/*
 * Copyright (C) by Argonne National Laboratory
 *     See COPYRIGHT in top-level directory
 */

#include "adio.h"

/* returns the current location of the shared_fp in terms of the
   no. of etypes relative to the current view, and also increments the
   shared_fp by the number of etypes to be accessed (incr) in the read
   or write following this function. */

void ADIOI_NFS_Get_shared_fp(ADIO_File fd, ADIO_Offset incr, ADIO_Offset * shared_fp,
                             int *error_code);

void ADIO_Get_shared_fp(ADIO_File fd, ADIO_Offset incr, ADIO_Offset * shared_fp, int *error_code)
{
    ADIO_Status status;
    ADIO_Offset new_fp;
    MPI_Comm dupcommself;

    /* Set the shared_fp in case this comes from an uninitialized stack variable
     * The read routines will not read into the address of this variable if the file
     * size of a shared pointer is 0, and if incr is always zero, this value will remain
     * uninitialized.  Initialize it here to prevent incorrect values
     */
    *shared_fp = 0;

#ifdef ROMIO_NFS
    if (fd->file_system == ADIO_NFS) {
        ADIOI_NFS_Get_shared_fp(fd, incr, shared_fp, error_code);
        return;
    }
#endif

    if (fd->shared_fp_fd == ADIO_FILE_NULL) {
        MPI_Comm_dup(MPI_COMM_SELF, &dupcommself);
        fd->shared_fp_fd = ADIO_Open(MPI_COMM_SELF, dupcommself,
                                     fd->shared_fp_fname,
                                     fd->file_system,
                                     fd->fns,
                                     ADIO_CREATE | ADIO_RDWR | ADIO_DELETE_ON_CLOSE,
                                     0, MPI_BYTE, MPI_BYTE,
                                     MPI_INFO_NULL, ADIO_PERM_NULL, error_code);
        if (*error_code != MPI_SUCCESS)
            return;
        ADIOI_WRITE_LOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
        ADIO_ReadContig(fd->shared_fp_fd, shared_fp, sizeof(ADIO_Offset),
                        MPI_BYTE, ADIO_EXPLICIT_OFFSET, 0, &status, error_code);
        /* if the file is empty, the above function may return error
         * (reading beyond end of file). In that case, shared_fp = 0,
         * set above, is the correct value. */
    } else {
        ADIOI_WRITE_LOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
        ADIO_ReadContig(fd->shared_fp_fd, shared_fp, sizeof(ADIO_Offset),
                        MPI_BYTE, ADIO_EXPLICIT_OFFSET, 0, &status, error_code);
        if (*error_code != MPI_SUCCESS) {
            ADIOI_UNLOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
            return;
        }
    }

    if (incr == 0) {
        goto done;
    }

    new_fp = *shared_fp + incr;

    ADIO_WriteContig(fd->shared_fp_fd, &new_fp, sizeof(ADIO_Offset),
                     MPI_BYTE, ADIO_EXPLICIT_OFFSET, 0, &status, error_code);
  done:
    ADIOI_UNLOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
}
