axmol/cocos/network/CCDownloader-curl.cpp

/****************************************************************************
 Copyright (c) 2015-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.

 http://www.cocos2d-x.org

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
 in the Software without restriction, including without limitation the rights
 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 copies of the Software, and to permit persons to whom the Software is
 furnished to do so, subject to the following conditions:

 The above copyright notice and this permission notice shall be included in
 all copies or substantial portions of the Software.

 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 ****************************************************************************/

#include "network/CCDownloader-curl.h"

#include <set>

#include <curl/curl.h>
#include <thread>
#include "base/ccUtils.h"
#include "base/ccUTF8.h"
#include "base/CCDirector.h"
#include "base/CCScheduler.h"
#include "platform/CCFileUtils.h"
#include "network/CCDownloader.h"
#include "platform/CCFileStream.h"
#include "md5/md5.h"
#include "yasio/xxsocket.hpp"
#include <inttypes.h>

// **NOTE**
// In the file:
// member function with suffix "Proc" designed called in DownloaderCURL::_threadProc
// member function without suffix designed called in main thread

#define CC_CURL_POLL_TIMEOUT_MS 50 //wait until DNS query done

enum {
	kCheckSumStateSucceed = 1,
	kCheckSumStateFailed = 1 << 1,
};

namespace cocos2d { namespace network {
    using namespace std;

////////////////////////////////////////////////////////////////////////////////
//  Implementation DownloadTaskCURL

    class DownloadTaskCURL : public IDownloadTask
    {
        static int _sSerialId;

        // if more than one task write to one file, cause file broken
        // so use a set to check this situation
        static set<string> _sStoragePathSet;
    public:
        int serialId;

        DownloadTaskCURL()
        : serialId(_sSerialId++), _requestHeaders(nullptr)
        
        {
            _initInternal();
            DLLOG("Construct DownloadTaskCURL %p", this);
        }

        virtual ~DownloadTaskCURL()
        {
            if (_errCode != DownloadTask::ERROR_TASK_DUPLICATED) {
                // if task destroyed unnormally, we should release WritenFileName stored in set.
                // Normally, this action should done when task finished.
                if (_tempFileName.length() && _sStoragePathSet.end() != _sStoragePathSet.find(_tempFileName))
                {
                    DownloadTaskCURL::_sStoragePathSet.erase(_tempFileName);
                }
            }

            if (_fs)
                _fs.close();

			if (_fsMd5)
				_fsMd5.close();

            if (_requestHeaders)
                curl_slist_free_all(_requestHeaders);

            DLLOG("Destruct DownloadTaskCURL %p", this);
        }

        bool init(const string& filename, const string& tempSuffix)
        {
            if (0 == filename.length())
            {
                // data task
                _buf.reserve(CURL_MAX_WRITE_SIZE);
                return true;
            }

            // file task
            _fileName = filename;
            _tempFileName = filename;
            _tempFileName.append(tempSuffix);

            if (_sStoragePathSet.end() != _sStoragePathSet.find(_tempFileName))
            {
                // there is another task uses this storage path
                _errCode = DownloadTask::ERROR_TASK_DUPLICATED;
                _errCodeInternal = 0;
                _errDescription = "More than one download file task write to same file:";
                _errDescription.append(_tempFileName);
                return false;
            }
            _sStoragePathSet.insert(_tempFileName);

            // open temp file handle for write
            bool ret = false;
            do
            {
                string dir;
                size_t found = _tempFileName.find_last_of("/\\");
                if (found == string::npos)
                {
                    _errCode = DownloadTask::ERROR_INVALID_PARAMS;
                    _errCodeInternal = 0;
                    _errDescription = "Can't find dirname in storagePath.";
                    break;
                }

                // ensure directory is exist
                dir = _tempFileName.substr(0, found+1);
                if (!FileUtils::getInstance()->isDirectoryExistInternal(dir))
                {
                    if (!FileUtils::getInstance()->createDirectory(dir))
                    {
                        _errCode = DownloadTask::ERROR_CREATE_DIR_FAILED;
                        _errCodeInternal = 0;
                        _errDescription = "Can't create dir:";
                        _errDescription.append(dir);
                        break;
                    }
                }
                // open file
                _fs.open(_tempFileName, FileStream::Mode::APPEND);
                if (!_fs)
                {
                    _errCode = DownloadTask::ERROR_OPEN_FILE_FAILED;
                    _errCodeInternal = 0;
                    _errDescription = "Can't open file:";
                    _errDescription.append(_tempFileName);
					break;
                }

