/* coap_subscribe.c -- subscription handling for CoAP

 *                see RFC7641

 *

 * Copyright (C) 2010-2019,2022-2026 Olaf Bergmann <bergmann@tzi.org>

 *

 * SPDX-License-Identifier: BSD-2-Clause

 *

 * This file is part of the CoAP library libcoap. Please see

 * README for terms of use.

 */

/**

 * @file coap_subscribe.c

 * @brief Subscription handling functions

 */

#include "coap3/coap_libcoap_build.h"

#ifndef min

#define min(a,b) ((a) < (b) ? (a) : (b))

#endif

int

coap_observe_persist_is_supported(void) {

#if COAP_SERVER_SUPPORT && COAP_WITH_OBSERVE_PERSIST

  return 1;

#else /* ! (COAP_SERVER_SUPPORT && COAP_WITH_OBSERVE_PERSIST) */

  return 0;

#endif /* ! (COAP_SERVER_SUPPORT && COAP_WITH_OBSERVE_PERSIST) */

}

#if COAP_SERVER_SUPPORT

void

coap_subscription_init(coap_subscription_t *s) {

  assert(s);

  memset(s, 0, sizeof(coap_subscription_t));

}

void

coap_persist_track_funcs(coap_context_t *context,

                         coap_observe_added_t observe_added,

                         coap_observe_deleted_t observe_deleted,

                         coap_track_observe_value_t track_observe_value,

                         coap_dyn_resource_added_t dyn_resource_added,

                         coap_resource_deleted_t resource_deleted,

                         uint32_t save_freq,

                         void *user_data) {

  context->observe_added_cb = observe_added;

  context->observe_deleted_cb = observe_deleted;

  context->observe_user_data = user_data;

  context->observe_save_freq = save_freq ? save_freq : 1;

  context->track_observe_value_cb = track_observe_value;

  context->dyn_resource_added_cb = dyn_resource_added;

  context->resource_deleted_cb = resource_deleted;

}

COAP_API coap_subscription_t *

coap_persist_observe_add(coap_context_t *context,

                         coap_proto_t e_proto,

                         const coap_address_t *e_listen_addr,

                         const coap_addr_tuple_t *s_addr_info,

                         const coap_bin_const_t *raw_packet,

                         const coap_bin_const_t *oscore_info) {

  coap_subscription_t *subs;

  coap_lock_lock(return NULL);

  subs = coap_persist_observe_add_lkd(context,

                                      e_proto,

                                      e_listen_addr,

                                      s_addr_info,

                                      raw_packet,

                                      oscore_info);

  coap_lock_unlock();

  return subs;

}

coap_subscription_t *

coap_persist_observe_add_lkd(coap_context_t *context,

                             coap_proto_t e_proto,

                             const coap_address_t *e_listen_addr,

                             const coap_addr_tuple_t *s_addr_info,

                             const coap_bin_const_t *raw_packet,

                             const coap_bin_const_t *oscore_info) {

  coap_session_t *session = NULL;

  const uint8_t *data;

  size_t data_len;

  coap_pdu_t *pdu = NULL;

#if COAP_CONSTRAINED_STACK

  /* e_packet can be protected by global_lock if needed */

  static coap_packet_t e_packet;

#else /* ! COAP_CONSTRAINED_STACK */

  coap_packet_t e_packet;

#endif /* ! COAP_CONSTRAINED_STACK */

  coap_packet_t *packet = &e_packet;

  coap_tick_t now;

  coap_string_t *uri_path = NULL;

  coap_opt_iterator_t opt_iter;

  coap_opt_t *observe;

  int observe_action;

  coap_resource_t *r;

  coap_subscription_t *s = NULL;

  coap_endpoint_t *ep;

  coap_lock_check_locked();

  if (e_listen_addr == NULL || s_addr_info == NULL || raw_packet == NULL)

    return NULL;

  /* Will be creating a local 'open' session */

  if (e_proto != COAP_PROTO_UDP)

    return NULL;

  ep = context->endpoint;

  while (ep) {

    if (ep->proto == e_proto &&

        memcmp(e_listen_addr, &ep->bind_addr, sizeof(ep->bind_addr)) == 0)

      break;

    ep = ep->next;

