Optimize wxImage::Scale() by pre-calculating the values used.

[wxWidgets.git] / src / common / stream.cpp

/////////////////////////////////////////////////////////////////////////////
// Name:        src/common/stream.cpp
// Purpose:     wxStream base classes
// Author:      Guilhem Lavaux
// Modified by: VZ (23.11.00) to fix realloc()ing new[]ed memory,
//                            general code review
// Created:     11/07/98
// RCS-ID:      $Id$
// Copyright:   (c) Guilhem Lavaux
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

// ============================================================================
// declarations
// ============================================================================

// ----------------------------------------------------------------------------
// headers
// ----------------------------------------------------------------------------

// For compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
    #pragma hdrstop
#endif

#if wxUSE_STREAMS

#include "wx/stream.h"

#ifndef WX_PRECOMP
    #include "wx/log.h"
#endif

#include <ctype.h>
#include "wx/datstrm.h"
#include "wx/textfile.h"
#include "wx/scopeguard.h"

// ----------------------------------------------------------------------------
// constants
// ----------------------------------------------------------------------------

// the temporary buffer size used when copying from stream to stream
#define BUF_TEMP_SIZE 4096

// ============================================================================
// implementation
// ============================================================================

// ----------------------------------------------------------------------------
// wxStreamBuffer
// ----------------------------------------------------------------------------

void wxStreamBuffer::SetError(wxStreamError err)
{
   if ( m_stream && m_stream->m_lasterror == wxSTREAM_NO_ERROR )
       m_stream->m_lasterror = err;
}

void wxStreamBuffer::InitBuffer()
{
    m_buffer_start =
    m_buffer_end =
    m_buffer_pos = NULL;

    // if we are going to allocate the buffer, we should free it later as well
    m_destroybuf = true;
}

void wxStreamBuffer::Init()
{
    InitBuffer();

    m_fixed = true;
}

void wxStreamBuffer::InitWithStream(wxStreamBase& stream, BufMode mode)
{
    Init();

    m_stream = &stream;
    m_mode = mode;

    m_flushable = true;
}

wxStreamBuffer::wxStreamBuffer(BufMode mode)
{
    Init();

    m_stream = NULL;
    m_mode = mode;

    m_flushable = false;
}

wxStreamBuffer::wxStreamBuffer(const wxStreamBuffer& buffer)
{
    // doing this has big chances to lead to a crash when the source buffer is
    // destroyed (otherwise assume the caller knows what he does)
    wxASSERT_MSG( !buffer.m_destroybuf,
                  wxT("it's a bad idea to copy this buffer") );

    m_buffer_start = buffer.m_buffer_start;
    m_buffer_end = buffer.m_buffer_end;
    m_buffer_pos = buffer.m_buffer_pos;
    m_fixed = buffer.m_fixed;
    m_flushable = buffer.m_flushable;
    m_stream = buffer.m_stream;
    m_mode = buffer.m_mode;
    m_destroybuf = false;
}

void wxStreamBuffer::FreeBuffer()
{
    if ( m_destroybuf )
    {
        free(m_buffer_start);
        m_buffer_start = NULL;
    }
}

wxStreamBuffer::~wxStreamBuffer()
{
    FreeBuffer();
}

wxInputStream *wxStreamBuffer::GetInputStream() const
{
    return m_mode == write ? NULL : (wxInputStream *)m_stream;
}

wxOutputStream *wxStreamBuffer::GetOutputStream() const
{
    return m_mode == read ? NULL : (wxOutputStream *)m_stream;
}

void wxStreamBuffer::SetBufferIO(void *buffer_start,
                                 void *buffer_end,
                                 bool takeOwnership)
{
    SetBufferIO(buffer_start, (char *)buffer_end - (char *)buffer_start,
                takeOwnership);
}

void wxStreamBuffer::SetBufferIO(void *start,
                                 size_t len,
                                 bool takeOwnership)
{
    // start by freeing the old buffer
    FreeBuffer();

    m_buffer_start = (char *)start;
    m_buffer_end   = m_buffer_start + len;

    // if we own it, we free it
    m_destroybuf = takeOwnership;

    ResetBuffer();
}

void wxStreamBuffer::SetBufferIO(size_t bufsize)
{
    if ( bufsize )
    {
        // this will free the old buffer and allocate the new one
        SetBufferIO(malloc(bufsize), bufsize, true /* take ownership */);
    }
    else // no buffer size => no buffer
    {
        // still free the old one
        FreeBuffer();
        InitBuffer();
    }
}

void wxStreamBuffer::ResetBuffer()
{
    if ( m_stream )
    {
        m_stream->Reset();
        m_stream->m_lastcount = 0;
    }

    m_buffer_pos = m_mode == read && m_flushable
                        ? m_buffer_end
                        : m_buffer_start;
}

void wxStreamBuffer::Truncate()
{
    size_t new_size = m_buffer_pos - m_buffer_start;
    if ( m_buffer_pos == m_buffer_end )
        return;

    if ( !new_size )
    {
        FreeBuffer();
        InitBuffer();
        return;
    }

    char *new_start = (char *)realloc(m_buffer_start, new_size);
    wxCHECK_RET( new_size, wxT("shrinking buffer shouldn't fail") );

    m_buffer_start = new_start;
    m_buffer_end = m_buffer_start + new_size;
    m_buffer_pos = m_buffer_end;
}