				// init md5 state
				_checksumFileName = filename + ".chksum";
				_fsMd5.open(_checksumFileName.c_str(), FileStream::Mode::WRITE);
				if (_fsMd5.seek(0, SEEK_END) != sizeof(md5_state_s)) {
					md5_init(&_md5State);
				}
				else {
					_fsMd5.seek(0, SEEK_SET);
					_fsMd5.read(&_md5State, sizeof(md5_state_s));
				}
                ret = true;
            } while (0);

            return ret;
        }

        void cancel()  override
        {
            lock_guard<std::recursive_mutex> lock(_mutex);

            if (!_cancelled) {
                _cancelled = true;
                if (this->_sockfd != -1)
                {
                    ::shutdown(this->_sockfd, SD_BOTH); // may cause curl CURLE_SEND_ERROR(55) or CURLE_RECV_ERROR(56)
                    this->_sockfd = -1;
                }
            }
        }

        curl_socket_t openSocket(curlsocktype propose, curl_sockaddr* addr)
        {
            lock_guard<std::recursive_mutex> lock(_mutex);

            if (!_cancelled) {
                this->_sockfd = ::socket(addr->family, addr->socktype, addr->protocol);
                return this->_sockfd;
            }
            return -1;
        }

		/*
		retval: 0. don't check, 1. check succeed, 2. check failed
		*/
		int checkFileMd5(const std::string& requiredsum, std::string* outsum = nullptr) {
			int status = 0;
			if (!requiredsum.empty()) {
				std::string digest(16, '\0');
				auto state = _md5State; // Excellent, make a copy, don't modify the origin state.
				md5_finish(&state, (md5_byte_t*)&digest.front());
                auto checksum = utils::bin2hex(digest);
				status = requiredsum == checksum ? kCheckSumStateSucceed : kCheckSumStateFailed;

				if (outsum != nullptr)
					*outsum = std::move(checksum);
			}
			return status;
		}

        void initProc()
        {
            lock_guard<std::recursive_mutex> lock(_mutex);
            _initInternal();
        }

        void setErrorProc(int code, int codeInternal, const char *desc)
        {
            lock_guard<std::recursive_mutex> lock(_mutex);
            _errCode = code;
            _errCodeInternal = codeInternal;
            _errDescription = desc;
        }

        size_t writeDataProc(unsigned char *buffer, size_t size, size_t count)
        {
            lock_guard<std::recursive_mutex> lock(_mutex);
            size_t ret = 0;

			auto bytes_transferred = size * count;

            if (_fs)
            {
                ret = _fs.write(buffer, bytes_transferred);// fwrite(buffer, size, count, _fp);
            }
            else
            {
                ret = bytes_transferred;
                auto cap = _buf.capacity();
                auto bufSize = _buf.size();
                if (cap < bufSize + ret)
                {
                    _buf.reserve(bufSize * 2);
                }
                _buf.insert(_buf.end() , buffer, buffer + ret);
            }
            if (ret > 0)
            {
                _bytesReceived += ret;
                _totalBytesReceived += ret;

				::md5_append(&_md5State, buffer, bytes_transferred);
				_fsMd5.seek(0, SEEK_SET);
				_fsMd5.write(&_md5State, sizeof(_md5State));
            }

            curl_easy_getinfo(_curl, CURLINFO_SPEED_DOWNLOAD, &_speed);

            return ret;
        }

    private:
        friend class DownloaderCURL;

        // for lock object instance
        std::recursive_mutex _mutex;

        // header info
        bool    _acceptRanges;
        bool    _headerAchieved;
        int64_t _totalBytesExpected;

        double _speed;
        CURL* _curl;
        curl_socket_t _sockfd = -1; // store the sockfd to support cancel download manually
        bool _cancelled = false;

        string  _header;        // temp buffer for receive header string, only used in thread proc

        curl_slist* _requestHeaders;

        // progress
        int64_t _bytesReceived;
        int64_t _totalBytesReceived;