  }

  if (!ep) {

    if (COAP_LOG_WARN <= coap_get_log_level()) {

#ifndef INET6_ADDRSTRLEN

#define INET6_ADDRSTRLEN 40

#endif

      unsigned char addr_str[INET6_ADDRSTRLEN + 8];

      if (coap_print_addr(e_listen_addr, addr_str, INET6_ADDRSTRLEN + 8)) {

        coap_log_warn("coap_persist_observe_add: Endpoint %s not defined\n",

                      addr_str);

      }

    }

    return NULL;

  }

  /* Build up packet */

  memcpy(&packet->addr_info, s_addr_info, sizeof(packet->addr_info));

  packet->ifindex = 0;

  memcpy(&packet->payload, &raw_packet->s, sizeof(packet->payload));

  packet->length = raw_packet->length;

  data = raw_packet->s;

  data_len = raw_packet->length;

  if (data_len < 4)

    goto malformed;

  /* Get the session */

  coap_ticks(&now);

  session = coap_endpoint_get_session(ep, packet, now);

  if (session == NULL)

    goto fail;

  /* Need max space in case PDU is updated with updated token, huge size etc. */

  pdu = coap_pdu_init(0, 0, 0, 0);

  if (!pdu)

    goto fail;

  if (!coap_pdu_parse(session->proto, data, data_len, pdu)) {

    goto malformed;

  }

  pdu->max_size = pdu->used_size;

  if (pdu->code != COAP_REQUEST_CODE_GET &&

      pdu->code != COAP_REQUEST_CODE_FETCH)

    goto malformed;

  observe = coap_check_option(pdu, COAP_OPTION_OBSERVE, &opt_iter);

  if (observe == NULL)

    goto malformed;

  observe_action = coap_decode_var_bytes(coap_opt_value(observe),

                                         coap_opt_length(observe));

  if (observe_action != COAP_OBSERVE_ESTABLISH)

    goto malformed;

  /* Get the resource */

  uri_path = coap_get_uri_path(pdu);

  if (!uri_path)

    goto malformed;

  r = coap_get_resource_from_uri_path_lkd(session->context,

                                          (coap_str_const_t *)uri_path);

  if (r == NULL) {

    coap_log_warn("coap_persist_observe_add: resource '%s' not defined\n",

                  uri_path->s);

    goto fail;

  }

  if (!r->observable) {

    coap_log_warn("coap_persist_observe_add: resource '%s' not observable\n",

                  uri_path->s);

    goto fail;

  }

  coap_delete_string(uri_path);

  uri_path = NULL;

  /* Create / update subscription for observing */

  /* Now set up the subscription */

  s = coap_add_observer(r, session, &pdu->actual_token, pdu);

  if (s == NULL)

    goto fail;

#if COAP_OSCORE_SUPPORT

  if (oscore_info) {

    coap_log_debug("persist: OSCORE association being updated\n");

    /*

     * Need to track the association used for tracking this observe, done as

     * a CBOR array. Written in coap_add_observer().

     *

     * If an entry is null, then use nil, else a set of bytes

     *

     * Currently tracking 5 items

     *  recipient_id

     *  id_context

     *  aad        (from oscore_association_t)

     *  partial_iv (from oscore_association_t)

     *  nonce      (from oscore_association_t)

     */

    oscore_ctx_t *osc_ctx;

    const uint8_t *info_buf = oscore_info->s;

    size_t info_buf_len = oscore_info->length;

    size_t ret = 0;

    coap_bin_const_t oscore_key_id;

    coap_bin_const_t partial_iv;

    coap_bin_const_t aad;

    coap_bin_const_t id_context;

    coap_bin_const_t nonce;

    int have_aad = 0;

    int have_partial_iv = 0;

    int have_id_context = 0;

    int have_nonce = 0;

    ret = oscore_cbor_get_next_element(&info_buf, &info_buf_len);

    if (ret != CBOR_ARRAY)

      goto oscore_fail;

    if (oscore_cbor_get_element_size(&info_buf, &info_buf_len) != 5)

      goto oscore_fail;

