Партнёры:
Хостинг:
_________________________________________________________________
NAME
Tcl_OpenFileChannel, Tcl_OpenCommandChannel,
Tcl_MakeFileChannel, Tcl_GetChannel, Tcl_GetChannelNames,
Tcl_GetChannelNamesEx, Tcl_RegisterChannel,
Tcl_UnregisterChannel, Tcl_Close, Tcl_ReadChars, Tcl_Read,
Tcl_GetsObj, Tcl_Gets, Tcl_WriteObj, Tcl_WriteChars,
Tcl_Write, Tcl_Flush, Tcl_Seek, Tcl_Tell,
Tcl_GetChannelOption, Tcl_SetChannelOption, Tcl_Eof,
Tcl_InputBlocked, Tcl_InputBuffered, Tcl_Ungets - buffered
I/O facilities using channels
SYNOPSIS
#include <tcl.h>
typedef ... Tcl_Channel;
Tcl_Channel
Tcl_OpenFileChannel(interp, fileName, mode, permissions)
Tcl_Channel
Tcl_OpenCommandChannel(interp, argc, argv, flags)
Tcl_Channel |
Tcl_MakeFileChannel(handle, readOrWrite) |
Tcl_Channel
Tcl_GetChannel(interp, channelName, modePtr)
int |
Tcl_GetChannelNames(interp) |
int |
Tcl_GetChannelNamesEx(interp, pattern) |
void
Tcl_RegisterChannel(interp, channel)
int
Tcl_UnregisterChannel(interp, channel)
int
Tcl_Close(interp, channel)
int |
Tcl_ReadChars(channel, readObjPtr, charsToRead, appendFlag) |
int |
Tcl_Read(channel, byteBuf, bytesToRead) |
int |
Tcl_GetsObj(channel, lineObjPtr) |
int |
Tcl_Gets(channel, lineRead) |
int |
Tcl_Ungets(channel, input, inputLen, addAtEnd) |
int |
Tcl_WriteObj(channel, writeObjPtr) |
int |
Tcl_WriteChars(channel, charBuf, bytesToWrite) |
int |
Tcl_Write(channel, byteBuf, bytesToWrite) |
int
Tcl_Eof(channel)
int
Tcl_Flush(channel)
int
Tcl_InputBlocked(channel)
int
Tcl_InputBuffered(channel)
int
Tcl_Seek(channel, offset, seekMode)
int
Tcl_Tell(channel)
int
Tcl_GetChannelOption(interp, channel, optionName, optionValue)
int
Tcl_SetChannelOption(interp, channel, optionName, newValue)
ARGUMENTS
Tcl_Interp *interp (in) Used for
error report-
ing and to
look up a
channel
registered in
it.
char *fileName (in) The name of a
local or net-
work file.
char *mode (in) Specifies how
the file is
to be
accessed.
May have any
of the values
allowed for
the mode
argument to
the Tcl open
command. For
Tcl_OpenCommandChannel,
may be NULL.
int permissions (in) POSIX-style
permission
flags such as
0644. If a
new file is
created,
these permis-
sions will be
set on the
created file.
int argc (in) The number of
elements in
argv.
char **argv (in) Arguments for
constructing
a command
pipeline.
These values
have the same
meaning as
the non-
switch argu-
ments to the
Tcl exec com-
mand.
int flags (in) Specifies the
disposition
of the stdio
handles in
pipeline:
OR-ed combi-
nation of
TCL_STDIN,
TCL_STDOUT,
TCL_STDERR,
and
TCL_ENFORCE_MODE.
If TCL_STDIN
is set, stdin
for the first
child in the
pipe is the
pipe channel,
otherwise it
is the same
as the stan-
dard input of
the invoking
process;
likewise for
TCL_STDOUT
and
TCL_STDERR.