        // error
        int     _errCode;
        int     _errCodeInternal;
        string  _errDescription;

        // for saving data
        string _fileName;
        string _tempFileName;
		std::string _checksumFileName;
        vector<unsigned char> _buf;
        FileStream _fs;

		// calculate md5 in downloading time support
        FileStream _fsMd5; // store md5 state realtime
		md5_state_s _md5State;
		

        void _initInternal()
        {
            _acceptRanges = (false);
            _headerAchieved = (false);
            _bytesReceived = (0);
            _totalBytesReceived = (0);
            _totalBytesExpected = (0);
            _speed = 0;
            _curl = nullptr;
            _errCode = (DownloadTask::ERROR_NO_ERROR);
            _errCodeInternal = (CURLE_OK);
            _header.resize(0);
            _header.reserve(384);   // pre alloc header string buffer
        }
    };
    int DownloadTaskCURL::_sSerialId;
    set<string> DownloadTaskCURL::_sStoragePathSet;

////////////////////////////////////////////////////////////////////////////////
//  Implementation DownloaderCURL::Impl
    // This class shared by DownloaderCURL and work thread.
    class DownloaderCURL::Impl : public enable_shared_from_this<DownloaderCURL::Impl>
    {
    public:
        DownloaderHints hints;

        Impl()
//        : _thread(nullptr)
        {
            DLLOG("Construct DownloaderCURL::Impl %p", this);
        }

        ~Impl()
        {
            DLLOG("Destruct DownloaderCURL::Impl %p", this);
        }

        void addTask(std::shared_ptr<DownloadTask> task, DownloadTaskCURL* coTask)
        {
			int status = coTask->checkFileMd5(task->checksum);

			if (status & kCheckSumStateSucceed || DownloadTask::ERROR_NO_ERROR != coTask->_errCode)
			{
				_owner->_onDownloadFinished(std::make_pair(task, coTask), status);
			}
			else {
				lock_guard<mutex> lock(_requestMutex);
				_requestQueue.push_back(std::make_pair(task, coTask));
			}
        }

        void run()
        {
            lock_guard<mutex> lock(_threadMutex);
            if (!_thread.joinable())
            {
                std::thread newThread(&DownloaderCURL::Impl::_threadProc, this);
                _thread.swap(newThread);
            }
        }

        void stop()
        { // make sure all task exit properly
            if (!_requestQueue.empty()) {
                lock_guard<mutex> lock(_requestMutex);
                _requestQueue.clear();
            }

            if (!_processSet.empty()) {
                lock_guard<mutex> lock(_processMutex);
                for (auto& task : _processSet)
                    task.first->cancel();
                _processSet.clear();
            }

            if (_thread.joinable())
                _thread.join();
        }

        bool stoped()
        {
            lock_guard<mutex> lock(_threadMutex);
            return !_thread.joinable();
        }

        void getProcessTasks(vector<TaskWrapper>& outList)
        {
            lock_guard<mutex> lock(_processMutex);
            outList.reserve(_processSet.size());
            outList.insert(outList.end(), _processSet.begin(), _processSet.end());
        }

    private:
        static size_t _outputHeaderCallbackProc(void *buffer, size_t size, size_t count, void *userdata)
        {
            int strLen = int(size * count);
            DLLOG("    _outputHeaderCallbackProc: %.*s", strLen, buffer);
            DownloadTaskCURL& coTask = *((DownloadTaskCURL*)(userdata));
            coTask._header.append((const char *)buffer, strLen);
            return strLen;
        }

        static size_t _outputDataCallbackProc(void *buffer, size_t size, size_t count, void *userdata)
        {
//            DLLOG("    _outputDataCallbackProc: size(%ld), count(%ld)", size, count);
            DownloadTaskCURL *coTask = (DownloadTaskCURL*)userdata;

            // If your callback function returns CURL_WRITEFUNC_PAUSE it will cause this transfer to become paused.
            return coTask->writeDataProc((unsigned char *)buffer, size, count);
        }

		static int _progressCallbackProc(void *ptr, double totalToDownload, double nowDownloaded, double totalToUpLoad, double nowUpLoaded)
		{
			DownloaderCURL* downloader = (DownloaderCURL*)ptr;
			downloader->_onDownloadProgress();
			return 0;
		}

        static curl_socket_t _openSocketCallback(DownloadTaskCURL& pTask, curlsocktype propose, curl_sockaddr* addr)
        {
            return pTask.openSocket(propose, addr);
        }

