Programming Information for Notes and History
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The Notes and History attributes in dataset headers are manipulated by
the following routines in file thd_notes.c (which is compiled into the
AFNI library libmri.a).  All functions that return a string (char *)
return a copy of the information requested.  This string will have
been malloc()-ed and should be free()-ed when it is no longer needed.

Notes are numbered 1, 2, ..., up to the value returned by
tross_Get_Notecount().  Note are always numbered contiguously.
The maximum number of Notes per dataset is 999.

Programs and plugins that create new datasets should also create a
History for the dataset, using one of the methods described below.
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int tross_Get_Notecount( THD_3dim_dataset * dset );

This routine returns the number of Notes stored in dataset "dset".
If -1 is returned, dset is not a valid dataset pointer.  If 0 is
returned, the dataset has no Notes at this time.
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char * tross_Get_Note( THD_3dim_dataset * dset, int inote );

This routine returns a copy of the "inote"-th Note in dataset "dset".
If NULL is returned, some error occurred (e.g., you asked for a non-
existent Note).
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char * tross_Get_Notedate( THD_3dim_dataset * dset, int inote );

This routine returns a string with the date that the "inote"-th Note
in dataset "dset" was created.  If NULL is returned, an error
occurred.
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void tross_Add_Note( THD_3dim_dataset *dset, char *cn );

This routine adds the string stored in "cn" to the dataset "dset".
A new Note is created at the end of all existing Notes.
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void tross_Store_Note( THD_3dim_dataset * dset, int inote, char * cn );

This routine stores string "cn" into dataset "dset" as Note number
"inote".  If this Note already exists, then it is replaced by the new
text.  If this Note number does not exist, then the new Note is
created by called tross_Add_Note(), which means that it's number may
not end up as "inote".
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void tross_Delete_Note(THD_3dim_dataset *dset, int inote);

This routine removes the "inote"-th Note from dataset "dset".  Any
notes above this Note are renumbered downwards by 1.
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char * tross_Get_History( THD_3dim_dataset *dset );

This function returns a copy of the History Note for dataset "dset".
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void tross_Make_History( char * pname, int argc, char ** argv,
                                       THD_3dim_dataset *dset );

This routine uses tross_commandline() to make an entry in the History
Note for dataset "dset".  If no History Note currently exists for
this dataset, one is created; otherwise, the command line is appended
to the History Note.
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void tross_Copy_History( THD_3dim_dataset * old_dset,
                         THD_3dim_dataset * new_dset );

This routine erases the History Note in dataset "new_dset" and
replaces it with the History Note in dataset "old_dset".  By combining
this routine with tross_Make_History(), a cumulative history of the
commands that led up to a dataset can be maintained.  The existing
AFNI programs use this function when creating a dataset from a single
input dataset (e.g., 3dmerge with one input), but do NOT use this
function when a dataset is created from many inputs (e.g., 3dmerge
with several input datasets being averaged).
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void tross_Append_History( THD_3dim_dataset *dset, char *cn );

This function appends the string "cn" to the History Note in dataset
"dset".  If you use tross_Make_History(), you don't need to use this
routine - it is only necessary if you have some custom history to add.
This routine adds the "[date time] " string to the front of "cn"
before storing it into the History Note.
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void tross_multi_Append_History( THD_3dim_dataset *dset, ... );

This function is like the previous one, but takes an arbitrary number
of strings as input.  Its usage is something like
  tross_multi_Append_History(dset,str1,str2,str3,NULL);
where each 'str' variable is of type char *.  The last input must
be NULL.  The strings are concatenated and then tross_Append_History
is invoked on the result.
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char * tross_commandline( char * pname, int argc, char ** argv );

This routine is designed to produce an approximate copy of the command
line used to invoke a program.
  pname = Program name
  argc  = argc from main()
  argv  = argv from main()
This function is invoked by tross_Make_History() and so doesn't often
need to be called directly by an AFNI program.
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char * tross_datetime(void);

This routine produces a string with the current date and time.  It
does not usually need to be called directly by an AFNI program.
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char * PLUTO_commandstring( PLUGIN_interface * plint );

This function (in afni_plugin.c) is used from within a plugin to
create a History string for storage in a dataset.  It is something
like tross_commandline(), in that it will produce a line that will
summarize how the plugin was run.  PLUTO_commandstring() can only
be invoked from plugins using standard (AFNI-generated) interfaces -
plugins that create there own interfaces must create their own
History as well.  A sample use of this function:

    char * his ;
    his = PLUTO_commandstring(plint) ;
    tross_Copy_History( old_dset , new_dset ) ;
    tross_Append_History( new_dset , his ) ;
    free(his) ;

This is for a plugin that is manipulating the input "old_dset" to
create the output "new_dset".  This example is drawn directly from
plug_power.c (the Power Spectrum plugin).
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