If
TCL_ENFORCE_MODE
is not set,
then the pipe
can redirect
stdio handles
to override
the stdio
handles for
which
TCL_STDIN,
TCL_STDOUT
and
TCL_STDERR
have been
set. If it
is set, then
such redirec-
tions cause
an error. |
ClientData handle (in) ||
Operating |
system |
specific han- |
dle for I/O |
to a file. |
For Unix this |
is a file |
descriptor, |
for Windows |
it is a HAN- |
DLE. |
int readOrWrite (in) ||
OR-ed combi- |
nation of |
TCL_READABLE |
and |
TCL_WRITABLE |
to indicate |
what opera- |
tions are |
valid on han- |
dle. |
char *channelName (in) ||
The name of |
the channel.
int *modePtr (out) Points at an
integer vari-
able that
will receive
an OR-ed com-
bination of
TCL_READABLE
and
TCL_WRITABLE
denoting
whether the
channel is
open for
reading and
writing.
Tcl_Channel channel (in) A Tcl channel
for input or
output. Must
have been the
return value
from a pro-
cedure such
as
Tcl_OpenFileChannel.
Tcl_Obj *readObjPtr (in/out) ||
A pointer to |
a Tcl Object |
in which to |
store the |
characters |
read from the |
channel. |
int charsToRead (in) ||
The number of |
characters to |
read from the |
channel. If |
the channel's |
encoding is |
binary, this |
is equivalent |
to the number |
of bytes to |
read from the |
channel. |
int appendFlag (in) ||
If non-zero, |
data read |
from the |
channel will |
be appended |
to the |
object. Oth- |
erwise, the |
data will |
replace the |
existing con- |
tents of the |
object. |
char *readBuf (out) ||
A buffer in |
which to |
store the |
bytes read |
from the |
channel. |
int bytesToRead (in) ||
The number of |
bytes to read |
from the |
channel. The |
buffer read- |
Buf must be |
large enough |
to hold this |
many bytes. |
Tcl_Obj *lineObjPtr (in/out) ||
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. |
Tcl_DString *lineRead (in/out) ||
A pointer to |
a Tcl dynamic |
string in |
which to |
store the |
line read |
from the |
channel. |
Must have |
been initial- |
ized by the |
caller. The |
line read |
will be |
appended to |
any data |
already in |
the dynamic |
string. |
Tcl_Obj *writeObjPtr (in) ||
A pointer to |
a Tcl Object |
whose con- |
tents will be |
output to the |
channel. |
CONST char *charBuf (in) ||
A buffer con- |
taining the |
characters to |
output to the |
channel. |
char *byteBuf (in) ||
A buffer con- |
taining the |
bytes to out- |
put to the |
channel. |
int bytesToWrite (in) ||
The number of |
bytes to con- |
sume from |
charBuf or |
byteBuf and |
output to the |
channel.
int offset (in) How far to
move the
access point
in the chan-
nel at which
the next
input or out-
put operation
will be
applied,
measured in
bytes from
the position
given by
seekMode.
May be either
positive or
negative.
int seekMode (in) Relative to
which point
to seek; used
with offset
to calculate
the new
access point
for the chan-
nel. Legal
values are
SEEK_SET,
SEEK_CUR, and
SEEK_END.
char *optionName (in) The name of
an option
applicable to
this channel,
such as
-blocking.
May have any
of the values
accepted by
the fconfig-
ure command.
Tcl_DString *optionValue (in) Where to
store the
value of an
option or a
list of all
options and
their values.
Must have
been initial-
ized by the
caller.
char *newValue (in) New value for
the option
given by
optionName. |
char *pattern (in) ||
The pattern |
to match on, |
passed to |
Tcl_StringMatch,|
or NULL. |
char *input (in) ||
The input to |
add to a |
channel |
buffer. |
int inputLen (in) ||
Length of the |
input |
int addToEnd (in) ||
Flag indicat- |
ing whether |
the input |
should be |
added to the |
end or begin- |
ning of the |
channel |
buffer.
_________________________________________________________________
DESCRIPTION
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 dev-
ice types. The channel mechanism is extensible to new chan-
nel types, by providing a low level channel driver for the
new type; the channel driver interface is described in the
manual entry for Tcl_CreateChannel. The channel mechanism
provides a buffering scheme modeled after Unix's standard
I/O, and it also allows for nonblocking I/O on channels.
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 Tcl_CreateChannel.
