initial commit

Signed-off-by: Peter Siegmund <mars3142@noreply.mars3142.dev>

libs/wxWidgets-3.3.1/include/wx/stream.h

@@ -0,0 +1,733 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        wx/stream.h
+// Purpose:     stream classes
+// Author:      Guilhem Lavaux, Guillermo Rodriguez Garcia, Vadim Zeitlin
+// Created:     11/07/98
+// Copyright:   (c) Guilhem Lavaux
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#ifndef _WX_WXSTREAM_H__
+#define _WX_WXSTREAM_H__
+
+#include "wx/defs.h"
+
+#if wxUSE_STREAMS
+
+#include "wx/object.h"
+#include "wx/string.h"
+#include "wx/filefn.h"  // for wxFileOffset, wxInvalidOffset and wxSeekMode
+
+class WXDLLIMPEXP_FWD_BASE wxStreamBase;
+class WXDLLIMPEXP_FWD_BASE wxInputStream;
+class WXDLLIMPEXP_FWD_BASE wxOutputStream;
+
+typedef wxInputStream& (*__wxInputManip)(wxInputStream&);
+typedef wxOutputStream& (*__wxOutputManip)(wxOutputStream&);
+
+WXDLLIMPEXP_BASE wxOutputStream& wxEndL(wxOutputStream& o_stream);
+
+// ----------------------------------------------------------------------------
+// constants
+// ----------------------------------------------------------------------------
+
+enum wxStreamError
+{
+    wxSTREAM_NO_ERROR = 0,      // stream is in good state
+    wxSTREAM_EOF,               // EOF reached in Read() or similar
+    wxSTREAM_WRITE_ERROR,       // generic write error
+    wxSTREAM_READ_ERROR         // generic read error
+};
+
+const int wxEOF = -1;
+
+// ============================================================================
+// base stream classes: wxInputStream and wxOutputStream
+// ============================================================================
+
+// ---------------------------------------------------------------------------
+// wxStreamBase: common (but non virtual!) base for all stream classes
+// ---------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxStreamBase : public wxObject
+{
+public:
+    wxStreamBase();
+    virtual ~wxStreamBase();
+
+    // error testing
+    wxStreamError GetLastError() const { return m_lasterror; }
+    virtual bool IsOk() const { return GetLastError() == wxSTREAM_NO_ERROR; }
+    bool operator!() const { return !IsOk(); }
+
+    // reset the stream state
+    void Reset(wxStreamError error = wxSTREAM_NO_ERROR) { m_lasterror = error; }
+
+    // this doesn't make sense for all streams, always test its return value
+    virtual size_t GetSize() const;
+    virtual wxFileOffset GetLength() const { return wxInvalidOffset; }
+
+    // returns true if the streams supports seeking to arbitrary offsets
+    virtual bool IsSeekable() const { return false; }
+
+protected:
+    virtual wxFileOffset OnSysSeek(wxFileOffset seek, wxSeekMode mode);
+    virtual wxFileOffset OnSysTell() const;
+
+    size_t m_lastcount;
+    wxStreamError m_lasterror;
+
+    friend class wxStreamBuffer;
+
+    wxDECLARE_ABSTRACT_CLASS(wxStreamBase);
+    wxDECLARE_NO_COPY_CLASS(wxStreamBase);
+};
+
+// ----------------------------------------------------------------------------
+// wxInputStream: base class for the input streams
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxInputStream : public wxStreamBase
+{
+public:
+    // ctor and dtor, nothing exciting
+    wxInputStream();
+    virtual ~wxInputStream();
+
+
+    // IO functions
+    // ------------
+
+    // return a character from the stream without removing it, i.e. it will
+    // still be returned by the next call to GetC()
+    //
+    // blocks until something appears in the stream if necessary, if nothing
+    // ever does (i.e. EOF) LastRead() will return 0 (and the return value is
+    // undefined), otherwise 1
+    virtual char Peek();
+
+    // return one byte from the stream, blocking until it appears if
+    // necessary
+    //
+    // on success returns a value between 0 - 255, or wxEOF on EOF or error.
+    int GetC();
+
+    // read at most the given number of bytes from the stream
+    //
+    // there are 2 possible situations here: either there is nothing at all in
+    // the stream right now in which case Read() blocks until something appears
+    // (use CanRead() to avoid this) or there is already some data available in
+    // the stream and then Read() doesn't block but returns just the data it
+    // can read without waiting for more
+    //
+    // in any case, if there are not enough bytes in the stream right now,
+    // LastRead() value will be less than size but greater than 0. If it is 0,
+    // it means that EOF has been reached.
