大家知道百度网盘下载对于非会员是有下载限速的, 最大速度基本上维持在 100kB/s以内,要下个电影啥的,那就有得等了. 之前还可以把网盘里的文件链接解析出来放到Uget或迅雷之类的下载工具里去多线程下载, 但是现在百度的文件服务器对ua做了校验, 没找到好用的可编辑http header的下载工具, 于是自己动手写一个了.基本上可以充分利用已有的带宽

download_demo.gif

PS: 请自行安装swoole拓展和Guzzle http包.
直接上代码吧:

<?php

include 'vendor/autoload.php';
// $service = new Service('http://peterq.cn/movie/api/video_redirect?fid=543468589252145', __DIR__);
$service = new Service('http://peterq.cn/movie/api/video_redirect?fid=364402848596280', __DIR__);
$service->start();

use GuzzleHttp\Client;


class Service
{

    /**
     * @var Client;
     */
    protected $client;

    protected $worker_pool; // 下载进程池

    protected $available_worker_queue; // 可用的进程队列

    protected $worker_number = 16; // 定义需要开多少个进程, 文件较小时, 并不一定全部用得上, 取决于你的分片大小

    protected $started = false; // 是否已经开始下载

    protected $url; // 下载链接

    protected $length; // 文件大小

    protected $dir; // 保存目录

    protected $filename; // 文件绝对路径

    protected $downloaded = 0; // 已下载字节数

    protected $speedArr = []; // 用来计算下载速度的数组

    protected $distributed = 0; // 对于要下载的文件, 已经分配到哪个位置了

    public function __construct($url, $dir)
    {
        $this->url = $url;
        $this->dir = realpath($dir);
    }

    public function start()
    {
        if ($this->started) return;
        $this->available_worker_queue = new SplQueue();
        $this->started = true;
        // 创建客户端
        $this->client = new Client([
            'headers' => [
                "Accept"           => "application/json, text/javascript, text/html, */*; q=0.01",
                "Accept-Encoding"  => "gzip, deflate, sdch",
                "Accept-Language"  => "en-US,en;q=0.8,zh-CN;q=0.6,zh;q=0.4,zh-TW;q=0.2",
                "Referer"          => "http://pan.baidu.com/disk/home",
                "X-Requested-With" => "XMLHttpRequest",
                "User-Agent"       => "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.108 Safari/537.36",
                "Connection"       => "keep-alive",
            ],
        ]);
        // 设置进程名称
        swoole_set_process_name('download-master');
        echo 'master pid:' . posix_getpid() . PHP_EOL;
        // 创建多个下载进程
        for ($i = 0; $i < $this->worker_number; $i++) {
            $process = $this->createProcess($i);
            $this->worker_pool[$i] = $process;
            // 通信通道加入事件轮训, 进行异步通信
            swoole_event_add($process->pipe, function ($pipe) use ($process) {
                $data = $process->read();
                $data = unserialize($data);
                $this->handleChildMessage($process, $data['type'], $data['data']);
            });
            $process->start();
            $this->available_worker_queue->enqueue($process);
        }

        // 子进程退出回收
        swoole_process::signal(SIGCHLD, function ($sig) {
            static $exited = 0;
            // 必须为false，非阻塞模式
            while ($ret = swoole_process::wait(false)) {
                echo "child process exited, PID={$ret['pid']}\n";
                $exited++;
                if ($exited == count($this->worker_pool)) exit();
            }
        });

        $this->initDownload();

    }

    // 初始化下载
    protected function initDownload()
    {
        $resp = $this->client->request('GET', $this->url, [
            'stream'          => true,
            'read_timeout'    => 10,
        ]);
        // 处理重定向
        while (in_array($resp->getStatusCode(), [301, 302])) {
            $this->url = $resp->getBody()->read(1024);
            dump('redirect: ' . $this->url);
            $resp = $this->client->request('GET', $this->url, [
                'stream'          => true,
                'read_timeout'    => 10,
            ]);
        }
        if (!$resp->getHeader('Content-Disposition')) {
            dump('not a file download url');
        }
        $this->length = intval($resp->getHeader('Content-Length')[0]);
        $fname = $resp->getHeader('Content-Disposition')[0];
        $fname = substr($fname, strpos($fname, 'filename=') + strlen('filename='));
        $fname = urldecode($fname);
        $this->filename = $this->dir . '/' . $fname;
        dump([
            '文件' => $this->filename,
            '大小' => round($this->length / 1024 / 1024, 2) . 'MB'
        ]);
        file_put_contents($this->filename, '');
        $this->download();
    }

    // 启动下载
    protected function download()
    {
        while (
            $this->distributed < $this->length
            && $this->available_worker_queue->count()
            && $process = $this->available_worker_queue->dequeue()) {
            $this->distributeSegment($process);
        }
    }

