Home Research Papers Posters Manuals Talks Download People Help Internal

libs/ck-libs/ampi/romio/adio/common/byte_offset.c

Go to the documentation of this file.

/* -*- Mode: C; c-basic-offset:4 ; -*- */
/* 
 *   $Id$    
 *
 *   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, sum, n_etypes_in_filetype, size_in_filetype;
    int n_filetypes, etype_in_filetype;
    ADIO_Offset abs_off_in_filetype=0;
    int filetype_size, etype_size, 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 {
/* filetype already flattened in ADIO_Open */
        flat_file = ADIOI_Flatlist;
        while (flat_file->type != fd->filetype) flat_file = flat_file->next;

        MPI_Type_size(fd->filetype, &filetype_size);
        n_etypes_in_filetype = filetype_size/etype_size;
        n_filetypes = (int) (offset / n_etypes_in_filetype);
        etype_in_filetype = (int) (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 + (ADIO_Offset) n_filetypes*filetype_extent + abs_off_in_filetype;
    }
}

---