JeVois  1.2
JeVois Smart Embedded Machine Vision Toolkit
VideoBuf.H
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2 //
3 // JeVois Smart Embedded Machine Vision Toolkit - Copyright (C) 2016 by Laurent Itti, the University of Southern
4 // California (USC), and iLab at USC. See http://iLab.usc.edu and http://jevois.org for information about this project.
5 //
6 // This file is part of the JeVois Smart Embedded Machine Vision Toolkit. This program is free software; you can
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15 // ///////////////////////////////////////////////////////////////////////////////////////////////////////////////////
16 /*! \file */
17 
18 #pragma once
19 
20 #include <cstddef>
21 
22 namespace jevois
23 {
24  //! A V4L2 video buffer, to be held in a shared_ptr
25  /*! Requests an MMAP'ed memory area from the given file descriptor at construction, and unmaps it at
26  destruction. VideoBuf is used to pass MMAP'ed video buffers from Camera and Gadget drivers to application code,
27  via RawImage. The actual memory allocation is performed by the kernel driver. Hence, VideoBuf pixel arrays cannot
28  be moved from one memory location to another. \ingroup core */
29  class VideoBuf
30  {
31  public:
32  //! Construct and allocate MMAP'd memory
33  /*! Mostly for debugging purposes (supporting VideoDisplay), if fd is -1 then we perform a regular memory
34  allocation instead of mmap. */
35  VideoBuf(int const fd, size_t const length, unsigned int offset);
36 
37  //! Destructor unmaps the memory
38  ~VideoBuf();
39 
40  //! Sync the data
41  /*! This may be useful in some cases to avoid cache coherency issues between DMA-capable driver and CPU. */
42  void sync();
43 
44  //! Get a pointer to the buffer data
45  void * data() const;
46 
47  //! Get the allocated memory length
48  size_t length() const;
49 
50  //! Set the number of bytes used, eg, for MJPEG images that application code compressed into the buffer
51  void setBytesUsed(size_t n);
52 
53  //! Get the number of bytes used, valid only for MJPEG images
54  size_t bytesUsed() const;
55 
56  private:
57  int const itsFd;
58  size_t const itsLength;
59  size_t itsBytesUsed;
60  void * itsAddr;
61  };
62 
63 } // namespace jevois
void sync()
Sync the data.
Definition: VideoBuf.C:77
A V4L2 video buffer, to be held in a shared_ptr.
Definition: VideoBuf.H:29
~VideoBuf()
Destructor unmaps the memory.
Definition: VideoBuf.C:47
VideoBuf(int const fd, size_t const length, unsigned int offset)
Construct and allocate MMAP'd memory.
Definition: VideoBuf.C:25
void setBytesUsed(size_t n)
Set the number of bytes used, eg, for MJPEG images that application code compressed into the buffer...
Definition: VideoBuf.C:109
size_t length() const
Get the allocated memory length.
Definition: VideoBuf.C:103
void * data() const
Get a pointer to the buffer data.
Definition: VideoBuf.C:97
size_t bytesUsed() const
Get the number of bytes used, valid only for MJPEG images.
Definition: VideoBuf.C:115