/* -*- Mode: C; c-basic-offset:4 ; indent-tabs-mode:nil ; -*- */
/*
 *
 *   Copyright (C) 1997 University of Chicago.
 *   See COPYRIGHT notice in top-level directory.
 */

#include "adio.h"
#include "adio_extern.h"

int ADIO_Type_create_subarray(int ndims,
			      int *array_of_sizes,
			      int *array_of_subsizes,
			      int *array_of_starts,
			      int order,
			      MPI_Datatype oldtype,
			      MPI_Datatype *newtype)
{
    MPI_Aint extent, disps[3], size;
    int i, blklens[3];
    MPI_Datatype tmp1, tmp2, types[3];

    MPI_Type_extent(oldtype, &extent);

    if (order == MPI_ORDER_FORTRAN) {
	/* dimension 0 changes fastest */
	if (ndims == 1) {
	    MPI_Type_contiguous(array_of_subsizes[0], oldtype, &tmp1);
	}
	else {
	    MPI_Type_vector(array_of_subsizes[1],
			    array_of_subsizes[0],
			    array_of_sizes[0], oldtype, &tmp1);

	    size = (MPI_Aint)array_of_sizes[0]*extent;
	    for (i=2; i<ndims; i++) {
		size *= (MPI_Aint)array_of_sizes[i-1];
		MPI_Type_hvector(array_of_subsizes[i], 1, size, tmp1, &tmp2);
		MPI_Type_free(&tmp1);
		tmp1 = tmp2;
	    }
	}

	/* add displacement and UB */
	disps[1] = array_of_starts[0];
	size = 1;
	for (i=1; i<ndims; i++) {
	    size *= (MPI_Aint)array_of_sizes[i-1];
	    disps[1] += size*(MPI_Aint)array_of_starts[i];
	}
        /* rest done below for both Fortran and C order */
    }

    else /* order == MPI_ORDER_C */ {
	/* dimension ndims-1 changes fastest */
	if (ndims == 1) {
	    MPI_Type_contiguous(array_of_subsizes[0], oldtype, &tmp1);
	}
	else {
	    MPI_Type_vector(array_of_subsizes[ndims-2],
			    array_of_subsizes[ndims-1],
			    array_of_sizes[ndims-1], oldtype, &tmp1);

	    size = (MPI_Aint)array_of_sizes[ndims-1]*extent;
	    for (i=ndims-3; i>=0; i--) {
		size *= (MPI_Aint)array_of_sizes[i+1];
		MPI_Type_hvector(array_of_subsizes[i], 1, size, tmp1, &tmp2);
		MPI_Type_free(&tmp1);
		tmp1 = tmp2;
	    }
	}

	/* add displacement and UB */
	disps[1] = array_of_starts[ndims-1];
	size = 1;
	for (i=ndims-2; i>=0; i--) {
	    size *= (MPI_Aint)array_of_sizes[i+1];
	    disps[1] += size*(MPI_Aint)array_of_starts[i];
	}
    }

    disps[1] *= extent;

    disps[2] = extent;
    for (i=0; i<ndims; i++) disps[2] *= (MPI_Aint)array_of_sizes[i];

    disps[0] = 0;
    blklens[0] = blklens[1] = blklens[2] = 1;
    types[0] = MPI_LB;
    types[1] = tmp1;
    types[2] = MPI_UB;

    MPI_Type_struct(3, blklens, disps, types, newtype);

    MPI_Type_free(&tmp1);

    return MPI_SUCCESS;
}
