path: root/system/bta/gatt/bta_gattc_cache.cc

/******************************************************************************
 *
 *  Copyright 2003-2012 Broadcom Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at:
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 ******************************************************************************/

/******************************************************************************
 *
 *  This file contains the GATT client discovery procedures and cache
 *  related functions.
 *
 ******************************************************************************/

#define LOG_TAG "bt_bta_gattc"

#include <base/logging.h>
#include <base/strings/string_number_conversions.h>
#include <base/strings/stringprintf.h>

#include <cstdint>
#include <cstdio>
#include <sstream>

#include "bt_target.h"  // Must be first to define build configuration
#include "bta/gatt/bta_gattc_int.h"
#include "bta/gatt/database.h"
#include "osi/include/allocator.h"
#include "osi/include/log.h"
#include "stack/btm/btm_sec.h"
#include "stack/include/gatt_api.h"
#include "types/bluetooth/uuid.h"
#include "types/raw_address.h"

using base::StringPrintf;
using bluetooth::Uuid;
using gatt::Characteristic;
using gatt::Database;
using gatt::DatabaseBuilder;
using gatt::Descriptor;
using gatt::IncludedService;
using gatt::Service;

static tGATT_STATUS bta_gattc_sdp_service_disc(uint16_t conn_id,
                                               tBTA_GATTC_SERV* p_server_cb);
const Descriptor* bta_gattc_get_descriptor_srcb(tBTA_GATTC_SERV* p_srcb,
                                                uint16_t handle);
const Characteristic* bta_gattc_get_characteristic_srcb(tBTA_GATTC_SERV* p_srcb,
                                                        uint16_t handle);
static void bta_gattc_explore_srvc_finished(uint16_t conn_id,
                                            tBTA_GATTC_SERV* p_srvc_cb);

static void bta_gattc_read_db_hash_cmpl(tBTA_GATTC_CLCB* p_clcb,
                                        const tBTA_GATTC_OP_CMPL* p_data,
                                        bool is_svc_chg);

static void bta_gattc_read_ext_prop_desc_cmpl(tBTA_GATTC_CLCB* p_clcb,
                                              const tBTA_GATTC_OP_CMPL* p_data);

// define the max retry count for DATABASE_OUT_OF_SYNC
#define BTA_GATTC_DISCOVER_RETRY_COUNT 2

#define BTA_GATT_SDP_DB_SIZE 4096

/*****************************************************************************
 *  Constants and data types
 ****************************************************************************/

typedef struct {
  tSDP_DISCOVERY_DB* p_sdp_db;
  uint16_t sdp_conn_id;
} tBTA_GATTC_CB_DATA;

#if (BTA_GATT_DEBUG == TRUE)
/* utility functions */

/* debug function to display the server cache */
static void bta_gattc_display_cache_server(const Database& database) {
  LOG(INFO) << "<=--------------=Start Server Cache =-----------=>";
  std::istringstream iss(database.ToString());
  for (std::string line; std::getline(iss, line);) {
    LOG(INFO) << line;
  }
  LOG(INFO) << "<=--------------=End Server Cache =-----------=>";
}

/** debug function to display the exploration list */
static void bta_gattc_display_explore_record(const DatabaseBuilder& database) {
  LOG(INFO) << "<=--------------=Start Explore Queue =-----------=>";
  std::istringstream iss(database.ToString());
  for (std::string line; std::getline(iss, line);) {
    LOG(INFO) << line;
  }
  LOG(INFO) << "<=--------------= End Explore Queue =-----------=>";
}
#endif /* BTA_GATT_DEBUG == TRUE */

/** Initialize the database cache and discovery related resources */
void bta_gattc_init_cache(tBTA_GATTC_SERV* p_srvc_cb) {
  p_srvc_cb->gatt_database = gatt::Database();
  p_srvc_cb->pending_discovery.Clear();
}

const Service* bta_gattc_find_matching_service(
    const std::list<Service>& services, uint16_t handle) {
  for (const Service& service : services) {
    if (handle >= service.handle && handle <= service.end_handle)
      return &service;
  }

  return nullptr;
}

/** Start primary service discovery */
tGATT_STATUS bta_gattc_discover_pri_service(uint16_t conn_id,
                                            tBTA_GATTC_SERV* p_server_cb,
                                            tGATT_DISC_TYPE disc_type) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);
  if (!p_clcb) return GATT_ERROR;

  if (p_clcb->transport == BT_TRANSPORT_LE) {
    return GATTC_Discover(conn_id, disc_type, 0x0001, 0xFFFF);
  }

  // only for Classic transport
  return bta_gattc_sdp_service_disc(conn_id, p_server_cb);
}

