.TH "FBB::Sharedpos" "3bobcat" "2005\-2023" "libbobcat\-dev_6\&.04\&.00" "Shared Memory Offsets"

.PP 
.SH "NAME"
FBB::Sharedpos \- Shared Memory offset controller
.PP 
.SH "SYNOPSIS"
\fB#include <bobcat/sharedpos>\fP
.br 
Linking option: \fI\-lbobcat\fP
.PP 
.SH "DESCRIPTION"

.PP 
The class \fBSharedPos\fP is a support class for Bobcat\(cq\&s shared memory
handling classes\&. It controls the shared memory read/write ofset and ensures
that shared memory operations never exceed the shared memory\(cq\&s maximum offset\&.
.PP 
The class \fBSharedPos\fP has several public members, but they are primarily
useful for other \fIShared*\fP classes offered by Bobcat\&. There is probably
little use for a stand\-alone \fBSharedPos\fP object\&.
.PP 
In the descriptions of the class\(cq\&s member functions \fIoffset\fP refers to
the read/write offset within a \fBFBB::SharedSegment\fP(3bobcat) object for
which \fBSharedPos\fP performs the offset\-administration\&.
.PP 
.SH "NAMESPACE"
\fBFBB\fP
.br 
All constructors, members, operators and manipulators, mentioned in this
man\-page, are defined in the namespace \fBFBB\fP\&.
.PP 
.SH "INHERITS FROM"
\-
.PP 
.SH "TYPEDEFS AND ENUMS"

.PP 
.SH "CONSTRUCTORS"

.PP 
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 \fIFBB::SharedSegment\fP
object\&. The member \fIreset\fP is used to start monitoring offsets\&.
.PP 
.SH "OVERLOADED OPERATORS"
.IP o 
\fBvoid operator++()\fP:
.br 
The offset is incremented\&. If this member is called when the offset is
equal to the shared memory\(cq\&s maximum offset an \fIFBB::Exception\fP is
thrown\&.
.IP 
.IP o 
\fBvoid operator+=(size_t len)\fP:
.br 
The offset is incremented by \fIlen\fP\&. If \fIoffset + len\fP exceeds the
shared memory\(cq\&s maximum offset then the offset is set to the maximum
offset and an \fIFBB::Exception\fP is thrown\&.
.IP 
.IP o 
\fBstd::ostream &operator<<(std::ostream &out, SharedPos const &pos)\fP:
.br 
Inserts information about the \fBSharedPos\fP object into \fIout\fP\&.

.PP 
.SH "MEMBER FUNCTIONS"

