汇编写的BASE64

unit Base64;

{

procedure TForm1.Button1Click(Sender: TObject);

var

  Source, Dest: TStream;

begin

  if OpenDialog1.Execute then

  begin

    Source := TFileStream.Create(OpenDialog1.FileName, fmOpenRead); // 打开源文件

    Dest := TFileStream.Create('Base64EncodeTest.txt', fmCreate); // Base64编码文件

    try

      Base64Encode(Source, Dest);

    finally

      Source.Free;

      Dest.Free;

    end;

    Source := TFileStream.Create('Base64EncodeTest.txt', fmOpenRead); // 打开编码文件

    Dest := TFileStream.Create('2.exe', fmCreate); // 还原源文件内容

    try

      Base64Decode(Source, Dest);

      Dest.Position := 0;

    finally

      Source.Free;

      Dest.Free;

    end;

  end;

end;

}

interface

uses

  SysUtils, Classes;

type

{$IFDEF UNICODE}

  Base64String = AnsiString;

{$ELSE}

  Base64String = string;

{$ENDIF}

// 按源长度SourceSize返回Base64编码所需缓冲区字节数

function Base64EncodeBufSize(SourceSize: Integer): Integer;

// 获取Sourec的Base64编码，Base64Buf必须有足够长度。返回实际编码字节数

function Base64Encode(const Source; SourceSize: Integer; var Base64Buf): Integer; overload;

// 将Source编码为Base64字符串返回

function Base64Encode(const Source; SourceSize: Integer): Base64String; overload;

// 将Source从StartPos开始的Size长度的内容源编码为Base64，写入流Dest。

// Size=0 表示一直编码到文件尾

procedure Base64Encode(Source, Dest: TStream; StartPos: Int64 = 0; Size: Int64 = 0); overload;

// 把字符串Str编码为Base64字符串返回

{$IFDEF UNICODE}

function StrToBase64(const Str: AnsiString): Base64String; overload;

function StrToBase64(const Str: string): Base64String; overload;

{$ELSE}

function StrToBase64(const Str: string): Base64String;

{$ENDIF}

// 按给定的编码源Source和长度SourceSize计算并返回解码缓冲区所需字节数

function Base64DecodeBufSize(const Base64Source; SourceSize: Integer): Integer;

// 将Base64编码源Base64Source解码，Buf必须有足够长度。返回实际解码字节数

function Base64Decode(const Base64Source; SourceSize: Integer; var Buf): Integer; overload;

// 将Source从StartPos开始的Size长度的Base64编码内容解码，写入流Dest。

// Size=0 表示一直解码到文件尾

procedure Base64Decode(Source, Dest: TStream; StartPos: Int64 = 0; Size: Int64 = 0); overload;

// 将Base64编码源Base64Source解码为字符串返回

function Base64Decode(const Base64Source; SourceSize: Integer): string; overload;

// 把Base64字符串Base64Str解码为字符串返回

function Base64ToStr(const Base64Str: Base64String): string;

implementation

const

  Base64_Chars: array[0..63] of AnsiChar = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

  Base64_Bytes: array[0..79] of Byte = (62, 0, 0, 0, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 0, 0, 0, 0, 0, 0, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51);

type

  Base64Proc = function(const Source; SourceSize: Integer; var Buf): Integer;

procedure Base64Stream(Source, Dest: TStream; Proc: Base64Proc; StartPos, Size: Int64; RBufSize, WBufSize: Integer);

var

  RBuf: array of Byte;

  WBuf: array of Byte;

  RSize, WSize: Integer;

begin

  if (StartPos < 0) or (StartPos >= Source.Size) then

    Exit;

  Source.Position := StartPos;

  if (Size <= 0) or (Size > Source.Size - Source.Position) then

    Size := Source.Size

  else

    Size := Size + Source.Position;

  SetLength(RBuf, RBufSize);

  SetLength(WBuf, WBufSize);

  while Size <> Source.Position do

  begin

    if RBufSize > Size - Source.Position then

      RBufSize := Size - Source.Position;

    RSize := Source.Read(RBuf[0], RBufSize);

    WSize := Proc(RBuf[0], RSize, WBuf[0]);

