crtchannel.3

linux系统下的音频通信

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'\" Copyright (c) 1996-1997 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
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'\" SCCS: @(#) CrtChannel.3 1.29 97/06/20 13:37:45
.so man.macros
.TH Tcl_CreateChannel 3 8.0 Tcl "Tcl Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Tcl_CreateChannel, Tcl_GetChannelInstanceData, Tcl_GetChannelType, Tcl_GetChannelName, Tcl_GetChannelHandle, Tcl_GetChannelMode, Tcl_GetChannelBufferSize, Tcl_SetDefaultTranslation, Tcl_SetChannelBufferSize, Tcl_NotifyChannel, Tcl_BadChannelOption \- procedures for creating and manipulating channels
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
Tcl_Channel
\fBTcl_CreateChannel\fR(\fItypePtr, channelName, instanceData, mask\fR)
.sp
ClientData
\fBTcl_GetChannelInstanceData\fR(\fIchannel\fR)
.sp
Tcl_ChannelType *
\fBTcl_GetChannelType\fR(\fIchannel\fR)
.sp
char *
\fBTcl_GetChannelName\fR(\fIchannel\fR)
.VS
.sp
int
\fBTcl_GetChannelHandle\fR(\fIchannel, direction, handlePtr\fR)
.VE
.sp
int
\fBTcl_GetChannelFlags\fR(\fIchannel\fR)
.sp
\fBTcl_SetDefaultTranslation\fR(\fIchannel, transMode\fR)
.sp
int
\fBTcl_GetChannelBufferSize\fR(\fIchannel\fR)
.sp
\fBTcl_SetChannelBufferSize\fR(\fIchannel, size\fR)
.sp
.VS
\fBTcl_NotifyChannel\fR(\fIchannel, mask\fR)
.sp
int
\fBTcl_BadChannelOption\fR(\fIinterp, optionName, optionList\fR)
.VE
.sp
.SH ARGUMENTS
.AS Tcl_EolTranslation *channelName in
.AP Tcl_ChannelType *typePtr in
Points to a structure containing the addresses of procedures that
can be called to perform I/O and other functions on the channel.
.AP char *channelName in
The name of this channel, such as \fBfile3\fR; must not be in use
by any other channel. Can be NULL, in which case the channel is
created without a name.
.AP ClientData instanceData in
Arbitrary one-word value to be associated with this channel.  This
value is passed to procedures in \fItypePtr\fR when they are invoked.
.AP int mask in
OR-ed combination of \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR to indicate
whether a channel is readable and writable.
.AP Tcl_Channel channel in
The channel to operate on.
.VS
.AP int direction in
\fBTCL_READABLE\fR means the input handle is wanted; \fBTCL_WRITABLE\fR
means the output handle is wanted.
.AP ClientData *handlePtr out
Points to the location where the desired OS-specific handle should be
stored.
.VE
.AP Tcl_EolTranslation transMode in
The translation mode; one of the constants \fBTCL_TRANSLATE_AUTO\fR,
\fBTCL_TRANSLATE_CR\fR, \fBTCL_TRANSLATE_LF\fR and \fBTCL_TRANSLATE_CRLF\fR.
.AP int size in
The size, in bytes, of buffers to allocate in this channel.
.VS
.AP int mask in
An OR-ed combination of \fBTCL_READABLE\fR, \fBTCL_WRITABLE\fR
and \fBTCL_EXCEPTION\fR that indicates events that have occurred on
this channel.
.AP Tcl_Interp *interp in
Current interpreter. (can be NULL)
.AP char *optionName in
Name of the invalid option.
.AP char *optionList in
Specific options list (space separated words, without "-") 
to append to the standard generic options list.
Can be NULL for generic options error message only.
.VE