/** start exploring next service, or finish discovery if no more services left
 */
static void bta_gattc_explore_next_service(uint16_t conn_id,
                                           tBTA_GATTC_SERV* p_srvc_cb) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);
  if (!p_clcb) {
    LOG(ERROR) << "unknown conn_id=" << loghex(conn_id);
    return;
  }

  if (p_srvc_cb->pending_discovery.StartNextServiceExploration()) {
    const auto& service =
        p_srvc_cb->pending_discovery.CurrentlyExploredService();
    VLOG(1) << "Start service discovery";

    /* start discovering included services */
    GATTC_Discover(conn_id, GATT_DISC_INC_SRVC, service.first, service.second);
    return;
  }
  // No more services to discover

  // As part of service discovery, read the values of "Characteristic Extended
  // Properties" descriptor
  const auto& descriptors =
      p_srvc_cb->pending_discovery.DescriptorHandlesToRead();
  if (!descriptors.empty()) {
    // set request field to READ_EXT_PROP_DESC
    p_clcb->request_during_discovery =
        BTA_GATTC_DISCOVER_REQ_READ_EXT_PROP_DESC;

    if (p_srvc_cb->read_multiple_not_supported || descriptors.size() == 1) {
      tGATT_READ_PARAM read_param{
          .by_handle = {.handle = descriptors.front(),
                        .auth_req = GATT_AUTH_REQ_NONE}};
      GATTC_Read(conn_id, GATT_READ_BY_HANDLE, &read_param);
      // asynchronous continuation in bta_gattc_op_cmpl_during_discovery
      return;
    }

    // TODO(jpawlowski): as a limit we should use MTU/2 rather than
    // GATT_MAX_READ_MULTI_HANDLES
    /* each descriptor contains just 2 bytes, so response size is same as
     * request size */
    size_t num_handles =
        std::min(descriptors.size(), (size_t)GATT_MAX_READ_MULTI_HANDLES);

    tGATT_READ_PARAM read_param;
    memset(&read_param, 0, sizeof(tGATT_READ_PARAM));

    read_param.read_multiple.num_handles = num_handles;
    read_param.read_multiple.auth_req = GATT_AUTH_REQ_NONE;
    memcpy(&read_param.read_multiple.handles, descriptors.data(),
           sizeof(uint16_t) * num_handles);
    GATTC_Read(conn_id, GATT_READ_MULTIPLE, &read_param);

    // asynchronous continuation in bta_gattc_op_cmpl_during_discovery
    return;
  }

  bta_gattc_explore_srvc_finished(conn_id, p_srvc_cb);
}

static void bta_gattc_explore_srvc_finished(uint16_t conn_id,
                                            tBTA_GATTC_SERV* p_srvc_cb) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);
  if (!p_clcb) {
    LOG(ERROR) << "unknown conn_id=" << loghex(conn_id);
    return;
  }

  /* no service found at all, the end of server discovery*/
  LOG(INFO) << __func__ << ": service discovery finished";

  p_srvc_cb->gatt_database = p_srvc_cb->pending_discovery.Build();

#if (BTA_GATT_DEBUG == TRUE)
  bta_gattc_display_cache_server(p_srvc_cb->gatt_database);
#endif
  /* save cache to NV */
  p_clcb->p_srcb->state = BTA_GATTC_SERV_SAVE;

  // If robust caching is not enabled, use original design
  if (!bta_gattc_is_robust_caching_enabled()) {
    if (btm_sec_is_a_bonded_dev(p_srvc_cb->server_bda)) {
      bta_gattc_cache_write(p_clcb->p_srcb->server_bda,
                            p_clcb->p_srcb->gatt_database);
    }
  } else {
    // If robust caching is enabled, do something optimized
    Octet16 hash = p_clcb->p_srcb->gatt_database.Hash();
    bool success = bta_gattc_hash_write(hash, p_clcb->p_srcb->gatt_database);

    // If the device is trusted, link the addr file to hash file
    if (success && btm_sec_is_a_bonded_dev(p_srvc_cb->server_bda)) {
      bta_gattc_cache_link(p_clcb->p_srcb->server_bda, hash);
    }

    // After success, reset the count.
    LOG_DEBUG("service discovery succeed, reset count to zero, conn_id=0x%04x",
              conn_id);
    p_srvc_cb->srvc_disc_count = 0;
  }

  bta_gattc_reset_discover_st(p_clcb->p_srcb, GATT_SUCCESS);
}

/** Start discovery for characteristic descriptor */
void bta_gattc_start_disc_char_dscp(uint16_t conn_id,
                                    tBTA_GATTC_SERV* p_srvc_cb) {
  VLOG(1) << "starting discover characteristics descriptor";

  std::pair<uint16_t, uint16_t> range =
      p_srvc_cb->pending_discovery.NextDescriptorRangeToExplore();
  if (range == DatabaseBuilder::EXPLORE_END) {
    goto descriptor_discovery_done;
  }

