Base64 (MIME) Encode and Decode (updated May 2003) (Daniel Wischnewski) an article on delphi3000.com ||

Base64 (MIME) Encode and Decode (updated May 2003)
Getting to the base fast!
Product:
Delphi 5.x (or higher) Category:
Algorithm Skill Level: Scoring: Last Update:
04/25/2005
Search Keys:
delphi delphi3000 article borland vcl code-snippet MIME Base64 encode encoding decode decoding Times Scored:
10 Visits:
9355
Uploader: Daniel Wischnewski
Company: Delphi-PRAXiS Reference: gate(n)etwork GmbH
Question/Problem/Abstract:
This article gives you two routines allowing for fast encoding and decoding in and out of the MIME format.
Answer:
Hi folks,

I have written the following unit to replace the INDY TIdEncoderMIME and TIdDecoderMIME components. This "Codec" is used in Email-Software, primarely.

First reason was the lack of speed of these components. Second reason was, that they are components and therefore require the VCL - an heavy extra load on otherwise nonVCL systems.

Both routines are written in Assembler and overloaded by different versions allowing for easy access.

I am sure, some of your are able to increase the speed even some more. Please let me know. Thanks.

Update May 2003

I have introduced a compiler switch to switch between a fast decoding mode and a more secure decoding mode. It is up to you, which you like to use. I recomend using the more secure mode, especially if the user is required to work with the encoded data.

{* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *

 *

 * Unit Name : uBase64Codec

 * Author    : Daniel Wischnewski

 * Copyright : Copyright © 2001-2003 by gate(n)etwork GmbH. All Rights Reserved.

 * Creator   : Daniel Wischnewski

 * Contact   : Daniel Wischnewski (e-mail: delphi3000(at)wischnewski.tv);

 *

 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *}

//                               * * * License * * *

//

// The contents of this file are used with permission, subject to the Mozilla

// Public License Version 1.1 (the "License"); you may not use this file except

// in compliance with the License. You may obtain a copy of the License at

//

//                       http://www.mozilla.org/MPL/MPL-1.1.html

//

// Software distributed under the License is distributed on an "AS IS" basis,

// WITHOUT WARRANTY OF ANY KIND, either express or  implied. See the License for

// the specific language governing rights and limitations under the License.

//

//                               * * * My Wish * * *

//

// If you come to use this unit for your work, I would like to know about it.

// Drop me an e-mail and let me know how it worked out for you. If you wish, you

// can send me a copy of your work. No obligations!

// My e-mail address: delphi3000(at)wischnewski.tv

//

//                               * * * History * * *

//

// Version 1.0 (Oct-10 2002)

//    first published on Delphi-PRAXiS (www.delphipraxis.net)

//

// Version 1.1 (May-13 2003)

//    introduced a compiler switch (SpeedDecode) to switch between a faster

//    decoding variant (prior version) and a litte less fast, but secure variant

//    to work around bad formatted data (decoding only!)

//    

// Version 1.2 (Juni-09 2004)

//    included compiler switch {$0+}. In Delphi 6 and 7 projects using this code 

//    with compiler optimizations turned off will raise an access violation

//    {$O+} will ensure that this unit runs with compiler optimizations.

//    This option does *not* influence other parts of the project including this

//    unit.

//    Thanks to Ralf Manschewski for pointing out this problem.

//

unit Base64;

interface

// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

// !! THE COMPILER SWITCH MAY BE USED TO ADJUST THE BEHAVIOR !!

// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

// enable "SpeedDecode"

//     the switch to gain speed while decoding the message, however, the codec

//     will raise different exceptions/access violations or invalid output if

//     the incoming data is invalid or missized.

// disable "SpeedDecode"

//     the switch to enable a data check, that will scan the data to decode to

//     be valid. This method is to be used if you cannot guarantee to validity

//     of the data to be decoded.

