php使用curl下载指定大小的文件实例代码

public function callFunction($url, $postData, $method, header=''){  $maxRetryTimes = 3;  $curl = curl_init();  /******初始化请求参数start******/  if(strtoupper($method) !== 'GET' && $postData){    curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($postData));  }elseif (strtoupper($method) === 'GET' && $postData){    $url .= '?'. http_build_query($postData);  }  /******初始化请求参数end******/  curl_setopt_array($curl, array(    CURLOPT_URL => $url,    CURLOPT_TIMEOUT => 10,    CURLOPT_NOBODY => 0,    CURLOPT_RETURNTRANSFER => 1  ));  if(method == 'POST'){    curl_setopt($curl, CURLOPT_POST, true);  }  if(false == empty()){    curl_setopt($curl, CURLOPT_HTTPHEADER, $header);  }  $response = false;  while(($response === false) && (--$maxRetryTimes > 0)){    $response = trim(curl_exec($curl));  }  return $response;}

$ch = curl_init();$options = array(CURLOPT_URL    => 'http://www.php.net/',CURLOPT_HEADER    => false,CURLOPT_HEADERFUNCTION  => 'on_curl_header',CURLOPT_WRITEFUNCTION  => 'on_curl_write');

function on_curl_write($ch, $data){  $pid = getmypid();  $downloadSizeRecorder = DownloadSizeRecorder::getInstance($pid);  $bytes = strlen($data);  $downloadSizeRecorder->downloadData .= $data;  $downloadSizeRecorder->downloadedFileSize += $bytes;//  error_log(' on_curl_write '.$downloadSizeRecorder->downloadedFileSize." > {$downloadSizeRecorder->maxSize} /n", 3, '/tmp/hyb.log');  //确保已经下载的内容略大于最大限制  if (($downloadSizeRecorder->downloadedFileSize - $bytes) > $downloadSizeRecorder->maxSize) {    return false;  }  return $bytes; //这个不正确的返回，将会报错，中断下载 "errno":23,"errmsg":"Failed writing body (0 != 16384)"}

class DownloadSizeRecorder{  const ERROR_FAILED_WRITING = 23; //Failed writing body  public $downloadedFileSize;  public $maxSize;  public $pid;  public $hasOverMaxSize;  public $fileFullName;  public $downloadData;  private static $selfInstanceList = array();  public static function getInstance($pid)  {    if(!isset(self::$selfInstanceList[$pid])){      self::$selfInstanceList[$pid] = new self($pid);    }    return self::$selfInstanceList[$pid];  }  private function __construct($pid)  {    $this->pid = $pid;    $this->downloadedFileSize = 0;    $this->fileFullName = '';    $this->hasOverMaxSize = false;    $this->downloadData = '';  }  /**   * 保存文件   */  public function saveMaxSizeData2File(){    if(empty($resp_data)){      $resp_data = $this->downloadData;    }    $fileFullName = '/tmp/http_'.$this->pid.'_'.time()."_{$this->maxSize}.download";    if($resp_data && strlen($resp_data)>0)    {      list($headerOnly, $bodyOnly) = explode("/r/n/r/n", $resp_data, 2);      $saveDataLenth = ($this->downloadedFileSize < $this->maxSize) ? $this->downloadedFileSize : $this->maxSize;      $needSaveData = substr($bodyOnly, 0, $saveDataLenth);      if(empty($needSaveData)){        return;      }      file_put_contents($fileFullName, $needSaveData);      if(file_exists($fileFullName)){        $this->fileFullName = $fileFullName;      }    }  }  /**   * 返回文件的md5   * @return string   */  public function returnFileMd5(){    $md5 = '';    if(file_exists($this->fileFullName)){      $md5 = md5_file($this->fileFullName);    }    return $md5;  }  /**   * 返回已下载的size   * @return int   */  public function returnSize(){    return ($this->downloadedFileSize < $this->maxSize) ? $this->downloadedFileSize : $this->maxSize;  }  /**   * 删除下载的文件   */  public function deleteFile(){    if(file_exists($this->fileFullName)){      unlink($this->fileFullName);    }  }}

……curl_setopt($ch, CURLOPT_WRITEFUNCTION, 'on_curl_write');//设置回调函数……$pid = getmypid();$downloadSizeRecorder = DownloadSizeRecorder::getInstance($pid);$downloadSizeRecorder->maxSize = $size_limit;……//发起curl请求$response = curl_exec($ch);……//保存文件，返回md5$downloadSizeRecorder->saveMaxSizeData2File(); //保存$downloadFileMd5 = $downloadSizeRecorder->returnFileMd5();$downloadedfile_size = $downloadSizeRecorder->returnSize();$downloadSizeRecorder->deleteFile();

if($response === true){  $response = $downloadSizeRecorder->downloadData;}