411 lines
14 KiB
C
411 lines
14 KiB
C
/*
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* option.h -- helpers for handling options in CoAP PDUs
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*
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* Copyright (C) 2010-2013 Olaf Bergmann <bergmann@tzi.org>
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*
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* This file is part of the CoAP library libcoap. Please see README for terms
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* of use.
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*/
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/**
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* @file option.h
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* @brief Helpers for handling options in CoAP PDUs
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*/
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#ifndef _COAP_OPTION_H_
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#define _COAP_OPTION_H_
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#include "bits.h"
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#include "pdu.h"
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/**
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* Use byte-oriented access methods here because sliding a complex struct
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* coap_opt_t over the data buffer may cause bus error on certain platforms.
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*/
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typedef unsigned char coap_opt_t;
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#define PCHAR(p) ((coap_opt_t *)(p))
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/** Representation of CoAP options. */
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typedef struct {
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unsigned short delta;
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size_t length;
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unsigned char *value;
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} coap_option_t;
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/**
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* Parses the option pointed to by @p opt into @p result. This function returns
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* the number of bytes that have been parsed, or @c 0 on error. An error is
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* signaled when illegal delta or length values are encountered or when option
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* parsing would result in reading past the option (i.e. beyond opt + length).
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*
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* @param opt The beginning of the option to parse.
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* @param length The maximum length of @p opt.
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* @param result A pointer to the coap_option_t structure that is filled with
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* actual values iff coap_opt_parse() > 0.
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* @return The number of bytes parsed or @c 0 on error.
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*/
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size_t coap_opt_parse(const coap_opt_t *opt,
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size_t length,
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coap_option_t *result);
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/**
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* Returns the size of the given option, taking into account a possible option
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* jump.
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*
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* @param opt An option jump or the beginning of the option.
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* @return The number of bytes between @p opt and the end of the option
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* starting at @p opt. In case of an error, this function returns
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* @c 0 as options need at least one byte storage space.
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*/
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size_t coap_opt_size(const coap_opt_t *opt);
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/** @deprecated { Use coap_opt_size() instead. } */
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#define COAP_OPT_SIZE(opt) coap_opt_size(opt)
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/**
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* Calculates the beginning of the PDU's option section.
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*
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* @param pdu The PDU containing the options.
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* @return A pointer to the first option if available, or @c NULL otherwise.
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*/
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coap_opt_t *options_start(coap_pdu_t *pdu);
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/**
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* Interprets @p opt as pointer to a CoAP option and advances to
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* the next byte past this option.
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* @hideinitializer
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*/
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#define options_next(opt) \
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((coap_opt_t *)((unsigned char *)(opt) + COAP_OPT_SIZE(opt)))
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/**
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* @defgroup opt_filter Option Filters
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* @{
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*/
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/**
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* The number of option types below 256 that can be stored in an
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* option filter. COAP_OPT_FILTER_SHORT + COAP_OPT_FILTER_LONG must be
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* at most 16. Each coap_option_filter_t object reserves
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* ((COAP_OPT_FILTER_SHORT + 1) / 2) * 2 bytes for short options.
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*/
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#define COAP_OPT_FILTER_SHORT 6
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/**
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* The number of option types above 255 that can be stored in an
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* option filter. COAP_OPT_FILTER_SHORT + COAP_OPT_FILTER_LONG must be
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* at most 16. Each coap_option_filter_t object reserves
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* COAP_OPT_FILTER_LONG * 2 bytes for short options.
