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Commit a8fafc63 authored by Jakub Pawlowski's avatar Jakub Pawlowski Committed by android-build-merger
Browse files

BTA GATT operation queue 

am: 19d0aae5

Change-Id: I771d06a5fb93f7a02a1cad8e70a158c2a523a5d0
parents 85a26c78 19d0aae5

system/bta/Android.bp

+1 −0
Original line number Diff line number Diff line
@@ -62,6 +62,7 @@ cc_library_static { 
        "gatt/bta_gattc_api.cc",

        "gatt/bta_gattc_cache.cc",

        "gatt/bta_gattc_main.cc",

        "gatt/bta_gattc_queue.cc",

        "gatt/bta_gattc_utils.cc",

        "gatt/bta_gatts_act.cc",

        "gatt/bta_gatts_api.cc",

system/bta/BUILD.gn

+1 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ static_library("bta") { 
    "gatt/bta_gattc_cache.cc",

    "gatt/bta_gattc_main.cc",

    "gatt/bta_gattc_utils.cc",

    "gatt/bta_gattc_queue.cc",

    "gatt/bta_gatts_act.cc",

    "gatt/bta_gatts_api.cc",

    "gatt/bta_gatts_main.cc",

system/bta/gatt/bta_gattc_queue.cc

0 → 100644
+192 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2017 The Android Open Source Project

 *

 * 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.

 */



#include "bta_gatt_queue.h"



#include <list>

#include <unordered_map>

#include <unordered_set>



using gatt_operation = BtaGattQueue::gatt_operation;



constexpr uint8_t GATT_READ_CHAR = 1;

constexpr uint8_t GATT_READ_DESC = 2;

constexpr uint8_t GATT_WRITE_CHAR = 3;

constexpr uint8_t GATT_WRITE_DESC = 4;



struct gatt_read_op_data {

  GATT_READ_OP_CB cb;

  void* cb_data;

};



std::unordered_map<uint16_t, std::list<gatt_operation>>

    BtaGattQueue::gatt_op_queue;

std::unordered_set<uint16_t> BtaGattQueue::gatt_op_queue_executing;



void BtaGattQueue::mark_as_not_executing(uint16_t conn_id) {

  gatt_op_queue_executing.erase(conn_id);

}



void BtaGattQueue::gatt_read_op_finished(uint16_t conn_id, tGATT_STATUS status,

                                         uint16_t handle, uint16_t len,

                                         uint8_t* value, void* data) {

  gatt_read_op_data* tmp = (gatt_read_op_data*)data;

  GATT_READ_OP_CB tmp_cb = tmp->cb;

  void* tmp_cb_data = tmp->cb_data;



  osi_free(data);



  mark_as_not_executing(conn_id);

  gatt_execute_next_op(conn_id);



  if (tmp_cb) {

    tmp_cb(conn_id, status, handle, len, value, tmp_cb_data);

    return;

  }

}



struct gatt_write_op_data {

  GATT_WRITE_OP_CB cb;

  void* cb_data;

};



void BtaGattQueue::gatt_write_op_finished(uint16_t conn_id, tGATT_STATUS status,

                                          uint16_t handle, void* data) {

  gatt_write_op_data* tmp = (gatt_write_op_data*)data;

  GATT_WRITE_OP_CB tmp_cb = tmp->cb;

  void* tmp_cb_data = tmp->cb_data;



  osi_free(data);



  mark_as_not_executing(conn_id);

  gatt_execute_next_op(conn_id);



  if (tmp_cb) {

    tmp_cb(conn_id, status, handle, tmp_cb_data);

    return;

  }

}



void BtaGattQueue::gatt_execute_next_op(uint16_t conn_id) {

  APPL_TRACE_DEBUG("%s:", __func__, conn_id);

  if (gatt_op_queue.empty()) {

    APPL_TRACE_DEBUG("%s: op queue is empty", __func__);

    return;

  }



  auto map_ptr = gatt_op_queue.find(conn_id);

  if (map_ptr == gatt_op_queue.end() || map_ptr->second.empty()) {

    APPL_TRACE_DEBUG("%s: no more operations queued for conn_id %d", __func__,

                     conn_id);

    return;

  }



  if (gatt_op_queue_executing.count(conn_id)) {

    APPL_TRACE_DEBUG("%s: can't enqueue next op, already executing", __func__);

    return;

