Tcl_CreateChannelHandler (3)
call a procedure when a channel becomes readable or writable
SYNOPSIS
#include <tcl.h>
void
Tcl_CreateChannelHandler(channel, mask, proc, clientData)
void
Tcl_DeleteChannelHandler(channel, proc, clientData)
ARGUMENTS
Tcl_ChannelProc clientData
Tcl_Channel channel in
Tcl channel such as returned by Tcl_CreateChannel.
int mask in
Conditions under which proc should be called: OR-ed combination of
TCL_READABLE, TCL_WRITABLE and TCL_EXCEPTION. Specify
a zero value to temporarily disable an existing handler.
Tcl_FileProc *proc in
Procedure to invoke whenever the channel indicated by channel meets
the conditions specified by mask.
ClientData clientData in
Arbitrary one-word value to pass to proc.
DESCRIPTION
Tcl_CreateChannelHandler arranges for proc to be called in the
future whenever input or output becomes possible on the channel identified
by channel, or whenever an exceptional condition exists for
channel. The conditions of interest under which proc will be
invoked are specified by the mask argument.
See the manual entry for fileevent for a precise description of
what it means for a channel to be readable or writable.
Proc must conform to the following prototype:
typedef void Tcl_ChannelProc(
ClientData clientData,
int mask);
The clientData argument is the same as the value passed to
Tcl_CreateChannelHandler when the handler was created. Typically,
clientData points to a data structure containing application-specific
information about the channel. Mask is an integer mask indicating
which of the requested conditions actually exists for the channel; it will
contain a subset of the bits from the mask argument to
Tcl_CreateChannelHandler when the handler was created.
Each channel handler is identified by a unique combination of channel,
proc and clientData.
There may be many handlers for a given channel as long as they don't
have the same channel, proc, and clientData.
If Tcl_CreateChannelHandler is invoked when there is already a handler
for channel, proc, and clientData, then no new
handler is created; instead, the mask is changed for the
existing handler.
Tcl_DeleteChannelHandler deletes a channel handler identified by
channel, proc and clientData; if no such handler exists,
the call has no effect.
Channel handlers are invoked via the Tcl event mechanism, so they
are only useful in applications that are event-driven.
Note also that the conditions specified in the mask argument
to proc may no longer exist when proc is invoked: for
example, if there are two handlers for TCL_READABLE on the same
channel, the first handler could consume all of the available input
so that the channel is no longer readable when the second handler
is invoked.
For this reason it may be useful to use nonblocking I/O on channels
for which there are event handlers.
SEE ALSO
KEYWORDS
blocking, callback, channel, events, handler, nonblocking.
'\"
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
'\" RCS: @(#) $Id: CrtCloseHdlr.3,v 1.2 1998/09/14 18:39:47 stanton Exp $
'\" The definitions below are for supplemental macros used in Tcl/Tk
'\" manual entries.
'\"
'\" .AP type name in/out ?indent?
'\" Start paragraph describing an argument to a library procedure.
'\" type is type of argument (int, etc.), in/out is either "in", "out",
'\" or "in/out" to describe whether procedure reads or modifies arg,
'\" and indent is equivalent to second arg of .IP (shouldn't ever be
'\" needed; use .AS below instead)
'\"
'\" .AS ?type? ?name?
'\" Give maximum sizes of arguments for setting tab stops. Type and
'\" name are examples of largest possible arguments that will be passed
'\" to .AP later. If args are omitted, default tab stops are used.
'\"
'\" .BS
'\" Start box enclosure. From here until next .BE, everything will be
'\" enclosed in one large box.
'\"
'\" .BE
'\" End of box enclosure.
'\"
'\" .CS
'\" Begin code excerpt.
'\"
'\" .CE
'\" End code excerpt.
'\"
'\" .VS ?version? ?br?
'\" Begin vertical sidebar, for use in marking newly-changed parts
'\" of man pages. The first argument is ignored and used for recording
'\" the version when the .VS was added, so that the sidebars can be
'\" found and removed when they reach a certain age. If another argument
'\" is present, then a line break is forced before starting the sidebar.
'\"
'\" .VE
'\" End of vertical sidebar.
'\"
'\" .DS
'\" Begin an indented unfilled display.
'\"
'\" .DE
'\" End of indented unfilled display.
'\"
'\" .SO
'\" Start of list of standard options for a Tk widget. The
'\" options follow on successive lines, in four columns separated
'\" by tabs.
'\"
'\" .SE
'\" End of list of standard options for a Tk widget.
'\"
'\" .OP cmdName dbName dbClass
'\" Start of description of a specific option. cmdName gives the
'\" option's name as specified in the class command, dbName gives
'\" the option's name in the option database, and dbClass gives
'\" the option's class in the option database.
'\"
'\" .UL arg1 arg2
'\" Print arg1 underlined, then print arg2 normally.
'\"
'\" RCS: @(#) $Id: man.macros,v 1.2 1998/09/14 18:39:54 stanton Exp $
'\"
'\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages.
t .wh -1.3i ^B
^l \n(.l
b
'\" # Start an argument description
AP
!"\\$4"" .TP \\$4
\{\
!"\\$2"" .TP \\n()Cu
.TP 15
|
