qtextcodec.cpp

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/****************************************************************************
** $Id: qt/src/tools/qtextcodec.cpp   2.2.3   edited 2000-12-07 $
**
** Implementation of QTextCodec class
**
** Created : 981015
**
** Copyright (C)1998-2000 Trolltech AS.  All rights reserved.
**
** This file is part of the tools module of the Qt GUI Toolkit.
**
** This file may be distributed under the terms of the Q Public License
** as defined by Trolltech AS of Norway and appearing in the file
** LICENSE.QPL included in the packaging of this file.
**
** This file may be distributed and/or modified under the terms of the
** GNU General Public License version 2 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.
**
** Licensees holding valid Qt Enterprise Edition or Qt Professional Edition
** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
**
** This file is provided AS IS with NO WARRANTY OF ANY KIND, INCLUDING THE
** WARRANTY OF DESIGN, MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
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**********************************************************************/

#include "qtextcodec.h"
#ifndef QT_NO_TEXTCODEC

#include "qlist.h"
#ifndef QT_NO_CODECS
#include "qutfcodec.h"
#include "qgbkcodec.h"
#include "qeucjpcodec.h"
#include "qjiscodec.h"
#include "qsjiscodec.h"
#include "qeuckrcodec.h"
#include "qbig5codec.h"
#include "qrtlcodec.h"
#include "qtsciicodec.h"
#endif

#include "qfile.h"
#include "qstrlist.h"
#include "qstring.h"

#include <stdlib.h>
#include <ctype.h>
#include <locale.h>


static QList<QTextCodec> * all = 0;
static bool destroying_is_ok; // starts out as 0

/*!  Deletes all the created codecs.

  \warning Do not call this function.

  QApplication calls this just before exiting, to delete any
  QTextCodec objects that may be lying around.  Since various other
  classes hold pointers to QTextCodec objects, it is not safe to call
  this function earlier.

  If you are using the utility classes (like QString) but not using
  QApplication, calling this function at the very end of your
  application can be helpful to chasing down memory leaks, as
  QTextCodec objects will not show up.
*/

void QTextCodec::deleteAllCodecs()
{
    if ( !all )
        return;

    destroying_is_ok = TRUE;
    QList<QTextCodec> * ball = all;
    all = 0;
    ball->clear();
    delete ball;
    destroying_is_ok = FALSE;
}


static void setupBuiltinCodecs();


static void realSetup()
{
#if defined(CHECK_STATE)
    if ( destroying_is_ok )
        qWarning( "creating new codec during codec cleanup" );
#endif
    all = new QList<QTextCodec>;
    all->setAutoDelete( TRUE );
    setupBuiltinCodecs();
}


static inline void setup()
{
    if ( !all )
        realSetup();
}


class QTextStatelessEncoder: public QTextEncoder {
    const QTextCodec* codec;
public:
    QTextStatelessEncoder(const QTextCodec*);
    QCString fromUnicode(const QString& uc, int& lenInOut);
};


class QTextStatelessDecoder : public QTextDecoder {
    const QTextCodec* codec;
public:
    QTextStatelessDecoder(const QTextCodec*);
    QString toUnicode(const char* chars, int len);
};

QTextStatelessEncoder::QTextStatelessEncoder(const QTextCodec* c) :
    codec(c)
{
}


QCString QTextStatelessEncoder::fromUnicode(const QString& uc, int& lenInOut)
{
    return codec->fromUnicode(uc,lenInOut);
}


QTextStatelessDecoder::QTextStatelessDecoder(const QTextCodec* c) :
    codec(c)
{
}


QString QTextStatelessDecoder::toUnicode(const char* chars, int len)
{
    return codec->toUnicode(chars,len);
}



// NOT REVISED
/*!
  \class QTextCodec qtextcodec.h
  \brief Provides conversion between text encodings.

  By making objects of subclasses of QTextCodec, support for
  new text encodings can be added to Qt.

  The abstract virtual functions describe the encoder to the
  system and the coder is used as required in the different
  text file formats supported QTextStream and, under X11 for the
  locale-specific character input and output (under Windows NT
  codecs are not needed for GUI I/O since the system works
  with Unicode already, and Windows 95/98 has built-in convertors
  for the 8-bit local encoding).

  More recently created QTextCodec objects take precedence
  over earlier ones.