  }



  gatt_op_queue_executing.insert(conn_id);



  std::list<gatt_operation>& gatt_ops = map_ptr->second;



  gatt_operation& op = gatt_ops.front();



  if (op.type == GATT_READ_CHAR) {

    gatt_read_op_data* data =

        (gatt_read_op_data*)osi_malloc(sizeof(gatt_read_op_data));

    data->cb = op.read_cb;

    data->cb_data = op.read_cb_data;

    BTA_GATTC_ReadCharacteristic(conn_id, op.handle, GATT_AUTH_REQ_NONE,

                                 gatt_read_op_finished, data);



  } else if (op.type == GATT_READ_DESC) {

    gatt_read_op_data* data =

        (gatt_read_op_data*)osi_malloc(sizeof(gatt_read_op_data));

    data->cb = op.read_cb;

    data->cb_data = op.read_cb_data;

    BTA_GATTC_ReadCharDescr(conn_id, op.handle, GATT_AUTH_REQ_NONE,

                            gatt_read_op_finished, data);



  } else if (op.type == GATT_WRITE_CHAR) {

    gatt_write_op_data* data =

        (gatt_write_op_data*)osi_malloc(sizeof(gatt_write_op_data));

    data->cb = op.write_cb;

    data->cb_data = op.write_cb_data;

    BTA_GATTC_WriteCharValue(conn_id, op.handle, op.write_type,

                             std::move(op.value), GATT_AUTH_REQ_NONE,

                             gatt_write_op_finished, data);



  } else if (op.type == GATT_WRITE_DESC) {

    gatt_write_op_data* data =

        (gatt_write_op_data*)osi_malloc(sizeof(gatt_write_op_data));

    data->cb = op.write_cb;

    data->cb_data = op.write_cb_data;

    BTA_GATTC_WriteCharDescr(conn_id, op.handle, std::move(op.value),

                             GATT_AUTH_REQ_NONE, gatt_write_op_finished, data);

  }



  gatt_ops.pop_front();

}



void BtaGattQueue::Clean(uint16_t conn_id) {

  gatt_op_queue.erase(conn_id);

  gatt_op_queue_executing.erase(conn_id);

}



void BtaGattQueue::ReadCharacteristic(uint16_t conn_id, uint16_t handle,

                                      GATT_READ_OP_CB cb, void* cb_data) {

  gatt_op_queue[conn_id].push_back({.type = GATT_READ_CHAR,

                                    .handle = handle,

                                    .read_cb = cb,

                                    .read_cb_data = cb_data});

  gatt_execute_next_op(conn_id);

}



void BtaGattQueue::ReadDescriptor(uint16_t conn_id, uint16_t handle,

                                  GATT_READ_OP_CB cb, void* cb_data) {

  gatt_op_queue[conn_id].push_back({.type = GATT_READ_DESC,

                                    .handle = handle,

                                    .read_cb = cb,

                                    .read_cb_data = cb_data});

  gatt_execute_next_op(conn_id);

}



void BtaGattQueue::WriteCharacteristic(uint16_t conn_id, uint16_t handle,

                                       std::vector<uint8_t> value,

                                       tGATT_WRITE_TYPE write_type,

                                       GATT_WRITE_OP_CB cb, void* cb_data) {

  gatt_op_queue[conn_id].push_back({.type = GATT_WRITE_CHAR,

                                    .handle = handle,

                                    .write_type = write_type,

                                    .write_cb = cb,

                                    .write_cb_data = cb_data,

                                    .value = std::move(value)});

  gatt_execute_next_op(conn_id);

}



void BtaGattQueue::WriteDescriptor(uint16_t conn_id, uint16_t handle,

                                   std::vector<uint8_t> value,

                                   tGATT_WRITE_TYPE write_type,

                                   GATT_WRITE_OP_CB cb, void* cb_data) {

  gatt_op_queue[conn_id].push_back({.type = GATT_WRITE_DESC,

                                    .handle = handle,

                                    .write_type = write_type,

                                    .write_cb = cb,

                                    .write_cb_data = cb_data,

                                    .value = std::move(value)});

  gatt_execute_next_op(conn_id);

}

system/bta/hh/bta_hh_le.cc

+27 −186
Original line number Diff line number Diff line
@@ -28,12 +28,9 @@ 


#include <base/bind.h>

#include <base/callback.h>

#include <list>

#include <unordered_map>

#include <unordered_set>

#include <vector>



#include "bta_gatt_api.h"