        // this function designed call in work thread
        // the curl handle destroyed in _threadProc
        // handle inited for get header
        CURLcode _initCurlHandleProc(CURL *handle, TaskWrapper& wrapper, bool forContent = false)
        {
            const DownloadTask& task = *wrapper.first;
            DownloadTaskCURL* coTask = wrapper.second;

            /* Resolve host domain to ip */
            std::string internalURL = task.requestURL;
            // Curl_custom_setup(handle, internalURL, (void**)& coTask->_requestHeaders);

            // set url
            curl_easy_setopt(handle, CURLOPT_URL, internalURL.c_str());

            // set write func
            if (forContent)
            {
                curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, _outputDataCallbackProc);
            }
            else
            {
                curl_easy_setopt(handle, CURLOPT_WRITEFUNCTION, _outputHeaderCallbackProc);
            }
            curl_easy_setopt(handle, CURLOPT_WRITEDATA, coTask);

            // curl_easy_setopt(handle, CURLOPT_NOPROGRESS, true);
            // curl_easy_setopt(handle, CURLOPT_XFERINFOFUNCTION, _progressCallbackProc);
            /*curl_easy_setopt(handle, CURLOPT_XFERINFODATA, coTask);*/
			curl_easy_setopt(handle, CURLOPT_NOPROGRESS, false);
			curl_easy_setopt(handle, CURLOPT_PROGRESSDATA, _owner);
			curl_easy_setopt(handle, CURLOPT_PROGRESSFUNCTION, _progressCallbackProc);

            curl_easy_setopt(handle, CURLOPT_FAILONERROR, true);
            curl_easy_setopt(handle, CURLOPT_NOSIGNAL, 1L);

            curl_easy_setopt(handle, CURLOPT_OPENSOCKETFUNCTION, _openSocketCallback);
            curl_easy_setopt(handle, CURLOPT_OPENSOCKETDATA, coTask);

            if (forContent)
            {
                /** if server acceptRanges and local has part of file, we continue to download **/
                if (coTask->_acceptRanges && coTask->_totalBytesReceived > 0)
                {
                    char buf[128];
                    sprintf(buf, "%" PRId64 "-", coTask->_totalBytesReceived);
                    curl_easy_setopt(handle, CURLOPT_RANGE, buf);
                    curl_easy_setopt(handle, CURLOPT_RESUME_FROM_LARGE,(curl_off_t)coTask->_totalBytesReceived);
                }
            }
            else
            {
                // get header options
                curl_easy_setopt(handle, CURLOPT_HEADER, 1);
                curl_easy_setopt(handle, CURLOPT_NOBODY, 1);
            }

//            if (!sProxy.empty())
//            {
//                curl_easy_setopt(curl, CURLOPT_PROXY, sProxy.c_str());
//            }
            if (hints.timeoutInSeconds)
            {
                curl_easy_setopt(handle, CURLOPT_CONNECTTIMEOUT, hints.timeoutInSeconds);
            }

            static const long LOW_SPEED_LIMIT = 1;
            static const long LOW_SPEED_TIME = 10;
            curl_easy_setopt(handle, CURLOPT_LOW_SPEED_LIMIT, LOW_SPEED_LIMIT);
            curl_easy_setopt(handle, CURLOPT_LOW_SPEED_TIME, LOW_SPEED_TIME);

            curl_easy_setopt(handle, CURLOPT_SSL_VERIFYHOST, 0);
            curl_easy_setopt(handle, CURLOPT_SSL_VERIFYPEER, 0);

            static const int MAX_REDIRS = 5;
            if (MAX_REDIRS)
            {
                curl_easy_setopt(handle, CURLOPT_FOLLOWLOCATION, true);
                curl_easy_setopt(handle, CURLOPT_MAXREDIRS, MAX_REDIRS);
            }

            coTask->_curl = handle;

