FBB::Sharedpos - Shared Memory offset controller

       Frank B. Brokken (f.b.brokken@rug.nl).

libbobcat-dev_6.07.01                               2005-2025                            FBB::Sharedpos(3bobcat)

       Bobcat is an acronym of `Brokken’s Own Base Classes And Templates’.

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

       Debian Bobcat project files:

       o      libbobcat6: debian package containing the shared library, changelog and copyright note;

       o      libbobcat-dev:  debian package containing the static library, headers, manual pages, and developer
              info;

       None Reported.

       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.

       This is free software, distributed under the terms of the GNU General Public License (GPL).

       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.

       See the sharedstream(3bobcat) man page.

bobcat/sharedpos - defines the class interface

       -

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

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

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

       o      booleof()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::streamsizeeos()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::streamsizemaxOffset()const:
              The maximum possible offset that can be used for the  currently  monitored  FBB::SharedSegment  is
              returned.

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

       o      voidreset(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::streamsizeshowmanyc()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_typeseek(std::ios::off_typeoffset,std::ios::seekdirorigin=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.

       FBB::Sharedpos - Shared Memory offset controller

FBB
       All constructors, members, operators and manipulators, mentioned in this man-page,  are  defined  in  the
       namespace FBB.

       o      voidoperator++():
              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      voidoperator+=(size_tlen):
              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,SharedPosconst&pos):
              Inserts information about the SharedPos object into out.

bobcat(7),          isharedstream(3bobcat),         osharedstream(3bobcat),         sharedblock(3bobcat),
       sharedcondition(3bobcat),     sharedmemory(3bobcat),     sharedmutex(3bobcat),     sharedreadme(7bobcat),
       sharedsegment(3bobcat), sharedstream(3bobcat), sharedbuf(3bobcat)

#include<bobcat/sharedpos>
       Linking option: -lbobcat