libcoap/resource.h

/* resource.h -- generic resource handling
 *
 * Copyright (C) 2010,2011 Olaf Bergmann <bergmann@tzi.org>
 *
 * This file is part of the CoAP library libcoap. Please see
 * README for terms of use. 
 */

/** 
 * @file resource.h
 * @brief generic resource handling
 */

#ifndef _COAP_RESOURCE_H_
#define _COAP_RESOURCE_H_

#include "config.h"

#if defined(HAVE_ASSERT_H) && !defined(assert)
# include <assert.h>
#endif

#ifndef COAP_RESOURCE_CHECK_TIME
/** The interval in seconds to check if resources have changed. */
#define COAP_RESOURCE_CHECK_TIME 2
#endif /* COAP_RESOURCE_CHECK_TIME */

#ifndef WITH_CONTIKI
#include "uthash.h"
#else /* WITH_CONTIKI */
#include "list.h"
#endif /* WITH_CONTIKI */
#include "hashkey.h"
#include "async.h"
#include "str.h"
#include "pdu.h"
#include "net.h"
#include "subscribe.h"

/** Definition of message handler function (@sa coap_resource_t). */
typedef void (*coap_method_handler_t)
  (coap_context_t  *, struct coap_resource_t *, coap_address_t *, coap_pdu_t *,
   str * /* token */, coap_pdu_t * /* response */);

typedef struct coap_attr_t {
  struct coap_attr_t *next;
  str name;
  str value;
} coap_attr_t;

typedef struct coap_resource_t {
  unsigned int dirty:1;	      /**< set to 1 if resource has changed */
  unsigned int observeable:1; /**< can be observed */
  unsigned int cacheable:1;   /**< can be cached */

  /** 
   * Used to store handlers for the four coap methods @c GET, @c POST,
   * @c PUT, and @c DELETE. coap_dispatch() will pass incoming
   * requests to the handler that corresponds to its request method or
   * generate a 4.05 response if no handler is available.
   */
  coap_method_handler_t handler[4];

  coap_key_t key;	/**< the actual key bytes for this resource */

#ifndef WITH_CONTIKI
  UT_hash_handle hh;
  coap_attr_t *link_attr; /**< attributes to be included with the link format */
  coap_subscription_t *subscribers; /**< list of observers for this resource */
#else /* WITH_CONTIKI */
  LIST_STRUCT(link_attr); /**< attributes to be included with the link format */
  LIST_STRUCT(subscribers); /**< list of observers for this resource */
#endif /* WITH_CONTIKI */


  /**
   * Request URI for this resource. This field will point into the
   * static memory. */
  str uri;
} coap_resource_t;

/** 
 * Creates a new resource object and initializes the link field to the
 * string of length @p len.  This function returns the
 * new coap_resource_t object.
 * 
 * @param uri  The URI path of the new resource.
 * @param len  The length of @p uri.
 * 
 * @return A pointer to the new object or @c NULL on error.
 */
coap_resource_t *coap_resource_init(const unsigned char *uri, size_t len);

/**
 * Registers the given @p resource for @p context. The resource must
 * have been created by coap_resource_init(), the storage allocated
 * for the resource will be released by coap_delete_resource().
 * 
 * @param context  The context to use.
 * @param resource The resource to store.
 */
void coap_add_resource(coap_context_t *context, coap_resource_t *resource);

/** 
 * Deletes a resource identified by @p key. The storage allocated for
 * that resource is freed.
 * 
 * @param context  The context where the resources are stored.
 * @param key      The unique key for the resource to delete.
 * 
 * @return @c 1 if the resource was found (and destroyed), @c 0 otherwise.
 */
int coap_delete_resource(coap_context_t *context, coap_key_t key);

