#region PDFsharp - A .NET library for processing PDF

//

// Authors:

// Stefan Lange

//

// Copyright (c) 2005-2016 empira Software GmbH, Cologne Area (Germany)

//

// http://www.PdfSharpCore.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;

namespace PdfSharpCore.Pdf.Filters

{

/// <summary>

/// Implements the ASCIIHexDecode filter.

/// </summary>

public class AsciiHexDecode : Filter

{

// Reference: 3.3.1 ASCIIHexDecode Filter / Page 69

/// <summary>

/// Encodes the specified data.

/// </summary>

public override byte[] Encode(byte[] data)

{

if (data == null)

throw new ArgumentNullException("data");

int count = data.Length;

byte[] bytes = new byte[2 * count];

for (int i = 0, j = 0; i < count; i++)

{

byte b = data[i];

bytes[j++] = (byte)((b >> 4) + ((b >> 4) < 10 ? (byte)'0' : (byte)('A' - 10)));

bytes[j++] = (byte)((b & 0xF) + ((b & 0xF) < 10 ? (byte)'0' : (byte)('A' - 10)));

}

return bytes;

}

/// <summary>

/// Decodes the specified data.

/// </summary>

public override byte[] Decode(byte[] data, FilterParms parms)

{

if (data == null)

throw new ArgumentNullException("data");

data = RemoveWhiteSpace(data);

int count = data.Length;

// Ignore EOD (end of data) character.

// EOD can be anywhere in the stream, but makes sense only at the end of the stream.

if (count > 0 && data[count - 1] == '>')

--count;

if (count % 2 == 1)

{

count++;

byte[] temp = data;

data = new byte[count];

temp.CopyTo(data, 0);

}

count >>= 1;

byte[] bytes = new byte[count];

for (int i = 0, j = 0; i < count; i++)

{

// Must support 0-9, A-F, a-f - "Any other characters cause an error."

byte hi = data[j++];

byte lo = data[j++];

if (hi >= 'a' && hi <= 'f')

hi -= 32;

if (lo >= 'a' && lo <= 'f')

lo -= 32;

// TODO Throw on invalid characters. Stop when encountering EOD. Add one more byte if EOD is the lo byte.

bytes[i] = (byte)((hi > '9' ? hi - '7'/*'A' + 10*/: hi - '0') * 16 + (lo > '9' ? lo - '7'/*'A' + 10*/: lo - '0'));

}

return bytes;

}

}

}