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/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Universal charset detector code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 2001
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Shy Shalom <shooshX@gmail.com>
* Rudi Pettazzi <rudi.pettazzi@gmail.com> (C# port)
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
using System.IO;
namespace UniversalDetector.Core
{
public enum ProbingState {
Detecting = 0, // no sure answer yet, but caller can ask for confidence
FoundIt = 1, // positive answer
NotMe = 2 // negative answer
};
public abstract class CharsetProber
{
protected const float SHORTCUT_THRESHOLD = 0.95F;
protected ProbingState state;
// ASCII codes
private const byte SPACE = 0x20;
private const byte CAPITAL_A = 0x41;
private const byte CAPITAL_Z = 0x5A;
private const byte SMALL_A = 0x61;
private const byte SMALL_Z = 0x7A;
private const byte LESS_THAN = 0x3C;
private const byte GREATER_THAN = 0x3E;
/// <summary>
/// Feed data to the prober
/// </summary>
/// <param name="buf">a buffer</param>
/// <param name="offset">offset into buffer</param>
/// <param name="len">number of bytes available into buffer</param>
/// <returns>
/// A <see cref="ProbingState"/>
/// </returns>
public abstract ProbingState HandleData(byte[] buf, int offset, int len);
/// <summary>
/// Reset prober state
/// </summary>
public abstract void Reset();
public abstract string GetCharsetName();
public abstract float GetConfidence();
public virtual ProbingState GetState()
{
return state;
}
public virtual void SetOption()
{
}
public virtual void DumpStatus()
{
}
//
// Helper functions used in the Latin1 and Group probers
//
/// <summary>
///
/// </summary>
/// <returns>filtered buffer</returns>
protected static byte[] FilterWithoutEnglishLetters(byte[] buf, int offset, int len)
{
byte[] result = null;
using (MemoryStream ms = new MemoryStream(buf.Length)) {
bool meetMSB = false;
int max = offset + len;
int prev = offset;
int cur = offset;
while (cur < max) {
byte b = buf[cur];
if ((b & 0x80) != 0) {
meetMSB = true;
} else if (b < CAPITAL_A || (b > CAPITAL_Z && b < SMALL_A)
|| b > SMALL_Z) {
if (meetMSB && cur > prev) {
ms.Write(buf, prev, cur - prev);
ms.WriteByte(SPACE);
meetMSB = false;
}
prev = cur + 1;
}
cur++;
}
if (meetMSB && cur > prev)
ms.Write(buf, prev, cur - prev);
ms.SetLength(ms.Position);
result = ms.ToArray();
}
return result;
}
/// <summary>
/// Do filtering to reduce load to probers (Remove ASCII symbols,
/// collapse spaces). This filter applies to all scripts which contain
/// both English characters and upper ASCII characters.
/// </summary>
/// <returns>a filtered copy of the input buffer</returns>
protected static byte[] FilterWithEnglishLetters(byte[] buf, int offset, int len)
{
byte[] result = null;
using (MemoryStream ms = new MemoryStream(buf.Length)) {
bool inTag = false;
int max = offset + len;
int prev = offset;
int cur = offset;
while (cur < max) {
byte b = buf[cur];
if (b == GREATER_THAN)
inTag = false;
else if (b == LESS_THAN)
inTag = true;
// it's ascii, but it's not a letter
if ((b & 0x80) == 0 && (b < CAPITAL_A || b > SMALL_Z
|| (b > CAPITAL_Z && b < SMALL_A))) {
if (cur > prev && !inTag) {
ms.Write(buf, prev, cur - prev);
ms.WriteByte(SPACE);
}
prev = cur + 1;
}
cur++;
}
// If the current segment contains more than just a symbol
// and it is not inside a tag then keep it.
if (!inTag && cur > prev)
ms.Write(buf, prev, cur - prev);
ms.SetLength(ms.Position);
result = ms.ToArray();
}
return result;
}
}
}
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