I got the source below from a third-party site explaining how to download a file from the internet using WinInet. I'm not too familiar with API, and I took at look at the WinInet unit but did not see any API calls like what I need.
What I'm doing is adding the ability to report back progress of downloading a file. This procedure I've already wrapped inside of a TThread and everything works fine. However, just one missing piece: Finding the total size of the source file before downloading.
See below where I have a comment //HOW TO GET TOTAL SIZE? This is where I need to find out what is the total size of the file BEFORE I begin downloading it. How do I go about doing this? Because this code seems to not know the size of the file until it's done being downloaded - and that makes this addition irrelevant.
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, nil, 0);
try
hURL:= InternetOpenURL(hSession, PChar(FSource), nil, 0, 0, 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, FSource, FDest, S);
end;
end;
You can use the HEAD method and check the Content-Length to retrieve the file size of a remote file
Check these two Methods
WinInet
If you want execute a HEAD method you must use the HttpOpenRequest, HttpSendRequest and HttpQueryInfo WinInet functions .
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, 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;
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), 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;
Indy
Also check this code using 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;