MERGE SORT IMPLEMENTATION
=========================

Praveen Sampath
prvn.exe@gmail.com

The main sort method is present in the file sort.c.
This method depends on other auxiliary methods defined in sort.c and a 
heap implementation in heap.h and heap.c.


Compilation
-----------

$ make sort

Usage
-----

Usage: ./sort [-o output_file] [-b buffer_size] [-a attr_list] input_file

The only required argument is the input file name.

Options:
	
	-o output_file
		Specify output file name. If not specified, the sorted data is written to 'output.bin'.

	-b buffer_size
		Set the buffer size (in bytes). The default buffer size is 100000 bytes.

	-a attr_list
		Specify the attributes to be considered for sorting, separated by comma.
		E.g., -a 3,4 or -a 8,4,-3.
		There should be NO SPACE between attribute index and the comma.
		If no attribute list is supplied, the data is sorted on the first column.

Data file format
----------------

The input data file (the file to be sorted) is a binary file that is structured as follows:

Metadata

4 byte unsigned int:  number of attributes  (n) 
followed by metadata of n attributes, each of the form 
    type (4 bytes), length (4 bytes) 
    Type is one of the following:  1: int, 2: double, 3: char (fixed length) 

Data

Records are fixed length.

Refer to the sort function in sort.c to see how the metadata and data are read from the input binary file