FBB::OmmapStream(3bobcat)         std::istream using FBB::MmapBuf as streambuf



NAME
       FBB::OmmapStream - Input Stream using mmap(2) through FBB::MmapBuf

SYNOPSIS
       #include <bobcat/ommapstream>


       Linking option: -lbobcat

DESCRIPTION
       FBB::OmmapStream objects are used to write information to files which
       are made available in the virtual address space of the calling process.
       Using the virtual address space is handled by the class's privately
       inherited FBB::MmapBuf (std::streambuf class.

       By mapping files in the process's virtual address space the time
       required for processing such files is usually dramatically reduced.

       An std::exception is thrown, and an error message is written to cerr if
       the FBB::MmapBuf base class cannot determine the size of the specified
       file, or when the (un)mapping cannot be performed.

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

INHERITS FROM
       std::ostream, privately from FBB::MmapBuf.

CONSTRUCTORS
       o      OmmapStream():
              The default constructor merely constructs an empty OmmapStream
              object. To change it to a usable object use move assignment;

       o      OmmapStream(std::string const &fname, char const *bufSize = 0,
              std::ios::openmode openMode = std::ios::out, mode_t mode =
              0644):
              The constructor initializes the OmmapStream object for a file
              named fname.

       The openMode parameter specifies how fname is used. The standard
       ios::in, ios::out, ios::trunc, ios::app, and ios::ate modes are
       supported.

       By default bfOmmapStream) uses a mapping buffer size of 10 times the
       standard page size, (cf. sysconf(3), and the member pageSize below).
       The size of the mapping buffer can also be specified using the bufSize
       parameter. To specify it use a value followed by K, M, or G,
       representing, resp. 1024, 1024 * 1024, and 1024 * 1024 * 1024 bytes.
       The final buffer size is at least equal to the standard page size. When
       a larger value is specified the used buffer size is set to specified /
       pageSize * pageSize.

       The mode parameter specifies the user/group/other access mode which is
       used when the file is created by MmapBuf. Its default value specifies
       read/write access by the user, and  read access by others.  )

       The move constructor and move assignment operator are available.
       The copy constructor and copy assignment operator are not available.

MEMBER FUNCTIONS
       All members of std::istream are available, as FBB::OmmapStream inherits
       from that class.

       o      size_t bufSize() const:
              returns the used t(mmap) buffer size;

       o      size_t fileSize() const:
              returns the current size of the used file. The size is updated
              to a larger size when writing beyond the current file size. Once
              the OmmapStream object ceases to exist the used file's size is
              modified to the current fileSize value.

       o      size_t pageSize() const:
              returns the smallest page size used by t(mmap).


EXAMPLE
       An example is provided in bobcat's source archive and gitlab repository
       at bobcat/ommapstream/demo.

FILES
       bobcat/ommapstream - defines the class interface

SEE ALSO
       bobcat(7), chmod(2), immapstream(3bobcat), iommapstream(3bobcat),
       mmap(2), mmapbuf(3bobcat) sysconf(3)

BUGS
       None Reported.

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

       o      bobcat_6.06.02-x.dsc: detached signature;

       o      bobcat_6.06.02-x.tar.gz: source archive;

       o      bobcat_6.06.02-x_i386.changes: change log;

       o      libbobcat1_6.06.02-x_*.deb: debian package containing the
              libraries;

       o      libbobcat1-dev_6.06.02-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).

libbobcat-dev_6.06.02              2005-2024         FBB::OmmapStream(3bobcat)