  if (GATTC_Discover(conn_id, GATT_DISC_CHAR_DSCPT, range.first,
                     range.second) != 0) {
    goto descriptor_discovery_done;
  }
  return;

descriptor_discovery_done:
  /* all characteristic has been explored, start with next service if any */
  DVLOG(3) << "all characteristics explored";

  bta_gattc_explore_next_service(conn_id, p_srvc_cb);
  return;
}

/* Process the discovery result from sdp */
void bta_gattc_sdp_callback(tSDP_STATUS sdp_status, const void* user_data) {
  tBTA_GATTC_CB_DATA* cb_data = (tBTA_GATTC_CB_DATA*)user_data;
  tBTA_GATTC_SERV* p_srvc_cb = bta_gattc_find_scb_by_cid(cb_data->sdp_conn_id);

  if (p_srvc_cb == nullptr) {
    LOG(ERROR) << "GATT service discovery is done on unknown connection";
    /* allocated in bta_gattc_sdp_service_disc */
    osi_free(cb_data);
    return;
  }

  if ((sdp_status != SDP_SUCCESS) && (sdp_status != SDP_DB_FULL)) {
    bta_gattc_explore_srvc_finished(cb_data->sdp_conn_id, p_srvc_cb);

    /* allocated in bta_gattc_sdp_service_disc */
    osi_free(cb_data);
    return;
  }

  bool no_pending_disc = !p_srvc_cb->pending_discovery.InProgress();

  tSDP_DISC_REC* p_sdp_rec = SDP_FindServiceInDb(cb_data->p_sdp_db, 0, nullptr);
  while (p_sdp_rec != nullptr) {
    /* find a service record, report it */
    Uuid service_uuid;
    if (!SDP_FindServiceUUIDInRec(p_sdp_rec, &service_uuid)) continue;

    tSDP_PROTOCOL_ELEM pe;
    if (!SDP_FindProtocolListElemInRec(p_sdp_rec, UUID_PROTOCOL_ATT, &pe))
      continue;

    uint16_t start_handle = (uint16_t)pe.params[0];
    uint16_t end_handle = (uint16_t)pe.params[1];

#if (BTA_GATT_DEBUG == TRUE)
    VLOG(1) << "Found ATT service uuid=" << service_uuid
            << ", s_handle=" << loghex(start_handle)
            << ", e_handle=" << loghex(end_handle);
#endif

    if (!GATT_HANDLE_IS_VALID(start_handle) ||
        !GATT_HANDLE_IS_VALID(end_handle)) {
      LOG(ERROR) << "invalid start_handle=" << loghex(start_handle)
                 << ", end_handle=" << loghex(end_handle);
      continue;
    }

    /* discover services result, add services into a service list */
    p_srvc_cb->pending_discovery.AddService(start_handle, end_handle,
                                            service_uuid, true);

    p_sdp_rec = SDP_FindServiceInDb(cb_data->p_sdp_db, 0, p_sdp_rec);
  }

  // If discovery is already pending, no need to call
  // bta_gattc_explore_next_service. Next service will be picked up to discovery
  // once current one is discovered. If discovery is not pending, start one
  if (no_pending_disc) {
    bta_gattc_explore_next_service(cb_data->sdp_conn_id, p_srvc_cb);
  }

  /* allocated in bta_gattc_sdp_service_disc */
  osi_free(cb_data);
}

/* Start DSP Service Discovery */
static tGATT_STATUS bta_gattc_sdp_service_disc(uint16_t conn_id,
                                               tBTA_GATTC_SERV* p_server_cb) {
  uint16_t num_attrs = 2;
  uint16_t attr_list[2];

  /*
   * On success, cb_data will be freed inside bta_gattc_sdp_callback,
   * otherwise it will be freed within this function.
   */
  tBTA_GATTC_CB_DATA* cb_data = (tBTA_GATTC_CB_DATA*)osi_malloc(
      sizeof(tBTA_GATTC_CB_DATA) + BTA_GATT_SDP_DB_SIZE);

  cb_data->p_sdp_db = (tSDP_DISCOVERY_DB*)(cb_data + 1);
  attr_list[0] = ATTR_ID_SERVICE_CLASS_ID_LIST;
  attr_list[1] = ATTR_ID_PROTOCOL_DESC_LIST;

