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Handles(TCL)							  Handles(TCL)

NAME
       Tcl_HandleAlloc,	 Tcl_HandleFree,  Tcl_HandleTblInit,  Tcl_HandleTblRe-
       lease, Tcl_HandleTblUseCount,  Tcl_HandleWalk,  Tcl_HandleXlate	-  Dy-
       namic, 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
       applications that need to create	data structures	in one command,	return
       a reference (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 en-
       tries based on an entry index.  The tables are  expanded	 when  needed,
       consequently  pointers  to entries should not be	kept, as they will be-
       come 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 pointers kept	in the	handle	table.
       A use count is kept on the table.  This use count is intended to	deter-
       mine 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
       table is	set to one.

       Parameters:
	 o  handleBase	-  The base name of the	handle,	the handle will	be re-
	 turned	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
       positive	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
       handle.	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)

NAME | SYNOPSIS | DESCRIPTION

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