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;