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4c8316f9cf
There is no "exception" in encoding. The non-breaking space 0xA0 is not ASCII, and therefore returning "ASCII" will later create issues (for instance trying to re-encode with iconv produces an error). This was obviously an explicit decision in original code (according to code comments), probably tied to specifity of the original program from Mozilla. Now we want strict detection. I will return "ISO-8859-1" for "nearly-ASCII texts with NBSP as only exception" (note that I could have returned any ISO-8859 charsets since they all have this character in common).
337 lines
9.1 KiB
C++
337 lines
9.1 KiB
C++
/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla Universal charset detector code.
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*
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* The Initial Developer of the Original Code is
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* Netscape Communications Corporation.
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* Portions created by the Initial Developer are Copyright (C) 2001
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* the Initial Developer. All Rights Reserved.
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*
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* Contributor(s):
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* Shy Shalom <shooshX@gmail.com>
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#include "nscore.h"
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#include "nsUniversalDetector.h"
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#include "nsMBCSGroupProber.h"
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#include "nsSBCSGroupProber.h"
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#include "nsEscCharsetProber.h"
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#include "nsLatin1Prober.h"
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nsUniversalDetector::nsUniversalDetector(PRUint32 aLanguageFilter)
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{
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mNbspFound = PR_FALSE;
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mDone = PR_FALSE;
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mBestGuess = -1; //illegal value as signal
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mInTag = PR_FALSE;
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mEscCharSetProber = nsnull;
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mStart = PR_TRUE;
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mDetectedCharset = nsnull;
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mGotData = PR_FALSE;
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mInputState = ePureAscii;
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mLastChar = '\0';
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mLanguageFilter = aLanguageFilter;
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PRUint32 i;
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for (i = 0; i < NUM_OF_CHARSET_PROBERS; i++)
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mCharSetProbers[i] = nsnull;
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}
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nsUniversalDetector::~nsUniversalDetector()
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{
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for (PRInt32 i = 0; i < NUM_OF_CHARSET_PROBERS; i++)
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delete mCharSetProbers[i];
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delete mEscCharSetProber;
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}
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void
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nsUniversalDetector::Reset()
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{
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mNbspFound = PR_FALSE;
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mDone = PR_FALSE;
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mBestGuess = -1; //illegal value as signal
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mInTag = PR_FALSE;
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mStart = PR_TRUE;
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mDetectedCharset = nsnull;
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mGotData = PR_FALSE;
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mInputState = ePureAscii;
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mLastChar = '\0';
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if (mEscCharSetProber)
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mEscCharSetProber->Reset();
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PRUint32 i;
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for (i = 0; i < NUM_OF_CHARSET_PROBERS; i++)
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if (mCharSetProbers[i])
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mCharSetProbers[i]->Reset();
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}
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//---------------------------------------------------------------------
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#define SHORTCUT_THRESHOLD (float)0.95
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#define MINIMUM_THRESHOLD (float)0.20
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nsresult nsUniversalDetector::HandleData(const char* aBuf, PRUint32 aLen)
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{
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if(mDone)
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return NS_OK;
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if (aLen > 0)
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mGotData = PR_TRUE;
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/* If the data starts with BOM, we know it is UTF. */
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if (mStart)
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{
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mStart = PR_FALSE;
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if (aLen > 2)
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switch (aBuf[0])
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{
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case '\xEF':
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if (('\xBB' == aBuf[1]) && ('\xBF' == aBuf[2]))
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/* EF BB BF: UTF-8 encoded BOM. */
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mDetectedCharset = "UTF-8";
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break;
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case '\xFE':
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if ('\xFF' == aBuf[1])
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/* FE FF: UTF-16, big endian BOM. */
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mDetectedCharset = "UTF-16";
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break;
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case '\xFF':
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if ('\xFE' == aBuf[1])
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{
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if (aLen > 3 &&
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aBuf[2] == '\x00' &&
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aBuf[3] == '\x00')
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{
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/* FF FE 00 00: UTF-32 (LE). */
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mDetectedCharset = "UTF-32";
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}
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else
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{
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/* FF FE: UTF-16, little endian BOM. */
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mDetectedCharset = "UTF-16";
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}
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}
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break;
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case '\x00':
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if (aLen > 3 &&
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aBuf[1] == '\x00' &&
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aBuf[2] == '\xFE' &&
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aBuf[3] == '\xFF')
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{
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/* 00 00 FE FF: UTF-32 (BE). */
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mDetectedCharset = "UTF-32";
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}
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break;
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}
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if (mDetectedCharset)
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{
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mDone = PR_TRUE;
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return NS_OK;
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}
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}
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PRUint32 i;
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for (i = 0; i < aLen; i++)
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{
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/* If every other character is ASCII or 0xA0, we don't run charset
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* probers.
