Mega Code Archive
Base64 (MIME) Encode and Decode (updated May 2003)
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Title: Base64 (MIME) Encode and Decode (updated May 2003)
Question: 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}
{$ENDIF}
uses SysUtils;
// codiert einen String in die zugehrige Base64-Darstellung
function Base64Encode(const InText: AnsiString): AnsiString; overload;
// decodiert die Base64-Darstellung eines Strings in den zugehrigen String
function Base64Decode(const InText: AnsiString): AnsiString; overload;
// bestimmt die Gre der Base64-Darstellung
function CalcEncodedSize(InSize: Cardinal): Cardinal;
// bestimmt die Gre der binren Darstellung
function CalcDecodedSize(const InBuffer; InSize: Cardinal): Cardinal;
// codiert einen Buffer in die zugehrige Base64-Darstellung
procedure Base64Encode(const InBuffer; InSize: Cardinal; var OutBuffer); overload; register;
// decodiert die Base64-Darstellung in einen Buffer
{$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 zugehrige Base64-Darstellung
procedure Base64Encode(const InText: PAnsiChar; var OutText: PAnsiChar); overload;
// decodiert die Base64-Darstellung eines Strings in den zugehrigen String
procedure Base64Decode(const InText: PAnsiChar; var OutText: PAnsiChar); overload;
// codiert einen String in die zugehrige Base64-Darstellung
procedure Base64Encode(const InText: AnsiString; var OutText: AnsiString); overload;
// decodiert die Base64-Darstellung eines Strings in den zugehrigen 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 // 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.
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