.BE

.SH DESCRIPTION
.PP
Tcl uses a two-layered channel architecture. It provides a generic upper
layer to enable C and Tcl programs to perform input and output using the
same APIs for a variety of files, devices, sockets etc. The generic C APIs
are described in the manual entry for \fBTcl_OpenFileChannel\fR.
.PP
The lower layer provides type-specific channel drivers for each type
of device supported on each platform.  This manual entry describes the
C APIs used to communicate between the generic layer and the
type-specific channel drivers.  It also explains how new types of
channels can be added by providing new channel drivers.
.PP
Channel drivers consist of a number of components: First, each channel
driver provides a \fBTcl_ChannelType\fR structure containing pointers to
functions implementing the various operations used by the generic layer to
communicate with the channel driver. The \fBTcl_ChannelType\fR structure
and the functions referenced by it are described in the section
TCL_CHANNELTYPE, below.
.PP
Second, channel drivers usually provide a Tcl command to create
instances of that type of channel. For example, the Tcl \fBopen\fR
command creates channels that use the file and command channel
drivers, and the Tcl \fBsocket\fR command creates channels that use
TCP sockets for network communication.
.PP
Third, a channel driver optionally provides a C function to open
channel instances of that type. For example, \fBTcl_OpenFileChannel\fR
opens a channel that uses the file channel driver, and
\fBTcl_OpenTcpClient\fR opens a channel that uses the TCP network
protocol.  These creation functions typically use
\fBTcl_CreateChannel\fR internally to open the channel.
.PP
To add a new type of channel you must implement a C API or a Tcl command
that opens a channel by invoking \fBTcl_CreateChannel\fR.
When your driver calls \fBTcl_CreateChannel\fR it passes in
a \fBTcl_ChannelType\fR structure describing the driver's I/O
procedures.
The generic layer will then invoke the functions referenced in that
structure to perform operations on the channel.
.PP
\fBTcl_CreateChannel\fR opens a new channel and associates the supplied
\fItypePtr\fR and \fIinstanceData\fR with it. The channel is opened in the
mode indicated by \fImask\fR.
For a discussion of channel drivers, their operations and the
\fBTcl_ChannelType\fR structure, see the section TCL_CHANNELTYPE, below.
.PP
\fBTcl_GetChannelInstanceData\fR returns the instance data associated with
the channel in \fIchannel\fR. This is the same as the \fIinstanceData\fR
argument in the call to \fBTcl_CreateChannel\fR that created this channel.
.PP
\fBTcl_GetChannelType\fR returns a pointer to the \fBTcl_ChannelType\fR
structure used by the channel in the \fIchannel\fR argument. This is
the same as the \fItypePtr\fR argument in the call to
\fBTcl_CreateChannel\fR that created this channel.
.PP
\fBTcl_GetChannelName\fR returns a string containing the name associated
with the channel, or NULL if the \fIchannelName\fR argument to
\fBTcl_CreateChannel\fR was NULL.
.PP
.VS
\fBTcl_GetChannelHandle\fR places the OS-specific device handle
associated with \fIchannel\fR for the given \fIdirection\fR in the
location specified by \fIhandlePtr\fR and returns \fBTCL_OK\fR.  If
the channel does not have a device handle for the specified direction,
then \fBTCL_ERROR\fR is returned instead.  Different channel drivers
will return different types of handle.  Refer to the manual entries
for each driver to determine what type of handle is returned.
.VE
.PP
\fBTcl_GetChannelMode\fR returns an OR-ed combination of \fBTCL_READABLE\fR
and \fBTCL_WRITABLE\fR, indicating whether the channel is open for input
and output.
.PP
\fBTcl_SetDefaultTranslation\fR sets the default end of line translation
mode. This mode will be installed as the translation mode for the channel
if an attempt is made to output on the channel while it is still in
\fBTCL_TRANSLATE_AUTO\fR mode. For a description of end of line translation
modes, see the manual entry for \fBfconfigure\fR.
.PP
\fBTcl_GetChannelBufferSize\fR returns the size, in bytes, of buffers
allocated to store input or output in \fIchan\fR. If the value was not set
by a previous call to \fBTcl_SetChannelBufferSize\fR, described below, then
the default value of 4096 is returned.
.PP
\fBTcl_SetChannelBufferSize\fR sets the size, in bytes, of buffers that
will be allocated in subsequent operations on the channel to store input or
output. The \fIsize\fR argument should be between ten and one million,
allowing buffers of ten bytes to one million bytes. If \fIsize\fR is
outside this range, \fBTcl_SetChannelBufferSize\fR sets the buffer size to
4096.
.PP
.VS
\fBTcl_NotifyChannel\fR is called by a channel driver to indicate to
the generic layer that the events specified by \fImask\fR have
occurred on the channel.  Channel drivers are responsible for invoking
this function whenever the channel handlers need to be called for the
channel.  See \fBWATCHPROC\fR below for more details.
.VE
.PP
.VS
\fBTcl_BadChannelOption\fR is called from driver specific set or get option
procs to generate a complete error message.
.VE

