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/* -*- 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"
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
ADIO_Offset ADIOI_GEN_SeekIndividual(ADIO_File fd, ADIO_Offset offset,
int whence, int *error_code)
{
/* implemented for whence=SEEK_SET only. SEEK_CUR and SEEK_END must
be converted to the equivalent with SEEK_SET before calling this
routine. */
/* offset is in units of etype relative to the filetype */
ADIO_Offset off;
ADIOI_Flatlist_node *flat_file;
int i;
ADIO_Offset n_etypes_in_filetype, n_filetypes, etype_in_filetype;
ADIO_Offset abs_off_in_filetype=0;
ADIO_Offset size_in_filetype, sum;
MPI_Count filetype_size, etype_size;
int filetype_is_contig;
MPI_Aint filetype_extent;
ADIOI_UNREFERENCED_ARG(whence);
ADIOI_Datatype_iscontig(fd->filetype, &filetype_is_contig);
etype_size = fd->etype_size;
if (filetype_is_contig) off = fd->disp + etype_size * offset;
else {
flat_file = ADIOI_Flatlist;
while (flat_file->type != fd->filetype) flat_file = flat_file->next;
MPI_Type_extent(fd->filetype, &filetype_extent);
MPI_Type_size_x(fd->filetype, &filetype_size);
if ( ! filetype_size ) {
/* Since offset relative to the filetype size, we can't
do compute the offset when that result is zero.
Return zero for the offset for now */
*error_code = MPI_SUCCESS;
return 0;
}
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 */
off = fd->disp + n_filetypes * filetype_extent +
abs_off_in_filetype;
}
/*
* we used to call lseek here and update both fp_ind and fp_sys_posn, but now
* we don't seek and only update fp_ind (ROMIO's idea of where we are in the
* file). We leave the system file descriptor and fp_sys_posn alone.
* The fs-specifc ReadContig and WriteContig will seek to the correct place in
* the file before reading/writing if the 'offset' parameter doesn't match
* fp_sys_posn
*/
fd->fp_ind = off;
*error_code = MPI_SUCCESS;
return off;
}
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