    /* recipient_id */

    ret = oscore_cbor_get_next_element(&info_buf, &info_buf_len);

    if (ret != CBOR_BYTE_STRING)

      goto oscore_fail;

    oscore_key_id.length = oscore_cbor_get_element_size(&info_buf,

                                                        &info_buf_len);

    if (oscore_key_id.length > info_buf_len)

      goto oscore_fail;

    oscore_key_id.s = info_buf;

    info_buf += oscore_key_id.length;

    info_buf_len -= oscore_key_id.length;

    /* id_context */

    ret = oscore_cbor_get_next_element(&info_buf, &info_buf_len);

    if (ret == CBOR_BYTE_STRING) {

      id_context.length = oscore_cbor_get_element_size(&info_buf,

                                                       &info_buf_len);

      if (id_context.length > info_buf_len)

        goto oscore_fail;

      id_context.s = info_buf;

      info_buf += id_context.length;

      info_buf_len -= id_context.length;

      have_id_context = 1;

    } else if (ret == CBOR_SIMPLE_VALUE &&

               oscore_cbor_get_element_size(&info_buf,

                                            &info_buf_len) == CBOR_NULL) {

    } else

      goto oscore_fail;

    /* aad */

    ret = oscore_cbor_get_next_element(&info_buf, &info_buf_len);

    if (ret == CBOR_BYTE_STRING) {

      aad.length = oscore_cbor_get_element_size(&info_buf, &info_buf_len);

      if (aad.length > info_buf_len)

        goto oscore_fail;

      aad.s = info_buf;

      info_buf += aad.length;

      info_buf_len -= aad.length;

      have_aad = 1;

    } else if (ret == CBOR_SIMPLE_VALUE &&

               oscore_cbor_get_element_size(&info_buf,

                                            &info_buf_len) == CBOR_NULL) {

    } else

      goto oscore_fail;

    /* partial_iv */

    ret = oscore_cbor_get_next_element(&info_buf, &info_buf_len);

    if (ret == CBOR_BYTE_STRING) {

      partial_iv.length = oscore_cbor_get_element_size(&info_buf,

                                                       &info_buf_len);

      if (partial_iv.length > info_buf_len)

        goto oscore_fail;

      partial_iv.s = info_buf;

      info_buf += partial_iv.length;

      info_buf_len -= partial_iv.length;

      have_partial_iv = 1;

    } else if (ret == CBOR_SIMPLE_VALUE &&

               oscore_cbor_get_element_size(&info_buf,

                                            &info_buf_len) == CBOR_NULL) {

    } else

      goto oscore_fail;

    /* nonce */

    ret = oscore_cbor_get_next_element(&info_buf, &info_buf_len);

    if (ret == CBOR_BYTE_STRING) {

      nonce.length = oscore_cbor_get_element_size(&info_buf,

                                                  &info_buf_len);

      if (nonce.length > info_buf_len)

        goto oscore_fail;

      nonce.s = info_buf;

      info_buf += nonce.length;

      info_buf_len -= nonce.length;

      have_nonce = 1;

    } else if (ret == CBOR_SIMPLE_VALUE &&

               oscore_cbor_get_element_size(&info_buf,

                                            &info_buf_len) == CBOR_NULL) {

    } else

      goto oscore_fail;

    osc_ctx = oscore_find_context(session, oscore_key_id,

                                  have_id_context ? &id_context : NULL, NULL,

                                  &session->recipient_ctx);

    if (osc_ctx) {

      session->oscore_encryption = 1;

      oscore_new_association(session, pdu, &pdu->actual_token,

                             session->recipient_ctx,

                             have_aad ? &aad : NULL,

                             have_nonce ? &nonce : NULL,

                             have_partial_iv ? &partial_iv : NULL,

                             1);

      coap_log_debug("persist: OSCORE association added\n");

      oscore_log_hex_value(COAP_LOG_OSCORE, "partial_iv",

                           have_partial_iv ? &partial_iv : NULL);

