我从第三方网站得到了源代码,解释了如何使用WinInet从互联网下载文件.我不太熟悉API,我看了看WinInet单元,但没有看到任何API调用,就像我需要的.
我正在做的是增加报告下载文件进度的能力.这个程序我已经包含在一个TThread里面,一切都很好.然而,只有一个缺失的部分：在下载之前查找源文件的总大小.
看下面我有一个评论//如何获得总大小？在我开始下载文件之前,我需要知道什么是文件的总大小.我该怎么做呢？因为这个代码似乎不知道文件的大小,直到它被完成下载 – 这使得这个添加无关紧要.
procedure TInetThread.Execute;
const
BufferSize = 1024;
var
hSession,hURL: HInternet;
Buffer: array[1..BufferSize] of Byte;
BufferLen: DWORD;
f: File;
S: Bool;
D: Integer;
T: Integer;
procedure DoWork(const Amt: Integer);
begin
if assigned(FOnWork) then
FOnWork(Self,FSource,FDest,Amt,T);
end;
begin
S:= False;
try
try
if not DirectoryExists(ExtractFilePath(FDest)) then begin
ForceDirectories(ExtractFilePath(FDest));
end;
hSession:= InternetOpen(PChar(FAppName),INTERNET_OPEN_TYPE_PRECONFIG,nil,0);
try
hURL:= InternetOpenURL(hSession,PChar(FSource),0);
try
AssignFile(f,FDest);
Rewrite(f,1);
T:= 0; //HOW TO GET TOTAL SIZE?
D:= 0;
DoWork(D);
repeat
InternetReadFile(hURL,@Buffer,SizeOf(Buffer),BufferLen);
BlockWrite(f,Buffer,BufferLen);
D:= D + BufferLen;
DoWork(D);
until BufferLen = 0;
CloseFile(f);
S:= True;
finally
InternetCloseHandle(hURL);
end
finally
InternetCloseHandle(hSession);
end;
except
on e: exception do begin
S:= False;
end;
end;
finally
if assigned(FOnComplete) then
FOnComplete(Self,S);
end;
end;
解决方法
您可以使用HEAD方法,并检查Content-Length以检索远程文件的文件大小
检查这两个方法
WinInet的
如果要执行HEAD方法,则必须使用HttpOpenRequest,HttpSendRequest和HttpQueryInfo WinInet函数.
uses
SysUtils,Windows,WinInet;
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,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,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;
const
sUserAgent = 'Mozilla/5.001 (windows; U; NT4.0; en-US; rv:1.0) Gecko/25250101';
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),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,INTERNET_SERVICE_HTTP,0);
if hConnect=nil then
begin
ErrorCode:=GetLastError;
raise Exception.Create(Format('InternetConnect Error %d Description %s',GetWinInetError(ErrorCode)]));
end;
try
hRequest := HttpOpenRequest(hConnect,PChar('HEAD'),PChar(Resource),0);
if hRequest<>nil then
begin
try
lpdwBufferLength:=SizeOf(Result);
lpdwReserved :=0;
if not HttpSendRequest(hRequest,0) then
begin
ErrorCode:=GetLastError;
raise Exception.Create(Format('HttpOpenRequest Error %d Description %s',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',GetWinInetError(ErrorCode)]));
end;
finally
InternetCloseHandle(hRequest);
end;
end
else
begin
ErrorCode:=GetLastError;
raise Exception.Create(Format('HttpOpenRequest Error %d Description %s',GetWinInetError(ErrorCode)]));
end;
finally
InternetCloseHandle(hConnect);
end;
finally
InternetCloseHandle(hInet);
end;
end;
印
还要检查这个代码使用indy.
function GetRemoteFilesize(const Url :string) : Integer;
var
Http: TIdHTTP;
begin
Http := TIdHTTP.Create(nil);
try
Http.Head(Url);
result:= Http.Response.ContentLength;
finally
Http.Free;
end;
end;