Delphi - URL 的文件大小 - 错误 12150

Posted 2023-02-16

【中文标题】Delphi - URL 的文件大小 - 错误 12150

【英文标题】：Delphi - File size by URL - error 12150

【发布时间】：2013-01-30 12:25:13

【问题描述】：

Delphi 6 教授，Win7 操作系统。

我有这段代码可以通过 URL 获取文件大小：

function TDDWIToolObject.GetFileSize(out Size: Int64): boolean;
var
    hInet: HINTERNET;
    hRequest : HINTERNET;
    lpdwBufferLength: DWORD;
    lpdwReserved    : DWORD;
    ServerName: string;
    Resource: string;
    FileSizeBuffer : array[0..32] of char;
    //SizeCard : Cardinal;
begin
    ParseURL(Url, ServerName, Resource);
    Result := False;
    Size := 0;

    hInet := InternetOpen(PChar(_UserAgent), INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
    if hInet=nil then begin
        FErrorCode := GetLastError;
        Exit;
    end;

    try


        hRequest := InternetOpenUrl(hInet, PChar(URL), PCHar(Headers), Length(HEaders), 0, 0);

        try

            FillChar(FileSizeBuffer, SizeOf(FileSizeBuffer), #0);
            lpdwBufferLength := SizeOf(FileSizeBuffer);
            lpdwReserved :=0;

            if not HttpQueryInfo(
                hRequest,
                HTTP_QUERY_CONTENT_LENGTH,
                @FileSizeBuffer, lpdwBufferLength, lpdwReserved) then begin

                FErrorCode:=GetLastError;
                Exit;
            end;

            Size := StrToInt64(StrPas(FileSizeBuffer));
            Result := True;

        finally
            InternetCloseHandle(hRequest);
        end;

    finally
        InternetCloseHandle(hInet);
    end;

end;

在我的机器 + DSL 连接上运行良好。

但是当我在其他完全受保护的地方（代理+许多策略）检查此代码时，我得到错误代码 12150... :-(

有趣的是，当我使用这段代码时，我可以下载这个文件：

function TDDWIToolObject.DownloadFile;
var
    hInet: HINTERNET;
    hFile: HINTERNET;
    pbuffer: Pointer;
    bytesRead: DWORD;
    Stm : TFileStream;
    TotalBytes : Int64;
    AbortIt : boolean;
begin
    Result := False;
    FErrorCode := -1;
    FAborted := False;
    hInet := InternetOpen(PChar(_UserAgent), INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
    if hInet = nil
        then begin
            FErrorCode := GetLastError;
            Exit;
        end;
    try
        hFile := InternetOpenURL(hInet, PChar(URL), PChar(FHeaders), Length(FHeaders), 0, 0);
        if hFile = nil
            then begin
                FErrorCode := GetLastError;
                Exit;
            end;
        try
            Stm := TFileStream.Create(FN, fmCreate);
            try
                GetMem(pbuffer, FBufferSize);
                try
                    TotalBytes := 0; AbortIt := False;
                    while (not FAborted) do begin
                        if not InternetReadFile(hFile, pbuffer, FBufferSize, bytesRead) then begin
                            FErrorCode := GetLastError;
                            Exit;
                        end;
                        if bytesRead > 0 then begin
                            Stm.WriteBuffer(pbuffer^, bytesRead);
                            if Assigned(FOnBytesArrived)
                                then begin
                                    inc(TotalBytes, bytesRead);
                                    FOnBytesArrived(Self, TotalBytes, AbortIt);
                                    if AbortIt
                                        then Abort;
                                end;
                        end else begin
                            break;
                        end;
                    end;
                finally
                    FreeMem(pbuffer);
                end;
                if not FAborted
                    then Result := True;
            finally
                Stm.Free;
            end;
        finally
            InternetCloseHandle(hFile);
        end;
    finally
        InternetCloseHandle(hInet);
    end;
end;