// fill the buffer with as much data as possible (only for read buffers)
bool wxStreamBuffer::FillBuffer()
{
    wxInputStream *inStream = GetInputStream();

    // It's legal to have no stream, so we don't complain about it just return false
    if ( !inStream )
        return false;

    size_t count = inStream->OnSysRead(GetBufferStart(), GetBufferSize());
    if ( !count )
        return false;

    m_buffer_end = m_buffer_start + count;
    m_buffer_pos = m_buffer_start;

    return true;
}

// write the buffer contents to the stream (only for write buffers)
bool wxStreamBuffer::FlushBuffer()
{
    wxCHECK_MSG( m_flushable, false, wxT("can't flush this buffer") );

    // FIXME: what is this check for? (VZ)
    if ( m_buffer_pos == m_buffer_start )
        return false;

    wxOutputStream *outStream = GetOutputStream();

    wxCHECK_MSG( outStream, false, wxT("should have a stream in wxStreamBuffer") );

    size_t current = m_buffer_pos - m_buffer_start;
    size_t count = outStream->OnSysWrite(m_buffer_start, current);
    if ( count != current )
        return false;

    m_buffer_pos = m_buffer_start;

    return true;
}

size_t wxStreamBuffer::GetDataLeft()
{
    /* Why is this done? RR. */
    if ( m_buffer_pos == m_buffer_end && m_flushable)
        FillBuffer();

    return GetBytesLeft();
}

// copy up to size bytes from our buffer into the provided one
void wxStreamBuffer::GetFromBuffer(void *buffer, size_t size)
{
    // don't get more bytes than left in the buffer
    size_t left = GetBytesLeft();

    if ( size > left )
        size = left;

    memcpy(buffer, m_buffer_pos, size);
    m_buffer_pos += size;
}

// copy the contents of the provided buffer into this one
void wxStreamBuffer::PutToBuffer(const void *buffer, size_t size)
{
    size_t left = GetBytesLeft();

    if ( size > left )
    {
        if ( m_fixed )
        {
            // we can't realloc the buffer, so just copy what we can
            size = left;
        }
        else // !m_fixed
        {
            // realloc the buffer to have enough space for the data
            if ( m_buffer_pos + size > m_buffer_end )
            {
                size_t delta = m_buffer_pos - m_buffer_start;
                size_t new_size = delta + size;

                char *startOld = m_buffer_start;
                m_buffer_start = (char *)realloc(m_buffer_start, new_size);
                if ( !m_buffer_start )
                {
                    // don't leak memory if realloc() failed
                    m_buffer_start = startOld;

                    // what else can we do?
                    return;
                }

                // adjust the pointers invalidated by realloc()
                m_buffer_pos = m_buffer_start + delta;
                m_buffer_end = m_buffer_start + new_size;
            } // else: the buffer is big enough
        }
    }

    memcpy(m_buffer_pos, buffer, size);
    m_buffer_pos += size;
}

void wxStreamBuffer::PutChar(char c)
{
    wxOutputStream *outStream = GetOutputStream();

    wxCHECK_RET( outStream, wxT("should have a stream in wxStreamBuffer") );

    // if we don't have buffer at all, just forward this call to the stream,
    if ( !HasBuffer() )
    {
        outStream->OnSysWrite(&c, sizeof(c));
    }
    else
    {
        // otherwise check we have enough space left
        if ( !GetDataLeft() && !FlushBuffer() )
        {
            // we don't
            SetError(wxSTREAM_WRITE_ERROR);
        }
        else
        {
            PutToBuffer(&c, sizeof(c));
            m_stream->m_lastcount = 1;
        }
    }
}

char wxStreamBuffer::Peek()
{
    wxCHECK_MSG( m_stream && HasBuffer(), 0,
                 wxT("should have the stream and the buffer in wxStreamBuffer") );

    if ( !GetDataLeft() )
    {
        SetError(wxSTREAM_READ_ERROR);
        return 0;
    }

    char c;
    GetFromBuffer(&c, sizeof(c));
    m_buffer_pos--;

    return c;
}

char wxStreamBuffer::GetChar()
{
    wxInputStream *inStream = GetInputStream();

    wxCHECK_MSG( inStream, 0, wxT("should have a stream in wxStreamBuffer") );

    char c;
    if ( !HasBuffer() )
    {
        inStream->OnSysRead(&c, sizeof(c));
    }
    else
    {
        if ( !GetDataLeft() )
        {
            SetError(wxSTREAM_READ_ERROR);
            c = 0;
        }
        else
        {
            GetFromBuffer(&c, sizeof(c));
            m_stream->m_lastcount = 1;
        }
    }

    return c;
}

size_t wxStreamBuffer::Read(void *buffer, size_t size)
{
    wxASSERT_MSG( buffer, wxT("Warning: Null pointer is about to be used") );

    /* Clear buffer first */
    memset(buffer, 0x00, size);

    // lasterror is reset before all new IO calls
    if ( m_stream )
        m_stream->Reset();

    size_t readBytes;
    if ( !HasBuffer() )
    {
        wxInputStream *inStream = GetInputStream();

        wxCHECK_MSG( inStream, 0, wxT("should have a stream in wxStreamBuffer") );

        readBytes = inStream->OnSysRead(buffer, size);
    }
    else // we have a buffer, use it
    {
        size_t orig_size = size;

        while ( size > 0 )
        {
            size_t left = GetDataLeft();

