Base64.pas


base64.pas
unit Base64;

interface

uses SysUtils;

function StrToBase64(const str: string): string;
function Base64ToStr(const Base64: string): string;

implementation

//const

// Base64_Chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';

function StrToBase64(const Str: string): string;
var

I, J, K, Len, Len1: Integer;

B3: array[0..2] of Byte;

B4: array[0..3] of Byte;

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 > Len then B3[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 - Len mod 3 - 1;

if K <> 2 then

for I := Len1 - K to Len1 do

Result[I] := '=';

end;



function Base64ToStr(const Base64: string): string;

var

I, J, K, Len, Len1: Integer;

B4: array[0..3] of Byte;

begin

if Base64 = '' then

begin

Result := '';

Exit;

end;

Len := Length(Base64);

if Len and 3 <> 0 then

raise Exception.Create('Invalid Base64 length');

Len1 := (Len shr 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 raise Exception.CreateFmt('#%d: Invalid char in Base64', [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) or B4[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.


联系电话:
020-00000000
联系电话:
020-00000000
联系电话:
020-12345678