    }

  }

oscore_fail:

#else /* ! COAP_OSCORE_SUPPORT */

  (void)oscore_info;

#endif /* ! COAP_OSCORE_SUPPORT */

  coap_delete_pdu_lkd(pdu);

  return s;

malformed:

  coap_log_warn("coap_persist_observe_add: discard malformed PDU\n");

fail:

  coap_delete_string(uri_path);

  coap_delete_pdu_lkd(pdu);

  return NULL;

}

#if COAP_WITH_OBSERVE_PERSIST

#include <stdio.h>

/*

 * read in active observe entry.

 */

static int

coap_op_observe_read(FILE *fp, coap_subscription_t **observe_key,

                     coap_proto_t *e_proto, coap_address_t *e_listen_addr,

                     coap_addr_tuple_t *s_addr_info,

                     coap_bin_const_t **raw_packet, coap_bin_const_t **oscore_info) {

  ssize_t size;

  coap_binary_t *scratch = NULL;

  assert(fp && observe_key && e_proto && e_listen_addr && s_addr_info &&

         raw_packet && oscore_info);

  *raw_packet = NULL;

  *oscore_info = NULL;

  if (fread(observe_key, sizeof(*observe_key), 1, fp) == 1) {

    /* New record 'key proto listen addr_info len raw_packet len oscore' */

    if (fread(e_proto, sizeof(*e_proto), 1, fp) != 1)

      goto fail;

    if (fread(e_listen_addr, sizeof(*e_listen_addr), 1, fp) != 1)

      goto fail;

    if (fread(s_addr_info, sizeof(*s_addr_info), 1, fp) != 1)

      goto fail;

    if (fread(&size, sizeof(size), 1, fp) != 1)

      goto fail;

    if (size < 0 || size > 0x10000)

      goto fail;

    scratch = coap_new_binary(size);

    if ((scratch) == NULL)

      goto fail;

    if (fread(scratch->s, scratch->length, 1, fp) != 1)

      goto fail;

    *raw_packet = (coap_bin_const_t *)scratch;

    scratch = NULL;

    if (fread(&size, sizeof(size), 1, fp) != 1)

      goto fail;

    /* If size == -1, then no oscore information */

    if (size == -1)

      return 1;

    else if (size < 0 || size > 0x10000)

      goto fail;

    else {

      scratch = coap_new_binary(size);

      if (scratch == NULL)

        goto fail;

      if (fread(scratch->s, scratch->length, 1, fp) != 1)

        goto fail;

      *oscore_info = (coap_bin_const_t *)scratch;

    }

    return 1;

  }

fail:

  coap_delete_bin_const(*raw_packet);

  coap_delete_binary(scratch);

  *observe_key = NULL;

  memset(e_proto, 0, sizeof(*e_proto));

  memset(e_listen_addr, 0, sizeof(*e_listen_addr));

  memset(s_addr_info, 0, sizeof(*s_addr_info));

  *raw_packet = NULL;

  return 0;

}

/*

 * write out active observe entry.

 */

static int

coap_op_observe_write(FILE *fp, coap_subscription_t *observe_key,

                      coap_proto_t e_proto, coap_address_t e_listen_addr,

                      coap_addr_tuple_t s_addr_info,

                      coap_bin_const_t *raw_packet, coap_bin_const_t *oscore_info) {

  if (fwrite(&observe_key, sizeof(observe_key), 1, fp) != 1)

    goto fail;

  if (fwrite(&e_proto, sizeof(e_proto), 1, fp) != 1)

    goto fail;

  if (fwrite(&e_listen_addr, sizeof(e_listen_addr),

             1, fp) != 1)

    goto fail;

  if (fwrite(&s_addr_info, sizeof(s_addr_info), 1, fp) != 1)

    goto fail;

  if (fwrite(&raw_packet->length, sizeof(raw_packet->length), 1, fp) != 1)

    goto fail;

  if (fwrite(raw_packet->s, raw_packet->length, 1, fp) != 1)

    goto fail;

  if (oscore_info) {

    if (fwrite(&oscore_info->length, sizeof(oscore_info->length), 1, fp) != 1)

      goto fail;

    if (fwrite(oscore_info->s, oscore_info->length, 1, fp) != 1)

      goto fail;