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*/
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#define COAP_OPT_FILTER_LONG 2
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/* Ensure that COAP_OPT_FILTER_SHORT and COAP_OPT_FILTER_LONG are set
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* correctly. */
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#if (COAP_OPT_FILTER_SHORT + COAP_OPT_FILTER_LONG > 16)
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#error COAP_OPT_FILTER_SHORT + COAP_OPT_FILTER_LONG must be less or equal 16
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#endif /* (COAP_OPT_FILTER_SHORT + COAP_OPT_FILTER_LONG > 16) */
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/** The number of elements in coap_opt_filter_t. */
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#define COAP_OPT_FILTER_SIZE \
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(((COAP_OPT_FILTER_SHORT + 1) >> 1) + COAP_OPT_FILTER_LONG) +1
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/**
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* Fixed-size vector we use for option filtering. It is large enough
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* to hold COAP_OPT_FILTER_SHORT entries with an option number between
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* 0 and 255, and COAP_OPT_FILTER_LONG entries with an option number
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* between 256 and 65535. Its internal structure is
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*
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* @code
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struct {
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uint16_t mask;
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uint16_t long_opts[COAP_OPT_FILTER_LONG];
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uint8_t short_opts[COAP_OPT_FILTER_SHORT];
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}
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* @endcode
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*
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* The first element contains a bit vector that indicates which fields
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* in the remaining array are used. The first COAP_OPT_FILTER_LONG
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* bits correspond to the long option types that are stored in the
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* elements from index 1 to COAP_OPT_FILTER_LONG. The next
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* COAP_OPT_FILTER_SHORT bits correspond to the short option types
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* that are stored in the elements from index COAP_OPT_FILTER_LONG + 1
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* to COAP_OPT_FILTER_LONG + COAP_OPT_FILTER_SHORT. The latter
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* elements are treated as bytes.
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*/
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typedef uint16_t coap_opt_filter_t[COAP_OPT_FILTER_SIZE];
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/** Pre-defined filter that includes all options. */
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#define COAP_OPT_ALL NULL
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/**
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* Clears filter @p f.
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*
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* @param f The filter to clear.
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*/
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static inline void
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coap_option_filter_clear(coap_opt_filter_t f) {
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memset(f, 0, sizeof(coap_opt_filter_t));
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}
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/**
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* Sets the corresponding entry for @p type in @p filter. This
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* function returns @c 1 if bit was set or @c 0 on error (i.e. when
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* the given type does not fit in the filter).
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*
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* @param filter The filter object to change.
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* @param type The type for which the bit should be set.
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*
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* @return @c 1 if bit was set, @c 0 otherwise.
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*/
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int coap_option_filter_set(coap_opt_filter_t filter, unsigned short type);
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/**
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* Clears the corresponding entry for @p type in @p filter. This
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* function returns @c 1 if bit was set or @c 0 on error (i.e. when
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* the given type does not fit in the filter).
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*
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* @param filter The filter object to change.
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* @param type The type that should be cleared from the filter.
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*
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* @return @c 1 if bit was set, @c 0 otherwise.
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*/
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int coap_option_filter_unset(coap_opt_filter_t filter, unsigned short type);
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/**
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* Checks if @p type is contained in @p filter. This function returns
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* @c 1 if found, @c 0 if not, or @c -1 on error (i.e. when the given
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* type does not fit in the filter).
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*
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* @param filter The filter object to search.
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* @param type The type to search for.
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*
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* @return @c 1 if @p type was found, @c 0 otherwise, or @c -1 on error.
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*/
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int coap_option_filter_get(const coap_opt_filter_t filter, unsigned short type);
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/**
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* Sets the corresponding bit for @p type in @p filter. This function returns @c
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* 1 if bit was set or @c -1 on error (i.e. when the given type does not fit in
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* the filter).
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*
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* @deprecated Use coap_option_filter_set() instead.
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*
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* @param filter The filter object to change.
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* @param type The type for which the bit should be set.
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*
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* @return @c 1 if bit was set, @c -1 otherwise.
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*/
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inline static int
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coap_option_setb(coap_opt_filter_t filter, unsigned short type) {
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return coap_option_filter_set(filter, type) ? 1 : -1;
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}
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/**
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* Clears the corresponding bit for @p type in @p filter. This function returns
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* @c 1 if bit was cleared or @c -1 on error (i.e. when the given type does not
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* fit in the filter).
