FBB::OmmapStream(3bobcat)

std::istream using FBB::MmapBuf as streambuf
(libbobcat-dev_6.07.01)

2005-2025

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

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

  • 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.

    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

    Debian Bobcat project files:

    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).