2 * option.h -- helpers for handling options in CoAP PDUs
4 * Copyright (C) 2010-2013 Olaf Bergmann <bergmann@tzi.org>
6 * This file is part of the CoAP library libcoap. Please see
7 * README for terms of use.
12 * @brief helpers for handling options in CoAP PDUs
26 * Use byte-oriented access methods here because sliding a complex
27 * struct coap_opt_t over the data buffer may cause bus error on
30 typedef unsigned char coap_opt_t;
31 #define PCHAR(p) ((coap_opt_t *)(p))
33 /** Representation of CoAP options. */
41 * Parses the option pointed to by @p opt into @p result. This
42 * function returns the number of bytes that have been parsed, or @c 0
43 * on error. An error is signaled when illegal delta or length values
44 * are encountered or when option parsing would result in reading past
45 * the option (i.e. beyond opt + length).
47 * @param opt The beginning of the option to parse.
48 * @param length The maximum length of @p opt.
49 * @param result A pointer to the coap_option_t structure that is
50 * filled with actual values iff coap_opt_parse() > 0.
51 * @return The number of bytes parsed or @c 0 on error.
53 size_t coap_opt_parse(const coap_opt_t *opt, size_t length,
54 coap_option_t *result);
57 * Returns the size of the given option, taking into account a
58 * possible option jump.
60 * @param opt An option jump or the beginning of the option.
61 * @return The number of bytes between @p opt and the end of
62 * the option starting at @p opt. In case of an error,
63 * this function returns @c 0 as options need at least
64 * one byte storage space.
66 size_t coap_opt_size(const coap_opt_t *opt);
68 /** @deprecated { Use coap_opt_size() instead. } */
69 #define COAP_OPT_SIZE(opt) coap_opt_size(opt)
72 * Calculates the beginning of the PDU's option section.
74 * @param pdu The PDU containing the options.
75 * @return A pointer to the first option if available, or @c NULL otherwise.
77 coap_opt_t *options_start(coap_pdu_t *pdu);
80 * Interprets @p opt as pointer to a CoAP option and advances to
81 * the next byte past this option.
84 #define options_next(opt) \
85 ((coap_opt_t *)((unsigned char *)(opt) + COAP_OPT_SIZE(opt)))
88 * @defgroup opt_filter Option Filters
93 * Fixed-size bit-vector we use for option filtering. It is large
94 * enough to hold the highest option number known at build time (20 in
97 typedef unsigned char coap_opt_filter_t[(COAP_MAX_OPT >> 3) + 1];
99 /** Pre-defined filter that includes all options. */
100 #define COAP_OPT_ALL NULL
103 * Clears filter @p f.
105 * @param f The filter to clear.
108 coap_option_filter_clear(coap_opt_filter_t f) {
109 memset(f, 0, sizeof(coap_opt_filter_t));
113 * Sets the corresponding bit for @p type in @p filter. This function
114 * returns @c 1 if bit was set or @c -1 on error (i.e. when the given
115 * type does not fit in the filter).
117 * @param filter The filter object to change.
118 * @param type The type for which the bit should be set.
120 * @return @c 1 if bit was set, @c -1 otherwise.
123 coap_option_setb(coap_opt_filter_t filter, unsigned short type) {
124 return bits_setb((uint8_t *)filter, sizeof(coap_opt_filter_t), type);
128 * Sets the entire range of vendor specific options in the filter
131 coap_option_setbVendor(coap_opt_filter_t filter)
133 if ((COAP_VENDOR_OPT_START >> 3) > sizeof(coap_opt_filter_t))
137 memset((uint8_t *)filter + (COAP_VENDOR_OPT_START >> 3), 0xFF,
138 sizeof(coap_opt_filter_t) - (COAP_VENDOR_OPT_START >> 3));
143 * Clears the corresponding bit for @p type in @p filter. This function
144 * returns @c 1 if bit was cleared or @c -1 on error (i.e. when the given
145 * type does not fit in the filter).
147 * @param filter The filter object to change.
148 * @param type The type for which the bit should be cleared.
150 * @return @c 1 if bit was set, @c -1 otherwise.
153 coap_option_clrb(coap_opt_filter_t filter, unsigned short type) {
154 return bits_clrb((uint8_t *)filter, sizeof(coap_opt_filter_t), type);
158 * Gets the corresponding bit for @p type in @p filter. This function
159 * returns @c 1 if the bit is set @c 0 if not, or @c -1 on error (i.e.
160 * when the given type does not fit in the filter).
162 * @param filter The filter object to read bit from..
163 * @param type The type for which the bit should be read.
165 * @return @c 1 if bit was set, @c 0 if not, @c -1 on error.
168 coap_option_getb(const coap_opt_filter_t filter, unsigned short type) {
169 return bits_getb((uint8_t *)filter, sizeof(coap_opt_filter_t), type);
173 * Iterator to run through PDU options. This object must be
174 * initialized with coap_option_iterator_init(). Call
175 * coap_option_next() to walk through the list of options until
176 * coap_option_next() returns @c NULL.
179 * coap_opt_t *option;
180 * coap_opt_iterator_t opt_iter;
181 * coap_option_iterator_init(pdu, &opt_iter, COAP_OPT_ALL);
183 * while ((option = coap_option_next(&opt_iter))) {
184 * ... do something with option ...
189 size_t length; /**< remaining length of PDU */
190 unsigned short type; /**< decoded option type */
191 unsigned int bad:1; /**< iterator object is ok if not set */
192 unsigned int filtered:1; /**< denotes whether or not filter is used */
193 coap_opt_t *next_option; /**< pointer to the unparsed next option */
194 coap_opt_filter_t filter; /**< option filter */
195 } coap_opt_iterator_t;
198 * Initializes the given option iterator @p oi to point to the
199 * beginning of the @p pdu's option list. This function returns @p oi
200 * on success, @c NULL otherwise (i.e. when no options exist).