{.DEFINE SpeedDecode}

{$IFNDEF SpeedDecode}

  {$DEFINE ValidityCheck}

{$ENDIF}

uses SysUtils;

  // codiert einen String in die zugehörige Base64-Darstellung

  function Base64Encode(const InText: AnsiString): AnsiString; overload;

  // decodiert die Base64-Darstellung eines Strings in den zugehörigen String

  function Base64Decode(const InText: AnsiString): AnsiString; overload;

  // bestimmt die Größe der Base64-Darstellung

  function CalcEncodedSize(InSize: Cardinal): Cardinal;

  // bestimmt die Größe der binären Darstellung

  function CalcDecodedSize(const InBuffer; InSize: Cardinal): Cardinal;

  // codiert einen Buffer in die zugehörige Base64-Darstellung

  procedure Base64Encode(const InBuffer; InSize: Cardinal; var OutBuffer); overload; register;

  // decodiert die Base64-Darstellung in einen Buffer

  {$IFDEF SpeedDecode}

    procedure Base64Decode(const InBuffer; InSize: Cardinal; var OutBuffer); overload; register;

  {$ENDIF}

  {$IFDEF ValidityCheck}

    function Base64Decode(const InBuffer; InSize: Cardinal; var OutBuffer): Boolean; overload; register;

  {$ENDIF}

  // codiert einen String in die zugehörige Base64-Darstellung

  procedure Base64Encode(const InText: PAnsiChar; var OutText: PAnsiChar); overload;

  // decodiert die Base64-Darstellung eines Strings in den zugehörigen String

  procedure Base64Decode(const InText: PAnsiChar; var OutText: PAnsiChar); overload;

  // codiert einen String in die zugehörige Base64-Darstellung

  procedure Base64Encode(const InText: AnsiString; var OutText: AnsiString); overload;

  // decodiert die Base64-Darstellung eines Strings in den zugehörigen String

  procedure Base64Decode(const InText: AnsiString; var OutText: AnsiString); overload;

implementation

const

  cBase64Codec: array[0..63] of AnsiChar =

    'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

  Base64Filler = '=';

function Base64Encode(const InText: string): string; overload;

begin

  Base64Encode(InText, Result);

end;

function Base64Decode(const InText: string): string; overload;

begin

  Base64Decode(InText, Result);

end;

function CalcEncodedSize(InSize: Cardinal): Cardinal;

begin

  // no buffers passed along, calculate outbuffer size needed

  Result := (InSize div 3) shl 2;

  if ((InSize mod 3) > 0)

  then Inc(Result, 4);

end;

function CalcDecodedSize(const InBuffer; InSize: Cardinal): Cardinal;

type

  BA = array of Byte;

begin

  Result := 0;

  if InSize = 0 then

    Exit;

  if InSize mod 4 <> 0 then

    Exit;

  Result := InSize div 4 * 3;

  if (BA(InBuffer)[InSize - 2] = Ord(Base64Filler))

  then Dec(Result, 2)

  else if BA(InBuffer)[InSize - 1] = Ord(Base64Filler)

       then Dec(Result);

end;

procedure Base64Encode(const InBuffer; InSize: Cardinal; var OutBuffer

    ); register;

var

  ByThrees, LeftOver: Cardinal;

  // reset in- and outbytes positions

asm

  // load addresses for source and destination

  // PBYTE(InBuffer);

  mov  ESI, [EAX]

  // PBYTE(OutBuffer);

  mov  EDI, [ECX]

  // ByThrees := InSize div 3;

  // LeftOver := InSize mod 3;

  // load InSize (stored in EBX)

  mov  EAX, EBX

  // load 3

  mov  ECX, $03

  // clear upper 32 bits

  xor  EDX, EDX

  // divide by ECX

  div  ECX

  // save result

  mov  ByThrees, EAX

  // save remainder

  mov  LeftOver, EDX

  // load addresses

  lea  ECX, cBase64Codec[0]

  // while I < ByThrees do

  // begin

  xor  EAX, EAX

  xor  EBX, EBX

  xor  EDX, EDX

  cmp  ByThrees, 0

  jz   @@LeftOver

  @@LoopStart:

    // load the first two bytes of the source triplet

    LODSW

    // write Bits 0..5 to destination

    mov  BL, AL

    shr  BL, 2

    mov  DL, BYTE PTR [ECX + EBX]

    // save the Bits 12..15 for later use [1]

    mov  BH, AH

    and  BH, $0F

    // save Bits 6..11

    rol  AX, 4

    and  AX, $3F

    mov  DH, BYTE PTR [ECX + EAX]

    mov  AX, DX

    // store the first two bytes of the destination quadruple

    STOSW

    // laod last byte (Bits 16..23) of the source triplet

    LODSB

    // extend bits 12..15 [1] with Bits 16..17 and save them

    mov  BL, AL

    shr  BX, 6

    mov  DL, BYTE PTR [ECX + EBX]

