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

#include "ad_nfs.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)
{
    ADIO_Offset new_fp;
    ssize_t err;
    MPI_Comm dupcommself;
    static char myname[] = "ADIOI_NFS_GET_SHARED_FP";

    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;
        *shared_fp = 0;
        ADIOI_WRITE_LOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
#ifdef ADIOI_MPE_LOGGING
        MPE_Log_event(ADIOI_MPE_read_a, 0, NULL);
#endif
        err = read(fd->shared_fp_fd->fd_sys, shared_fp, sizeof(ADIO_Offset));
#ifdef ADIOI_MPE_LOGGING
        MPE_Log_event(ADIOI_MPE_read_b, 0, NULL);
#endif
        /* if the file is empty, the above read 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));

#ifdef ADIOI_MPE_LOGGING
        MPE_Log_event(ADIOI_MPE_lseek_a, 0, NULL);
#endif
        err = lseek(fd->shared_fp_fd->fd_sys, 0, SEEK_SET);
#ifdef ADIOI_MPE_LOGGING
        MPE_Log_event(ADIOI_MPE_lseek_b, 0, NULL);
#endif
        if (err == 0) {
#ifdef ADIOI_MPE_LOGGING
            MPE_Log_event(ADIOI_MPE_read_a, 0, NULL);
#endif
            err = read(fd->shared_fp_fd->fd_sys, shared_fp, sizeof(ADIO_Offset));
#ifdef ADIOI_MPE_LOGGING
            MPE_Log_event(ADIOI_MPE_read_b, 0, NULL);
#endif
        }
        if (err == -1) {
            ADIOI_UNLOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
            *error_code = MPIO_Err_create_code(MPI_SUCCESS,
                                               MPIR_ERR_RECOVERABLE, myname,
                                               __LINE__, MPI_ERR_IO, "**io",
                                               "**io %s", strerror(errno));
            return;
        }
    }

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

    new_fp = *shared_fp + incr;

#ifdef ADIOI_MPE_LOGGING
    MPE_Log_event(ADIOI_MPE_lseek_a, 0, NULL);
#endif
    err = lseek(fd->shared_fp_fd->fd_sys, 0, SEEK_SET);
#ifdef ADIOI_MPE_LOGGING
    MPE_Log_event(ADIOI_MPE_lseek_b, 0, NULL);
#endif
    if (err == 0) {
#ifdef ADIOI_MPE_LOGGING
        MPE_Log_event(ADIOI_MPE_write_a, 0, NULL);
#endif
        err = write(fd->shared_fp_fd->fd_sys, &new_fp, sizeof(ADIO_Offset));
#ifdef ADIOI_MPE_LOGGING
        MPE_Log_event(ADIOI_MPE_write_b, 0, NULL);
#endif
    }
  done:
    ADIOI_UNLOCK(fd->shared_fp_fd, 0, SEEK_SET, sizeof(ADIO_Offset));
    if (err == -1) {
        *error_code = MPIO_Err_create_code(MPI_SUCCESS, MPIR_ERR_RECOVERABLE,
                                           myname, __LINE__, MPI_ERR_IO,
                                           "**io", "**io %s", strerror(errno));
    } else
        *error_code = MPI_SUCCESS;
}
