在上面两个中我们都是把一个文件做为整体进行复制

这一节我们要把文件分成块来一块块复制

procedure TForm1.Button1Click(Sender: TObject);
const
buffsize=4096;
var
instrm,outstrm:tfilestream;
i,biaoji:integer;
p:array [1..buffsize] of char;
begin
instrm:=tfilestream.Create('c:\my.exe',fmOpenRead);//流打开文件
outstrm:=tfilestream.Create('c:\ok.exe',fmCreate);//流保存的文件
i:=instrm.Size;
instrm.Position:=0;//把流指针放在开始位置,用时要从头读取
while instrm.Position <=i do
begin
  if  (i-instrm.Position)> buffsize then
  begin
     instrm.ReadBuffer(p,buffsize);
     outstrm.WriteBuffer(p,buffsize);
  end
  else
  begin
     biaoji:=i-instrm.Position;//如果没有这里中转，余下部分不能写入
     instrm.ReadBuffer(p,biaoji);
     outstrm.WriteBuffer(p,biaoji);
     break;
  end;
end;
FreeAndNil(instrm);
FreeAndNil(outstrm);
application.MessageBox('复制成功','good',mb_ok);
end;

说明：
while 以4096个char为一块读一程序  do
begin
   if  4096正数倍then
  一块块写入
else
不够4096的把余下的全部写入

结束


为什么是4096呢？
这里只能说方面机算机使用，也可是512 1024  2048 这样的数计算机使用快，内存全部同样
现样你也可以是1  2  3  ....更大的数
还能是
p:array [1..buffsize] of char;
改为:
p:char;
这样会一个字节一个字节的复制
对于大文件来说会慢些而已
TFileStream- 文件流 复制文件（1）
是直接用copyfrom(),方面易懂
在这里我们用一个变量来中转，然后再去保存
var
instrm,outstrm:tfilestream;
i:integer;
p:pchar;
begin
instrm:=tfilestream.Create('c:\my.exe',fmOpenRead);//流打开文件
outstrm:=tfilestream.Create('c:\ok.exe',fmCreate);//流保存的文件
i:=instrm.Size;
instrm.Position:=0;//把流指针放在开始位置,用时要从头读取
getmem(p,i);//分配内存
instrm.readbuffer(p^,i);//这里是P的指针,而不是P
outstrm.Write(p^,i);
freemem(p);
FreeAndNil(instrm);
FreeAndNil(outstrm);
application.MessageBox('复制成功','good',mb_ok);
end;
TFileStream可实现对文件的复制
下面做个例子（我感觉例子是最好的记忆方法）
先放入C下一个文件：my.exe
新建工程，放一button组件
button.caption:=复制

procedure TForm1.Button1Click(Sender: TObject);
var
instrm,outstrm:tfilestream;
begin
instrm:=tfilestream.Create('c:\my.exe',fmOpenRead);//流打开文件
outstrm:=tfilestream.Create('c:\ok.exe',fmCreate);//流保存的文件
outstrm.CopyFrom(instrm,instrm.Size);
FreeAndNil(instrm);
FreeAndNil(outstrm);
application.MessageBox('复制成功','good',mb_ok);
end;

一次很简单的复制成功了

些书由陈国强编写
中文说明
下载点击
/Files/shuyezi122/API32.rar

TStream 是一个抽象的基类, 不能直接生成对象. 在具体的应用中, 主要使用它的子孙类:
TFileStream: 文件流
TStringStream: 字符串流
TMemoryStream: 内存流
TResourceStream: 资源文件流
THandleStream: 是 TFileStream 的父类、TStream 的子类
TCustomMemoryStream: 是 TMemoryStream 和 TResourceStream 的父类、TStream 的子类

System.IsMemoryManagerSet;
System.Move;
System.New;
System.ReallocMem;
System.ReallocMemory;
System.SetMemoryManager;
System.SysAllocMem;
System.SysFreeMem;
System.SysGetMem;
System.SysReallocMem;

SysUtils.DisposeStr;
SysUtils.NewStr;

TlHelp32.Heap32First;
TlHelp32.Heap32ListFirst;
TlHelp32.Heap32ListNext;
TlHelp32.Heap32Next;

Windows.CopyMemory;
Windows.FillMemory;
Windows.GetProcessHeap;
Windows.GetProcessHeaps;
Windows.GlobalAlloc;
Windows.GlobalAllocPtr;
Windows.GlobalCompact;
Windows.GlobalDiscard;
Windows.GlobalFix;
Windows.GlobalFlags;
Windows.GlobalFree;
Windows.GlobalFreePtr;
Windows.GlobalHandle;
Windows.GlobalLock;
Windows.GlobalMemoryStatus;
Windows.GlobalReAlloc;
Windows.GlobalReAllocPtr;
Windows.GlobalSize;
Windows.GlobalUnfix;
Windows.GlobalUnlock;
Windows.GlobalUnWire;
Windows.GlobalWire;
Windows.HeapAlloc;
Windows.HeapCompact;
Windows.HeapCreate;
Windows.HeapDestroy;
Windows.HeapFree;
Windows.HeapLock;
Windows.HeapReAlloc;
Windows.HeapSize;
Windows.HeapUnlock;
Windows.HeapValidate;
Windows.HeapWalk;
Windows.IsBadCodePtr;
Windows.IsBadReadPtr;
Windows.IsBadStringPtr;
Windows.IsBadWritePtr;
Windows.MoveMemory;
Windows.VirtualAlloc;
Windows.VirtualAllocEx;
Windows.VirtualFree;
Windows.VirtualFreeEx;
Windows.VirtualLock;
Windows.VirtualProtect;
Windows.VirtualProtectEx;
Windows.VirtualQuery;
Windows.VirtualQueryEx;
Windows.ZeroMemory;

Windows.LocalAlloc;
Windows.LocalCompact;
Windows.LocalDiscard;
Windows.LocalFlags;
Windows.LocalFree;
Windows.LocalLock;
Windows.LocalReAlloc;
Windows.LocalShrink;
Windows.LocalSize;
Windows.LocalUnlock;

新建
new->other->dll wizard

library new;

uses
  SysUtils,
  Classes,
  Dialogs;

{$R *.res}

procedure dll;
begin
showmessage('delphi');
end;

exports
 dll;

begin
end.

var
  Form1: TForm1;
type
TMB = function(hWnd: HWND; lpText, lpCaption: PChar; uType: UINT): Integer; stdcall;
implementation

{$R *.dfm}
var
 MB: TMB;
 inst: LongWord;

procedure TForm1.Button1Click(Sender: TObject);
var
  t,b: PChar;
begin
inst := LoadLibrary('user32.dll');
 MB := GetProcAddress(inst, 'MessageBoxA'){注意MessageBoxA这里区分大小写,他NND的让我试了半天才知道这里错了,你们也要注意了}
  t := '标题';
  b := '内容';
  MB(0, b, t, 0);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
 FreeLibrary(inst);
end;

MessageBox()是API,对应的在user32.dll中的MessageBoxA()


{注意MessageBoxA这里区分大小写,他NND的让我试了半天才知道这里错了,你们也要注意了}
function msg(h:hwnd;sa,sb:pchar;i:uint):integer;stdcall ;external 'user32.dll' name 'MessageBoxA';
implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
var
  sa,sb:  PChar;
begin
  sa := '标题';
  sb := '内容';
  msg(0,sa,sb,0);
end;
这样msg就等同于MessageBoxA()