crtchannel.3

tcl是工具命令语言

(thread)global list of all channels (of the current thread).
Application to a channel registered in some interpreter is not allowed.
.PP
\fBTcl_ClearChannelHandlers\fR removes all channelhandlers and event
scripts associated with the specified \fIchannel\fR, thus shutting
down all event processing for this channel.
.VE 8.4

.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 structure
was versioned starting in Tcl 8.3.2/8.4 to correct a problem with stacked
channel drivers.  See the \fBOLD CHANNEL TYPES\fR section below for
details about the old structure.
.PP
The \fBTcl_ChannelType\fR structure contains the following fields:
.CS
typedef struct Tcl_ChannelType {
	char *\fItypeName\fR;
	Tcl_ChannelTypeVersion \fIversion\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_DriverClose2Proc *\fIclose2Proc\fR;
	Tcl_DriverBlockModeProc *\fIblockModeProc\fR;	
	Tcl_DriverFlushProc *\fIflushProc\fR;	
	Tcl_DriverHandlerProc *\fIhandlerProc\fR;	
	Tcl_DriverWideSeekProc *\fIwideSeekProc\fR;
} Tcl_ChannelType;
.CE
.PP
The driver must provide implementations for all functions except
\fIblockModeProc\fR, \fIseekProc\fR, \fIsetOptionProc\fR,
\fIgetOptionProc\fR, and \fIclose2Proc\fR, which may be specified as
NULL.  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, except in the case of \fIflushProc\fR and
\fIhandlerProc\fR, which should specified as NULL if not otherwise defined.
.PP
The user should only use the above structure for \fBTcl_ChannelType\fR
instantiation.  When referencing fields in a \fBTcl_ChannelType\fR
structure, the following functions should be used to obtain the values:
\fBTcl_ChannelName\fR, \fBTcl_ChannelVersion\fR,
\fBTcl_ChannelBlockModeProc\fR, \fBTcl_ChannelCloseProc\fR,
\fBTcl_ChannelClose2Proc\fR, \fBTcl_ChannelInputProc\fR,
\fBTcl_ChannelOutputProc\fR, \fBTcl_ChannelSeekProc\fR,
.VS 8.4
\fBTcl_ChannelWideSeekProc\fR,
.VE 8.4
\fBTcl_ChannelSetOptionProc\fR, \fBTcl_ChannelGetOptionProc\fR,
\fBTcl_ChannelWatchProc\fR, \fBTcl_ChannelGetHandleProc\fR,
\fBTcl_ChannelFlushProc\fR, or \fBTcl_ChannelHandlerProc\fR.
.PP
The change to the structures was made in such a way that standard channel
types are binary compatible.  However, channel types that use stacked
channels (ie: TLS, Trf) have new versions to correspond to the above change
since the previous code for stacked channels had problems.

.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.
.PP
This value can be retrieved with \fBTcl_ChannelName\fR, which returns
a pointer to the string.

.SH VERSION
.PP
The \fIversion\fR field should be set to \fBTCL_CHANNEL_VERSION_2\fR.
If it is not set to this value \fBTCL_CHANNEL_VERSION_3\fR, then this
\fBTcl_ChannelType\fR is assumed to have the older structure.  See
\fBOLD CHANNEL TYPES\fR for more details.  While Tcl will recognize
and function with either structure, stacked channels must be of at
least \fBTCL_CHANNEL_VERSION_2\fR to function correctly.
.PP
This value can be retrieved with \fBTcl_ChannelVersion\fR, which returns
.VS 8.4
one of \fBTCL_CHANNEL_VERSION_3\fR,
.VE 8.4
\fBTCL_CHANNEL_VERSION_2\fR or \fBTCL_CHANNEL_VERSION_1\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.
.PP
This value can be retrieved with \fBTcl_ChannelBlockModeProc\fR, which returns
a pointer to the function.

.SH "CLOSEPROC AND CLOSE2PROC"
.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
error code. In addition, if an error occurs and \fIinterp\fR is not NULL,
the procedure should store an error message in the interpreter's result.
.PP
Alternatively, channels that support closing the read and write sides
independently may set \fIcloseProc\fR to \fBTCL_CLOSE2PROC\fR and set
\fIclose2Proc\fR to the address of a function that matches the
following prototype:
.PP
.CS
typedef int Tcl_DriverClose2Proc(
	ClientData \fIinstanceData\fR,
	Tcl_Interp *\fIinterp\fR,
	int \fIflags\fR);
.CE
.PP
The \fIclose2Proc\fR will be called with \fIflags\fR set to an OR'ed
combination of \fBTCL_CLOSE_READ\fR or \fBTCL_CLOSE_WRITE\fR to
indicate that the driver should close the read and/or write side of
the channel.  The channel driver may be invoked to perform
additional operations on the channel after \fIclose2Proc\fR is
called to close one or both sides of the channel.  If \fIflags\fR is
\fB0\fR (zero), the driver should close the channel in the manner
described above for \fIcloseProc\fR.  No further operations will be
invoked on this instance after \fIclose2Proc\fR is called with all
flags cleared.  In all cases, the \fIclose2Proc\fR function should
return zero if the close operation was successful; otherwise it should
return a nonzero POSIX error code. In addition, if an error occurs and
\fIinterp\fR is not NULL, the procedure should store an error message
in the interpreter's result.
.PP
These value can be retrieved with \fBTcl_ChannelCloseProc\fR or
\fBTcl_ChannelClose2Proc\fR, which returns a pointer to the respective
function.

.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.
.PP
This value can be retrieved with \fBTcl_ChannelInputProc\fR, which returns
a pointer to the function.

.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,
	CONST 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.
.PP
This value can be retrieved with \fBTcl_ChannelOutputProc\fR, which returns
a pointer to the function.

.SH "SEEKPROC AND WIDESEEKPROC"
.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_Seek\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.
.PP
.VS 8.4
If there is a non-NULL \fIseekProc\fR field, the \fIwideSeekProc\fR
field may contain the address of an alternative function to use which
handles wide (i.e. larger than 32-bit) offsets, so allowing seeks
within files larger than 2GB.  The \fIwideSeekProc\fR will be called