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6 XPAGet: retrieve data from one or more XPA servers
7
9 #include <xpa.h>
10 int XPAGet(XPA xpa,
12 char *template, char *paramlist, char *mode,
13 char **bufs, size_t *lens, char **names, char **messages,
14 int n);
15
17 Retrieve data from one or more XPA servers whose class:name identifier
18 matches the specified template.
19 A template of the form "class1:name1" is sent to the XPA name server,
21 which returns a list of at most n matching XPA servers. A connection
22 is established with each of these servers and the paramlist string is
23 passed to the server as the data transfer request is initiated. If an
24 XPA struct is passed to the call, then the persistent connections are
25 updated as described above. Otherwise, temporary connections are made
26 to the servers (which will be closed when the call completes).
27 The XPAGet() routine then retrieves data from at most n XPA servers,
29 places these data into n allocated buffers and places the buffer
30 pointers in the bufs array. The length of each buffer is stored in the
31 lens array. A string containing the class:name and ip:port is stored in
32 the name array. If a given server returned an error or the server
33 callback sends a message back to the client, then the message will be
34 stored in the associated element of the messages array. NB: if
35 specified, the name and messages arrays must be of size n or greater.
36 The returned message string will be of the form:
38 XPA$ERROR error-message (class:name ip:port)
40 or
42 XPA$MESSAGE message (class:name ip:port)
44 Note that when there is an error stored in an messages entry, the
46 corresponding bufs and lens entry may or may not be NULL and 0
47 (respectively), depending on the particularities of the server.
48 The return value will contain the actual number of servers that were
50 processed. This value thus will hold the number of valid entries in
51 the bufs, lens, names, and messages arrays, and can be used to loop
52 through these arrays. In names and/or messages is NULL, no information
53 is passed back in that array.
54 The bufs, names, and messages arrays should be freed upon completion
56 (if they are not NULL);
57 The mode string is of the form: "key1=value1,key2=value2,..." The
59 following keywords are recognized:
60 key value default explanation
62 ------ -------- -------- -----------
63 ack true/false true if false, don't wait for ack from server (after callback completes)
64 doxpa true/false true client processes xpa requests
65 The ack keyword is not very useful, since the server completes the
67 callback in order to return the data anyway. It is here for completion
68 (and perhaps for future usefulness).
69 Normally, an XPA client will process incoming XPA server requests while
71 awaiting the completion of the client request. Setting this variable
72 to "false" will prevent XPA server requests from being processed by the
73 client.
74 Example:
76 #include <xpa.h>
78 #define NXPA 10
80 int i, got;
81 size_t lens[NXPA];
82 char *bufs[NXPA];
83 char *names[NXPA];
84 char *messages[NXPA];
85 got = XPAGet(NULL, "ds9", "file", NULL, bufs, lens, names, messages,
86 NXPA);
87 for(i=0; i<got; i++){
88 if( messages[i] == NULL ){
89 /* process buf contents */
90 ProcessImage(bufs[i], ...);
91 free(bufs[i]);
92 }
93 else{
94 /* error processing */
95 fprintf(stderr, "ERROR: %s (%s)\n", messages[i], names[i]);
96 }
97 if( names[i] )
98 free(names[i]);
99 if( messages[i] )
100 free(messages[i]);
101 }
102
104 See xpa(n) for a list of XPA help pages
105version 2.1.15 July 23, 2013 xpaget(3)