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Disk ARchive
2.5.2
Full featured and portable backup and archiving tool
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#include <cache.hpp>
Inherits libdar::generic_file.
Public Member Functions | |
cache (generic_file &hidden, bool shift_mode, U_I size=102400) | |
cache (const cache &ref) | |
const cache & | operator= (const cache &ref) |
void | change_to_read_write () |
bool | skippable (skippability direction, const infinint &amount) |
bool | skip (const infinint &pos) |
bool | skip_to_eof () |
skip to the end of file | |
bool | skip_relative (S_I x) |
skip relatively to the current position | |
infinint | get_position () const |
get the current read/write position | |
Protected Member Functions | |
void | inherited_read_ahead (const infinint &amount) |
U_I | inherited_read (char *a, U_I size) |
implementation of read() operation | |
void | inherited_write (const char *a, U_I size) |
implementation of the write() operation | |
void | inherited_sync_write () |
write down any pending data | |
void | inherited_flush_read () |
void | inherited_terminate () |
destructor-like call, except that it is allowed to throw exceptions |
the cache class implements a fixed length read/write caching mechanism
it is intended to reduce context switches when no compression is used and when reading or writing catalogue through a pipe. The catalogue read and write is done by calling dump/constructor methods of the many objects that a catalogue contains. This makes a lot of small reads or writes, which make very poor performances when used over the network through a pipe to ssh. When compression is used, the problem disapears as the compression engine gather these many small reads or writes into much bigger ones. This in only when there is no compression or encryption that this class is useful (and used). Another target of class cache is to provide limited skippability when data is read of written to pipe (which do not have any skippability)
void libdar::cache::inherited_flush_read | ( | ) | [inline, protected, virtual] |
reset internal engine, flush caches in order to read the data at current position
Implements libdar::generic_file.
U_I libdar::cache::inherited_read | ( | char * | a, |
U_I | size | ||
) | [protected, virtual] |
implementation of read() operation
[in,out] | a | where to put the data to read |
[in] | size | says how much data to read |
Implements libdar::generic_file.
void libdar::cache::inherited_read_ahead | ( | const infinint & | amount | ) | [inline, protected, virtual] |
tells the object that several calls to read() will follow to probably obtain at least the given amount of data
[in] | amount | is the maximum expected amount of data that is known to be read |
Implements libdar::generic_file.
Definition at line 73 of file cache.hpp.
References libdar::generic_file::read_ahead().
void libdar::cache::inherited_sync_write | ( | ) | [inline, protected, virtual] |
write down any pending data
Implements libdar::generic_file.
void libdar::cache::inherited_terminate | ( | ) | [inline, protected, virtual] |
destructor-like call, except that it is allowed to throw exceptions
Implements libdar::generic_file.
void libdar::cache::inherited_write | ( | const char * | a, |
U_I | size | ||
) | [protected, virtual] |
implementation of the write() operation
[in] | a | what data to write |
[in] | size | amount of data to write |
Implements libdar::generic_file.
bool libdar::cache::skip | ( | const infinint & | pos | ) | [virtual] |
skip at the absolute position
[in] | pos | the offset in byte where next read/write operation must start |
Implements libdar::generic_file.
bool libdar::cache::skippable | ( | skippability | direction, |
const infinint & | amount | ||
) | [virtual] |
whether the implementation is able to skip
Implements libdar::generic_file.