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* 0xA0 (NBSP in a few charset) is apparently a rare exception
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* of non-ASCII character often contained in nearly-ASCII text. */
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if (aBuf[i] & '\x80' && aBuf[i] != '\xA0')
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{
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/* We got a non-ASCII byte (high-byte) */
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if (mInputState != eHighbyte)
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{
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//adjust state
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mInputState = eHighbyte;
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//kill mEscCharSetProber if it is active
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if (mEscCharSetProber) {
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delete mEscCharSetProber;
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mEscCharSetProber = nsnull;
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}
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//start multibyte and singlebyte charset prober
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if (nsnull == mCharSetProbers[0])
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{
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mCharSetProbers[0] = new nsMBCSGroupProber(mLanguageFilter);
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if (nsnull == mCharSetProbers[0])
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return NS_ERROR_OUT_OF_MEMORY;
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}
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if (nsnull == mCharSetProbers[1] &&
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(mLanguageFilter & NS_FILTER_NON_CJK))
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{
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mCharSetProbers[1] = new nsSBCSGroupProber;
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if (nsnull == mCharSetProbers[1])
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return NS_ERROR_OUT_OF_MEMORY;
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}
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if (nsnull == mCharSetProbers[2])
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{
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mCharSetProbers[2] = new nsLatin1Prober;
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if (nsnull == mCharSetProbers[2])
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return NS_ERROR_OUT_OF_MEMORY;
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}
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}
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}
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else
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{
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/* Just pure ASCII or NBSP so far. */
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if (aBuf[i] == '\xA0')
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{
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/* ASCII with the only exception of NBSP seems quite common.
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* I doubt it is really necessary to train a model here, so let's
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* just make an exception.
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*/
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mNbspFound = PR_TRUE;
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}
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else if (mInputState == ePureAscii &&
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(aBuf[i] == '\033' || (aBuf[i] == '{' && mLastChar == '~')))
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{
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/* We found an escape character or HZ "~{". */
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mInputState = eEscAscii;
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}
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mLastChar = aBuf[i];
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}
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}
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nsProbingState st;
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switch (mInputState)
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{
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case eEscAscii:
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if (nsnull == mEscCharSetProber) {
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mEscCharSetProber = new nsEscCharSetProber(mLanguageFilter);
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if (nsnull == mEscCharSetProber)
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return NS_ERROR_OUT_OF_MEMORY;
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}
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st = mEscCharSetProber->HandleData(aBuf, aLen);
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if (st == eFoundIt)
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{
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mDone = PR_TRUE;
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mDetectedCharset = mEscCharSetProber->GetCharSetName();
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}
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else if (mNbspFound)
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{
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mDetectedCharset = "ISO-8859-1";
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}
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else
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{
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/* ASCII with the ESC character (or the sequence "~{") is still
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* ASCII until proven otherwise. */
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mDetectedCharset = "ASCII";
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}
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break;
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case eHighbyte:
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for (i = 0; i < NUM_OF_CHARSET_PROBERS; i++)
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{
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if (mCharSetProbers[i])
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{
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st = mCharSetProbers[i]->HandleData(aBuf, aLen);
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if (st == eFoundIt)
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{
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mDone = PR_TRUE;
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mDetectedCharset = mCharSetProbers[i]->GetCharSetName();
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return NS_OK;
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}
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}
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}
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break;
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default:
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if (mNbspFound)
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{
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/* ISO-8859-1 is a good result candidate for ASCII + NBSP.
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* (though it could have been any ISO-8859 encoding). */
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mDetectedCharset = "ISO-8859-1";
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}
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else
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{
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/* Pure ASCII */
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mDetectedCharset = "ASCII";
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}
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break;
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}
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return NS_OK;
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}
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//---------------------------------------------------------------------
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void nsUniversalDetector::DataEnd()
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{
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if (!mGotData)
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{
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// we haven't got any data yet, return immediately
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// caller program sometimes call DataEnd before anything has been sent to detector
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return;
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}
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if (mDetectedCharset)
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{
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mDone = PR_TRUE;
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Report(mDetectedCharset);
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return;
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}
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switch (mInputState)
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{
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case eHighbyte:
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{
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float proberConfidence;
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float maxProberConfidence = (float)0.0;
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PRInt32 maxProber = 0;
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for (PRInt32 i = 0; i < NUM_OF_CHARSET_PROBERS; i++)
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{
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if (mCharSetProbers[i])
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{
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proberConfidence = mCharSetProbers[i]->GetConfidence();
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if (proberConfidence > maxProberConfidence)
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{
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maxProberConfidence = proberConfidence;
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maxProber = i;
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}
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}
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}
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//do not report anything because we are not confident of it, that's in fact a negative answer
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if (maxProberConfidence > MINIMUM_THRESHOLD)
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Report(mCharSetProbers[maxProber]->GetCharSetName());
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}
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break;
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case eEscAscii:
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break;
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default:
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;
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}
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return;
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}
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