  } else {

    ssize_t not_defined = -1;

    if (fwrite(&not_defined, sizeof(not_defined), 1, fp) != 1)

      goto fail;

  }

  return 1;

fail:

  return 0;

}

/*

 * This should be called before coap_persist_track_funcs() to prevent

 * coap_op_observe_added() getting unnecessarily called.

 * It should be called after init_resources() and coap_op_resource_load_disk()

 * so that all the resources are in place.

 */

static void

coap_op_observe_load_disk(coap_context_t *ctx) {

  FILE *fp_orig = fopen((const char *)ctx->observe_save_file->s, "r");

  FILE *fp_new = NULL;

  coap_subscription_t *observe_key = NULL;

  coap_proto_t e_proto;

  coap_address_t e_listen_addr;

  coap_addr_tuple_t s_addr_info;

  coap_bin_const_t *raw_packet = NULL;

  coap_bin_const_t *oscore_info = NULL;

  char *new = NULL;

  if (fp_orig == NULL)

    goto fail;

  new = coap_malloc_type(COAP_STRING, ctx->observe_save_file->length + 5);

  if (!new)

    goto fail;

  strcpy(new, (const char *)ctx->observe_save_file->s);

  strcat(new, ".tmp");

  fp_new = fopen(new, "w+");

  if (fp_new == NULL)

    goto fail;

  /* Go through and load oscore entry, updating key on the way */

  while (1) {

    if (!coap_op_observe_read(fp_orig, &observe_key, &e_proto, &e_listen_addr,

                              &s_addr_info, &raw_packet, &oscore_info))

      break;

    coap_log_debug("persist: New session/observe being created\n");

    observe_key = coap_persist_observe_add_lkd(ctx, e_proto,

                                               &e_listen_addr,

                                               &s_addr_info,

                                               raw_packet,

                                               oscore_info);

    if (observe_key) {

      if (!coap_op_observe_write(fp_new, observe_key, e_proto, e_listen_addr,

                                 s_addr_info, raw_packet, oscore_info))

        goto fail;

    }

    coap_delete_bin_const(raw_packet);

    raw_packet = NULL;

    coap_delete_bin_const(oscore_info);

    oscore_info = NULL;

  }

  coap_delete_bin_const(raw_packet);

  raw_packet = NULL;

  coap_delete_bin_const(oscore_info);

  oscore_info = NULL;

  if (fflush(fp_new) == EOF)

    goto fail;

  fclose(fp_new);

  fclose(fp_orig);

  /* Either old or new is in place */

  if (rename(new, (const char *)ctx->observe_save_file->s) == -1) {

    coap_log_warn("rename %s -> %s: failed: %s (%d)\n",

                  new, (const char *)ctx->observe_save_file->s,

                  coap_socket_strerror(), errno);

  }

  coap_free_type(COAP_STRING, new);

  return;

fail:

  coap_delete_bin_const(raw_packet);

  coap_delete_bin_const(oscore_info);

  if (fp_new)

    fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  if (new) {

    (void)remove(new);

  }

  coap_free_type(COAP_STRING, new);

  return;

}

/*

 * client has registered a new observe subscription request.

 */

static int

coap_op_observe_added(coap_session_t *session,

                      coap_subscription_t *a_observe_key,

                      coap_proto_t a_e_proto, coap_address_t *a_e_listen_addr,

                      coap_addr_tuple_t *a_s_addr_info,

                      coap_bin_const_t *a_raw_packet,

                      coap_bin_const_t *a_oscore_info, void *user_data) {

  FILE *fp_orig = fopen((const char *)session->context->observe_save_file->s,

                        "r");

