[OpenSPARC-T2-SAM] / sam-t2 / devtools / v9 / man / man3 / Tcl_StackChannel.3

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.AS Tcl_Interp Tcl_CreateInterp in/out
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.TH Tcl_StackChannel 3 8.3 Tcl "Tcl Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Tcl_StackChannel, Tcl_UnstackChannel, Tcl_GetStackedChannel, Tcl_GetTopChannel \- stack an I/O channel on top of another, and undo it
.SH SYNOPSIS
.nf
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_Channel
\fBTcl_StackChannel\fR(\fIinterp, typePtr, clientData, mask, channel\fR)
.sp
int
\fBTcl_UnstackChannel\fR(\fIinterp, channel\fR)
.sp
Tcl_Channel
\fBTcl_GetStackedChannel\fR(\fIchannel\fR)
.sp
Tcl_Channel
\fBTcl_GetTopChannel\fR(\fIchannel\fR)
.sp
.SH ARGUMENTS
.AS Tcl_ChannelType
.AP Tcl_Interp *interp in
Interpreter for error reporting.
.AP Tcl_ChannelType *typePtr in
The new channel I/O procedures to use for \fIchannel\fP.
.AP ClientData clientData in
Arbitrary one-word value to pass to channel I/O procedures.
.AP int mask in
Conditions under which \fIchannel\fR will be used: OR-ed combination of
\fBTCL_READABLE\fR, \fBTCL_WRITABLE\fR and \fBTCL_EXCEPTION\fR.
This can be a subset of the operations currently allowed on \fIchannel\fP.
.AP Tcl_Channel channel in
An existing Tcl channel such as returned by \fBTcl_CreateChannel\fR.
.BE

.SH DESCRIPTION
.PP
These functions are for use by extensions that add processing layers to Tcl
I/O channels.  Examples include compression and encryption modules.  These
functions transparently stack and unstack a new channel on top of an
existing one.  Any number of channels can be stacked together.
.PP
The implementation of the Tcl channel code was rewritten in 8.3.2 to
correct some problems with the previous implementation with regard to
stacked channels.  Anyone using stacked channels or creating stacked
channel drivers should update to the new \fBTCL_CHANNEL_VERSION_2\fR
\fBTcl_ChannelType\fR structure.  See \fBTcl_CreateChannel\fR for details.
.PP
\fBTcl_StackChannel\fR stacks a new \fIchannel\fP on an existing channel
with the same name that was registered for \fIchannel\fP by
\fBTcl_RegisterChannel\fP.
.PP
\fBTcl_StackChannel\fR works by creating a new channel structure and
placing itself on top of the channel stack.  EOL translation, encoding and
buffering options are shared between all channels in the stack.  The hidden
channel does no buffering, newline translations, or character set encoding.
Instead, the buffering, newline translations, and encoding functions all
remain at the top of the channel stack.  A pointer to the new top channel
structure is returned.  If an error occurs when stacking the channel, NULL
is returned instead.
.PP
The \fImask\fP parameter specifies the operations that are allowed on the
new channel.  These can be a subset of the operations allowed on the
original channel.  For example, a read-write channel may become read-only
after the \fBTcl_StackChannel\fR call.
.PP
Closing a channel closes the channels stacked below it.  The close of
stacked channels is executed in a way that allows buffered data to be
properly flushed.
.PP
\fBTcl_UnstackChannel\fP reverses the process.  The old channel is
associated with the channel name, and the processing module added by
\fBTcl_StackChannel\fR is destroyed.  If there is no old channel, then
\fBTcl_UnstackChannel\fP is equivalent to \fBTcl_Close\fP.  If an error
occurs unstacking the channel, \fBTCL_ERROR\fR is returned, otherwise
\fBTCL_OK\fR is returned.
.PP
\fBTcl_GetTopChannel\fR returns the top channel in the stack of
channels the supplied channel is part of.
.PP
\fBTcl_GetStackedChannel\fR returns the channel in the stack of
channels which is just below the supplied channel.

.SH "SEE ALSO"
Notifier(3), Tcl_CreateChannel(3), Tcl_OpenFileChannel(3), vwait(n).

