/****************************************************************************
** $Id: qbuffer.cpp,v 1.1 2002/03/18 13:37:11 thiagocorrea Exp $
**
** Implementation of QBuffer class
**
** Created : 930812
**
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**
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** 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.
**
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** licenses may use this file in accordance with the Qt Commercial License
** Agreement provided with the Software.
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**   information about Qt Commercial License Agreements.
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**********************************************************************/

#include "qbuffer.h"
#include <stdlib.h>

// REVISED: paul
/*!
  \class QBuffer qbuffer.h
  \ingroup io
  \ingroup collection
  \brief The QBuffer class is an I/O device that operates on a QByteArray.

  QBuffer is used to read and write to a memory buffer. It is normally
  used with a QTextStream or a QDataStream.  QBuffer has an
  associated QByteArray which holds the buffer data. The size() of the
  buffer is automatically adjusted as data is written.

  The constructor \c QBuffer(QByteArray) creates a QBuffer with an
  existing byte array.  The byte array can also be set with setBuffer().
  Writing to the QBuffer will modify the original byte array because
  QByteArray is \link shclass.html explicitly shared.\endlink

  Use open() to open the buffer before use and to set the mode
  (read-only, write-only, etc.).  close() closes the buffer. The buffer
  must be closed before reopening or calling setBuffer().

  A common way to use QBuffer is through \l QDataStream or \l QTextStream,
  which have constructors that take a QBuffer parameter. For
  convenience, there are also QDataStream and QTextStream constructors
  that take a QByteArray parameter.  These constructors create and open
  an internal QBuffer.

  Note that QTextStream can also operate on a QString (a Unicode
  string); a QBuffer cannot.

  You can also use QBuffer directly through the standard QIODevice
  functions readBlock(), writeBlock() readLine(), at(), getch(), putch() and
  ungetch().

  \sa QFile, QDataStream, QTextStream, QByteArray, \link shclass.html Shared Classes\endlink
*/


/*!
  Constructs an empty buffer.
*/

QBuffer::QBuffer()
{
    setFlags( IO_Direct );
    a_inc = 16;                                 // initial increment
    a_len = 0;
    ioIndex = 0;
}


/*!
  Constructs a buffer that operates on \a buf.
  If you open the buffer in write mode (\c IO_WriteOnly or
  \c IO_ReadWrite) and write something into the buffer, \a buf
  will be modified.


  Example:
  \code
    QCString str = "abc";
    QBuffer b( str );
    b.open( IO_WriteOnly );
    b.at( 3 ); // position at the 4th character (the terminating \0)
    b.writeBlock( "def", 4 ); // write "def" including the terminating \0
    b.close();
    // Now, str == "abcdef" with a terminating \0
  \endcode


  \sa setBuffer()
*/

QBuffer::QBuffer( QByteArray buf ) : a(buf)
{
    setFlags( IO_Direct );
    a_len = a.size();
    a_inc = (a_len > 512) ? 512 : a_len;        // initial increment
    if ( a_inc < 16 )
        a_inc = 16;
    ioIndex = 0;
}

/*!
  Destroys the buffer.
*/

QBuffer::~QBuffer()
{
}


/*!
  Replaces the buffer's contents with \a buf.

  This may not be done when isOpen() is TRUE.

  Note that if you open the buffer in write mode (\c IO_WriteOnly or
  IO_ReadWrite) and write something into the buffer, \a buf is also
  modified because QByteArray is an explicitly shared class.

  \sa buffer(), open(), close()
*/

bool QBuffer::setBuffer( QByteArray buf )
{
    if ( isOpen() ) {
#if defined(QT_CHECK_STATE)
        qWarning( "QBuffer::setBuffer: Buffer is open");
#endif
        return FALSE;
    }
    a = buf;
    a_len = a.size();
    a_inc = (a_len > 512) ? 512 : a_len;        // initial increment
    if ( a_inc < 16 )
        a_inc = 16;
    ioIndex = 0;
    return TRUE;
}

/*!
  \fn QByteArray QBuffer::buffer() const

  Returns this buffer's byte array.