TCL_OPENFILECHANNEL
Tcl_OpenFileChannel opens a file specified by fileName and
returns a channel handle that can be used to perform input
and output on the file. This API is modeled after the fopen
procedure of the Unix standard I/O library. The syntax and
meaning of all arguments is similar to those given in the
Tcl open command when opening a file. If an error occurs
while opening the channel, Tcl_OpenFileChannel returns NULL
and records a POSIX error code that can be retrieved with
Tcl_GetErrno. In addition, if interp is non-NULL,
Tcl_OpenFileChannel leaves an error message in interp's
result after any error.
The newly created channel is not registered in the supplied
interpreter; to register it, use Tcl_RegisterChannel,
described below. If one of the standard channels, stdin,
stdout or stderr was previously closed, the act of creating
the new channel also assigns it as a replacement for the
standard channel.
TCL_OPENCOMMANDCHANNEL
Tcl_OpenCommandChannel provides a C-level interface to the
functions of the exec and open commands. It creates a
sequence of subprocesses specified by the argv and argc
arguments and returns a channel that can be used to communi-
cate with these subprocesses. The flags argument indicates
what sort of communication will exist with the command pipe-
line.
If the TCL_STDIN 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 TCL_STDIN
is not set, then standard input for the first subprocess
will be the same as this application's standard input. If
TCL_STDOUT is set then standard output from the last subpro-
cess can be read from the channel; otherwise it goes to this
application's standard output. If TCL_STDERR is set, stan-
dard 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
TCL_ENFORCE_MODE is not set, then argc and argv can redirect
the stdio handles to override TCL_STDIN, TCL_STDOUT, and
TCL_STDERR; if it is set, then it is an error for argc and
argv to override stdio channels for which TCL_STDIN,
TCL_STDOUT, and TCL_STDERR have been set.
If an error occurs while opening the channel,
Tcl_OpenCommandChannel returns NULL and records a POSIX
error code that can be retrieved with Tcl_GetErrno. In
addition, Tcl_OpenCommandChannel leaves an error message in
the interpreter's result if interp is not NULL.
The newly created channel is not registered in the supplied
interpreter; to register it, use Tcl_RegisterChannel,
described below. If one of the standard channels, stdin,
stdout or stderr was previously closed, the act of creating
the new channel also assigns it as a replacement for the
standard channel.
TCL_MAKEFILECHANNEL
Tcl_MakeFileChannel makes a Tcl_Channel from an existing,
platform-specific, file handle. The newly created channel
is not registered in the supplied interpreter; to register
it, use Tcl_RegisterChannel, described below. If one of the
standard channels, stdin, stdout or stderr was previously
closed, the act of creating the new channel also assigns it
as a replacement for the standard channel.
TCL_GETCHANNEL
Tcl_GetChannel returns a channel given the channelName used
to create it with Tcl_CreateChannel and a pointer to a Tcl
interpreter in interp. If a channel by that name is not
registered in that interpreter, the procedure returns NULL.
If the mode argument is not NULL, it points at an integer
variable that will receive an OR-ed combination of
TCL_READABLE and TCL_WRITABLE describing whether the channel
is open for reading and writing.
Tcl_GetChannelNames and Tcl_GetChannelNamesEx write the
names of the registered channels to the interpreter's result
as a list object. Tcl_GetChannelNamesEx will filter these
names according to the pattern. If pattern is NULL, then it
will not do any filtering. The return value is TCL_OK if no
errors occured writing to the result, otherwise it is
TCL_ERROR, and the error message is left in the
interpreter's result.
TCL_REGISTERCHANNEL
Tcl_RegisterChannel adds a channel to the set of channels
accessible in interp. After this call, Tcl programs execut-
ing in that interpreter can refer to the channel in input or
output operations using the name given in the call to
Tcl_CreateChannel. After this call, the channel becomes the
property of the interpreter, and the caller should not call
Tcl_Close for the channel; the channel will be closed
automatically when it is unregistered from the interpreter.
Code executing outside of any Tcl interpreter can call
Tcl_RegisterChannel with interp as NULL, to indicate that it
wishes to hold a reference to this channel. Subsequently,
the channel can be registered in a Tcl interpreter and it
will only be closed when the matching number of calls to
Tcl_UnregisterChannel have been made. This allows code exe-
cuting outside of any interpreter to safely hold a reference
to a channel that is also registered in a Tcl interpreter.
