用wininet.pas中的函数如何实现FTP的断点续传。仅用API实现。(100分)

如题。

试试indy

我是讲用纯API。。

如果硬要用Indy，新具体谈谈断点续传的实现。谢谢。

unit Unit1;

interface

uses
{}filectrl,inifiles,{}Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ScktComp, ExtCtrls;

type
Tbuf_char=array[0..4095] of char;
Tbuf_byte=array[0..4095] of byte;

type
TForm1 = class(TForm)
ClientSocket1: TClientSocket;
Memo1: TMemo;
Panel1: TPanel;
Edit1: TEdit;
Button1: TButton;
Edit2: TEdit;
Button3: TButton;
Button4: TButton;
Label2: TLabel;
Label3: TLabel;
Label1: TLabel;
procedure ClientSocket1Read(Sender: TObject; Socket: TCustomWinSocket);
procedure Button1Click(Sender: TObject);
procedure ClientSocket1Connect(Sender: TObject;
Socket: TCustomWinSocket);
procedure Edit1Change(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure Edit2Change(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
filename1:string; //本地文件名
serfilename:string; //服务器端文件名
serhost1:string; //服务器地址
can_rec1:boolean; //是否可以接收
stop1:boolean; //是否停止

end;

var
Form1: TForm1;
pos1:longint; //上次下载到的位置


implementation


{$R *.dfm}

function app_path1:string;
begin
result:=extractfilepath(application.ExeName);
end;


//接收一行数据//socket,超时，结束符
function socket_rec_line1(socket1:TCustomWinSocket;timeout1:integer;crlf1:string=#13#10):string;
var
buf1:Tbuf_char;
r1:integer;
ts1:TStringStream; //保存所有的数据

FSocketStream: TWinSocketStream;

begin

ts1:=TStringStream.Create('');
FSocketStream:= TWinSocketStream.create(Socket1, timeout1);


//while true do//下面的一句更安全,不过对本程序好象没起作用
while (socket1.Connected=true) do
begin

//确定是否可以接收数据
//只能确定接收的超时，可见WaitForData的源码
if not FSocketStream.WaitForData(timeout1) then break; //continue;

//这一句是一定要有的，以免返回的数据不正确
zeromemory(@buf1,sizeof(buf1));
r1 := FsocketStream.Read(buf1, 1); //每次只读一个字符，以免读入了命令外的数据
//读不出数据时也要跳出，要不会死循环
if r1=0 then break; //test
//用FsocketStream.Read能设置超时
//r1:=socket1.ReceiveBuf(buf1,sizeof(buf1));
ts1.Write(buf1,r1);

//读到回车换行符了
if pos(crlf1,ts1.DataString)<>0 then
begin
break;
end;

end;

result:=ts1.DataString;

//没有读到回车换行符,就表示有超时错，这时返回空字符串
if pos(crlf1,result)=0 then
begin
result:='';
end;

ts1.Free;
FSocketStream.Free;

end;


function get_host1(in1:string):string;
begin
in1:=trim(in1);
if pos('http://',lowercase(in1))=1 then
begin
in1:=copy(in1,length('http://')+1,length(in1));
end;
if pos('/',in1)<>0 then
begin
in1:=copy(in1,0,pos('/',in1)-1);
end;
result:=in1;
end;

function get_file1(in1:string):string;
begin
in1:=trim(in1);
if pos('http://',lowercase(in1))=1 then
begin
in1:=copy(in1,length('http://')+1,length(in1));
end;
if pos('/',in1)<>0 then
begin
in1:=copy(in1,pos('/',in1)+1,length(in1));
end;
result:=in1;

end;

procedure TForm1.ClientSocket1Read(Sender: TObject;
Socket: TCustomWinSocket);
begin
memo1.Lines.Add(socket.ReceiveText);
end;

procedure TForm1.Button1Click(Sender: TObject);
var
url1:string;
buf1:Tbuf_byte;
rec1:longint;
f1:file;