            // if the requested number of bytes if greater than the buffer
            // size, read data in chunks
            if ( size > left )
            {
                GetFromBuffer(buffer, left);
                size -= left;
                buffer = (char *)buffer + left;

                if ( !FillBuffer() )
                {
                    SetError(wxSTREAM_EOF);
                    break;
                }
            }
            else // otherwise just do it in one gulp
            {
                GetFromBuffer(buffer, size);
                size = 0;
            }
        }

        readBytes = orig_size - size;
    }

    if ( m_stream )
        m_stream->m_lastcount = readBytes;

    return readBytes;
}

// this should really be called "Copy()"
size_t wxStreamBuffer::Read(wxStreamBuffer *dbuf)
{
    wxCHECK_MSG( m_mode != write, 0, wxT("can't read from this buffer") );

    char buf[BUF_TEMP_SIZE];
    size_t nRead,
           total = 0;

    do
    {
        nRead = Read(buf, WXSIZEOF(buf));
        if ( nRead )
        {
            nRead = dbuf->Write(buf, nRead);
            total += nRead;
        }
    }
    while ( nRead );

    return total;
}

size_t wxStreamBuffer::Write(const void *buffer, size_t size)
{
    wxASSERT_MSG( buffer, wxT("Warning: Null pointer is about to be send") );

    if (m_stream)
    {
        // lasterror is reset before all new IO calls
        m_stream->Reset();
    }

    size_t ret;

    if ( !HasBuffer() && m_fixed )
    {
        wxOutputStream *outStream = GetOutputStream();

        wxCHECK_MSG( outStream, 0, wxT("should have a stream in wxStreamBuffer") );

        // no buffer, just forward the call to the stream
        ret = outStream->OnSysWrite(buffer, size);
    }
    else // we [may] have a buffer, use it
    {
        size_t orig_size = size;

        while ( size > 0 )
        {
            size_t left = GetBytesLeft();

            // if the buffer is too large to fit in the stream buffer, split
            // it in smaller parts
            //
            // NB: If stream buffer isn't fixed (as for wxMemoryOutputStream),
            //     we always go to the second case.
            //
            // FIXME: fine, but if it fails we should (re)try writing it by
            //        chunks as this will (hopefully) always work (VZ)

            if ( size > left && m_fixed )
            {
                PutToBuffer(buffer, left);
                size -= left;
                buffer = (char *)buffer + left;

                if ( !FlushBuffer() )
                {
                    SetError(wxSTREAM_WRITE_ERROR);

                    break;
                }

                m_buffer_pos = m_buffer_start;
            }
            else // we can do it in one gulp
            {
                PutToBuffer(buffer, size);
                size = 0;
            }
        }

        ret = orig_size - size;
    }

    if (m_stream)
    {
        // i am not entirely sure what we do this for
        m_stream->m_lastcount = ret;
    }

    return ret;
}

size_t wxStreamBuffer::Write(wxStreamBuffer *sbuf)
{
    wxCHECK_MSG( m_mode != read, 0, wxT("can't write to this buffer") );
    wxCHECK_MSG( sbuf->m_mode != write, 0, wxT("can't read from that buffer") );

    char buf[BUF_TEMP_SIZE];
    size_t nWrite,
           total = 0;

    do
    {
        size_t nRead = sbuf->Read(buf, WXSIZEOF(buf));
        if ( nRead )
        {
            nWrite = Write(buf, nRead);
            if ( nWrite < nRead )
            {
                // put back data we couldn't copy
                wxInputStream *in_stream = (wxInputStream *)sbuf->GetStream();

                in_stream->Ungetch(buf + nWrite, nRead - nWrite);
            }

            total += nWrite;
        }
        else
        {
            nWrite = 0;
        }
    }
    while ( nWrite == WXSIZEOF(buf) );

    return total;
}

wxFileOffset wxStreamBuffer::Seek(wxFileOffset pos, wxSeekMode mode)
{
    wxFileOffset ret_off, diff;

    wxFileOffset last_access = GetLastAccess();

    if ( !m_flushable )
    {
        switch (mode)
        {
            case wxFromStart:
                diff = pos;
                break;

            case wxFromCurrent:
                diff = pos + GetIntPosition();
                break;

            case wxFromEnd:
                diff = pos + last_access;
                break;

            default:
                wxFAIL_MSG( wxT("invalid seek mode") );

                return wxInvalidOffset;
        }
        if (diff < 0 || diff > last_access)
            return wxInvalidOffset;
        size_t int_diff = wx_truncate_cast(size_t, diff);
        wxCHECK_MSG( (wxFileOffset)int_diff == diff, wxInvalidOffset, wxT("huge file not supported") );
        SetIntPosition(int_diff);
        return diff;
    }

    switch ( mode )
    {
        case wxFromStart:
            // We'll try to compute an internal position later ...
            ret_off = m_stream->OnSysSeek(pos, wxFromStart);
            ResetBuffer();
            return ret_off;

        case wxFromCurrent:
            diff = pos + GetIntPosition();

            if ( (diff > last_access) || (diff < 0) )
            {
                // We must take into account the fact that we have read
                // something previously.
                ret_off = m_stream->OnSysSeek(diff-last_access, wxFromCurrent);
                ResetBuffer();
                return ret_off;
            }
            else
            {
                size_t int_diff = wx_truncate_cast(size_t, diff);
                wxCHECK_MSG( (wxFileOffset)int_diff == diff, wxInvalidOffset, wxT("huge file not supported") );
                SetIntPosition(int_diff);
                return diff;
            }

        case wxFromEnd:
            // Hard to compute: always seek to the requested position.
            ret_off = m_stream->OnSysSeek(pos, wxFromEnd);
            ResetBuffer();
            return ret_off;
    }

    return wxInvalidOffset;
}

wxFileOffset wxStreamBuffer::Tell() const
{
    wxFileOffset pos;

