/*

 * 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;

}