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

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

libbobcat-dev_6.07.01                               2005-2025                          FBB::OmmapStream(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.

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

       o      OmmapStream(std::stringconst&fname,charconst*bufSize=0,std::ios::openmodeopenMode=std::ios::out,mode_tmode=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.

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

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.

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

bobcat/ommapstream - defines the class interface

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

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

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

       o      size_tfileSize()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_tpageSize()const:
              returns the smallest page size used by t(mmap).

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

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

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

#include<bobcat/ommapstream>

       Linking option: -lbobcat