delphi中文件比较的类(纯代码)

{---------------------------------------------------------------------------------------
Class: TFileCompare
Version: 1.0
Date: 12 July 2000
Author: Mike GIBBARD
Email: mike.gibbard@burnsecs.com

Description: TFileCompare is a simple class for comparing one file (CompareFileName)
with another (BaseFileName) using the CompareMem function in SysUtils to
perform a binary compare of Length bytes of memory referenced by
BaseFileName to that of CompareFileName.

Properties: * BaseFileName: string - Fully qualified path and filename of the file
against which the comparison will be made

* CompareFileName: string - Fully qualified path and filename of the file
to compared

Copyright: Copyright 2000, Mike Gibbard (hereafter 'the Author').
All Rights Reserved.

IMPORTANT: This software is provided 'as-is', without any express or implied
warranty. In no event will the author be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented, you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.

Example: procedure TForm1.Button1Click(Sender: TObject);
var
FCompare: TFileCompare;
begin
FCompare := TFileCompare.Create;
try
if (Edit1.Text <> '') and (Edit2.Text <> '') then
begin
with FCompare do
begin
BaseFileName := Edit1.Text;
CompareFileName := Edit2.Text;
if CompareFiles then
ShowMessage('Files are the same')
else
ShowMessage('Files are different');
end;
end;
finally
FCompare.Free;
end;
end;

---------------------------------------------------------------------------------------}

unit FileCompare;

interface

uses
Classes, SysUtils;

type
TFileCompare = class(TObject)
private
FBaseFileName: string;
FCompareFileName: string;
FBaseStream: TMemoryStream;
FCompareStream: TMemoryStream;
procedure SetBaseFileName(Val: string);
procedure SetCompareFileName(Val: string);
public
constructor Create;
destructor Destroy; override;
function CompareFiles: boolean;
property BaseFileName: string read FBaseFileName write SetBaseFileName;
property CompareFileName: string read FCompareFileName write SetCompareFileName;
end;

{ In Delphi 5, the CompareMem function is exposed in the SysUtils unit whereas, in
Delphi 2, it's hidden in the Classes unit. I don't know where it appears in Delphi's
3 and 4, so, for convenience, I've included it here}

function CompareMem(P1, P2: Pointer; Length: Integer): Boolean; assembler;


implementation

constructor TFileCompare.Create;
begin
FBaseStream := Nil;
FCompareStream := Nil;
FBaseFileName := '';
FCompareFileName := '';
end;

destructor TFileCompare.Destroy;
begin
inherited Destroy;
end;

procedure TFileCompare.SetBaseFileName(Val: String);
begin
if FileExists(Val) then FBaseFileName := Val
else
raise Exception.Create(Val+' does not exist');
end;

procedure TFileCompare.SetCompareFileName(Val: String);
begin
if FileExists(Val) then FCompareFileName := Val
else
raise Exception.Create(Val+' does not exist');
end;

function TFileCompare.CompareFiles: boolean;
begin
Result := FALSE;
//Instantiate the two memory streams
FBaseStream := TMemoryStream.Create;
FCompareStream := TMemoryStream.Create;

try
//Load both files into their respective streams...
FBaseStream.LoadFromFile(FBaseFileName);
FCompareStream.LoadFromFile(FCompareFileName);

//...and compare them
Result := (FBaseStream.Size = FCompareStream.Size) and
CompareMem(FBaseStream.Memory, FCompareStream.Memory, FBaseStream.Size);
finally
//Tidy up
FBaseStream.Free;
FCompareStream.Free;
FBaseStream := Nil;
FCompareStream := Nil;
end;
end;

function CompareMem(P1, P2: Pointer; Length: Integer): Boolean; assembler;
asm
PUSH ESI
PUSH EDI
MOV ESI,P1
MOV EDI,P2
MOV EDX,ECX
XOR EAX,EAX
AND EDX,3
SHR ECX,2
REPE CMPSD
JNE @@2
MOV ECX,EDX
REPE CMPSB
JNE @@2
@@1: INC EAX
@@2: POP EDI
POP ESI
end;


end.