  FILE *fp_new = NULL;

  coap_subscription_t *observe_key = NULL;

  coap_proto_t e_proto;

  coap_address_t e_listen_addr;

  coap_addr_tuple_t s_addr_info;

  coap_bin_const_t *raw_packet = NULL;

  coap_bin_const_t *oscore_info = NULL;

  char *new = NULL;

  (void)user_data;

  new = coap_malloc_type(COAP_STRING,

                         session->context->observe_save_file->length + 5);

  if (!new)

    goto fail;

  strcpy(new, (const char *)session->context->observe_save_file->s);

  strcat(new, ".tmp");

  fp_new = fopen(new, "w+");

  if (fp_new == NULL)

    goto fail;

  /* Go through and delete observe entry if it exists */

  while (fp_orig) {

    if (!coap_op_observe_read(fp_orig, &observe_key, &e_proto, &e_listen_addr,

                              &s_addr_info, &raw_packet, &oscore_info))

      break;

    if (observe_key != a_observe_key) {

      if (!coap_op_observe_write(fp_new, observe_key, e_proto, e_listen_addr,

                                 s_addr_info, raw_packet, oscore_info))

        goto fail;

    }

    coap_delete_bin_const(raw_packet);

    raw_packet = NULL;

    coap_delete_bin_const(oscore_info);

    oscore_info = NULL;

  }

  coap_delete_bin_const(raw_packet);

  raw_packet = NULL;

  coap_delete_bin_const(oscore_info);

  oscore_info = NULL;

  /* Add in new entry to the end */

  if (!coap_op_observe_write(fp_new, a_observe_key, a_e_proto, *a_e_listen_addr,

                             *a_s_addr_info, a_raw_packet, a_oscore_info))

    goto fail;

  if (fflush(fp_new) == EOF)

    goto fail;

  fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  /* Either old or new is in place */

  (void)rename(new, (const char *)session->context->observe_save_file->s);

  coap_free_type(COAP_STRING, new);

  return 1;

fail:

  coap_delete_bin_const(raw_packet);

  coap_delete_bin_const(oscore_info);

  if (fp_new)

    fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  if (new) {

    (void)remove(new);

  }

  coap_free_type(COAP_STRING, new);

  return 0;

}

/*

 * client has de-registered a observe subscription request.

 */

static int

coap_op_observe_deleted(coap_session_t *session,

                        coap_subscription_t *d_observe_key,

                        void *user_data) {

  FILE *fp_orig = fopen((const char *)session->context->observe_save_file->s,

                        "r");

  FILE *fp_new = NULL;

  coap_subscription_t *observe_key = NULL;

  coap_proto_t e_proto;

  coap_address_t e_listen_addr;

  coap_addr_tuple_t s_addr_info;

  coap_bin_const_t *raw_packet = NULL;

  coap_bin_const_t *oscore_info = NULL;

  char *new = NULL;

  (void)user_data;

  if (fp_orig == NULL)

    goto fail;

  new = coap_malloc_type(COAP_STRING,

                         session->context->observe_save_file->length + 5);

  if (!new)

    goto fail;

  strcpy(new, (const char *)session->context->observe_save_file->s);

  strcat(new, ".tmp");

  fp_new = fopen(new, "w+");

  if (fp_new == NULL)

    goto fail;

  /* Go through and locate observe entry to delete and not copy it across */

  while (1) {

    if (!coap_op_observe_read(fp_orig, &observe_key, &e_proto, &e_listen_addr,

                              &s_addr_info, &raw_packet, &oscore_info))

      break;

    if (observe_key != d_observe_key) {

      if (!coap_op_observe_write(fp_new, observe_key, e_proto, e_listen_addr,

                                 s_addr_info, (coap_bin_const_t *)raw_packet,

                                 (coap_bin_const_t *)oscore_info))

        goto fail;

    }

    coap_delete_bin_const(raw_packet);

    raw_packet = NULL;

    coap_delete_bin_const(oscore_info);

    oscore_info = NULL;

  }

  coap_delete_bin_const(raw_packet);

  raw_packet = NULL;

  coap_delete_bin_const(oscore_info);

  oscore_info = NULL;

  if (fflush(fp_new) == EOF)

    goto fail;

  fclose(fp_new);

  fclose(fp_orig);