  To add support for another 8-bit encoding to Qt, make a subclass
  or QTextCodec and implement at least the following methods:
  <dl>
   <dt>\c const char* name() const
    <dd>Return the official name for the encoding.
   <dt>\c int mibEnum() const
    <dd>Return the MIB enum for the encoding if it is listed in the
      <a href=ftp://ftp.isi.edu/in-notes/iana/assignments/character-sets>
      IANA character-sets encoding file</a>.
  </dl>
  If the encoding is multi-byte then it will have "state"; that is,
  the interpretation of some bytes will be dependent on some preceding
  bytes.  For such an encoding, you will need to implement
  <dl>
   <dt> \c QTextDecoder* makeDecoder() const
    <dd>Return a QTextDecoder that remembers incomplete multibyte
        sequence prefixes or other required state.
  </dl>
  If the encoding does \e not require state, you should implement:
  <dl>
   <dt> \c QString toUnicode(const char* chars, int len) const
    <dd>Converts \e len characters from \e chars to Unicode.
  </dl>
  The base QTextCodec class has default implementations of the above
  two functions, <i>but they are mutually recursive</i>, so you must
  re-implement at least one of them, or both for improved efficiency.

  For conversion from Unicode to 8-bit encodings, it is rarely necessary
  to maintain state.  However, two functions similar to the two above
  are used for encoding:
  <dl>
   <dt> \c QTextEncoder* makeEncoder() const
    <dd>Return a QTextDecoder.
   <dt> \c QCString fromUnicode(const QString& uc, int& lenInOut ) const;
    <dd>Converts \e lenInOut characters (of type QChar) from the start
        of the string \a uc, returning a QCString result, and also returning
        the \link QCString::length() length\endlink
        of the result in lenInOut.
  </dl>
  Again, these are mutually recursive so only one needs to be implemented,
  or both if better efficiency is possible.

  Finally, you must implement:
  <dl>
   <dt> \c int heuristicContentMatch(const char* chars, int len) const
    <dd>Gives a value indicating how likely it is that \e len characters
        from \e chars are in the encoding.
  </dl>
  A good model for this function is the
  QWindowsLocalCodec::heuristicContentMatch function found in the Qt sources.

  A QTextCodec subclass might have improved performance if you also
  re-implement:
  <dl>
   <dt> \c bool canEncode( QChar ) const
    <dd>Test if a Unicode character can be encoded.
   <dt> \c bool canEncode( const QString& ) const
    <dd>Test if a string of Unicode characters can be encoded.
   <dt> \c int heuristicNameMatch(const char* hint) const
    <dd>Test if a possibly non-standard name is referring to the codec.
  </dl>
*/


/*!
  Constructs a QTextCodec, making it of highest precedence.
  The QTextCodec should always be constructed on the heap
  (with new), and once constructed it becomes the responsibility
  of Qt to delete it (which is done at QApplication destruction).
*/
QTextCodec::QTextCodec()
{
    setup();
    all->insert(0,this);
}


/*!
  Destructs the QTextCodec.  Note that you should not delete
  codecs yourself - once created they become the responsibility
  of Qt to delete.
*/
QTextCodec::~QTextCodec()
{
    if ( !destroying_is_ok )
        qWarning("QTextCodec::~QTextCodec() called by application");
    if ( all )
        all->remove( this );
}


/*!
  Returns a value indicating how likely this decoder is
  for decoding some format that has the given name.

  A good match returns a positive number around
  the length of the string.  A bad match is negative.

  The default implementation calls simpleHeuristicNameMatch()
  with the name of the codec.
*/
int QTextCodec::heuristicNameMatch(const char* hint) const
{
    return simpleHeuristicNameMatch(name(),hint);
}


// returns a string cotnaining the letters and numbers from input,
// with a space separating run of a character class.  e.g. "iso8859-1"
// becomes "iso 8859 1"
static QString lettersAndNumbers( const char * input )
{
    QString result;
    QChar c;

    while( input && *input ) {
        c = *input;
        if ( c.isLetter() || c.isNumber() )
            result += c.lower();
        if ( input[1] ) {
            // add space at character class transition, except
            // transition from upper-case to lower-case letter
            QChar n( input[1] );
            if ( c.isLetter() && n.isLetter() ) {
                if ( c == c.lower() && n == n.upper() )
                    result += ' ';
            } else if ( c.category() != n.category() ) {
                result += ' ';
            }
        }
        input++;
    }
    return result.simplifyWhiteSpace();
}

/*!
  A simple utility function for heuristicNameMatch() - it
  does some very minor character-skipping
  so that almost-exact matches score high.
*/
int QTextCodec::simpleHeuristicNameMatch(const char* name, const char* hint)
{
    // if they're the same, return a perfect score.
    if ( name && hint && qstrcmp( name, hint ) == 0 )
        return qstrlen( hint );

    // if the letters and numbers are the same, we have an "almost"
    // perfect match.
    QString h( lettersAndNumbers( hint ) );
    QString n( lettersAndNumbers( name ) );
    if ( h == n )
        return qstrlen( hint )-1;

    if ( h.stripWhiteSpace() == n.stripWhiteSpace() )
        return qstrlen( hint )-2;

    // could do some more here, but I don't think it's worth it

    return 0;
}


/*!
  Returns the QTextCodec \a i places from the more recently