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Handles(TCL)							    Handles(TCL)

NAME
     Tcl_HandleAlloc,  Tcl_HandleFree,	Tcl_HandleTblInit, Tcl_HandleTblRelease,
     Tcl_HandleTblUseCount, Tcl_HandleWalk, Tcl_HandleXlate  -	Dynamic,  handle
     addressable tables.

SYNOPSIS
     #include <tclExtend.h>

     void_pt
     Tcl_HandleTblInit (const char *handleBase,
			int	    entrySize,
			int	    initEntries);

     int
     Tcl_HandleTblUseCount (void_pt  headerPtr,
			    int      amount);

     void
     Tcl_HandleTblRelease (void_pt headerPtr);

     void_pt
     Tcl_HandleAlloc (void_pt	headerPtr,
		      char     *handlePtr);

     void_pt
     Tcl_HandleXlate (Tcl_Interp *interp,
		      void_pt	  headerPtr,
		      const char *handle);

     void_pt
     Tcl_HandleWalk (void_pt   headerPtr,
		     int      *walkKeyPtr);

     void
     Tcl_WalkKeyToHandle (void_pt   headerPtr,
			  int	    walkKey,
			  char	   *handlePtr);

     void
     Tcl_HandleFree (void_pt headerPtr,
		     void_pt entryPtr);

DESCRIPTION
     The  Tcl handle facility provides a way to manage table entries that may be
     referenced by a textual handle from Tcl code.  This is provided for  appli-
     cations that need to create data structures in one command, return a refer-
     ence  (i.e. pointer) to that particular data structure and then access that
     data structure in other commands. An example application is file handles.

     A handle consists of a base name, which is some  unique,  meaningful  name,
     such  as  `file'  and  a  numeric	value  appended  to  the base name (e.g.
     `file3').	The handle facility is designed to provide a standard  mechanism
     for  building  Tcl commands that allocate and access table entries based on
     an entry index.  The tables are expanded when needed, consequently pointers
     to entries should not be kept, as they will become invalid when  the  table
     is  expanded.   If  the table entries are large or pointers must be kept to
     the entries, then the the entries should be allocated separately and point-
     ers kept in the handle table.  A use count is kept on the table.  This  use
     count  is intended to determine when a table shared by multiple commands is
     to be release.

   Tcl_HandleTblInit
     Create and initialize a Tcl dynamic handle table.	The use count on the ta-
     ble is set to one.

     Parameters:
       o handleBase - The base name of the handle, the handle will  be	returned
       in the form "baseNN", where NN is the table entry number.
       o entrySize - The size of an entry, in bytes.
       o initEntries - Initial size of the table, in entries.

     Returns:
       A pointer to the table header.

   Tcl_HandleTblUseCount
     Alter the handle table use count by the specified amount, which can be pos-
     itive or negative.  Amount may be zero to retrieve the use count.

     Parameters:
       o headerPtr - Pointer to the table header.
       o amount - The amount to alter the use count by.

     Returns:
       The resulting use count.

   Tcl_HandleTblRelease
     Decrement	the  use count on a Tcl dynamic handle table.  If the count goes
     to zero or negative, then release the table.

     Parameters:
       o headerPtr - Pointer to the table header.

   Tcl_HandleAlloc
     Allocate an entry and associate a handle with it.

     Parameters:
       o headerPtr - A pointer to the table header.
       o handlePtr - Buffer to return handle in. It must be big enough	to  hold
       the name.

     Returns:
       A pointer to the allocated entry (user part).

   Tcl_HandleXlate
     Translate a handle to a entry pointer.

     Parameters:
       o interp - A error message may be returned in result.
       o headerPtr - A pointer to the table header.

       o handle - The handle assigned to the entry.

     Returns:
       A pointer to the entry, or NULL if an error occurred.

   Tcl_HandleWalk
     Walk  through  and  find  every allocated entry in a table.  Entries may be
     deallocated during a walk, but should not be allocated.

     Parameters:
       o headerPtr - A pointer to the table header.
       o walkKeyPtr - Pointer to a variable to use to keep track of the place in
       the table.  The variable should be initialized to  -1  before  the  first
       call.
     Returns:
       A pointer to the next allocated entry, or NULL if there are not more.

   Tcl_WalkKeyToHandle
     Convert  a  walk key, as returned from a call to Tcl_HandleWalk into a han-
     dle.  The Tcl_HandleWalk must have succeeded.

     Parameters:
       o headerPtr - A pointer to the table header.
       o walkKey - The walk key.
       o handlePtr - Buffer to return handle in. It must be big enough	to  hold
       the name.

   Tcl_HandleFree
     Frees a handle table entry.

     Parameters:
       o headerPtr - A pointer to the table header.
       o entryPtr - Entry to free.

Tcl								    Handles(TCL)

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