/TCL/src/commands/NamespaceCmd.cs

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#undef DEBUG
/*
* NamespaceCmd.java
*
* Copyright (c) 1993-1997 Lucent Technologies.
* Copyright (c) 1997 Sun Microsystems, Inc.
* Copyright (c) 1998-1999 by Scriptics Corporation.
* Copyright (c) 1999 Moses DeJong
*
* Originally implemented by
*   Michael J. McLennan
*   Bell Labs Innovations for Lucent Technologies
*   mmclennan@lucent.com
*
* See the file "license.terms" for information on usage and
* redistribution of this file, and for a DISCLAIMER OF ALL
* WARRANTIES.
*
* Included in SQLite3 port to C# for use in testharness only;  2008 Noah B Hart
*
* RCS @(#) $Id: NamespaceCmd.java,v 1.12 2001/05/05 22:38:13 mdejong Exp $
*/
using System;
using System.Collections;
using System.Text;

namespace tcl.lang
{

  /// <summary> This class implements the built-in "namespace" command in Tcl.
  /// See the user documentation for details on what it does.
  /// </summary>


  public class NamespaceCmd : InternalRep, Command
  {

    // Flag passed to getNamespaceForQualName to indicate that it should
    // search for a namespace rather than a command or variable inside a
    // namespace. Note that this flag's value must not conflict with the values
    // of TCL.VarFlag.GLOBAL_ONLY, TCL.VarFlag.NAMESPACE_ONLY, or TCL.VarFlag.CREATE_NS_IF_UNKNOWN.


    // Initial size of stack allocated space for tail list - used when resetting
    // shadowed command references in the functin: TclResetShadowedCmdRefs.

    //private static final int NUM_TRAIL_ELEMS = 5;

    // Count of the number of namespaces created. This value is used as a
    // unique id for each namespace.

    private static long numNsCreated = 0;
    private static Object nsMutex;

    //
    // Flags used to represent the status of a namespace:
    //
    // NS_DYING -	1 means deleteNamespace has been called to delete the
    //		namespace but there are still active call frames on the Tcl
    //		stack that refer to the namespace. When the last call frame
    //		referring to it has been popped, it's variables and command
    //		will be destroyed and it will be marked "dead" (NS_DEAD).
    //		The namespace can no longer be looked up by name.
    // NS_DEAD -	1 means deleteNamespace has been called to delete the
    //		namespace and no call frames still refer to it. Its
    //		variables and command have already been destroyed. This bit
    //		allows the namespace resolution code to recognize that the
    //		namespace is "deleted". When the last namespaceName object
    //		in any byte code code unit that refers to the namespace has
    //		been freed (i.e., when the namespace's refCount is 0), the
    //		namespace's storage will be freed.

    internal const int NS_DYING = 0x01;
    internal const int NS_DEAD = 0x02;


    // Flag passed to getNamespaceForQualName to have it create all namespace
    // components of a namespace-qualified name that cannot be found. The new
    // namespaces are created within their specified parent. Note that this
    // flag's value must not conflict with the values of the flags
    // TCL.VarFlag.GLOBAL_ONLY, TCL.VarFlag.NAMESPACE_ONLY, and TCL.VarFlag.FIND_ONLY_NS

    // internal const int TCL.VarFlag.CREATE_NS_IF_UNKNOWN = 0x800;


    // This value corresponds to the Tcl_Obj.otherValuePtr pointer used
    // in the C version of Tcl 8.1. Use it to keep track of a ResolvedNsName.

    private ResolvedNsName otherValue = null;


    /*
    *----------------------------------------------------------------------
    *
    * Tcl_GetCurrentNamespace -> getCurrentNamespace
    *
    *	Returns a reference to an interpreter's currently active namespace.
    *
    * Results:
    *	Returns a reference to the interpreter's current namespace.
    *
    * Side effects:
    *	None.
    *
    *----------------------------------------------------------------------
    */

    internal static Namespace getCurrentNamespace( Interp interp )
    {
      if ( interp.varFrame != null )
      {
        return interp.varFrame.ns;
      }
      else
      {
        return interp.globalNs;
      }
    }

    /*
    *----------------------------------------------------------------------
    *
    * Tcl_GetGlobalNamespace -> getGlobalNamespace
    *
    *	Returns a reference to an interpreter's global :: namespace.
    *
    * Results:
    *	Returns a reference to the specified interpreter's global namespace.
    *
    * Side effects:
    *	None.
    *
    *----------------------------------------------------------------------
    */

    internal static Namespace getGlobalNamespace( Interp interp )
    {
      return interp.globalNs;
    }


    /*
    *----------------------------------------------------------------------
    *
    * Tcl_PushCallFrame -> pushCallFrame
    *
    *	Pushes a new call frame onto the interpreter's Tcl call stack.
    *	Called when executing a Tcl procedure or a "namespace eval" or
    *	"namespace inscope" command. 
    *
    * Results:
    *  Returns if successful, raises TclException if something goes wrong.
    *
    * Side effects:
    *	Modifies the interpreter's Tcl call stack.
    *
    *----------------------------------------------------------------------
    */

    internal static void pushCallFrame( Interp interp, CallFrame frame, Namespace namespace_Renamed, bool isProcCallFrame )
    // If true, the frame represents a
    // called Tcl procedure and may have local
    // vars. Vars will ordinarily be looked up
    // in the frame. If new variables are
    // created, they will be created in the
    // frame. If false, the frame is for a
    // "namespace eval" or "namespace inscope"
    // command and var references are treated
    // as references to namespace variables.
    {
      Namespace ns;

      if ( namespace_Renamed == null )
      {
        ns = getCurrentNamespace( interp );
      }
      else
      {
        ns = namespace_Renamed;
        if ( ( ns.flags & NS_DEAD ) != 0 )
        {
          throw new TclRuntimeError( "Trying to push call frame for dead namespace" );
        }
      }

      ns.activationCount++;
      frame.ns = ns;
      frame.isProcCallFrame = isProcCallFrame;
      frame.objv = null;

      frame.caller = interp.frame;
      frame.callerVar = interp.varFrame;

      if ( interp.varFrame != null )
      {
        frame.level = ( interp.varFrame.level + 1 );
      }
      else
      {
        frame.level = 1;
      }

