I had the same problem and found a solution by extending the code above. The file length was available as suggested above by using the Header information.
Here is my code:
unit uhttpdownloader;
{$mode Delphi}{$H+}
interface
uses
Classes, SysUtils, httpsend, blcksock, typinfo;
//Interface for notifications about the progress
type
IProgress = interface
procedure ProgressNotification(Text: String; CurrentProgress : integer; MaxProgress : integer);
end;
type
{ THttpDownloader }
THttpDownloader = class
public
function DownloadHTTP(URL, TargetFile: string; ProgressMonitor : IProgress): Boolean;
private
Bytes : Integer;
MaxBytes : Integer;
HTTPSender: THTTPSend;
ProgressMonitor : IProgress;
procedure Status(Sender: TObject; Reason: THookSocketReason; const Value: String);
function GetSizeFromHeader(Header: String):integer;
end;
implementation
function THttpDownloader.DownloadHTTP(URL, TargetFile: string; ProgressMonitor : IProgress): Boolean;
var
HTTPGetResult: Boolean;
begin
Result := False;
Bytes:= 0;
MaxBytes:= -1;
Self.ProgressMonitor:= ProgressMonitor;
HTTPSender := THTTPSend.Create;
try
//add callback function for status updates
HTTPSender.Sock.OnStatus:= Status;
HTTPGetResult := HTTPSender.HTTPMethod('GET', URL);
if (HTTPSender.ResultCode >= 100) and (HTTPSender.ResultCode<=299) then begin
HTTPSender.Document.SaveToFile(TargetFile);
Result := True;
end;
finally
HTTPSender.Free;
end;
end;
//Callback function for status events
procedure THttpDownloader.Status(Sender: TObject; Reason: THookSocketReason; const Value: String);
var
V, currentHeader: String;
i: integer;
begin
//try to get filesize from headers
if (MaxBytes = -1) then
begin
for i:= 0 to HTTPSender.Headers.Count - 1 do
begin
currentHeader:= HTTPSender.Headers[i];
MaxBytes:= GetSizeFromHeader(currentHeader);
if MaxBytes <> -1 then break;
end;
end;
V := GetEnumName(TypeInfo(THookSocketReason), Integer(Reason)) + ' ' + Value;
//HR_ReadCount contains the number of bytes since the last event
if Reason = THookSocketReason.HR_ReadCount then
begin
Bytes:= Bytes + StrToInt(Value);
ProgressMonitor.ProgressNotification(V, Bytes, MaxBytes);
end;
end;
function THttpDownloader.GetSizeFromHeader(Header: String): integer;
var
item : TStringList;
begin
//the download size is contained in the header (e.g.: Content-Length: 3737722)
Result:= -1;
if Pos('Content-Length:', Header) <> 0 then
begin
item:= TStringList.Create();
item.Delimiter:= ':';
item.StrictDelimiter:=true;
item.DelimitedText:=Header;
if item.Count = 2 then
begin
Result:= StrToInt(Trim(item[1]));
end;
end;
end;
end.
The complete source code and example can be downloaded here as well: http://andydunkel.net/lazarus/delphi/2015/09/09/lazarus_synapse_progress.html
Andy