LTAVIEW:
~~~~~~~
    A specialization of LTAFMT object which allows selections to be
    applied to the underlying LTAFMT object and presents the resultant
    view.   

    Currently the only selection that can be applied is on the source
    name and scan numbers.  It can also be used to average the data in
    time and frequency.  Only the selected source will be visible via
    this object.  Later as and when the need arises, selection on
    time, frequency, baseline etc can also be applied - but all that
    has be thought of and implemented carefully.  The issues there
    would be that of efficiency and speed.

Method:
~~~~~~
    
    The following methods of the LTAFMT object have been overloaded.
    The calling signature remains same.  However there behavior is
    slightly changed as explained below.  All methods of LTAFMT
    (described in the documentation on LTAFMT object are available from
    this object as well).

    LTAVIEW():
     A blank constructor.

    LTAVIEW(char *IFile, char *OFile=NULL, char *Obj=NULL);
     Alternate constructor which attach the input stream to the file
     named by IFile.  The next two arguments are optional.  If OFile
     is not given, the output stream will be attached to stdout.  If
     Obj is not given, all sources in the file will be visible.  
     
     If Obj is given, only the given source name would be visible.  If
     the given source is not present in the file, a fatal error would
     be detected.

    ~LTAVIEW();
     The destructor.

    int reset(char *IFile, char *OFile, char *Obj);
     Same function as the second constructor.  This is used when an
     empty object (via the blank construct - also called the default
     constructor in the OOP jargon) has to be initialized.

    int getnscans();
     Returns the no. of scan for the chosen source found.

    int skipscan(int n);
     Skips to the nth. scan of the chosen source.
   
    int rd_data(char *buf);
     Reads the next record corresponding the chosen source into the
     buffer buf.

    int rd_data();
     Reads the next record corresponding the chosen source into an
     internal buffer.


-----------------------------------------------------------------------
Policy regarding handling input data from a pipe:
------------------------------------------------

1.  LTAVIEW::getScanRecords(int n)

    This function returns the no. of records in the nth scan of the
    database in case of disk file.  In case of a pipe, it throws an
    ltaError exception with a ErrorObj::Recoverable state set in the
    exception object.

2.  LTAVIEW::getMaxRecords()

    Returns the max. no. of records in a ANY scan in case of a disk
    file.  In case of a pipe, this throws an exception of type
    ltaError with ErrorObj::Recoverable state set in the exception
    object. 

3.  LTAVIEW::getnscans()

    Returns the no. of scans in case of a disk file.  In case of a
    pipe, throws an exception of type ltaError with
    ErrorObj::Recoverable state set in the exception object.

4.  LTAVIEW::scanSelect(int,int *)

    Sets the list of logical scan nos. of the selected object to be
    passed to the applications programm.   This works for both cases. 

5.  LTAVIEW::avgrd_data(char *,.....)

    In case of disk file, does averaging and/or normalization of the
    data.  In case of pipe, works for no averaging (ie. no further
    averaging of the data on-the-fly).  In case more averaging is
    attempted, this might misbehave at scan boundaries where it might
    not have enough records left before the next scan begins to make
    the desired integration.


The entire logic of handling data from a pipe is handled by the
EatData, LTAInputFromPipe and ThisScan state variables.  If
LTAInputFromPipe is set, EatData is used to eat data to simulate the
action of skipscan, skiprecord, etc.  To determine if the current scan
is the selected one (selection is a combination of SourceName (which
is a regular expression comparator object) and the list of logical
scan nos.), ThisScan is used which increments linearly with every new
scan.