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(conststr:string):string;
functionBase64ToStr(constBase64:string):string;

implementation

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

functionStrToBase64(constStr:string):string;
var
I,J,K,Len,Len1:Integer;
B3:array[0..2]ofByte;
B4:array[0..3]ofByte;
begin
ifStr=''then
begin
Result:='';
Exit;
end;
Len:=Length(Str);
Len1:=((Len+2)div3)shl2;
SetString(Result,nil,Len1);
I:=1;
J:=1;
whileI<=Lendo
begin
forK:=0to2do
ifK+I>LenthenB3[K]:=0
elseB3[K]:=Ord(Str[K+I]);
B4[0]:=B3[0]shr2;
B4[1]:=((B3[0]shl4)or(B3[1]shr4))and63;
B4[2]:=((B3[1]shl2)or(B3[2]shr6))and63;
B4[3]:=B3[2]and63;
forK:=0to3do
begin
caseB4[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]:='/';
elseResult[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-Lenmod3-1;
ifK<>2then
forI:=Len1-KtoLen1do
Result[I]:='=';
end;

functionBase64ToStr(constBase64:string):string;
var
I,J,K,Len,Len1:Integer;
B4:array[0..3]ofByte;
begin
ifBase64=''then
begin
Result:='';
Exit;
end;
Len:=Length(Base64);
ifLenand3<>0then
raiseException.Create('InvalidBase64length');
Len1:=(Lenshr2)*3;
SetString(Result,nil,Len1);
I:=1;
J:=1;
whileI<=Lendo
begin
forK:=0to3do
begin
caseBase64[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;
elseraiseException.CreateFmt('#%d:InvalidcharinBase64',[Ord(Base64[I])]);
end;
Inc(I);
end;
Result[J]:=Chr((B4[0]shl2)or(B4[1]shr4));
Result[J+1]:=Chr((B4[1]shl4)or(B4[2]shr2));
Result[J+2]:=Chr((B4[2]shl6)orB4[3]);
Inc(J,3);
end;

I:=Pos('=',Base64);
ifI<>0then
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