oracular (3) sharedpos.3bobcat.gz

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 as well as the copy and move assignment operators 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

       o      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.

       o      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.

       o      std::ostream &operator<<(std::ostream &out, SharedPos const &pos):
              Inserts information about the SharedPos object into out.

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.

       o      bool atMaxOffset() const:
              Returns  true  if  offset  equals  the  maximum  offset  that  can  be  used  for  the  configured
              FBB::SharedSegment object.

       o      size_t blockIdx() const:
              The index of the configured FBB::SharedSegment object’s shared segment data block to which  offset
              refers is returned.

       o      size_t blockOffset() const:
              The  offset  within  the  shared  segment  data block matching the member offset’s return value is
              returned.

       o      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.

       o      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).

       o      std::streamsize maxOffset() const:
              The  maximum  possible  offset  that can be used for the currently monitored FBB::SharedSegment is
              returned.

       o      std::streamsize offset() const:
              The offset within the currently monitored shared memory segment is returned.

       o      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.

       o      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.

       o      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), sharedbuf(3bobcat)

BUGS

       None Reported.

BOBCAT PROJECT FILES

       o      https://fbb-git.gitlab.io/bobcat/: gitlab project page;

       o      bobcat_6.06.01-x.dsc: detached signature;

       o      bobcat_6.06.01-x.tar.gz: source archive;

       o      bobcat_6.06.01-x_i386.changes: change log;

       o      libbobcat1_6.06.01-x_*.deb: debian package containing the libraries;

       o      libbobcat1-dev_6.06.01-x_*.deb: debian package containing the libraries, headers and manual pages;

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).