+    virtual wxInputStream& Read(void *buffer, size_t size);
+
+    // Read exactly the given number of bytes, unlike Read(), which may read
+    // less than the requested amount of data without returning an error, this
+    // method either reads all the data or returns false.
+    bool ReadAll(void *buffer, size_t size);
+
+    // copy the entire contents of this stream into streamOut, stopping only
+    // when EOF is reached or an error occurs
+    wxInputStream& Read(wxOutputStream& streamOut);
+
+
+    // status functions
+    // ----------------
+
+    // returns the number of bytes read by the last call to Read(), GetC() or
+    // Peek()
+    //
+    // this should be used to discover whether that call succeeded in reading
+    // all the requested data or not
+    virtual size_t LastRead() const { return wxStreamBase::m_lastcount; }
+
+    // returns true if some data is available in the stream right now, so that
+    // calling Read() wouldn't block
+    virtual bool CanRead() const;
+
+    // is the stream at EOF?
+    //
+    // note that this cannot be really implemented for all streams and
+    // CanRead() is more reliable than Eof()
+    virtual bool Eof() const;
+
+
+    // write back buffer
+    // -----------------
+
+    // put back the specified number of bytes into the stream, they will be
+    // fetched by the next call to the read functions
+    //
+    // returns the number of bytes really stuffed back
+    size_t Ungetch(const void *buffer, size_t size);
+
+    // put back the specified character in the stream
+    //
+    // returns true if ok, false on error
+    bool Ungetch(char c);
+
+
+    // position functions
+    // ------------------
+
+    // move the stream pointer to the given position (if the stream supports
+    // it)
+    //
+    // returns wxInvalidOffset on error
+    virtual wxFileOffset SeekI(wxFileOffset pos, wxSeekMode mode = wxFromStart);
+
+    // return the current position of the stream pointer or wxInvalidOffset
+    virtual wxFileOffset TellI() const;
+
+
+    // stream-like operators
+    // ---------------------
+
+    wxInputStream& operator>>(wxOutputStream& out) { return Read(out); }
+    wxInputStream& operator>>(__wxInputManip func) { return func(*this); }
+
+protected:
+    // do read up to size bytes of data into the provided buffer
+    //
+    // this method should return 0 if EOF has been reached or an error occurred
+    // (m_lasterror should be set accordingly as well) or the number of bytes
+    // read
+    virtual size_t OnSysRead(void *buffer, size_t size) = 0;
+
+    // write-back buffer support
+    // -------------------------
+
+    // return the pointer to a buffer big enough to hold sizeNeeded bytes
+    char *AllocSpaceWBack(size_t sizeNeeded);
+
+    // read up to size data from the write back buffer, return the number of
+    // bytes read
+    size_t GetWBack(void *buf, size_t size);
+
+    // write back buffer or nullptr if none
+    char *m_wback;
+
+    // the size of the buffer
+    size_t m_wbacksize;
+
+    // the current position in the buffer
+    size_t m_wbackcur;
+
+    friend class wxStreamBuffer;
+
+    wxDECLARE_ABSTRACT_CLASS(wxInputStream);
+    wxDECLARE_NO_COPY_CLASS(wxInputStream);
+};
+
+// ----------------------------------------------------------------------------
+// wxOutputStream: base for the output streams
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxOutputStream : public wxStreamBase
+{
+public:
+    wxOutputStream();
+    virtual ~wxOutputStream();
+
+    void PutC(char c);
+    virtual wxOutputStream& Write(const void *buffer, size_t size);
+
+    // This is ReadAll() equivalent for Write(): it either writes exactly the
+    // given number of bytes or returns false, unlike Write() which can write
+    // less data than requested but still return without error.
