Disk ARchive
2.4.8
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the cache class implements a very basic read/write caching mechanism More...
#include <cache.hpp>
Inherits libdar::generic_file.
Public Member Functions | |
cache (generic_file &hidden, bool shift_mode, U_I initial_size=10240, U_I unused_read_ratio=10, U_I observation_read_number=100, U_I max_size_hit_read_ratio=50, U_I unused_write_ratio=10, U_I observation_write_number=100, U_I max_size_hit_write_ratio=50) | |
cache (const cache &ref) | |
const cache & | operator= (const cache &ref) |
bool | skip (const infinint &pos) |
skip at the absolute position | |
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 () |
get the current read/write position | |
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generic_file (gf_mode m) | |
main constructor | |
generic_file (const generic_file &ref) | |
copy constructor | |
void | terminate () const |
virtual destructor, this let inherited destructor to be called even from a generic_file pointer to an inherited class | |
const generic_file & | operator= (const generic_file &ref) |
assignment operator | |
gf_mode | get_mode () const |
retreive the openning mode for this object | |
U_I | read (char *a, U_I size) |
read data from the generic_file | |
void | write (const char *a, U_I size) |
write data to the generic_file | |
void | write (const std::string &arg) |
write a string to the generic_file | |
S_I | read_back (char &a) |
skip back one char, read on char and skip back one char | |
S_I | read_forward (char &a) |
read one char | |
virtual void | copy_to (generic_file &ref) |
copy all data from current position to the object in argument | |
virtual void | copy_to (generic_file &ref, const infinint &crc_size, crc *&value) |
copy all data from the current position to the object in argument and computes a CRC value of the transmitted data | |
U_32 | copy_to (generic_file &ref, U_32 size) |
small copy (up to 4GB) with CRC calculation | |
infinint | copy_to (generic_file &ref, infinint size) |
copy the given amount to the object in argument | |
bool | diff (generic_file &f, const infinint &crc_size, crc *&value) |
compares the contents with the object in argument | |
void | reset_crc (const infinint &width) |
reset CRC on read or writen data | |
bool | crc_status () const |
to known whether CRC calculation is activated or not | |
crc * | get_crc () |
get CRC of the transfered date since last reset | |
void | sync_write () |
write any pending data |
Protected Member Functions | |
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_terminate () |
destructor-like call, except that it is allowed to throw exceptions | |
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void | set_mode (gf_mode x) |
bool | is_terminated () const |
the cache class implements a very basic 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 can contain. This makes a lot of small read or write, 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 read or write into much bigger ones. This in only when there is no compression that that this class is useful (and used).
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protectedvirtual |
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.
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inlineprotectedvirtual |
write down any pending data
Implements libdar::generic_file.
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inlineprotectedvirtual |
destructor-like call, except that it is allowed to throw exceptions
Implements libdar::generic_file.
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protectedvirtual |
implementation of the write() operation
[in] | a | what data to write |
[in] | size | amount of data to write |
Implements libdar::generic_file.
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virtual |
skip at the absolute position
[in] | pos | the offset in byte where next read/write operation must start |
Implements libdar::generic_file.