这很有趣，因为系统管理员允许在代理中对这个 URL 的请求，并且下载对我有用 - 只有内容长度请求失败。

我想问一个问题，但很难做到，因为其中很多都在我的脑海中...... 您知道我们可以做些什么来允许这些请求吗？ 也许 HttpRequest 使用另一个端口，或者一些“非法”的不可代理？ 或者我的代码似乎是错误的？为什么它在非保护区工作？下载和获取内容长度请求有什么区别？

所以问题是总结格式：你知道我可以做些什么来在下载之前获取文件大小吗？

谢谢。

【问题讨论】：

不，如果我添加 flag_number，我得到的结果是数字（我知道红衣主教）。我更喜欢符合 Int64 的字符串。

【参考方案1】：

这个错误可能是由很多因素引起的（ERROR_HTTP_HEADER_NOT_FOUND），在你的代码中你没有在调用HttpQueryInfo方法之前检查InternetOpenUrl函数的结果，我没有看到的内容_UserAgent 和 Headers 变量给你一个更准确的答案。无论如何尝试使用HttpOpenRequest 和HttpSendRequest 函数而不是InternetOpenURL。

试试这个示例

uses
  Windows,
  SysUtils,
  WinInet;


const
  sUserAgent = 'Mozilla/5.001 (windows; U; NT4.0; en-US; rv:1.0) Gecko/25250101';

function GetWinInetError(ErrorCode:Cardinal): string;
const
   winetdll = 'wininet.dll';
var
  Len: Integer;
  Buffer: PChar;
begin
  Len := FormatMessage(
  FORMAT_MESSAGE_FROM_HMODULE or FORMAT_MESSAGE_FROM_SYSTEM or
  FORMAT_MESSAGE_ALLOCATE_BUFFER or FORMAT_MESSAGE_IGNORE_INSERTS or  FORMAT_MESSAGE_ARGUMENT_ARRAY,
  Pointer(GetModuleHandle(winetdll)), ErrorCode, 0, @Buffer, SizeOf(Buffer), nil);
  try
    while (Len > 0) and $IFDEF UNICODE(CharInSet(Buffer[Len - 1], [#0..#32, '.'])) $ELSE(Buffer[Len - 1] in [#0..#32, '.']) $ENDIF do Dec(Len);
    SetString(Result, Buffer, Len);
  finally
    LocalFree(HLOCAL(Buffer));
  end;
end;


procedure ParseURL(const lpszUrl: string; var Host, Resource: string);
var
  lpszScheme      : array[0..INTERNET_MAX_SCHEME_LENGTH - 1] of Char;
  lpszHostName    : array[0..INTERNET_MAX_HOST_NAME_LENGTH - 1] of Char;
  lpszUserName    : array[0..INTERNET_MAX_USER_NAME_LENGTH - 1] of Char;
  lpszPassword    : array[0..INTERNET_MAX_PASSWORD_LENGTH - 1] of Char;
  lpszUrlPath     : array[0..INTERNET_MAX_PATH_LENGTH - 1] of Char;
  lpszExtraInfo   : array[0..1024 - 1] of Char;
  lpUrlComponents : TURLComponents;
begin
  ZeroMemory(@lpszScheme, SizeOf(lpszScheme));
  ZeroMemory(@lpszHostName, SizeOf(lpszHostName));
  ZeroMemory(@lpszUserName, SizeOf(lpszUserName));
  ZeroMemory(@lpszPassword, SizeOf(lpszPassword));
  ZeroMemory(@lpszUrlPath, SizeOf(lpszUrlPath));
  ZeroMemory(@lpszExtraInfo, SizeOf(lpszExtraInfo));
  ZeroMemory(@lpUrlComponents, SizeOf(TURLComponents));