+    bool WriteAll(const void *buffer, size_t size);
+
+    wxOutputStream& Write(wxInputStream& stream_in);
+
+    virtual wxFileOffset SeekO(wxFileOffset pos, wxSeekMode mode = wxFromStart);
+    virtual wxFileOffset TellO() const;
+
+    virtual size_t LastWrite() const { return wxStreamBase::m_lastcount; }
+
+    virtual void Sync();
+    virtual bool Close() { return true; }
+
+    wxOutputStream& operator<<(wxInputStream& out) { return Write(out); }
+    wxOutputStream& operator<<( __wxOutputManip func) { return func(*this); }
+
+protected:
+    // to be implemented in the derived classes (it should have been pure
+    // virtual)
+    virtual size_t OnSysWrite(const void *buffer, size_t bufsize);
+
+    friend class wxStreamBuffer;
+
+    wxDECLARE_ABSTRACT_CLASS(wxOutputStream);
+    wxDECLARE_NO_COPY_CLASS(wxOutputStream);
+};
+
+// ============================================================================
+// helper stream classes
+// ============================================================================
+
+// ---------------------------------------------------------------------------
+// A stream for measuring streamed output
+// ---------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxCountingOutputStream : public wxOutputStream
+{
+public:
+    wxCountingOutputStream();
+
+    virtual wxFileOffset GetLength() const override;
+    bool Ok() const { return IsOk(); }
+    virtual bool IsOk() const override { return true; }
+
+protected:
+    virtual size_t OnSysWrite(const void *buffer, size_t size) override;
+    virtual wxFileOffset OnSysSeek(wxFileOffset pos, wxSeekMode mode) override;
+    virtual wxFileOffset OnSysTell() const override;
+
+    size_t m_currentPos,
+           m_lastPos;
+
+    wxDECLARE_DYNAMIC_CLASS(wxCountingOutputStream);
+    wxDECLARE_NO_COPY_CLASS(wxCountingOutputStream);
+};
+
+// ---------------------------------------------------------------------------
+// "Filter" streams
+// ---------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxFilterInputStream : public wxInputStream
+{
+public:
+    wxFilterInputStream();
+    wxFilterInputStream(wxInputStream& stream);
+    wxFilterInputStream(wxInputStream *stream);
+    virtual ~wxFilterInputStream();
+
+    virtual char Peek() override { return m_parent_i_stream->Peek(); }
+
+    virtual wxFileOffset GetLength() const override { return m_parent_i_stream->GetLength(); }
+
+    wxInputStream *GetFilterInputStream() const { return m_parent_i_stream; }
+
+protected:
+    wxInputStream *m_parent_i_stream;
+    bool m_owns;
+
+    wxDECLARE_ABSTRACT_CLASS(wxFilterInputStream);
+    wxDECLARE_NO_COPY_CLASS(wxFilterInputStream);
+};
+
+class WXDLLIMPEXP_BASE wxFilterOutputStream : public wxOutputStream
+{
+public:
+    wxFilterOutputStream();
+    wxFilterOutputStream(wxOutputStream& stream);
+    wxFilterOutputStream(wxOutputStream *stream);
+    virtual ~wxFilterOutputStream();
+
+    virtual wxFileOffset GetLength() const override { return m_parent_o_stream->GetLength(); }
+
+    wxOutputStream *GetFilterOutputStream() const { return m_parent_o_stream; }
+
+    bool Close() override;
+
+protected:
+    wxOutputStream *m_parent_o_stream;
+    bool m_owns;
+
+    wxDECLARE_ABSTRACT_CLASS(wxFilterOutputStream);
+    wxDECLARE_NO_COPY_CLASS(wxFilterOutputStream);
+};
+
+enum wxStreamProtocolType
+{
+    wxSTREAM_PROTOCOL,  // wxFileSystem protocol (should be only one)
+    wxSTREAM_MIMETYPE,  // MIME types the stream handles
+    wxSTREAM_ENCODING,  // The HTTP Content-Encodings the stream handles
+    wxSTREAM_FILEEXT    // File extensions the stream handles
+};
+
+void WXDLLIMPEXP_BASE wxUseFilterClasses();
+
+class WXDLLIMPEXP_BASE wxFilterClassFactoryBase : public wxObject
+{
+public:
+    virtual ~wxFilterClassFactoryBase() = default;
+
+    wxString GetProtocol() const { return wxString(*GetProtocols()); }
+    wxString PopExtension(const wxString& location) const;
+
+    virtual const wxChar * const *GetProtocols(wxStreamProtocolType type
+                                               = wxSTREAM_PROTOCOL) const = 0;
+
+    bool CanHandle(const wxString& protocol,
+                   wxStreamProtocolType type
+                   = wxSTREAM_PROTOCOL) const;
+
+protected:
+    wxString::size_type FindExtension(const wxString& location) const;
+
+    wxDECLARE_ABSTRACT_CLASS(wxFilterClassFactoryBase);
+};
+
+class WXDLLIMPEXP_BASE wxFilterClassFactory : public wxFilterClassFactoryBase