      // FIXME : does Jacl need a procPtr in the CallFrame class?
      //frame.procPtr = null; 	   // no called procedure

      frame.varTable = null; // and no local variables

      // Compiled locals are not part of Jacl's CallFrame

      // Push the new call frame onto the interpreter's stack of procedure
      // call frames making it the current frame.

      interp.frame = frame;
      interp.varFrame = frame;
    }



    /*
    *----------------------------------------------------------------------
    *
    * Tcl_PopCallFrame -> popCallFrame
    *
    *	Removes a call frame from the Tcl call stack for the interpreter.
    *	Called to remove a frame previously pushed by Tcl_PushCallFrame.
    *
    * Results:
    *	None.
    *
    * Side effects:
    *	Modifies the call stack of the interpreter. Resets various fields of
    *	the popped call frame. If a namespace has been deleted and
    *	has no more activations on the call stack, the namespace is
    *	destroyed.
    *
    *----------------------------------------------------------------------
    */

    internal static void popCallFrame( Interp interp )
    {
      CallFrame frame = interp.frame;
      int saveErrFlag;
      Namespace ns;

      // It's important to remove the call frame from the interpreter's stack
      // of call frames before deleting local variables, so that traces
      // invoked by the variable deletion don't see the partially-deleted
      // frame.

      interp.frame = frame.caller;
      interp.varFrame = frame.callerVar;

      // Delete the local variables. As a hack, we save then restore the
      // ERR_IN_PROGRESS flag in the interpreter. The problem is that there
      // could be unset traces on the variables, which cause scripts to be
      // evaluated. This will clear the ERR_IN_PROGRESS flag, losing stack
      // trace information if the procedure was exiting with an error. The
      // code below preserves the flag. Unfortunately, that isn't really
      // enough: we really should preserve the errorInfo variable too
      // (otherwise a nested error in the trace script will trash errorInfo).
      // What's really needed is a general-purpose mechanism for saving and
      // restoring interpreter state.

      saveErrFlag = ( interp.flags & Parser.ERR_IN_PROGRESS );

      if ( frame.varTable != null )
      {
        Var.deleteVars( interp, frame.varTable );
        frame.varTable = null;
      }

      interp.flags |= saveErrFlag;

      // Decrement the namespace's count of active call frames. If the
      // namespace is "dying" and there are no more active call frames,
      // call Tcl_DeleteNamespace to destroy it.

      ns = frame.ns;
      ns.activationCount--;
      if ( ( ( ns.flags & NS_DYING ) != 0 ) && ( ns.activationCount == 0 ) )
      {
        deleteNamespace( ns );
      }
      frame.ns = null;
    }

    /*
    *----------------------------------------------------------------------
    *
    * Tcl_CreateNamespace --
    *
    *	Creates a new namespace with the given name. If there is no
    *	active namespace (i.e., the interpreter is being initialized),
    *	the global :: namespace is created and returned.
    *
    * Results:
    *	Returns a reference to the new namespace if successful. If the
    *	namespace already exists or if another error occurs, this routine
    *	returns null, along with an error message in the interpreter's
    *	result object.
    *
    * Side effects:
    *	If the name contains "::" qualifiers and a parent namespace does
    *	not already exist, it is automatically created. 
    *
    *----------------------------------------------------------------------
    */

    internal static Namespace createNamespace( Interp interp, string name, DeleteProc deleteProc )
    {
      Namespace ns, ancestor;
      Namespace parent;
      Namespace globalNs = getGlobalNamespace( interp );
      string simpleName;
      StringBuilder buffer1, buffer2;

      // If there is no active namespace, the interpreter is being
      // initialized. 

      if ( ( globalNs == null ) && ( interp.varFrame == null ) )
      {
        // Treat this namespace as the global namespace, and avoid
        // looking for a parent.

        parent = null;
        simpleName = "";
      }
      else if ( name.Length == 0 )
      {
        /*
        TclObject tobj = interp.getResult();
        // FIXME : is there a test case to check this error result?
        TclString.append(tobj,
        "can't create namespace \"\": only global namespace can have empty name");
        */

        // FIXME : is there a test case to check this error result?
        interp.setResult( "can't create namespace \"\": only global namespace can have empty name" );
        return null;
      }
      else
      {
        // Find the parent for the new namespace.

        // Java does not support passing an address so we pass
        // an array of size 1 and then assign arr[0] to the value
        Namespace[] parentArr = new Namespace[1];
        Namespace[] dummyArr = new Namespace[1];
        string[] simpleArr = new string[1];

        getNamespaceForQualName( interp, name, null, ( TCL.VarFlag.CREATE_NS_IF_UNKNOWN | TCL.VarFlag.LEAVE_ERR_MSG ), parentArr, dummyArr, dummyArr, simpleArr );

        // Get the values out of the arrays!
        parent = parentArr[0];
        simpleName = simpleArr[0];


        // If the unqualified name at the end is empty, there were trailing
        // "::"s after the namespace's name which we ignore. The new
        // namespace was already (recursively) created and is referenced
        // by parent.

        if ( simpleName.Length == 0 )
        {
          return parent;
        }

        // Check for a bad namespace name and make sure that the name
        // does not already exist in the parent namespace.

        if ( parent.childTable[simpleName] != null )
        {
          /*
          TclObject tobj = interp.getResult();
          // FIXME : is there a test case to check this error result?
          TclString.append(tobj,
          "can't create namespace \"" + name + "\": already exists");
          */

