtr;

     /*

      *  Look for an existing scheme with the given name.

      */

     prevPtrPtr = &iPtr->resolverPtr;

     for (resPtr = iPtr->resolverPtr; resPtr != NULL; resPtr = resPtr->nextPtr) {

         if (*name == *resPtr->name && strcmp(name, resPtr->name) == 0) {

             break;

         }

         prevPtrPtr = &resPtr->nextPtr;

     }

     /*

      *  If we found the scheme, delete it.

      */

     if (resPtr) {

         /*

          *  If we're deleting a scheme with compiled variable resolution

          *  rules, bump the compiler epoch to invalidate compiled code.

          *  If we're deleting a scheme with command resolution rules,

          *  bump the cmdRefEpoch in all namespaces.

          */

         if (resPtr->compiledVarResProc) {

             iPtr->compileEpoch++;

         }

         if (resPtr->cmdResProc) {

             BumpCmdRefEpochs(iPtr->globalNsPtr);

         }

         *prevPtrPtr = resPtr->nextPtr;

         ckfree(resPtr->name);

         ckfree((char *) resPtr);

         return 1;

     }

     return 0;

 }

 /*

  *----------------------------------------------------------------------

  *

  * BumpCmdRefEpochs --

  *

  *	This procedure is used to bump the cmdRefEpoch counters in

  *	the specified namespace and all of its child namespaces.

  *	It is used whenever name resolution schemes are added/removed

  *	from an interpreter, to invalidate all command references.

  *

  * Results:

  *	None.

  *

  * Side effects:

  *	Bumps the cmdRefEpoch in the specified namespace and its

  *	children, recursively.

  *

  *----------------------------------------------------------------------

  */

 static void

 BumpCmdRefEpochs(nsPtr)

     Namespace *nsPtr;			/* Namespace being modified. */

 {

     Tcl_HashEntry *entry;

     Tcl_HashSearch search;

     Namespace *childNsPtr;

     nsPtr->cmdRefEpoch++;

     for (entry = Tcl_FirstHashEntry(&nsPtr->childTable, &search);

 	    entry != NULL;

 	    entry = Tcl_NextHashEntry(&search)) {

         childNsPtr = (Namespace *) Tcl_GetHashValue(entry);

         BumpCmdRefEpochs(childNsPtr);

     }

 }

 /*

  *----------------------------------------------------------------------

  *

  * Tcl_SetNamespaceResolvers --

  *

  *	Sets the command/variable resolution procedures for a namespace,

  *	thereby changing the way that command/variable names are

  *	interpreted.  This allows extension writers to support different

  *	name resolution schemes, such as those for object-oriented

  *	packages.

  *

  *	Command resolution is handled by a procedure of the following

  *	type:

  *

  *	  typedef int (Tcl_ResolveCmdProc) _ANSI_ARGS_((

  *		Tcl_Interp* interp, CONST char* name, Tcl_Namespace *context,

  *              int flags, Tcl_Command *rPtr));

  *          

  *	Whenever a command is executed or Tcl_FindCommand is invoked

  *	within the namespace, this procedure is called to resolve the

  *	command name.  If this procedure is able to resolve the name,

  *	it should return the status code TCL_OK, along with the

  *	corresponding Tcl_Command in the rPtr argument.  Otherwise,

  *	the procedure can return TCL_CONTINUE, and the command will

  *	be treated under the usual name resolution rules.  Or, it can

  *	return TCL_ERROR, and the command will be considered invalid.

  *

  *	Variable resolution is handled by two procedures.  The first

  *	is called whenever a variable needs to be resolved at compile

  *	time:

  *

  *        typedef int (Tcl_ResolveCompiledVarProc) _ANSI_ARGS_((

  *	        Tcl_Interp* interp, CONST char* name, Tcl_Namespace *context,

  *	        Tcl_ResolvedVarInfo *rPtr));

  *

  *      If this procedure is able to resolve the name, it should return

  *      the status code TCL_OK, along with variable resolution info in

  *      the rPtr argument; this info will be used to set up compiled

  *	locals in the call frame at runtime.  The procedure may also

  *	return TCL_CONTINUE, and the variable will be treated under

  *	the usual name resolution rules.  Or, it can return TCL_ERROR,

  *	and the variable will be considered invalid.

