Disk ARchive  2.6.8
Full featured and portable backup and archiving tool
null_file.hpp
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2 // dar - disk archive - a backup/restoration program
3 // Copyright (C) 2002-2020 Denis Corbin
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21 
27 
28 #ifndef NULL_FILE_HPP
29 #define NULL_FILE_HPP
30 
31 #include "../my_config.h"
32 #include "generic_file.hpp"
33 #include "thread_cancellation.hpp"
34 
35 namespace libdar
36 {
37 
40 
42 
48 
50  {
51  public :
52  null_file(gf_mode m) : generic_file(m) { set_offset(0); };
53  null_file(const null_file & ref) = default;
54  null_file(null_file && ref) noexcept = default;
55  null_file & operator = (const null_file & ref) = default;
56  null_file & operator = (null_file && ref) noexcept = default;
57  ~null_file() = default;
58 
59  virtual bool skippable(skippability direction, const infinint & amount) override { return true; };
60  virtual bool skip(const infinint &pos) override { set_offset(pos); return true; };
61  virtual bool skip_to_eof() override { offset = max_offset; return true; };
62  virtual bool skip_relative(signed int x) override { return set_rel_offset(x); };
63  virtual infinint get_position() const override { return offset; };
64 
65  protected :
66  virtual void inherited_read_ahead(const infinint & amount) override {};
67 
68  virtual U_I inherited_read(char *a, U_I size) override
69  {
70 #ifdef MUTEX_WORKS
72 #endif
73  return 0;
74  };
75 
76  virtual void inherited_write(const char *a, U_I siz) override
77  {
78 #ifdef MUTEX_WORKS
80 #endif
81  set_offset(offset + siz);
82  };
83 
84  virtual void inherited_sync_write() override {};
85  virtual void inherited_flush_read() override {};
86  virtual void inherited_terminate() override {};
87 
88  private:
89  infinint offset;
90  infinint max_offset;
91 
92  void set_offset(const infinint & x)
93  {
94  if(x > max_offset)
95  max_offset = x;
96  offset = x;
97  }
98 
99  bool set_rel_offset(signed int x)
100  {
101  if(x >= 0)
102  {
103  set_offset(offset + x);
104  return true;
105  }
106  else // x < 0
107  {
108  infinint tmp = -x;
109  if(tmp > offset)
110  {
111  offset = 0;
112  return false;
113  }
114  else
115  {
116  offset -= tmp;
117  return true;
118  }
119  }
120  }
121 
122  };
123 
125 
126 } // end of namespace
127 
128 #endif
libdar::generic_file::generic_file
generic_file(gf_mode m)
main constructor
Definition: generic_file.hpp:80
libdar::thread_cancellation::check_self_cancellation
void check_self_cancellation() const
Checkpoint test : whether the current libdar call must abort or not.
libdar::thread_cancellation
class to be used as parent to provide checkpoints to inherited classes
Definition: thread_cancellation.hpp:68
libdar::gf_mode
gf_mode
generic_file openning modes
Definition: gf_mode.hpp:43
libdar::infinint
the arbitrary large positive integer class
Definition: real_infinint.hpp:61
libdar::null_file::inherited_flush_read
virtual void inherited_flush_read() override
reset internal engine, flush caches in order to read the data at current position
Definition: null_file.hpp:85
libdar::null_file::inherited_terminate
virtual void inherited_terminate() override
destructor-like call, except that it is allowed to throw exceptions
Definition: null_file.hpp:86
libdar::null_file::skippable
virtual bool skippable(skippability direction, const infinint &amount) override
whether the implementation is able to skip
Definition: null_file.hpp:59
libdar::null_file::inherited_read_ahead
virtual void inherited_read_ahead(const infinint &amount) override
tells the object that several calls to read() will follow to probably obtain at least the given amoun...
Definition: null_file.hpp:66
libdar::null_file::skip_to_eof
virtual bool skip_to_eof() override
skip to the end of file
Definition: null_file.hpp:61
thread_cancellation.hpp
to be able to cancel libdar operation while running in a given thread.
generic_file.hpp
class generic_file is defined here as well as class fichier
libdar::null_file::inherited_write
virtual void inherited_write(const char *a, U_I siz) override
implementation of the write() operation
Definition: null_file.hpp:76
libdar::null_file::skip
virtual bool skip(const infinint &pos) override
skip at the absolute position
Definition: null_file.hpp:60
libdar::generic_file
this is the interface class from which all other data transfer classes inherit
Definition: generic_file.hpp:76
libdar::null_file::inherited_read
virtual U_I inherited_read(char *a, U_I size) override
implementation of read() operation
Definition: null_file.hpp:68
libdar::null_file
the null_file class implements the /dev/null behavior
Definition: null_file.hpp:49
libdar::null_file::inherited_sync_write
virtual void inherited_sync_write() override
write down any pending data
Definition: null_file.hpp:84
libdar::null_file::get_position
virtual infinint get_position() const override
get the current read/write position
Definition: null_file.hpp:63
libdar
libdar namespace encapsulate all libdar symbols
Definition: archive.hpp:46