          // FIXME : is there a test case to check this error result?
          interp.setResult( "can't create namespace \"" + name + "\": already exists" );
          return null;
        }
      }

      // Create the new namespace and root it in its parent. Increment the
      // count of namespaces created.

      ns = new Namespace();
      ns.name = simpleName;
      ns.fullName = null; // set below
      //ns.clientData       = clientData;
      ns.deleteProc = deleteProc;
      ns.parent = parent;
      ns.childTable = new Hashtable();
      lock ( nsMutex )
      {
        numNsCreated++;
        ns.nsId = numNsCreated;
      }
      ns.interp = interp;
      ns.flags = 0;
      ns.activationCount = 0;
      // FIXME : there was a problem with the refcount because
      // when the namespace was deleted the refocount was 0.
      // We avoid this by just using a refcount of 1 for now.
      // We can do ignore the refCount because GC will reclaim mem.
      //ns.refCount           = 0;
      ns.refCount = 1;
      ns.cmdTable = new Hashtable();
      ns.varTable = new Hashtable();
      ns.exportArray = null;
      ns.numExportPatterns = 0;
      ns.maxExportPatterns = 0;

      // Jacl does not use these tcl compiler specific members
      //ns.cmdRefEpoch        = 0;
      //ns.resolverEpoch      = 0;

      ns.resolver = null;

      if ( parent != null )
      {
        SupportClass.PutElement( parent.childTable, simpleName, ns );
      }

      // Build the fully qualified name for this namespace.

      buffer1 = new StringBuilder();
      buffer2 = new StringBuilder();
      for ( ancestor = ns; ancestor != null; ancestor = ancestor.parent )
      {
        if ( ancestor != globalNs )
        {
          buffer1.Append( "::" );
          buffer1.Append( ancestor.name );
        }
        buffer1.Append( buffer2 );

        buffer2.Length = 0;
        buffer2.Append( buffer1 );
        buffer1.Length = 0;
      }

      name = buffer2.ToString();
      ns.fullName = name;

      // Return a reference to the new namespace.

      return ns;
    }

    /*
    *----------------------------------------------------------------------
    *
    * Tcl_DeleteNamespace -> deleteNamespace
    *
    *	Deletes a namespace and all of the commands, variables, and other
    *	namespaces within it.
    *
    * Results:
    *	None.
    *
    * Side effects:
    *	When a namespace is deleted, it is automatically removed as a
    *	child of its parent namespace. Also, all its commands, variables
    *	and child namespaces are deleted.
    *
    *----------------------------------------------------------------------
    */

    internal static void deleteNamespace( Namespace namespace_Renamed )
    {
      Namespace ns = namespace_Renamed;
      Interp interp = ns.interp;
      Namespace globalNs = getGlobalNamespace( interp );

      // If the namespace is on the call frame stack, it is marked as "dying"
      // (NS_DYING is OR'd into its flags): the namespace can't be looked up
      // by name but its commands and variables are still usable by those
      // active call frames. When all active call frames referring to the
      // namespace have been popped from the Tcl stack, popCallFrame will
      // call this procedure again to delete everything in the namespace.
      // If no nsName objects refer to the namespace (i.e., if its refCount 
      // is zero), its commands and variables are deleted and the storage for
      // its namespace structure is freed. Otherwise, if its refCount is
      // nonzero, the namespace's commands and variables are deleted but the
      // structure isn't freed. Instead, NS_DEAD is OR'd into the structure's
      // flags to allow the namespace resolution code to recognize that the
      // namespace is "deleted".

      if ( ns.activationCount > 0 )
      {
        ns.flags |= NS_DYING;
        if ( ns.parent != null )
        {
          ns.parent.childTable.Remove( ns.name );
        }
        ns.parent = null;
      }
      else
      {
        // Delete the namespace and everything in it. If this is the global
        // namespace, then clear it but don't free its storage unless the
        // interpreter is being torn down.

        teardownNamespace( ns );

        if ( ( ns != globalNs ) || ( ( interp.flags & Parser.DELETED ) != 0 ) )
        {
          // If this is the global namespace, then it may have residual
          // "errorInfo" and "errorCode" variables for errors that
          // occurred while it was being torn down.  Try to clear the
          // variable list one last time.

          Var.deleteVars( ns.interp, ns.varTable );

          ns.childTable.Clear();
          ns.cmdTable.Clear();

          // If the reference count is 0, then discard the namespace.
          // Otherwise, mark it as "dead" so that it can't be used.

          if ( ns.refCount == 0 )
          {
            free( ns );
          }
          else
          {
            ns.flags |= NS_DEAD;
          }
        }
      }
    }


    /*
    *----------------------------------------------------------------------
    *
    * TclTeardownNamespace -> teardownNamespace
    *
    *	Used internally to dismantle and unlink a namespace when it is
    *	deleted. Divorces the namespace from its parent, and deletes all
    *	commands, variables, and child namespaces.
    *
    *	This is kept separate from Tcl_DeleteNamespace so that the global
    *	namespace can be handled specially. Global variables like
    *	"errorInfo" and "errorCode" need to remain intact while other
    *	namespaces and commands are torn down, in case any errors occur.
    *
    * Results:
    *	None.
    *
    * Side effects:
    *	Removes this namespace from its parent's child namespace hashtable.
    *	Deletes all commands, variables and namespaces in this namespace.
    *	If this is the global namespace, the "errorInfo" and "errorCode"
    *	variables are left alone and deleted later.
    *
    *----------------------------------------------------------------------
    */

    internal static void teardownNamespace( Namespace ns )
    {
      Interp interp = ns.interp;
      IEnumerator search;
      Namespace globalNs = getGlobalNamespace( interp );
      int i;

      // Start by destroying the namespace's variable table,
      // since variables might trigger traces.

