实现对一个文本文件读操作和写操作,如 a.txt 文件,文件内容为:Abcdefafdafdfdsaf
erexdfaffdaffdfsaf
ffsvsfafasfweffagfa
ewrewrewrwerwerf
fsafsgerererwerwgd
bgsdgfdgfdgdfgdffe
ffsafdsfsdafsdfdwer
一个线程对文件内容,进行读,同时将读出的字符进行大写转换,并替换。另一个线程,实现对文件的写操作,不停地随机往文件写入小写字母(如果 dfafsdfsa)。
要求 通过 多线程 和 内核对象 实现。
erexdfaffdaffdfsaf
ffsvsfafasfweffagfa
ewrewrewrwerwerf
fsafsgerererwerwgd
bgsdgfdgfdgdfgdffe
ffsafdsfsdafsdfdwer
一个线程对文件内容,进行读,同时将读出的字符进行大写转换,并替换。另一个线程,实现对文件的写操作,不停地随机往文件写入小写字母(如果 dfafsdfsa)。
要求 通过 多线程 和 内核对象 实现。
unit MainFrm;interfaceuses
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.