Index of Section 3 Manual Pages
| Interix / SUA | CrtChannel.3 | Interix / SUA |
Tcl_CreateChannel(3) Tcl Library Procedures Tcl_CreateChannel(3)
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NAME
Tcl_CreateChannel, Tcl_GetChannelInstanceData,
Tcl_GetChannelType, Tcl_GetChannelName, Tcl_GetChannelHan-
dle, Tcl_GetChannelMode, Tcl_GetChannelBufferSize,
Tcl_SetChannelBufferSize, Tcl_NotifyChannel, Tcl_BadChan-
nelOption, Tcl_ChannelName, Tcl_ChannelVersion, Tcl_Chan-
nelBlockModeProc, Tcl_ChannelCloseProc, Tcl_Channel-
Close2Proc, Tcl_ChannelInputProc, Tcl_ChannelOutputProc,
Tcl_ChannelSeekProc, Tcl_ChannelWideSeekProc, Tcl_Chan-
nelSetOptionProc, Tcl_ChannelGetOptionProc, Tcl_Channel-
WatchProc, Tcl_ChannelGetHandleProc, Tcl_ChannelFlushProc,
Tcl_ChannelHandlerProc, Tcl_IsChannelShared, Tcl_IsChan-
nelRegistered, Tcl_CutChannel, Tcl_SpliceChannel,
Tcl_IsChannelExisting, Tcl_ClearChannelHandlers,
Tcl_GetChannelThread, Tcl_ChannelBuffered - procedures for
creating and manipulating channels
SYNOPSIS
#include
Tcl_Channel
Tcl_CreateChannel(typePtr, channelName, instanceData, mask)
ClientData
Tcl_GetChannelInstanceData(channel)
Tcl_ChannelType *
Tcl_GetChannelType(channel)
CONST char *
Tcl_GetChannelName(channel)
int
Tcl_GetChannelHandle(channel, direction, handlePtr)
Tcl_ThreadId |
Tcl_GetChannelThread(channel) |
int
Tcl_GetChannelBufferSize(channel)
Tcl_SetChannelBufferSize(channel, size)
Tcl_NotifyChannel(channel, mask)
int
Tcl_BadChannelOption(interp, optionName, optionList)
int |
Tcl_IsChannelShared(channel) |
int |
Tcl_IsChannelRegistered(interp, channel) |
int |
Tcl_IsChannelExisting(channelName) |
void |
Tcl_CutChannel(channel) |
void |
Tcl_SpliceChannel(channel) |
void |
Tcl_ClearChannelHandlers(channel) |
int
Tcl_ChannelBuffered(channel)
CONST char *
Tcl_ChannelName(typePtr)
Tcl_ChannelTypeVersion
Tcl_ChannelVersion(typePtr)
Tcl_DriverBlockModeProc *
Tcl_ChannelBlockModeProc(typePtr)
Tcl_DriverCloseProc *
Tcl_ChannelCloseProc(typePtr)
Tcl_DriverClose2Proc *
Tcl_ChannelClose2Proc(typePtr)
Tcl_DriverInputProc *
Tcl_ChannelInputProc(typePtr)
Tcl_DriverOutputProc *
Tcl_ChannelOutputProc(typePtr)
Tcl_DriverSeekProc *
Tcl_ChannelSeekProc(typePtr)
Tcl_DriverWideSeekProc * |
Tcl_ChannelWideSeekProc(typePtr) |
Tcl_DriverSetOptionProc *
Tcl_ChannelSetOptionProc(typePtr)
Tcl_DriverGetOptionProc *
Tcl_ChannelGetOptionProc(typePtr)
Tcl_DriverWatchProc *
Tcl_ChannelWatchProc(typePtr)
Tcl_DriverGetHandleProc *
Tcl_ChannelGetHandleProc(typePtr)
Tcl_DriverFlushProc *
Tcl_ChannelFlushProc(typePtr)
Tcl_DriverHandlerProc *
Tcl_ChannelHandlerProc(typePtr)
ARGUMENTS
Tcl_ChannelType *typePtr (in) Points to a
structure con-
taining the
addresses of
procedures that
can be called
to perform I/O
and other func-
tions on the
channel.