  Uuid uuid = Uuid::From16Bit(UUID_PROTOCOL_ATT);
  SDP_InitDiscoveryDb(cb_data->p_sdp_db, BTA_GATT_SDP_DB_SIZE, 1, &uuid,
                      num_attrs, attr_list);

  if (!SDP_ServiceSearchAttributeRequest2(
          p_server_cb->server_bda, cb_data->p_sdp_db, &bta_gattc_sdp_callback,
          const_cast<const void*>(static_cast<void*>(cb_data)))) {
    osi_free(cb_data);
    return GATT_ERROR;
  }

  cb_data->sdp_conn_id = conn_id;
  return GATT_SUCCESS;
}

/** operation completed */
void bta_gattc_op_cmpl_during_discovery(tBTA_GATTC_CLCB* p_clcb,
                                        const tBTA_GATTC_DATA* p_data) {
  // Currently, there are two cases needed to be handled.
  // 1. Read ext prop descriptor value after service discovery
  // 2. Read db hash before starting service discovery
  switch (p_clcb->request_during_discovery) {
    case BTA_GATTC_DISCOVER_REQ_READ_EXT_PROP_DESC:
      bta_gattc_read_ext_prop_desc_cmpl(p_clcb, &p_data->op_cmpl);
      break;
    case BTA_GATTC_DISCOVER_REQ_READ_DB_HASH:
    case BTA_GATTC_DISCOVER_REQ_READ_DB_HASH_FOR_SVC_CHG:
      if (bta_gattc_is_robust_caching_enabled()) {
        bool is_svc_chg = (p_clcb->request_during_discovery ==
                           BTA_GATTC_DISCOVER_REQ_READ_DB_HASH_FOR_SVC_CHG);
        bta_gattc_read_db_hash_cmpl(p_clcb, &p_data->op_cmpl, is_svc_chg);
      } else {
        // it is not possible here if flag is off, but just in case
        p_clcb->request_during_discovery = BTA_GATTC_DISCOVER_REQ_NONE;
      }
      break;
    case BTA_GATTC_DISCOVER_REQ_NONE:
    default:
      break;
  }
}

/** callback function to GATT client stack */
void bta_gattc_disc_res_cback(uint16_t conn_id, tGATT_DISC_TYPE disc_type,
                              tGATT_DISC_RES* p_data) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);
  tBTA_GATTC_SERV* p_srvc_cb = bta_gattc_find_scb_by_cid(conn_id);

  if (!p_srvc_cb || !p_clcb || p_clcb->state != BTA_GATTC_DISCOVER_ST) return;

  switch (disc_type) {
    case GATT_DISC_SRVC_ALL:
    case GATT_DISC_SRVC_BY_UUID:
      p_srvc_cb->pending_discovery.AddService(
          p_data->handle, p_data->value.group_value.e_handle,
          p_data->value.group_value.service_type, true);
      break;

    case GATT_DISC_INC_SRVC:
      p_srvc_cb->pending_discovery.AddIncludedService(
          p_data->handle, p_data->value.incl_service.service_type,
          p_data->value.incl_service.s_handle,
          p_data->value.incl_service.e_handle);
      break;

    case GATT_DISC_CHAR:
      p_srvc_cb->pending_discovery.AddCharacteristic(
          p_data->handle, p_data->value.dclr_value.val_handle,
          p_data->value.dclr_value.char_uuid,
          p_data->value.dclr_value.char_prop);
      break;

    case GATT_DISC_CHAR_DSCPT:
      p_srvc_cb->pending_discovery.AddDescriptor(p_data->handle, p_data->type);
      break;

    case GATT_DISC_MAX:
    default:
      LOG_ERROR("Received illegal discovery item");
      break;
  }
}

void bta_gattc_disc_cmpl_cback(uint16_t conn_id, tGATT_DISC_TYPE disc_type,
                               tGATT_STATUS status) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);
  tBTA_GATTC_SERV* p_srvc_cb = bta_gattc_find_scb_by_cid(conn_id);

  if (p_clcb && (status != GATT_SUCCESS || p_clcb->status != GATT_SUCCESS)) {
    if (status == GATT_SUCCESS) p_clcb->status = status;

    // if db out of sync is received, try to start service discovery if possible
    if (bta_gattc_is_robust_caching_enabled() &&
        status == GATT_DATABASE_OUT_OF_SYNC) {
      if (p_srvc_cb &&
          p_srvc_cb->srvc_disc_count < BTA_GATTC_DISCOVER_RETRY_COUNT) {
        p_srvc_cb->srvc_disc_count++;
        p_clcb->auto_update = BTA_GATTC_DISC_WAITING;
      } else {
        LOG(ERROR) << __func__
                   << ": retry limit exceeds for db out of sync, conn_id="
                   << conn_id;
      }
    }

    bta_gattc_sm_execute(p_clcb, BTA_GATTC_DISCOVER_CMPL_EVT, NULL);
    return;
  }

  if (!p_srvc_cb) return;

  switch (disc_type) {
    case GATT_DISC_SRVC_ALL:
    case GATT_DISC_SRVC_BY_UUID:
// definition of all services are discovered, now it's time to discover
// their content
#if (BTA_GATT_DEBUG == TRUE)
      bta_gattc_display_explore_record(p_srvc_cb->pending_discovery);
#endif
      bta_gattc_explore_next_service(conn_id, p_srvc_cb);
      break;