cmd1:string; //这一行的内容
reclen1,real_reclen1:longint; //服务器返回的长度;实际已经收到的长度
value1:string; //标志们的值
total_len1:longint; //数据总长

begin
try

//self.filename1:='c:/temp1.dat';
assignfile(f1,self.filename1);
can_rec1:=false;
self.stop1:=false;

if FileExists(self.filename1)=true then
begin
reset(f1,1);
pos1:=filesize(f1);
end
else
begin
rewrite(f1,1);
pos1:=0;
end;

seek(f1,pos1);


ClientSocket1.Active:=false;
ClientSocket1.Host:=get_host1(edit1.Text);
ClientSocket1.Port:=80;


url1:='';

self.serfilename:=get_file1(edit1.Text);
self.serhost1:=get_host1(edit1.Text);

//取得文件长度以确定什么时候结束接收[通过"head"请求得到]

ClientSocket1.Active:=false;
ClientSocket1.Active:=true;
url1:='';

url1:=url1+'HEAD /'+self.serfilename+' HTTP/1.1'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
url1:=url1+'Pragma: no-cache'+#13#10;
//新的
url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//下面这句必须要有
//url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Host: '+self.serhost1+#13#10;
url1:=url1+#13#10;

ClientSocket1.Socket.SendText(url1);

while ClientSocket1.Active=true do
begin

if self.stop1=true then break;

cmd1:=socket_rec_line1(ClientSocket1.Socket,60*1000);

//计算文件的长度

if pos(lowercase('Content-Length: '),lowercase(cmd1))=1 then
begin
value1:=copy(cmd1,length('Content-Length: ')+1,length(cmd1));
total_len1:=strtoint(trim(value1));
end;

//计算文件的长度_end;

if cmd1=#13#10 then break;
end;

//取得文件长度以确定什么时候结束接收_end;

//发送get请求，以得到实际的文件数据

clientsocket1.Active:=false;
clientsocket1.Active:=true;

url1:='';

//url1:=url1+'GET http://clq.51.net/textfile.zip HTTP/1.1'+#13#10;
//url1:=url1+'GET /textfile.zip HTTP/1.1'+#13#10;
url1:=url1+'GET /'+self.serfilename+' HTTP/1.1'+#13#10;
url1:=url1+'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*'+#13#10;
//应该可以不要url1:=url1+'Accept-Language: zh-cn'+#13#10;
//应该可以不要url1:=url1+'Accept-Encoding: gzip, deflate'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
//url1:=url1+'Pragma: no-cache'+#13#10;
//新的
//url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//接受数据的范围,可选
//url1:=url1+'RANGE: bytes=533200-'+#13#10;
url1:=url1+'RANGE: bytes='+inttostr(pos1)+'-'+#13#10;
//下面这句必须要有
//url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Host: '+self.serhost1+#13#10;
//应该可以不要
//url1:=url1+'Connection: Keep-Alive'+#13#10;
url1:=url1+#13#10;
ClientSocket1.Socket.SendText(url1);

while ClientSocket1.Active=true do
begin

if self.stop1=true then break;

cmd1:=socket_rec_line1(ClientSocket1.Socket,60*1000);

//是否可接收
if pos(lowercase('Content-Range:'),lowercase(cmd1))=1 then
begin
can_rec1:=true;
end;

//是否可接收_end;

//计算要接收的长度

if pos(lowercase('Content-Length: '),lowercase(cmd1))=1 then
begin
value1:=copy(cmd1,length('Content-Length: ')+1,length(cmd1));
reclen1:=strtoint(trim(value1));
end;

//计算要接收的长度_end;

//头信息收完了
if cmd1=#13#10 then break;
end;

real_reclen1:=0;
while ClientSocket1.Active=true do
begin


if self.stop1=true then break;

//不能接收则退出
if can_rec1=false then break;

