Question

在DELPHI中如何用文件流读写几百M大的文件呢？

在DELPHI中如何用文件流读写几百M大的文件呢？

Answer 1

unit U_Client;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, IdBaseComponent, IdComponent, IdTCPConnection, IdTCPClient, Math,
StdCtrls, ComCtrls;

type
Tfrm_Client = class(TForm)
SaveDialog1: TSaveDialog;
IdTCPClient1: TIdTCPClient;
Button1: TButton;
StatusBar1: TStatusBar;
Edit1: TEdit;
Label1: TLabel;
Edit2: TEdit;
Label2: TLabel;
procedure Button1Click(Sender: TObject);
private
{ Private declarations }
public
{ Public declarations }
end;

var
frm_Client: Tfrm_Client;

implementation

{$R *.dfm}

procedure Tfrm_Client.Button1Click(Sender: TObject);
var
cmd: string;
ASize, TotalSize: Int64;
AFileStream: TFileStream;
begin
IdTCPClient1.Host := Edit1.Text; //连接主机
IdTCPClient1.Port := StrToIntDef(Edit2.Text, 9925); //端口
IdTCPClient1.Connect; //连接
try
IdTCPClient1.WriteLn('BEGIN'); //提示服务器开始接收
cmd := IdTCPClient1.ReadLn;
//以“|”符号分离文件名
SaveDialog1.FileName := Copy(cmd, Pos('|', cmd) + 1, Length(cmd));
if not SaveDialog1.Execute then
begin
IdTCPClient1.WriteLn('CANCEL'); //告诉服务器取消
IdTCPClient1.Disconnect; //断开连接
exit;
end;
TotalSize := StrToInt(Copy(cmd, 0, Pos('|', cmd) - 1)); //分离文件大小
//建立文件流准备接收
AFileStream := TFileStream.Create(SaveDialog1.FileName, fmCreate);
try //循环开始接受
repeat
IdTCPClient1.WriteLn(IntToStr(AFileStream.Size));//发送当前传输的位置
ASize := Min(TotalSize - AFileStream.Size, IdTCPClient1.RecvBufferSize);
//选择剩余大小和缓冲区大小小的一个作为传输的大小
IdTCPClient1.ReadStream(AFileStream, ASize); //接收流
StatusBar1.SimpleText := Format('当前传输位置%d/大小%d', [AFileStream.Size, TotalSize]);
Application.ProcessMessages;
until AFileStream.Size = TotalSize; //大小一致了表示结束
finally
AFileStream.Free; //释放文件流
end;
IdTCPClient1.WriteLn('END'); //提示服务器传输完成
StatusBar1.SimpleText := '传输完成...';
except
StatusBar1.SimpleText := '连接服务器失败或者对方已经中断传输！';
end;
IdTCPClient1.Disconnect;
end;

end.

unit U_Server;

interface

uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, ComCtrls, IdBaseComponent, IdComponent, IdTCPServer, Math;

type
Tfrm_Server = class(TForm)
IdTCPServer1: TIdTCPServer;
Button1: TButton;
Button2: TButton;
Button3: TButton;
ProgressBar1: TProgressBar;
StatusBar1: TStatusBar;
Edit1: TEdit;
Button4: TButton;
OpenDialog1: TOpenDialog;
Edit2: TEdit;
Label1: TLabel;
Label2: TLabel;
procedure Button1Click(Sender: TObject);
procedure Button4Click(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
procedure IdTCPServer1Execute(AThread: TIdPeerThread);
procedure FormClose(Sender: TObject; var Action: TCloseAction);
private
AFileStream: TFileStream; //传输的文件流
procedure ButtonBegin;
procedure ButtonEnd;
{ Private declarations }
public
{ Public declarations }
end;

var
frm_Server: Tfrm_Server;

implementation

{$R *.dfm}

procedure Tfrm_Server.Button1Click(Sender: TObject);
begin
if OpenDialog1.Execute then
Edit1.Text := OpenDialog1.FileName;
end;

procedure Tfrm_Server.Button4Click(Sender: TObject);
begin
Close;
end;

procedure Tfrm_Server.Button2Click(Sender: TObject);
begin
if not FileExists(Edit1.Text) then //检测文件是否存在
begin
Showmessage('文件不存在，请选择文件！');
exit;
end;
//建立文件流
AFileStream := TFileStream.Create(Edit1.Text, fmOpenRead);
ProgressBar1.Max := AFileStream.Size;
ProgressBar1.Position := 0;
ButtonBegin; //VCL开始状态设置
//服务器准备好连接
IdTCPServer1.DefaultPort := StrToIntDef(Edit2.Text, 9925);
if not IdTCPServer1.Active then IdTCPServer1.Active := True;
end;

procedure Tfrm_Server.ButtonBegin;
begin //VCL开始状态设置
Button1.Enabled := False;
Button2.Enabled := False;
Button3.Enabled := True;
Button4.Enabled := False;
end;

procedure Tfrm_Server.ButtonEnd;
begin //VCL结束状态设置
Button1.Enabled := True;
Button2.Enabled := True;
Button3.Enabled := False;
Button4.Enabled := True;
end;

procedure Tfrm_Server.Button3Click(Sender: TObject);
begin
StatusBar1.SimpleText := '传输取消...';
AFileStream.Free; //释放文件流
ButtonEnd; //VCL结束状态设置
end;

procedure Tfrm_Server.IdTCPServer1Execute(AThread: TIdPeerThread);
var
cmd: string; //接收到客户端的字符串信息
ASize: Integer; //需要传输的流大小
begin
with AThread.Connection do //已经连街上的一个进程
begin
cmd := UpperCase(ReadLn); //客户端发送的命令字符串
if cmd = 'BEGIN' then //开始传输
begin
//告诉远程传输文件的大小和文件名
WriteLn(Format('%d|%s', [AFileStream.Size, ExtractFileName(Edit1.Text)]));
StatusBar1.SimpleText := '准备传输...';
Exit;
end;
if cmd = 'END' then
begin //传输完成
Button3.Click;
StatusBar1.SimpleText := '传输完成...';
Exit;
end;
if cmd = 'CANCEL' then
begin //传输取消
StatusBar1.SimpleText := '传输取消...';
//保持传输状态
Exit;
end;
//按照指定位置传输文件
AFileStream.Seek(StrToInT(cmd), soFromBeginning); //转到文件流传输的位置
ASize := Min(AFileStream.Size - AFileStream.Position, RecvBufferSize);
//计算需要发送的大小，Min()函数在Math单元
OpenWriteBuffer; //准备发送缓冲
WriteStream(AFileStream, false, false, ASize);
//注意这个函数的参数。
CloseWriteBuffer; //结束发送缓冲
StatusBar1.SimpleText := Format('当前传输位置%s/大小%d', [cmd, AFileStream.Size]);
ProgressBar1.Position := ProgressBar1.Position + ASize;
end;
end;

procedure Tfrm_Server.FormClose(Sender: TObject; var Action: TCloseAction);
begin
IdTCPServer1.Active := False;
end;

end.

希望能帮到你！