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#region PDFsharp - A .NET library for processing PDF
//
// Authors:
// Stefan Lange (mailto:Stefan.Lange@pdfsharp.com)
//
// Copyright (c) 2005-2008 empira Software GmbH, Cologne (Germany)
//
// http://www.pdfsharp.com
// http://sourceforge.net/projects/pdfsharp
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
// THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
#endregion
using System;
using System.Diagnostics;
using System.Text;
using PdfSharp.Internal;
using PdfSharp.Pdf.Internal;
namespace PdfSharp.Pdf.Filters
{
/// <summary>
/// Implements the ASCII85Decode filter.
/// </summary>
public class ASCII85Decode : Filter
{
/// <summary>
/// Encodes the specified data.
/// </summary>
public override byte[] Encode(byte[] data)
{
if (data == null)
throw new ArgumentNullException("data");
int length = data.Length; // length == 0 is must not be treated as a special case
int words = length / 4;
int rest = length - (words * 4);
byte[] result = new byte[words * 5 + (rest == 0 ? 0 : rest + 1) + 2];
int idxIn = 0, idxOut = 0;
int wCount = 0;
while (wCount < words)
{
uint val = ((uint)data[idxIn++] << 24) + ((uint)data[idxIn++] << 16) + ((uint)data[idxIn++] << 8) + data[idxIn++];
if (val == 0)
{
result[idxOut++] = (byte)'z';
}
else
{
byte c5 = (byte)(val % 85 + '!');
val /= 85;
byte c4 = (byte)(val % 85 + '!');
val /= 85;
byte c3 = (byte)(val % 85 + '!');
val /= 85;
byte c2 = (byte)(val % 85 + '!');
val /= 85;
byte c1 = (byte)(val + '!');
result[idxOut++] = c1;
result[idxOut++] = c2;
result[idxOut++] = c3;
result[idxOut++] = c4;
result[idxOut++] = c5;
}
wCount++;
}
if (rest == 1)
{
uint val = (uint)data[idxIn++] << 24;
val /= 85 * 85 * 85;
byte c2 = (byte)(val % 85 + '!');
val /= 85;
byte c1 = (byte)(val + '!');
result[idxOut++] = c1;
result[idxOut++] = c2;
}
else if (rest == 2)
{
uint val = ((uint)data[idxIn++] << 24) + ((uint)data[idxIn++] << 16);
val /= 85 * 85;
byte c3 = (byte)(val % 85 + '!');
val /= 85;
byte c2 = (byte)(val % 85 + '!');
val /= 85;
byte c1 = (byte)(val + '!');
result[idxOut++] = c1;
result[idxOut++] = c2;
result[idxOut++] = c3;
}
else if (rest == 3)
{
uint val = ((uint)data[idxIn++] << 24) + ((uint)data[idxIn++] << 16) + ((uint)data[idxIn++] << 8);
val /= 85;
byte c4 = (byte)(val % 85 + '!');
val /= 85;
byte c3 = (byte)(val % 85 + '!');
val /= 85;
byte c2 = (byte)(val % 85 + '!');
val /= 85;
byte c1 = (byte)(val + '!');
result[idxOut++] = c1;
result[idxOut++] = c2;
result[idxOut++] = c3;
result[idxOut++] = c4;
}
result[idxOut++] = (byte)'~';
result[idxOut++] = (byte)'>';
if (idxOut < result.Length)
Array.Resize<byte>(ref result, idxOut);
return result;
}
/// <summary>
/// Decodes the specified data.
/// </summary>
public override byte[] Decode(byte[] data, FilterParms parms)
{
if (data == null)
throw new ArgumentNullException("data");
int idx;
int length = data.Length;
int zCount = 0;
int idxOut = 0;
for (idx = 0; idx < length; idx++)
{
char ch = (char)data[idx];
if (ch >= '!' && ch <= 'u')
data[idxOut++] = (byte)ch;
else if (ch == 'z')
{
data[idxOut++] = (byte)ch;
zCount++;
}
else if (ch == '~')
{
if ((char)data[idx + 1] != '>')
throw new ArgumentException("Illegal character.", "data");
break;
}
else
{
// ingnore unknown character
}
}
// Loop not ended with break?
if (idx == length)
throw new ArgumentException("Illegal character.", "date");
length = idxOut;
int nonZero = length - zCount;
int byteCount = 4 * (zCount + (nonZero / 5)); // full 4 byte blocks
int remainder = nonZero % 5;
if (remainder == 1)
throw new InvalidOperationException("Illegal character.");
if (remainder != 0)
byteCount += remainder - 1;
byte[] output = new byte[byteCount];
idxOut = 0;
idx = 0;
while (idx + 4 < length)
{
char ch = (char)data[idx];
if (ch == 'z')
{
idx++;
idxOut += 4;
}
else
{
uint val =
(uint)(data[idx++] - '!') * (85 * 85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85) +
(uint)(data[idx++] - '!') * 85 +
(uint)(data[idx++] - '!');
output[idxOut++] = (byte)(val >> 24);
output[idxOut++] = (byte)(val >> 16);
output[idxOut++] = (byte)(val >> 8);
output[idxOut++] = (byte)val;
}
}
// I've found no appropriate algorithm, so I write my own. In some rare cases the value must not
// increased by one, but I cannot found a general formula or a proof.
// All possible cases are tested programmatically.
if (remainder == 2) // one byte
{
int idxIn = idx;
uint value =
(uint)(data[idx++] - '!') * (85 * 85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85 * 85);
// Always increase if not zero (tried out)
if (value != 0)
value += 0x01000000;
output[idxOut++] = (byte)(value >> 24);
}
else if (remainder == 3) // two bytes
{
int idxIn = idx;
uint val;
uint value =
(uint)(data[idx++] - '!') * (85 * 85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85);
if (value != 0)
{
value &= 0xFFFF0000;
val = value / (85 * 85);
byte c3 = (byte)(val % 85 + '!');
val /= 85;
byte c2 = (byte)(val % 85 + '!');
val /= 85;
byte c1 = (byte)(val + '!');
if (c1 != data[idxIn] || c2 != data[idxIn + 1] || c3 != data[idxIn + 2])
{
value += 0x00010000;
//Count2++;
}
}
output[idxOut++] = (byte)(value >> 24);
output[idxOut++] = (byte)(value >> 16);
}
else if (remainder == 4) // three bytes
{
int idxIn = idx;
uint val;
uint value =
(uint)(data[idx++] - '!') * (85 * 85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85 * 85) +
(uint)(data[idx++] - '!') * (85 * 85) +
(uint)(data[idx++] - '!') * 85;
if (value != 0)
{
value &= 0xFFFFFF00;
val = value / 85;
byte c4 = (byte)(val % 85 + '!');
val /= 85;
byte c3 = (byte)(val % 85 + '!');
val /= 85;
byte c2 = (byte)(val % 85 + '!');
val /= 85;
byte c1 = (byte)(val + '!');
if (c1 != data[idxIn] || c2 != data[idxIn + 1] || c3 != data[idxIn + 2] || c4 != data[idxIn + 3])
{
value += 0x00000100;
//Count3++;
}
}
output[idxOut++] = (byte)(value >> 24);
output[idxOut++] = (byte)(value >> 16);
output[idxOut++] = (byte)(value >> 8);
}
return output;
}
//public static int Count1;
//public static int Count2;
//public static int Count3;
}
}
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