coap_add_attr(3)

1COAP_ATTRIBUTE(3)               libcoap Manual               COAP_ATTRIBUTE(3)
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NAME

6       coap_attribute, coap_add_attr, coap_find_attr - Work with CoAP
7       attributes
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SYNOPSIS

10       #include <coap2/coap.h>
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12       coap_attr_t *coap_add_attr(coap_resource_t *resource, coap_str_const_t
13       *name, coap_str_const_t *value, int flags);
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15       coap_attr_t *coap_find_attr(coap_resource_t *resource, coap_str_const_t
16       *name);
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18       Link with -lcoap-2, -lcoap-2-gnutls, -lcoap-2-openssl or
19       -lcoap-2-tinydtls depending on your (D)TLS library type.
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DESCRIPTION

22       CoAP Resources on a CoAP Server need to be created, updated etc. The
23       URI in the request packet defines the resource to work with, with
24       possibly the Query referring to a sub-resource. When resources are
25       configured on the CoAP server, the URI to match against is specified.
26       Callback Handlers are then added to the resource to handle the
27       different request methods. Adding Attributes allows textual information
28       to be added to the resource which can then be reported back to any
29       client doing a "GET .well-known/core" request.
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31       Attributes are automatically freed when a Resource is deleted.
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33       The coap_add_attr() function registers a new attribute called name for
34       the resource. The value of the attribute is value.
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36       flags can be one or more of the following, which, if set, defines what
37       is to be internally freed off when the attribute is deleted with
38       coap_delete_resource().
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41       COAP_ATTR_FLAGS_RELEASE_NAME    Free off name when
42                                       attribute is deleted with
43                                       coap_delete_resource().
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45       COAP_ATTR_FLAGS_RELEASE_VALUE   Free off value when
46                                       attribute is deleted with
47                                       coap_delete_resource().
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50       The coap_find_attr() function returns the attribute with the name, if
51       found, associated with resource.
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RETURN VALUES

54       coap_add_attr() function return a pointer to the attribute that was
55       created or NULL if there is a malloc failure.
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57       coap_find_attr() function returns a pointer to the first matching
58       attribute or NULL if the name was not found.
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EXAMPLE

61       Initialize Resources
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63           #include <coap2/coap.h>
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65           static void
66           init_resources(coap_context_t *ctx) {
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68             coap_resource_t *r;
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70             /* Create a resource to return general information */
71             r = coap_resource_init(NULL, 0);
72             coap_register_handler(r, COAP_REQUEST_GET, hnd_get_index);
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74             /* Document resource for .well-known/core request */
75             coap_add_attr(r, coap_make_str_const("ct"), coap_make_str_const("0"), 0);
76             coap_add_attr(r, coap_make_str_const("title"),
77                           coap_make_str_const("\"General Info\""), 0);
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79             coap_add_resource(ctx, r);
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81             /* Create a resource to return return or update time */
82             r = coap_resource_init(coap_make_str_const("time"),
83                                    COAP_RESOURCE_FLAGS_NOTIFY_CON);
84             coap_resource_set_get_observable(r, 1);
85             coap_register_handler(r, COAP_REQUEST_GET, hnd_get_time);
86             coap_register_handler(r, COAP_REQUEST_PUT, hnd_put_time);
87             coap_register_handler(r, COAP_REQUEST_DELETE, hnd_delete_time);
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89             /* Document resource for .well-known/core request */
90             coap_add_attr(r, coap_make_str_const("ct"), coap_make_str_const("0"), 0);
91             coap_add_attr(r, coap_make_str_const("title"),
92                           coap_make_str_const("\"Internal Clock\""), 0);
93             coap_add_attr(r, coap_make_str_const("rt"), coap_make_str_const("\"secs\""),
94                           0);
95             coap_add_attr(r, coap_make_str_const("if"), coap_make_str_const("\"clock\""),
96                           0);
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98             coap_add_resource(ctx, r);
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100           }
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FURTHER INFORMATION

106       See RFC7252 ‘The Constrained Application Protocol (CoAP)’ for further
107       information.
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BUGS

110       Please report bugs on the mailing list for libcoap:
111       libcoap-developers@lists.sourceforge.net
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AUTHORS

114       The libcoap project <libcoap-developers@lists.sourceforge.net>
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118coap_attribute 4.2.1              07/28/2020                 COAP_ATTRIBUTE(3)