    // ask the stream for position if we have a real one
    if ( m_stream )
    {
        pos = m_stream->OnSysTell();
        if ( pos == wxInvalidOffset )
            return wxInvalidOffset;
    }
    else // no associated stream
    {
        pos = 0;
    }

    pos += GetIntPosition();

    if ( m_mode == read && m_flushable )
        pos -= GetLastAccess();

    return pos;
}

// ----------------------------------------------------------------------------
// wxStreamBase
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxStreamBase, wxObject)

wxStreamBase::wxStreamBase()
{
    m_lasterror = wxSTREAM_NO_ERROR;
    m_lastcount = 0;
}

wxStreamBase::~wxStreamBase()
{
}

size_t wxStreamBase::GetSize() const
{
    wxFileOffset length = GetLength();
    if ( length == (wxFileOffset)wxInvalidOffset )
        return 0;

    const size_t len = wx_truncate_cast(size_t, length);
    wxASSERT_MSG( len == length + size_t(0), wxT("large files not supported") );

    return len;
}

wxFileOffset wxStreamBase::OnSysSeek(wxFileOffset WXUNUSED(seek), wxSeekMode WXUNUSED(mode))
{
    return wxInvalidOffset;
}

wxFileOffset wxStreamBase::OnSysTell() const
{
    return wxInvalidOffset;
}

// ----------------------------------------------------------------------------
// wxInputStream
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxInputStream, wxStreamBase)

wxInputStream::wxInputStream()
{
    m_wback = NULL;
    m_wbacksize =
    m_wbackcur = 0;
}

wxInputStream::~wxInputStream()
{
    free(m_wback);
}

bool wxInputStream::CanRead() const
{
    // we don't know if there is anything to read or not and by default we
    // prefer to be optimistic and try to read data unless we know for sure
    // there is no more of it
    return m_lasterror != wxSTREAM_EOF;
}

bool wxInputStream::Eof() const
{
    // the only way the base class can know we're at EOF is when we'd already
    // tried to read beyond it in which case last error is set accordingly
    return GetLastError() == wxSTREAM_EOF;
}

char *wxInputStream::AllocSpaceWBack(size_t needed_size)
{
    // get number of bytes left from previous wback buffer
    size_t toget = m_wbacksize - m_wbackcur;

    // allocate a buffer large enough to hold prev + new data
    char *temp_b = (char *)malloc(needed_size + toget);

    if (!temp_b)
        return NULL;

    // copy previous data (and free old buffer) if needed
    if (m_wback)
    {
        memmove(temp_b + needed_size, m_wback + m_wbackcur, toget);
        free(m_wback);
    }

    // done
    m_wback = temp_b;
    m_wbackcur = 0;
    m_wbacksize = needed_size + toget;

    return m_wback;
}

size_t wxInputStream::GetWBack(void *buf, size_t size)
{
    wxASSERT_MSG( buf, wxT("Warning: Null pointer is about to be used") );

    /* Clear buffer first */
    memset(buf, 0x00, size);

    if (!m_wback)
        return 0;

    // how many bytes do we have in the buffer?
    size_t toget = m_wbacksize - m_wbackcur;

    if ( size < toget )
    {
        // we won't read everything
        toget = size;
    }

    // copy the data from the cache
    memcpy(buf, m_wback + m_wbackcur, toget);

    m_wbackcur += toget;
    if ( m_wbackcur == m_wbacksize )
    {
        // TODO: should we really free it here all the time? maybe keep it?
        free(m_wback);
        m_wback = NULL;
        m_wbacksize = 0;
        m_wbackcur = 0;
    }

    // return the number of bytes copied
    return toget;
}

size_t wxInputStream::Ungetch(const void *buf, size_t bufsize)
{
    wxASSERT_MSG( buf, wxT("Warning: Null pointer is about to be used in Ungetch()") );

    if ( m_lasterror != wxSTREAM_NO_ERROR && m_lasterror != wxSTREAM_EOF )
    {
        // can't operate on this stream until the error is cleared
        return 0;
    }

    char *ptrback = AllocSpaceWBack(bufsize);
    if (!ptrback)
        return 0;

