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libs/ck-libs/ampi/romio/adio/ad_xfs/ad_xfs_read.c

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/* -*- Mode: C; c-basic-offset:4 ; -*- */
/* 
 *   $Id$    
 *
 *   Copyright (C) 1997 University of Chicago. 
 *   See COPYRIGHT notice in top-level directory.
 */

#include "ad_xfs.h"

static void ADIOI_XFS_Aligned_Mem_File_Read(ADIO_File fd, void *buf, int len, 
                                             ADIO_Offset offset, int *err);

void ADIOI_XFS_ReadContig(ADIO_File fd, void *buf, int count, 
                     MPI_Datatype datatype, int file_ptr_type,
                     ADIO_Offset offset, ADIO_Status *status, int *error_code)
{
    int err=-1, datatype_size, len, diff, size, nbytes;
    void *newbuf;
#ifndef PRINT_ERR_MSG
    static char myname[] = "ADIOI_XFS_READCONTIG";
#endif

    MPI_Type_size(datatype, &datatype_size);
    len = datatype_size * count;

    fd->fp_sys_posn = -1; /* set it to null, since we are using pread */

    if (file_ptr_type == ADIO_INDIVIDUAL) offset = fd->fp_ind;

    if (!(fd->direct_read))     /* direct I/O not enabled */
        err = pread(fd->fd_sys, buf, len, offset);
    else {       /* direct I/O enabled */

        /* (1) if mem_aligned && file_aligned 
                    use direct I/O to read up to correct io_size
                    use buffered I/O for remaining  */

        if (!(((long) buf) % fd->d_mem) && !(offset % fd->d_miniosz)) 
            ADIOI_XFS_Aligned_Mem_File_Read(fd, buf, len, offset, &err);

        /* (2) if !file_aligned
                    use buffered I/O to read up to file_aligned
                    At that point, if still mem_aligned, use (1)
                        else copy into aligned buf and then use (1) */
        else if (offset % fd->d_miniosz) {
            diff = fd->d_miniosz - (offset % fd->d_miniosz);
            diff = ADIOI_MIN(diff, len);
            nbytes = pread(fd->fd_sys, buf, diff, offset);

            buf = ((char *) buf) + diff;
            offset += diff;
            size = len - diff;
            if (!(((long) buf) % fd->d_mem)) {
                ADIOI_XFS_Aligned_Mem_File_Read(fd, buf, size, offset, &err);
                nbytes += err;
            }
            else {
                newbuf = (void *) memalign(XFS_MEMALIGN, size);
                if (newbuf) {
                    ADIOI_XFS_Aligned_Mem_File_Read(fd, newbuf, size, offset, &err);
                    if (err > 0) memcpy(buf, newbuf, err);
                    nbytes += err;
                    free(newbuf);
                }
                else nbytes += pread(fd->fd_sys, buf, size, offset);
            }
            err = nbytes;
        }

        /* (3) if !mem_aligned && file_aligned
                    copy into aligned buf, then use (1)  */
        else {
            newbuf = (void *) memalign(XFS_MEMALIGN, len);
            if (newbuf) {
                ADIOI_XFS_Aligned_Mem_File_Read(fd, newbuf, len, offset, &err);
                if (err > 0) memcpy(buf, newbuf, err);
                free(newbuf);
            }
            else err = pread(fd->fd_sys, buf, len, offset);
        }
    }

    if (file_ptr_type == ADIO_INDIVIDUAL) fd->fp_ind += err;

#ifdef HAVE_STATUS_SET_BYTES
    if (err != -1) MPIR_Status_set_bytes(status, datatype, err);
#endif

#ifdef PRINT_ERR_MSG
    *error_code = (err == -1) ? MPI_ERR_UNKNOWN : MPI_SUCCESS;
#else
    if (err == -1) {
        *error_code = MPIR_Err_setmsg(MPI_ERR_IO, MPIR_ADIO_ERROR,
                              myname, "I/O Error", "%s", strerror(errno));
        ADIOI_Error(fd, *error_code, myname);
    }
    else *error_code = MPI_SUCCESS;
#endif
}


void ADIOI_XFS_Aligned_Mem_File_Read(ADIO_File fd, void *buf, int len, 
              ADIO_Offset offset, int *err)
{
    int ntimes, rem, newrem, i, size, nbytes;

    /* memory buffer is aligned, offset in file is aligned,
       io_size may or may not be of the right size.
       use direct I/O to read up to correct io_size,
       use buffered I/O for remaining. */

    if (!(len % fd->d_miniosz) && 
        (len >= fd->d_miniosz) && (len <= fd->d_maxiosz))
        *err = pread(fd->fd_direct, buf, len, offset);
    else if (len < fd->d_miniosz)
        *err = pread(fd->fd_sys, buf, len, offset);
    else if (len > fd->d_maxiosz) {
        ntimes = len/(fd->d_maxiosz);
        rem = len - ntimes * fd->d_maxiosz;
        nbytes = 0;
        for (i=0; i<ntimes; i++) {
            nbytes += pread(fd->fd_direct, ((char *)buf) + i * fd->d_maxiosz,
                         fd->d_maxiosz, offset);
            offset += fd->d_maxiosz;
        }
        if (rem) {
            if (!(rem % fd->d_miniosz))
                nbytes += pread(fd->fd_direct, 
                     ((char *)buf) + ntimes * fd->d_maxiosz, rem, offset);
            else {
                newrem = rem % fd->d_miniosz;
                size = rem - newrem;
                if (size) {
                    nbytes += pread(fd->fd_direct, 
                         ((char *)buf) + ntimes * fd->d_maxiosz, size, offset);
                    offset += size;
                }
                nbytes += pread(fd->fd_sys, 
                      ((char *)buf) + ntimes*fd->d_maxiosz + size, newrem, offset);
            }
        }
        *err = nbytes;
    }
    else {
        rem = len % fd->d_miniosz;
        size = len - rem;
        nbytes = pread(fd->fd_direct, buf, size, offset);
        nbytes += pread(fd->fd_sys, (char *)buf + size, rem, offset+size);
        *err = nbytes;
    }
}


void ADIOI_XFS_ReadStrided(ADIO_File fd, void *buf, int count,
                       MPI_Datatype datatype, int file_ptr_type,
                       ADIO_Offset offset, ADIO_Status *status, int
                       *error_code)
{
    ADIOI_GEN_ReadStrided(fd, buf, count, datatype, file_ptr_type,
                        offset, status, error_code);
}

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