            return CURLE_OK;
        }

        // get header info, if success set handle to content download state
        bool _getHeaderInfoProc(CURL *handle, TaskWrapper& wrapper)
        {
            DownloadTaskCURL& coTask = *wrapper.second;
            CURLcode rc = CURLE_OK;
            do
            {
                long httpResponseCode = 0;
                rc = curl_easy_getinfo(handle, CURLINFO_RESPONSE_CODE, &httpResponseCode);
                if (CURLE_OK != rc)
                {
                    break;
                }
                // Comment follow code to support ftp
                /*if (200 != httpResponseCode)
                {
                    char buf[256] = {0};
                    sprintf(buf
                            , "When request url(%s) header info, return unexcept http response code(%ld)"
                            , wrapper.first->requestURL.c_str()
                            , httpResponseCode);
                    coTask.setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, CURLE_OK, buf);
                }*/

//                curl_easy_getinfo(handle, CURLINFO_EFFECTIVE_URL, &effectiveUrl);
//                curl_easy_getinfo(handle, CURLINFO_CONTENT_TYPE, &contentType);
                double contentLen = 0;
                rc = curl_easy_getinfo(handle, CURLINFO_CONTENT_LENGTH_DOWNLOAD, &contentLen);
                if (CURLE_OK != rc)
                {
                    break;
                }

                // std::transform(coTask._header.begin(), coTask._header.end(), coTask._header.begin(), ::toupper);
                bool acceptRanges = true; // (string::npos != coTask._header.find("ACCEPT-RANGES")) ? true : false;

                // get current file size
                int64_t fileSize = 0;
                if (acceptRanges && coTask._tempFileName.length())
                {
                    fileSize = FileUtils::getInstance()->getFileSize(coTask._tempFileName);
                }

                // set header info to coTask
                lock_guard<std::recursive_mutex> lock(coTask._mutex);
                coTask._totalBytesExpected = (int64_t)contentLen;
                coTask._acceptRanges = acceptRanges;
                if (acceptRanges && fileSize > 0)
                {
                    coTask._totalBytesReceived = fileSize;
                }
                coTask._headerAchieved = true;
            } while (0);

            if (CURLE_OK != rc)
            {
                coTask.setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, rc, curl_easy_strerror(rc));
            }
            return coTask._headerAchieved;
        }

        void _threadProc()
        {
            DLLOG("++++DownloaderCURL::Impl::_threadProc begin %p", this);
            // the holder prevent DownloaderCURL::Impl class instance be destruct in main thread
            auto holder = this->shared_from_this();
            auto thisThreadId = this_thread::get_id();
            uint32_t countOfMaxProcessingTasks = this->hints.countOfMaxProcessingTasks;
            // init curl content
            CURLM* curlmHandle = curl_multi_init();
            unordered_map<CURL*, TaskWrapper> coTaskMap;
            int runningHandles = 0;
            CURLMcode mcode = CURLM_OK;
            int rc = 0;                 // select return code

            do
            {
                // check the thread should exit or not
                {
                    lock_guard<mutex> lock(_threadMutex);
                    // if the Impl stoped, this->_thread.reset will be called, thus _thread.get_id() not equal with thisThreadId
                    if (thisThreadId != this->_thread.get_id())
                    {
                        break;
                    }
                }

                if (runningHandles)
                {
                    // get timeout setting from multi-handle
                    long timeoutMS = -1;
                    curl_multi_timeout(curlmHandle, &timeoutMS);

                    if(timeoutMS < 0)
                    {
                        timeoutMS = 1000;
                    }

                    /* get file descriptors from the transfers */
                    fd_set fdread;
                    fd_set fdwrite;
                    fd_set fdexcep;
                    int maxfd = -1;

                    FD_ZERO(&fdread);
                    FD_ZERO(&fdwrite);
                    FD_ZERO(&fdexcep);

                    mcode = curl_multi_fdset(curlmHandle, &fdread, &fdwrite, &fdexcep, &maxfd);
                    if (CURLM_OK != mcode)
                    {
                        break;
                    }

                    // do wait action
                    if(maxfd == -1)
                    {
                        this_thread::sleep_for(chrono::milliseconds(CC_CURL_POLL_TIMEOUT_MS));
                        rc = 0;
                    }
                    else
                    {
                        struct timeval timeout;

                        timeout.tv_sec = timeoutMS / 1000;
                        timeout.tv_usec = (timeoutMS % 1000) * 1000;

