本文整理自网络，侵删。
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.
相关阅读 >>
更多相关阅读请进入《Delphi》频道 >>
