crtchannel.3

linux系统下的音频通信

error code. In addition, if an error occurs and \fIinterp\fR is not NULL,
the procedure should store an error message in \fIinterp->result\fR.

.SH INPUTPROC
.PP
The \fIinputProc\fR field contains the address of a function called by the
generic layer to read data from the file or device and store it in an
internal buffer. \fIInputProc\fR must match the following prototype:
.PP
.CS
typedef int Tcl_DriverInputProc(
	ClientData \fIinstanceData\fR,
	char *\fIbuf\fR,
	int \fIbufSize\fR,
	int *\fIerrorCodePtr\fR);
.CE
.PP
\fIInstanceData\fR is the same as the value passed to
\fBTcl_CreateChannel\fR when the channel was created.  The \fIbuf\fR
argument points to an array of bytes in which to store input from the
device, and the \fIbufSize\fR argument indicates how many bytes are
available at \fIbuf\fR.
.PP
The \fIerrorCodePtr\fR argument points to an integer variable provided by
the generic layer. If an error occurs, the function should set the variable
to a POSIX error code that identifies the error that occurred.
.PP
The function should read data from the input device encapsulated by the
channel and store it at \fIbuf\fR.  On success, the function should return
a nonnegative integer indicating how many bytes were read from the input
device and stored at \fIbuf\fR. On error, the function should return -1. If
an error occurs after some data has been read from the device, that data is
lost.
.PP
If \fIinputProc\fR can determine that the input device has some data
available but less than requested by the \fIbufSize\fR argument, the
function should only attempt to read as much data as is available and
return without blocking. If the input device has no data available
whatsoever and the channel is in nonblocking mode, the function should
return an \fBEAGAIN\fR error. If the input device has no data available
whatsoever and the channel is in blocking mode, the function should block
for the shortest possible time until at least one byte of data can be read
from the device; then, it should return as much data as it can read without
blocking.

.SH OUTPUTPROC
.PP
The \fIoutputProc\fR field contains the address of a function called by the
generic layer to transfer data from an internal buffer to the output device.
\fIOutputProc\fR must match the following prototype:
.PP
.CS
typedef int Tcl_DriverOutputProc(
	ClientData \fIinstanceData\fR,
	char *\fIbuf\fR,
	int \fItoWrite\fR,
	int *\fIerrorCodePtr\fR);
.CE
.PP
\fIInstanceData\fR is the same as the value passed to
\fBTcl_CreateChannel\fR when the channel was created. The \fIbuf\fR
argument contains an array of bytes to be written to the device, and the
\fItoWrite\fR argument indicates how many bytes are to be written from the
\fIbuf\fR argument.
.PP
The \fIerrorCodePtr\fR argument points to an integer variable provided by
the generic layer. If an error occurs, the function should set this
variable to a POSIX error code that identifies the error.
.PP
The function should write the data at \fIbuf\fR to the output device
encapsulated by the channel. On success, the function should return a
nonnegative integer indicating how many bytes were written to the output
device.  The return value is normally the same as \fItoWrite\fR, but may be
less in some cases such as if the output operation is interrupted by a
signal. If an error occurs the function should return -1.  In case of
error, some data may have been written to the device.
.PP
If the channel is nonblocking and the output device is unable to absorb any
data whatsoever, the function should return -1 with an \fBEAGAIN\fR error
without writing any data.

.SH SEEKPROC
.PP
The \fIseekProc\fR field contains the address of a function called by the
generic layer to move the access point at which subsequent input or output
operations will be applied. \fISeekProc\fR must match the following
prototype:
.PP
.CS
typedef int Tcl_DriverSeekProc(
	ClientData \fIinstanceData\fR,
	long \fIoffset\fR,
	int \fIseekMode\fR,
	int *\fIerrorCodePtr\fR);
.CE
.PP
The \fIinstanceData\fR argument is the same as the value given to
\fBTcl_CreateChannel\fR when this channel was created.  \fIOffset\fR and
\fIseekMode\fR have the same meaning as for the \fBTcl_SeekChannel\fR
procedure (described in the manual entry for \fBTcl_OpenFileChannel\fR).
.PP
The \fIerrorCodePtr\fR argument points to an integer variable provided by
the generic layer for returning \fBerrno\fR values from the function.  The
function should set this variable to a POSIX error code if an error occurs.
The function should store an \fBEINVAL\fR error code if the channel type
does not implement seeking.
.PP
The return value is the new access point or -1 in case of error. If an
error occurred, the function should not move the access point.

.SH SETOPTIONPROC
.PP
The \fIsetOptionProc\fR field contains the address of a function called by
the generic layer to set a channel type specific option on a channel.
\fIsetOptionProc\fR must match the following prototype:
.PP
.CS
typedef int Tcl_DriverSetOptionProc(
	ClientData \fIinstanceData\fR,
	Tcl_Interp *\fIinterp\fR,
	char *\fIoptionName\fR,
	char *\fIoptionValue\fR);
.CE
.PP
\fIoptionName\fR is the name of an option to set, and \fIoptionValue\fR is
the new value for that option, as a string. The \fIinstanceData\fR is the
same as the value given to \fBTcl_CreateChannel\fR when this channel was
created. The function should do whatever channel type specific action is
required to implement the new value of the option.
.PP
Some options are handled by the generic code and this function is never
called to set them, e.g. \fB-blockmode\fR. Other options are specific to
each channel type and the \fIsetOptionProc\fR procedure of the channel
driver will get called to implement them. The \fIsetOptionProc\fR field can
be NULL, which indicates that this channel type supports no type specific
options. 
.PP
If the option value is successfully modified to the new value, the function
returns \fBTCL_OK\fR.
.VS
It should call \fBTcl_BadChannelOption\fR which itself returns
\fBTCL_ERROR\fR if the \fIoptionName\fR is
unrecognized. 
.VE
If \fIoptionValue\fR specifies a value for the option that
is not supported or if a system call error occurs,
the function should leave an error message in the
\fIresult\fR field of \fIinterp\fR if \fIinterp\fR is not NULL. The
function should also call \fBTcl_SetErrno\fR to store an appropriate POSIX
error code.

