Tcl Library Procedures Tcl_CreateChannel(3TCL)
_________________________________________________________________
NAME
Tcl_CreateChannel, Tcl_GetChannelInstanceData,
Tcl_GetChannelType, Tcl_GetChannelName,
Tcl_GetChannelHandle, Tcl_GetChannelMode,
Tcl_GetChannelBufferSize, Tcl_SetChannelBufferSize,
Tcl_NotifyChannel, Tcl_BadChannelOption, Tcl_ChannelName,
Tcl_ChannelVersion, Tcl_ChannelBlockModeProc,
Tcl_ChannelCloseProc, Tcl_ChannelClose2Proc,
Tcl_ChannelInputProc, Tcl_ChannelOutputProc,
Tcl_ChannelSeekProc, Tcl_ChannelWideSeekProc,
Tcl_ChannelSetOptionProc, Tcl_ChannelGetOptionProc,
Tcl_ChannelWatchProc, Tcl_ChannelGetHandleProc,
Tcl_ChannelFlushProc, Tcl_ChannelHandlerProc,
Tcl_ChannelThreadActionProc, Tcl_IsChannelShared,
Tcl_IsChannelRegistered, Tcl_CutChannel, Tcl_SpliceChannel,
Tcl_IsChannelExisting, Tcl_ClearChannelHandlers,
Tcl_GetChannelThread, Tcl_ChannelBuffered - procedures for
creating and manipulating channelsSYNOPSIS
#include
Tcl_Channel
Tcl_CreateChannel(typePtr, channelName, instanceData, mask)
ClientDataTcl_GetChannelInstanceData(channel)
Tcl_ChannelType *
Tcl_GetChannelType(channel)
CONST char *Tcl_GetChannelName(channel)
intTcl_GetChannelHandle(channel, direction, handlePtr)
Tcl_ThreadId |
Tcl_GetChannelThread(channel) |
intTcl_GetChannelMode(channel)
intTcl_GetChannelBufferSize(channel)
Tcl_SetChannelBufferSize(channel, size)
Tcl_NotifyChannel(channel, mask)
Tcl Last change: 8.4 1Tcl Library Procedures Tcl_CreateChannel(3TCL)
intTcl_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) |
intTcl_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_DriverThreadActionProc * |
Tcl Last change: 8.4 2Tcl Library Procedures Tcl_CreateChannel(3TCL)
Tcl_ChannelThreadActionProc(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)
ARGUMENTSTcl_ChannelType *typePtr (in) Points to a
structure con-
taining theaddresses of pro-
cedures that canbe called to per-
form I/O and other functions 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 created without a name.
ClientData instanceData (in) Arbitrary one-
word value to be associated with this channel. This value ispassed to pro-
cedures in typePtr when they are invoked. Tcl Last change: 8.4 3Tcl Library Procedures Tcl_CreateChannel(3TCL)
int mask (in) OR-ed combination
of TCL_READABLE
and TCL_WRITABLE
to indicate whether a channel 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 output handle is wanted. ClientData *handlePtr (out) Points to the location wherethe 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 combina-
tion ofTCL_READABLE,
TCL_WRITABLE and
TCL_EXCEPTION
that indicates 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 separated words,without "-") to
append to the standard generic Tcl Last change: 8.4 4Tcl Library Procedures Tcl_CreateChannel(3TCL)
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 perform input and output using the same APIs for a variety of files, devices, sockets etc. The generic C APIs are described inthe manual entry for Tcl_OpenFileChannel.
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 thegeneric layer and the type-specific channel drivers. It
also explains how new types of channels can be added by pro-
viding 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 thechannel driver. The Tcl_ChannelType structure and the func-
tions referenced by it are described in the sectionTCL_CHANNELTYPE, below.