.SH KEYWORDS
channel, compression
Commit	Line	Data
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	5	'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
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	8	'\" The definitions below are for supplemental macros used in Tcl/Tk
	9	'\" manual entries.
	10	'\"
	11	'\" .AP type name in/out ?indent?
	12	'\" Start paragraph describing an argument to a library procedure.
	13	'\" type is type of argument (int, etc.), in/out is either "in", "out",
	14	'\" or "in/out" to describe whether procedure reads or modifies arg,
	15	'\" and indent is equivalent to second arg of .IP (shouldn't ever be
	16	'\" needed; use .AS below instead)
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	18	'\" .AS ?type? ?name?
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	64	'\" the option's class in the option database.
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72	.if t .wh -1.3i ^B
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243	..
244	.TH Tcl_StackChannel 3 8.3 Tcl "Tcl Library Procedures"
245	.BS
246	'\" Note: do not modify the .SH NAME line immediately below!
247	.SH NAME
248	Tcl_StackChannel, Tcl_UnstackChannel, Tcl_GetStackedChannel, Tcl_GetTopChannel \- stack an I/O channel on top of another, and undo it
249	.SH SYNOPSIS
250	.nf
251	.nf
252	\fB#include <tcl.h>\fR
253	.sp
254	Tcl_Channel
255	\fBTcl_StackChannel\fR(\fIinterp, typePtr, clientData, mask, channel\fR)
256	.sp
257	int
258	\fBTcl_UnstackChannel\fR(\fIinterp, channel\fR)
259	.sp
260	Tcl_Channel
261	\fBTcl_GetStackedChannel\fR(\fIchannel\fR)
262	.sp
263	Tcl_Channel
264	\fBTcl_GetTopChannel\fR(\fIchannel\fR)
265	.sp
266	.SH ARGUMENTS
267	.AS Tcl_ChannelType
268	.AP Tcl_Interp *interp in
269	Interpreter for error reporting.
270	.AP Tcl_ChannelType *typePtr in
271	The new channel I/O procedures to use for \fIchannel\fP.
272	.AP ClientData clientData in
273	Arbitrary one-word value to pass to channel I/O procedures.
274	.AP int mask in
275	Conditions under which \fIchannel\fR will be used: OR-ed combination of
276	\fBTCL_READABLE\fR, \fBTCL_WRITABLE\fR and \fBTCL_EXCEPTION\fR.
277	This can be a subset of the operations currently allowed on \fIchannel\fP.
278	.AP Tcl_Channel channel in
279	An existing Tcl channel such as returned by \fBTcl_CreateChannel\fR.
280	.BE
281
282	.SH DESCRIPTION
283	.PP
284	These functions are for use by extensions that add processing layers to Tcl
285	I/O channels. Examples include compression and encryption modules. These
286	functions transparently stack and unstack a new channel on top of an
287	existing one. Any number of channels can be stacked together.
288	.PP
289	The implementation of the Tcl channel code was rewritten in 8.3.2 to
290	correct some problems with the previous implementation with regard to
291	stacked channels. Anyone using stacked channels or creating stacked
292	channel drivers should update to the new \fBTCL_CHANNEL_VERSION_2\fR
293	\fBTcl_ChannelType\fR structure. See \fBTcl_CreateChannel\fR for details.
294	.PP
295	\fBTcl_StackChannel\fR stacks a new \fIchannel\fP on an existing channel
296	with the same name that was registered for \fIchannel\fP by
297	\fBTcl_RegisterChannel\fP.
298	.PP
299	\fBTcl_StackChannel\fR works by creating a new channel structure and
300	placing itself on top of the channel stack. EOL translation, encoding and
301	buffering options are shared between all channels in the stack. The hidden
302	channel does no buffering, newline translations, or character set encoding.
303	Instead, the buffering, newline translations, and encoding functions all
304	remain at the top of the channel stack. A pointer to the new top channel
305	structure is returned. If an error occurs when stacking the channel, NULL
306	is returned instead.
307	.PP
308	The \fImask\fP parameter specifies the operations that are allowed on the
309	new channel. These can be a subset of the operations allowed on the
310	original channel. For example, a read-write channel may become read-only
311	after the \fBTcl_StackChannel\fR call.
312	.PP
313	Closing a channel closes the channels stacked below it. The close of
314	stacked channels is executed in a way that allows buffered data to be
315	properly flushed.
316	.PP
317	\fBTcl_UnstackChannel\fP reverses the process. The old channel is
318	associated with the channel name, and the processing module added by
319	\fBTcl_StackChannel\fR is destroyed. If there is no old channel, then
320	\fBTcl_UnstackChannel\fP is equivalent to \fBTcl_Close\fP. If an error
321	occurs unstacking the channel, \fBTCL_ERROR\fR is returned, otherwise
322	\fBTCL_OK\fR is returned.
323	.PP
324	\fBTcl_GetTopChannel\fR returns the top channel in the stack of
325	channels the supplied channel is part of.
326	.PP
327	\fBTcl_GetStackedChannel\fR returns the channel in the stack of
328	channels which is just below the supplied channel.
329
330	.SH "SEE ALSO"
331	Notifier(3), Tcl_CreateChannel(3), Tcl_OpenFileChannel(3), vwait(n).
332
333	.SH KEYWORDS
334	channel, compression