.PP 
Note: the behavior of member functions returning values which refer to
information of an \fIFBB::SharedSegment\fP is undefined until the member
\fIreset\fP has been called\&.
.PP 
.IP o 
\fBbool atMaxOffset() const\fP:
.br 
Returns \fItrue\fP if offset equals the maximum offset that can be used
for the configured \fIFBB::SharedSegment\fP object\&.
.IP 
.IP o 
\fBsize_t blockIdx() const\fP:
.br 
The index of the configured \fIFBB::SharedSegment\fP object\(cq\&s shared
segment data block to which offset refers is returned\&.
.IP 
.IP o 
\fBsize_t blockOffset() const\fP:
.br 
The offset within the shared segment data block matching the member
\fIoffset\fP\(cq\&s return value is returned\&.
.IP 
.IP o 
\fBbool eof() const\fP:
.br 
Returns \fItrue\fP if offset exceeds the maximum offset of any character
ever written to the shared memory to which the \fBSharedPos\fP object
interfaces\&. If \fIeof\fP returns \fItrue\fP information may still be
\fIwritten\fP to the shared memory: writing is possible until the
maximum shared memory segment offset has been reached\&.
.IP 
.IP o 
\fBstd::streamsize eos() const\fP:
.br 
The offset just beyond the maximum offset for the current shared
segment data block is returned\&. E\&.g\&., if \fIblockIdx\fP returns 5, and
the size of the shared segment data blocks equals 2000, then \fIeos\fP
returns 12000 (the first offset of segment 6)\&.
.IP 
.IP o 
\fBstd::streamsize maxOffset() const\fP:
.br 
The maximum possible offset that can be used for the currently
monitored \fIFBB::SharedSegment\fP is returned\&.
.IP 
.IP o 
\fBstd::streamsize offset() const\fP:
.br 
The offset within the currently monitored shared memory segment is
returned\&.
.IP 
.IP o 
\fBvoid reset(SharedSegment *sharedData)\fP:
.br 
The \fISharedPos\fP object is reset to monitor the offset of the
\fIFBB::SharedSegment\fP object whose address is passed as argument to
\fIreset\fP\&. The address must point to a \fBsharedsegment\fP(3bobcat)
object that must exist until the end of the \fBSharedPos\fP
object\(cq\&s lifetime or until its next \fIreset\fP call\&. Immediately after
calling \fIreset\fP offset is reset to 0\&.
.IP 
.IP o 
\fBstd::streamsize showmanyc() const\fP:
.br 
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 \fIFBB::SharedSegment\fP data before calling this member\&. See also
the \fBsharedsegment\fP(3bobcat) man\-page\&.
.IP 
.IP o 
\fBstd::ios::pos_type seek(std::ios::off_type offset,
std::ios::seekdir origin = std::ios::beg)\fP:
.br 
The monitored offset is changed to this member\(cq\&s \fIoffset\fP argument,
relative to \fIorigin\fP\&. Seeking beyond \fIeof\fP is OK\&. However, \-1 is
returned when seeking beyond \fImaxOffset\fP or seeking before the
shared segment\(cq\&s offset 0\&.

.PP 
.SH "EXAMPLE"
See the \fBsharedstream\fP(3bobcat) man page\&.
.PP 
.SH "FILES"
\fIbobcat/sharedpos\fP \- defines the class interface
.PP 
.SH "SEE ALSO"
\fBbobcat\fP(7),
\fBisharedstream\fP(3bobcat),
\fBosharedstream\fP(3bobcat),
\fBsharedblock\fP(3bobcat),
\fBsharedcondition\fP(3bobcat),
\fBsharedmemory\fP(3bobcat),
\fBsharedmutex\fP(3bobcat),
\fBsharedreadme\fP(7bobcat),
\fBsharedsegment\fP(3bobcat),
\fBsharedstream\fP(3bobcat),
\fBsharedbuf\fP(3bobcat)
.PP 
.SH "BUGS"
None Reported\&.
.PP 
.SH "BOBCAT PROJECT FILES"

.PP 
.IP o 
\fIhttps://fbb\-git\&.gitlab\&.io/bobcat/\fP: gitlab project page;
.IP o 
\fIbobcat_6\&.04\&.00\-x\&.dsc\fP: detached signature;
.IP o 
\fIbobcat_6\&.04\&.00\-x\&.tar\&.gz\fP: source archive;
.IP o 
\fIbobcat_6\&.04\&.00\-x_i386\&.changes\fP: change log;
.IP o 
\fIlibbobcat1_6\&.04\&.00\-x_*\&.deb\fP: debian package containing the
libraries;
.IP o 
\fIlibbobcat1\-dev_6\&.04\&.00\-x_*\&.deb\fP: debian package containing the
libraries, headers and manual pages;

.PP 
.SH "BOBCAT"
Bobcat is an acronym of `Brokken\(cq\&s Own Base Classes And Templates\(cq\&\&.
.PP 
.SH "COPYRIGHT"
This is free software, distributed under the terms of the
GNU General Public License (GPL)\&.
.PP 
.SH "AUTHOR"
Frank B\&. Brokken (\fBf\&.b\&.brokken@rug\&.nl\fP)\&.
.PP