Delphi版的Base64转换函数(修改版)


前几天,兴趣所致,写了2个Delphi版的Base64转换函数,见《Delphi版的Base64转换函数》一文。后来觉得这些函数使用不够灵活,所以重新写了几个放在这里,核心的转换代码用BASM写的(不知是否快一点,不过,我觉得用汇编写这种代码好像比Pascal还容易些,因为有些二进制操作,高级语言不方便,同时使用汇编也能使算法更合理,可比较《Delphi版的Base64转换函数》代码和汇编码的注释伪代码),如果有错误和建议,请指正,本人不甚感激!


unit Base64;

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.


// 文件流的Base64测试
procedure TForm1.Button3Click(Sender: TObject);
var
Source, Dest: TStream;
md5: TMessageDigest5;
Value: THashValue128;
s1, s2: string;
begin
if OpenDialog1.Execute then
begin
md5 := TMessageDigest5.Create;
try
Source := TFileStream.Create(OpenDialog1.FileName, fmOpenRead); // 打开源文件
Value := md5.HashValue(Source); // 取得源文件Hash
s1 := md5.AsHex(Value);
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('Base64DecodeTest.txt', fmCreate); // 还原源文件内容
try
Base64Decode(Source, Dest);
Dest.Position := 0;
Value := md5.HashValue(Dest); // 取得还原文件Hash
s2 := md5.AsHex(Value);
finally
Source.Free;
Dest.Free;
end;
finally
md5.Free;
end;
// 显示源文件和还原文件的Hash十六进制字串,如果相等,证明编码和解码过程正确
ShowMessage(s1 + #10 + s2);
end;
end;

另有一点需要说明:有不少Delphi新手对本文编码(解码)过程的无类型参数感到困惑,不知该传递什么类型。其实,Delph中有不少这类无类型参数,如常用的Move过程,只要把它当着一个Byte类型的数组看待就行了,当使用string类型作实参传递给无类型形参时,要把s[1]作为参数传递(string类型下标是从1开始的),或者用指针转换,如PChar(s)^。如果是Delphi2009及以上版本,string类型作实参传递给无类型形参时,要注意不能简单的将Length(s)传递给SourceSize,而应该是Length(s) * Sizeof(char),因为Length(s)是字符串的长度,而不是实际缓冲区的长度,Delphi2009及以上版本中默认的string是WideString,char也等于WideChar,每个char占2字节。当然用string类型传递给无类型参数计算的是Unicode字符串的Base64编码,只有用AnsiString类型传递给无类型参数,或者使用StrToBase64过程(会自动转换string为AnsiString),才可能是你需要的Base64编码.


本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/maozefa/archive/2007/06/14/1653020.aspx


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