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*
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* @deprecated Use coap_option_filter_unset() instead.
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*
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* @param filter The filter object to change.
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* @param type The type for which the bit should be cleared.
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*
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* @return @c 1 if bit was set, @c -1 otherwise.
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*/
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inline static int
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coap_option_clrb(coap_opt_filter_t filter, unsigned short type) {
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return coap_option_filter_unset(filter, type) ? 1 : -1;
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}
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/**
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* Gets the corresponding bit for @p type in @p filter. This function returns @c
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* 1 if the bit is set @c 0 if not, or @c -1 on error (i.e. when the given type
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* does not fit in the filter).
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*
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* @deprecated Use coap_option_filter_get() instead.
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*
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* @param filter The filter object to read bit from.
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* @param type The type for which the bit should be read.
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*
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* @return @c 1 if bit was set, @c 0 if not, @c -1 on error.
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*/
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inline static int
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coap_option_getb(const coap_opt_filter_t filter, unsigned short type) {
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return coap_option_filter_get(filter, type);
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}
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/**
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* Iterator to run through PDU options. This object must be
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* initialized with coap_option_iterator_init(). Call
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* coap_option_next() to walk through the list of options until
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* coap_option_next() returns @c NULL.
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*
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* @code
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* coap_opt_t *option;
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* coap_opt_iterator_t opt_iter;
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* coap_option_iterator_init(pdu, &opt_iter, COAP_OPT_ALL);
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*
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* while ((option = coap_option_next(&opt_iter))) {
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* ... do something with option ...
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* }
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* @endcode
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*/
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typedef struct {
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size_t length; /**< remaining length of PDU */
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unsigned short type; /**< decoded option type */
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unsigned int bad:1; /**< iterator object is ok if not set */
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unsigned int filtered:1; /**< denotes whether or not filter is used */
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coap_opt_t *next_option; /**< pointer to the unparsed next option */
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coap_opt_filter_t filter; /**< option filter */
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} coap_opt_iterator_t;
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/**
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* Initializes the given option iterator @p oi to point to the beginning of the
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* @p pdu's option list. This function returns @p oi on success, @c NULL
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* otherwise (i.e. when no options exist). Note that a length check on the
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* option list must be performed before coap_option_iterator_init() is called.
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*
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* @param pdu The PDU the options of which should be walked through.
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* @param oi An iterator object that will be initilized.
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* @param filter An optional option type filter.
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* With @p type != @c COAP_OPT_ALL, coap_option_next()
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* will return only options matching this bitmask.
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* Fence-post options @c 14, @c 28, @c 42, ... are always
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* skipped.
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*
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* @return The iterator object @p oi on success, @c NULL otherwise.
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*/
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coap_opt_iterator_t *coap_option_iterator_init(coap_pdu_t *pdu,
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coap_opt_iterator_t *oi,
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const coap_opt_filter_t filter);
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/**
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* Updates the iterator @p oi to point to the next option. This function returns
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* a pointer to that option or @c NULL if no more options exist. The contents of
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* @p oi will be updated. In particular, @c oi->n specifies the current option's
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* ordinal number (counted from @c 1), @c oi->type is the option's type code,
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* and @c oi->option points to the beginning of the current option itself. When
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* advanced past the last option, @c oi->option will be @c NULL.
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*
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* Note that options are skipped whose corresponding bits in the filter
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* specified with coap_option_iterator_init() are @c 0. Options with type codes
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* that do not fit in this filter hence will always be returned.
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*
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* @param oi The option iterator to update.
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*
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* @return The next option or @c NULL if no more options exist.
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*/
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coap_opt_t *coap_option_next(coap_opt_iterator_t *oi);
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/**
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* Retrieves the first option of type @p type from @p pdu. @p oi must point to a
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* coap_opt_iterator_t object that will be initialized by this function to
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* filter only options with code @p type. This function returns the first option
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* with this type, or @c NULL if not found.