+{
+public:
+    virtual ~wxFilterClassFactory() = default;
+
+    virtual wxFilterInputStream  *NewStream(wxInputStream& stream)  const = 0;
+    virtual wxFilterOutputStream *NewStream(wxOutputStream& stream) const = 0;
+    virtual wxFilterInputStream  *NewStream(wxInputStream *stream)  const = 0;
+    virtual wxFilterOutputStream *NewStream(wxOutputStream *stream) const = 0;
+
+    static const wxFilterClassFactory *Find(const wxString& protocol,
+                                            wxStreamProtocolType type
+                                            = wxSTREAM_PROTOCOL);
+
+    static const wxFilterClassFactory *GetFirst();
+    const wxFilterClassFactory *GetNext() const { return m_next; }
+
+    void PushFront() { Remove(); m_next = sm_first; sm_first = this; }
+    void Remove();
+
+protected:
+    wxFilterClassFactory() : m_next(this) { }
+
+    wxFilterClassFactory& operator=(const wxFilterClassFactory&)
+        { return *this; }
+
+private:
+    static wxFilterClassFactory *sm_first;
+    wxFilterClassFactory *m_next;
+
+    wxDECLARE_ABSTRACT_CLASS(wxFilterClassFactory);
+};
+
+// ============================================================================
+// buffered streams
+// ============================================================================
+
+// ---------------------------------------------------------------------------
+// Stream buffer: this class can be derived from and passed to
+// wxBufferedStreams to implement custom buffering
+// ---------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxStreamBuffer
+{
+public:
+    // suppress Xcode 11 warning about shadowing global read() symbol
+    wxCLANG_WARNING_SUPPRESS(shadow)
+
+    enum BufMode
+    {
+        read,
+        write,
+        read_write
+    };
+
+    wxCLANG_WARNING_RESTORE(shadow)
+
+    wxStreamBuffer(wxStreamBase& stream, BufMode mode)
+    {
+        InitWithStream(stream, mode);
+    }
+
+    wxStreamBuffer(size_t bufsize, wxInputStream& stream)
+    {
+        InitWithStream(stream, read);
+        SetBufferIO(bufsize);
+    }
+
+    wxStreamBuffer(size_t bufsize, wxOutputStream& stream)
+    {
+        InitWithStream(stream, write);
+        SetBufferIO(bufsize);
+    }
+
+    wxStreamBuffer(const wxStreamBuffer& buf);
+    virtual ~wxStreamBuffer();
+
+    // Filtered IO
+    virtual size_t Read(void *buffer, size_t size);
+    size_t Read(wxStreamBuffer *buf);
+    virtual size_t Write(const void *buffer, size_t size);
+    size_t Write(wxStreamBuffer *buf);
+
+    virtual char Peek();
+    virtual char GetChar();
+    virtual void PutChar(char c);
+    virtual wxFileOffset Tell() const;
+    virtual wxFileOffset Seek(wxFileOffset pos, wxSeekMode mode);
+
+    // Buffer control
+    void ResetBuffer();
+    void Truncate();
+
+    // NB: the buffer must always be allocated with malloc() if takeOwn is
+    //     true as it will be deallocated by free()
+    void SetBufferIO(void *start, void *end, bool takeOwnership = false);
+    void SetBufferIO(void *start, size_t len, bool takeOwnership = false);
+    void SetBufferIO(size_t bufsize);
+    void *GetBufferStart() const { return m_buffer_start; }
+    void *GetBufferEnd() const { return m_buffer_end; }
+    void *GetBufferPos() const { return m_buffer_pos; }
+    size_t GetBufferSize() const { return m_buffer_end - m_buffer_start; }
+    size_t GetIntPosition() const { return m_buffer_pos - m_buffer_start; }
+    void SetIntPosition(size_t pos) { m_buffer_pos = m_buffer_start + pos; }
+    size_t GetLastAccess() const { return m_buffer_end - m_buffer_start; }
+    size_t GetBytesLeft() const { return m_buffer_end - m_buffer_pos; }
+
+    void Fixed(bool fixed) { m_fixed = fixed; }
+    void Flushable(bool f) { m_flushable = f; }
+
+    bool FlushBuffer();
+    bool FillBuffer();
+    size_t GetDataLeft();
+
+    // misc accessors
+    wxStreamBase *GetStream() const { return m_stream; }
+    bool HasBuffer() const { return m_buffer_start != m_buffer_end; }
+
+    bool IsFixed() const { return m_fixed; }
+    bool IsFlushable() const { return m_flushable; }
+
+    // only for input/output buffers respectively, returns nullptr otherwise
+    wxInputStream *GetInputStream() const;
+    wxOutputStream *GetOutputStream() const;
+
+    // this constructs a dummy wxStreamBuffer, used by (and exists for)
+    // wxMemoryStreams only, don't use!