      if ( ns == globalNs )
      {
        // This is the global namespace, so be careful to preserve the
        // "errorInfo" and "errorCode" variables. These might be needed
        // later on if errors occur while deleting commands. We are careful
        // to destroy and recreate the "errorInfo" and "errorCode"
        // variables, in case they had any traces on them.

        string errorInfoStr, errorCodeStr;

        try
        {

          errorInfoStr = interp.getVar( "errorInfo", TCL.VarFlag.GLOBAL_ONLY ).ToString();
        }
        catch ( TclException e )
        {
          errorInfoStr = null;
        }

        try
        {

          errorCodeStr = interp.getVar( "errorCode", TCL.VarFlag.GLOBAL_ONLY ).ToString();
        }
        catch ( TclException e )
        {
          errorCodeStr = null;
        }

        Var.deleteVars( interp, ns.varTable );

        if ( (System.Object)errorInfoStr != null )
        {
          try
          {
            interp.setVar( "errorInfo", errorInfoStr, TCL.VarFlag.GLOBAL_ONLY );
          }
          catch ( TclException e )
          {
            // ignore an exception while setting this var
          }
        }
        if ( (System.Object)errorCodeStr != null )
        {
          try
          {
            interp.setVar( "errorCode", errorCodeStr, TCL.VarFlag.GLOBAL_ONLY );
          }
          catch ( TclException e )
          {
            // ignore an exception while setting this var
          }
        }
      }
      else
      {
        // Variable table should be cleared.
        Var.deleteVars( interp, ns.varTable );
      }

      // Remove the namespace from its parent's child hashtable.

      if ( ns.parent != null )
      {
        ns.parent.childTable.Remove( ns.name );
      }
      ns.parent = null;

      // Delete all the child namespaces.
      //
      // BE CAREFUL: When each child is deleted, it will divorce
      //    itself from its parent. You can't traverse a hash table
      //    properly if its elements are being deleted. We use only
      //    the Tcl_FirstHashEntry function to be safe.

      foreach ( Namespace childNs in new ArrayList( ns.childTable.Values ) )
      {
        deleteNamespace( childNs );
      }

      // Delete all commands in this namespace. Be careful when traversing the
      // hash table: when each command is deleted, it removes itself from the
      // command table.

      // FIXME : double check that using an enumeration for a hashtable
      // that changes is ok in Java! Also call deleteCommand... correctly!
      foreach ( WrappedCommand cmd in new ArrayList( ns.cmdTable.Values ) )
      {
        interp.deleteCommandFromToken( cmd );
      }

      ns.cmdTable.Clear();

      // Free the namespace's export pattern array.

      if ( ns.exportArray != null )
      {
        ns.exportArray = null;
        ns.numExportPatterns = 0;
        ns.maxExportPatterns = 0;
      }

      // Callback invoked when namespace is deleted

      if ( ns.deleteProc != null )
      {
        ns.deleteProc.delete();
      }
      ns.deleteProc = null;

      // Reset the namespace's id field to ensure that this namespace won't
      // be interpreted as valid by, e.g., the cache validation code for
      // cached command references in Tcl_GetCommandFromObj.

      ns.nsId = 0;
    }


    /*
    *----------------------------------------------------------------------
    *
    * NamespaceFree -> free
    *
    *	Called after a namespace has been deleted, when its
    *	reference count reaches 0.  Frees the data structure
    *	representing the namespace.
    *
    * Results:
    *	None.
    *
    * Side effects:
    *	None.
    *
    *----------------------------------------------------------------------
    */

    internal static void free( Namespace ns )
    {
      // Most of the namespace's contents are freed when the namespace is
      // deleted by Tcl_DeleteNamespace. All that remains is to free its names
      // (for error messages), and the structure itself.

      ns.name = null;
      ns.fullName = null;
    }

    /*
    *----------------------------------------------------------------------
    *
    * Tcl_Export -> exportList
    *
    *	Makes all the commands matching a pattern available to later be
    *	imported from the namespace specified by namespace (or the
    *	current namespace if namespace is null). The specified pattern is
    *	appended onto the namespace's export pattern list, which is
    *	optionally cleared beforehand.
    *
    * Results:
    *  Returns if successful, raises TclException if something goes wrong.
    *
    * Side effects:
    *	Appends the export pattern onto the namespace's export list.
    *	Optionally reset the namespace's export pattern list.
    *
    *----------------------------------------------------------------------
    */

    internal static void exportList( Interp interp, Namespace namespace_Renamed, string pattern, bool resetListFirst )
    {
      int INIT_EXPORT_PATTERNS = 5;
      Namespace ns, exportNs;
      Namespace currNs = getCurrentNamespace( interp );
      string simplePattern, patternCpy;
      int neededElems, len, i;

      // If the specified namespace is null, use the current namespace.

      if ( namespace_Renamed == null )
      {
        ns = currNs;
      }
      else
      {
        ns = namespace_Renamed;
      }

      // If resetListFirst is true (nonzero), clear the namespace's export
      // pattern list.

      if ( resetListFirst )
      {
        if ( ns.exportArray != null )
        {
          for ( i = 0; i < ns.numExportPatterns; i++ )
          {
            ns.exportArray[i] = null;
          }
          ns.exportArray = null;
          ns.numExportPatterns = 0;
          ns.maxExportPatterns = 0;
        }
      }

      // Check that the pattern doesn't have namespace qualifiers.

