openfilechnl.3

linux系统下的音频通信

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'\" Copyright (c) 1996-1997 Sun Microsystems, Inc.
'\"
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'\" SCCS: @(#) OpenFileChnl.3 1.40 97/09/29 11:22:49
.so man.macros
.TH Tcl_OpenFileChannel 3 8.0 Tcl "Tcl Library Procedures"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
Tcl_OpenFileChannel, Tcl_OpenCommandChannel, Tcl_MakeFileChannel, Tcl_GetChannel, Tcl_RegisterChannel, Tcl_UnregisterChannel, Tcl_Close, Tcl_Read, Tcl_Gets, Tcl_Write, Tcl_Flush, Tcl_Seek, Tcl_Tell, Tcl_Eof, Tcl_InputBlocked, Tcl_InputBuffered, Tcl_GetChannelOption, Tcl_SetChannelOption \- buffered I/O facilities using channels
.SH SYNOPSIS
.nf
\fB#include <tcl.h>\fR
.sp
typedef ... Tcl_Channel;
.sp
Tcl_Channel
\fBTcl_OpenFileChannel\fR(\fIinterp, fileName, mode, permissions\fR)
.sp
Tcl_Channel
\fBTcl_OpenCommandChannel\fR(\fIinterp, argc, argv, flags\fR)
.VS
.sp
Tcl_Channel
\fBTcl_MakeFileChannel\fR(\fIhandle, readOrWrite\fR)
.VE
.sp
Tcl_Channel
\fBTcl_GetChannel\fR(\fIinterp, channelName, modePtr\fR)
.sp
void
\fBTcl_RegisterChannel\fR(\fIinterp, channel\fR)
.sp
int
\fBTcl_UnregisterChannel\fR(\fIinterp, channel\fR)
.sp
int
\fBTcl_Close\fR(\fIinterp, channel\fR)
.sp
int
\fBTcl_Read\fR(\fIchannel, buf, toRead\fR)
.sp
int
\fBTcl_Gets\fR(\fIchannel, lineRead\fR)
.sp
int
\fBTcl_GetsObj\fR(\fIchannel, lineObjPtr\fR)
.sp
int
\fBTcl_Write\fR(\fIchannel, buf, toWrite\fR)
.sp
int
\fBTcl_Flush\fR(\fIchannel\fR)
.sp
int
\fBTcl_Seek\fR(\fIchannel, offset, seekMode\fR)
.sp
int
\fBTcl_Tell\fR(\fIchannel\fR)
.sp
int
\fBTcl_GetChannelOption\fR(\fIinterp, channel, optionName, optionValue\fR)
.sp
int
\fBTcl_SetChannelOption\fR(\fIinterp, channel, optionName, newValue\fR)
.sp
int
\fBTcl_Eof\fR(\fIchannel\fR)
.sp
int
\fBTcl_InputBlocked\fR(\fIchannel\fR)
.sp
int
\fBTcl_InputBuffered\fR(\fIchannel\fR)
.sp
.SH ARGUMENTS
.AS Tcl_ChannelType newClientProcPtr in
.AP Tcl_Interp *interp in
Used for error reporting and to look up a channel registered in it.
.AP char *fileName in
The name of a local or network file.
.AP char *mode in
Specifies how the file is to be accessed.  May have any of the
values allowed for the \fImode\fR argument to the Tcl
\fBopen\fR command.
For \fBTcl_OpenCommandChannel\fR, may be NULL.
.AP int permissions in
POSIX-style permission flags such as 0644.
If a new file is created, these permissions will be set on the
created file.
.AP int argc in
The number of elements in \fIargv\fR.
.AP char **argv in
Arguments for constructing a command pipeline.
These values have the same meaning as the non-switch arguments
to the Tcl \fBexec\fR command.
.AP int flags in
Specifies the disposition of the stdio handles in pipeline: OR-ed
combination of \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, \fBTCL_STDERR\fR,
and \fBTCL_ENFORCE_MODE\fR. If \fBTCL_STDIN\fR is set, stdin for
the first child in the pipe is the pipe channel, otherwise it is the same
as the standard input of the invoking process; likewise for
\fBTCL_STDOUT\fR and \fBTCL_STDERR\fR. If \fBTCL_ENFORCE_MODE\fR is not set,
then the pipe can redirect stdio handles to override the stdio handles for
which \fBTCL_STDIN\fR, \fBTCL_STDOUT\fR and \fBTCL_STDERR\fR have been set.
If it is set, then such redirections cause an error.
.VS
.AP ClientData handle in
Operating system specific handle for I/O to a file. For Unix this is a
file descriptor, for Windows it is a HANDLE.
.AP int readOrWrite in
OR-ed combination of \fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR to indicate
what operations are valid on \fIhandle\fR.
.VE
.AP int *modePtr out
Points at an integer variable that will receive an OR-ed combination of
\fBTCL_READABLE\fR and \fBTCL_WRITABLE\fR denoting whether the channel is
open for reading and writing.
.AP Tcl_Channel channel in
A Tcl channel for input or output.  Must have been the return value
from a procedure such as \fBTcl_OpenFileChannel\fR.
.AP char *buf in
An array of bytes in which to store channel input, or from which
to read channel output.
.AP int len in
The length of the input or output.
.AP int atEnd in
If nonzero, store the input at the end of the input queue, otherwise store
it at the head of the input queue.
.AP int toRead in
The number of bytes to read from the channel.
.AP Tcl_DString *lineRead in
A pointer to a Tcl dynamic string in which to store the line read from the
channel.  Must have been initialized by the caller.  The line read
will be appended to any data already in the dynamic string.
.AP Tcl_Obj *linePtrObj in
A pointer to a Tcl object in which to store the line read from the
channel.  The line read will be appended to the current value of the
object. 
.AP int toWrite in
The number of bytes to read from \fIbuf\fR and output to the channel.
.AP int offset in
How far to move the access point in the channel at which the next input or
output operation will be applied, measured in bytes from the position
given by \fIseekMode\fR.  May be either positive or negative.
.AP int seekMode in
Relative to which point to seek; used with \fIoffset\fR to calculate the new
access point for the channel. Legal values are \fBSEEK_SET\fR,
\fBSEEK_CUR\fR, and \fBSEEK_END\fR.
.AP char *optionName in
The name of an option applicable to this channel, such as \fB\-blocking\fR.
May have any of the values accepted by the \fBfconfigure\fR command.
.AP Tcl_DString *optionValue in
Where to store the value of an option or a list of all options and their
values. Must have been initialized by the caller.
.AP char *newValue in
New value for the option given by \fIoptionName\fR.
.BE