Second, channel drivers usually provide a Tcl command to create instances of that type of channel. For example, theTcl open command creates channels that use the file and com-
mand channel drivers, and the Tcl socket command creates channels that use TCP sockets for network communication. 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 chan-
nel driver, and Tcl_OpenTcpClient opens a channel that uses
the TCP network protocol. These creation functions typi-
cally 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 invokingTcl_CreateChannel. 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 perform opera-
tions on the channel. Tcl Last change: 8.4 5Tcl Library Procedures Tcl_CreateChannel(3TCL)
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 ofchannel drivers, their operations and the Tcl_ChannelType
structure, see the section TCL_CHANNELTYPE, below.
Tcl_CreateChannel interacts with the code managing the stan-
dard channels. Once a standard channel was initializedeither 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 associ-
ated with the channel in channel. This is the same as theinstanceData argument in the call to Tcl_CreateChannel that
created this channel.Tcl_GetChannelType returns a pointer to the Tcl_ChannelType
structure used by the channel in the channel argument. This is the same as the typePtr argument in the call toTcl_CreateChannel that created this channel.
Tcl_GetChannelName returns a string containing the name
associated with the channel, or NULL if the channelNameargument to Tcl_CreateChannel was NULL.
Tcl_GetChannelHandle places the OS-specific device handle
associated with channel for the given direction in the loca-
tion specified by handlePtr and returns TCL_OK. If the
channel does not have a device handle for the specifieddirection, then TCL_ERROR 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.Tcl_GetChannelThread returns the id of the thread currently |
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 chan-
nel 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 toTcl_SetChannelBufferSize, described below, then the default
value of 4096 is returned. Tcl Last change: 8.4 6Tcl Library Procedures Tcl_CreateChannel(3TCL)
Tcl_SetChannelBufferSize sets the size, in bytes, of buffers
that will be allocated in subsequent operations on the chan-
nel 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 indicate
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 channel 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 supplied 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 channel |
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 inter- |
preter is not allowed. Also notifies the driver if the |Tcl_ChannelType version is TCL_CHANNEL_VERSION_4 (or |
higher), and Tcl_DriverThreadActionProc is defined for it.
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. Also notifies the driver if the |Tcl_ChannelType version is TCL_CHANNEL_VERSION_4 (or |
higher), and Tcl_DriverThreadActionProc is defined for it.
Tcl_ClearChannelHandlers removes all channelhandlers and
event scripts associated with the specified channel, thus shutting down all event processing for this channel. Tcl Last change: 8.4 7Tcl Library Procedures Tcl_CreateChannel(3TCL)
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 section 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_DriverThreadActionProc *threadActionProc;
} Tcl_ChannelType;
It is not necessary to provide implementations for all chan-
nel operations. Those which are not necessary may be set to NULL in the struct: blockModeProc, seekProc, setOptionProc, getOptionProc, and close2Proc, in addition to flushProc, handlerProc, and threadActionProc. Other functions thatcannot be implemented in a meaningful way should return EIN-
VAL when called, to indicate that the operations they represent are not available. Also note that wideSeekProc can be NULL if seekProc is. The user should only use the above structure forTcl_ChannelType instantiation. When referencing fields in a
Tcl_ChannelType structure, the following functions should be
used to obtain the values: Tcl_ChannelName,
Tcl_ChannelVersion, Tcl_ChannelBlockModeProc,
Tcl_ChannelCloseProc, Tcl_ChannelClose2Proc,
Tcl_ChannelInputProc, Tcl_ChannelOutputProc,
Tcl_ChannelSeekProc, Tcl_ChannelWideSeekProc, |
Tcl_ChannelThreadActionProc, Tcl_ChannelSetOptionProc,
Tcl_ChannelGetOptionProc, Tcl_ChannelWatchProc,
Tcl_ChannelGetHandleProc, Tcl_ChannelFlushProc, or
Tcl_ChannelHandlerProc.
