Tcl_HandleTblInit

Handles(TCL)                                                      Handles(TCL)



NAME
       Tcl_HandleAlloc,  Tcl_HandleFree,  Tcl_HandleTblInit,  Tcl_HandleTblRe-
       lease, 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
       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
       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 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
         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
       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)