    // save bits 18..23

    and  AL, $3F

    xor  AH, AH

    mov  DH, BYTE PTR [ECX + EAX]

    mov  AX, DX

    // store the last two bytes of the destination quadruple

    STOSW

    dec  ByThrees

  jnz  @@LoopStart

  @@LeftOver:

  // there are up to two more bytes to encode

  cmp  LeftOver, 0

  jz   @@Done

  // clear result

  xor  EAX, EAX

  xor  EBX, EBX

  xor  EDX, EDX

  // get left over 1

  LODSB

  // load the first six bits

  shl  AX, 6

  mov  BL, AH

  // save them

  mov  DL, BYTE PTR [ECX + EBX]

  // another byte ?

  dec  LeftOver

  jz   @@SaveOne

  // save remaining two bits

  shl  AX, 2

  and  AH, $03

  // get left over 2

  LODSB

  // load next 4 bits

  shl  AX, 4

  mov  BL, AH

  // save all 6 bits

  mov  DH, BYTE PTR [ECX + EBX]

  shl  EDX, 16

  // save last 4 bits

  shr  AL, 2

  mov  BL, AL

  // save them

  mov  DL, BYTE PTR [ECX + EBX]

  // load base 64 'no more data flag'

  mov  DH, Base64Filler

  jmp  @@WriteLast4

  @@SaveOne:

  // adjust the last two bits

  shr  AL, 2

  mov  BL, AL

  // save them

  mov  DH, BYTE PTR [ECX + EBX]

  shl  EDX, 16

  // load base 64 'no more data flags'

  mov  DH, Base64Filler

  mov  DL, Base64Filler

  // ignore jump, as jump reference is next line !

  // jmp  @@WriteLast4

  @@WriteLast4:

    // load and adjust result

    mov  EAX, EDX

    ror EAX, 16

    // save it to destination

    STOSD

  @@Done:

end;

{$IFDEF SpeedDecode}

  procedure Base64Decode(const InBuffer; InSize: Cardinal; var OutBuffer);

      overload; register;

{$ENDIF}

{$IFDEF ValidityCheck}

  function Base64Decode(const InBuffer; InSize: Cardinal; var OutBuffer):

      Boolean; overload; register;