+    wxStreamBuffer(BufMode mode);
+
+protected:
+    void GetFromBuffer(void *buffer, size_t size);
+    void PutToBuffer(const void *buffer, size_t size);
+
+    // set the last error to the specified value if we didn't have it before
+    void SetError(wxStreamError err);
+
+    // common part of several ctors
+    void Init();
+
+    // common part of ctors taking wxStreamBase parameter
+    void InitWithStream(wxStreamBase& stream, BufMode mode);
+
+    // init buffer variables to be empty
+    void InitBuffer();
+
+    // free the buffer (always safe to call)
+    void FreeBuffer();
+
+    // the buffer itself: the pointers to its start and end and the current
+    // position in the buffer
+    char *m_buffer_start,
+         *m_buffer_end,
+         *m_buffer_pos;
+
+    // the stream we're associated with
+    wxStreamBase *m_stream;
+
+    // its mode
+    BufMode m_mode;
+
+    // flags
+    bool m_destroybuf,      // deallocate buffer?
+         m_fixed,
+         m_flushable;
+
+
+    wxDECLARE_NO_ASSIGN_CLASS(wxStreamBuffer);
+};
+
+// ---------------------------------------------------------------------------
+// wxBufferedInputStream
+// ---------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxBufferedInputStream : public wxFilterInputStream
+{
+public:
+    // create a buffered stream on top of the specified low-level stream
+    //
+    // if a non null buffer is given to the stream, it will be deleted by it,
+    // otherwise a default 1KB buffer will be used
+    wxBufferedInputStream(wxInputStream& stream,
+                          wxStreamBuffer *buffer = nullptr);
+
+    // ctor allowing to specify the buffer size, it's just a more convenient
+    // alternative to creating wxStreamBuffer, calling its SetBufferIO(bufsize)
+    // and using the ctor above
+    wxBufferedInputStream(wxInputStream& stream, size_t bufsize);
+
+
+    virtual ~wxBufferedInputStream();
+
+    virtual char Peek() override;
+    virtual wxInputStream& Read(void *buffer, size_t size) override;
+
+    // Position functions
+    virtual wxFileOffset SeekI(wxFileOffset pos, wxSeekMode mode = wxFromStart) override;
+    virtual wxFileOffset TellI() const override;
+    virtual bool IsSeekable() const override { return m_parent_i_stream->IsSeekable(); }
+
+    // the buffer given to the stream will be deleted by it
+    void SetInputStreamBuffer(wxStreamBuffer *buffer);
+    wxStreamBuffer *GetInputStreamBuffer() const { return m_i_streambuf; }
+
+protected:
+    virtual size_t OnSysRead(void *buffer, size_t bufsize) override;
+    virtual wxFileOffset OnSysSeek(wxFileOffset seek, wxSeekMode mode) override;
+    virtual wxFileOffset OnSysTell() const override;
+
+    wxStreamBuffer *m_i_streambuf;
+
+    wxDECLARE_NO_COPY_CLASS(wxBufferedInputStream);
+};
+
+// ----------------------------------------------------------------------------
+// wxBufferedOutputStream
+// ----------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxBufferedOutputStream : public wxFilterOutputStream
+{
+public:
+    // create a buffered stream on top of the specified low-level stream
+    //
+    // if a non null buffer is given to the stream, it will be deleted by it,
+    // otherwise a default 1KB buffer will be used
+    wxBufferedOutputStream(wxOutputStream& stream,
+                           wxStreamBuffer *buffer = nullptr);
+
+    // ctor allowing to specify the buffer size, it's just a more convenient
+    // alternative to creating wxStreamBuffer, calling its SetBufferIO(bufsize)
+    // and using the ctor above
+    wxBufferedOutputStream(wxOutputStream& stream, size_t bufsize);
+
+    virtual ~wxBufferedOutputStream();
+
+    virtual wxOutputStream& Write(const void *buffer, size_t size) override;
+
+    // Position functions
+    virtual wxFileOffset SeekO(wxFileOffset pos, wxSeekMode mode = wxFromStart) override;
+    virtual wxFileOffset TellO() const override;
+    virtual bool IsSeekable() const override { return m_parent_o_stream->IsSeekable(); }
+
+    void Sync() override;
+    bool Close() override;
+
+    virtual wxFileOffset GetLength() const override;
+
+    // the buffer given to the stream will be deleted by it
+    void SetOutputStreamBuffer(wxStreamBuffer *buffer);
+    wxStreamBuffer *GetOutputStreamBuffer() const { return m_o_streambuf; }
+
+protected:
+    virtual size_t OnSysWrite(const void *buffer, size_t bufsize) override;
+    virtual wxFileOffset OnSysSeek(wxFileOffset seek, wxSeekMode mode) override;
+    virtual wxFileOffset OnSysTell() const override;
+
+    wxStreamBuffer *m_o_streambuf;
+
+    wxDECLARE_NO_COPY_CLASS(wxBufferedOutputStream);
+};
+
+// ---------------------------------------------------------------------------
+// wxWrapperInputStream: forwards all IO to another stream.