CONST char *channelName (in) The name of
this channel,
such as file3;
must not be in
use by any
other channel.
Can be NULL, in
which case the
channel is cre-
ated without a
name.
ClientData instanceData (in) Arbitrary one-
word value to
be associated
with this chan-
nel. This
value is passed
to procedures
in typePtr when
they are
invoked.
int mask (in) OR-ed combina-
tion of
TCL_READABLE
and
TCL_WRITABLE to
indicate
whether a chan-
nel is readable
and writable.
Tcl_Channel channel (in) The channel to
operate on.
int direction (in) TCL_READABLE
means the input
handle is
wanted;
TCL_WRITABLE
means the out-
put handle is
wanted.
ClientData *handlePtr (out) Points to the
location where
the desired OS-
specific handle
should be
stored.
int size (in) The size, in
bytes, of
buffers to
allocate in
this channel.
int mask (in) An OR-ed combi-
nation of
TCL_READABLE,
TCL_WRITABLE
and TCL_EXCEP-
TION that indi-
cates events
that have
occurred on
this channel.
Tcl_Interp *interp (in) Current inter-
preter. (can be
NULL)
CONST char *optionName (in) Name of the
invalid option.
CONST char *optionList (in) Specific
options list
(space sepa-
rated words,
without "-") to
append to the
standard
generic options
list. Can be
NULL for
generic options
error message
only.
_________________________________________________________________
DESCRIPTION
Tcl uses a two-layered channel architecture. It provides a
generic upper layer to enable C and Tcl programs to per-
form 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 Tcl_OpenFileChannel.
The lower layer provides type-specific channel drivers for
each type of device supported on each platform. This man-
ual 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.
Channel drivers consist of a number of components: First,
each channel driver provides a Tcl_ChannelType structure
containing pointers to functions implementing the various
operations used by the generic layer to communicate with
the channel driver. The Tcl_ChannelType structure and the
functions referenced by it are described in the section
TCL_CHANNELTYPE, below.
Second, channel drivers usually provide a Tcl command to
create instances of that type of channel. For example, the
Tcl open command creates channels that use the file and
command channel drivers, and the Tcl socket command cre-
ates channels that use TCP sockets for network communica-
tion.
Third, a channel driver optionally provides a C function
to open channel instances of that type. For example,
Tcl_OpenFileChannel opens a channel that uses the file
channel driver, and Tcl_OpenTcpClient opens a channel that
uses the TCP network protocol. These creation functions
typically use Tcl_CreateChannel internally to open the
channel.
To add a new type of channel you must implement a C API or
a Tcl command that opens a channel by invoking Tcl_Create-
Channel. When your driver calls Tcl_CreateChannel it
passes in a Tcl_ChannelType structure describing the
driver's I/O procedures. The generic layer will then
invoke the functions referenced in that structure to per-
form operations on the channel.
Tcl_CreateChannel opens a new channel and associates the
supplied typePtr and instanceData with it. The channel is
opened in the mode indicated by mask. For a discussion of
channel drivers, their operations and the Tcl_ChannelType
structure, see the section TCL_CHANNELTYPE, below.
Tcl_CreateChannel interacts with the code managing the
standard channels. Once a standard channel was initialized
either through a call to Tcl_GetStdChannel or a call to
Tcl_SetStdChannel closing this standard channel will cause
the next call to Tcl_CreateChannel to make the new channel
the new standard channel too. See Tcl_StandardChannels for
a general treatise about standard channels and the
behaviour of the Tcl library with regard to them.
Tcl_GetChannelInstanceData returns the instance data asso-
ciated with the channel in channel. This is the same as
the instanceData argument in the call to Tcl_CreateChannel
that created this channel.