      // Java does not support passing an address so we pass
      // an array of size 1 and then assign arr[0] to the value
      Namespace[] exportNsArr = new Namespace[1];
      Namespace[] dummyArr = new Namespace[1];
      string[] simplePatternArr = new string[1];

      getNamespaceForQualName( interp, pattern, ns, TCL.VarFlag.LEAVE_ERR_MSG, exportNsArr, dummyArr, dummyArr, simplePatternArr );

      // get the values out of the arrays

      exportNs = exportNsArr[0];
      simplePattern = simplePatternArr[0];

      if ( ( exportNs != ns ) || ( pattern.CompareTo( simplePattern ) != 0 ) )
      {
        throw new TclException( interp, "invalid export pattern \"" + pattern + "\": pattern can't specify a namespace" );
      }

      // Make sure there is room in the namespace's pattern array for the
      // new pattern.

      neededElems = ns.numExportPatterns + 1;
      if ( ns.exportArray == null )
      {
        ns.exportArray = new string[INIT_EXPORT_PATTERNS];
        ns.numExportPatterns = 0;
        ns.maxExportPatterns = INIT_EXPORT_PATTERNS;
      }
      else if ( neededElems > ns.maxExportPatterns )
      {
        int numNewElems = 2 * ns.maxExportPatterns;
        string[] newArray = new string[numNewElems];
        Array.Copy( (System.Array)ns.exportArray, 0, (System.Array)newArray, 0, ns.numExportPatterns );
        ns.exportArray = newArray;
        ns.maxExportPatterns = numNewElems;
      }

      // Add the pattern to the namespace's array of export patterns.

      ns.exportArray[ns.numExportPatterns] = pattern;
      ns.numExportPatterns++;
      return;
    }


    /*
    *----------------------------------------------------------------------
    *
    * Tcl_AppendExportList -> appendExportList
    *
    *	Appends onto the argument object the list of export patterns for the
    *	specified namespace.
    *
    * Results:
    *	The method will return when successful; in this case the object
    *	referenced by obj has each export pattern appended to it. If an
    *	error occurs, an exception and the interpreter's result
    *	holds an error message.
    *
    * Side effects:
    *	If necessary, the object referenced by obj is converted into
    *	a list object.
    *
    *----------------------------------------------------------------------
    */

    internal static void appendExportList( Interp interp, Namespace namespace_Renamed, TclObject obj )
    {
      Namespace ns;
      int i;

      // If the specified namespace is null, use the current namespace.

      if ( namespace_Renamed == null )
      {
        ns = getCurrentNamespace( interp );
      }
      else
      {
        ns = namespace_Renamed;
      }

      // Append the export pattern list onto objPtr.

      for ( i = 0; i < ns.numExportPatterns; i++ )
      {
        TclList.append( interp, obj, TclString.newInstance( ns.exportArray[i] ) );
      }
      return;
    }


    /*
    *----------------------------------------------------------------------
    *
    * Tcl_Import -> importList
    *
    *	Imports all of the commands matching a pattern into the namespace
    *	specified by namespace (or the current namespace if namespace
    *	is null). This is done by creating a new command (the "imported
    *	command") that points to the real command in its original namespace.
    *
    *      If matching commands are on the autoload path but haven't been
    *	loaded yet, this command forces them to be loaded, then creates
    *	the links to them.
    *
    * Results:
    *  Returns if successful, raises TclException if something goes wrong.
    *
    * Side effects:
    *	Creates new commands in the importing namespace. These indirect
    *	calls back to the real command and are deleted if the real commands
    *	are deleted.
    *
    *----------------------------------------------------------------------
    */

    internal static void importList( Interp interp, Namespace namespace_Renamed, string pattern, bool allowOverwrite )
    {
      Namespace ns, importNs;
      Namespace currNs = getCurrentNamespace( interp );
      string simplePattern, cmdName;
      IEnumerator search;
      WrappedCommand cmd, realCmd;
      ImportRef ref_Renamed;
      WrappedCommand autoCmd, importedCmd;
      ImportedCmdData data;
      bool wasExported;
      int i, result;

      // If the specified namespace is null, use the current namespace.

      if ( namespace_Renamed == null )
      {
        ns = currNs;
      }
      else
      {
        ns = namespace_Renamed;
      }

      // First, invoke the "auto_import" command with the pattern
      // being imported.  This command is part of the Tcl library.
      // It looks for imported commands in autoloaded libraries and
      // loads them in.  That way, they will be found when we try
      // to create links below.

      autoCmd = findCommand( interp, "auto_import", null, TCL.VarFlag.GLOBAL_ONLY );

      if ( autoCmd != null )
      {
        TclObject[] objv = new TclObject[2];

        objv[0] = TclString.newInstance( "auto_import" );
        objv[0].preserve();
        objv[1] = TclString.newInstance( pattern );
        objv[1].preserve();

        cmd = autoCmd;
        try
        {
          // Invoke the command with the arguments
          cmd.cmd.cmdProc( interp, objv );
        }
        finally
        {
          objv[0].release();
          objv[1].release();
        }

        interp.resetResult();
      }

      // From the pattern, find the namespace from which we are importing
      // and get the simple pattern (no namespace qualifiers or ::'s) at
      // the end.

      if ( pattern.Length == 0 )
      {
        throw new TclException( interp, "empty import pattern" );
      }

      // Java does not support passing an address so we pass
      // an array of size 1 and then assign arr[0] to the value
      Namespace[] importNsArr = new Namespace[1];
      Namespace[] dummyArr = new Namespace[1];
      string[] simplePatternArr = new string[1];

      getNamespaceForQualName( interp, pattern, ns, TCL.VarFlag.LEAVE_ERR_MSG, importNsArr, dummyArr, dummyArr, simplePatternArr );

      importNs = importNsArr[0];
      simplePattern = simplePatternArr[0];

      if ( importNs == null )
      {
        throw new TclException( interp, "unknown namespace in import pattern \"" + pattern + "\"" );
      }
      if ( importNs == ns )
      {
        if ( (System.Object)pattern == (System.Object)simplePattern )
        {
          throw new TclException( interp, "no namespace specified in import pattern \"" + pattern + "\"" );
        }
        else
        {
          throw new TclException( interp, "import pattern \"" + pattern + "\" tries to import from namespace \"" + importNs.name + "\" into itself" );
        }
      }