    // 分配下一块区间给一个进程
    protected function distributeSegment($process)
    {
        // 分成 1 MB 一个段去下载
        $size = 1 * 1024 * 1024;
        $process->write(serialize([
            'type' => 'new-segment',
            'data' => [
                'url' => $this->url,
                'file' => $this->filename,
                'start' => $this->distributed,
                'length' => min($size, $this->length - $this->distributed),
            ]
        ]));
        $this->distributed += $size;
    }

    // 进程间通信处理
    protected function handleChildMessage($process, $type, $data)
    {
        method_exists($this, 'on' . ucfirst($type)) and $this->{'on' . ucfirst($type)}($process, $data);
    }

    // 当下载进程下载一小块时, 通过此回调通知master进程
    protected function onRange(swoole_process $process, $data)
    {
        $this->downloaded += $data;
        static $lastClearTime = 0;
        $time = time();
        $this->speedArr[$time] = $this->speedArr[$time] ?? 0;
        $this->speedArr[$time] += $data;
        // 取过去 5 秒作为平均速度 作为速度显示, 粗略计算, 并不准确
        if ($time > $lastClearTime) {
            $lastClearTime = $time;
            foreach ($this->speedArr as $t => $size) {
                if ($t < $time - 5) unset($this->speedArr[$t]);
            }
        }
        $speed = array_sum($this->speedArr) / count($this->speedArr);
        $percent = $this->downloaded / $this->length * 100;
        $percent = round($percent, 2);
        $size = humanSize($this->downloaded);
        $speed = humanSize($speed);
        echo "\r\033[2K" . "已下载: $size, $percent%; 当前速度：　$speed/s";
    }

    // 当分配给下载进程的下载任务完成时执行的回调
    protected function onTaskFinished($process, $data)
    {
        if ($this->distributed < $this->length)
            $this->distributeSegment($process);
        else {
            $this->available_worker_queue->enqueue($process);
            if ($this->available_worker_queue->count() == count($this->worker_pool)) {
                dump('文件下载完成');
                foreach ($this->worker_pool as $worker) {
                    $worker->write(serialize([
                        'type' => 'exit', 'data' => ''
                    ]));
                }
            }
        }
    }

    // 创建下载进程
    protected function createProcess($index = null)
    {
        $process = new swoole_process(function (swoole_process $process) use ($index) {
            swoole_set_process_name('download worker' . $index);
            echo sprintf('worker:%s, pid:%s', $index, posix_getpid()) . PHP_EOL;
            $downloader = null;
            // 通信通道加入事件轮训, 进行异步通信
            swoole_event_add($process->pipe, function ($pipe) use ($process, &$downloader) {
                $data = $process->read();
                $data = unserialize($data);
                $type = $data['type'];
                $data = $data['data'];
                // 这里会阻塞掉, 后续改进
                if ($type == 'new-segment') {
                    $downloader = new Downloader($process, $this->client, $data['url'], $data['file'], $data['start'], $data['length']);
                    $downloader->download();
                    $process->write(serialize([
                        'type' => 'taskFinished',
                        'data' => ''
                    ]));
                    $downloader = null;
                    return;
                }
                if ($type == 'exit') exit(0);
            });
        }, false, 2);

        return $process;
    }
}


// 下载器类
class Downloader
{

    protected $client; // guzzle实例

    protected $process; // 当前进程实例

    protected $file; // 文件名

    protected $url;

    protected $start; // 开始位置

    protected $length; // 下载长度

    protected $offset; // 已经下到哪一个位置了

    public function __construct(swoole_process $process, Client $client, $url, $file, $start, $length)
    {
        $this->process = $process;
        $this->client = $client;
        $this->url = $url;
        $this->file = $file;
        $this->start = $start;
        $this->length = $length;
    }


    public function download()
    {
        $this->offset = $this->start;
        $res = fopen($this->file, 'rb+');
        fseek($res, $this->start, SEEK_SET);
        $resp = $this->client->request('GET', $this->url, [
            'stream' => true,
            'headers' => [
                'Range' => 'bytes=' . $this->start . '-' . ($this->start + $this->length)
            ]
        ]);
        $loaded = 0;
        while (!$resp->getBody()->eof()) {
            // 5 kb 的下载
            $size = 1024 * 5;
            $data = $resp->getBody()->read($size);
            $loaded += strlen($data);
            fwrite($res, $data);
            $this->process->write(serialize([
                'type' => 'range',
                'data' => strlen($data)
            ]));
            if ($loaded >= $this->length) break; // eof 貌似不起作用，　手动退出
        }
        fclose($res);
        dump($this->length / 1024 / 1024 . 'MB下载完成');
    }
}

// 把文件大小从字节转换为合适的单位
function humanSize($size) {
    $units = ['B', 'KB', 'MB', 'GB'];
    foreach ($units as $unit) {
        if ($size > 1024)
            $size /= 1024;
        else break;
    }
    return round($size, 2) . $unit;
}