                        rc = select(maxfd+1, &fdread, &fdwrite, &fdexcep, &timeout);
                    }

                    if (rc < 0)
                    {
                        DLLOG("    _threadProc: select return unexpect code: %d", rc);
                    }
                }

                if (!coTaskMap.empty())
                {
                    mcode = CURLM_CALL_MULTI_PERFORM;
                    while(CURLM_CALL_MULTI_PERFORM == mcode)
                    {
                        mcode = curl_multi_perform(curlmHandle, &runningHandles);
                    }
                    if (CURLM_OK != mcode)
                    {
                        break;
                    }

                    struct CURLMsg *m;
                    do {
                        int msgq = 0;
                        m = curl_multi_info_read(curlmHandle, &msgq);
                        if(m && (m->msg == CURLMSG_DONE))
                        {
                            CURL *curlHandle = m->easy_handle;
                            CURLcode errCode = m->data.result;

                            TaskWrapper wrapper = coTaskMap[curlHandle];

                            // remove from multi-handle
                            curl_multi_remove_handle(curlmHandle, curlHandle);
                            bool reinited = false;
                            do
                            {
                                if (CURLE_OK != errCode)
                                {
                                    wrapper.second->setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, errCode, curl_easy_strerror(errCode));
                                    break;
                                }

                                // if the task is content download task, cleanup the handle
                                if (wrapper.second->_headerAchieved)
                                {
                                    break;
                                }

                                // the task is get header task
                                // first, we get info from response
                                if (!_getHeaderInfoProc(curlHandle, wrapper))
                                {
                                    // the error info has been set in _getHeaderInfoProc
                                    break;
                                }

                                // after get header info success
                                // wrapper.second->_totalBytesReceived inited by local file size
                                // if the local file size equal with the content size from header, the file has downloaded finish
                                if (wrapper.second->_totalBytesReceived &&
                                    wrapper.second->_totalBytesReceived == wrapper.second->_totalBytesExpected)
                                {
                                    // the file has download complete
                                    // break to move this task to finish queue
                                    break;
                                }
                                // reinit curl handle for download content
                                curl_easy_reset(curlHandle);
                                auto error = _initCurlHandleProc(curlHandle, wrapper, true);
                                if (error != CURLE_OK)
                                {
                                    wrapper.second->setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, error, curl_easy_strerror(error));
                                    break;
                                }
                                mcode = curl_multi_add_handle(curlmHandle, curlHandle);
                                if (CURLM_OK != mcode)
                                {
                                    wrapper.second->setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, mcode, curl_multi_strerror(mcode));
                                    break;
                                }
                                reinited = true;
                            } while (0);

                            if (reinited)
                            {
                                continue;
                            }
                            curl_easy_cleanup(curlHandle);
                            DLLOG("    _threadProc task clean cur handle :%p with errCode:%d",  curlHandle, errCode);

                           // remove from coTaskMap
                            coTaskMap.erase(curlHandle);

                            // remove from _processSet
                            {
                                lock_guard<mutex> lock(_processMutex);
                                if (_processSet.end() != _processSet.find(wrapper)) {
                                    _processSet.erase(wrapper);
                                }
                            }

							_owner->_onDownloadFinished(std::move(wrapper));
                        }
                    } while(m);
                }

                // process tasks in _requestList
                auto size = coTaskMap.size();
                while (0 == countOfMaxProcessingTasks || size < countOfMaxProcessingTasks)
                {
                    // get task wrapper from request queue
                    TaskWrapper wrapper;
                    {
                        lock_guard<mutex> lock(_requestMutex);
                        if (!_requestQueue.empty())
                        {
                            wrapper = _requestQueue.front();
                            _requestQueue.pop_front();
                        }
                    }

                    // if request queue is empty, the wrapper.first is nullptr
                    if (! wrapper.first)
                    {
                        break;
                    }

                    wrapper.second->initProc();

                    // create curl handle from task and add into curl multi handle
                    CURL* curlHandle = curl_easy_init();

                    if (nullptr == curlHandle)
                    {
						wrapper.second->setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, 0, "Alloc curl handle failed.");
						_owner->_onDownloadFinished(std::move(wrapper));
                        continue;
                    }