      // Scan through the command table in the source namespace and look for
      // exported commands that match the string pattern. Create an "imported
      // command" in the current namespace for each imported command; these
      // commands redirect their invocations to the "real" command.


      for ( search = importNs.cmdTable.Keys.GetEnumerator(); search.MoveNext(); )
      {

        cmdName = ( (string)search.Current );
        if ( Util.stringMatch( cmdName, simplePattern ) )
        {
          // The command cmdName in the source namespace matches the
          // pattern. Check whether it was exported. If it wasn't,
          // we ignore it.

          wasExported = false;
          for ( i = 0; i < importNs.numExportPatterns; i++ )
          {
            if ( Util.stringMatch( cmdName, importNs.exportArray[i] ) )
            {
              wasExported = true;
              break;
            }
          }
          if ( !wasExported )
          {
            continue;
          }

          // Unless there is a name clash, create an imported command
          // in the current namespace that refers to cmdPtr.

          if ( ( ns.cmdTable[cmdName] == null ) || allowOverwrite )
          {
            // Create the imported command and its client data.
            // To create the new command in the current namespace, 
            // generate a fully qualified name for it.

            StringBuilder ds;

            ds = new StringBuilder();
            ds.Append( ns.fullName );
            if ( ns != interp.globalNs )
            {
              ds.Append( "::" );
            }
            ds.Append( cmdName );

            // Check whether creating the new imported command in the
            // current namespace would create a cycle of imported->real
            // command references that also would destroy an existing
            // "real" command already in the current namespace.

            cmd = (WrappedCommand)importNs.cmdTable[cmdName];

            if ( cmd.cmd is ImportedCmdData )
            {
              // This is actually an imported command, find
              // the real command it references
              realCmd = getOriginalCommand( cmd );
              if ( ( realCmd != null ) && ( realCmd.ns == currNs ) && ( currNs.cmdTable[cmdName] != null ) )
              {
                throw new TclException( interp, "import pattern \"" + pattern + "\" would create a loop containing command \"" + ds.ToString() + "\"" );
              }
            }

            data = new ImportedCmdData();

            // Create the imported command inside the interp
            interp.createCommand( ds.ToString(), data );

            // Lookup in the namespace for the new WrappedCommand
            importedCmd = findCommand( interp, ds.ToString(), ns, ( TCL.VarFlag.NAMESPACE_ONLY | TCL.VarFlag.LEAVE_ERR_MSG ) );

            data.realCmd = cmd;
            data.self = importedCmd;

            // Create an ImportRef structure describing this new import
            // command and add it to the import ref list in the "real"
            // command.

            ref_Renamed = new ImportRef();
            ref_Renamed.importedCmd = importedCmd;
            ref_Renamed.next = cmd.importRef;
            cmd.importRef = ref_Renamed;
          }
          else
          {
            throw new TclException( interp, "can't import command \"" + cmdName + "\": already exists" );
          }
        }
      }
      return;
    }

    /*
    *----------------------------------------------------------------------
    *
    * Tcl_ForgetImport -> forgetImport
    *
    *	Deletes previously imported commands. Given a pattern that may
    *	include the name of an exporting namespace, this procedure first
    *	finds all matching exported commands. It then looks in the namespace
    *	specified by namespace for any corresponding previously imported
    *	commands, which it deletes. If namespace is null, commands are
    *	deleted from the current namespace.
    *
    * Results:
    *  Returns if successful, raises TclException if something goes wrong.
    *
    * Side effects:
    *	May delete commands. 
    *
    *----------------------------------------------------------------------
    */

    internal static void forgetImport( Interp interp, Namespace namespace_Renamed, string pattern )
    {
      Namespace ns, importNs, actualCtx;
      string simplePattern, cmdName;
      IEnumerator search;
      WrappedCommand cmd;

      // If the specified namespace is null, use the current namespace.

      if ( namespace_Renamed == null )
      {
        ns = getCurrentNamespace( interp );
      }
      else
      {
        ns = namespace_Renamed;
      }

      // From the pattern, find the namespace from which we are importing
      // and get the simple pattern (no namespace qualifiers or ::'s) at
      // the end.

      // Java does not support passing an address so we pass
      // an array of size 1 and then assign arr[0] to the value
      Namespace[] importNsArr = new Namespace[1];
      Namespace[] dummyArr = new Namespace[1];
      Namespace[] actualCtxArr = new Namespace[1];
      string[] simplePatternArr = new string[1];

      getNamespaceForQualName( interp, pattern, ns, TCL.VarFlag.LEAVE_ERR_MSG, importNsArr, dummyArr, actualCtxArr, simplePatternArr );

      // get the values out of the arrays
      importNs = importNsArr[0];
      actualCtx = actualCtxArr[0];
      simplePattern = simplePatternArr[0];

      // FIXME : the above call passes TCL.VarFlag.LEAVE_ERR_MSG, but
      // it seems like this will be a problem when exception is raised!
      if ( importNs == null )
      {
        throw new TclException( interp, "unknown namespace in namespace forget pattern \"" + pattern + "\"" );
      }

      // Scan through the command table in the source namespace and look for
      // exported commands that match the string pattern. If the current
      // namespace has an imported command that refers to one of those real
      // commands, delete it.


      for ( search = importNs.cmdTable.Keys.GetEnumerator(); search.MoveNext(); )
      {

        cmdName = ( (string)search.Current );
        if ( Util.stringMatch( cmdName, simplePattern ) )
        {
          cmd = (WrappedCommand)ns.cmdTable[cmdName];
          if ( cmd != null )
          {
            // cmd of same name in current namespace
            if ( cmd.cmd is ImportedCmdData )
            {
              interp.deleteCommandFromToken( cmd );
            }
          }
        }
      }
      return;
    }