    case GATT_DISC_INC_SRVC: {
      auto& service = p_srvc_cb->pending_discovery.CurrentlyExploredService();
      /* start discovering characteristic */
      GATTC_Discover(conn_id, GATT_DISC_CHAR, service.first, service.second);
      break;
    }

    case GATT_DISC_CHAR: {
#if (BTA_GATT_DEBUG == TRUE)
      bta_gattc_display_explore_record(p_srvc_cb->pending_discovery);
#endif
      bta_gattc_start_disc_char_dscp(conn_id, p_srvc_cb);
      break;
    }

    case GATT_DISC_CHAR_DSCPT:
      /* start discovering next characteristic for char descriptor */
      bta_gattc_start_disc_char_dscp(conn_id, p_srvc_cb);
      break;

    case GATT_DISC_MAX:
    default:
      LOG_ERROR("Received illegal discovery item");
      break;
  }
}

/** search local cache for matching service record */
void bta_gattc_search_service(tBTA_GATTC_CLCB* p_clcb, Uuid* p_uuid) {
  for (const Service& service : p_clcb->p_srcb->gatt_database.Services()) {
    if (p_uuid && *p_uuid != service.uuid) continue;

#if (BTA_GATT_DEBUG == TRUE)
    VLOG(1) << __func__ << "found service " << service.uuid
            << " handle:" << +service.handle;
#endif
    if (!p_clcb->p_rcb->p_cback) continue;

    tBTA_GATTC cb_data;
    memset(&cb_data, 0, sizeof(tBTA_GATTC));
    cb_data.srvc_res.conn_id = p_clcb->bta_conn_id;
    cb_data.srvc_res.service_uuid.inst_id = service.handle;
    cb_data.srvc_res.service_uuid.uuid = service.uuid;

    (*p_clcb->p_rcb->p_cback)(BTA_GATTC_SEARCH_RES_EVT, &cb_data);
  }
}

const std::list<Service>* bta_gattc_get_services_srcb(tBTA_GATTC_SERV* p_srcb) {
  if (!p_srcb || p_srcb->gatt_database.IsEmpty()) return NULL;

  return &p_srcb->gatt_database.Services();
}

const std::list<Service>* bta_gattc_get_services(uint16_t conn_id) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);

  if (p_clcb == NULL) return NULL;

  tBTA_GATTC_SERV* p_srcb = p_clcb->p_srcb;

  return bta_gattc_get_services_srcb(p_srcb);
}

const Service* bta_gattc_get_service_for_handle_srcb(tBTA_GATTC_SERV* p_srcb,
                                                     uint16_t handle) {
  const std::list<Service>* services = bta_gattc_get_services_srcb(p_srcb);
  if (services == NULL) return NULL;
  return bta_gattc_find_matching_service(*services, handle);
}

const Service* bta_gattc_get_service_for_handle(uint16_t conn_id,
                                                uint16_t handle) {
  const std::list<Service>* services = bta_gattc_get_services(conn_id);
  if (services == NULL) return NULL;

  return bta_gattc_find_matching_service(*services, handle);
}

const Characteristic* bta_gattc_get_characteristic_srcb(tBTA_GATTC_SERV* p_srcb,
                                                        uint16_t handle) {
  const Service* service =
      bta_gattc_get_service_for_handle_srcb(p_srcb, handle);

  if (!service) return NULL;

  for (const Characteristic& charac : service->characteristics) {
    if (handle == charac.value_handle) return &charac;
  }

  return NULL;
}

const Characteristic* bta_gattc_get_characteristic(uint16_t conn_id,
                                                   uint16_t handle) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);

  if (p_clcb == NULL) return NULL;

  tBTA_GATTC_SERV* p_srcb = p_clcb->p_srcb;
  return bta_gattc_get_characteristic_srcb(p_srcb, handle);
}

const Descriptor* bta_gattc_get_descriptor_srcb(tBTA_GATTC_SERV* p_srcb,
                                                uint16_t handle) {
  const Service* service =
      bta_gattc_get_service_for_handle_srcb(p_srcb, handle);

  if (!service) {
    return NULL;
  }

  for (const Characteristic& charac : service->characteristics) {
    for (const Descriptor& desc : charac.descriptors) {
      if (handle == desc.handle) return &desc;
    }
  }

  return NULL;
}

const Descriptor* bta_gattc_get_descriptor(uint16_t conn_id, uint16_t handle) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);

  if (p_clcb == NULL) return NULL;

  tBTA_GATTC_SERV* p_srcb = p_clcb->p_srcb;
  return bta_gattc_get_descriptor_srcb(p_srcb, handle);
}