#include "bta_gatt_queue.h"

#include "bta_hh_co.h"

#include "btm_api.h"

#include "btm_ble_api.h"
@@ -74,160 +71,6 @@ static void bta_hh_le_add_dev_bg_conn(tBTA_HH_DEV_CB* p_cb, bool check_bond); 
//                                       tBTA_HH_RPT_CACHE_ENTRY *p_rpt_cache,

//                                       uint8_t num_rpt);



#define GATT_READ_CHAR 0

#define GATT_READ_DESC 1

#define GATT_WRITE_CHAR 2

#define GATT_WRITE_DESC 3



/* Holds pending GATT operations */

struct gatt_operation {

  uint8_t type;

  uint16_t handle;

  GATT_READ_OP_CB read_cb;

  void* read_cb_data;

  GATT_WRITE_OP_CB write_cb;

  void* write_cb_data;



  /* write-specific fields */

  tGATT_WRITE_TYPE write_type;

  vector<uint8_t> value;

};



// maps connection id to operations waiting for execution

static std::unordered_map<uint16_t, std::list<gatt_operation>> gatt_op_queue;

// contain connection ids that currently execute operations

static std::unordered_set<uint16_t> gatt_op_queue_executing;



static void mark_as_not_executing(uint16_t conn_id) {

  gatt_op_queue_executing.erase(conn_id);

}



static void gatt_op_queue_clean(uint16_t conn_id) {

  gatt_op_queue.erase(conn_id);

  gatt_op_queue_executing.erase(conn_id);

}



static void gatt_execute_next_op(uint16_t conn_id);

GATT_READ_OP_CB act_read_cb = NULL;

void* act_read_cb_data = NULL;

static void gatt_read_op_finished(uint16_t conn_id, tGATT_STATUS status,

                                  uint16_t handle, uint16_t len, uint8_t* value,

                                  void* data) {

  GATT_READ_OP_CB tmp_cb = act_read_cb;

  void* tmp_cb_data = act_read_cb_data;



  act_read_cb = NULL;

  act_read_cb_data = NULL;



  mark_as_not_executing(conn_id);

  gatt_execute_next_op(conn_id);



  if (tmp_cb) {

    tmp_cb(conn_id, status, handle, len, value, tmp_cb_data);

    return;

  }

}



GATT_WRITE_OP_CB act_write_cb = NULL;

void* act_write_cb_data = NULL;

static void gatt_write_op_finished(uint16_t conn_id, tGATT_STATUS status,

                                   uint16_t handle, void* data) {

  GATT_WRITE_OP_CB tmp_cb = act_write_cb;

  void* tmp_cb_data = act_write_cb_data;

  act_write_cb = NULL;

  act_write_cb_data = NULL;



  mark_as_not_executing(conn_id);

  gatt_execute_next_op(conn_id);



  if (tmp_cb) {

    tmp_cb(conn_id, status, handle, tmp_cb_data);

    return;

  }

}



static void gatt_execute_next_op(uint16_t conn_id) {

  APPL_TRACE_DEBUG("%s:", __func__, conn_id);

  if (gatt_op_queue.empty()) {

    APPL_TRACE_DEBUG("%s: op queue is empty", __func__);

    return;

  }



  auto map_ptr = gatt_op_queue.find(conn_id);

  if (map_ptr == gatt_op_queue.end() || map_ptr->second.empty()) {

    APPL_TRACE_DEBUG("%s: no more operations queued for conn_id %d", __func__,

                     conn_id);

    return;

  }



  if (gatt_op_queue_executing.count(conn_id)) {

    APPL_TRACE_DEBUG("%s: can't enqueue next op, already executing", __func__);

    return;

  }



  gatt_op_queue_executing.insert(conn_id);



  std::list<gatt_operation>& gatt_ops = map_ptr->second;



  gatt_operation& op = gatt_ops.front();



  if (op.type == GATT_READ_CHAR) {

    act_read_cb = op.read_cb;

    act_read_cb_data = op.read_cb_data;

    BTA_GATTC_ReadCharacteristic(conn_id, op.handle, GATT_AUTH_REQ_NONE,

                                 gatt_read_op_finished, NULL);



