FBB::Sharedpos - Shared Memory offset controller
#include <bobcat/sharedpos>
Linking option: -lbobcat
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.
FBB
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace FBB.
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.
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- 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.
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- 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.
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- std::ostream &operator<<(std::ostream &out, SharedPos
const &pos):
Inserts information about the SharedPos object into out.
Copy and move assignment operators are available.
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.
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- bool atMaxOffset() const:
Returns true if offset equals the maximum offset that can be used for
the configured FBB::SharedSegment object.
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- size_t blockIdx() const:
The index of the configured FBB::SharedSegment object’s shared
segment data block to which offset refers is returned.
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- size_t blockOffset() const:
The offset within the shared segment data block matching the member
offset’s return value is returned.
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- 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.
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- 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).
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- std::streamsize maxOffset() const:
The maximum possible offset that can be used for the currently monitored
FBB::SharedSegment is returned.
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- std::streamsize offset() const:
The offset within the currently monitored shared memory segment is
returned.
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- 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.
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- 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.
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- 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.
bobcat/sharedpos - defines the class interface
bobcat(7), isharedstream(3bobcat),
osharedstream(3bobcat), sharedblock(3bobcat),
sharedcondition(3bobcat), sharedmemory(3bobcat),
sharedmutex(3bobcat), sharedreadme(7bobcat),
sharedsegment(3bobcat), sharedstream(3bobcat),
sharedstreambuf(3bobcat)
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- bobcat_4.08.06-x.dsc: detached signature;
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- bobcat_4.08.06-x.tar.gz: source archive;
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- bobcat_4.08.06-x_i386.changes: change log;
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- libbobcat1_4.08.06-x_*.deb: debian package holding the
libraries;
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- libbobcat1-dev_4.08.06-x_*.deb: debian package holding the
libraries, headers and manual pages;
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- http://sourceforge.net/projects/bobcat: public archive location;
Bobcat is an acronym of `Brokken’s Own Base Classes And
Templates’.
This is free software, distributed under the terms of the GNU
General Public License (GPL).
Frank B. Brokken (f.b.brokken@rug.nl).