Tcl_GetChannelType returns a pointer to the Tcl_Channel-
Type structure used by the channel in the channel argu-
ment. This is the same as the typePtr argument in the call
to Tcl_CreateChannel that created this channel.
Tcl_GetChannelName returns a string containing the name
associated with the channel, or NULL if the channelName
argument to Tcl_CreateChannel was NULL.
Tcl_GetChannelHandle places the OS-specific device handle
associated with channel for the given direction in the
location specified by handlePtr and returns TCL_OK. If
the channel does not have a device handle for the speci-
fied direction, then TCL_ERROR is returned instead. Dif-
ferent channel drivers will return different types of han-
dle. Refer to the manual entries for each driver to
determine what type of handle is returned. |
Tcl_GetChannelThread returns the id of the thread cur- |
rently managing the specified channel. This allows channel |
drivers to send their file events to the correct event |
queue even for a multi-threaded core.
Tcl_GetChannelMode returns an OR-ed combination of
TCL_READABLE and TCL_WRITABLE, indicating whether the
channel is open for input and output.
Tcl_GetChannelBufferSize returns the size, in bytes, of
buffers allocated to store input or output in channel. If
the value was not set by a previous call to Tcl_SetChan-
nelBufferSize, described below, then the default value of
4096 is returned.
Tcl_SetChannelBufferSize sets the size, in bytes, of
buffers that will be allocated in subsequent operations on
the channel to store input or output. The size argument
should be between ten and one million, allowing buffers of
ten bytes to one million bytes. If size is outside this
range, Tcl_SetChannelBufferSize sets the buffer size to
4096.
Tcl_NotifyChannel is called by a channel driver to indi-
cate to the generic layer that the events specified by
mask have occurred on the channel. Channel drivers are
responsible for invoking this function whenever the chan-
nel handlers need to be called for the channel. See
WATCHPROC below for more details.
Tcl_BadChannelOption is called from driver specific set or
get option procs to generate a complete error message.
Tcl_ChannelBuffered returns the number of bytes of input
currently buffered in the internal buffer (push back area)
of the channel itself. It does not report about the data
in the overall buffers for the stack of channels the sup-
plied channel is part of.
Tcl_IsChannelShared checks the refcount of the specified |
channel and returns whether the channel was shared among |
multiple interpreters (result == 1) or not (result == 0). |
Tcl_IsChannelRegistered checks whether the specified chan- |
nel is registered in the given interpreter (result == 1) |
or not (result == 0). |
Tcl_IsChannelExisting checks whether a channel with the |
specified name is registered in the (thread)-global list |
of all channels (result == 1) or not (result == 0). |
Tcl_CutChannel removes the specified channel from the |
(thread)global list of all channels (of the current |
thread). Application to a channel still registered in |
some interpreter is not allowed. |
Tcl_SpliceChannel adds the specified channel to the |
(thread)global list of all channels (of the current |
thread). Application to a channel registered in some |
interpreter is not allowed. |
Tcl_ClearChannelHandlers removes all channelhandlers and |
event scripts associated with the specified channel, thus |
shutting down all event processing for this channel.
TCL_CHANNELTYPE
A channel driver provides a Tcl_ChannelType 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 OLD CHANNEL TYPES sec-
tion below for details about the old structure.
The Tcl_ChannelType structure contains the following
fields:
typedef struct Tcl_ChannelType {
char *typeName;
Tcl_ChannelTypeVersion version;
Tcl_DriverCloseProc *closeProc;
Tcl_DriverInputProc *inputProc;
Tcl_DriverOutputProc *outputProc;
Tcl_DriverSeekProc *seekProc;
Tcl_DriverSetOptionProc *setOptionProc;
Tcl_DriverGetOptionProc *getOptionProc;
Tcl_DriverWatchProc *watchProc;
Tcl_DriverGetHandleProc *getHandleProc;
Tcl_DriverClose2Proc *close2Proc;
Tcl_DriverBlockModeProc *blockModeProc;
Tcl_DriverFlushProc *flushProc;
Tcl_DriverHandlerProc *handlerProc;
Tcl_DriverWideSeekProc *wideSeekProc;
} Tcl_ChannelType;
The driver must provide implementations for all functions
except blockModeProc, seekProc, setOptionProc, getOption-
Proc, and close2Proc, which may be specified as NULL.