  /* Either old or new is in place */

  (void)rename(new, (const char *)session->context->observe_save_file->s);

  coap_free_type(COAP_STRING, new);

  return 1;

fail:

  coap_delete_bin_const(raw_packet);

  coap_delete_bin_const(oscore_info);

  if (fp_new)

    fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  if (new) {

    (void)remove(new);

  }

  coap_free_type(COAP_STRING, new);

  return 0;

}

/*

 * This should be called before coap_persist_track_funcs() to prevent

 * coap_op_obs_cnt_track_observe() getting unnecessarily called.

 * Should be called after coap_op_dyn_resource_load_disk() to make sure that

 * all the resources are in the right place.

 */

static void

coap_op_obs_cnt_load_disk(coap_context_t *context) {

  FILE *fp = fopen((const char *)context->obs_cnt_save_file->s, "r");

  char buf[1500];

  if (fp == NULL)

    return;

  while (fgets(buf, sizeof(buf), fp) != NULL) {

    char *cp = strchr(buf, ' ');

    coap_str_const_t resource_key;

    uint32_t observe_num;

    coap_resource_t *r;

    if (!cp)

      break;

    *cp = '\000';

    cp++;

    observe_num = atoi(cp);

    /*

     * Need to assume 0 .. (context->observe_save_freq-1) have in addition

     * been sent so need to round up to latest possible send value

     */

    observe_num = ((observe_num + context->observe_save_freq) /

                   context->observe_save_freq) *

                  context->observe_save_freq - 1;

    resource_key.s = (uint8_t *)buf;

    resource_key.length = strlen(buf);

    r = coap_get_resource_from_uri_path_lkd(context, &resource_key);

    if (r) {

      coap_log_debug("persist: Initial observe number being updated '%s' %u\n",

                     buf, observe_num);

      coap_persist_set_observe_num(r, observe_num);

    }

  }

  fclose(fp);

}

/*

 * Called when the observe value of a resource has been changed, but limited

 * to be called every context->context->observe_save_freq to reduce update

 * overheads.

 */

static int

coap_op_obs_cnt_track_observe(coap_context_t *context,

                              coap_str_const_t *resource_name,

                              uint32_t n_observe_num,

                              void *user_data) {

  FILE *fp_orig = fopen((const char *)context->obs_cnt_save_file->s, "r");

  FILE *fp_new = NULL;

  char buf[1500];

  char *new = NULL;

  (void)user_data;

  new = coap_malloc_type(COAP_STRING, context->obs_cnt_save_file->length + 5);

  if (!new)

    goto fail;

  strcpy(new, (const char *)context->obs_cnt_save_file->s);

  strcat(new, ".tmp");

  fp_new = fopen(new, "w+");

  if (fp_new == NULL)

    goto fail;

  /* Go through and locate resource entry to update */

  while (fp_orig && fgets(buf, sizeof(buf), fp_orig) != NULL) {

    char *cp = strchr(buf, ' ');

    uint32_t observe_num;

    coap_bin_const_t resource_key;

    if (!cp)

      break;

    *cp = '\000';

    cp++;

    observe_num = atoi(cp);

    resource_key.s = (uint8_t *)buf;

    resource_key.length = strlen(buf);

    if (!coap_binary_equal(resource_name, &resource_key)) {

      if (fprintf(fp_new, "%s %u\n", resource_key.s, observe_num) < 0)

        goto fail;

    }

  }

  if (fprintf(fp_new, "%s %u\n", resource_name->s, n_observe_num) < 0)

    goto fail;

  if (fflush(fp_new) == EOF)

    goto fail;

  fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  /* Either old or new is in place */

  (void)rename(new, (const char *)context->obs_cnt_save_file->s);

  coap_free_type(COAP_STRING, new);

  return 1;

fail:

  if (fp_new)

    fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  if (new) {

    (void)remove(new);

  }

  coap_free_type(COAP_STRING, new);

  return 0;

}

/*

 * Called when a resource has been deleted.

