ttmedia_load(library call) ttmedia_load(library call)
NAMEttmedia_load — send a Display, Edit or Compose request
SYNOPSIS
#include <Tt/tttk.h>
Tt_message ttmedia_load(
Tt_message context,
Ttmedia_load_msg_cb cb,
void *clientdata,
Tttk_op op,
const char *media_type,
const unsigned char *contents,
int len,
const char *file,
const char *docname,
int send);
DESCRIPTION
The ttmedia_load function is used to create and optionally send a Media
Exchange request to display, edit or compose a document.
The cb argument will be passed clientdata when the reply is received,
or when intermediate versions of the document are checkpointed through
Deposit requests. The op argument must be one of TTME_DISPLAY,
TTME_EDIT or TTME_COMPOSE. The media_type argument names the data for‐
mat of the document, and is usually the primary determinant of which
application will be chosen to handle the request. The contents and len
arguments specify the document; if they are NULL and zero, respec‐
tively, and file is not NULL, then the document is assumed to be con‐
tained in file. If docname is not NULL, then ttmedia_load uses it as
the title of the document. If send is True, the message is sent before
being returned.
The context argument describes the environment to use. If context is
not zero, messages created by ttmedia_load inherit from context all
contexts whose slotname begins with the characters ENV_.
The Ttmedia_load_msg_cb argument is a callback defined as:
Tt_message (*Ttmedia_load_msg_cb)(Tt_message msg,
void *clientdata),
Tttk_op op,
unsigned char *contents,
int len,
char *file);
The msg argument is the reply to the load request, or a Deposit request
with a messageID argument naming the identifier (see tt_message_id(3))
of the load request. In the latter case, the client program becomes
responsible for either failing or replying to the request. In either
case, msg should be destroyed after being processed.
The op argument is the op of msg. It must be either TTME_DEPOSIT or the
op passed to ttmedia_load(3).
The contents, len and file arguments represent the contents of the
arriving document. If len is zero, then the document is contained in
file. If contents or file are non- NULL, they can be freed using
tt_free.
The clientdata argument is the clientdata passed to ttmedia_load.
RETURN VALUE
Upon successful completion, the ttmedia_load function returns the
request it was asked to build; otherwise, it returns an error pointer.
The application can use tt_ptr_error(3) to extract one of the following
Tt_status values from the returned handle:
TT_ERR_NOMEM
There is insufficient memory available to perform the func‐
tion.
TT_ERR_NOMP
The ttsession(1) process is not running and the ToolTalk ser‐
vice cannot restart it.
TT_ERR_OVERFLOW
The ToolTalk service has more active messages than it can
handle. (The maximum number of active messages is implemen‐
tation specific, but is at least 2000.)
TT_ERR_PROCID
The specified process identifier is out of date or invalid.
APPLICATION USAGE
After the request created by ttmedia_load is sent, the application will
probably want to use ttdt_subcontract_manage immediately afterwards to
manage the standard interactions with the handler of the request.
A Ttmedia_load_msg_cb callback should return NULL if it processes msg
successfully, or a tt_error_pointer cast to Tt_message if processing
results in an error. It should return the msg if it does not consume
it, in which case the ToolTalk service will pass TT_CALLBACK_CONTINUE
down the call stack, so that msg will be offered to other callbacks or
(more likely) be returned from tt_message_receive(3). Applications will
rarely want msg to get processed by other callbacks or in the main
event loop.
EXAMPLES
This is the typical algorithm of a Ttmedia_load_msg_cb:
Tt_message
myLoadMsgCB(Tt_message msg,
void *clientData,
Tttk_op op,
unsigned char *contents,
int len,
char *file)
{
if (len > 0) {
/* Replace data with len bytes in contents */
} else if (file != 0) {
/* Replace data with data read from file */
}
if (op == TTME_DEPOSIT) {
tt_message_reply(msg);
}
tttk_message_destroy(msg);
return 0;
}
SEE ALSO
Tt/tttk.h - Tttttk(5), ttmedia_load_reply(3), ttmedia_ptype_declare(3),
ttmedia_Deposit(3), tt_free(3), tt_message_receive(3).
ttmedia_load(library call)
