Provided by: libbobcat-dev_2.20.01-1_amd64 bug

NAME

       FBB::Mstream - Generic message handling stream

SYNOPSIS

       #include <bobcat/mstream>
       Linking option: -lbobcat

DESCRIPTION

       Objects  of  this class may be used to handle messages in a standardized way. Messages may
       be prefixed with order numbers and labels  and/or  line  numbers.  Messages  generated  by
       Mstream  objects  may  optionally  end in an exception, allowing simple implementation of,
       e.g., fatal error messages.

       Four message streams are provided by the BOBCAT library and may be  used  after  including
       the mstream header file. They are all defined in the FBB namespace:

       o      FBB::emsg for generating standard (labeled and numbered) error messages, e.g.

              [Error 1] this is an error message

       o      FBB::fmsg  for  generating  (labeled) fatal error messages, ending in an exception,
              e.g.,

              [Fatal] this fatal message is followed by an exception

       o      FBB::imsg for generating plain informational messages, e.g.,

              this is a plain message

       o      FBB::wmsg for generating (labeled) warning messages;

              [Warning] this is a warning

              By default all messages are inserted into the standard  output  stream,  but  other
              destinations (standard error, a named file, etc.) can easily be configured.

       Mstream objects themselves are std::ostream objects, so they can be used as objects passed
       to functions expecting ostream arguments.  Messages  inserted  into  Mstream  objects  are
       buffered  until  the  buffer  is  flushed  by  their std::ostream parts or when either the
       FBB::endl or FBB::flush is inserted into the message stream. Since these manipulators  act
       like  std::endl  and  std::flush  when  inserted into another kind of std::ostream object,
       using FBB::endl and  using  FBB::flush  might  be  worth  considering.  Also,  when  using
       namespace  std  and  using  namespace  FBB  is  specified  the  FBB::endl  and  FBB::flush
       manipulator will automatically be used with Mstream objects.

       Messages inserted into Mstream objects are considered completed at the  insertion  of  the
       FBB::endl  or FBB::flush manipulators. Message labels, line number labels and line numbers
       will only be shown for the next line after  these  manipulators  have  been  inserted  and
       exceptions are, if needed, thrown from these manipulators.

NAMESPACE

       FBB
       All elements mentioned in this man-page, are defined in the namespace FBB.

INHERITS FROM

       std::ostream

CONSTRUCTORS

       o      Mstream():
              The  default  constructor  generates  messages  using  the  std::streambuf  used by
              std::cout. There is no limit to the number of messages that  may  be  inserted.  No
              message or line numbers are shown, no exception are thrown when inserting messages.

       o      explicit  Mstream(std::ostream &ostr, size_t maxCount = UINT_MAX, std::string const
              &tag = "", bool throwing = false):
              This constructor uses the std::streambuf that is also used by the ostream ostr.  By
              default  (using  the  default  argument  values) there is no limit to the number of
              messages that may be inserted. No message or line numbers are shown,  no  exception
              are  thrown  when inserting messages. Specifying any other value than UINT_MAX will
              set the maximum number of messages that can be inserted  to  that  value.  The  tag
              defines  the text of the message label (e.g., Error). When throwing is specified as
              true an FBB::Errno exception is thrown after completing a  message.  The  generated
              exception  holds  the  id  (see below for the member id) of the Mstream object from
              which the exception was thrown as well as the text FBB::Mstream.

       o      explicit Mstream(std::streambuf &buf, size_t maxCount = UINT_MAX, std::string const
              &tag = "", bool throwing = false):
              This  constructor  uses  buf  to insert messages into. The remaining parameters are
              identical to those of the previous constructor.

       o      explicit Mstream(std::string const &name, size_t maxCount =  UINT_MAX,  std::string
              const &tag = "", bool throwing = false):
              This  constructor  creates  a  std::ofstream  from  the provided name parameter. It
              throws an FBB::Errno exception if the stream cannot be opened  for  writing.  If  a
              file  by  that  name  already exists it is rewritten.  The remaining parameters are
              identical to those of the previous two  constructors.   As  Mstream  inherits  from
              std::ostream   the   copy  constructor  is  not  available.  Neither  is  the  move
              constructor.

