无类型文件读写

无类型文件读写

unit Unit1;     interface     uses       Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,       Dialogs, StdCtrls;     type       TForm1 = class(TForm)         Memo1: TMemo;         Button1: TButton;         Button2: TButton;         Button3: TButton;         Button4: TButton;         Button5: TButton;         Button6: TButton;         Button7: TButton;         procedure Button1Click(Sender: TObject);         procedure Button2Click(Sender: TObject);         procedure Button3Click(Sender: TObject);         procedure Button4Click(Sender: TObject);         procedure Button5Click(Sender: TObject);         procedure Button6Click(Sender: TObject);         procedure Button7Click(Sender: TObject);       private         { Private declarations }       public         { Public declarations }       end;     var       Form1: TForm1;     implementation     {$R *.dfm}     const       FileName = 'c:\temp\binary.dat';     var       F: file;     //用无类型的方式写入一个字节     procedure TForm1.Button1Click(Sender: TObject);     var       b: Byte;     begin       AssignFile(F,FileName);       Rewrite(F,1); //第二个参数表示: 把 1 个字节当作一个写入单位       b := 65;       BlockWrite(F,b,1); //写入; 参数2是要写入的内容; 参数3表示写入 1 次.       CloseFile(F);     //落实 binary.dat 的大小: 1个字节; 内容: A (可用记事本打开)     end;     //用无类型的方式读出一个字节     procedure TForm1.Button2Click(Sender: TObject);     var       b: Byte;     begin       AssignFile(F,FileName);       Reset(F,1); //把 1 个字节当作一个读取单位       BlockRead(F,b,1); //读取一次; 放入 b       ShowMessage(Chr(b)); //A       CloseFile(F);     end;     //写入更多字节     procedure TForm1.Button3Click(Sender: TObject);     var       buffer: array[0..127] of Byte;       i: Integer; //储存多个字节, 需要用数组了     begin       for i := Low(buffer) to High(buffer) do         buffer[i] := i; //给数组赋值, 注意现在数组大小是 128       AssignFile(F,FileName);       Rewrite(F,32); //规定把 32 个字节当作一个读取单位, 注意这个数字和缓冲区大小必须是倍数关系       BlockWrite(F,buffer,4); //需要写入几次呢? 128/32=4       CloseFile(F);     //写成的文件肯定是128字节大小, 但用记事本可能看不了, 因为这个二进制不是文本     end;     //读出     procedure TForm1.Button4Click(Sender: TObject);     var       buffer: array[0..127] of Byte;       i: Integer;     begin       AssignFile(F,FileName);       Reset(F,4); //把 4 字节当作一个读取单位; 为了那个倍数关系, 这里一般是 1       BlockRead(F,buffer,32); //当然需要 32 次才能读完       CloseFile(F);       //怎么显示一下呢? 还是用 Memo 吧; 显示字符? 数字? 还是十六进制吧       Memo1.Clear;       for i := Low(buffer) to High(buffer) do       begin         Memo1.Lines.Add(IntToHex(buffer[i],1));       end;     (*显示结果: 0 1 2 3 ... 7D 7E 7F *)     end;     //读写 Char 与实际读写字节     procedure TForm1.Button5Click(Sender: TObject);     var       cArr1,cArr2: array[0..4] of Char;       i: Integer;       num: Integer; //记录实际读写的字节数     begin       for i := Low(cArr1) to High(cArr1) do         cArr1[i] := Chr(65+i); //填充 A B C D E       AssignFile(F,FileName);       Rewrite(F,1); //建立       BlockWrite(F,cArr1,Length(cArr1),num); //参数4: num 是实际写入的字节数       ShowMessage(IntToStr(num)); //5       Reset(F,1); //重新打开       BlockRead(F,cArr2,Length(cArr2),num); //参数5: num 是实际读出的字节数       ShowMessage(IntToStr(num)); //5       ShowMessage(cArr2); //ABCDE       CloseFile(F);     end;     //写入长字符串, 读出其十六进制码     procedure TForm1.Button6Click(Sender: TObject);     var       p: PChar;       b: Byte;     begin       p := '万一的 Delphi 博客';       AssignFile(F,FileName);     //关联文件名       Rewrite(F,1);               //创建并打开       BlockWrite(F,p,Length(p));  //写入       FileMode := fmOpenRead;     //这时可以设文件为只读       Reset(F,1);                 //为读取打开       Memo1.Clear;       while not Eof(F) do       begin         BlockRead(F,b,1);         Memo1.Text := Memo1.Text + IntToHex(b,2) + ' ';       end;       //显示结果: 70 F0 45 00 08 F7 12 00 A6 FB 43 00 A0 1A E5 00 FF C5       CloseFile(F);     end;     //复制个文件     procedure TForm1.Button7Click(Sender: TObject);     var       FromF,ToF: file;       NumRead,NumWritten: Integer;       Buffer: array[1..2048] of Byte;     begin       AssignFile(FromF, 'c:\temp\test1.dat'); //假定有这个文件       Reset(FromF, 1);       AssignFile(ToF, 'c:\temp\test2.dat');       Rewrite(ToF, 1);       repeat         BlockRead(FromF, Buffer, SizeOf(Buffer), NumRead);         BlockWrite(ToF, Buffer, NumRead, NumWritten);       until (NumRead = 0) or (NumWritten <> NumRead);       { NumRead=0 表示读完了; NumWritten <> NumRead 表示磁盘空间不够了 }       CloseFile(FromF);       CloseFile(ToF);     end;     end.