    Dest.Write(WBuf[0], WSize);

  end;

end;

function Base64EncodeBufSize(SourceSize: Integer): Integer;

begin

  Result := ((SourceSize + 2) div 3) shl 2;

end;

(****************************************************************************

* *

* BASE64 Encode hint: *

* *

* addr: (high) 4 byte 3 byte 2 byte 1 byte (low) *

* sourec ASCII(3 bytes): 33333333 22222222 11111111 *

* bswap: 11111111 22222222 33333333 00000000 *

* b4 = Base64_Chars[(source >> 8) & 63]: [00333333]->44444444 *

* b3 = Base64_Chars[(source >> 14) & 63]: [00222233]->33333333 *

* b2 = Base64_Chars[(source >> 20) & 63]: [00112222]->22222222 *

* b1 = Base64_Chars[source >> 26]: [00111111]->11111111 *

* b4 << 24 b3 << 16 b2 << 8 b1 *

* dest BASE64(4 bytes) 44444444 33333333 22222222 11111111 *

* *

****************************************************************************)

function Base64Encode(const Source; SourceSize: Integer; var Base64Buf): Integer;

asm

        push    ebp

        push    esi

        push    edi

        push    ebx

        mov     esi, eax // esi = Source

        mov     edi, ecx // edi = Buf

        mov     eax, edx

        cdq

        mov     ecx, 3

        DIV     ecx // edx = SourceSize % 3

        mov     ecx, eax // ecx = SourceSize / 3

        test    edx, edx

        jz      @@1

        inc     eax // eax = (SourceSize + 2) / 3

@@1:

        push    eax

        push    edx

        lea     ebp, Base64_Chars

        jecxz   @Last

        cld

@EncodeLoop: // while (ecx > 0){

        mov     edx, [esi] // edx = 00000000 33333333 22222222 11111111

        bswap   edx // edx = 11111111 22222222 33333333 00000000

        push    edx

        push    edx

        push    edx

        pop     ebx // ebx = edx

        SHR     edx, 20

        SHR     ebx, 26 // ebx = 00111111

        AND     edx, 63 // edx = 00112222

        mov     ah, [ebp + edx] // *(word*)edi = (Base64_Chars[edx] << 8) |

        mov     al, [ebp + ebx] // Base64_Chars[ebx]

        stosw // edi += 2

        pop     edx // edx = 11111111 22222222 33333333 00000000

        pop     ebx // ebx = edx

        SHR     edx, 8

        SHR     ebx, 14

        AND     edx, 63 // edx = 00333333

        AND     ebx, 63 // ebx = 00222233

        mov     ah, [ebp + edx] // *(word*)edi = (Base64_Chars[edx] << 8) |

        mov     al, [ebp + ebx] // Base64_Chars[ebx]

        stosw // edi += 2

        add     esi, 3 // esi += 3

        loop    @EncodeLoop // }

@Last:

        pop     ecx // ecx = SourceSize % 3

        jecxz   @END // if (ecx == 0) return

        mov     eax, 3d3d0000h // preset 2 bytes '='

        mov     [edi], eax

        test    ecx, 2

        jnz     @@3

        mov     al, [esi] // if (ecx == 1)

        SHL     eax, 4 // eax = *esi << 4

        jmp     @@4

@@3:

        mov     ax, [esi] // else

        xchg    al, ah // eax = ((*esi << 8) or *(esi + 1)) << 2

        SHL     eax, 2

@@4:

        add     edi, ecx // edi += ecx

        inc     ecx // ecx = last encode bytes

@LastLoop:

        mov     edx, eax // for (; cex > 0; ecx --, edi --)

        AND     edx, 63 // {

        mov     dl, [ebp + edx] // edx = eax & 63

        mov     [edi], dl // *edi = Base64_Chars[edx]

        SHR     eax, 6 // eax >>= 6

        dec     edi // }

        loop    @LastLoop

@end:

        pop     eax

        SHL     eax, 2 // return encode bytes

        pop     ebx

        pop     edi

        pop     esi

        pop     ebp

end;

function Base64Encode(const Source; SourceSize: Integer): Base64String;

begin

  SetLength(Result, Base64EncodeBufSize(SourceSize));