                    // init curl handle for get header info
                    _initCurlHandleProc(curlHandle, wrapper);

                    // add curl handle to process list
                    mcode = curl_multi_add_handle(curlmHandle, curlHandle);
                    if (CURLM_OK != mcode)
                    {
						wrapper.second->setErrorProc(DownloadTask::ERROR_IMPL_INTERNAL, mcode, curl_multi_strerror(mcode));
						_owner->_onDownloadFinished(std::move(wrapper));
                        continue;
                    }

                    DLLOG("    _threadProc task create curl handle:%p", curlHandle);
                    coTaskMap[curlHandle] = wrapper;
                    lock_guard<mutex> lock(_processMutex);
                    _processSet.insert(wrapper);
                }
            } while (!coTaskMap.empty());

            curl_multi_cleanup(curlmHandle);
            DLLOG("----DownloaderCURL::Impl::_threadProc end");
        }

        thread _thread;
        deque<TaskWrapper>  _requestQueue;
        set<TaskWrapper>    _processSet;
        // deque<TaskWrapper>  _finishedQueue;

        mutex _threadMutex;
        mutex _requestMutex;
        mutex _processMutex;
        mutex _finishedMutex;

public:
		DownloaderCURL* _owner = nullptr;
    };


////////////////////////////////////////////////////////////////////////////////
//  Implementation DownloaderCURL
    DownloaderCURL::DownloaderCURL(const DownloaderHints& hints)
    : _impl(std::make_shared<Impl>())
    , _currTask(nullptr)
    {
        DLLOG("Construct DownloaderCURL %p", this);
        _impl->hints = hints;
		_impl->_owner = this;

        _transferDataToBuffer = [this](void *buf, int64_t len)->int64_t
        {
            DownloadTaskCURL& coTask = *_currTask;
            int64_t dataLen = coTask._buf.size();
            if (len < dataLen)
            {
                return 0;
            }

            memcpy(buf, coTask._buf.data(), dataLen);
            coTask._buf.resize(0);
            return dataLen;
        };
    }

    DownloaderCURL::~DownloaderCURL()
    {
        _impl->stop();
        DLLOG("Destruct DownloaderCURL %p", this);
    }

    IDownloadTask *DownloaderCURL::createCoTask(std::shared_ptr<DownloadTask>& task)
    {
        DownloadTaskCURL *coTask = new (std::nothrow) DownloadTaskCURL;
        coTask->init(task->storagePath, _impl->hints.tempFileNameSuffix);

        DLLOG("    DownloaderCURL: createTask: Id(%d)", coTask->serialId);

        _impl->addTask(task, coTask);
        _impl->run();
		
        // _scheduler->resumeTarget(this);
        return coTask;
    }

	void DownloaderCURL::_onDownloadFinished(TaskWrapper&& wrapper, int checkState)
	{
		const DownloadTask& task = *wrapper.first;
		DownloadTaskCURL& coTask = *wrapper.second;

		// if there is bytesReceived, call progress update first
		if (coTask._bytesReceived)
		{
			_currTask = &coTask;
			task.progressInfo.bytesReceived = coTask._bytesReceived;
			task.progressInfo.totalBytesReceived = coTask._totalBytesReceived;
			task.progressInfo.totalBytesExpected = coTask._totalBytesExpected;
			task.progressInfo.speedInBytes = coTask._speed;
			onTaskProgress(task,
				_transferDataToBuffer);
			coTask._bytesReceived = 0;
			_currTask = nullptr;
		}

		// if file task, close file handle and rename file if needed
		if (coTask._fs)
		{
			do
			{
                auto pFileUtils = FileUtils::getInstance();
				coTask._fs.close();
				coTask._fsMd5.close();

				if (checkState & kCheckSumStateSucceed) // No need download 
				{
					FileStream fsOrigin;
					if (fsOrigin.open(coTask._fileName, FileStream::Mode::READ)) {
						task.progressInfo.totalBytesExpected = fsOrigin.seek(0, SEEK_END);
						task.progressInfo.bytesReceived = task.progressInfo.totalBytesExpected;
						task.progressInfo.totalBytesReceived = task.progressInfo.totalBytesExpected;
						task.progressInfo.speedInBytes = task.progressInfo.totalBytesExpected;
						coTask._errCode = DownloadTask::ERROR_NO_ERROR;
						coTask._errCodeInternal = 0;
						coTask._errDescription = "";