const Characteristic* bta_gattc_get_owning_characteristic_srcb(
    tBTA_GATTC_SERV* p_srcb, uint16_t handle) {
  const Service* service =
      bta_gattc_get_service_for_handle_srcb(p_srcb, handle);

  if (!service) return NULL;

  for (const Characteristic& charac : service->characteristics) {
    for (const Descriptor& desc : charac.descriptors) {
      if (handle == desc.handle) return &charac;
    }
  }

  return NULL;
}

const Characteristic* bta_gattc_get_owning_characteristic(uint16_t conn_id,
                                                          uint16_t handle) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);
  if (!p_clcb) return NULL;

  return bta_gattc_get_owning_characteristic_srcb(p_clcb->p_srcb, handle);
}

/* request reading database hash */
bool bta_gattc_read_db_hash(tBTA_GATTC_CLCB* p_clcb, bool is_svc_chg) {
  tGATT_READ_PARAM read_param;
  memset(&read_param, 0, sizeof(tGATT_READ_BY_TYPE));

  read_param.char_type.s_handle = 0x0001;
  read_param.char_type.e_handle = 0xFFFF;
  read_param.char_type.uuid = Uuid::From16Bit(GATT_UUID_DATABASE_HASH);
  read_param.char_type.auth_req = GATT_AUTH_REQ_NONE;
  tGATT_STATUS status =
      GATTC_Read(p_clcb->bta_conn_id, GATT_READ_BY_TYPE, &read_param);

  if (status != GATT_SUCCESS) return false;

  if (is_svc_chg) {
    p_clcb->request_during_discovery =
        BTA_GATTC_DISCOVER_REQ_READ_DB_HASH_FOR_SVC_CHG;
  } else {
    p_clcb->request_during_discovery = BTA_GATTC_DISCOVER_REQ_READ_DB_HASH;
  }

  return true;
}

/* handle response of reading database hash */
static void bta_gattc_read_db_hash_cmpl(tBTA_GATTC_CLCB* p_clcb,
                                        const tBTA_GATTC_OP_CMPL* p_data,
                                        bool is_svc_chg) {
  uint8_t op = (uint8_t)p_data->op_code;
  if (op != GATTC_OPTYPE_READ) {
    VLOG(1) << __func__ << ": op = " << +p_data->hdr.layer_specific;
    return;
  }
  p_clcb->request_during_discovery = BTA_GATTC_DISCOVER_REQ_NONE;

  // run match flow only if the status is success
  bool matched = false;
  bool found = false;
  if (p_data->status == GATT_SUCCESS) {
    // start to compare local hash and remote hash
    uint16_t len = p_data->p_cmpl->att_value.len;
    uint8_t* data = p_data->p_cmpl->att_value.value;

    Octet16 remote_hash;
    if (len == remote_hash.max_size()) {
      std::copy(data, data + len, remote_hash.begin());

      Octet16 local_hash = p_clcb->p_srcb->gatt_database.Hash();
      matched = (local_hash == remote_hash);

      LOG_DEBUG("lhash=%s",
                base::HexEncode(local_hash.data(), local_hash.size()).c_str());
      LOG_DEBUG(
          "rhash=%s",
          base::HexEncode(remote_hash.data(), remote_hash.size()).c_str());

      if (!matched) {
        gatt::Database db = bta_gattc_hash_load(remote_hash);
        if (!db.IsEmpty()) {
          p_clcb->p_srcb->gatt_database = db;
          found = true;
        }
        // If the device is trusted, link addr file to correct hash file
        if (found && (btm_sec_is_a_bonded_dev(p_clcb->p_srcb->server_bda))) {
          bta_gattc_cache_link(p_clcb->p_srcb->server_bda, remote_hash);
        }
      }
    }
  } else {
    // Only load cache for trusted device if no database hash on server side.
    // If is_svc_chg is true, do not read the existing cache.
    bool is_a_bonded_dev = btm_sec_is_a_bonded_dev(p_clcb->p_srcb->server_bda);
    if (!is_svc_chg && is_a_bonded_dev) {
      gatt::Database db = bta_gattc_cache_load(p_clcb->p_srcb->server_bda);
      if (!db.IsEmpty()) {
        p_clcb->p_srcb->gatt_database = db;
        found = true;
      }
      LOG_DEBUG("load cache directly, result=%d", found);
    } else {
      LOG_DEBUG("skip read cache, is_svc_chg=%d, is_a_bonded_dev=%d",
                is_svc_chg, is_a_bonded_dev);
    }
  }

  if (matched) {
    LOG_DEBUG("hash is the same, skip service discovery");
    p_clcb->p_srcb->state = BTA_GATTC_SERV_IDLE;
    bta_gattc_reset_discover_st(p_clcb->p_srcb, GATT_SUCCESS);
  } else {
    if (found) {
      LOG_DEBUG("hash found in cache, skip service discovery");