    // Eof() shouldn't return true any longer
    if ( m_lasterror == wxSTREAM_EOF )
        m_lasterror = wxSTREAM_NO_ERROR;

    memcpy(ptrback, buf, bufsize);
    return bufsize;
}

bool wxInputStream::Ungetch(char c)
{
    return Ungetch(&c, sizeof(c)) != 0;
}

int wxInputStream::GetC()
{
    unsigned char c;
    Read(&c, sizeof(c));
    return LastRead() ? c : wxEOF;
}

wxInputStream& wxInputStream::Read(void *buf, size_t size)
{
    wxASSERT_MSG( buf, wxT("Warning: Null pointer is about to be read") );

    char *p = (char *)buf;
    m_lastcount = 0;

    size_t read = GetWBack(buf, size);
    for ( ;; )
    {
        size -= read;
        m_lastcount += read;
        p += read;

        if ( !size )
        {
            // we read the requested amount of data
            break;
        }

        if ( p != buf && !CanRead() )
        {
            // we have already read something and we would block in OnSysRead()
            // now: don't do it but return immediately
            break;
        }

        read = OnSysRead(p, size);
        if ( !read )
        {
            // no more data available
            break;
        }
    }

    return *this;
}

char wxInputStream::Peek()
{
    char c;
    Read(&c, sizeof(c));
    if (m_lasterror == wxSTREAM_NO_ERROR)
    {
        Ungetch(c);
        return c;
    }

    return 0;
}

wxInputStream& wxInputStream::Read(wxOutputStream& stream_out)
{
    size_t lastcount = 0;
    char buf[BUF_TEMP_SIZE];

    for ( ;; )
    {
        size_t bytes_read = Read(buf, WXSIZEOF(buf)).LastRead();
        if ( !bytes_read )
            break;

        if ( stream_out.Write(buf, bytes_read).LastWrite() != bytes_read )
            break;

        lastcount += bytes_read;
    }

    m_lastcount = lastcount;

    return *this;
}

bool wxInputStream::ReadAll(void *buffer_, size_t size)
{
    char* buffer = static_cast<char*>(buffer_);

    size_t totalCount = 0;

    for ( ;; )
    {
        const size_t lastCount = Read(buffer, size).LastRead();

        // There is no point in continuing looping if we can't read anything at
        // all.
        if ( !lastCount )
            break;

        totalCount += lastCount;

        // ... Or if an error occurred on the stream.
        if ( !IsOk() )
            break;

        // Return successfully if we read exactly the requested number of
        // bytes (normally the ">" case should never occur and so we could use
        // "==" test, but be safe and avoid overflowing size even in case of
        // bugs in LastRead()).
        if ( lastCount >= size )
        {
            size = 0;
            break;
        }

        // Advance the buffer before trying to read the rest of data.
        size -= lastCount;
        buffer += lastCount;
    }

    m_lastcount = totalCount;

    return size == 0;
}

wxFileOffset wxInputStream::SeekI(wxFileOffset pos, wxSeekMode mode)
{
    // RR: This code is duplicated in wxBufferedInputStream. This is
    // not really a good design, but buffered stream are different
    // from all others in that they handle two stream-related objects:
    // the stream buffer and parent stream.

    // I don't know whether it should be put as well in wxFileInputStream::OnSysSeek
    if (m_lasterror==wxSTREAM_EOF)
        m_lasterror=wxSTREAM_NO_ERROR;

    // avoid unnecessary seek operations (optimization)
    wxFileOffset currentPos = TellI(), size = GetLength();
    if ((mode == wxFromStart && currentPos == pos) ||
        (mode == wxFromCurrent && pos == 0) ||
        (mode == wxFromEnd && size != wxInvalidOffset && currentPos == size-pos))
        return currentPos;

    if (!IsSeekable() && mode == wxFromCurrent && pos > 0)
    {
        // rather than seeking, we can just read data and discard it;
        // this allows to forward-seek also non-seekable streams!
        char buf[BUF_TEMP_SIZE];
        size_t bytes_read;

        // read chunks of BUF_TEMP_SIZE bytes until we reach the new position
        for ( ; pos >= BUF_TEMP_SIZE; pos -= bytes_read)
        {
            bytes_read = Read(buf, WXSIZEOF(buf)).LastRead();
            if ( m_lasterror != wxSTREAM_NO_ERROR )
                return wxInvalidOffset;

            wxASSERT(bytes_read == WXSIZEOF(buf));
        }

        // read the last 'pos' bytes
        bytes_read = Read(buf, (size_t)pos).LastRead();
        if ( m_lasterror != wxSTREAM_NO_ERROR )
            return wxInvalidOffset;

        wxASSERT(bytes_read == (size_t)pos);

        // we should now have sought to the right position...
        return TellI();
    }

    /* RR: A call to SeekI() will automatically invalidate any previous
       call to Ungetch(), otherwise it would be possible to SeekI() to
       one position, unread some bytes there, SeekI() to another position
       and the data would be corrupted.

       GRG: Could add code here to try to navigate within the wback
       buffer if possible, but is it really needed? It would only work
       when seeking in wxFromCurrent mode, else it would invalidate
       anyway... */

    if (m_wback)
    {
        wxLogDebug( wxT("Seeking in stream which has data written back to it.") );

        free(m_wback);
        m_wback = NULL;
        m_wbacksize = 0;
        m_wbackcur = 0;
    }

    return OnSysSeek(pos, mode);
}

wxFileOffset wxInputStream::TellI() const
{
    wxFileOffset pos = OnSysTell();

    if (pos != wxInvalidOffset)
        pos -= (m_wbacksize - m_wbackcur);

    return pos;
}


// ----------------------------------------------------------------------------
// wxOutputStream
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxOutputStream, wxStreamBase)

