include/wx/fileback.h

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        include/wx/fileback.h
   3 // Purpose:     Back an input stream with memory or a file
   4 // Author:      Mike Wetherell
   5 // RCS-ID:      $Id$
   6 // Copyright:   (c) 2006 Mike Wetherell
   7 // Licence:     wxWindows licence
   8 /////////////////////////////////////////////////////////////////////////////
   9
  10 #ifndef _WX_FILEBACK_H__
  11 #define _WX_FILEBACK_H__
  12
  13 #include "wx/defs.h"
  14
  15 #if wxUSE_BACKINGFILE
  16
  17 #include "wx/stream.h"
  18
  19 // ----------------------------------------------------------------------------
  20 // Backs an input stream with memory or a file to make it seekable.
  21 //
  22 // One or more wxBackedInputStreams can be used to read it's data. The data is
  23 // reference counted, so stays alive until the last wxBackingFile or
  24 // wxBackedInputStream using it is destroyed.
  25 // ----------------------------------------------------------------------------
  26
  27 class WXDLLIMPEXP_BASE wxBackingFile
  28 {
  29 public:
  30     enum { DefaultBufSize = 16384 };
  31
  32     // Takes ownership of stream. If the stream is smaller than bufsize, the
  33     // backing file is never created and the backing is done with memory.
  34     wxBackingFile(wxInputStream *stream,
  35                   size_t bufsize = DefaultBufSize,
  36                   const wxString& prefix = _T("wxbf"));
  37
  38     wxBackingFile() : m_impl(NULL) { }
  39     ~wxBackingFile();
  40
  41     wxBackingFile(const wxBackingFile& backer);
  42     wxBackingFile& operator=(const wxBackingFile& backer);
  43
  44     operator bool() const { return m_impl != NULL; }
  45
  46 private:
  47     class wxBackingFileImpl *m_impl;
  48     friend class wxBackedInputStream;
  49 };
  50
  51 // ----------------------------------------------------------------------------
  52 // An input stream to read from a wxBackingFile.
  53 // ----------------------------------------------------------------------------
  54
  55 class WXDLLIMPEXP_BASE wxBackedInputStream : public wxInputStream
  56 {
  57 public:
  58     wxBackedInputStream(const wxBackingFile& backer);
  59
  60     // If the length of the backer's parent stream is unknown then GetLength()
  61     // returns wxInvalidOffset until the parent has been read to the end.
  62     wxFileOffset GetLength() const;
  63
  64     // Returns the length, reading the parent stream to the end if necessary.
  65     wxFileOffset FindLength() const;
  66
  67     bool IsSeekable() const { return true; }
  68
  69 protected:
  70     size_t OnSysRead(void *buffer, size_t size);
  71     wxFileOffset OnSysSeek(wxFileOffset pos, wxSeekMode mode);
  72     wxFileOffset OnSysTell() const;
  73
  74 private:
  75     wxBackingFile m_backer;
  76     wxFileOffset m_pos;
  77
  78     DECLARE_NO_COPY_CLASS(wxBackedInputStream)
  79 };
  80
  81 #endif // wxUSE_BACKINGFILE
  82
  83 #endif // _WX_FILEBACK_H__