記憶體管理[4]

一個使用私人堆的例子:

unit Unit1;interfaceuses  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,  Dialogs, StdCtrls;type  TForm1 = class(TForm)    Button1: TButton;    procedure Button1Click(Sender: TObject);  end;var  Form1: TForm1;implementation{$R *.dfm}var  MyHeap: THandle; {堆控制代碼}  p: Pointer;procedure TForm1.Button1Click(Sender: TObject);var  i,num: Integer;  p2: Pointer;  str: string;begin  {建立堆}  MyHeap := HeapCreate(HEAP_ZERO_MEMORY, 1024*1024*2, 0); {建立個 2M 的堆}  if Myheap = 0 then Exit; {如果建立失敗則退出}  {從堆中分配記憶體}  p := HeapAlloc(MyHeap, 0, 7);  if p = nil then Exit; {出錯退出}  {擷取記憶體塊大小}  num := HeapSize(MyHeap, 0, p);  {給記憶體塊的每個位元組賦值}  p2 := p;  for i := 0 to num - 1 do  begin    Byte(p2^) := i + 65;    p2 := Ptr(Integer(p2) + 1);  end;  {取值}  p2 := p;  str := '';  for i := 0 to num - 1 do  begin    str := str + Chr(Byte(p2^));    p2 := Ptr(Integer(p2) + 1);  end;  {顯示記憶體塊的內容與大小}  ShowMessageFmt('%s,%d',[str,num]); {ABCDEFG,7}  /////////////////////////////////////////////////////  {擴充記憶體, 只此一句不同, 下面都是重複上面的代碼}  p := HeapReAlloc(MyHeap, 0, p, 26);  if p = nil then Exit; {出錯退出}  {擷取記憶體塊大小}  num := HeapSize(MyHeap, 0, p);  {給記憶體塊的每個位元組賦值}  p2 := p;  for i := 0 to num - 1 do  begin    Byte(p2^) := i + 65;    p2 := Ptr(Integer(p2) + 1);  end;  {取值}  p2 := p;  str := '';  for i := 0 to num - 1 do  begin    str := str + Chr(Byte(p2^));    p2 := Ptr(Integer(p2) + 1);  end;  {顯示記憶體塊的內容與大小}  ShowMessageFmt('%s,%d',[str,num]); {ABCDEFGHIJKLMNOPQRSTUVWXYZ,26}  /////////////////////////////////////////////////////  {釋放記憶體}  HeapFree(MyHeap, 0, p);  {銷毀堆}  HeapDestroy(MyHeap);end;end.