wxOutputStream::wxOutputStream()
{
}

wxOutputStream::~wxOutputStream()
{
}

size_t wxOutputStream::OnSysWrite(const void * WXUNUSED(buffer),
                                  size_t WXUNUSED(bufsize))
{
    return 0;
}

void wxOutputStream::PutC(char c)
{
    Write(&c, sizeof(c));
}

wxOutputStream& wxOutputStream::Write(const void *buffer, size_t size)
{
    m_lastcount = OnSysWrite(buffer, size);
    return *this;
}

wxOutputStream& wxOutputStream::Write(wxInputStream& stream_in)
{
    stream_in.Read(*this);
    return *this;
}

bool wxOutputStream::WriteAll(const void *buffer_, size_t size)
{
    // This exactly mirrors ReadAll(), see there for more comments.
    const char* buffer = static_cast<const char*>(buffer_);

    size_t totalCount = 0;

    for ( ;; )
    {
        const size_t lastCount = Write(buffer, size).LastWrite();
        if ( !lastCount )
            break;

        totalCount += lastCount;

        if ( !IsOk() )
            break;

        if ( lastCount >= size )
        {
            size = 0;
            break;
        }

        size -= lastCount;
        buffer += lastCount;
    }

    m_lastcount = totalCount;
    return size == 0;
}

wxFileOffset wxOutputStream::TellO() const
{
    return OnSysTell();
}

wxFileOffset wxOutputStream::SeekO(wxFileOffset pos, wxSeekMode mode)
{
    return OnSysSeek(pos, mode);
}

void wxOutputStream::Sync()
{
}


// ----------------------------------------------------------------------------
// wxCountingOutputStream
// ----------------------------------------------------------------------------

IMPLEMENT_DYNAMIC_CLASS(wxCountingOutputStream, wxOutputStream)

wxCountingOutputStream::wxCountingOutputStream ()
{
    m_currentPos =
    m_lastPos = 0;
}

wxFileOffset wxCountingOutputStream::GetLength() const
{
    return m_lastPos;
}

size_t wxCountingOutputStream::OnSysWrite(const void *WXUNUSED(buffer),
                                          size_t size)
{
    m_currentPos += size;
    if ( m_currentPos > m_lastPos )
        m_lastPos = m_currentPos;

    return size;
}

wxFileOffset wxCountingOutputStream::OnSysSeek(wxFileOffset pos, wxSeekMode mode)
{
    ssize_t new_pos = wx_truncate_cast(ssize_t, pos);

    switch ( mode )
    {
        case wxFromStart:
            wxCHECK_MSG( (wxFileOffset)new_pos == pos, wxInvalidOffset, wxT("huge position not supported") );
            break;

        case wxFromEnd:
            new_pos += m_lastPos;
            wxCHECK_MSG( (wxFileOffset)new_pos == (wxFileOffset)(m_lastPos + pos), wxInvalidOffset, wxT("huge position not supported") );
            break;

        case wxFromCurrent:
            new_pos += m_currentPos;
            wxCHECK_MSG( (wxFileOffset)new_pos == (wxFileOffset)(m_currentPos + pos), wxInvalidOffset, wxT("huge position not supported") );
            break;

        default:
            wxFAIL_MSG( wxT("invalid seek mode") );
            return wxInvalidOffset;
    }

    m_currentPos = new_pos;

    if ( m_currentPos > m_lastPos )
        m_lastPos = m_currentPos;

    return m_currentPos;
}

wxFileOffset wxCountingOutputStream::OnSysTell() const
{
    return m_currentPos;
}

// ----------------------------------------------------------------------------
// wxFilterInputStream
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxFilterInputStream, wxInputStream)

wxFilterInputStream::wxFilterInputStream()
 :  m_parent_i_stream(NULL),
    m_owns(false)
{
}

wxFilterInputStream::wxFilterInputStream(wxInputStream& stream)
 :  m_parent_i_stream(&stream),
    m_owns(false)
{
}

wxFilterInputStream::wxFilterInputStream(wxInputStream *stream)
 :  m_parent_i_stream(stream),
    m_owns(true)
{
}

wxFilterInputStream::~wxFilterInputStream()
{
    if (m_owns)
        delete m_parent_i_stream;
}

// ----------------------------------------------------------------------------
// wxFilterOutputStream
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxFilterOutputStream, wxOutputStream)

wxFilterOutputStream::wxFilterOutputStream()
 :  m_parent_o_stream(NULL),
    m_owns(false)
{
}

wxFilterOutputStream::wxFilterOutputStream(wxOutputStream& stream)
 :  m_parent_o_stream(&stream),
    m_owns(false)
{
}

wxFilterOutputStream::wxFilterOutputStream(wxOutputStream *stream)
 :  m_parent_o_stream(stream),
    m_owns(true)
{
}

bool wxFilterOutputStream::Close()
{
    if (m_parent_o_stream && m_owns)
        return m_parent_o_stream->Close();
    else
        return true;
}

wxFilterOutputStream::~wxFilterOutputStream()
{
    if (m_owns)
        delete m_parent_o_stream;
}