  \sa setBuffer()
*/

/*!
  \reimp
  Opens the buffer in mode \a m.  Returns TRUE if successful;
  otherwise returns FALSE. The buffer must be opened before use.

  The mode parameter \a m must be a combination of the following flags.
  <ul>
  <li>\c IO_ReadOnly opens the buffer in read-only mode.
  <li>\c IO_WriteOnly opens the buffer in write-only mode.
  <li>\c IO_ReadWrite opens the buffer in read/write mode.
  <li>\c IO_Append sets the buffer index to the end of the buffer.
  <li>\c IO_Truncate truncates the buffer.
  </ul>

  \sa close(), isOpen()
*/

bool QBuffer::open( int m  )
{
    if ( isOpen() ) {                           // buffer already open
#if defined(QT_CHECK_STATE)
        qWarning( "QBuffer::open: Buffer already open" );
#endif
        return FALSE;
    }
    setMode( m );
    if ( m & IO_Truncate ) {                    // truncate buffer
        a.resize( 0 );
        a_len = 0;
    }
    if ( m & IO_Append ) {                      // append to end of buffer
        ioIndex = a.size();
    } else {
        ioIndex = 0;
    }
    a_inc = 16;
    setState( IO_Open );
    setStatus( 0 );
    return TRUE;
}

/*!
  \reimp
  Closes an open buffer.
  \sa open()
*/

void QBuffer::close()
{
    if ( isOpen() ) {
        setFlags( IO_Direct );
        ioIndex = 0;
        a_inc = 16;
    }
}

/*!
  \reimp
  The flush function does nothing for a QBuffer.
*/

void QBuffer::flush()
{
    return;
}


/*!
  \fn QIODevice::Offset QBuffer::at() const
  \reimp
*/

/*!
  \fn QIODevice::Offset QBuffer::size() const
  \reimp
*/

/*!
  \reimp
*/

bool QBuffer::at( Offset pos )
{
#if defined(QT_CHECK_STATE)
    if ( !isOpen() ) {
        qWarning( "QBuffer::at: Buffer is not open" );
        return FALSE;
    }
#endif
    if ( pos > a_len ) {
#if defined(QT_CHECK_RANGE)
        qWarning( "QBuffer::at: Index %ld out of range", pos );
#endif
        return FALSE;
    }
    ioIndex = pos;
    return TRUE;
}


/*!
  \reimp
*/

Q_LONG QBuffer::readBlock( char *p, Q_ULONG len )
{
#if defined(QT_CHECK_STATE)
    Q_CHECK_PTR( p );
    if ( !isOpen() ) {                          // buffer not open
        qWarning( "QBuffer::readBlock: Buffer not open" );
        return -1;
    }
    if ( !isReadable() ) {                      // reading not permitted
        qWarning( "QBuffer::readBlock: Read operation not permitted" );
        return -1;
    }
#endif
    if ( ioIndex + len > a.size() ) {   // overflow
        if ( ioIndex >= a.size() ) {
            setStatus( IO_ReadError );
            return -1;
        } else {
            len = a.size() - ioIndex;
        }
    }
    memcpy( p, a.data()+ioIndex, len );
    ioIndex += len;
    return len;
}

/*!
    \overload Q_LONG QBuffer::writeBlock( const QByteArray& data )

  This convenience function takes \a data and is the same as calling
  \c{writeBlock( data.data(), data.size() )}.

*/

/*!

  Writes \a len bytes from \a p into the buffer at the current index,
  overwriting any characters there and extending the buffer if necessary.
  Returns the number of bytes actually written.

  Returns -1 if an error occurred.