TCL_UNREGISTERCHANNEL
Tcl_UnregisterChannel removes a channel from the set of
channels accessible in interp. After this call, Tcl programs
will no longer be able to use the channel's name to refer to
the channel in that interpreter. If this operation removed
the last registration of the channel in any interpreter, the
channel is also closed and destroyed.
Code not associated with a Tcl interpreter can call
Tcl_UnregisterChannel with interp as NULL, to indicate to
Tcl that it no longer holds a reference to that channel. If
this is the last reference to the channel, it will now be
closed.
TCL_CLOSE
Tcl_Close destroys the channel channel, which must denote a
currently open channel. The channel should not be registered
in any interpreter when Tcl_Close is called. Buffered output
is flushed to the channel's output device prior to destroy-
ing the channel, and any buffered input is discarded. If
this is a blocking channel, the call does not return until
all buffered data is successfully sent to the channel's out-
put device. If this is a nonblocking channel and there is
buffered output that cannot be written without blocking, the
call returns immediately; output is flushed in the back-
ground and the channel will be closed once all of the
buffered data has been output. In this case errors during
flushing are not reported.
If the channel was closed successfully, Tcl_Close returns
TCL_OK. If an error occurs, Tcl_Close returns TCL_ERROR and
records a POSIX error code that can be retrieved with
Tcl_GetErrno. If the channel is being closed synchronously
and an error occurs during closing of the channel and interp
is not NULL, an error message is left in the interpreter's
result.
Note: it is not safe to call Tcl_Close on a channel that has
been registered using Tcl_RegisterChannel; see the documen-
tation for Tcl_RegisterChannel, above, for details. If the
channel has ever been given as the chan argument in a call
to Tcl_RegisterChannel, you should instead use
Tcl_UnregisterChannel, which will internally call Tcl_Close
when all calls to Tcl_RegisterChannel have been matched by
corresponding calls to Tcl_UnregisterChannel.
TCL_READCHARS AND TCL_READ |
Tcl_ReadChars consumes bytes from channel, converting the |
bytes to UTF-8 based on the channel's encoding and storing |
the produced data in readObjPtr's string representation. |
The return value of Tcl_ReadChars is the number of charac- |
ters, up to charsToRead, that were stored in objPtr. If an |
error occurs while reading, the return value is -1 and |
Tcl_ReadChars records a POSIX error code that can be |
retrieved with Tcl_GetErrno. |
The return value may be smaller than the value to read, |
indicating that less data than requested was available. |
This is called a short read. In blocking mode, this can |
only happen on an end-of-file. In nonblocking mode, a short |
read can also occur if there is not enough input currently |
available: Tcl_ReadChars returns a short count rather than |
waiting for more data. |
If the channel is in blocking mode, a return value of zero |
indicates an end-of-file condition. If the channel is in |
nonblocking mode, a return value of zero indicates either |
that no input is currently available or an end-of-file con- |
dition. Use Tcl_Eof and Tcl_InputBlocked to tell which of |
these conditions actually occurred. |
Tcl_ReadChars translates the various end-of-line representa- |
tions into the canonical \n internal representation accord- |
ing to the current end-of-line recognition mode. End-of- |
line recognition and the various platform-specific modes are |
described in the manual entry for the Tcl fconfigure com- |
mand. |
As a performance optimization, when reading from a channel |
with the encoding binary, the bytes are not converted to |
UTF-8 as they are read. Instead, they are stored in |
readObjPtr's internal representation as a byte-array object. |
The string representation of this object will only be con- |
structed if it is needed (e.g., because of a call to |
Tcl_GetStringFromObj). In this way, byte-oriented data can |
be read from a channel, manipulated by calling |
Tcl_GetByteArrayFromObj and related functions, and then |
written to a channel without the expense of ever converting |
to or from UTF-8. |
Tcl_Read is similar to Tcl_ReadChars, except that it doesn't |
do encoding conversions, regardless of the channel's encod- |
ing. It is deprecated and exists for backwards compatibil- |
ity with non-internationalized Tcl extensions. It consumes |
bytes from channel and stores them in buf, performing end- |
of-line translations on the way. The return value of |
Tcl_Read is the number of bytes, up to toRead, written in |