#if (BTA_GATT_DEBUG == TRUE)
      bta_gattc_display_cache_server(p_clcb->p_srcb->gatt_database);
#endif

      p_clcb->p_srcb->state = BTA_GATTC_SERV_IDLE;
      bta_gattc_reset_discover_st(p_clcb->p_srcb, GATT_SUCCESS);
    } else {
      LOG_DEBUG("hash is not the same, start service discovery");
      bta_gattc_start_discover_internal(p_clcb);
    }
  }
}

/* handle response of reading extended properties descriptor */
static void bta_gattc_read_ext_prop_desc_cmpl(
    tBTA_GATTC_CLCB* p_clcb, const tBTA_GATTC_OP_CMPL* p_data) {
  uint8_t op = (uint8_t)p_data->op_code;
  if (op != GATTC_OPTYPE_READ) {
    VLOG(1) << __func__ << ": op = " << +p_data->hdr.layer_specific;
    return;
  }

  if (!p_clcb->disc_active) {
    VLOG(1) << __func__ << ": not active in discover state";
    return;
  }
  p_clcb->request_during_discovery = BTA_GATTC_DISCOVER_REQ_NONE;

  tBTA_GATTC_SERV* p_srvc_cb = p_clcb->p_srcb;
  const uint8_t status = p_data->status;

  if (status == GATT_REQ_NOT_SUPPORTED &&
      !p_srvc_cb->read_multiple_not_supported) {
    // can't do "read multiple request", fall back to "read request"
    p_srvc_cb->read_multiple_not_supported = true;
    bta_gattc_explore_next_service(p_clcb->bta_conn_id, p_srvc_cb);
    return;
  }

  if (status != GATT_SUCCESS) {
    LOG(WARNING) << "Discovery on server failed: " << loghex(status);
    bta_gattc_reset_discover_st(p_clcb->p_srcb, GATT_ERROR);
    return;
  }

  const tGATT_VALUE& att_value = p_data->p_cmpl->att_value;
  if (p_srvc_cb->read_multiple_not_supported && att_value.len != 2) {
    // Just one Characteristic Extended Properties value at a time in Read
    // Response
    LOG(WARNING) << __func__ << " Read Response should be just 2 bytes!";
    bta_gattc_reset_discover_st(p_clcb->p_srcb, GATT_ERROR);
    return;
  }

  // Parsing is same for "Read Multiple Response", and for "Read Response"
  const uint8_t* p = att_value.value;
  std::vector<uint16_t> value_of_descriptors;
  while (p < att_value.value + att_value.len) {
    uint16_t extended_properties;
    STREAM_TO_UINT16(extended_properties, p);
    value_of_descriptors.push_back(extended_properties);
  }

  bool ret =
      p_srvc_cb->pending_discovery.SetValueOfDescriptors(value_of_descriptors);
  if (!ret) {
    LOG(WARNING) << __func__
                 << " Problem setting Extended Properties descriptors values";
    bta_gattc_reset_discover_st(p_clcb->p_srcb, GATT_ERROR);
    return;
  }

  // Continue service discovery
  bta_gattc_explore_next_service(p_clcb->bta_conn_id, p_srvc_cb);
}

/*******************************************************************************
 *
 * Function         bta_gattc_fill_gatt_db_el
 *
 * Description      fill a btgatt_db_element_t value
 *
 * Returns          None.
 *
 ******************************************************************************/
void bta_gattc_fill_gatt_db_el(btgatt_db_element_t* p_attr,
                               bt_gatt_db_attribute_type_t type,
                               uint16_t att_handle, uint16_t s_handle,
                               uint16_t e_handle, uint16_t id, const Uuid& uuid,
                               uint8_t prop) {
  p_attr->type = type;
  p_attr->attribute_handle = att_handle;
  p_attr->start_handle = s_handle;
  p_attr->end_handle = e_handle;
  p_attr->id = id;
  p_attr->properties = prop;

  // Permissions are not discoverable using the attribute protocol.
  // Core 5.0, Part F, 3.2.5 Attribute Permissions
  p_attr->permissions = 0;
  p_attr->uuid = uuid;
}

