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. */
38 * Parses the option pointed to by @p opt into @p result. This
39 * function returns the number of bytes that have been parsed, or @c 0
40 * on error. An error is signaled when illegal delta or length values
41 * are encountered or when option parsing would result in reading past
42 * the option (i.e. beyond opt + length).
44 * @param opt The beginning of the option to parse.
45 * @param length The maximum length of @p opt.
46 * @param result A pointer to the coap_option_t structure that is
47 * filled with actual values iff coap_opt_parse() > 0.
48 * @return The number of bytes parsed or @c 0 on error.
50 size_t coap_opt_parse(const coap_opt_t *opt, size_t length, 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.
103 static inline void 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.
118 inline static int 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.
133 inline static int 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.
148 inline static int 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 ...
171 size_t length; /**< remaining length of PDU */
172 unsigned short type; /**< decoded option type */
173 unsigned int bad :1; /**< iterator object is ok if not set */
174 unsigned int filtered :1; /**< denotes whether or not filter is used */
175 coap_opt_t *next_option; /**< pointer to the unparsed next option */
176 coap_opt_filter_t filter; /**< option filter */
177 } coap_opt_iterator_t;
180 * Initializes the given option iterator @p oi to point to the
181 * beginning of the @p pdu's option list. This function returns @p oi
182 * on success, @c NULL otherwise (i.e. when no options exist).
183 * Note that a length check on the option list must be performed before
184 * coap_option_iterator_init() is called.
186 * @param pdu The PDU the options of which should be walked through.
187 * @param oi An iterator object that will be initilized.
188 * @param filter An optional option type filter.
189 * With @p type != @c COAP_OPT_ALL, coap_option_next()
190 * will return only options matching this bitmask.
191 * Fence-post options @c 14, @c 28, @c 42, ... are always
194 * @return The iterator object @p oi on success, @c NULL otherwise.
196 coap_opt_iterator_t *coap_option_iterator_init(coap_pdu_t *pdu, coap_opt_iterator_t *oi,
197 const coap_opt_filter_t filter);
200 * Updates the iterator @p oi to point to the next option. This
201 * function returns a pointer to that option or @c NULL if no more
202 * options exist. The contents of @p oi will be updated. In
203 * particular, @c oi->n specifies the current option's ordinal number
204 * (counted from @c 1), @c oi->type is the option's type code, and @c
205 * oi->option points to the beginning of the current option
206 * itself. When advanced past the last option, @c oi->option will be
209 * Note that options are skipped whose corresponding bits in the
210 * filter specified with coap_option_iterator_init() are @c 0. Options
211 * with type codes that do not fit in this filter hence will always be
214 * @param oi The option iterator to update.
216 * @return The next option or @c NULL if no more options exist.
218 coap_opt_t *coap_option_next(coap_opt_iterator_t *oi);
221 * Retrieves the first option of type @p type from @p pdu. @p oi must
222 * point to a coap_opt_iterator_t object that will be initialized by
223 * this function to filter only options with code @p type. This
224 * function returns the first option with this type, or @c NULL if not
227 * @param pdu The PDU to parse for options.
228 * @param type The option type code to search for.
229 * @param oi An iterator object to use.
231 * @return A pointer to the first option of type @p type, or @c NULL
234 coap_opt_t *coap_check_option(coap_pdu_t *pdu, unsigned char type, coap_opt_iterator_t *oi);
237 * Encodes the given delta and length values into @p opt. This
238 * function returns the number of bytes that were required to encode
239 * @p delta and @p length or @c 0 on error. Note that the result
240 * indicates by how many bytes @p opt must be advanced to encode the
243 * @param opt The option buffer space where @p delta and @p length are
245 * @param maxlen The maximum length of @p opt
246 * @param delta The actual delta value to encode.
247 * @param length The actual length value to encode.
248 * @return The number of bytes used or @c 0 on error.
250 size_t coap_opt_setheader(coap_opt_t *opt, size_t maxlen, unsigned short delta, size_t length);
253 * Encodes option with given @p delta into @p opt. This function returns
254 * the number of bytes written to @p opt or @c 0 on error. This happens
255 * especially when @p opt does not provide sufficient space to store
256 * the option value, delta, and option jumps when required.
258 * @param opt The option buffer space where @p val is written
259 * @param n Maximum length of @p opt.
260 * @param delta The option delta.
261 * @param val The option value to copy into @p opt.
262 * @param len The actual length of @p val.
263 * @return The number of bytes that have been written to @p opt or
264 * @c 0 on error. The return value will always be less than @p n.
266 size_t coap_opt_encode(coap_opt_t *opt, size_t n, unsigned short delta, const unsigned char *val,
270 * Decodes the delta value of the next option. This function returns
271 * the number of bytes read or @c 0 on error. The caller of this
272 * function must ensure that it does not read over the boundaries
273 * of @p opt (e.g. by calling coap_opt_check_delta().
275 * @param opt The option to examine
276 * @return The number of bytes read or @c 0 on error.
278 unsigned short coap_opt_delta(const coap_opt_t *opt);
280 /** @deprecated { Use coap_opt_delta() instead. } */
281 #define COAP_OPT_DELTA(opt) coap_opt_delta(opt)
283 /** @deprecated { Use coap_opt_encode() instead. } */
284 #define COAP_OPT_SETDELTA(opt,val) \
285 coap_opt_encode((opt), COAP_MAX_PDU_SIZE, (val), NULL, 0)
288 * Returns the length of the given option. @p opt must point to an
289 * option jump or the beginning of the option. This function returns
290 * @c 0 when @p opt is not an option or the actual length of @p opt
291 * (which can be @c 0 as well).
293 * @note {The rationale for using @c 0 in case of an error is that in
294 * most contexts, the result of this function is used to skip the next
295 * coap_opt_length() bytes. }
297 * @param opt The option whose length should be returned.
298 * @return The option's length or @c 0 when undefined.
300 unsigned short coap_opt_length(const coap_opt_t *opt);
302 /** @deprecated { Use coap_opt_length() instead. } */
303 #define COAP_OPT_LENGTH(opt) coap_opt_length(opt)
306 * Returns a pointer to the value of the given option. @p opt must
307 * point to an option jump or the beginning of the option. This
308 * function returns @c NULL if @p opt is not a valid option.
310 * @param opt The option whose value should be returned.
311 * @return A pointer to the option value or @c NULL on error.
313 unsigned char *coap_opt_value(coap_opt_t *opt);
315 /** @deprecated { Use coap_opt_value() instead. } */
316 #define COAP_OPT_VALUE(opt) coap_opt_value((coap_opt_t *)opt)
320 #endif /* _OPTION_H_ */