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*
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* @param pdu The PDU to parse for options.
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* @param type The option type code to search for.
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* @param oi An iterator object to use.
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*
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* @return A pointer to the first option of type @p type, or @c NULL if
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* not found.
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*/
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coap_opt_t *coap_check_option(coap_pdu_t *pdu,
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unsigned short type,
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coap_opt_iterator_t *oi);
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/**
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* Encodes the given delta and length values into @p opt. This function returns
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* the number of bytes that were required to encode @p delta and @p length or @c
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* 0 on error. Note that the result indicates by how many bytes @p opt must be
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* advanced to encode the option value.
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*
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* @param opt The option buffer space where @p delta and @p length are
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* written.
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* @param maxlen The maximum length of @p opt.
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* @param delta The actual delta value to encode.
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* @param length The actual length value to encode.
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*
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* @return The number of bytes used or @c 0 on error.
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*/
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size_t coap_opt_setheader(coap_opt_t *opt,
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size_t maxlen,
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unsigned short delta,
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size_t length);
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/**
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* Encodes option with given @p delta into @p opt. This function returns the
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* number of bytes written to @p opt or @c 0 on error. This happens especially
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* when @p opt does not provide sufficient space to store the option value,
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* delta, and option jumps when required.
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*
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* @param opt The option buffer space where @p val is written.
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* @param n Maximum length of @p opt.
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* @param delta The option delta.
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* @param val The option value to copy into @p opt.
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* @param length The actual length of @p val.
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*
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* @return The number of bytes that have been written to @p opt or @c 0 on
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* error. The return value will always be less than @p n.
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*/
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size_t coap_opt_encode(coap_opt_t *opt,
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size_t n,
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unsigned short delta,
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const unsigned char *val,
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size_t length);
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/**
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* Decodes the delta value of the next option. This function returns the number
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* of bytes read or @c 0 on error. The caller of this function must ensure that
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* it does not read over the boundaries of @p opt (e.g. by calling
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* coap_opt_check_delta().
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*
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* @param opt The option to examine.
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*
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* @return The number of bytes read or @c 0 on error.
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*/
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unsigned short coap_opt_delta(const coap_opt_t *opt);
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/** @deprecated { Use coap_opt_delta() instead. } */
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#define COAP_OPT_DELTA(opt) coap_opt_delta(opt)
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/** @deprecated { Use coap_opt_encode() instead. } */
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#define COAP_OPT_SETDELTA(opt,val) \
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coap_opt_encode((opt), COAP_MAX_PDU_SIZE, (val), NULL, 0)
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/**
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* Returns the length of the given option. @p opt must point to an option jump
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* or the beginning of the option. This function returns @c 0 when @p opt is not
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* an option or the actual length of @p opt (which can be @c 0 as well).
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*
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* @note {The rationale for using @c 0 in case of an error is that in most
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* contexts, the result of this function is used to skip the next
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* coap_opt_length() bytes.}
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*
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* @param opt The option whose length should be returned.
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*
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* @return The option's length or @c 0 when undefined.
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*/
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unsigned short coap_opt_length(const coap_opt_t *opt);
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/** @deprecated { Use coap_opt_length() instead. } */
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#define COAP_OPT_LENGTH(opt) coap_opt_length(opt)
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/**
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* Returns a pointer to the value of the given option. @p opt must point to an
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* option jump or the beginning of the option. This function returns @c NULL if
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* @p opt is not a valid option.
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*
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* @param opt The option whose value should be returned.
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*
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* @return A pointer to the option value or @c NULL on error.
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*/
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unsigned char *coap_opt_value(coap_opt_t *opt);
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/** @deprecated { Use coap_opt_value() instead. } */
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#define COAP_OPT_VALUE(opt) coap_opt_value((coap_opt_t *)opt)
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/** @} */
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#endif /* _OPTION_H_ */
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