// ----------------------------------------------------------------------------
// wxFilterClassFactoryBase
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxFilterClassFactoryBase, wxObject)

wxString wxFilterClassFactoryBase::PopExtension(const wxString& location) const
{
    return location.substr(0, FindExtension(location));
}

wxString::size_type wxFilterClassFactoryBase::FindExtension(
        const wxString& location) const
{
    for (const wxChar *const *p = GetProtocols(wxSTREAM_FILEEXT); *p; p++)
    {
        if ( location.EndsWith(*p) )
            return location.length() - wxStrlen(*p);
    }

    return wxString::npos;
}

bool wxFilterClassFactoryBase::CanHandle(const wxString& protocol,
                                         wxStreamProtocolType type) const
{
    if (type == wxSTREAM_FILEEXT)
        return FindExtension(protocol) != wxString::npos;
    else
        for (const wxChar *const *p = GetProtocols(type); *p; p++)
            if (protocol == *p)
                return true;

    return false;
}

// ----------------------------------------------------------------------------
// wxFilterClassFactory
// ----------------------------------------------------------------------------

IMPLEMENT_ABSTRACT_CLASS(wxFilterClassFactory, wxFilterClassFactoryBase)

wxFilterClassFactory *wxFilterClassFactory::sm_first = NULL;

void wxFilterClassFactory::Remove()
{
    if (m_next != this)
    {
        wxFilterClassFactory **pp = &sm_first;

        while (*pp != this)
            pp = &(*pp)->m_next;

        *pp = m_next;

        m_next = this;
    }
}

// ----------------------------------------------------------------------------
// wxBufferedInputStream
// ----------------------------------------------------------------------------

namespace
{

// helper function used for initializing the buffer used by
// wxBufferedInput/OutputStream: it simply returns the provided buffer if it's
// not NULL or creates a buffer of the given size otherwise
template <typename T>
wxStreamBuffer *
CreateBufferIfNeeded(T& stream, wxStreamBuffer *buffer, size_t bufsize = 1024)
{
    return buffer ? buffer : new wxStreamBuffer(bufsize, stream);
}

} // anonymous namespace

wxBufferedInputStream::wxBufferedInputStream(wxInputStream& stream,
                                             wxStreamBuffer *buffer)
                     : wxFilterInputStream(stream)
{
    m_i_streambuf = CreateBufferIfNeeded(*this, buffer);
}

wxBufferedInputStream::wxBufferedInputStream(wxInputStream& stream,
                                             size_t bufsize)
                     : wxFilterInputStream(stream)
{
    m_i_streambuf = CreateBufferIfNeeded(*this, NULL, bufsize);
}

wxBufferedInputStream::~wxBufferedInputStream()
{
    m_parent_i_stream->SeekI(-(wxFileOffset)m_i_streambuf->GetBytesLeft(),
                             wxFromCurrent);

    delete m_i_streambuf;
}

char wxBufferedInputStream::Peek()
{
    return m_i_streambuf->Peek();
}

wxInputStream& wxBufferedInputStream::Read(void *buf, size_t size)
{
    // reset the error flag
    Reset();

    // first read from the already cached data
    m_lastcount = GetWBack(buf, size);

    // do we have to read anything more?
    if ( m_lastcount < size )
    {
        size -= m_lastcount;
        buf = (char *)buf + m_lastcount;

        // the call to wxStreamBuffer::Read() below may reset our m_lastcount
        // (but it also may not do it if the buffer is associated to another
        // existing stream and wasn't created by us), so save it
        size_t countOld = m_lastcount;

        // the new count of the bytes read is the count of bytes read this time
        m_lastcount = m_i_streambuf->Read(buf, size);

        // plus those we had read before
        m_lastcount += countOld;
    }

    return *this;
}

wxFileOffset wxBufferedInputStream::SeekI(wxFileOffset pos, wxSeekMode mode)
{
    // RR: Look at wxInputStream for comments.

    if (m_lasterror==wxSTREAM_EOF)
        Reset();

    if (m_wback)
    {
        wxLogDebug( wxT("Seeking in stream which has data written back to it.") );

        free(m_wback);
        m_wback = NULL;
        m_wbacksize = 0;
        m_wbackcur = 0;
    }

    return m_i_streambuf->Seek(pos, mode);
}

wxFileOffset wxBufferedInputStream::TellI() const
{
    wxFileOffset pos = m_i_streambuf->Tell();

    if (pos != wxInvalidOffset)
        pos -= (m_wbacksize - m_wbackcur);

    return pos;
}

size_t wxBufferedInputStream::OnSysRead(void *buffer, size_t bufsize)
{
    return m_parent_i_stream->Read(buffer, bufsize).LastRead();
}

wxFileOffset wxBufferedInputStream::OnSysSeek(wxFileOffset seek, wxSeekMode mode)
{
    return m_parent_i_stream->SeekI(seek, mode);
}

wxFileOffset wxBufferedInputStream::OnSysTell() const
{
    return m_parent_i_stream->TellI();
}

void wxBufferedInputStream::SetInputStreamBuffer(wxStreamBuffer *buffer)
{
    wxCHECK_RET( buffer, wxT("wxBufferedInputStream needs buffer") );

    delete m_i_streambuf;
    m_i_streambuf = buffer;
}

// ----------------------------------------------------------------------------
// wxBufferedOutputStream
// ----------------------------------------------------------------------------

wxBufferedOutputStream::wxBufferedOutputStream(wxOutputStream& stream,
                                               wxStreamBuffer *buffer)
                      : wxFilterOutputStream(stream)
{
    m_o_streambuf = CreateBufferIfNeeded(*this, buffer);
}