buf. The buffer produced by Tcl_Read is not NULL ter- |
minated. Its contents are valid from the zeroth position up |
to and excluding the position indicated by the return value. |
TCL_GETSOBJ AND TCL_GETS |
Tcl_GetsObj consumes bytes from channel, converting the |
bytes to UTF-8 based on the channel's encoding, until a full |
line of input has been seen. If the channel's encoding is |
binary, each byte read from the channel is treated as an |
individual Unicode character. All of the characters of the |
line except for the terminating end-of-line character(s) are |
appended to lineObjPtr's string representation. The end- |
of-line character(s) are read and discarded. |
If a line was successfully read, the return value is greater |
than or equal to zero and indicates the number of bytes |
stored in lineObjPtr. If an error occurs, Tcl_GetsObj |
returns -1 and records a POSIX error code that can be |
retrieved with Tcl_GetErrno. Tcl_GetsObj also returns -1 if |
the end of the file is reached; the Tcl_Eof procedure can be |
used to distinguish an error from an end-of-file condition. |
If the channel is in nonblocking mode, the return value can |
also be -1 if no data was available or the data that was |
available did not contain an end-of-line character. When -1 |
is returned, the Tcl_InputBlocked procedure may be invoked |
to determine if the channel is blocked because of input una- |
vailability. |
Tcl_Gets is the same as Tcl_GetsObj except the resulting |
characters are appended to the appended to the dynamic |
string given by dsPtr rather than a Tcl object. |
TCL_UNGETS |
Tcl_Ungets is used to add data to the input queue of a chan- |
nel, at either the head or tail of the queue. Input is a |
pointer to the data that is to be added. InputLen gives the |
length of the input to add. AddAtEnd, in non-zero, indi- |
cates that the data is to be added at the end of queue; oth- |
erwise it will be added at the head of the queue. If chan- |
nel has a "sticky" EOF set, no data will be added to the |
input queue. Tcl_Ungets returns inputLen or -1 if an error |
occurs. |
TCL_WRITECHARS, TCL_WRITEOBJ, AND TCL_WRITE |
Tcl_WriteChars accepts bytesToWrite bytes of character data |
at charBuf. The UTF-8 characters in the buffer are con- |
verted to the channel's encoding and queued for output to |
channel. If bytesToWrite is negative, Tcl_WriteChars |
expects charBuf to be NULL terminated and it outputs every- |
thing up to the NULL. |
Data queued for output may not appear on the output device |
immediately, due to internal buffering. If the data should |
appear immediately, call Tcl_Flush after the call to |
Tcl_WriteChars, or set the -buffering option on the channel |
to none. If you wish the data to appear as soon as a com- |
plete line is accepted for output, set the -buffering option |
on the channel to line mode. |
The return value of Tcl_WriteChars is a count of how many |
bytes were accepted for output to the channel. This is |
either greater than zero to indicate success or -1 to indi- |
cate that an error occurred. If an error occurs, |
Tcl_WriteChars records a POSIX error code that may be |
retrieved with Tcl_GetErrno. |
Newline characters in the output data are translated to |
platform-specific end-of-line sequences according to the |
-translation option for the channel. This is done even if |
the channel has no encoding. |
Tcl_WriteObj is similar to Tcl_WriteChars except it accepts |
a Tcl object whose contents will be output to the channel. |
The UTF-8 characters in writeObjPtr's string representation |
are converted to the channel's encoding and queued for out- |
put to channel. As a performance optimization, when writing |
to a channel with the encoding binary, UTF-8 characters are |
not converted as they are written. Instead, the bytes in |
writeObjPtr's internal representation as a byte-array object |
are written to the channel. The byte-array representation |
of the object will be constructed if it is needed. In this |
way, byte-oriented data can be read from a channel, manipu- |
lated by calling Tcl_GetByteArrayFromObj and related |
functions, and then written to a channel without the expense |
of ever converting to or from UTF-8. |
Tcl_Write is similar to Tcl_WriteChars except that it |
doesn't do encoding conversions, regardless of the channel's |
encoding. It is deprecated and exists for backwards compa- |
tibility with non-internationalized Tcl extensions. It |
accepts bytesToWrite bytes of data at byteBuf and queues |
them for output to channel. If bytesToWrite is negative, |
Tcl_Write expects byteBuf to be NULL terminated and it out- |
puts everything up to the NULL.