 */

static int

coap_op_obs_cnt_deleted(coap_context_t *context,

                        coap_str_const_t *resource_name) {

  FILE *fp_orig = fopen((const char *)context->obs_cnt_save_file->s, "r");

  FILE *fp_new = NULL;

  char buf[1500];

  char *new = NULL;

  if (fp_orig == NULL)

    goto fail;

  new = coap_malloc_type(COAP_STRING, context->obs_cnt_save_file->length + 5);

  if (!new)

    goto fail;

  strcpy(new, (const char *)context->obs_cnt_save_file->s);

  strcat(new, ".tmp");

  fp_new = fopen(new, "w+");

  if (fp_new == NULL)

    goto fail;

  /* Go through and locate resource entry to delete */

  while (fgets(buf, sizeof(buf), fp_orig) != NULL) {

    char *cp = strchr(buf, ' ');

    uint32_t observe_num;

    coap_bin_const_t resource_key;

    if (!cp)

      break;

    *cp = '\000';

    cp++;

    observe_num = atoi(cp);

    resource_key.s = (uint8_t *)buf;

    resource_key.length = strlen(buf);

    if (!coap_binary_equal(resource_name, &resource_key)) {

      if (fprintf(fp_new, "%s %u\n", resource_key.s, observe_num) < 0)

        goto fail;

    }

  }

  if (fflush(fp_new) == EOF)

    goto fail;

  fclose(fp_new);

  fclose(fp_orig);

  /* Either old or new is in place */

  (void)rename(new, (const char *)context->obs_cnt_save_file->s);

  coap_free_type(COAP_STRING, new);

  return 1;

fail:

  if (fp_new)

    fclose(fp_new);

  if (fp_orig)

    fclose(fp_orig);

  if (new) {

    (void)remove(new);

  }

  coap_free_type(COAP_STRING, new);

  return 0;

}

/*

 * read in dynamic resource entry, allocating name & raw_packet

 * which need to be freed off by caller.

 */

static int

coap_op_dyn_resource_read(FILE *fp, coap_proto_t *e_proto,

                          coap_string_t **name,

                          coap_binary_t **raw_packet) {

  ssize_t size;

  *name = NULL;

  *raw_packet = NULL;

  if (fread(e_proto, sizeof(*e_proto), 1, fp) == 1) {

    /* New record 'proto len resource_name len raw_packet' */

    if (fread(&size, sizeof(size), 1, fp) != 1)

      goto fail;

    if (size < 0 || size > 0x10000)

      goto fail;

    *name = coap_new_string(size);

    if (!(*name))

      goto fail;

    if (fread((*name)->s, size, 1, fp) != 1)

      goto fail;

    if (fread(&size, sizeof(size), 1, fp) != 1)

      goto fail;

    if (size < 0 || size > 0x10000)

      goto fail;

    *raw_packet = coap_new_binary(size);

    if (!(*raw_packet))

      goto fail;

    if (fread((*raw_packet)->s, size, 1, fp) != 1)

      goto fail;

    return 1;

  }

fail:

  return 0;

}

/*

 * write out dynamic resource entry.

 */

static int

coap_op_dyn_resource_write(FILE *fp, coap_proto_t e_proto,

                           coap_str_const_t *name,

                           coap_bin_const_t *raw_packet) {

  if (fwrite(&e_proto, sizeof(e_proto), 1, fp) != 1)

    goto fail;

  if (fwrite(&name->length, sizeof(name->length), 1, fp) != 1)

    goto fail;

  if (fwrite(name->s, name->length, 1, fp) != 1)

    goto fail;

  if (fwrite(&raw_packet->length, sizeof(raw_packet->length), 1, fp) != 1)

    goto fail;

  if (fwrite(raw_packet->s, raw_packet->length, 1, fp) != 1)

    goto fail;

  return 1;

fail:

  return 0;

}

/*

 * This should be called before coap_persist_track_funcs() to prevent

 * coap_op_dyn_resource_added() getting unnecessarily called.

 *

 * Each record 'proto len resource_name len raw_packet'

 */