201 * Note that a length check on the option list must be performed before
202 * coap_option_iterator_init() is called.
204 * @param pdu The PDU the options of which should be walked through.
205 * @param oi An iterator object that will be initilized.
206 * @param filter An optional option type filter.
207 * With @p type != @c COAP_OPT_ALL, coap_option_next()
208 * will return only options matching this bitmask.
209 * Fence-post options @c 14, @c 28, @c 42, ... are always
212 * @return The iterator object @p oi on success, @c NULL otherwise.
214 coap_opt_iterator_t *coap_option_iterator_init(coap_pdu_t *pdu,
215 coap_opt_iterator_t *oi, const coap_opt_filter_t filter);
218 * Updates the iterator @p oi to point to the next option. This
219 * function returns a pointer to that option or @c NULL if no more
220 * options exist. The contents of @p oi will be updated. In
221 * particular, @c oi->n specifies the current option's ordinal number
222 * (counted from @c 1), @c oi->type is the option's type code, and @c
223 * oi->option points to the beginning of the current option
224 * itself. When advanced past the last option, @c oi->option will be
227 * Note that options are skipped whose corresponding bits in the
228 * filter specified with coap_option_iterator_init() are @c 0. Options
229 * with type codes that do not fit in this filter hence will always be
232 * @param oi The option iterator to update.
234 * @return The next option or @c NULL if no more options exist.
236 coap_opt_t *coap_option_next(coap_opt_iterator_t *oi);
239 * Retrieves the first option of type @p type from @p pdu. @p oi must
240 * point to a coap_opt_iterator_t object that will be initialized by
241 * this function to filter only options with code @p type. This
242 * function returns the first option with this type, or @c NULL if not
245 * @param pdu The PDU to parse for options.
246 * @param type The option type code to search for.
247 * @param oi An iterator object to use.
249 * @return A pointer to the first option of type @p type, or @c NULL
252 coap_opt_t *coap_check_option(coap_pdu_t *pdu,
254 coap_opt_iterator_t *oi);
257 * Encodes the given delta and length values into @p opt. This
258 * function returns the number of bytes that were required to encode
259 * @p delta and @p length or @c 0 on error. Note that the result
260 * indicates by how many bytes @p opt must be advanced to encode the
263 * @param opt The option buffer space where @p delta and @p length are
265 * @param maxlen The maximum length of @p opt
266 * @param delta The actual delta value to encode.
267 * @param length The actual length value to encode.
268 * @return The number of bytes used or @c 0 on error.
270 size_t coap_opt_setheader(coap_opt_t *opt, size_t maxlen,
271 unsigned short delta, size_t length);
274 * Encodes option with given @p delta into @p opt. This function returns
275 * the number of bytes written to @p opt or @c 0 on error. This happens
276 * especially when @p opt does not provide sufficient space to store
277 * the option value, delta, and option jumps when required.
279 * @param opt The option buffer space where @p val is written
280 * @param n Maximum length of @p opt.
281 * @param delta The option delta.
282 * @param val The option value to copy into @p opt.
283 * @param len The actual length of @p val.
284 * @return The number of bytes that have been written to @p opt or
285 * @c 0 on error. The return value will always be less than @p n.
287 size_t coap_opt_encode(coap_opt_t *opt, size_t n, unsigned short delta,
288 const unsigned char *val, size_t length);
291 * Decodes the delta value of the next option. This function returns
292 * the number of bytes read or @c 0 on error. The caller of this
293 * function must ensure that it does not read over the boundaries
294 * of @p opt (e.g. by calling coap_opt_check_delta().
296 * @param opt The option to examine
297 * @return The number of bytes read or @c 0 on error.
299 unsigned short coap_opt_delta(const coap_opt_t *opt);
301 /** @deprecated { Use coap_opt_delta() instead. } */
302 #define COAP_OPT_DELTA(opt) coap_opt_delta(opt)
304 /** @deprecated { Use coap_opt_encode() instead. } */
305 #define COAP_OPT_SETDELTA(opt,val) \
306 coap_opt_encode((opt), COAP_MAX_PDU_SIZE, (val), NULL, 0)
309 * Returns the length of the given option. @p opt must point to an
310 * option jump or the beginning of the option. This function returns
311 * @c 0 when @p opt is not an option or the actual length of @p opt
312 * (which can be @c 0 as well).
314 * @note {The rationale for using @c 0 in case of an error is that in
315 * most contexts, the result of this function is used to skip the next
316 * coap_opt_length() bytes. }
318 * @param opt The option whose length should be returned.
319 * @return The option's length or @c 0 when undefined.
321 unsigned short coap_opt_length(const coap_opt_t *opt);
323 /** @deprecated { Use coap_opt_length() instead. } */
324 #define COAP_OPT_LENGTH(opt) coap_opt_length(opt)
327 * Returns a pointer to the value of the given option. @p opt must
328 * point to an option jump or the beginning of the option. This
329 * function returns @c NULL if @p opt is not a valid option.
331 * @param opt The option whose value should be returned.
332 * @return A pointer to the option value or @c NULL on error.
334 unsigned char *coap_opt_value(coap_opt_t *opt);
336 /** @deprecated { Use coap_opt_value() instead. } */
337 #define COAP_OPT_VALUE(opt) coap_opt_value((coap_opt_t *)opt)
345 #endif /* _OPTION_H_ */