  } else if (op.type == GATT_READ_DESC) {

    act_read_cb = op.read_cb;

    act_read_cb_data = op.read_cb_data;

    BTA_GATTC_ReadCharDescr(conn_id, op.handle, GATT_AUTH_REQ_NONE,

                            gatt_read_op_finished, NULL);



  } else if (op.type == GATT_WRITE_CHAR) {

    act_write_cb = op.write_cb;

    act_write_cb_data = op.write_cb_data;

    BTA_GATTC_WriteCharValue(conn_id, op.handle, op.write_type,

                             std::move(op.value), GATT_AUTH_REQ_NONE,

                             gatt_write_op_finished, NULL);



  } else if (op.type == GATT_WRITE_DESC) {

    act_write_cb = op.write_cb;

    act_write_cb_data = op.write_cb_data;

    BTA_GATTC_WriteCharDescr(conn_id, op.handle, std::move(op.value),

                             GATT_AUTH_REQ_NONE, gatt_write_op_finished, NULL);

  }



  gatt_ops.pop_front();

}



static void gatt_queue_read_op(uint8_t op_type, uint16_t conn_id,

                               uint16_t handle, GATT_READ_OP_CB cb,

                               void* cb_data) {

  gatt_operation op;

  op.type = op_type;

  op.handle = handle;

  op.read_cb = cb;

  op.read_cb_data = cb_data;

  gatt_op_queue[conn_id].push_back(op);

  gatt_execute_next_op(conn_id);

}



static void gatt_queue_write_op(uint8_t op_type, uint16_t conn_id,

                                uint16_t handle, vector<uint8_t> value,

                                tGATT_WRITE_TYPE write_type,

                                GATT_WRITE_OP_CB cb, void* cb_data) {

  gatt_operation op;

  op.type = op_type;

  op.handle = handle;

  op.write_type = write_type;

  op.write_cb = cb;

  op.write_cb_data = cb_data;

  op.value = std::move(value);



  gatt_op_queue[conn_id].push_back(op);

  gatt_execute_next_op(conn_id);

}



#if (BTA_HH_DEBUG == TRUE)

static const char* bta_hh_le_rpt_name[4] = {"UNKNOWN", "INPUT", "OUTPUT",

                                            "FEATURE"};
@@ -643,8 +486,7 @@ static tBTA_HH_STATUS bta_hh_le_read_char_descriptor(tBTA_HH_DEV_CB* p_cb, 
      find_descriptor_by_short_uuid(p_cb->conn_id, char_handle, short_uuid);

  if (!p_desc) return BTA_HH_ERR;



  gatt_queue_read_op(GATT_READ_DESC, p_cb->conn_id, p_desc->handle, cb,

                     cb_data);

  BtaGattQueue::ReadDescriptor(p_cb->conn_id, p_desc->handle, cb, cb_data);

  return BTA_HH_OK;

}
@@ -833,8 +675,8 @@ bool bta_hh_le_write_ccc(tBTA_HH_DEV_CB* p_cb, uint8_t char_handle, 
  uint8_t* ptr = value.data();

  UINT16_TO_STREAM(ptr, clt_cfg_value);



  gatt_queue_write_op(GATT_WRITE_DESC, p_cb->conn_id, p_desc->handle,

                      std::move(value), GATT_WRITE, cb, cb_data);

  BtaGattQueue::WriteDescriptor(p_cb->conn_id, p_desc->handle, std::move(value),

                                GATT_WRITE, cb, cb_data);

  return true;

}
@@ -972,8 +814,8 @@ bool bta_hh_le_set_protocol_mode(tBTA_HH_DEV_CB* p_cb, 
    mode = (mode == BTA_HH_PROTO_BOOT_MODE) ? BTA_HH_LE_PROTO_BOOT_MODE

                                            : BTA_HH_LE_PROTO_REPORT_MODE;



    gatt_queue_write_op(GATT_WRITE_CHAR, p_cb->conn_id,

                        p_cb->hid_srvc.proto_mode_handle, {mode},

    BtaGattQueue::WriteCharacteristic(

        p_cb->conn_id, p_cb->hid_srvc.proto_mode_handle, {mode},

        GATT_WRITE_NO_RSP, write_proto_mode_cb, p_cb);

    return true;