Other functions that can not be implemented for this type
of device should return EINVAL when invoked to indicate
that they are not implemented, except in the case of
flushProc and handlerProc, which should specified as NULL
if not otherwise defined.
The user should only use the above structure for Tcl_Chan-
nelType instantiation. When referencing fields in a
Tcl_ChannelType structure, the following functions should
be used to obtain the values: Tcl_ChannelName, Tcl_Chan-
nelVersion, Tcl_ChannelBlockModeProc, Tcl_ChannelClose-
Proc, Tcl_ChannelClose2Proc, Tcl_ChannelInputProc,
Tcl_ChannelOutputProc, Tcl_ChannelSeekProc, Tcl_Channel- |
WideSeekProc, Tcl_ChannelSetOptionProc, Tcl_ChannelGetOp-
tionProc, Tcl_ChannelWatchProc, Tcl_ChannelGetHandleProc,
Tcl_ChannelFlushProc, or Tcl_ChannelHandlerProc.
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.
TYPENAME
The typeName field contains a null-terminated string that
identifies the type of the device implemented by this
driver, e.g. file or socket.
This value can be retrieved with Tcl_ChannelName, which
returns a pointer to the string.
VERSION
The version field should be set to TCL_CHANNEL_VERSION_2.
If it is not set to this value TCL_CHANNEL_VERSION_3, then
this Tcl_ChannelType is assumed to have the older struc-
ture. See OLD CHANNEL TYPES for more details. While Tcl
will recognize and function with either structure, stacked
channels must be of at least TCL_CHANNEL_VERSION_2 to
function correctly.
This value can be retrieved with Tcl_ChannelVersion, which
returns one of TCL_CHANNEL_VERSION_3, TCL_CHANNEL_VER- |
SION_2 or TCL_CHANNEL_VERSION_1.
BLOCKMODEPROC
The blockModeProc field contains the address of a function
called by the generic layer to set blocking and nonblock-
ing mode on the device. BlockModeProc should match the
following prototype:
typedef int Tcl_DriverBlockModeProc(
ClientData instanceData,
int mode);
The instanceData is the same as the value passed to
Tcl_CreateChannel when this channel was created. The mode
argument is either TCL_MODE_BLOCKING or TCL_MODE_NONBLOCK-
ING to set the device into blocking or nonblocking mode.
The function should return zero if the operation was suc-
cessful, or a nonzero POSIX error code if the operation
failed.
If the operation is successful, the function can modify
the supplied instanceData 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.
This value can be retrieved with Tcl_ChannelBlockModeProc,
which returns a pointer to the function.
CLOSEPROC AND CLOSE2PROC
The closeProc field contains the address of a function
called by the generic layer to clean up driver-related
information when the channel is closed. CloseProc must
match the following prototype:
typedef int Tcl_DriverCloseProc(
ClientData instanceData,
Tcl_Interp *interp);
The instanceData argument is the same as the value pro-
vided to Tcl_CreateChannel 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 closeProc.
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 interp is
not NULL, the procedure should store an error message in
the interpreter's result.
Alternatively, channels that support closing the read and
write sides independently may set closeProc to
TCL_CLOSE2PROC and set close2Proc to the address of a
function that matches the following prototype:
typedef int Tcl_DriverClose2Proc(
ClientData instanceData,
Tcl_Interp *interp,
int flags);
The close2Proc will be called with flags set to an OR'ed
combination of TCL_CLOSE_READ or TCL_CLOSE_WRITE to indi-
cate 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
close2Proc is called to close one or both sides of the
channel. If flags is 0 (zero), the driver should close
the channel in the manner described above for closeProc.