/** 
 * Registers a new attribute with the given @p resource. As the
 * attributes str fields will point to @p name and @p val the 
 * caller must ensure that these pointers are valid during the
 * attribute's lifetime.
 * 
 * @param resource  The resource to register the attribute with.
 * @param name      The attribute's name.
 * @param nlen      Length of @p name.
 * @param val       The attribute's value or @c NULL if none.
 * @param vlen      Length of @p val if specified.
 *
 * @return A pointer to the new attribute or @c NULL on error.
 */
coap_attr_t *coap_add_attr(coap_resource_t *resource, 
			   const unsigned char *name, size_t nlen,
			   const unsigned char *val, size_t vlen);

/** 
 * Writes a description of this resource in link-format to given text
 * buffer. @p len must be initialized to the maximum length of @p buf
 * and will be set to the number of characters actually written if
 * successful.  This function returns @c 1 on success or @c 0 on
 * error.
 * 
 * @param resource The resource to describe.
 * @param buf      The output buffer to write the description to.
 * @param len      Must be initialized to the length of @p buf and 
 * will be set to the number of characters written on success.
 * 
 * @return @c 1 on success, or @c 0 on error. If @c 0, @p len is
 * undefined.
 */
int coap_print_link(const coap_resource_t *resource, 
		    unsigned char *buf, size_t *len);

/** 
 * Registers the specified @p handler as message handler for the request type
 * @p method 
 * 
 * @param resource The resource for which the handler shall be registered.
 * @param method   The CoAP request method to handle. 
 * @param handler  The handler to register with @p resource.
 */
static inline void
coap_register_handler(coap_resource_t *resource, 
		      unsigned char method, coap_method_handler_t handler) {
  assert(resource);
  assert(method > 0 && (size_t)(method-1) < sizeof(resource->handler)/sizeof(coap_method_handler_t));
  resource->handler[method-1] = handler;
}

/** 
 * Returns the resource identified by the unique string @p key. If no
 * resource was found, this function returns @c NULL.
 * 
 * @param context  The context to look for this resource.
 * @param key      The unique key of the resource.
 * 
 * @return A pointer to the resource or @c NULL if not found.
 */
coap_resource_t *coap_get_resource_from_key(coap_context_t *context, 
					    coap_key_t key);

/** 
 * Calculates the hash key for the resource requested by the
 * Uri-Options of @p request.  This function calls coap_hash() for
 * every path segment. 
 * 
 * @param context The context to use.
 * @param request The requesting pdu.
 */
void coap_hash_request_uri(const coap_pdu_t *request, coap_key_t key);

/** 
 * @addtogroup observe 
 */

/**
 * Adds the specified peer as observer for @p resource. The
 * subscription is identified by the given @p token. This function
 * returns the registered subscription information if the @p observer
 * has been added, or @c NULL on error.
 *
 * @param resource The observed resource.
 * @param observer The remote peer that wants to received status updates.
 * @param token The token that identifies this subscription.
 * @param token_length The actual length of @p token. Must be @c 0 when
 *        @p token is @c NULL.
 * @return A pointer to the added/updated subscription information or 
 *        @c NULL on error.
 */
coap_subscription_t *coap_add_observer(coap_resource_t *resource, 
				       const coap_address_t *observer,
				       const str *token);

/**
 * Returns a subscription object for given @p peer.
 *
 * @param resource The observed resource.
 * @param peer The address to search for.
 * @param token The token that identifies this subscription or @c NULL for any
 *              token.
 * @return A valid subscription if exists or @c NULL otherwise.
 */
coap_subscription_t *coap_find_observer(coap_resource_t *resource, 
					const coap_address_t *peer,
					const str *token);

/**
 * Removes any subscription for @p observer from @p resource and releases
 * the allocated storage.
 *
 * @param resource The observed resource.
 * @param observer The observer's address.
 * @param token    The token that identifies this subscription or @c NULL for any
 *                 token.
 */
void coap_delete_observer(coap_resource_t *resource, 
			  coap_address_t *observer, 
			  const str *token);

/** 
 * Checks for all known resources, if they are dirty and notifies
 * subscribed observers.
 */
void coap_check_notify(coap_context_t *context);

/** @} */

#endif /* _COAP_RESOURCE_H_ */