.SH GETOPTIONPROC
.PP
The \fIgetOptionProc\fR field contains the address of a function called by
the generic layer to get the value of a channel type specific option on a
channel. \fIgetOptionProc\fR must match the following prototype:
.PP
.CS
typedef int Tcl_DriverGetOptionProc(
	ClientData \fIinstanceData\fR,
.VS
	Tcl_Interp *\fIinterp\fR,
.VE
	char *\fIoptionName\fR,
	Tcl_DString *\fIdsPtr\fR);
.CE
.PP
\fIOptionName\fR is the name of an option supported by this type of
channel. If the option name is not NULL, the function stores its current
value, as a string, in the Tcl dynamic string \fIdsPtr\fR.
If \fIoptionName\fR is NULL, the function stores in \fIdsPtr\fR an
alternating list of all supported options and their current values.
On success, the function returns \fBTCL_OK\fR. 
.VS
It should call \fBTcl_BadChannelOption\fR which itself returns
\fBTCL_ERROR\fR if the \fIoptionName\fR is
unrecognized. If a system call error occurs,
the function should leave an error message in the
\fIresult\fR field of \fIinterp\fR if \fIinterp\fR is not NULL. The
function should also call \fBTcl_SetErrno\fR to store an appropriate POSIX
error code.
.VE
.PP
Some options are handled by the generic code and this function is never
called to retrieve their value, e.g. \fB-blockmode\fR. Other options are
specific to each channel type and the \fIgetOptionProc\fR procedure of the
channel driver will get called to implement them. The \fIgetOptionProc\fR
field can be NULL, which indicates that this channel type supports no type
specific options.

.SH WATCHPROC
.VS
.PP
The \fIwatchProc\fR field contains the address of a function called
by the generic layer to initialize the event notification mechanism to
notice events of interest on this channel.
\fIWatchProc\fR should match the following prototype:
.PP
.CS
typedef void Tcl_DriverWatchProc(
	ClientData \fIinstanceData\fR,
	int \fImask\fR);
.CE
.VE
.PP
The \fIinstanceData\fR is the same as the value passed to
\fBTcl_CreateChannel\fR when this channel was created. The \fImask\fR
argument is an OR-ed combination of \fBTCL_READABLE\fR, \fBTCL_WRITABLE\fR
and \fBTCL_EXCEPTION\fR; it indicates events the caller is interested in
noticing on this channel.
.PP
.VS
The function should initialize device type specific mechanisms to
notice when an event of interest is present on the channel.  When one
or more of the designated events occurs on the channel, the channel
driver is responsible for calling \fBTcl_NotifyChannel\fR to inform
the generic channel module.  The driver should take care not to starve
other channel drivers or sources of callbacks by invoking
Tcl_NotifyChannel too frequently.  Fairness can be insured by using
the Tcl event queue to allow the channel event to be scheduled in sequence
with other events.  See the description of \fBTcl_QueueEvent\fR for
details on how to queue an event.

.SH GETHANDLEPROC
.PP
The \fIgetHandleProc\fR field contains the address of a function called by
the generic layer to retrieve a device-specific handle from the channel.
\fIGetHandleProc\fR should match the following prototype:
.PP
.CS
typedef int Tcl_DriverGetHandleProc(
	ClientData \fIinstanceData\fR,
	int \fIdirection\fR,
	ClientData *\fIhandlePtr\fR);
.CE
.PP
\fIInstanceData is the same as the value passed to
\fBTcl_CreateChannel\fR when this channel was created. The \fIdirection\fR
argument is either \fBTCL_READABLE\fR to retrieve the handle used
for input, or \fBTCL_WRITABLE\fR to retrieve the handle used for
output.
.PP
If the channel implementation has device-specific handles, the
function should retrieve the appropriate handle associated with the
channel, according the \fIdirection\fR argument.  The handle should be
stored in the location referred to by \fIhandlePtr\fR, and
\fBTCL_OK\fR should be returned.  If the channel is not open for the
specified direction, or if the channel implementation does not use
device handles, the function should return \fBTCL_ERROR\fR.
.VE

.VS
.SH TCL_BADCHANNELOPTION
.PP
This procedure generates a "bad option" error message in an
(optional) interpreter.  It is used by channel drivers when 
a invalid Set/Get option is requested. Its purpose is to concatenate
the generic options list to the specific ones and factorize
the generic options error message string.
.PP
It always return \fBTCL_ERROR\fR
.PP
An error message is generated in interp's result object to
indicate that a command was invoked with the a bad option
The message has the form
.CS
    bad option "blah": should be one of 
    <...generic options...>+<...specific options...>
so you get for instance:
    bad option "-blah": should be one of -blocking,
    -buffering, -buffersize, -eofchar, -translation,
    -peername, or -sockname
when called with optionList="peername sockname"
.CE
"blah" is the optionName argument and "<specific options>"
is a space separated list of specific option words.
The function takes good care of inserting minus signs before
each option, commas after, and an "or" before the last option.
.VE

.SH "SEE ALSO"
Tcl_Close(3), Tcl_OpenFileChannel(3), Tcl_SetErrno(3), Tcl_QueueEvent(3)

.SH KEYWORDS
blocking, channel driver, channel registration, channel type, nonblocking