include/wx/private/fileback.h

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