.SH DESCRIPTION
.PP
The Tcl channel mechanism provides a device-independent and
platform-independent mechanism for performing buffered input
and output operations on a variety of file, socket, and device
types.
The channel mechanism is extensible to new channel types, by
providing a low level channel driver for the new type; the channel driver
interface is described in the manual entry for \fBTcl_CreateChannel\fR. The
channel mechanism provides a buffering scheme modelled after
Unix's standard I/O, and it also allows for nonblocking I/O on
channels.
.PP
The procedures described in this manual entry comprise the C APIs of the
generic layer of the channel architecture. For a description of the channel
driver architecture and how to implement channel drivers for new types of
channels, see the manual entry for \fBTcl_CreateChannel\fR.

.SH TCL_OPENFILECHANNEL
.PP
\fBTcl_OpenFileChannel\fR opens a file specified by \fIfileName\fR and
returns a channel handle that can be used to perform input and output on
the file. This API is modelled after the \fBfopen\fR procedure of
the Unix standard I/O library.
The syntax and meaning of all arguments is similar to those
given in the Tcl \fBopen\fR command when opening a file.
If an error occurs while opening the channel, \fBTcl_OpenFileChannel\fR
returns NULL and records a POSIX error code that can be
retrieved with \fBTcl_GetErrno\fR.
In addition, if \fIinterp\fR is non-NULL, \fBTcl_OpenFileChannel\fR
leaves an error message in \fIinterp->result\fR after any error.
.PP
The newly created channel is not registered in the supplied interpreter; to
register it, use \fBTcl_RegisterChannel\fR, described below.
If one of the standard channels, \fBstdin, stdout\fR or \fBstderr\fR was
previously closed, the act of creating the new channel also assigns it as a
replacement for the standard channel.

.SH TCL_OPENCOMMANDCHANNEL
.PP
\fBTcl_OpenCommandChannel\fR provides a C-level interface to the
functions of the \fBexec\fR and \fBopen\fR commands.
It creates a sequence of subprocesses specified
by the \fIargv\fR and \fIargc\fR arguments and returns a channel that can
be used to communicate with these subprocesses.
The \fIflags\fR argument indicates what sort of communication will
exist with the command pipeline.
.PP
If the \fBTCL_STDIN\fR flag is set then the standard input for the
first subprocess will be tied to the channel: writing to the channel
will provide input to the subprocess.  If \fBTCL_STDIN\fR is not set,
then standard input for the first subprocess will be the same as this
application's standard input.  If \fBTCL_STDOUT\fR is set then
standard output from the last subprocess can be read from the channel;
otherwise it goes to this application's standard output.  If
\fBTCL_STDERR\fR is set, standard error output for all subprocesses is
returned to the channel and results in an error when the channel is
closed; otherwise it goes to this application's standard error.  If
\fBTCL_ENFORCE_MODE\fR is not set, then \fIargc\fR and \fIargv\fR can
redirect the stdio handles to override \fBTCL_STDIN\fR,
\fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR; if it is set, then it is an
error for argc and argv to override stdio channels for which
\fBTCL_STDIN\fR, \fBTCL_STDOUT\fR, and \fBTCL_STDERR\fR have been set.
.PP
If an error occurs while opening the channel, \fBTcl_OpenCommandChannel\fR
returns NULL and records a POSIX error code that can be retrieved with
\fBTcl_GetErrno\fR.
In addition, \fBTcl_OpenCommandChannel\fR leaves an error message in
\fIinterp->result\fR if \fIinterp\fR is not NULL.
.PP
The newly created channel is not registered in the supplied interpreter; to
register it, use \fBTcl_RegisterChannel\fR, described below.
If one of the standard channels, \fBstdin, stdout\fR or \fBstderr\fR was
previously closed, the act of creating the new channel also assigns it as a
replacement for the standard channel.

.SH TCL_MAKEFILECHANNEL
.PP
\fBTcl_MakeFileChannel\fR makes a \fBTcl_Channel\fR from an existing,
platform-specific, file handle.
The newly created channel is not registered in the supplied interpreter; to
register it, use \fBTcl_RegisterChannel\fR, described below.
If one of the standard channels, \fBstdin, stdout\fR or \fBstderr\fR was
previously closed, the act of creating the new channel also assigns it as a
replacement for the standard channel.

.SH TCL_GETCHANNEL
.PP