/*
* Copyright (C) 2002 Matt Zyzik (www.FileScope.com)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
using System;
using System.Text;
namespace DCSharp.Text{
/// <summary>
/// Encodes and decodes 'Canonical' base32 format.
/// </summary>
public class Base32
{
static string base32Chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
private static int[] base32Lookup =
{
0xFF,0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F, // '0', '1', '2', '3', '4', '5', '6', '7'
0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, // '8', '9', ':', ';', '<', '=', '>', '?'
0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G'
0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O'
0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W'
0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF, // 'X', 'Y', 'Z', '[', '\', ']', '^', '_'
0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g'
0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o'
0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w'
0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF // 'x', 'y', 'z', '{', '|', '}', '~', 'DEL'
};
public static string Encode(byte[] bytes)
{
return Encode(bytes, 0, bytes.Length);
}
public static string Encode(byte[] bytes, int loc, int len)
{
int total = loc+len;
int index = 0, digit = 0;
int currByte, nextByte;
StringBuilder base32 = new StringBuilder((len+7)*8/5);
while(loc < total)
{
currByte = bytes[loc];
if(index > 3)
{
if((loc+1) < total)
nextByte = bytes[loc+1];
else
nextByte = 0;
digit = currByte & (0xFF >> index);
index = (index + 5) % 8;
digit <<= index;
digit |= nextByte >> (8 - index);
loc++;
}
else
{
digit = (currByte >> (8 - (index + 5))) & 0x1F;
index = (index + 5) % 8;
if(index == 0)
loc++;
}
base32.Append(base32Chars[digit]);
}
return base32.ToString();
}
public static byte[] Decode(string base32)
{
return Decode(base32, 0, base32.Length);
}
public static byte[] Decode(string base32, int loc, int len)
{
int total = loc+len;
int index, lookup, offset, digit;
byte[] bytes = new byte[len*5/8];
for(index = 0, offset = 0; loc < total; loc++)
{
lookup = base32[loc] - '0';
if(lookup < 0 || lookup >= base32Lookup.Length)
continue;
digit = base32Lookup[lookup];
if(digit == 0xFF)
continue;
if(index <= 3)
{
index = (index + 5) % 8;
if(index == 0)
{
bytes[offset] |= (byte)digit;
offset++;
if(offset >= bytes.Length)
break;
}
else
bytes[offset] |= (byte)(digit << (8 - index));
}
else
{
index = (index + 5) % 8;
bytes[offset] |= (byte)((uint)digit >> index);
offset++;
if(offset >= bytes.Length)
break;
bytes[offset] |= (byte)(digit << (8 - index));
}
}
return bytes;
}
}
}
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