{$ENDIF}

const

  {$IFDEF SpeedDecode}

    cBase64Codec: array[0..127] of Byte =

  {$ENDIF}

  {$IFDEF ValidityCheck}

    cBase64Codec: array[0..255] of Byte =

  {$ENDIF}

  (

    $FF, $FF, $FF, $FF, $FF, {005>} $FF, $FF, $FF, $FF, $FF, // 000..009

    $FF, $FF, $FF, $FF, $FF, {015>} $FF, $FF, $FF, $FF, $FF, // 010..019

    $FF, $FF, $FF, $FF, $FF, {025>} $FF, $FF, $FF, $FF, $FF, // 020..029

    $FF, $FF, $FF, $FF, $FF, {035>} $FF, $FF, $FF, $FF, $FF, // 030..039

    $FF, $FF, $FF, $3E, $FF, {045>} $FF, $FF, $3F, $34, $35, // 040..049

    $36, $37, $38, $39, $3A, {055>} $3B, $3C, $3D, $FF, $FF, // 050..059

    $FF, $FF, $FF, $FF, $FF, {065>} $00, $01, $02, $03, $04, // 060..069

    $05, $06, $07, $08, $09, {075>} $0A, $0B, $0C, $0D, $0E, // 070..079

    $0F, $10, $11, $12, $13, {085>} $14, $15, $16, $17, $18, // 080..089

    $19, $FF, $FF, $FF, $FF, {095>} $FF, $FF, $1A, $1B, $1C, // 090..099

    $1D, $1E, $1F, $20, $21, {105>} $22, $23, $24, $25, $26, // 100..109

    $27, $28, $29, $2A, $2B, {115>} $2C, $2D, $2E, $2F, $30, // 110..119

    $31, $32, $33, $FF, $FF, {125>} $FF, $FF, $FF            // 120..127

    {$IFDEF ValidityCheck}

                               {125>}              , $FF, $FF, // 128..129

      $FF, $FF, $FF, $FF, $FF, {135>} $FF, $FF, $FF, $FF, $FF, // 130..139

      $FF, $FF, $FF, $FF, $FF, {145>} $FF, $FF, $FF, $FF, $FF, // 140..149

      $FF, $FF, $FF, $FF, $FF, {155>} $FF, $FF, $FF, $FF, $FF, // 150..159

      $FF, $FF, $FF, $FF, $FF, {165>} $FF, $FF, $FF, $FF, $FF, // 160..169

      $FF, $FF, $FF, $FF, $FF, {175>} $FF, $FF, $FF, $FF, $FF, // 170..179

      $FF, $FF, $FF, $FF, $FF, {185>} $FF, $FF, $FF, $FF, $FF, // 180..189

      $FF, $FF, $FF, $FF, $FF, {195>} $FF, $FF, $FF, $FF, $FF, // 190..199

      $FF, $FF, $FF, $FF, $FF, {205>} $FF, $FF, $FF, $FF, $FF, // 200..209

      $FF, $FF, $FF, $FF, $FF, {215>} $FF, $FF, $FF, $FF, $FF, // 210..219

      $FF, $FF, $FF, $FF, $FF, {225>} $FF, $FF, $FF, $FF, $FF, // 220..229

      $FF, $FF, $FF, $FF, $FF, {235>} $FF, $FF, $FF, $FF, $FF, // 230..239

      $FF, $FF, $FF, $FF, $FF, {245>} $FF, $FF, $FF, $FF, $FF, // 240..249

      $FF, $FF, $FF, $FF, $FF, {255>} $FF                      // 250..255

    {$ENDIF}

  );

asm

  push EBX

  mov  ESI, [EAX]

  mov  EDI, [ECX]

  {$IFDEF ValidityCheck}

    mov  EAX, InSize

    and  EAX, $03

    cmp  EAX, $00

    jz   @@DecodeStart

    jmp  @@ErrorDone

    @@DecodeStart:

  {$ENDIF}

  mov  EAX, InSize

  shr  EAX, 2

  jz   @@Done

  lea  ECX, cBase64Codec[0]

  xor  EBX, EBX

  dec  EAX

  jz   @@LeftOver

  push EBP

  mov  EBP, EAX

  @@LoopStart:

    // load four bytes into EAX

    LODSD

    // save them to EDX as AX is used to store results

    mov  EDX, EAX

    // get bits 0..5

    mov  BL, DL

    // decode

    mov  AH, BYTE PTR [ECX + EBX]

    {$IFDEF ValidityCheck}

      // check valid code

      cmp  AH, $FF

      jz   @@ErrorDoneAndPopEBP

    {$ENDIF}

    // get bits 6..11

    mov  BL, DH

    // decode

    mov  AL, BYTE PTR [ECX + EBX]

    {$IFDEF ValidityCheck}

      // check valid code

      cmp  AL, $FF

      jz   @@ErrorDoneAndPopEBP

    {$ENDIF}

    // align last 6 bits

    shl  AL, 2

    // get first 8 bits

    ror  AX, 6

    // store first byte

    STOSB

    // align remaining 4 bits

    shr  AX, 12

    // get next two bytes from source quad

    shr  EDX, 16

    // load bits 12..17

    mov  BL, DL

    // decode

    mov  AH, BYTE PTR [ECX + EBX]

    {$IFDEF ValidityCheck}

      // check valid code

      cmp  AH, $FF

      jz   @@ErrorDoneAndPopEBP

    {$ENDIF}

    // align ...

    shl  AH, 2

    // ... and adjust

    rol  AX, 4

    // get last bits 18..23

    mov  BL, DH

    // decord

    mov  BL, BYTE PTR [ECX + EBX]

    {$IFDEF ValidityCheck}

      // check valid code

      cmp  BL, $FF

      jz   @@ErrorDoneAndPopEBP

    {$ENDIF}

    // enter in destination word

    or   AH, BL

    // and store to destination

    STOSW

    // more coming ?

    dec  EBP

  jnz  @@LoopStart

  pop  EBP

  // no

  // last four bytes are handled separately, as special checking is needed

  // on the last two bytes (may be end of data signals '=' or '==')

  @@LeftOver:

  // get the last four bytes

  LODSD

  // save them to EDX as AX is used to store results

  mov  EDX, EAX

  // get bits 0..5

  mov  BL, DL

  // decode

  mov  AH, BYTE PTR [ECX + EBX]

