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
22 * Use byte-oriented access methods here because sliding a complex
23 * struct coap_opt_t over the data buffer may cause bus error on
26 typedef unsigned char coap_opt_t;
27 #define PCHAR(p) ((coap_opt_t *)(p))
29 /** Representation of CoAP options. */
37 * Parses the option pointed to by @p opt into @p result. This
38 * function returns the number of bytes that have been parsed, or @c 0
39 * on error. An error is signaled when illegal delta or length values
40 * are encountered or when option parsing would result in reading past
41 * the option (i.e. beyond opt + length).
43 * @param opt The beginning of the option to parse.
44 * @param length The maximum length of @p opt.
45 * @param result A pointer to the coap_option_t structure that is
46 * filled with actual values iff coap_opt_parse() > 0.
47 * @return The number of bytes parsed or @c 0 on error.
49 size_t coap_opt_parse(const coap_opt_t *opt, size_t length,
50 coap_option_t *result);
53 * Returns the size of the given option, taking into account a
54 * possible option jump.
56 * @param opt An option jump or the beginning of the option.
57 * @return The number of bytes between @p opt and the end of
58 * the option starting at @p opt. In case of an error,
59 * this function returns @c 0 as options need at least
60 * one byte storage space.
62 size_t coap_opt_size(const coap_opt_t *opt);
64 /** @deprecated { Use coap_opt_size() instead. } */
65 #define COAP_OPT_SIZE(opt) coap_opt_size(opt)
68 * Calculates the beginning of the PDU's option section.
70 * @param pdu The PDU containing the options.
71 * @return A pointer to the first option if available, or @c NULL otherwise.
73 coap_opt_t *options_start(coap_pdu_t *pdu);
76 * Interprets @p opt as pointer to a CoAP option and advances to
77 * the next byte past this option.
80 #define options_next(opt) \
81 ((coap_opt_t *)((unsigned char *)(opt) + COAP_OPT_SIZE(opt)))
84 * @defgroup opt_filter Option Filters
89 * Fixed-size bit-vector we use for option filtering. It is large
90 * enough to hold the highest option number known at build time (20 in
93 typedef unsigned char coap_opt_filter_t[(COAP_MAX_OPT >> 3) + 1];
95 /** Pre-defined filter that includes all options. */
96 #define COAP_OPT_ALL NULL
101 * @param f The filter to clear.
104 coap_option_filter_clear(coap_opt_filter_t f) {
105 memset(f, 0, sizeof(coap_opt_filter_t));
109 * Sets the corresponding bit for @p type in @p filter. This function
110 * returns @c 1 if bit was set or @c -1 on error (i.e. when the given
111 * type does not fit in the filter).
113 * @param filter The filter object to change.
114 * @param type The type for which the bit should be set.
116 * @return @c 1 if bit was set, @c -1 otherwise.
119 coap_option_setb(coap_opt_filter_t filter, unsigned short type) {
120 return bits_setb((uint8_t *)filter, sizeof(coap_opt_filter_t), type);
124 * Clears the corresponding bit for @p type in @p filter. This function
125 * returns @c 1 if bit was cleared or @c -1 on error (i.e. when the given
126 * type does not fit in the filter).
128 * @param filter The filter object to change.
129 * @param type The type for which the bit should be cleared.
131 * @return @c 1 if bit was set, @c -1 otherwise.
134 coap_option_clrb(coap_opt_filter_t filter, unsigned short type) {
135 return bits_clrb((uint8_t *)filter, sizeof(coap_opt_filter_t), type);
139 * Gets the corresponding bit for @p type in @p filter. This function
140 * returns @c 1 if the bit is set @c 0 if not, or @c -1 on error (i.e.
141 * when the given type does not fit in the filter).
143 * @param filter The filter object to read bit from..
144 * @param type The type for which the bit should be read.
146 * @return @c 1 if bit was set, @c 0 if not, @c -1 on error.
149 coap_option_getb(const coap_opt_filter_t filter, unsigned short type) {
150 return bits_getb((uint8_t *)filter, sizeof(coap_opt_filter_t), type);
154 * Iterator to run through PDU options. This object must be
155 * initialized with coap_option_iterator_init(). Call
156 * coap_option_next() to walk through the list of options until
157 * coap_option_next() returns @c NULL.
160 * coap_opt_t *option;
161 * coap_opt_iterator_t opt_iter;
162 * coap_option_iterator_init(pdu, &opt_iter, COAP_OPT_ALL);
164 * while ((option = coap_option_next(&opt_iter))) {
165 * ... do something with option ...
170 size_t length; /**< remaining length of PDU */
171 unsigned short type; /**< decoded option type */
172 unsigned int bad:1; /**< iterator object is ok if not set */
173 unsigned int filtered:1; /**< denotes whether or not filter is used */
174 coap_opt_t *next_option; /**< pointer to the unparsed next option */
175 coap_opt_filter_t filter; /**< option filter */
176 } coap_opt_iterator_t;
179 * Initializes the given option iterator @p oi to point to the
180 * beginning of the @p pdu's option list. This function returns @p oi
181 * on success, @c NULL otherwise (i.e. when no options exist).
182 * Note that a length check on the option list must be performed before
183 * coap_option_iterator_init() is called.