  }
@@ -1035,9 +877,9 @@ void bta_hh_le_get_protocol_mode(tBTA_HH_DEV_CB* p_cb) { 
  p_cb->w4_evt = BTA_HH_GET_PROTO_EVT;



  if (p_cb->hid_srvc.in_use && p_cb->hid_srvc.proto_mode_handle != 0) {

    gatt_queue_read_op(GATT_READ_CHAR, p_cb->conn_id,

                       p_cb->hid_srvc.proto_mode_handle, get_protocol_mode_cb,

                       p_cb);

    BtaGattQueue::ReadCharacteristic(p_cb->conn_id,

                                     p_cb->hid_srvc.proto_mode_handle,

                                     get_protocol_mode_cb, p_cb);

    return;

  }
@@ -1312,7 +1154,7 @@ void bta_hh_gatt_open(tBTA_HH_DEV_CB* p_cb, tBTA_HH_DATA* p_buf) { 


    bta_hh_cb.le_cb_index[BTA_HH_GET_LE_CB_IDX(p_cb->hid_handle)] = p_cb->index;



    gatt_op_queue_clean(p_cb->conn_id);

    BtaGattQueue::Clean(p_cb->conn_id);



#if (BTA_HH_DEBUG == TRUE)

    APPL_TRACE_DEBUG("hid_handle = %2x conn_id = %04x cb_index = %d",
@@ -1548,14 +1390,13 @@ static void bta_hh_le_search_hid_chars(tBTA_HH_DEV_CB* p_dev_cb, 
        break;

      case GATT_UUID_HID_INFORMATION:

        /* only one instance per HID service */

        gatt_queue_read_op(GATT_READ_CHAR, p_dev_cb->conn_id,

                           charac.value_handle, read_hid_info_cb, p_dev_cb);

        BtaGattQueue::ReadCharacteristic(p_dev_cb->conn_id, charac.value_handle,

                                         read_hid_info_cb, p_dev_cb);

        break;

      case GATT_UUID_HID_REPORT_MAP:

        /* only one instance per HID service */

        gatt_queue_read_op(GATT_READ_CHAR, p_dev_cb->conn_id,

                           charac.value_handle, read_hid_report_map_cb,

                           p_dev_cb);

        BtaGattQueue::ReadCharacteristic(p_dev_cb->conn_id, charac.value_handle,

                                         read_hid_report_map_cb, p_dev_cb);

        /* descriptor is optional */

        bta_hh_le_read_char_descriptor(p_dev_cb, charac.value_handle,

                                       GATT_UUID_EXT_RPT_REF_DESCR,
@@ -1666,10 +1507,9 @@ void bta_hh_le_srvc_search_cmpl(tBTA_GATTC_SEARCH_CMPL* p_data) { 
      for (const tBTA_GATTC_CHARACTERISTIC& charac : service.characteristics) {

        if (charac.uuid == Uuid::From16Bit(GATT_UUID_GAP_PREF_CONN_PARAM)) {

          /* read the char value */

          gatt_queue_read_op(GATT_READ_CHAR, p_dev_cb->conn_id,

                             charac.value_handle, read_pref_conn_params_cb,

                             p_dev_cb);



          BtaGattQueue::ReadCharacteristic(p_dev_cb->conn_id,

                                           charac.value_handle,

                                           read_pref_conn_params_cb, p_dev_cb);

          break;

        }

      }
@@ -1834,7 +1674,7 @@ void bta_hh_gatt_close(tBTA_HH_DEV_CB* p_cb, tBTA_HH_DATA* p_data) { 
 ******************************************************************************/

void bta_hh_le_api_disc_act(tBTA_HH_DEV_CB* p_cb) {

  if (p_cb->conn_id != GATT_INVALID_CONN_ID) {

    gatt_op_queue_clean(p_cb->conn_id);

    BtaGattQueue::Clean(p_cb->conn_id);

    BTA_GATTC_Close(p_cb->conn_id);

    /* remove device from background connection if intended to disconnect,

       do not allow reconnection */
@@ -1935,7 +1775,7 @@ void bta_hh_le_get_rpt(tBTA_HH_DEV_CB* p_cb, tBTA_HH_RPT_TYPE r_type, 
  }



  p_cb->w4_evt = BTA_HH_GET_RPT_EVT;

  gatt_queue_read_op(GATT_READ_CHAR, p_cb->conn_id, p_rpt->char_inst_id,

  BtaGattQueue::ReadCharacteristic(p_cb->conn_id, p_rpt->char_inst_id,

                                   read_report_cb, p_cb);