MEMBER FUNCTIONS

       o      size_t count() const:
              returns the number of inserted messages (if setCount has been called: the value set
              by the last setCount call plus the number of inserted messages since that call).

       o      bool  isActive() const:
              returns  true  if  messages can  actually be inserted into the FBB::MStream object,
              and false if inserted messages are ignored.  When  ignoring  messages  the  message
              count is not updated.

       o      int id() const:
              returns the unique id of the Mstream object.

       o      bool lineExcess() const:
              returns true after attempting to insert an additional message after maxCount number
              of messages have been inserted.

       o      std::string const &lineTag() const:
              returns the currently used line-tag (by default `Line’).

       o      size_t maxCount() const:
              returns the maximum number of messages that can be inserted. If the returned  value
              equals  UINT_MAX  then  there  is  no  limit  to the number of messages that can be
              inserted.

       o      void noLineNr():
              calling this member will suppress the display of a line  number  if  it  is  called
              after  calling  setLineNr  (see  below) but before a message is being (or has been)
              inserted.

       o      void off():
              after calling off messages inserted into the Mstream object are  silently  ignored.
              After calling off the internal message counter is not incremented when messages are
              inserted.

       o      void on():
              by default and after calling on messages inserted into the Mstream object are  sent
              to their destination stream.

       o      void reset(std::ostream &ostr):
              messages  inserted  into  the Mstream object are handled by the std::streambuf also
              used by ostr. Other parameters (e.g., maxCount, the message label) are kept as-is.

       o      void reset(std::streambuf *buf):
              messages inserted into the Mstream object are handled by std::streambuf buf.  Other
              parameters (e.g., maxCount, the message label) are kept as-is.

       o      void reset(FBB::Mstream const &mstream):
              the current object is reset using the parameters of the mstream parameter.

       o      void  reset(std::string  const &name, size_t maxCount, std::string const &tag, bool
              throwing):
              messages inserted into Mstream objects are handled by a std::ofstream created using
              the  provided  name parameter.  FBB::Errno exception if the stream cannot be opened
              for writing. If a  file  by  that  name  already  exists  it  is  rewritten.  Other
              parameters (e.g., maxCount, the message label) are kept as-is.

       o      void  reset(std::ostream  &ostr,  size_t  maxCount,  std::string  const  &tag, bool
              throwing):
              messages inserted into Mstream objects are handled by the std::streambuf also  used
              by  ostr.   By  specifying UINT_MAX for maxCount there is no limit to the number of
              messages that may be handled by this std::streambuf. The tag defines  the  text  of
              the  message  label  (e.g.,  Error  or the empty string for no message label). When
              throwing is specified as true an FBB::Errno exception is thrown after completing  a
              message.

       o      void  reset(std::streambuf  *buf,  size_t  maxCount,  std::string  const &tag, bool
              throwing):
              messages inserted into Mstream objects  are  handled  by  std::streambuf  buf.  The
              remaining parameters are identical to those of the previous reset member.

       o      void  reset(std::string  const &name, size_t maxCount, std::string const &tag, bool
              throwing):
              messages inserted into Mstream objects are handled by a std::ofstream created using
              the provided name parameter. It throws an FBB::Errno exception if the stream cannot
              be opened for writing. If a file by that name already exists it is rewritten.   The
              remaining parameters are identical to those of the previous two reset members.

       o      void reset(FBB::Mstream const &mstream):
              the  current  object  is  reset  using  the  parameters  of  the mstream parameter.
              Following the reset all of the current object’s  parameters  can  independently  be
              modified from those used by mstream.

       o      bool setActive(bool ifTrue):
              If  ifTrue  equals  true  the  Mstream  is  activated  otherwise  its  actions  are
              suppressed. Returns ifTrue.

       o      void setCount(size_t count):
              assigns the value count to the object’s message counter.

       o      void setLineNr(size_t lineNr):
              specifies the value lineNr as the message’s line  number  when  the  next  line  is
              displayed  (see also noLineNr). This value is not changed by the Mstream object. To
              display another line number the member will have to be called again (i.e., the line
              number is not displayed automatically again at every new line).

       o      void setLineTag(std::string const &tag):
              specifies the tag prefixing line numbers. By default the line tag equals `Line’.

       o      void setMaxCount(size_t maxCount):
              defines  maxCount  as  the maximum number of messages that can be inserted into the
              Mstream object.

       o      void setTag(std::string const &tag):
              specifies the tag prefixing messages. By default the tag is empty. If not empty the
              tag  is  enclosed  by square brackets. E.g., specifying the tag `Error’ will prefix
              messages with [Error].

