FBB::Sharedpos(3bobcat)
Shared Memory Offsets
(libbobcat-dev_4.08.03-x.tar.gz)
2005-2018
NAME
FBB::Sharedpos - Shared Memory offset controller
SYNOPSIS
#include <bobcat/sharedpos>
Linking option: -lbobcat
DESCRIPTION
The class SharedPos is a support class for Bobcat's shared memory
handling classes. It controls the shared memory read/write ofset and ensures
that shared memory operations never exceed the shared memory's maximum offset.
The class SharedPos has several public members, but they are primarily
useful for other Shared* classes offered by Bobcat. There is probably
little use for a stand-alone SharedPos object.
In the descriptions of the class's member functions offset refers to
the read/write offset within a FBB::SharedSegment(3bobcat) object for
which SharedPos performs the offset-administration.
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace FBB.
INHERITS FROM
-
TYPEDEFS AND ENUMS
CONSTRUCTORS
Default, copy and move constructors are available. The default constructor
does not yet monitor the offset of an FBB::SharedSegment
object. The member reset is used to start monitoring offsets.
OVERLOADED OPERATORS
- void operator++():
The offset is incremented. If this member is called when the offset is
equal to the shared memory's maximum offset an FBB::Exception is
thrown.
- void operator+=(size_t len):
The offset is incremented by len. If offset + len exceeds the
shared memory's maximum offset then the offset is set to the maximum
offset and an FBB::Exception is thrown.
- std::ostream &operator<<(std::ostream &out, SharedPos const &pos):
Inserts information about the SharedPos object into out.
Copy and move assignment operators are available.
MEMBER FUNCTIONS
Note: the behavior of member functions returning values which refer to
information of an FBB::SharedSegment is undefined until the member
reset has been called.
- bool atMaxOffset() const:
Returns true if offset equals the maximum offset that can be used
for the configured FBB::SharedSegment object.
- size_t blockIdx() const:
The index of the configured FBB::SharedSegment object's shared
segment data block to which offset refers is returned.
- size_t blockOffset() const:
The offset within the shared segment data block matching the member
offset's return value is returned.
- bool eof() const:
Returns true if offset exceeds the maximum offset of any character
ever written to the shared memory to which the SharedPos object
interfaces. If eof returns true information may still be
written to the shared memory: writing is possible until the
maximum shared memory segment offset has been reached.
- std::streamsize eos() const:
The offset just beyond the maximum offset for the current shared
segment data block is returned. E.g., if blockIdx returns 5, and
the size of the shared segment data blocks equals 2000, then eos
returns 12000 (the first offset of segment 6).
- std::streamsize maxOffset() const:
The maximum possible offset that can be used for the currently
monitored FBB::SharedSegment is returned.
- std::streamsize offset() const:
The offset within the currently monitored shared memory segment is
returned.
- void reset(SharedSegment *sharedData):
The SharedPos object is reset to monitor the offset of the
FBB::SharedSegment object whose address is passed as argument to
reset. The address must point to a sharedsegment(3bobcat)
object that must exist until the end of the SharedPos
object's lifetime or until its next reset call. Immediately after
calling reset offset is reset to 0.
- std::streamsize showmanyc() const:
The number of characters that can be read from the current shared
segment data block is returned. This member interrogates the number
of readable characters in the shared memory segment. This number may
change while this member is being executed. In order to receive a
stable return value, calling functions should have obtained a lock on
the FBB::SharedSegment data before calling this member. See also
the sharedsegment(3bobcat) man-page.
- std::ios::pos_type seek(std::ios::off_type offset,
std::ios::seekdir origin = std::ios::beg):
The monitored offset is changed to this member's offset argument,
relative to origin. Seeking beyond eof is OK. However, -1 is
returned when seeking beyond maxOffset or seeking before the
shared segment's offset 0.
EXAMPLE
See the sharedstream(3bobcat) man page.
FILES
bobcat/sharedpos - defines the class interface
SEE ALSO
bobcat(7),
isharedstream(3bobcat),
osharedstream(3bobcat),
sharedblock(3bobcat),
sharedcondition(3bobcat),
sharedmemory(3bobcat),
sharedmutex(3bobcat),
sharedreadme(7bobcat),
sharedsegment(3bobcat),
sharedstream(3bobcat),
sharedstreambuf(3bobcat)
BUGS
None Reported.
DISTRIBUTION FILES
- bobcat_4.08.03-x.dsc: detached signature;
- bobcat_4.08.03-x.tar.gz: source archive;
- bobcat_4.08.03-x_i386.changes: change log;
- libbobcat1_4.08.03-x_*.deb: debian package holding the
libraries;
- libbobcat1-dev_4.08.03-x_*.deb: debian package holding the
libraries, headers and manual pages;
- http://sourceforge.net/projects/bobcat: public archive location;
BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.
COPYRIGHT
This is free software, distributed under the terms of the
GNU General Public License (GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).