//如果文件当前的长度大于服务器标识的长度,则是出错了，不要写入文件中
if filesize(f1)>=total_len1 then
begin
showmessage('文件已经下载完毕了！');
break;
end;

zeromemory(@buf1,sizeof(buf1));
rec1:=ClientSocket1.Socket.ReceiveBuf(buf1,sizeof(buf1));

//如果实际收到的长度大于服务器标识的长度,则是出错了，不要写入文件中
if real_reclen1>=reclen1 then
begin
showmessage('文件已经下载完毕了！');
break;

end;
//如果当前的长度大于服务器标识的长度,则是出错了，不要写入文件中
if pos1=reclen1 then
begin
showmessage('文件已经下载完毕了！');
break;

end;

blockwrite(f1,buf1,rec1);

real_reclen1:=real_reclen1+rec1;

Label1.Caption:=FormatFloat('#,##',real_reclen1)+'/'+FormatFloat('#,##',reclen1);
Label1.Caption:=Label1.Caption+'->'+inttostr(trunc((real_reclen1/reclen1)*100))+'%';
application.ProcessMessages;



end;

closefile(f1);
showmessage('ok');

//发送get请求，以得到实际的文件数据_end;

ClientSocket1.Active:=false;

except
closefile(f1);
showmessage('discon...');
end;


end;

procedure TForm1.ClientSocket1Connect(Sender: TObject;
Socket: TCustomWinSocket);
var
url1:string;
begin
{ url1:='';

url1:=url1+'GET http://clq.51.net/textfile.zip HTTP/1.1'+#13#10;
url1:=url1+'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*'+#13#10;
//应该可以不要url1:=url1+'Accept-Language: zh-cn'+#13#10;
//应该可以不要url1:=url1+'Accept-Encoding: gzip, deflate'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
url1:=url1+'Pragma: no-cache'+#13#10;
//新的
url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//接受数据的范围,可选
url1:=url1+'RANGE: bytes=533200-'+#13#10;
//下面这句必须要有
url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Connection: Keep-Alive'+#13#10;
url1:=url1+#13#10;
ClientSocket1.Socket.SendText(url1);

}
end;

procedure TForm1.Edit1Change(Sender: TObject);
var
ini1:tinifile;
begin
ini1:=tinifile.Create(app_path1+'sys1.ini');
ini1.WriteString('file1','host1',edit1.Text);

ini1.Free;

end;

procedure TForm1.FormCreate(Sender: TObject);
var
ini1:tinifile;
begin
ini1:=tinifile.Create(app_path1+'sys1.ini');
edit1.Text:=ini1.ReadString('file1','host1',edit1.Text);
self.filename1:=ini1.ReadString('file1','filename1','c:/temp1.dat');
edit2.Text:=self.filename1;
//pos1:=filesize(
ini1.Free;


end;

procedure TForm1.Edit2Change(Sender: TObject);
var
ini1:tinifile;
begin
ini1:=tinifile.Create(app_path1+'sys1.ini');
ini1.WriteString('file1','filename1',edit2.Text);

self.filename1:=edit2.Text;
ini1.Free;

end;

procedure TForm1.Button3Click(Sender: TObject);
var
url1:string;
buf1:Tbuf_byte;
rec1:longint;
f1:file;

cmd1:string; //这一行的内容
reclen1,real_reclen1:longint; //服务器返回的长度;实际已经收到的长度
value1:string; //标志们的值

begin
self.stop1:=false;