  *

  *	Another procedure is used whenever a variable needs to be

  *	resolved at runtime but it is not recognized as a compiled local.

  *	(For example, the variable may be requested via

  *	Tcl_FindNamespaceVar.) This procedure has the following type:

  *

  *	  typedef int (Tcl_ResolveVarProc) _ANSI_ARGS_((

  *	        Tcl_Interp* interp, CONST char* name, Tcl_Namespace *context,

  *	        int flags, Tcl_Var *rPtr));

  *

  *	This procedure is quite similar to the compile-time version.

  *	It returns the same status codes, but if variable resolution

  *	succeeds, this procedure returns a Tcl_Var directly via the

  *	rPtr argument.

  *

  * Results:

  *	Nothing.

  *

  * Side effects:

  *	Bumps the command epoch counter for the namespace, invalidating

  *	all command references in that namespace.  Also bumps the

  *	resolver epoch counter for the namespace, forcing all code

  *	in the namespace to be recompiled.

  *

  *----------------------------------------------------------------------

  */

 void

 Tcl_SetNamespaceResolvers(namespacePtr, cmdProc, varProc, compiledVarProc)

     Tcl_Namespace *namespacePtr;	/* Namespace whose resolution rules

 					 * are being modified. */

     Tcl_ResolveCmdProc *cmdProc;	/* Procedure for command resolution */

     Tcl_ResolveVarProc *varProc;	/* Procedure for variable resolution

 					 * at runtime */

     Tcl_ResolveCompiledVarProc *compiledVarProc;

 					/* Procedure for variable resolution

 					 * at compile time. */

 {

     Namespace *nsPtr = (Namespace*)namespacePtr;

     /*

      *  Plug in the new command resolver, and bump the epoch counters

      *  so that all code will have to be recompiled and all commands

      *  will have to be resolved again using the new policy.

      */

     nsPtr->cmdResProc = cmdProc;

     nsPtr->varResProc = varProc;

     nsPtr->compiledVarResProc = compiledVarProc;

     nsPtr->cmdRefEpoch++;

     nsPtr->resolverEpoch++;

 }

 /*

  *----------------------------------------------------------------------

  *

  * Tcl_GetNamespaceResolvers --

  *

  *	Returns the current command/variable resolution procedures

  *	for a namespace.  By default, these procedures are NULL.

  *	New procedures can be installed by calling

  *	Tcl_SetNamespaceResolvers, to provide new name resolution

  *	rules.

  *

  * Results:

  *	Returns non-zero if any name resolution procedures have been

  *	assigned to this namespace; also returns pointers to the

  *	procedures in the Tcl_ResolverInfo structure.  Returns zero

  *	otherwise.

  *

  * Side effects:

  *	None.

  *

  *----------------------------------------------------------------------

  */

 int

 Tcl_GetNamespaceResolvers(namespacePtr, resInfoPtr)

     Tcl_Namespace *namespacePtr;	/* Namespace whose resolution rules

 					 * are being modified. */

     Tcl_ResolverInfo *resInfoPtr;	/* Returns: pointers for all

 					 * name resolution procedures

 					 * assigned to this namespace. */

 {

     Namespace *nsPtr = (Namespace*)namespacePtr;

     resInfoPtr->cmdResProc = nsPtr->cmdResProc;

     resInfoPtr->varResProc = nsPtr->varResProc;

     resInfoPtr->compiledVarResProc = nsPtr->compiledVarResProc;

     if (nsPtr->cmdResProc != NULL ||

         nsPtr->varResProc != NULL ||

         nsPtr->compiledVarResProc != NULL) {

 	return 1;

     }

     return 0;

 }