    /*
    *----------------------------------------------------------------------
    *
    * TclGetOriginalCommand -> getOriginalCommand
    *
    *	An imported command is created in a namespace when a "real" command
    *	is imported from another namespace. If the specified command is an
    *	imported command, this procedure returns the original command it
    *	refers to.
    *
    * Results:
    *	If the command was imported into a sequence of namespaces a, b,...,n
    *	where each successive namespace just imports the command from the
    *	previous namespace, this procedure returns the Tcl_Command token in
    *	the first namespace, a. Otherwise, if the specified command is not
    *	an imported command, the procedure returns null.
    *
    * Side effects:
    *	None.
    *
    *----------------------------------------------------------------------
    */

    internal static WrappedCommand getOriginalCommand( WrappedCommand command )
    {
      WrappedCommand cmd = command;
      ImportedCmdData data;

      if ( !( cmd.cmd is ImportedCmdData ) )
      {
        return null;
      }

      while ( cmd.cmd is ImportedCmdData )
      {
        data = (ImportedCmdData)cmd.cmd;
        cmd = data.realCmd;
      }
      return cmd;
    }


    /*
    *----------------------------------------------------------------------
    *
    * InvokeImportedCmd -> invokeImportedCmd
    *
    *	Invoked by Tcl whenever the user calls an imported command that
    *	was created by Tcl_Import. Finds the "real" command (in another
    *	namespace), and passes control to it.
    *
    * Results:
    *	Returns if successful, raises TclException if something goes wrong.
    *
    * Side effects:
    *	Returns a result in the interpreter's result object. If anything
    *	goes wrong, the result object is set to an error message.
    *
    *----------------------------------------------------------------------
    */

    internal static void invokeImportedCmd( Interp interp, ImportedCmdData data, TclObject[] objv )
    {
      WrappedCommand realCmd = data.realCmd;
      realCmd.cmd.cmdProc( interp, objv );
    }


    /*
    *----------------------------------------------------------------------
    *
    * DeleteImportedCmd -> deleteImportedCmd
    *
    *	Invoked by Tcl whenever an imported command is deleted. The "real"
    *	command keeps a list of all the imported commands that refer to it,
    *	so those imported commands can be deleted when the real command is
    *	deleted. This procedure removes the imported command reference from
    *	the real command's list, and frees up the memory associated with
    *	the imported command.
    *
    * Results:
    *	None.
    *
    * Side effects:
    *	Removes the imported command from the real command's import list.
    *
    *----------------------------------------------------------------------
    */

    internal static void deleteImportedCmd( ImportedCmdData data )
    // The data object for this imported command
    {
      WrappedCommand realCmd = data.realCmd;
      WrappedCommand self = data.self;
      ImportRef ref_Renamed, prev;

      prev = null;
      for ( ref_Renamed = realCmd.importRef; ref_Renamed != null; ref_Renamed = ref_Renamed.next )
      {
        if ( ref_Renamed.importedCmd == self )
        {
          // Remove ref from real command's list of imported commands
          // that refer to it.

          if ( prev == null )
          {
            // ref is first in list
            realCmd.importRef = ref_Renamed.next;
          }
          else
          {
            prev.next = ref_Renamed.next;
          }
          ref_Renamed = null;
          data = null;
          return;
        }
        prev = ref_Renamed;
      }

      throw new TclRuntimeError( "DeleteImportedCmd: did not find cmd in real cmd's list of import references" );
    }

    /*
    *----------------------------------------------------------------------
    *
    * TclGetNamespaceForQualName -> getNamespaceForQualName
    *
    *	Given a qualified name specifying a command, variable, or namespace,
    *	and a namespace in which to resolve the name, this procedure returns
    *	a pointer to the namespace that contains the item. A qualified name
    *	consists of the "simple" name of an item qualified by the names of
    *	an arbitrary number of containing namespace separated by "::"s. If
    *	the qualified name starts with "::", it is interpreted absolutely
    *	from the global namespace. Otherwise, it is interpreted relative to
    *	the namespace specified by cxtNsPtr if it is non-null. If cxtNsPtr
    *	is null, the name is interpreted relative to the current namespace.
    *
    *	A relative name like "foo::bar::x" can be found starting in either
    *	the current namespace or in the global namespace. So each search
    *	usually follows two tracks, and two possible namespaces are
    *	returned. If the procedure sets either nsPtrPtr[0] or altNsPtrPtr[0] to
    *	null, then that path failed.
    *
    *	If "flags" contains TCL.VarFlag.GLOBAL_ONLY, the relative qualified name is
    *	sought only in the global :: namespace. The alternate search
    *	(also) starting from the global namespace is ignored and
    *	altNsPtrPtr[0] is set null. 
    *
    *	If "flags" contains TCL.VarFlag.NAMESPACE_ONLY, the relative qualified
    *	name is sought only in the namespace specified by cxtNsPtr. The
    *	alternate search starting from the global namespace is ignored and
    *	altNsPtrPtr[0] is set null. If both TCL.VarFlag.GLOBAL_ONLY and
    *	TCL.VarFlag.NAMESPACE_ONLY are specified, TCL.VarFlag.GLOBAL_ONLY is ignored and
    *	the search starts from the namespace specified by cxtNsPtr.
    *
    *	If "flags" contains TCL.VarFlag.CREATE_NS_IF_UNKNOWN, all namespace
    *	components of the qualified name that cannot be found are
    *	automatically created within their specified parent. This makes sure
    *	that functions like Tcl_CreateCommand always succeed. There is no
    *	alternate search path, so altNsPtrPtr[0] is set null.
    *
    *	If "flags" contains TCL.VarFlag.FIND_ONLY_NS, the qualified name is treated as a
    *	reference to a namespace, and the entire qualified name is
    *	followed. If the name is relative, the namespace is looked up only
    *	in the current namespace. A pointer to the namespace is stored in
    *	nsPtrPtr[0] and null is stored in simpleNamePtr[0]. Otherwise, if
    *	TCL.VarFlag.FIND_ONLY_NS is not specified, only the leading components are
    *	treated as namespace names, and a pointer to the simple name of the
    *	final component is stored in simpleNamePtr[0].
    *
    * Results:
    *	It sets nsPtrPtr[0] and altNsPtrPtr[0] to point to the two possible
    *	namespaces which represent the last (containing) namespace in the
    *	qualified name. If the procedure sets either nsPtrPtr[0] or altNsPtrPtr[0]
    *	to null, then the search along that path failed.  The procedure also
    *	stores a pointer to the simple name of the final component in
    *	simpleNamePtr[0]. If the qualified name is "::" or was treated as a
    *	namespace reference (TCL.VarFlag.FIND_ONLY_NS), the procedure stores a pointer
    *	to the namespace in nsPtrPtr[0], null in altNsPtrPtr[0], and sets
    *	simpleNamePtr[0] to an empty string.
    *
    *	If there is an error, this procedure returns TCL_ERROR. If "flags"
    *	contains TCL_LEAVE_ERR_MSG, an error message is returned in the
    *	interpreter's result object. Otherwise, the interpreter's result
    *	object is left unchanged.
    *
    *	actualCxtPtrPtr[0] is set to the actual context namespace. It is
    *	set to the input context namespace pointer in cxtNsPtr. If cxtNsPtr
    *	is null, it is set to the current namespace context.
    *
    * Side effects:
    *	If "flags" contains TCL.VarFlag.CREATE_NS_IF_UNKNOWN, new namespaces may be
    *	created.
    *
    *----------------------------------------------------------------------
    */