       o      std::string const &tag() const:
              returns the currently used message tag (by default an empty string).

       o      bool throws():
              returns true when the Mstream object will throw an FBB::Errno exception at the next
              completed message. The generated exception holds the id (see earlier for the member
              id) of the Mstream object from which the exception was thrown as well as  the  text
              FBB::Mstream.

       o      void throwing(bool ifTrue):
              modifies  the behaviro of Mstream objects at completed messages. After passing true
              Mstream objects will throw an FBB::Errno exception at the next  completed  message,
              otherwise  this  exception is not thrown. The generated exception holds the id (see
              earlier for the member id) of the Mstream  object  from  which  the  exception  was
              thrown as well as the text FBB::Mstream.

MANIPULATORS

       Note  that  the  following  two manipulators are not members of the class Mstream, but are
       free functions defined in the namespace FBB.

       o      std::ostream &endl(std::ostream &out):
              This manipulator inserts a newline character in the Mstream’s stream and then calls
              FBB::flush.  This manipulator acts like std::endl and std::flush when inserted into
              another kind of std::ostream object.

       o      std::ostream &flush(std::ostream &out):
              This manipulator completes the message that is currently  being  inserted  into  an
              Mstream  object. It flushes the object’s destination stream and prepares the object
              for the next message.  When the object’s throws member returns true it  will  throw
              an  FBB:::Errno exception which holds the id (see earlier for the member id) of the
              Mstream  object  from  which  the  exception  was  thrown  as  well  as  the   text
              FBB::Mstream.  When used in combination with another kind of std::ostream object it
              acts like std::flush.

       As the manipulators  FBB::endl  and  FBB::flush  act  like,  respectively,  std::endl  and
       std::flush  when inserted into another kind of std::ostream object, using the declarations
       `using FBB::endl’ and `using FBB::flush’ might be  worth  considering.  Also,  when  using
       namespace  std  and  using  namespace  FBB  is  specified  the  FBB::endl  and  FBB::flush
       manipulator will automatically be  called  when  inserting  endl  or  flush  into  Mstream
       objects.

EXAMPLE

       #include <iostream>
       #include <algorithm>
       #include <iterator>

       #include <bobcat/mstream>
       #include <bobcat/errno>

       using namespace std;
       using namespace FBB;

       int main(int argc, char **argv)
       try
       {
           imsg << "Informational: " << endl;
           imsg.off();
           cout << "The i-msg stream is now off. This message should appear once" <<
                                                                               endl;
           imsg << "The i-msg stream is now off. This message should appear once" <<
                                                                               endl;
           imsg << "The i-msg stream is now off. This message should appear once" <<
                                                                               endl;
           cout << "But this message is shown" << endl;

           wmsg << "Warning message" << endl;
           emsg << "Oops, this this is an error (not really)" << endl;
           emsg << "Oops, this goes wrong, too" << endl;

           imsg.on();
           imsg << "And another informational msg: " << emsg.count() <<
                   " error messages\n" << flush;

           emsg << "Third error" << endl;
           emsg.setMaxCount(3);

           imsg << "Msg in between" << endl;

           cerr << "(cerr) LineExcess: " << emsg.lineExcess() << ", count = " <<
                   emsg.count() << endl;

           emsg << "Fourth error" << endl;

           cerr << "(cerr) LineExcess: " << emsg.lineExcess() << ", count = " <<
                   emsg.count() << endl;

           cerr << "Beyond\n";
       }
       catch(FBB::Errno const &e)
       {
           std::cerr << "Got an Errno object: " << e.why() << ’\n’;
       }
       catch(...)
       {
           std::cerr << "Got an exception\n";
       }

FILES

       bobcat/mstream - defines the class interface

SEE ALSO

       bobcat(7), errno(3bobcat), mbuf(3bobcat)

BUGS

       None Reported.

DISTRIBUTION FILES

       o      bobcat_2.20.01-x.dsc: detached signature;

       o      bobcat_2.20.01-x.tar.gz: source archive;

       o      bobcat_2.20.01-x_i386.changes: change log;

       o      libbobcat1_2.20.01-x_*.deb: debian package holding the libraries;

       o      libbobcat1-dev_2.20.01-x_*.deb:  debian  package holding the libraries, headers and
              manual pages;

       o      http://sourceforge.net/projects/bobcat: public archive location;

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).