Tcl Last change: 8.4 8Tcl Library Procedures Tcl_CreateChannel(3TCL)
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. VERSIONThe version field should be set to the version of the struc-
ture that you require. TCL_CHANNEL_VERSION_2 is the minimum
recommended. TCL_CHANNEL_VERSION_3 must be set to specifiy |
the wideSeekProc member. TCL_CHANNEL_VERSION_4 must be set |
to specifiy the threadActionProc member (includes | wideSeekProc). If it is not set to any of these, then thisTcl_ChannelType is assumed to have the original structure.
See OLD CHANNEL TYPES for more details. While Tcl willrecognize and function with either structures, stacked chan-
nels 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_4, TCL_CHANNEL_VERSION_3, |
TCL_CHANNEL_VERSION_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 nonblockingmode on the device. BlockModeProc should match the follow-
ing prototype:typedef int Tcl_DriverBlockModeProc(
ClientData instanceData, int mode); The instanceData is the same as the value passed toTcl_CreateChannel when this channel was created. The mode
argument is either TCL_MODE_BLOCKING or TCL_MODE_NONBLOCKING
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. Tcl Last change: 8.4 9Tcl Library Procedures Tcl_CreateChannel(3TCL)
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 blockingor nonblocking behavior. For some device types, the block-
ing 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. A channel driver not supplying a blockModeProc has to be very, very careful. It has to tell the generic layer exactly which blocking mode is acceptable to it, and should this also document for the user so that the blocking mode of thechannel is not changed to an inacceptable value. Any confu-
sion here may lead the interpreter into a (spurious and dif-
ficult to find) deadlock. CLOSEPROC AND CLOSE2PROC The closeProc field contains the address of a functioncalled 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 providedto Tcl_CreateChannel when the channel was created. The func-
tion should release any storage maintained by the channeldriver for this channel, and close the input and output dev-
ices 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 toTCL_CLOSE2PROC and set close2Proc to the address of a func-
tion that matches the following prototype:typedef int Tcl_DriverClose2Proc(
ClientData instanceData, Tcl Last change: 8.4 10Tcl Library Procedures Tcl_CreateChannel(3TCL)
Tcl_Interp *interp,
int flags); The close2Proc will be called with flags set to an OR'edcombination of TCL_CLOSE_READ or TCL_CLOSE_WRITE 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 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 calledwith all flags cleared. In all cases, the close2Proc func-
tion should return zero if the close operation was success-
ful; 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 toTcl_CreateChannel 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 pro-
vided by the generic layer. If an error occurs, the functionshould set the variable to a POSIX error code that identi-
fies the error that occurred.The function should read data from the input device encapsu-
lated by the channel and store it at buf. On success, the function should return a nonnegative integer indicating how many bytes were read from the input device and stored atbuf. On error, the function should return -1. If an error
Tcl Last change: 8.4 11Tcl Library Procedures Tcl_CreateChannel(3TCL)
occurs after some data has been read from the device, that data is lost. If inputProc can determine that the input device has somedata available but less than requested by the bufSize argu-
ment, 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 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.This value can be retrieved with Tcl_ChannelInputProc, which
returns a pointer to the function.OUTPUTPROC
The outputProc field contains the address of a functioncalled by the generic layer to transfer data from an inter-
nal 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 toTcl_CreateChannel 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 pro-
vided by the generic layer. If an error occurs, the functionshould set this variable to a POSIX error code that identi-
fies the error.The function should write the data at buf to the output dev-
ice 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 toWrite, but may be less in some cases such as if the output operation is interrupted by asignal. If an error occurs the function should return -1.
In case of error, some data may have been written to the device. Tcl Last change: 8.4 12Tcl Library Procedures Tcl_CreateChannel(3TCL)
If the channel is nonblocking and the output device is unable to absorb any data whatsoever, the function shouldreturn -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 calledby the generic layer to move the access point at which sub-
sequent 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 toTcl_CreateChannel when this channel was created. Offset and
seekMode have the same meaning as for the Tcl_Seek procedure
(described in the manual entry for Tcl_OpenFileChannel).