  {$IFDEF ValidityCheck}

    // check valid code

    cmp  AH, $FF

    jz   @@ErrorDone

  {$ENDIF}

  // get bits 6..11

  mov  BL, DH

  // decode

  mov  AL, BYTE PTR [ECX + EBX]

  {$IFDEF ValidityCheck}

    // check valid code

    cmp  AL, $FF

    jz   @@ErrorDone

  {$ENDIF}

  // align last 6 bits

  shl  AL, 2

  // get first 8 bits

  ror  AX, 6

  // store first byte

  STOSB

  // get next two bytes from source quad

  shr  EDX, 16

  // check DL for "end of data signal"

  cmp  DL, Base64Filler

  jz   @@SuccessDone

  // align remaining 4 bits

  shr  AX, 12

  // load bits 12..17

  mov  BL, DL

  // decode

  mov  AH, BYTE PTR [ECX + EBX]

  {$IFDEF ValidityCheck}

    // check valid code

    cmp  AH, $FF

    jz   @@ErrorDone

  {$ENDIF}

  // align ...

  shl  AH, 2

  // ... and adjust

  rol  AX, 4

  // store second byte

  STOSB

  // check DH for "end of data signal"

  cmp  DH, Base64Filler

  jz   @@SuccessDone

  // get last bits 18..23

  mov  BL, DH

  // decord

  mov  BL, BYTE PTR [ECX + EBX]

  {$IFDEF ValidityCheck}

    // check valid code

    cmp  BL, $FF

    jz   @@ErrorDone

  {$ENDIF}

  // enter in destination word

  or   AH, BL

  // AH - AL for saving last byte

  mov  AL, AH

  // store third byte

  STOSB

  @@SuccessDone:

  {$IFDEF ValidityCheck}

    mov  Result, $01

    jmp  @@Done

    @@ErrorDoneAndPopEBP:

    pop  EBP

    @@ErrorDone:

    mov  Result, $00

  {$ENDIF}

  @@Done:

  pop  EBX

end;

procedure Base64Encode(const InText: PAnsiChar; var OutText: PAnsiChar);

var

  InSize, OutSize: Cardinal;

begin

  // get size of source

  InSize := Length(InText);

  // calculate size for destination

  OutSize := CalcEncodedSize(InSize);

  // reserve memory

  OutText := StrAlloc(Succ(OutSize));

  OutText[OutSize] := #0;

  // encode !

  Base64Encode(InText, InSize, OutText);

end;

procedure Base64Encode(const InText: AnsiString; var OutText: AnsiString);

    overload;

var

  InSize, OutSize: Cardinal;

  PIn, POut: Pointer;

begin

  // get size of source

  InSize := Length(InText);

  // calculate size for destination

  OutSize := CalcEncodedSize(InSize);

  // prepare string length to fit result data

  SetLength(OutText, OutSize);

  PIn := @InText[1];

  POut := @OutText[1];

  // encode !

  Base64Encode(PIn, InSize, POut);

end;

procedure Base64Decode(const InText: PAnsiChar; var OutText: PAnsiChar);

    overload;

var

  InSize, OutSize: Cardinal;

begin

  // get size of source

  InSize := Length(InText);

  // calculate size for destination

  OutSize := CalcDecodedSize(InText, InSize);

  // reserve memory

  OutText := StrAlloc(Succ(OutSize));

  OutText[OutSize] := #0;

  // encode !

  {$IFDEF SpeedDecode}

    Base64Decode(InText, InSize, OutText);

  {$ENDIF}

  {$IFDEF ValidityCheck}

    if not Base64Decode(InText, InSize, OutText) then

      OutText[0] := #0;

  {$ENDIF}

end;

procedure Base64Decode(const InText: AnsiString; var OutText: AnsiString);

    overload;

var

  InSize, OutSize: Cardinal;

  PIn, POut: Pointer;

begin

  // get size of source

  InSize := Length(InText);

  // calculate size for destination

  PIn := @InText[1];

  OutSize := CalcDecodedSize(PIn, InSize);

  // prepare string length to fit result data

  SetLength(OutText, OutSize);

  FillChar(OutText[1], OutSize, '.');

  POut := @OutText[1];

  // encode !

  {$IFDEF SpeedDecode}

    Base64Decode(PIn, InSize, POut);

  {$ENDIF}

  {$IFDEF ValidityCheck}

    if not Base64Decode(PIn, InSize, POut) then

      SetLength(OutText, 0);

  {$ENDIF}

end;

end.