Delphi版的Base64转换函数

Base64是网络上最常见的用于加密传输8Bit字节代码的编码方式之一，网上搜索，.NET、C/C++的代码到处都是，可没找到Delphi的，本人写了2个函数，可供访问者参考使用。（注：后来，我觉得这2个函数灵活性太差，进行了修改，见《Delphi版的Base64转换函数（修改版） 》）

unitBase64;

interface

usesSysUtils;

functionStrToBase64( const str: string ): string ;
functionBase64ToStr( const Base64: string ): string ;

implementation

// const
// Base64_Chars='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

functionStrToBase64( const Str: string ): string ;
var
I,J,K,Len,Len1:Integer;
B3:array[ 0 .. 2 ]ofByte;
B4:array[ 0 .. 3 ]ofByte;
begin
if Str = '' then
begin
Result: = '' ;
Exit;
end;
Len: = Length(Str);
Len1: = ((Len + 2 )div 3 )shl 2 ;
SetString(Result,nil,Len1);
I: = 1 ;
J: = 1 ;
while I <= Len do
begin
for K: = 0 to 2 do
if K + I > LenthenB3[K]: = 0
else B3[K]: = Ord(Str[K + I]);
B4[ 0 ]: = B3[ 0 ]shr 2 ;
B4[ 1 ]: = ((B3[ 0 ]shl 4 )or(B3[ 1 ]shr 4 ))and 63 ;
B4[ 2 ]: = ((B3[ 1 ]shl 2 )or(B3[ 2 ]shr 6 ))and 63 ;
B4[ 3 ]: = B3[ 2 ]and 63 ;
for K: = 0 to 3 do
begin
case B4[K]of
0 .. 25 :Result[J]: = Chr(B4[K] + 65 ); // 'A'..'Z'
26 .. 51 :Result[J]: = Chr(B4[K] + 71 ); // 'a'..'z'(B4[K]-26+97)
62 :Result[J]: = ' + ' ;
63 :Result[J]: = ' / ' ;
else Result[J]: = Chr(B4[K] - 4 ); // '0'..'9'(B4[K]-52+48)
end;
// Result[J]:=Base64_Chars[B4[K]+1];
Inc(J);
end;
Inc(I, 3 );
end;
K: = 3 - Lenmod 3 - 1 ;
if K <> 2 then
for I: = Len1 - KtoLen1 do
Result[I]: = ' = ' ;
end;

functionBase64ToStr( const Base64: string ): string ;
var
I,J,K,Len,Len1:Integer;
B4:array[ 0 .. 3 ]ofByte;
begin
if Base64 = '' then
begin
Result: = '' ;
Exit;
end;
Len: = Length(Base64);
if Lenand 3 <> 0 then
raiseException.Create( ' InvalidBase64length ' );
Len1: = (Lenshr 2 ) * 3 ;
SetString(Result,nil,Len1);
I: = 1 ;
J: = 1 ;
while I <= Len do
begin
for K: = 0 to 3 do
begin
case Base64[I]of
' A ' .. ' Z ' :B4[K]: = Ord(Base64[I]) - 65 ;
' a ' .. ' z ' :B4[K]: = Ord(Base64[I]) - 71 ;
' 0 ' .. ' 9 ' :B4[K]: = Ord(Base64[I]) + 4 ;
' + ' :B4[K]: = 62 ;
' / ' :B4[K]: = 63 ;
' = ' :B4[K]: = 0 ;
else raiseException.CreateFmt( ' #%d:InvalidcharinBase64 ' ,[Ord(Base64[I])]);
end;
Inc(I);
end;
Result[J]: = Chr((B4[ 0 ]shl 2 )or(B4[ 1 ]shr 4 ));
Result[J + 1 ]: = Chr((B4[ 1 ]shl 4 )or(B4[ 2 ]shr 2 ));
Result[J + 2 ]: = Chr((B4[ 2 ]shl 6 )orB4[ 3 ]);
Inc(J, 3 );
end;

I: = Pos( ' = ' ,Base64);
if I <> 0 then
begin
I: = Len - I + 1 ;
Delete(Result,Len1 - I + 1 ,I);
end;

end;

end.

使用indy9的MD5类测试，测试如下：

unitmain;

interface

uses
Windows,Messages,SysUtils,Variants,Classes,Graphics,Controls,Forms,
Dialogs,StdCtrls;

type
TForm1 = class (TForm)
Button1:TButton;
procedureButton1Click(Sender:TObject);
private
... {Privatedeclarations}
public
... {Publicdeclarations}
end;

var
Form1:TForm1;

implementation

usesBase64,IdHash,IdHashMessageDigest;

... {$R*.dfm}

procedureTForm1.Button1Click(Sender:TObject);
var
md5:TIdHashMessageDigest5;
Value:T4x4LongWordRecord;
s,s1: string ;
begin
md5: = TIdHashMessageDigest5.Create;
try
Value: = md5.HashValue( ' Maozefa ' ); // 得到MD5值
SetLength(s1, 16); // 设置s1长度为16
Move(Value, s1[1], 16); // 将Value拷贝到s1中
s := StrToBase64(s1); // 得到MD5值的Base64
s1: = md5.AsHex(value); // 转换为十六进制字串
ShowMessage( ' Base64: ' + s + # 10 + ' Hex: ' + s1); // 显示结果
s: = Base64ToStr(s); // 还原为MD5原值字串
Move(s[ 1 ],Value, 16 ); // 转换为MD5原值
s1: = md5.AsHex(value); // MD5原值转换为十六进制字串
// 显示还原结果,因s为原始MD5值，所以显示为乱码，但是16进制码与转换前是相同的
ShowMessage( ' string: ' + s + # 10 + ' Hex: ' + s1);
finally
md5.Free;
end;
end;

end.

测试结果：

Base64: dPV9boIqSOmu861RyPB+WQ==
Hex: 74F57D6E822A48E9AEF3AD51C8F07E59

string: t鮹n?H楫蟓Q瑞~Y
Hex: 74F57D6E822A48E9AEF3AD51C8F07E59