.SH TCL_CHANNELTYPE
.PP
A channel driver provides a \fBTcl_ChannelType\fR structure that contains
pointers to functions that implement the various operations on a channel;
these operations are invoked as needed by the generic layer. The
\fBTcl_ChannelType\fR structure contains the following fields:
.PP
.VS
.CS
typedef struct Tcl_ChannelType {
	char *\fItypeName\fR;
	Tcl_DriverBlockModeProc *\fIblockModeProc\fR;	
	Tcl_DriverCloseProc *\fIcloseProc\fR;
	Tcl_DriverInputProc *\fIinputProc\fR;
	Tcl_DriverOutputProc *\fIoutputProc\fR;
	Tcl_DriverSeekProc *\fIseekProc\fR;
	Tcl_DriverSetOptionProc *\fIsetOptionProc\fR;
	Tcl_DriverGetOptionProc *\fIgetOptionProc\fR;
	Tcl_DriverWatchProc *\fIwatchProc\fR;
	Tcl_DriverGetHandleProc *\fIgetHandleProc\fR;
} Tcl_ChannelType;
.CE
.VE
.PP
The driver must provide implementations for all functions except
\fIblockModeProc\fR, \fIseekProc\fR, \fIsetOptionProc\fR, and
\fIgetOptionProc\fR, which may be specified as NULL to indicate that the
channel does not support seeking.  Other functions that can not be
implemented for this type of device should return \fBEINVAL\fR when invoked
to indicate that they are not implemented.

.SH TYPENAME
.PP
The \fItypeName\fR field contains a null-terminated string that
identifies the type of the device implemented by this driver, e.g.
\fBfile\fR or \fBsocket\fR.

.SH BLOCKMODEPROC
.PP
The \fIblockModeProc\fR field contains the address of a function called by
the generic layer to set blocking and nonblocking mode on the device.
\fIBlockModeProc\fR should match the following prototype:
.PP
.CS
typedef int Tcl_DriverBlockModeProc(
	ClientData \fIinstanceData\fR,
	int \fImode\fR);
.CE
.PP
The \fIinstanceData\fR is the same as the value passed to
\fBTcl_CreateChannel\fR when this channel was created.  The \fImode\fR
argument is either \fBTCL_MODE_BLOCKING\fR or \fBTCL_MODE_NONBLOCKING\fR to
set the device into blocking or nonblocking mode. The function should
return zero if the operation was successful, or a nonzero POSIX error code
if the operation failed.
.PP
If the operation is successful, the function can modify the supplied
\fIinstanceData\fR to record that the channel entered blocking or
nonblocking mode and to implement the blocking or nonblocking behavior.
For some device types, the blocking and nonblocking behavior can be
implemented by the underlying operating system; for other device types, the
behavior must be emulated in the channel driver.

.SH CLOSEPROC
.PP
The \fIcloseProc\fR field contains the address of a function called by the
generic layer to clean up driver-related information when the channel is
closed. \fICloseProc\fR must match the following prototype:
.PP
.CS
typedef int Tcl_DriverCloseProc(
	ClientData \fIinstanceData\fR,
	Tcl_Interp *\fIinterp\fR);
.CE
.PP
The \fIinstanceData\fR argument is the same as the value provided to
\fBTcl_CreateChannel\fR when the channel was created. The function should
release any storage maintained by the channel driver for this channel, and
close the input and output devices encapsulated by this channel. All queued
output will have been flushed to the device before this function is called,
and no further driver operations will be invoked on this instance after
calling the \fIcloseProc\fR. If the close operation is successful, the
procedure should return zero; otherwise it should return a nonzero POSIX