  \sa readBlock()
*/

Q_LONG QBuffer::writeBlock( const char *p, Q_ULONG len )
{
    if ( len == 0 )
        return 0;

#if defined(QT_CHECK_NULL)
    if ( p == 0 ) {
        qWarning( "QBuffer::writeBlock: Null pointer error" );
        return -1;
    }
#endif
#if defined(QT_CHECK_STATE)
    if ( !isOpen() ) {                          // buffer not open
        qWarning( "QBuffer::writeBlock: Buffer not open" );
        return -1;
    }
    if ( !isWritable() ) {                      // writing not permitted
        qWarning( "QBuffer::writeBlock: Write operation not permitted" );
        return -1;
    }
#endif
    if ( ioIndex + len >= a_len ) {             // overflow
        Q_ULONG new_len = a_len + a_inc*((ioIndex+len-a_len)/a_inc+1);
        if ( !a.resize( new_len ) ) {           // could not resize
#if defined(QT_CHECK_NULL)
            qWarning( "QBuffer::writeBlock: Memory allocation error" );
#endif
            setStatus( IO_ResourceError );
            return -1;
        }
        a_inc *= 2;                             // double increment
        a_len = new_len;
        a.shd->len = ioIndex + len;
    }
    memcpy( a.data()+ioIndex, p, len );
    ioIndex += len;
    if ( a.shd->len < ioIndex )
        a.shd->len = ioIndex;                   // fake (not alloc'd) length
    return len;
}


/*!
  \reimp
*/

Q_LONG QBuffer::readLine( char *p, Q_ULONG maxlen )
{
#if defined(QT_CHECK_STATE)
    Q_CHECK_PTR( p );
    if ( !isOpen() ) {                          // buffer not open
        qWarning( "QBuffer::readLine: Buffer not open" );
        return -1;
    }
    if ( !isReadable() ) {                      // reading not permitted
        qWarning( "QBuffer::readLine: Read operation not permitted" );
        return -1;
    }
#endif
    if ( maxlen == 0 )
        return 0;
    Q_ULONG start = ioIndex;
    char *d = a.data() + ioIndex;
    maxlen--;                                   // make room for 0-terminator
    if ( a.size() - ioIndex < maxlen )
        maxlen = a.size() - ioIndex;
    while ( maxlen-- ) {
        if ( (*p++ = *d++) == '\n' )
            break;
    }
    *p = '\0';
    ioIndex = d - a.data();
    return ioIndex - start;
}


/*!
  \reimp
*/

int QBuffer::getch()
{
#if defined(QT_CHECK_STATE)
    if ( !isOpen() ) {                          // buffer not open
        qWarning( "QBuffer::getch: Buffer not open" );
        return -1;
    }
    if ( !isReadable() ) {                      // reading not permitted
        qWarning( "QBuffer::getch: Read operation not permitted" );
        return -1;
    }
#endif
    if ( ioIndex+1 > a.size() ) {               // overflow
        setStatus( IO_ReadError );
        return -1;
    }
    return uchar(*(a.data()+ioIndex++));
}

/*!
  \reimp
  Writes the character \a ch into the buffer, overwriting
  the character at the current index, extending the buffer
  if necessary.

  Returns \a ch, or -1 if some error occurred.

  \sa getch(), ungetch()
*/

int QBuffer::putch( int ch )
{
#if defined(QT_CHECK_STATE)
    if ( !isOpen() ) {                          // buffer not open
        qWarning( "QBuffer::putch: Buffer not open" );
        return -1;
    }
    if ( !isWritable() ) {                      // writing not permitted
        qWarning( "QBuffer::putch: Write operation not permitted" );
        return -1;
    }
#endif
    if ( ioIndex + 1 >= a_len ) {               // overflow
        char buf[1];
        buf[0] = (char)ch;
        if ( writeBlock(buf,1) != 1 )
            return -1;                          // write error
    } else {
        *(a.data() + ioIndex++) = (char)ch;
        if ( a.shd->len < ioIndex )
            a.shd->len = ioIndex;
    }
    return ch;
}

/*!
  \reimp
*/

int QBuffer::ungetch( int ch )
{
#if defined(QT_CHECK_STATE)
    if ( !isOpen() ) {                          // buffer not open
        qWarning( "QBuffer::ungetch: Buffer not open" );
        return -1;
    }
    if ( !isReadable() ) {                      // reading not permitted
        qWarning( "QBuffer::ungetch: Read operation not permitted" );
        return -1;
    }
#endif
    if ( ch != -1 ) {
        if ( ioIndex )
            ioIndex--;
        else
            ch = -1;
    }
    return ch;
}

