/* -*- 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"

/* Returns the absolute byte position in the file corresponding to
   "offset" etypes relative to the current view. */

void ADIOI_Get_byte_offset(ADIO_File fd, ADIO_Offset offset, ADIO_Offset * disp)
{
    ADIOI_Flatlist_node *flat_file;
    int i;
    ADIO_Offset n_filetypes, etype_in_filetype, sum, abs_off_in_filetype = 0, size_in_filetype;
    MPI_Count n_etypes_in_filetype, filetype_size, etype_size;
    int filetype_is_contig;
    MPI_Aint filetype_extent;

    ADIOI_Datatype_iscontig(fd->filetype, &filetype_is_contig);
    etype_size = fd->etype_size;

    if (filetype_is_contig)
        *disp = fd->disp + etype_size * offset;
    else {
        flat_file = ADIOI_Flatten_and_find(fd->filetype);

        MPI_Type_size_x(fd->filetype, &filetype_size);
        n_etypes_in_filetype = filetype_size / etype_size;
        n_filetypes = offset / n_etypes_in_filetype;
        etype_in_filetype = offset % n_etypes_in_filetype;
        size_in_filetype = etype_in_filetype * etype_size;

        sum = 0;
        for (i = 0; i < flat_file->count; i++) {
            sum += flat_file->blocklens[i];
            if (sum > size_in_filetype) {
                abs_off_in_filetype = flat_file->indices[i] +
                    size_in_filetype - (sum - flat_file->blocklens[i]);
                break;
            }
        }

        /* abs. offset in bytes in the file */
        MPI_Type_extent(fd->filetype, &filetype_extent);
        *disp =
            fd->disp + n_filetypes * ADIOI_AINT_CAST_TO_OFFSET filetype_extent +
            abs_off_in_filetype;
    }
}
