| 1 | '\" |
| 2 | '\" Copyright (c) 1996 Sun Microsystems, Inc. |
| 3 | '\" |
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| 5 | '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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| 7 | '\" RCS: @(#) $Id: CrtChnlHdlr.3,v 1.2 1998/09/14 18:39:46 stanton Exp $ |
| 8 | '\" The definitions below are for supplemental macros used in Tcl/Tk |
| 9 | '\" manual entries. |
| 10 | '\" |
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| 38 | '\" of man pages. The first argument is ignored and used for recording |
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| 69 | '\" RCS: @(#) $Id: man.macros,v 1.4 2000/08/25 06:18:32 ericm Exp $ |
| 70 | '\" |
| 71 | '\" # Set up traps and other miscellaneous stuff for Tcl/Tk man pages. |
| 72 | .if t .wh -1.3i ^B |
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| 206 | .SH "STANDARD OPTIONS" |
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| 224 | Command-Line Name: \\fB\\$1\\fR |
| 225 | Database Name: \\fB\\$2\\fR |
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| 242 | \\$1\l'|0\(ul'\\$2 |
| 243 | .. |
| 244 | .TH Tcl_CreateChannelHandler 3 7.5 Tcl "Tcl Library Procedures" |
| 245 | .BS |
| 246 | '\" Note: do not modify the .SH NAME line immediately below! |
| 247 | .SH NAME |
| 248 | Tcl_CreateChannelHandler, Tcl_DeleteChannelHandler \- call a procedure when a channel becomes readable or writable |
| 249 | .SH SYNOPSIS |
| 250 | .nf |
| 251 | .nf |
| 252 | \fB#include <tcl.h>\fR |
| 253 | .sp |
| 254 | void |
| 255 | \fBTcl_CreateChannelHandler\fR(\fIchannel, mask, proc, clientData\fR) |
| 256 | .sp |
| 257 | void |
| 258 | \fBTcl_DeleteChannelHandler\fR(\fIchannel, proc, clientData\fR) |
| 259 | .sp |
| 260 | .SH ARGUMENTS |
| 261 | .AS Tcl_ChannelProc clientData |
| 262 | .AP Tcl_Channel channel in |
| 263 | Tcl channel such as returned by \fBTcl_CreateChannel\fR. |
| 264 | .AP int mask in |
| 265 | Conditions under which \fIproc\fR should be called: OR-ed combination of |
| 266 | \fBTCL_READABLE\fR, \fBTCL_WRITABLE\fR and \fBTCL_EXCEPTION\fR. Specify |
| 267 | a zero value to temporarily disable an existing handler. |
| 268 | .AP Tcl_FileProc *proc in |
| 269 | Procedure to invoke whenever the channel indicated by \fIchannel\fR meets |
| 270 | the conditions specified by \fImask\fR. |
| 271 | .AP ClientData clientData in |
| 272 | Arbitrary one-word value to pass to \fIproc\fR. |
| 273 | .BE |
| 274 | |
| 275 | .SH DESCRIPTION |
| 276 | .PP |
| 277 | \fBTcl_CreateChannelHandler\fR arranges for \fIproc\fR to be called in the |
| 278 | future whenever input or output becomes possible on the channel identified |
| 279 | by \fIchannel\fR, or whenever an exceptional condition exists for |
| 280 | \fIchannel\fR. The conditions of interest under which \fIproc\fR will be |
| 281 | invoked are specified by the \fImask\fR argument. |
| 282 | See the manual entry for \fBfileevent\fR for a precise description of |
| 283 | what it means for a channel to be readable or writable. |
| 284 | \fIProc\fR must conform to the following prototype: |
| 285 | .CS |
| 286 | typedef void Tcl_ChannelProc( |
| 287 | ClientData \fIclientData\fR, |
| 288 | int \fImask\fR); |
| 289 | .CE |
| 290 | .PP |
| 291 | The \fIclientData\fR argument is the same as the value passed to |
| 292 | \fBTcl_CreateChannelHandler\fR when the handler was created. Typically, |
| 293 | \fIclientData\fR points to a data structure containing application-specific |
| 294 | information about the channel. \fIMask\fR is an integer mask indicating |
| 295 | which of the requested conditions actually exists for the channel; it will |
| 296 | contain a subset of the bits from the \fImask\fR argument to |
| 297 | \fBTcl_CreateChannelHandler\fR when the handler was created. |
| 298 | .PP |
| 299 | Each channel handler is identified by a unique combination of \fIchannel\fR, |
| 300 | \fIproc\fR and \fIclientData\fR. |
| 301 | There may be many handlers for a given channel as long as they don't |
| 302 | have the same \fIchannel\fR, \fIproc\fR, and \fIclientData\fR. |
| 303 | If \fBTcl_CreateChannelHandler\fR is invoked when there is already a handler |
| 304 | for \fIchannel\fR, \fIproc\fR, and \fIclientData\fR, then no new |
| 305 | handler is created; instead, the \fImask\fR is changed for the |
| 306 | existing handler. |
| 307 | .PP |
| 308 | \fBTcl_DeleteChannelHandler\fR deletes a channel handler identified by |
| 309 | \fIchannel\fR, \fIproc\fR and \fIclientData\fR; if no such handler exists, |
| 310 | the call has no effect. |
| 311 | .PP |
| 312 | Channel handlers are invoked via the Tcl event mechanism, so they |
| 313 | are only useful in applications that are event-driven. |
| 314 | Note also that the conditions specified in the \fImask\fR argument |
| 315 | to \fIproc\fR may no longer exist when \fIproc\fR is invoked: for |
| 316 | example, if there are two handlers for \fBTCL_READABLE\fR on the same |
| 317 | channel, the first handler could consume all of the available input |
| 318 | so that the channel is no longer readable when the second handler |
| 319 | is invoked. |
| 320 | For this reason it may be useful to use nonblocking I/O on channels |
| 321 | for which there are event handlers. |
| 322 | |
| 323 | .SH "SEE ALSO" |
| 324 | Notifier(3), Tcl_CreateChannel(3), Tcl_OpenFileChannel(3), vwait(n). |
| 325 | |
| 326 | .SH KEYWORDS |
| 327 | blocking, callback, channel, events, handler, nonblocking. |