                        pFileUtils->removeFile(coTask._tempFileName);

						onTaskProgress(task,
							_transferDataToBuffer);
					}
					else {
						coTask._errCode = DownloadTask::ERROR_ORIGIN_FILE_MISSING;
						coTask._errCodeInternal = 0;
						coTask._errDescription = "Check file md5 succeed, but the origin file is missing!";
						pFileUtils->removeFile(coTask._checksumFileName);
						pFileUtils->removeFile(coTask._tempFileName);
					}
					break;
				}

				if (coTask._fileName.empty() || DownloadTask::ERROR_NO_ERROR != coTask._errCode)
				{
                    if (coTask._errCodeInternal == CURLE_RANGE_ERROR) {
                        // If CURLE_RANGE_ERROR, means the server not support resume from download.
                        pFileUtils->removeFile(coTask._checksumFileName);
                        pFileUtils->removeFile(coTask._tempFileName);
                    }
					break;
				}

				// if file already exist, remove it
				if (pFileUtils->isFileExistInternal(coTask._fileName))
				{
					if (!pFileUtils->removeFile(coTask._fileName))
					{
						coTask._errCode = DownloadTask::ERROR_REMOVE_FILE_FAILED;
						coTask._errCodeInternal = errno;
						coTask._errDescription = "Can't remove old file: ";
						coTask._errDescription.append(coTask._fileName);
						break;
					}
				}


				// Try check sum with md5 digest
				std::string realMd5;
				if (coTask.checkFileMd5(task.checksum, &realMd5) & kCheckSumStateFailed) {
					coTask._errCode = DownloadTask::ERROR_CHECK_SUM_FAILED;
					coTask._errCodeInternal = 0;
					coTask._errDescription = StringUtils::format("Check file: %s md5 failed, required:%s, real:%s", coTask._fileName.c_str(),
						task.checksum.c_str(),
						realMd5.c_str());

                    pFileUtils->removeFile(coTask._checksumFileName);
                    pFileUtils->removeFile(coTask._tempFileName);
					break;
				}

				// remove file firstly, confirm rename file work fine.
                pFileUtils->removeFile(coTask._fileName);
				if (pFileUtils->renameFile(coTask._tempFileName, coTask._fileName))
				{
					// success, remove storage from set
					DownloadTaskCURL::_sStoragePathSet.erase(coTask._tempFileName);
					break;
				}

				// failed
				coTask._errCode = DownloadTask::ERROR_RENAME_FILE_FAILED;
				coTask._errCodeInternal = 0;
				coTask._errDescription = "Can't renamefile from: ";
				coTask._errDescription.append(coTask._tempFileName);
				coTask._errDescription.append(" to: ");
				coTask._errDescription.append(coTask._fileName);
			} while (0);

		}

		// needn't lock coTask here, because tasks has removed form _impl
		onTaskFinish(task, coTask._errCode, coTask._errCodeInternal, coTask._errDescription, coTask._buf);
		DLLOG("    DownloaderCURL: finish Task: Id(%d)", coTask.serialId);
	}

    void DownloaderCURL::_onDownloadProgress()
    {
        vector<TaskWrapper> tasks;

        // update processing tasks
        _impl->getProcessTasks(tasks);
        for (auto& wrapper : tasks)
        {
            const DownloadTask& task = *wrapper.first;
            DownloadTaskCURL& coTask = *wrapper.second;

            lock_guard<std::recursive_mutex> lock(coTask._mutex);
            if (coTask._bytesReceived)
            {
                _currTask = &coTask;
                task.progressInfo.bytesReceived = coTask._bytesReceived;
                task.progressInfo.totalBytesReceived = coTask._totalBytesReceived;
                task.progressInfo.totalBytesExpected = coTask._totalBytesExpected;
                task.progressInfo.speedInBytes = coTask._speed;
                onTaskProgress(task,
                               _transferDataToBuffer);
                _currTask = nullptr;
                coTask._bytesReceived = 0;
            }
        }
        tasks.resize(0);
    }

}}  //  namespace cocos2d::network