No further operations will be invoked on this instance
after close2Proc is called with all flags cleared. In all
cases, the close2Proc 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 interp is not NULL, the procedure should store
an error message in the interpreter's result.
These value can be retrieved with Tcl_ChannelCloseProc or
Tcl_ChannelClose2Proc, which returns a pointer to the
respective function.
INPUTPROC
The inputProc 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. InputProc must
match the following prototype:
typedef int Tcl_DriverInputProc(
ClientData instanceData,
char *buf,
int bufSize,
int *errorCodePtr);
InstanceData is the same as the value passed to Tcl_Creat-
eChannel when the channel was created. The buf argument
points to an array of bytes in which to store input from
the device, and the bufSize argument indicates how many
bytes are available at buf.
The errorCodePtr 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.
The function should read data from the input device encap-
sulated by the channel and store it at buf. On success,
the function should return a nonnegative integer indicat-
ing how many bytes were read from the input device and
stored at buf. On error, the function should return -1. If
an error occurs after some data has been read from the
device, that data is lost.
If inputProc can determine that the input device has some
data available but less than requested by the bufSize
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 EAGAIN error. If the input device has no data available
whatsoever and the channel is in blocking mode, the func-
tion 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.
This value can be retrieved with Tcl_ChannelInputProc,
which returns a pointer to the function.
OUTPUTPROC
The outputProc field contains the address of a function
called by the generic layer to transfer data from an
internal buffer to the output device. OutputProc must
match the following prototype:
typedef int Tcl_DriverOutputProc(
ClientData instanceData,
CONST char *buf,
int toWrite,
int *errorCodePtr);
InstanceData is the same as the value passed to Tcl_Creat-
eChannel when the channel was created. The buf argument
contains an array of bytes to be written to the device,
and the toWrite argument indicates how many bytes are to
be written from the buf argument.
The errorCodePtr 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.
The function should write the data at buf to the output
device encapsulated by the channel. On success, the func-
tion should return a nonnegative integer indicating how
many bytes were written to the output device. The return
value is normally the same as toWrite, 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.
If the channel is nonblocking and the output device is
unable to absorb any data whatsoever, the function should
return -1 with an EAGAIN error without writing any data.
This value can be retrieved with Tcl_ChannelOutputProc,
which returns a pointer to the function.
SEEKPROC AND WIDESEEKPROC
The seekProc 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. SeekProc must match the following prototype:
typedef int Tcl_DriverSeekProc(
ClientData instanceData,
long offset,
int seekMode,
int *errorCodePtr);
The instanceData argument is the same as the value given
to Tcl_CreateChannel when this channel was created. Off-
set and seekMode have the same meaning as for the Tcl_Seek
procedure (described in the manual entry for Tcl_Open-
FileChannel).
The errorCodePtr argument points to an integer variable
provided by the generic layer for returning errno values
from the function. The function should set this variable
to a POSIX error code if an error occurs. The function
should store an EINVAL error code if the channel type does
not implement seeking.
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.
If there is a non-NULL seekProc field, the wideSeekProc |
field may contain the address of an alternative function |
to use which handles wide (i.e. larger than 32-bit) off- |
sets, so allowing seeks within files larger than 2GB. The |
wideSeekProc will be called in preference to the seekProc, |
but both must be defined if the wideSeekProc is defined. |
WideSeekProc must match the following prototype: |
typedef Tcl_WideInt Tcl_DriverWideSeekProc( |
ClientData instanceData, |
Tcl_WideInt offset, |
int seekMode, |
int *errorCodePtr); |
The arguments and return values mean the same thing as |
with seekProc above, except that the type of offsets and |
the return type are different. |
The seekProc value can be retrieved with Tcl_Chan- |
nelSeekProc, which returns a pointer to the function, and |
similarly the wideSeekProc can be retrieved with Tcl_Chan- |
nelWideSeekProc.