  lpUrlComponents.dwStructSize      := SizeOf(TURLComponents);
  lpUrlComponents.lpszScheme        := lpszScheme;
  lpUrlComponents.dwSchemeLength    := SizeOf(lpszScheme);
  lpUrlComponents.lpszHostName      := lpszHostName;
  lpUrlComponents.dwHostNameLength  := SizeOf(lpszHostName);
  lpUrlComponents.lpszUserName      := lpszUserName;
  lpUrlComponents.dwUserNameLength  := SizeOf(lpszUserName);
  lpUrlComponents.lpszPassword      := lpszPassword;
  lpUrlComponents.dwPasswordLength  := SizeOf(lpszPassword);
  lpUrlComponents.lpszUrlPath       := lpszUrlPath;
  lpUrlComponents.dwUrlPathLength   := SizeOf(lpszUrlPath);
  lpUrlComponents.lpszExtraInfo     := lpszExtraInfo;
  lpUrlComponents.dwExtraInfoLength := SizeOf(lpszExtraInfo);

  InternetCrackUrl(PChar(lpszUrl), Length(lpszUrl), ICU_DECODE or ICU_ESCAPE, lpUrlComponents);

  Host := lpszHostName;
  Resource := lpszUrlPath;
end;

function GetRemoteFileSize(const Url : string): Integer;
var
  hInet    : HINTERNET;
  hConnect : HINTERNET;
  hRequest : HINTERNET;
  lpdwBufferLength: DWORD;
  lpdwReserved    : DWORD;
  ServerName: string;
  Resource: string;
  ErrorCode : Cardinal;
begin
  ParseURL(Url,ServerName,Resource);
  Result:=0;

  hInet := InternetOpen(PChar(sUserAgent), INTERNET_OPEN_TYPE_PRECONFIG, nil, nil, 0);
  if hInet=nil then
  begin
    ErrorCode:=GetLastError;
    raise Exception.Create(Format('InternetOpen Error %d Description %s',[ErrorCode,GetWinInetError(ErrorCode)]));
  end;

  try
    hConnect := InternetConnect(hInet, PChar(ServerName), INTERNET_DEFAULT_HTTP_PORT, nil, nil, INTERNET_SERVICE_HTTP, 0, 0);
    if hConnect=nil then
    begin
      ErrorCode:=GetLastError;
      raise Exception.Create(Format('InternetConnect Error %d Description %s',[ErrorCode,GetWinInetError(ErrorCode)]));
    end;

    try
      hRequest := HttpOpenRequest(hConnect, PChar('HEAD'), PChar(Resource), nil, nil, nil, 0, 0);
        if hRequest<>nil then
        begin
          try
            lpdwBufferLength:=SizeOf(Result);
            lpdwReserved    :=0;
            if not HttpSendRequest(hRequest, nil, 0, nil, 0) then
            begin
              ErrorCode:=GetLastError;
              raise Exception.Create(Format('HttpOpenRequest Error %d Description %s',[ErrorCode,GetWinInetError(ErrorCode)]));
            end;

             if not HttpQueryInfo(hRequest, HTTP_QUERY_CONTENT_LENGTH or HTTP_QUERY_FLAG_NUMBER, @Result, lpdwBufferLength, lpdwReserved) then
             begin
              Result:=0;
              ErrorCode:=GetLastError;
              raise Exception.Create(Format('HttpQueryInfo Error %d Description %s',[ErrorCode,GetWinInetError(ErrorCode)]));
             end;
          finally
            InternetCloseHandle(hRequest);
          end;
        end
        else
        begin
          ErrorCode:=GetLastError;
          raise Exception.Create(Format('HttpOpenRequest Error %d Description %s',[ErrorCode,GetWinInetError(ErrorCode)]));
        end;
    finally
      InternetCloseHandle(hConnect);
    end;
  finally
    InternetCloseHandle(hInet);
  end;

end;

【讨论】：

另外，请记住，并非所有 HTTP 响应，尤其是 HTTP 1.1 响应，都有 Content-Length 标头，但仍然可以传输数据。这是通过通过Transfer-Encoding: chunked 标头对响应进行分块来实现的，在这种情况下，计算文件大小的唯一方法是实际完整下载它。