table of contents
| Handles(3tclx) | Handles(3tclx) |
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 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 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 table is set to one.
Parameters:
o entrySize - The size of an entry, in bytes.
o initEntries - Initial size of the table, in entries.
Returns:
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 amount - The amount to alter the use count by.
Returns:
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:
Tcl_HandleAlloc¶
Allocate an entry and associate a handle with it.
Parameters:
o handlePtr - Buffer to return handle in. It must be big enough to hold the name.
Returns:
Tcl_HandleXlate¶
Translate a handle to a entry pointer.
Parameters:
o headerPtr - A pointer to the table header.
o handle - The handle assigned to the entry.
Returns:
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 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.
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 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 entryPtr - Entry to free.
| Tcl |