SETOPTIONPROC
The setOptionProc field contains the address of a function
called by the generic layer to set a channel type specific
option on a channel. setOptionProc must match the follow-
ing prototype:
typedef int Tcl_DriverSetOptionProc(
ClientData instanceData,
Tcl_Interp *interp,
CONST char *optionName,
CONST char *newValue);
optionName is the name of an option to set, and newValue
is the new value for that option, as a string. The
instanceData is the same as the value given to Tcl_Create-
Channel when this channel was created. The function should
do whatever channel type specific action is required to
implement the new value of the option.
Some options are handled by the generic code and this
function is never called to set them, e.g. -blockmode.
Other options are specific to each channel type and the
setOptionProc procedure of the channel driver will get
called to implement them. The setOptionProc field can be
NULL, which indicates that this channel type supports no
type specific options.
If the option value is successfully modified to the new
value, the function returns TCL_OK. It should call
Tcl_BadChannelOption which itself returns TCL_ERROR if the
optionName is unrecognized. If newValue 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 result field of interp if interp is not NULL. The
function should also call Tcl_SetErrno to store an appro-
priate POSIX error code.
This value can be retrieved with Tcl_ChannelSetOptionProc,
which returns a pointer to the function.
GETOPTIONPROC
The getOptionProc 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. getOptionProc must
match the following prototype:
typedef int Tcl_DriverGetOptionProc(
ClientData instanceData,
Tcl_Interp *interp,
CONST char *optionName,
Tcl_DString *optionValue);
OptionName 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 optionValue. If optionName is NULL, the function
stores in optionValue an alternating list of all supported
options and their current values. On success, the func-
tion returns TCL_OK. It should call Tcl_BadChannelOption
which itself returns TCL_ERROR if the optionName is unrec-
ognized. If a system call error occurs, the function
should leave an error message in the result of interp if
interp is not NULL. The function should also call
Tcl_SetErrno to store an appropriate POSIX error code.
Some options are handled by the generic code and this
function is never called to retrieve their value, e.g.
-blockmode. Other options are specific to each channel
type and the getOptionProc procedure of the channel driver
will get called to implement them. The getOptionProc field
can be NULL, which indicates that this channel type sup-
ports no type specific options.
This value can be retrieved with Tcl_ChannelGetOptionProc,
which returns a pointer to the function.
WATCHPROC
The watchProc field contains the address of a function
called by the generic layer to initialize the event noti-
fication mechanism to notice events of interest on this
channel. WatchProc should match the following prototype:
typedef void Tcl_DriverWatchProc(
ClientData instanceData,
int mask);
The instanceData is the same as the value passed to
Tcl_CreateChannel when this channel was created. The mask
argument is an OR-ed combination of TCL_READABLE,
TCL_WRITABLE and TCL_EXCEPTION; it indicates events the
caller is interested in noticing on this channel.
The function should initialize device type specific mecha-
nisms 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 Tcl_NotifyChannel to inform the generic chan-
nel 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 Tcl_QueueEvent for details on how to queue
an event.
This value can be retrieved with Tcl_ChannelWatchProc,
which returns a pointer to the function.
GETHANDLEPROC
The getHandleProc field contains the address of a function
called by the generic layer to retrieve a device-specific
handle from the channel. GetHandleProc should match the
following prototype:
typedef int Tcl_DriverGetHandleProc(
ClientData instanceData,
int direction,
ClientData *handlePtr);
InstanceData is the same as the value passed to Tcl_Creat-
eChannel when this channel was created. The direction
argument is either TCL_READABLE to retrieve the handle
used for input, or TCL_WRITABLE to retrieve the handle
used for output.
