1xpagetfd(3) SAORD Documentation xpagetfd(3)
2
6 XPAGetFd: retrieve data from one or more XPA servers and write to files
7
9 #include <xpa.h>
10 int XPAGetFd(XPA xpa,
12 char *template, char *paramlist, char *mode,
13 int *fds, char **names, char **messages, int n);
14
16 Retrieve data from one or more XPA servers whose class:name identifier
17 matches the specified template and write it to files associated with
18 one or more standard I/O fds (i.e, handles returned by open()).
19 A template of the form "class1:name1" is sent to the XPA name server,
21 which returns a list of at most ABS(n) matching XPA servers. A
22 connection is established with each of these servers and the paramlist
23 string is passed to the server as the data transfer request is
24 initiated. If an XPA struct is passed to the call, then the persistent
25 connections are updated as described above. Otherwise, temporary
26 connections are made to the servers (which will be closed when the call
27 completes).
28 The XPAGetFd() routine then retrieves data from the XPA servers, and
30 write these data to the fds associated with one or more fds (i.e.,
31 results from open). Is n is positive, then there will be n fds and the
32 data from each server will be sent to a separate fd. If n is negative,
33 then there is only 1 fd and all data is sent to this single fd. (The
34 latter is how xpaget is implemented.)
35 A string containing the class:name and ip:port is stored in the name
37 array. If a given server returned an error or the server callback
38 sends a message back to the client, then the message will be stored in
39 the associated element of the messages array. NB: if specified, the
40 name and messages arrays must be of size n or greater.
41 The returned message string will be of the form:
43 XPA$ERROR error-message (class:name ip:port)
45 or
47 XPA$MESSAGE message (class:name ip:port)
49 Note that when there is an error stored in an messages entry, the
51 corresponding bufs and lens entry may or may not be NULL and 0
52 (respectively), depending on the particularities of the server.
53 The return value will contain the actual number of servers that were
55 processed. This value thus will hold the number of valid entries in
56 the bufs, lens, names, and messages arrays, and can be used to loop
57 through these arrays. In names and/or messages is NULL, no information
58 is passed back in that array.
59 The mode string is of the form: "key1=value1,key2=value2,..." The
61 following keywords are recognized:
62 key value default explanation
64 ------ -------- -------- -----------
65 ack true/false true if false, don't wait for ack from server (after callback completes)
66 The ack keyword is not very useful, since the server completes the
68 callback in order to return the data anyway. It is here for completion
69 (and perhaps for future usefulness).
70 Example:
72 #include <xpa.h>
74 #define NXPA 10
75 int i, got;
76 int fds[NXPA];
77 char *names[NXPA];
78 char *messages[NXPA];
79 for(i=0; i<NXPA; i++)
80 fds[i] = open(...);
81 got = XPAGetFd(NULL, "ds9", "file", NULL, fds, names, messages, NXPA);
82 for(i=0; i<got; i++){
83 if( messages[i] != NULL ){
84 /* error processing */
85 fprintf(stderr, "ERROR: %s (%s)\n", messages[i], names[i]);
86 }
87 if( names[i] )
88 free(names[i]);
89 if( messages[i] )
90 free(messages[i]);
91 }
92
94 See xpa(n) for a list of XPA help pages
95version 2.1.15 July 23, 2013 xpagetfd(3)