Developement.doc

                Development notes for Wgrib2      1/2004



Every option for wgrib is now a function call.  (Eventually some
options will be macros; for example, -s = -var -d etc.)  I went
to this approach for

  (1) ease of development
  (2) ease of extendability
  (3) more versatile

People kept making mods for wgrib, so I wanted a system where you
just drop in the code and compile.  


Steps to add a new option/function:

  (1) decide on the type of function
      currently inv (inventory) - writes to stdout, no access to decoded data
                output - writes to stdout, dump-file, access to decoded data
		setup - no access to decoded data

  (2) write function
	functions are called several times
	a) first with mode == -1 (initialization stop)
	b) for each data field (mode = 0 or mode = 1 verbose)
	c) finishing with mode = -2 (finializing step)

  (3) write header in the source code
	format is
		* HEADER:sort_order:name:type:number_args:description
	ex      * HEADER:100:d:inv:0:date YYYYMMDDHH

     For the name of the function and calling args, see
	documentation in wgrib2

To compile

	./function.sh		updates the option table
	./compile		compiles the code