/TCL/src/commands/LappendCmd.cs

/*
* LappendCmd.java
*
* Copyright (c) 1997 Cornell University.
* Copyright (c) 1997 Sun Microsystems, Inc.
* Copyright (c) 1998-1999 by Scriptics Corporation.
* Copyright (c) 1999 Mo DeJong.
*
* 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: LappendCmd.java,v 1.3 2003/01/09 02:15:39 mdejong Exp $
*
*/
using System;
namespace tcl.lang
{

  /// <summary> This class implements the built-in "lappend" command in Tcl.</summary>
  class LappendCmd : Command
  {
    /// <summary> 
    /// Tcl_LappendObjCmd -> LappendCmd.cmdProc
    /// 
    /// This procedure is invoked to process the "lappend" Tcl command.
    /// See the user documentation for details on what it does.
    /// </summary>

    public TCL.CompletionCode cmdProc( Interp interp, TclObject[] objv )
    {
      TclObject varValue, newValue = null;
      int i;//int numElems, i, j;
      bool createdNewObj, createVar;

      if ( objv.Length < 2 )
      {
        throw new TclNumArgsException( interp, 1, objv, "varName ?value value ...?" );
      }
      if ( objv.Length == 2 )
      {
        try
        {
          newValue = interp.getVar( objv[1], 0 );
        }
        catch ( TclException e )
        {
          // The variable doesn't exist yet. Just create it with an empty
          // initial value.
          varValue = TclList.newInstance();

          try
          {
            newValue = interp.setVar( objv[1], varValue, 0 );
          }
          finally
          {
            if ( newValue == null )
              varValue.release(); // free unneeded object
          }

          interp.resetResult();
          return TCL.CompletionCode.RETURN;
        }
      }
      else
      {
        // We have arguments to append. We used to call Tcl_SetVar2 to
        // append each argument one at a time to ensure that traces were run
        // for each append step. We now append the arguments all at once
        // because it's faster. Note that a read trace and a write trace for
        // the variable will now each only be called once. Also, if the
        // variable's old value is unshared we modify it directly, otherwise
        // we create a new copy to modify: this is "copy on write".

        createdNewObj = false;
        createVar = true;

        try
        {
          varValue = interp.getVar( objv[1], 0 );
        }
        catch ( TclException e )
        {
          // We couldn't read the old value: either the var doesn't yet
          // exist or it's an array element. If it's new, we will try to
          // create it with Tcl_ObjSetVar2 below.

          // FIXME : not sure we even need this parse for anything!
          // If we do not need to parse could we at least speed it up a bit

          string varName;
          int nameBytes;


          varName = objv[1].ToString();
          nameBytes = varName.Length; // Number of Unicode chars in string

          for ( i = 0; i < nameBytes; i++ )
          {
            if ( varName[i] == '(' )
            {
              i = nameBytes - 1;
              if ( varName[i] == ')' )
              {
                // last char is ')' => array ref
                createVar = false;
              }
              break;
            }
          }
          varValue = TclList.newInstance();
          createdNewObj = true;
        }

        // We only take this branch when the catch branch was not run
        if ( createdNewObj == false && varValue.Shared )
        {
          varValue = varValue.duplicate();
          createdNewObj = true;
        }

        // Insert the new elements at the end of the list.

        for ( i = 2; i < objv.Length; i++ )
            TclList.append( interp, varValue, objv[i] );

        // No need to call varValue.invalidateStringRep() since it
        // is called during the TclList.append operation.

        // Now store the list object back into the variable. If there is an
        // error setting the new value, decrement its ref count if it
        // was new and we didn't create the variable.

        try
        {

          newValue = interp.setVar( objv[1].ToString(), varValue, 0 );
        }
        catch ( TclException e )
        {
          if ( createdNewObj && !createVar )
          {
            varValue.release(); // free unneeded obj
          }
          throw;
        }
      }

      // Set the interpreter's object result to refer to the variable's value
      // object.

      interp.setResult( newValue );
      return TCL.CompletionCode.RETURN;
    }
  }
}