headers/private/storage/OffsetFile.h

   1 //----------------------------------------------------------------------
   2 //  This software is part of the OpenBeOS distribution and is covered
   3 //  by the MIT License.
   4 //---------------------------------------------------------------------
   5 /*!
   6         \file OffsetFile.h
   7         OffsetFile interface declaration.
   8 */
   9
  10 #ifndef _OFFSET_FILE_H
  11 #define _OFFSET_FILE_H
  12
  13 #include <DataIO.h>
  14 #include <File.h>
  15
  16 namespace BPrivate {
  17 namespace Storage {
  18
  19 /*!
  20         \class OffsetFile
  21         \brief Provides access to a file skipping a certain amount of bytes at
  22         the beginning.
  23
  24         This class implements the BPositionIO interface to provide access to the
  25         data of a file past a certain offset. This is very handy e.g. for dealing
  26         with resources, as they always reside at the end of a file, but may start
  27         at arbitrary offsets.
  28
  29         \author <a href='mailto:bonefish@users.sf.net'>Ingo Weinhold</a>
  30
  31         \version 0.0.0
  32 */
  33 class OffsetFile : public BPositionIO {
  34 public:
  35         OffsetFile();
  36         OffsetFile(BFile *file, off_t offset);
  37         virtual ~OffsetFile();
  38
  39         status_t SetTo(BFile *file, off_t offset);
  40         void Unset();
  41         status_t InitCheck() const;
  42
  43         BFile *File() const;
  44
  45         ssize_t ReadAt(off_t pos, void *buffer, size_t size);
  46         ssize_t WriteAt(off_t pos, const void *buffer,
  47                                                                 size_t size);
  48         off_t Seek(off_t position, uint32 seekMode);
  49         off_t Position() const;
  50
  51         status_t SetSize(off_t size);
  52         status_t GetSize(off_t *size) const;
  53
  54         off_t Offset() const;
  55
  56 private:
  57         BFile*                          fFile;
  58         off_t                           fOffset;
  59         off_t                           fCurrentPosition;
  60 };
  61
  62 };      // namespace Storage
  63 };      // namespace BPrivate
  64
  65 #endif  // _OFFSET_FILE_H
  66
  67