Delphi large file read and write use MapViewOfFile

UnitFilemap;InterfaceusesWindows, Messages, sysutils, variants, Classes, Graphics, Controls, Forms, Dialogs, Stdctrls;ConstFileName='MyTest.txt';typeTForm1=class(tform) Btnupper:tbutton;    Btnlower:tbutton;    Txtcontent:tmemo;    Label1:tlabel;    Btnclose:tbutton; procedureformcreate (Sender:tobject); procedureBtnupperclick (Sender:tobject); procedureBtnlowerclick (Sender:tobject); procedureBtncloseclick (Sender:tobject); Private    {Private Declarations}   PublicUcase:boolean; procedurechangefilecase; End;varForm1:tform1;Implementation{$R *.DFM}//TxtContent.Lines.LoadFromFile (FileName) in the full text is intended only to show file modification resultsproceduretform1.formcreate (sender:tobject);begintxtcontent.clear ();    TxtContent.Lines.LoadFromFile (FileName); //turn it to uppercase by defaultUCase: =True;End;procedureTform1.btnupperclick (sender:tobject);beginUCase:=true; Changefilecase;End;procedureTform1.btnlowerclick (sender:tobject);beginUCase:=false; Changefilecase;End;procedureTform1.changefilecase;//This is the core operations section of this sample filevarFfilehandle:thandle;    Fmaphandle:thandle;    Ffilesize:integer;    Fdata:pbyte; Pdata:pchar;begin//-------------------1 Determine if the file exists----------------------//    if  notFileExists (FileName) Then        RaiseException.Create('file does not exist!')    Else//-------------------2 Get a file using FileOpen handle--------//Ffilehandle: =FileOPen (Filename,fmopenreadwrite); //throws an exception if a file fails to be created    ifFfilehandle = Invalid_handle_value Then        RaiseException.Create('failed to open or create file! ');//-------------------3 using createfilemapping to create a file-mapping object for the handle that you just created with FileOpen--//    Tryffilesize:= GetFileSize (Ffilehandle,Nil); Fmaphandle:= CreateFileMapping (Ffilehandle,Nil, Page_readwrite,0, Ffilesize,Nil); ifFmaphandle =0  Then            RaiseException.Create('failed to create memory-mapped file! '); finallyCloseHandle (Ffilehandle); End;//-------------------4 Use MapViewOfFile to create a view of the createfilemapping established handle mapping file toThe address space of the process------//    TryFData:= MapViewOfFile (fmaphandle,file_map_all_access,0,0, ffilesize); ifFData =Nil  Then            RaiseException.Create('mapping file failed!'); finallyCloseHandle (Fmaphandle); End;//-------------------5 to perform the corresponding operation on the pointer returned by the mapviewoffile------//    TryPData:=PChar (FData);        Inc (Pdata,ffilesize); pdata^:= #0; ifUCase ThenStrupper (PChar (FData))ElseStrlower (PChar (FData)); finally//-------------------6 Canceling the mapping of the File View------//UnmapViewOfFile (FData); End;    TxtContent.Lines.Clear (); TxtContent.Lines.LoadFromFile (fileName);End;procedureTform1.btncloseclick (sender:tobject);beginform1.close ();End;End.{-------------------------------------------------------//When you do a pointer-specific operation, you can use this to directly get the value of a type at that pointer procedure     Tform1.button1click (Sender:tobject); var I:integer;   P:pointer;begin I: = 12345678;   P: = @i;   ShowMessage (IntToStr (p));   My Computer on 1242664, this is an address showmessage (IntToStr (Pinteger (p) ^)); 12345678 ShowMessage (IntToStr (Pword (p) ^)); 24910end; Pinteger (p) ^ indicates that pointer p obtains an integer value Pword (p) ^ indicates that a word value is obtained at pointer P

Many pointer types are also defined in Windows.pas and System.pas as follows Pinteger = ^integer; {$NODEFINE Pinteger}    {defined in sysmac.h}pcardinal=^cardinal; Pword=^word; Psmallint= ^smallint;{$NODEFINE Psmallint}   {defined in sysmac.h}  {$POINTERMATH on}pbyte= ^byte;{$NODEFINE pbyte}       {defined in sysmac.h}  {$POINTERMATH OFF}Pshortint= ^shortint;{$NODEFINE Pshortint}   {defined in sysmac.h}PInt64= ^int64;{$NODEFINE PInt64}      {defined in sysmac.h}PUInt64=^uint64; Plongword= ^longword;{$NODEFINE Plongword}   {defined in sysmac.h}Psingle= ^single;{$NODEFINE Psingle}     {defined in sysmac.h}pdouble= ^double;{$NODEFINE pdouble}     {defined in sysmac.h}PDate= ^doub

Delphi large file read and write use MapViewOfFile