185 * @param pdu The PDU the options of which should be walked through.
186 * @param oi An iterator object that will be initilized.
187 * @param filter An optional option type filter.
188 * With @p type != @c COAP_OPT_ALL, coap_option_next()
189 * will return only options matching this bitmask.
190 * Fence-post options @c 14, @c 28, @c 42, ... are always
193 * @return The iterator object @p oi on success, @c NULL otherwise.
195 coap_opt_iterator_t *coap_option_iterator_init(coap_pdu_t *pdu,
196 coap_opt_iterator_t *oi, const coap_opt_filter_t filter);
199 * Updates the iterator @p oi to point to the next option. This
200 * function returns a pointer to that option or @c NULL if no more
201 * options exist. The contents of @p oi will be updated. In
202 * particular, @c oi->n specifies the current option's ordinal number
203 * (counted from @c 1), @c oi->type is the option's type code, and @c
204 * oi->option points to the beginning of the current option
205 * itself. When advanced past the last option, @c oi->option will be
208 * Note that options are skipped whose corresponding bits in the
209 * filter specified with coap_option_iterator_init() are @c 0. Options
210 * with type codes that do not fit in this filter hence will always be
213 * @param oi The option iterator to update.
215 * @return The next option or @c NULL if no more options exist.
217 coap_opt_t *coap_option_next(coap_opt_iterator_t *oi);
220 * Retrieves the first option of type @p type from @p pdu. @p oi must
221 * point to a coap_opt_iterator_t object that will be initialized by
222 * this function to filter only options with code @p type. This
223 * function returns the first option with this type, or @c NULL if not
226 * @param pdu The PDU to parse for options.
227 * @param type The option type code to search for.
228 * @param oi An iterator object to use.
230 * @return A pointer to the first option of type @p type, or @c NULL
233 coap_opt_t *coap_check_option(coap_pdu_t *pdu,
235 coap_opt_iterator_t *oi);
238 * Encodes the given delta and length values into @p opt. This
239 * function returns the number of bytes that were required to encode
240 * @p delta and @p length or @c 0 on error. Note that the result
241 * indicates by how many bytes @p opt must be advanced to encode the
244 * @param opt The option buffer space where @p delta and @p length are
246 * @param maxlen The maximum length of @p opt
247 * @param delta The actual delta value to encode.
248 * @param length The actual length value to encode.
249 * @return The number of bytes used or @c 0 on error.
251 size_t coap_opt_setheader(coap_opt_t *opt, size_t maxlen,
252 unsigned short delta, size_t length);
255 * Encodes option with given @p delta into @p opt. This function returns
256 * the number of bytes written to @p opt or @c 0 on error. This happens
257 * especially when @p opt does not provide sufficient space to store
258 * the option value, delta, and option jumps when required.
260 * @param opt The option buffer space where @p val is written
261 * @param n Maximum length of @p opt.
262 * @param delta The option delta.
263 * @param val The option value to copy into @p opt.
264 * @param len The actual length of @p val.
265 * @return The number of bytes that have been written to @p opt or
266 * @c 0 on error. The return value will always be less than @p n.
268 size_t coap_opt_encode(coap_opt_t *opt, size_t n, unsigned short delta,
269 const unsigned char *val, size_t length);
272 * Decodes the delta value of the next option. This function returns
273 * the number of bytes read or @c 0 on error. The caller of this
274 * function must ensure that it does not read over the boundaries
275 * of @p opt (e.g. by calling coap_opt_check_delta().
277 * @param opt The option to examine
278 * @return The number of bytes read or @c 0 on error.
280 unsigned short coap_opt_delta(const coap_opt_t *opt);
282 /** @deprecated { Use coap_opt_delta() instead. } */
283 #define COAP_OPT_DELTA(opt) coap_opt_delta(opt)
285 /** @deprecated { Use coap_opt_encode() instead. } */
286 #define COAP_OPT_SETDELTA(opt,val) \
287 coap_opt_encode((opt), COAP_MAX_PDU_SIZE, (val), NULL, 0)
290 * Returns the length of the given option. @p opt must point to an
291 * option jump or the beginning of the option. This function returns
292 * @c 0 when @p opt is not an option or the actual length of @p opt
293 * (which can be @c 0 as well).
295 * @note {The rationale for using @c 0 in case of an error is that in
296 * most contexts, the result of this function is used to skip the next
297 * coap_opt_length() bytes. }
299 * @param opt The option whose length should be returned.
300 * @return The option's length or @c 0 when undefined.
302 unsigned short coap_opt_length(const coap_opt_t *opt);
304 /** @deprecated { Use coap_opt_length() instead. } */
305 #define COAP_OPT_LENGTH(opt) coap_opt_length(opt)
308 * Returns a pointer to the value of the given option. @p opt must
309 * point to an option jump or the beginning of the option. This
310 * function returns @c NULL if @p opt is not a valid option.
312 * @param opt The option whose value should be returned.
313 * @return A pointer to the option value or @c NULL on error.
315 unsigned char *coap_opt_value(coap_opt_t *opt);
317 /** @deprecated { Use coap_opt_value() instead. } */
318 #define COAP_OPT_VALUE(opt) coap_opt_value((coap_opt_t *)opt)
322 #endif /* _OPTION_H_ */