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Base64编码/解码Delphi源码

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Unit CnBase64;

Interface

Uses
SysUtils, Windows;

Function Base64Encode(InputData: String; Var OutputData: String): byte;
{* 对数据进行BASE64编码,如编码成功返回Base64_OK
|


InputData:string – 要编码的数据
var OutputData: string – 编码后的数据
|
}

Function Base64Decode(InputData: String; Var OutputData: String): byte;
{* 对数据进行BASE64解码,如解码成功返回Base64_OK
|

InputData:string – 要解码的数据
var OutputData: string – 解码后的数据
|
}

Const
BASE64_OK = 0; // 转换成功
BASE64_ERROR = 1;
// 转换错误(未知错误) (e.g. can’t encode octet in input stream) -> error in implementation
BASE64_INVALID = 2;
// 输入的字符串中有非法字符 (在 FilterDecodeInput=False 时可能出现)
BASE64_LENGTH = 3; // 数据长度非法
BASE64_DATALEFT = 4;
// too much input data left (receveived ‘end of encoded data’ but not end of input string)
BASE64_PADDING = 5; // 输入的数据未能以正确的填充字符结束

Implementation

Var
FilterDecodeInput: Boolean = true;
Const
Base64TableLength = 64;
Base64Table : String[Base64TableLength] =
‘ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+*’;
Pad = ‘=’;

Function Base64Encode(InputData: String; Var OutputData: String): byte;
Var
i : integer;
CurrentB, PrevB : byte;
c : byte;
s : char;
InputLength : integer;

Function ValueToCharacter(value: byte; Var character: char): Boolean;
//******************************************************************
// 将一个在0..Base64TableLength-1区间内的值,转换为与Base64编码相对应
// 的字符来表示,如果转换成功则返回True
//******************************************************************
Begin
result := true;
If (value > Base64TableLength – 1) Then
result := false
Else
character := Base64Table[value + 1];
End;

Begin
OutputData := ”;
InputLength := Length(InputData);
i := 1;
If (InputLength = 0) Then Begin
result := BASE64_OK;
Exit;
End;

Repeat
// 第一次转换
CurrentB := Ord(InputData[i]);
i := i + 1;
InputLength := InputLength – 1;
c := (CurrentB Shr 2);
If Not ValueToCharacter(c, s) Then Begin
result := BASE64_ERROR;
Exit;
End;
OutputData := OutputData + s;
PrevB := CurrentB;

// 第二次转换
If InputLength = 0 Then
CurrentB := 0
Else Begin
CurrentB := Ord(InputData[i]);
i := i + 1;
End;
InputLength := InputLength – 1;
c := (PrevB And $03) Shl 4 + (CurrentB Shr 4);
//取出XX后4位并将其左移4位与XX右移4位合并成六位
If Not ValueToCharacter(c, s) Then
{//检测取得的字符是否在Base64Table内} Begin
result := BASE64_ERROR;
Exit;
End;
OutputData := OutputData + s;
PrevB := CurrentB;

// 第三次转换
If InputLength < 0 Then s := Pad Else Begin If InputLength = 0 Then CurrentB := 0 Else Begin CurrentB := Ord(InputData[i]); i := i + 1; End; InputLength := InputLength - 1; c := (PrevB And $0F) Shl 2 + (CurrentB Shr 6); //取出XX后4位并将其左移2位与XX右移6位合并成六位 If Not ValueToCharacter(c, s) Then {//检测取得的字符是否在Base64Table内} Begin result := BASE64_ERROR; Exit; End; End; OutputData := OutputData + s;
// 第四次转换
If InputLength < 0 Then s := Pad Else Begin c := (CurrentB And $3F); //取出XX后6位 If Not ValueToCharacter(c, s) Then {//检测取得的字符是否在Base64Table内} Begin result := BASE64_ERROR; Exit; End; End; OutputData := OutputData + s; Until InputLength <= 0; result := BASE64_OK; End;
Function Base64Decode(InputData: String; Var OutputData: String): byte;
Var
i : integer;
InputLength : integer;
CurrentB, PrevB : byte;
c : byte;
s : char;

Function CharacterToValue(character: char; Var value: byte): Boolean;
//******************************************************************
// 转换字符为一在0..Base64TableLength-1区间中的值,如果转换成功则返
// 回True(即字符在Base64Table中)
//******************************************************************
Begin
result := true;
value := Pos(character, Base64Table);
If value = 0 Then
result := false
Else
value := value – 1;
End;

Function FilterLine(InputData: String): String;
//******************************************************************
// 过滤所有不在Base64Table中的字符,返回值为过滤后的字符
//******************************************************************
Var
F : byte;
i : integer;
Begin
result := ”;
For i := 1 To Length(InputData) Do
If CharacterToValue(InputData[i], F) Or (InputData[i] = Pad) Then
result := result + InputData[i];
End;

Begin
If (InputData = ”) Then Begin
result := BASE64_OK;
Exit;
End;
OutputData := ”;

If FilterDecodeInput Then
InputData := FilterLine(InputData);

InputLength := Length(InputData);
If InputLength Mod 4 <> 0 Then Begin
result := BASE64_LENGTH;
Exit;
End;

i := 0;
Repeat
// 第一次转换
i := i + 1;
s := InputData[i];
If Not CharacterToValue(s, CurrentB) Then Begin
result := BASE64_INVALID;
Exit;
End;
i := i + 1;
s := InputData[i];
If Not CharacterToValue(s, PrevB) Then Begin
result := BASE64_INVALID;
Exit;
End;

c := (CurrentB Shl 2) + (PrevB Shr 4);
OutputData := OutputData + Chr(c);

// 第二次转换
i := i + 1;
s := InputData[i];
If s = Pad Then Begin
If (i <> InputLength – 1) Then Begin
result := BASE64_DATALEFT;
Exit;
End
Else
If InputData[i + 1] <> Pad Then Begin
result := BASE64_PADDING;
Exit;
End;
End
Else Begin
If Not CharacterToValue(s, CurrentB) Then Begin
result := BASE64_INVALID;
Exit;
End;
c := (PrevB Shl 4) + (CurrentB Shr 2);
OutputData := OutputData + Chr(c);
End;

// 第三次转换
i := i + 1;
s := InputData[i];
If s = Pad Then Begin
If (i <> InputLength) Then Begin
result := BASE64_DATALEFT;
Exit;
End;
End
Else Begin
If Not CharacterToValue(s, PrevB) Then Begin
result := BASE64_INVALID;
Exit;
End;
c := (CurrentB Shl 6) + (PrevB);
OutputData := OutputData + Chr(c);
End;

Until (i >= InputLength);
result := BASE64_OK;
End;

End.
=======================================================================================
Uses CnBase64;
CnBase64.Base64Encode(Edit1.Text, Psw64);

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