    internal static void getNamespaceForQualName( Interp interp, string qualName, Namespace cxtNsPtr, TCL.VarFlag flags, Namespace[] nsPtrPtr, Namespace[] altNsPtrPtr, Namespace[] actualCxtPtrPtr, string[] simpleNamePtr )
    {


      // FIXME : remove extra method call checks when we are sure this works!

      if ( true )
      {
        // check invariants
        if ( ( nsPtrPtr == null ) || ( nsPtrPtr.Length != 1 ) )
        {

          throw new System.SystemException( "nsPtrPtr " + nsPtrPtr );
        }
        if ( ( altNsPtrPtr == null ) || ( altNsPtrPtr.Length != 1 ) )
        {

          throw new System.SystemException( "altNsPtrPtr " + altNsPtrPtr );
        }
        if ( ( actualCxtPtrPtr == null ) || ( actualCxtPtrPtr.Length != 1 ) )
        {

          throw new System.SystemException( "actualCxtPtrPtr " + actualCxtPtrPtr );
        }
        if ( ( simpleNamePtr == null ) || ( simpleNamePtr.Length != 1 ) )
        {

          throw new System.SystemException( "simpleNamePtr " + simpleNamePtr );
        }
      }




      Namespace ns = cxtNsPtr;
      Namespace altNs;
      Namespace globalNs = getGlobalNamespace( interp );
      Namespace entryNs;
      string start, end;
      string nsName;
      int len;
      int start_ind, end_ind, name_len;

      // Determine the context namespace ns in which to start the primary
      // search. If TCL.VarFlag.NAMESPACE_ONLY or TCL.VarFlag.FIND_ONLY_NS was specified, search
      // from the current namespace. If the qualName name starts with a "::"
      // or TCL.VarFlag.GLOBAL_ONLY was specified, search from the global
      // namespace. Otherwise, use the given namespace given in cxtNsPtr, or
      // if that is null, use the current namespace context. Note that we
      // always treat two or more adjacent ":"s as a namespace separator.

      if ( ( flags & ( TCL.VarFlag.NAMESPACE_ONLY | TCL.VarFlag.FIND_ONLY_NS ) ) != 0 )
      {
        ns = getCurrentNamespace( interp );
      }
      else if ( ( flags & TCL.VarFlag.GLOBAL_ONLY ) != 0 )
      {
        ns = globalNs;
      }
      else if ( ns == null )
      {
        if ( interp.varFrame != null )
        {
          ns = interp.varFrame.ns;
        }
        else
        {
          ns = interp.globalNs;
        }
      }



      start_ind = 0;
      name_len = qualName.Length;

      if ( ( name_len >= 2 ) && ( qualName[0] == ':' ) && ( qualName[1] == ':' ) )
      {
        start_ind = 2; // skip over the initial ::

        while ( ( start_ind < name_len ) && ( qualName[start_ind] == ':' ) )
        {
          start_ind++; // skip over a subsequent :
        }

        ns = globalNs;
        if ( start_ind >= name_len )
        {
          // qualName is just two or more ":"s
          nsPtrPtr[0] = globalNs;
          altNsPtrPtr[0] = null;
          actualCxtPtrPtr[0] = globalNs;
          simpleNamePtr[0] = ""; // points to empty string
          return;
        }
      }
      actualCxtPtrPtr[0] = ns;


      // Start an alternate search path starting with the global namespace.
      // However, if the starting context is the global namespace, or if the
      // flag is set to search only the namespace cxtNs, ignore the
      // alternate search path.


      altNs = globalNs;
      if ( ( ns == globalNs ) || ( ( flags & ( TCL.VarFlag.NAMESPACE_ONLY | TCL.VarFlag.FIND_ONLY_NS ) ) != 0 ) )
      {
        altNs = null;
      }


      // Loop to resolve each namespace qualifier in qualName.	

      end_ind = start_ind;

      while ( start_ind < name_len )
      {
        // Find the next namespace qualifier (i.e., a name ending in "::")
        // or the end of the qualified name  (i.e., a name ending in "\0").
     …

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