ClientSocket1.Active:=false;
ClientSocket1.Host:=get_host1(edit1.Text);
ClientSocket1.Port:=80;
ClientSocket1.Active:=true;

url1:='';

self.serfilename:=get_file1(edit1.Text);
self.serhost1:=get_host1(edit1.Text);
//url1:=url1+'GET http://clq.51.net/textfile.zip HTTP/1.1'+#13#10;
//url1:=url1+'GET /textfile.zip HTTP/1.1'+#13#10;
url1:=url1+'GET /'+self.serfilename+' HTTP/1.1'+#13#10;
//url1:=url1+'HEAD /'+self.serfilename+' HTTP/1.1'+#13#10;
url1:=url1+'Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, */*'+#13#10;
//应该可以不要
//url1:=url1+'Accept-Language: zh-cn'+#13#10;
//应该可以不要
//url1:=url1+'Accept-Encoding: gzip, deflate'+#13#10;

//不使用缓存,我附加的
//与以前的服务器兼容
//url1:=url1+'Pragma: no-cache'+#13#10;
//新的
//url1:=url1+'Cache-Control: no-cache'+#13#10;

//不使用缓存,我附加的_end;

url1:=url1+'User-Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; .NET CLR 1.0.3705)'+#13#10;
//接受数据的范围,可选
//url1:=url1+'RANGE: bytes=533200-'+#13#10;
url1:=url1+'RANGE: bytes='+inttostr(533263)+'-533263'+#13#10;
//下面这句必须要有
//url1:=url1+'Host: clq.51.net'+#13#10;
url1:=url1+'Host: '+self.serhost1+#13#10;
//应该可以不要
//url1:=url1+'Connection: Keep-Alive'+#13#10;
url1:=url1+#13#10;
ClientSocket1.Socket.SendText(url1);


//while ClientSocket1.Active=true do
begin
zeromemory(@buf1,sizeof(buf1));
rec1:=ClientSocket1.Socket.ReceiveBuf(buf1,sizeof(buf1));

real_reclen1:=real_reclen1+rec1;

memo1.Lines.Add(strpas(@buf1));

application.ProcessMessages;
//if self.stop1=true then break;
end;

ClientSocket1.Active:=false;

showmessage('ok');


end;

procedure TForm1.Button4Click(Sender: TObject);
begin
self.stop1:=true;
end;

end.

wininet里的不叫API吧？

用InternetReadFileEx，只要设置INTERNET_BUFFERS结构中的dwOffsetLow和dwOffsetHigh就可以设置下载起始点

1.FtpOpenFile+InternetReadFileEx+InternetCloseHandle
2.FtpOpenFile+InternetSetFilePointer+InternetReadFile+InternetCloseHandle
具体的函数参考看看Win32SDK的帮助文档吧。

InternetReadFileEx
Reads data from a handle opened by the InternetOpenUrl or HttpOpenRequest function.

BOOL InternetReadFileEx(
HINTERNET hFile,
LPINTERNET_BUFFERS lpBuffersOut,
DWORD dwFlags,
DWORD dwContext
);

Parameters
hFile
[in] Handle returned by the InternetOpenUrl or HttpOpenRequest function.
lpBuffersOut
[out] Pointer to an INTERNET_BUFFERS structure that receives the data downloaded.
dwFlags
[in] This parameter can be the following value.Value Meaning
IRF_NO_WAIT Do not wait for data. If there is data available, the function returns either the amount of data requested or the amount of data available (whichever is smaller).

dwContext
[in] Context value used for asynchronous operations.
Return Values
Returns TRUE if successful, or FALSE otherwise. To get extended error information, call GetLastError. An application can also use InternetGetLastResponseInfo when necessary.
Requirements
Client: Requires Windows XP, Windows 2000 Professional, Windows NT Workstation 4.0, Windows Me, Windows 98, or Windows 95.
Server: Requires Windows Server 2003, Windows 2000 Server, or Windows NT Server 4.0.
Version: Requires Internet Explorer 4.0 or later.
Header: Declared in Wininet.h.
Library: Use Wininet.lib.


See Also
Common Functions, WinINet Functions

多人接受答案了。

InternetSetFilePointer对FTP不起作用。
不过InternetReadFileEx我却没有试过。
等一下试试。

不论怎样，多谢大家的帮忙。分数已分。