If the channel implementation has device-specific handles,
the function should retrieve the appropriate handle asso-
ciated with the channel, according the direction argument.
The handle should be stored in the location referred to by
handlePtr, and TCL_OK 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 TCL_ERROR.
This value can be retrieved with Tcl_ChannelGetHandleProc,
which returns a pointer to the function.
FLUSHPROC
The flushProc field is currently reserved for future use.
It should be set to NULL. FlushProc should match the fol-
lowing prototype:
typedef int Tcl_DriverFlushProc(
ClientData instanceData);
This value can be retrieved with Tcl_ChannelFlushProc,
which returns a pointer to the function.
HANDLERPROC
The handlerProc field contains the address of a function
called by the generic layer to notify the channel that an
event occurred. It should be defined for stacked channel
drivers that wish to be notified of events that occur on
the underlying (stacked) channel. HandlerProc should
match the following prototype:
typedef int Tcl_DriverHandlerProc(
ClientData instanceData,
int interestMask);
InstanceData is the same as the value passed to Tcl_Creat-
eChannel when this channel was created. The interestMask
is an OR-ed combination of TCL_READABLE or TCL_WRITABLE;
it indicates what type of event occurred on this channel.
This value can be retrieved with Tcl_ChannelHandlerProc,
which returns a pointer to the function.
TCL_BADCHANNELOPTION
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.
It always return TCL_ERROR
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
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"
``blah'' is the optionName argument and ``'' 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.
OLD CHANNEL TYPES
The original (8.3.1 and below) Tcl_ChannelType structure
contains the following fields:
typedef struct Tcl_ChannelType {
char *typeName;
Tcl_DriverBlockModeProc *blockModeProc;
Tcl_DriverCloseProc *closeProc;
Tcl_DriverInputProc *inputProc;
Tcl_DriverOutputProc *outputProc;
Tcl_DriverSeekProc *seekProc;
Tcl_DriverSetOptionProc *setOptionProc;
Tcl_DriverGetOptionProc *getOptionProc;
Tcl_DriverWatchProc *watchProc;
Tcl_DriverGetHandleProc *getHandleProc;
Tcl_DriverClose2Proc *close2Proc;
} Tcl_ChannelType;
It is still possible to create channel with the above
structure. The internal channel code will determine the
version. It is imperative to use the new Tcl_ChannelType
structure if you are creating a stacked channel driver,
due to problems with the earlier stacked channel implemen-
tation (in 8.2.0 to 8.3.1).
Prior to 8.4.0 (i.e. during the later releases of 8.3 and |
early part of the 8.4 development cycle) the Tcl_Channel- |
Type structure contained the following fields: |
typedef struct Tcl_ChannelType { |
char *typeName; |
Tcl_ChannelTypeVersion version; |
Tcl_DriverCloseProc *closeProc; |
Tcl_DriverInputProc *inputProc; |
Tcl_DriverOutputProc *outputProc; |
Tcl_DriverSeekProc *seekProc; |
Tcl_DriverSetOptionProc *setOptionProc; |
Tcl_DriverGetOptionProc *getOptionProc; |
Tcl_DriverWatchProc *watchProc; |
Tcl_DriverGetHandleProc *getHandleProc; |
Tcl_DriverClose2Proc *close2Proc; |
Tcl_DriverBlockModeProc *blockModeProc; |
Tcl_DriverFlushProc *flushProc; |
Tcl_DriverHandlerProc *handlerProc; |
} Tcl_ChannelType; |
When the above structure is registered as a channel type, |
the version field should always be TCL_CHANNEL_VERSION_2.
SEE ALSO
Tcl_Close(3), Tcl_OpenFileChannel(3), Tcl_SetErrno(3),
Tcl_QueueEvent(3), Tcl_StackChannel(3), Tcl_GetStdChan-
nel(3)
KEYWORDS
blocking, channel driver, channel registration, channel
type, nonblocking
Tcl 8.3 Tcl_CreateChannel(3)