The errorCodePtr argument points to an integer variable pro-
vided 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) offsets, 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 | Tcl Last change: 8.4 13Tcl Library Procedures Tcl_CreateChannel(3TCL)
return type are different. | The seekProc value can be retrieved with |Tcl_ChannelSeekProc, which returns a pointer to the func- |
tion, and similarly the wideSeekProc can be retrieved with |Tcl_ChannelWideSeekProc.
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 following 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 instanceDatais the same as the value given to Tcl_CreateChannel 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 func-
tion is never called to set them, e.g. -blockmode. Other
options are specific to each channel type and the setOp-
tionProc 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 newvalue, 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 inthe result field of interp if interp is not NULL. The func-
tion should also call Tcl_SetErrno to store an appropriate
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 Tcl Last change: 8.4 14Tcl Library Procedures Tcl_CreateChannel(3TCL)
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 functionreturns TCL_OK. It should call Tcl_BadChannelOption which
itself returns TCL_ERROR if the optionName is unrecognized.
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 func-
tion is never called to retrieve their value, e.g. -block-
mode. 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 supports 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 functioncalled by the generic layer to initialize the event notifi-
cation mechanism to notice events of interest on this chan-
nel. WatchProc should match the following prototype:typedef void Tcl_DriverWatchProc(
ClientData instanceData, int mask); The instanceData is the same as the value passed toTcl_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 mechan-
isms to notice when an event of interest is present on the Tcl Last change: 8.4 15Tcl Library Procedures Tcl_CreateChannel(3TCL)
channel. When one or more of the designated events occurson the channel, the channel driver is responsible for cal-
ling Tcl_NotifyChannel to inform the generic channel module.
The driver should take care not to starve other channel drivers or sources of callbacks by invokingTcl_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 thedescription 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 functioncalled 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 toTcl_CreateChannel when this channel was created. The direc-
tion 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 associ-
ated with the channel, according the direction argument. The handle should be stored in the location referred to byhandlePtr, 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 functionshould 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); Tcl Last change: 8.4 16Tcl Library Procedures Tcl_CreateChannel(3TCL)
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 toTcl_CreateChannel 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. THREADACTIONPROC |The threadActionProc field contains the address of the func- |
tion called by the generic layer when a channel is created, |closed, or going to move to a different thread, i.e. when- |
ever thread-specific driver state might have to initialized |
or updated. It can be NULL. The action |TCL_CHANNEL_THREAD_REMOVE is used to notify the driver that |
it should update or remove any thread-specific data it might |
be maintaining for the channel. |The action TCL_CHANNEL_THREAD_INSERT is used to notify the |
driver that it should update or initialize any thread- |
specific data it might be maintaining using the calling |thread as the associate. See Tcl_CutChannel and |
Tcl_SpliceChannel for more detail. |
typedef void Tcl_DriverThreadActionProc( |
ClientData instanceData, | int action); | InstanceData is the same as the value passed to |Tcl_CreateChannel when this channel was created. |
These values can be retrieved with |Tcl_ChannelThreadActionProc, which returns a pointer to the |
function. Tcl Last change: 8.4 17Tcl Library Procedures Tcl_CreateChannel(3TCL)
TCL_BADCHANNELOPTION
This procedure generates a "bad option" error message in an (optional) interpreter. It is used by channel drivers whena 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 struc-
ture. 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 implementation (in 8.2.0 to 8.3.1). Tcl Last change: 8.4 18Tcl Library Procedures Tcl_CreateChannel(3TCL)
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_ChannelType |
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(3TCL), Tcl_OpenFileChannel(3TCL),
Tcl_SetErrno(3TCL), Tcl_QueueEvent(3TCL),
Tcl_StackChannel(3TCL), Tcl_GetStdChannel(3TCL)
KEYWORDS blocking, channel driver, channel registration, channel type, nonblockingATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:_______________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
|____________________|__________________|_
| Availability | runtime/tcl-8 |
|____________________|__________________|_
| Interface Stability| Uncommitted ||____________________|_________________|
NOTES Source for Tcl is available on http://opensolaris.org. Tcl Last change: 8.4 19