delphi-改进获取文件MD5 Hash方法

序言

之前所说的获取文件MD5方法有性能问题，没多久我就遇到了，程序假死，卡顿。因此将获取文件MD5的方法改了一下，并测试了一下，大概性能提升了5倍，获取同一个文件的MD5，老方法用时是新方法的6倍。

改进

原始获取文件MD5的方法：

// uses IdHashMessageDigest

Function StreamToMD5(s: TFileStream): string;

var

MD5Encode: TIdHashMessageDigest5;

begin

MD5Encode := TIdHashMessageDigest5.Create;

try

result := MD5Encode.HashStreamAsHex(s);

finally

MD5Encode.Free;

end;

end;Copy

改进后的方法：

// uses System.Hash

Function GetFileHashMD5(FileName: String): String;

var

HashMD5: THashMD5;

BufLen, Readed: integer;

Stream: TFileStream;

Buffer: Pointer;

begin

HashMD5 := THashMD5.Create;

BufLen := 16 * 1024;

Buffer := AllocMem(BufLen);

try

Stream := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);

try

while Stream.Position < Stream.size do

begin

Readed := Stream.Read(Buffer^, BufLen);

if Readed > 0 then

begin

HashMD5.update(Buffer^, Readed);

end;

finally

Stream.Free;

end;

finally

FreeMem(Buffer)

end;

result := HashMD5.HashAsString.ToUpper;

end;Copy

测试结果

文件大小原方法用时新方法用时

1KB 00:00:00.013 00:00:00.001

10KB 00:00:00.020 00:00:00.001

100KB 00:00:00.010 00:00:00.001

1MB 00:00:00.069 00:00:00.008

10MB 00:00:00.455 00:00:00.091

100MB 00:00:04.338 00:00:00.771

1GB 00:00:36.306 00:00:07.451

2GB 00:01:13:218 00:00:15:101

3GB 00:02:19:977 00:00:23:119

4GB 00:02:25:502 00:00:30:106

以上测试结果肯定有偏差，因此将测试程序源码附上，以供需要的参考，程序界面：

unit Unit3;

interface

uses

Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,

Vcl.Controls, Vcl.Forms, Vcl.Dialogs, System.Hash, IdHashMessageDigest,

Vcl.StdCtrls, System.Math, IdGlobalProtocols;

type

TForm2 = class(TForm)

OpenDialog1: TOpenDialog;

Button1: TButton;

Button2: TButton;

Label1: TLabel;

Label2: TLabel;

Label3: TLabel;

Label4: TLabel;

Label5: TLabel;

Label6: TLabel;

Label7: TLabel;

Label8: TLabel;

procedure Button1Click(Sender: TObject);

procedure Button2Click(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form2: TForm2;

Function TransFloatToStr(Avalue: Double; ADigits: integer): String;

implementation

{$R *.dfm}

Function StreamToMD5(s: TFileStream): string;

var

MD5Encode: TIdHashMessageDigest5;

begin

MD5Encode := TIdHashMessageDigest5.Create;

try

result := MD5Encode.HashStreamAsHex(s);

finally

MD5Encode.Free;

end;

Function GetFileHashMD5(FileName: String): String;

var

HashMD5: THashMD5;

BufLen, Readed: integer;

Stream: TFileStream;

Buffer: Pointer;

begin

HashMD5 := THashMD5.Create;

BufLen := 16 * 1024;

Buffer := AllocMem(BufLen);

try

Stream := TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);

try

while Stream.Position < Stream.size do

begin

Readed := Stream.Read(Buffer^, BufLen);

if Readed > 0 then

begin

HashMD5.update(Buffer^, Readed);

end;

finally

Stream.Free;

end;

finally

FreeMem(Buffer)

end;

result := HashMD5.HashAsString.ToUpper;

end;

function TransBytesToSize(Bytes: integer): String;

var

temp: String;

begin

if Bytes < 1024 then { 字节 }

begin

result := IntToStr(Bytes) + ' Byte';

end

else if Bytes < 1024 * 1024 then { KB }

begin

temp := TransFloatToStr(Bytes / 1024, 2);

result := temp + ' KB';

end

else if Bytes < 1024 * 1024 * 1024 then { MB }

begin

temp := TransFloatToStr(Bytes / (1024 * 1024), 2);

result := temp + ' MB';

end

else { GB }

begin

temp := TransFloatToStr(Bytes / (1024 * 1024 * 1024), 2);

result := temp + ' GB';

end

end;

Function TransFloatToStr(Avalue: Double; ADigits: integer): String;

var

v: Double;

p: integer;

e: String;

begin

if abs(Avalue) < 1 then

begin

result := FloatToStr(Avalue);

p := Pos('E', result);

if p > 0 then

begin

e := copy(result, p, length(result));

setlength(result, p - 1);

v := RoundTo(StrToFloat(result), -ADigits);

result := FloatToStr(v) + e;

end

else

result := FloatToStr(RoundTo(Avalue, -ADigits));

end

else

result := FloatToStr(RoundTo(Avalue, -ADigits));

end;

procedure TForm2.Button1Click(Sender: TObject);

var

path: string;

FileName: string;

MD5: string;

bytes: Integer;

size: string;

d1 : TDateTime;

begin

if OpenDialog1.Execute then

begin

FileName := ExtractFileName(OpenDialog1.FileName);

path := OpenDialog1.FileName;

d1 := Now();

MD5 := StreamToMD5(TFileStream.Create(path, fmOpenRead or fmShareDenyWrite));

Label4.Caption := FormatDateTime('hh:nn:ss.zzz', (Now-d1));

bytes := FileSizeByName(path);

size := TransBytesToSize(bytes);

Label2.Caption := MD5;

Label3.Caption := size;

end;

procedure TForm2.Button2Click(Sender: TObject);

var

path: string;

FileName: string;

MD5: string;

bytes: Integer;

size: string;

d2: TDateTime;

begin

if OpenDialog1.Execute then

begin

FileName := ExtractFileName(OpenDialog1.FileName);

path := OpenDialog1.FileName;

d2 := Now();

MD5 := GetFileHashMD5(path);

Label8.Caption := FormatDateTime('hh:nn:ss.zzz', (Now-d2));

bytes := FileSizeByName(path);

size := TransBytesToSize(bytes);

Label6.Caption := MD5;

Label7.Caption := size;

end;

end.

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