wxBufferedOutputStream::wxBufferedOutputStream(wxOutputStream& stream,
                                               size_t bufsize)
                      : wxFilterOutputStream(stream)
{
    m_o_streambuf = CreateBufferIfNeeded(*this, NULL, bufsize);
}

wxBufferedOutputStream::~wxBufferedOutputStream()
{
    Sync();
    delete m_o_streambuf;
}

bool wxBufferedOutputStream::Close()
{
    Sync();
    return IsOk();
}


wxOutputStream& wxBufferedOutputStream::Write(const void *buffer, size_t size)
{
    m_lastcount = 0;
    m_o_streambuf->Write(buffer, size);
    return *this;
}

wxFileOffset wxBufferedOutputStream::SeekO(wxFileOffset pos, wxSeekMode mode)
{
    Sync();
    return m_o_streambuf->Seek(pos, mode);
}

wxFileOffset wxBufferedOutputStream::TellO() const
{
    return m_o_streambuf->Tell();
}

void wxBufferedOutputStream::Sync()
{
    m_o_streambuf->FlushBuffer();
    m_parent_o_stream->Sync();
}

size_t wxBufferedOutputStream::OnSysWrite(const void *buffer, size_t bufsize)
{
    return m_parent_o_stream->Write(buffer, bufsize).LastWrite();
}

wxFileOffset wxBufferedOutputStream::OnSysSeek(wxFileOffset seek, wxSeekMode mode)
{
    return m_parent_o_stream->SeekO(seek, mode);
}

wxFileOffset wxBufferedOutputStream::OnSysTell() const
{
    return m_parent_o_stream->TellO();
}

wxFileOffset wxBufferedOutputStream::GetLength() const
{
   return m_parent_o_stream->GetLength() + m_o_streambuf->GetIntPosition();
}

void wxBufferedOutputStream::SetOutputStreamBuffer(wxStreamBuffer *buffer)
{
    wxCHECK_RET( buffer, wxT("wxBufferedOutputStream needs buffer") );

    delete m_o_streambuf;
    m_o_streambuf = buffer;
}

// ---------------------------------------------------------------------------
// wxWrapperInputStream implementation
// ---------------------------------------------------------------------------

wxWrapperInputStream::wxWrapperInputStream()
{
    m_lasterror = wxSTREAM_READ_ERROR;
}

wxWrapperInputStream::wxWrapperInputStream(wxInputStream& stream)
    : wxFilterInputStream(stream)
{
    SynchronizeLastError();
}

wxWrapperInputStream::wxWrapperInputStream(wxInputStream *stream)
    : wxFilterInputStream(stream)
{
    if ( m_parent_i_stream )
        SynchronizeLastError();
    else
        m_lasterror = wxSTREAM_READ_ERROR;
}

void wxWrapperInputStream::InitParentStream(wxInputStream& stream)
{
    wxCHECK_RET( !m_parent_i_stream, "Can't init parent stream twice" );

    m_parent_i_stream = &stream;

    SynchronizeLastError();
}

void wxWrapperInputStream::InitParentStream(wxInputStream* stream)
{
    wxCHECK_RET( !m_parent_i_stream, "Can't init parent stream twice" );

    m_parent_i_stream = stream;

    if ( m_parent_i_stream )
    {
        m_owns = true;

        SynchronizeLastError();
    }
}

wxFileOffset wxWrapperInputStream::GetLength() const
{
    wxCHECK_MSG(m_parent_i_stream, wxInvalidOffset, "Stream not valid");

    wxON_BLOCK_EXIT_THIS0(wxWrapperInputStream::SynchronizeLastError);
    return m_parent_i_stream->GetLength();
}

bool wxWrapperInputStream::IsSeekable() const
{
    wxCHECK_MSG(m_parent_i_stream, false, "Stream not valid");
    return m_parent_i_stream->IsSeekable();
}

size_t wxWrapperInputStream::OnSysRead(void *buffer, size_t size)
{
    wxCHECK_MSG(m_parent_i_stream, false, "Stream not valid");

    wxON_BLOCK_EXIT_THIS0(wxWrapperInputStream::SynchronizeLastError);

    m_parent_i_stream->Read(buffer, size);
    return m_parent_i_stream->LastRead();
}

wxFileOffset wxWrapperInputStream::OnSysSeek(wxFileOffset pos, wxSeekMode mode)
{
    wxCHECK_MSG(IsSeekable(), false, "Stream not seekable");

    wxON_BLOCK_EXIT_THIS0(wxWrapperInputStream::SynchronizeLastError);
    return m_parent_i_stream->SeekI (pos, mode);
}

wxFileOffset wxWrapperInputStream::OnSysTell() const
{
    wxCHECK_MSG(m_parent_i_stream, false, "Stream not valid");

    wxON_BLOCK_EXIT_THIS0(wxWrapperInputStream::SynchronizeLastError);
    return m_parent_i_stream->TellI();
}

// ----------------------------------------------------------------------------
// Some IOManip function
// ----------------------------------------------------------------------------

wxOutputStream& wxEndL(wxOutputStream& stream)
{
    static const wxChar *eol = wxTextFile::GetEOL();

    return stream.Write(eol, wxStrlen(eol));
}

#endif // wxUSE_STREAMS