/*******************************************************************************
 * Returns          number of elements inside db from start_handle to end_handle
 ******************************************************************************/
static size_t bta_gattc_get_db_size(const std::list<Service>& services,
                                    uint16_t start_handle,
                                    uint16_t end_handle) {
  if (services.empty()) return 0;

  size_t db_size = 0;

  for (const Service& service : services) {
    if (service.handle < start_handle) continue;

    if (service.end_handle > end_handle) break;

    db_size++;

    for (const Characteristic& charac : service.characteristics) {
      db_size++;

      db_size += charac.descriptors.size();
    }

    db_size += service.included_services.size();
  }

  return db_size;
}

/*******************************************************************************
 *
 * Function         bta_gattc_get_gatt_db_impl
 *
 * Description      copy the server GATT database into db parameter.
 *
 * Parameters       p_srvc_cb: server.
 *                  db: output parameter which will contain GATT database copy.
 *                      Caller is responsible for freeing it.
 *                  count: output parameter which will contain number of
 *                  elements in database.
 *
 * Returns          None.
 *
 ******************************************************************************/
static void bta_gattc_get_gatt_db_impl(tBTA_GATTC_SERV* p_srvc_cb,
                                       uint16_t start_handle,
                                       uint16_t end_handle,
                                       btgatt_db_element_t** db, int* count) {
  VLOG(1) << __func__
          << StringPrintf(": start_handle 0x%04x, end_handle 0x%04x",
                          start_handle, end_handle);

  if (p_srvc_cb->gatt_database.IsEmpty()) {
    *count = 0;
    *db = NULL;
    return;
  }

  size_t db_size = bta_gattc_get_db_size(p_srvc_cb->gatt_database.Services(),
                                         start_handle, end_handle);

  void* buffer = osi_malloc(db_size * sizeof(btgatt_db_element_t));
  btgatt_db_element_t* curr_db_attr = (btgatt_db_element_t*)buffer;

  for (const Service& service : p_srvc_cb->gatt_database.Services()) {
    if (service.handle < start_handle) continue;

    if (service.end_handle > end_handle) break;

    bta_gattc_fill_gatt_db_el(curr_db_attr,
                              service.is_primary ? BTGATT_DB_PRIMARY_SERVICE
                                                 : BTGATT_DB_SECONDARY_SERVICE,
                              0 /* att_handle */, service.handle,
                              service.end_handle, service.handle, service.uuid,
                              0 /* prop */);
    curr_db_attr++;

    for (const Characteristic& charac : service.characteristics) {
      bta_gattc_fill_gatt_db_el(curr_db_attr, BTGATT_DB_CHARACTERISTIC,
                                charac.value_handle, 0 /* s_handle */,
                                0 /* e_handle */, charac.value_handle,
                                charac.uuid, charac.properties);
      btgatt_db_element_t* characteristic = curr_db_attr;
      curr_db_attr++;

      for (const Descriptor& desc : charac.descriptors) {
        bta_gattc_fill_gatt_db_el(
            curr_db_attr, BTGATT_DB_DESCRIPTOR, desc.handle, 0 /* s_handle */,
            0 /* e_handle */, desc.handle, desc.uuid, 0 /* property */);

        if (desc.uuid == Uuid::From16Bit(GATT_UUID_CHAR_EXT_PROP)) {
          characteristic->extended_properties =
              desc.characteristic_extended_properties;
        }
        curr_db_attr++;
      }
    }

    for (const IncludedService& p_isvc : service.included_services) {
      bta_gattc_fill_gatt_db_el(curr_db_attr, BTGATT_DB_INCLUDED_SERVICE,
                                p_isvc.handle, p_isvc.start_handle,
                                0 /* e_handle */, p_isvc.handle, p_isvc.uuid,
                                0 /* property */);
      curr_db_attr++;
    }
  }

  *db = (btgatt_db_element_t*)buffer;
  *count = db_size;
}

/*******************************************************************************
 *
 * Function         bta_gattc_get_gatt_db
 *
 * Description      copy the server GATT database into db parameter.
 *
 * Parameters       conn_id: connection ID which identify the server.
 *                  db: output parameter which will contain GATT database copy.
 *                      Caller is responsible for freeing it.
 *                  count: number of elements in database.
 *
 * Returns          None.
 *
 ******************************************************************************/
void bta_gattc_get_gatt_db(uint16_t conn_id, uint16_t start_handle,
                           uint16_t end_handle, btgatt_db_element_t** db,
                           int* count) {
  tBTA_GATTC_CLCB* p_clcb = bta_gattc_find_clcb_by_conn_id(conn_id);

  LOG_INFO("%s", __func__);
  if (p_clcb == NULL) {
    LOG(ERROR) << "Unknown conn_id=" << loghex(conn_id);
    return;
  }

  if (p_clcb->state != BTA_GATTC_CONN_ST) {
    LOG(ERROR) << "server cache not available, CLCB state=" << +p_clcb->state;
    return;
  }

  if (!p_clcb->p_srcb || p_clcb->p_srcb->pending_discovery.InProgress() ||
      p_clcb->p_srcb->gatt_database.IsEmpty()) {
    LOG(ERROR) << "No server cache available";
    return;
  }

  bta_gattc_get_gatt_db_impl(p_clcb->p_srcb, start_handle, end_handle, db,
                             count);
}