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| 59.1 XEmacs ToolTalk API Summary | ||
| 59.2 Sending Messages | ||
| 59.3 Receiving Messages |
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The XEmacs Lisp interface to ToolTalk is similar, at least in spirit, to the standard C ToolTalk API. Only the message and pattern parts of the API are supported at present; more of the API could be added if needed. The Lisp interface departs from the C API in a few ways:
'TT_SESSION. This
simplifies building lists that represent messages and patterns.
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| 59.2.1 Example of Sending Messages | ||
| 59.2.2 Elisp Interface for Sending Messages |
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Here’s a simple example that sends a query to another application and then displays its reply. Both the query and the reply are stored in the first argument of the message.
(defun tooltalk-random-query-handler (msg)
(let ((state (get-tooltalk-message-attribute msg 'state)))
(cond
((eq state 'TT_HANDLED)
(message (get-tooltalk-message-attribute msg arg_val 0)))
((memq state '(TT_FAILED TT_REJECTED))
(message "Random query turns up nothing")))))
(defvar random-query-message
'( class TT_REQUEST
scope TT_SESSION
address TT_PROCEDURE
op "random-query"
args '((TT_INOUT "?" "string"))
callback tooltalk-random-query-handler))
(let ((m (make-tooltalk-message random-query-message)))
(send-tooltalk-message m))
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Create a ToolTalk message and initialize its attributes. The value of attributes must be a list of alternating keyword/values, where keywords are symbols that name valid message attributes. For example:
(make-tooltalk-message
'(class TT_NOTICE
scope TT_SESSION
address TT_PROCEDURE
op "do-something"
args ("arg1" 12345 (TT_INOUT "arg3" "string"))))
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Values must always be strings, integers, or symbols that represent
ToolTalk constants. Attribute names are the same as those supported by
set-tooltalk-message-attribute, plus args.
The value of args should be a list of message arguments where
each message argument has the following form:
‘(mode [value [type]])’ or just ‘value’
Where mode is one of TT_IN, TT_OUT, or
TT_INOUT and type is a string. If type isn’t
specified then int is used if value is a number; otherwise
string is used. If type is string then value
is converted to a string (if it isn’t a string already) with
prin1-to-string. If only a value is specified then mode
defaults to TT_IN. If mode is TT_OUT then
value and type don’t need to be specified. You can find out
more about the semantics and uses of ToolTalk message arguments in
chapter 4 of the ToolTalk Programmer’s Guide.
Send the message on its way. Once the message has been sent it’s almost
always a good idea to get rid of it with
destroy-tooltalk-message.
Send a reply to this message. The second argument can be reply,
reject or fail; the default is reply. Before
sending a reply, all message arguments whose mode is TT_INOUT or
TT_OUT should have been filled in—see
set-tooltalk-message-attribute.
Returns the indicated ToolTalk message attribute. Attributes are
identified by symbols with the same name (underscores and all) as the
suffix of the ToolTalk ‘tt_message_<attribute>’ function that
extracts the value. String attribute values are copied and enumerated
type values (except disposition) are converted to symbols;
e.g. ‘TT_HANDLER’ is 'TT_HANDLER, ‘uid’ and ‘gid’
are represented by fixnums (small integers), ‘opnum’ is converted
to a string, and ‘disposition’ is converted to a fixnum. We
convert ‘opnum’ (a C int) to a string (e.g. 123 ⇒
"123") because there’s no guarantee that opnums will fit within
the range of XEmacs Lisp integers.
[TBD] Use the plist attribute instead of C API user
attribute for user-defined message data. To retrieve the value of a
message property, specify the indicator for argn. For example, to
get the value of a property called rflag, use
(get-tooltalk-message-attribute msg 'plist 'rflag) |
To get the value of a message argument use one of the arg_val
(strings), arg_ival (integers), or arg_bval (strings with
embedded nulls), attributes. For example, to get the integer value of
the third argument:
(get-tooltalk-message-attribute msg 'arg_ival 2) |
As you can see, argument numbers are zero-based. The type of each
arguments can be retrieved with the arg_type attribute; however
ToolTalk doesn’t define any semantics for the string value of
arg_type. Conventionally string is used for strings and
int for 32 bit integers. Note that XEmacs Lisp stores the lengths
of strings explicitly (unlike C) so treating the value returned by
arg_bval like a string is fine.
Initialize one ToolTalk message attribute.
Attribute names and values are the same as for
get-tooltalk-message-attribute. A property list is provided for
user data (instead of the user message attribute); see
get-tooltalk-message-attribute.
Callbacks are handled slightly differently than in the C ToolTalk API.
The value of callback should be the name of a function of one
argument. It will be called each time the state of the message changes.
This is usually used to notice when the message’s state has changed to
TT_HANDLED (or TT_FAILED), so that reply argument values
can be used.
If one of the argument attributes is specified as arg_val,
arg_ival, or arg_bval, then argn must be the
number of an already created argument. Arguments can be added to a
message with add-tooltalk-message-arg.
Append one new argument to the message. mode must be one of
TT_IN, TT_INOUT, or TT_OUT, type must be a
string, and value can be a string or an integer. ToolTalk doesn’t
define any semantics for type, so only the participants in the
protocol you’re using need to agree what types mean (if anything).
Conventionally string is used for strings and int for 32
bit integers. Arguments can initialized by providing a value or with
set-tooltalk-message-attribute; the latter is necessary if you
want to initialize the argument with a string that can contain embedded
nulls (use arg_bval).
Create a new ToolTalk message. The message’s session attribute is
initialized to the default session. Other attributes can be initialized
with set-tooltalk-message-attribute.
make-tooltalk-message is the preferred way to create and
initialize a message.
Optional arg no-callback says don’t add a C-level callback at all.
Normally don’t do that; just don’t specify the Lisp callback when
calling make-tooltalk-message.
Apply ‘tt_message_destroy’ to the message. It’s not necessary to destroy messages after they’ve been processed by a message or pattern callback, the Lisp/ToolTalk callback machinery does this for you.
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| 59.3.1 Example of Receiving Messages | ||
| 59.3.2 Elisp Interface for Receiving Messages |
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Here’s a simple example of a handler for a message that tells XEmacs to display a string in the mini-buffer area. The message operation is called ‘emacs-display-string’. Its first (0th) argument is the string to display.
(defun tooltalk-display-string-handler (msg)
(message (get-tooltalk-message-attribute msg 'arg_val 0)))
(defvar display-string-pattern
'(category TT_HANDLE
scope TT_SESSION
op "emacs-display-string"
callback tooltalk-display-string-handler))
(let ((p (make-tooltalk-pattern display-string-pattern)))
(register-tooltalk-pattern p))
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