  Base64Encode(Source, SourceSize, Result[1]);

end;

procedure Base64Encode(Source, Dest: TStream; StartPos: Int64; Size: Int64);

begin

  Base64Stream(Source, Dest, Base64Encode, StartPos, Size, 6144, 8192);

end;

{$IFDEF UNICODE}

function StrToBase64(const Str: AnsiString): Base64String;

begin

  Result := Base64Encode(Str[1], Length(Str));

end;

function StrToBase64(const Str: string): Base64String;

begin

  Result := StrToBase64(AnsiString(Str));

end;

{$ELSE}

function StrToBase64(const Str: string): Base64String;

begin

  Result := Base64Encode(Str[1], Length(Str));

end;

{$ENDIF}

function Base64DecodeBufSize(const Base64Source; SourceSize: Integer): Integer;

asm

        mov     ecx, eax // ecx = Source + Size

        add     ecx, edx

        mov     eax, edx // eax = Size / 4 * 3

        SHR     edx, 2

        SHR     eax, 1

        add     eax, edx

        mov     edx, eax

        jz      @@2

@@1:

        dec     ecx

        cmp     byte ptr[ecx], 61

        jne     @@2 // if (*--ecx == '=')

        dec     eax // eax --

        jmp     @@1

@@2: // return eax: BufSize; edx: Size / 4 * 3

end;

function Base64Decode(const Base64Source; SourceSize: Integer; var Buf): Integer;

asm

        push    ebp

        push    esi

        push    edi

        push    ebx

        mov     esi, eax // esi = Source

        mov     edi, ecx // edi = Buf

        mov     ebx, edx

        call    Base64DecodeBufSize

        push    eax // eax = Base64DecodeBufSize(Source, SourceSize)

        sub     edx, eax // edx -= eax // edx: '=' count

        lea     ebp, Base64_Bytes

        SHR     ebx, 2 // ebx = SourceSize / 4

        test    ebx, ebx

        jz      @END

        push    edx

        cld

@DecodeLoop: // for (; ebx > 0; ebx --; edi += 3)

        mov     ecx, 4 // {

        XOR     eax, eax

@xchgLoop: // for (ecx = 4, eax = 0; ecx > 0; ecx --)

        movzx   edx, [esi] // {

        sub     edx, 43 // edx = *(int*)esi - 43

        SHL     eax, 6 // eax <<= 6

        OR      al, [ebp + edx]// al |= Base64_Bytes[edx]

        inc     esi // esi ++

        loop    @xchgLoop // }

        bswap   eax // bswap(eax)

        dec     ebx // if (ebx == 1) break

        jz      @Last

        SHR     eax, 8 // eax >>= 8

        stosw // *edi = ax; edi += 2

        SHR     eax, 16 // eax >>= 16

        stosb // *edi++ = al

        jmp     @DecodeLoop // }

@Last:

        pop     ecx

        XOR     ecx, 3 // ecx = last bytes

@LastLoop: // for (; ecx > 0; ecx --)

        SHR     eax, 8 // {

        stosb // eax >>= 8; *edi ++ = al

        loop    @LastLoop // }

@end:

        pop     eax // return eax

        pop     ebx

        pop     edi

        pop     esi

        pop     ebp

end;

procedure Base64Decode(Source, Dest: TStream; StartPos: Int64; Size: Int64);

begin

  Base64Stream(Source, Dest, Base64Decode, StartPos, Size, 8192, 6144);

end;

{$IFDEF UNICODE}

function Base64Decode(const Base64Source; SourceSize: Integer): string;

var

  s: AnsiString;

begin

  SetLength(s, Base64DecodeBufSize(Base64Source, SourceSize));

  Base64Decode(Base64Source, SourceSize, s[1]);

  Result := string(s);

end;

{$ELSE}

function Base64Decode(const Base64Source; SourceSize: Integer): string;

begin

  SetLength(Result, Base64DecodeBufSize(Base64Source, SourceSize));

  Base64Decode(Base64Source, SourceSize, Result[1]);

end;

{$ENDIF}

function Base64ToStr(const Base64Str: Base64String): string;

begin

  Result := Base64Decode(Base64Str[1], Length(Base64Str));

end;

end.

　　

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