Изменение регистра символов в файле через отображение в память

{
Copyright © 1999 by Delphi 5 Developer's Guide - Xavier Pacheco and Steve Teixeira
}

unit
 MainFrm;

interface


uses

  Windows, Messages, SysUtils, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls;

const

  FName = 'test.txt';

type


  TMainForm = class
(TForm)
    btnUpperCase: TButton;
    memTextContents: TMemo;
    lblContents: TLabel;
    btnLowerCase: TButton;
    procedure
 btnUpperCaseClick(Sender: TObject);
    procedure
 FormCreate(Sender: TObject);
    procedure
 btnLowerCaseClick(Sender: TObject);
  public

    UCase: Boolean;
    procedure
 ChangeFileCase;
  end
;

var

  MainForm: TMainForm;

implementation


{$R *.DFM}

procedure
 TMainForm.btnUpperCaseClick(Sender: TObject);
begin

  UCase := True;
  ChangeFileCase;
end
;

procedure
 TMainForm.btnLowerCaseClick(Sender: TObject);
begin

  UCase := False;
  ChangeFileCase;
end
;

procedure
 TMainForm.FormCreate(Sender: TObject);
begin

  memTextContents.Lines.LoadFromFile(FName);
  // Change to upper case by default.
  UCase := True;
end
;

procedure
 TMainForm.ChangeFileCase;
var

  FFileHandle: THandle; // Handle to the open file.
  FMapHandle: THandle; // Handle to a file-mapping object
  FFileSize: Integer; // Variable to hold the file size.
  FData: PByte; // Pointer to the file's data when mapped.
  PData: PChar; // Pointer used to reference the file data.
begin


  { First obtain a file handle to the file to be mapped. This code
    assumes the existence of the file. Otherwise, you can use the
    FileCreate() function to create a new file. }

  if
 not
 FileExists(FName) then

    raise
 Exception.Create('File does not exist.')
  else

    FFileHandle := FileOpen(FName, fmOpenReadWrite);

  // If CreateFile() was not successful, raise an exception
  if
 FFileHandle = INVALID_HANDLE_VALUE then

    raise
 Exception.Create('Failed to open or create file');

  try

    { Now obtain the file size which we will pass to the other file-
      mapping functions. We'll make this size one byte larger as we
      need to append a null-terminating character to the end of the
      mapped-file's data.}
    FFileSize := GetFileSize(FFileHandle, nil
);

    { Obtain a file-mapping object handle. If this function is not
       successful, then raise an exception. }
    FMapHandle := CreateFileMapping(FFileHandle, nil
,
      PAGE_READWRITE, 0, FFileSize, nil
);

    if
 FMapHandle = 0 then

      raise
 Exception.Create('Failed to create file mapping');
  finally

    // Release the file handle
    CloseHandle(FFileHandle);
  end
;

  try

    { Map the file-mapping object to a view. This will return a pointer
      to the file data. If this function is not successful, then raise
      an exception. }
    FData := MapViewOfFile(FMapHandle, FILE_MAP_ALL_ACCESS, 0, 0, FFileSize);

    if
 FData = nil
 then

      raise
 Exception.Create('Failed to map view of file');

  finally

    // Release the file-mapping object handle
    CloseHandle(FMapHandle);
  end
;

  try

    { !!! Here is where you would place the functions to work with
    the mapped file's data. For example, the following line forces
    all characters in the file to uppercase }
    PData := PChar(FData);
    // Position the pointer to the end of the file's data
    inc(PData, FFileSize);

    // Append a null-terminating character to the end of the file's data
    PData^ := #0;

    // Now set all characters in the file to uppercase
    if
 UCase then

      StrUpper(PChar(FData))
    else

      StrLower(PChar(FData));

  finally

    // Release the file mapping.
    UnmapViewOfFile(FData);
  end
;
  memTextContents.Lines.Clear;
  memTextContents.Lines.LoadFromFile(FName);
end
;

end
.

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