}
@@ -2007,8 +1847,9 @@ void bta_hh_le_write_rpt(tBTA_HH_DEV_CB* p_cb, tBTA_HH_RPT_TYPE r_type, 
  if (p_char && (p_char->properties & GATT_CHAR_PROP_BIT_WRITE_NR))

    write_type = GATT_WRITE_NO_RSP;



  gatt_queue_write_op(GATT_WRITE_CHAR, p_cb->conn_id, p_rpt->char_inst_id,

                      std::move(value), write_type, write_report_cb, p_cb);

  BtaGattQueue::WriteCharacteristic(p_cb->conn_id, p_rpt->char_inst_id,

                                    std::move(value), write_type,

                                    write_report_cb, p_cb);

}



/*******************************************************************************
@@ -2025,8 +1866,8 @@ void bta_hh_le_suspend(tBTA_HH_DEV_CB* p_cb, 
  ctrl_type -= BTA_HH_CTRL_SUSPEND;



  // We don't care about response

  gatt_queue_write_op(GATT_WRITE_CHAR, p_cb->conn_id,

                      p_cb->hid_srvc.control_point_handle, {(uint8_t)ctrl_type},

  BtaGattQueue::WriteCharacteristic(

      p_cb->conn_id, p_cb->hid_srvc.control_point_handle, {(uint8_t)ctrl_type},

      GATT_WRITE_NO_RSP, NULL, NULL);

}

system/bta/include/bta_gatt_queue.h

0 → 100644
+78 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2017 The Android Open Source Project

 *

 * 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.

 */



#include <vector>



#include <list>

#include <unordered_map>

#include <unordered_set>

#include "bta_gatt_api.h"



/* BTA GATTC implementation does not allow for multiple commands queuing. So one

 * client making calls to BTA_GATTC_ReadCharacteristic, BTA_GATTC_ReadCharDescr,

 * BTA_GATTC_WriteCharValue, BTA_GATTC_WriteCharDescr must wait for the callacks

 * before scheduling next operation.

 *

 * Methods below can be used as replacement to BTA_GATTC_* in BTA app. They do

 * queue the commands if another command is currently being executed.

 *

 * If you decide to use those methods in your app, make sure to not mix it with

 * existing BTA_GATTC_* API.

 */

class BtaGattQueue {

 public:

  static void Clean(uint16_t conn_id);

  static void ReadCharacteristic(uint16_t conn_id, uint16_t handle,

                                 GATT_READ_OP_CB cb, void* cb_data);

  static void ReadDescriptor(uint16_t conn_id, uint16_t handle,

                             GATT_READ_OP_CB cb, void* cb_data);

  static void WriteCharacteristic(uint16_t conn_id, uint16_t handle,

                                  std::vector<uint8_t> value,

                                  tGATT_WRITE_TYPE write_type,

                                  GATT_WRITE_OP_CB cb, void* cb_data);

  static void WriteDescriptor(uint16_t conn_id, uint16_t handle,

                              std::vector<uint8_t> value,

                              tGATT_WRITE_TYPE write_type, GATT_WRITE_OP_CB cb,

                              void* cb_data);



  /* Holds pending GATT operations */

  struct gatt_operation {

    uint8_t type;

    uint16_t handle;

    GATT_READ_OP_CB read_cb;

    void* read_cb_data;

    GATT_WRITE_OP_CB write_cb;

    void* write_cb_data;



    /* write-specific fields */

    tGATT_WRITE_TYPE write_type;

    std::vector<uint8_t> value;

  };



 private:

  static void mark_as_not_executing(uint16_t conn_id);

  static void gatt_execute_next_op(uint16_t conn_id);

  static void gatt_read_op_finished(uint16_t conn_id, tGATT_STATUS status,

                                    uint16_t handle, uint16_t len,

                                    uint8_t* value, void* data);

  static void gatt_write_op_finished(uint16_t conn_id, tGATT_STATUS status,

                                     uint16_t handle, void* data);



  // maps connection id to operations waiting for execution

  static std::unordered_map<uint16_t, std::list<gatt_operation>> gatt_op_queue;

  // contain connection ids that currently execute operations

  static std::unordered_set<uint16_t> gatt_op_queue_executing;

};
 
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