TCL_FLUSH
Tcl_Flush causes all of the buffered output data for channel
to be written to its underlying file or device as soon as
possible. If the channel is in blocking mode, the call does
not return until all the buffered data has been sent to the
channel or some error occurred. The call returns immedi-
ately if the channel is nonblocking; it starts a background
flush that will write the buffered data to the channel even-
tually, as fast as the channel is able to absorb it.
The return value is normally TCL_OK. If an error occurs,
Tcl_Flush returns TCL_ERROR and records a POSIX error code
that can be retrieved with Tcl_GetErrno.
TCL_SEEK
Tcl_Seek moves the access point in channel where subsequent
data will be read or written. Buffered output is flushed to
the channel and buffered input is discarded, prior to the
seek operation.
Tcl_Seek normally returns the new access point. If an error
occurs, Tcl_Seek returns -1 and records a POSIX error code
that can be retrieved with Tcl_GetErrno. After an error,
the access point may or may not have been moved.
TCL_TELL
Tcl_Tell returns the current access point for a channel. The
returned value is -1 if the channel does not support seek-
ing.
TCL_GETCHANNELOPTION
Tcl_GetChannelOption retrieves, in dsPtr, the value of one
of the options currently in effect for a channel, or a list
of all options and their values. The channel argument iden-
tifies the channel for which to query an option or retrieve
all options and their values. If optionName is not NULL, it
is the name of the option to query; the option's value is
copied to the Tcl dynamic string denoted by optionValue. If
optionName is NULL, the function stores an alternating list
of option names and their values in optionValue, using a
series of calls to Tcl_DStringAppendElement. The various
preexisting options and their possible values are described
in the manual entry for the Tcl fconfigure command. Other
options can be added by each channel type. These channel
type specific options are described in the manual entry for
the Tcl command that creates a channel of that type; for
example, the additional options for TCP based channels are
described in the manual entry for the Tcl socket command.
The procedure normally returns TCL_OK. If an error occurs,
it returns TCL_ERROR and calls Tcl_SetErrno to store an
appropriate POSIX error code.
TCL_SETCHANNELOPTION
Tcl_SetChannelOption sets a new value for an option on chan-
nel. OptionName is the option to set and newValue is the
value to set. The procedure normally returns TCL_OK. If an
error occurs, it returns TCL_ERROR; in addition, if interp
is non-NULL, Tcl_SetChannelOption leaves an error message in
the interpreter's result.
TCL_EOF
Tcl_Eof returns a nonzero value if channel encountered an
end of file during the last input operation.
TCL_INPUTBLOCKED
Tcl_InputBlocked returns a nonzero value if channel is in
nonblocking mode and the last input operation returned less
data than requested because there was insufficient data
available. The call always returns zero if the channel is
in blocking mode.
TCL_INPUTBUFFERED
Tcl_InputBuffered returns the number of bytes of input
currently buffered in the internal buffers for a channel. If
the channel is not open for reading, this function always
returns zero.
PLATFORM ISSUES |
The handles returned from Tcl_GetChannelHandle depend on the |
platform and the channel type. On Unix platforms, the han- |
dle is always a Unix file descriptor as returned from the |
open system call. On Windows platforms, the handle is a |
file HANDLE when the channel was created with |
Tcl_OpenFileChannel, Tcl_OpenCommandChannel, or |
Tcl_MakeFileChannel. Other channel types may return a dif- |
ferent type of handle on Windows platforms. On the Macin- |
tosh platform, the handle is a file reference number as |
returned from HOpenDF.
SEE ALSO
DString(3), fconfigure(n), filename(n), fopen(2),
Tcl_CreateChannel(3)
KEYWORDS
access point, blocking, buffered I/O, channel, channel
driver, end of file, flush, input, nonblocking, output,
read, seek, write
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