+// ---------------------------------------------------------------------------
+
+class WXDLLIMPEXP_BASE wxWrapperInputStream : public wxFilterInputStream
+{
+public:
+    // Constructor fully initializing the stream. The overload taking pointer
+    // takes ownership of the parent stream, the one taking reference does not.
+    //
+    // Notice that this class also has a default ctor but it's protected as the
+    // derived class is supposed to take care of calling InitParentStream() if
+    // it's used.
+    wxWrapperInputStream(wxInputStream& stream);
+    wxWrapperInputStream(wxInputStream* stream);
+
+    // Override the base class methods to forward to the wrapped stream.
+    virtual wxFileOffset GetLength() const override;
+    virtual bool IsSeekable() const override;
+
+protected:
+    virtual size_t OnSysRead(void *buffer, size_t size) override;
+    virtual wxFileOffset OnSysSeek(wxFileOffset pos, wxSeekMode mode) override;
+    virtual wxFileOffset OnSysTell() const override;
+
+    // Ensure that our own last error is the same as that of the real stream.
+    //
+    // This method is const because the error must be updated even from const
+    // methods (in other words, it really should have been mutable in the first
+    // place).
+    void SynchronizeLastError() const
+    {
+        const_cast<wxWrapperInputStream*>(this)->
+            Reset(m_parent_i_stream->GetLastError());
+    }
+
+    // Default constructor, use InitParentStream() later.
+    wxWrapperInputStream();
+
+    // Set up the wrapped stream for an object initialized using the default
+    // constructor. The ownership logic is the same as above.
+    void InitParentStream(wxInputStream& stream);
+    void InitParentStream(wxInputStream* stream);
+
+    wxDECLARE_NO_COPY_CLASS(wxWrapperInputStream);
+};
+
+// ----------------------------------------------------------------------------
+// wxPeekInputStream(): read some data from a stream and then rewind it back
+// ----------------------------------------------------------------------------
+
+// This semi-private class is used in wx code to read some data, using the
+// provided method of the class T, from a stream if it's seekable and then
+// rewind it back.
+class wxInputStreamPeeker
+{
+public:
+    explicit wxInputStreamPeeker(wxInputStream& stream)
+        : m_stream(stream),
+          m_ofsOrig(stream.IsSeekable() ? stream.TellI() : wxInvalidOffset)
+    {
+    }
+
+    // Call the given function if the stream is seekable, otherwise return 0.
+    template <typename R, typename T>
+    R CallIfCanSeek(R (T::*func)(wxInputStream&), T* obj)
+    {
+        return RewindAndReturn(CanSeek() ? (obj->*func)(m_stream) : R(0));
+    }
+
+    // Overload for const methods.
+    template <typename R, typename T>
+    R CallIfCanSeek(R (T::*func)(wxInputStream&) const, const T* obj)
+    {
+        return RewindAndReturn(CanSeek() ? (obj->*func)(m_stream) : R(0));
+    }
+
+private:
+    bool CanSeek() const { return m_ofsOrig != wxInvalidOffset; }
+
+    template <typename R>
+    R RewindAndReturn(R retval)
+    {
+        if ( CanSeek() && m_stream.SeekI(m_ofsOrig) == wxInvalidOffset )
+            return R(0);
+
+        return retval;
+    }
+
+    wxInputStream& m_stream;
+    const wxFileOffset m_ofsOrig;
+
+    wxDECLARE_NO_COPY_CLASS(wxInputStreamPeeker);
+};
+
+#endif // wxUSE_STREAMS
+
+#endif // _WX_WXSTREAM_H__