path: root/src/H5AC.c

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF5.  The full HDF5 copyright notice, including     *
 * terms governing use, modification, and redistribution, is contained in    *
 * the files COPYING and Copyright.html.  COPYING can be found at the root   *
 * of the source code distribution tree; Copyright.html can be found at the  *
 * root level of an installed copy of the electronic HDF5 document set and   *
 * is linked from the top-level documents page.  It can also be found at     *
 * http://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html.  If you do not have     *
 * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/*-------------------------------------------------------------------------
 *
 * Created:             H5AC.c
 *                      Jul  9 1997
 *                      Robb Matzke <matzke@llnl.gov>
 *
 * Purpose:             Functions in this file implement a cache for
 *                      things which exist on disk.  All "things" associated
 *                      with a particular HDF file share the same cache; each
 *                      HDF file has it's own cache.
 *
 * Modifications:
 *
 *      Robb Matzke, 4 Aug 1997
 *      Added calls to H5E.
 *
 *      Quincey Koziol, 22 Apr 2000
 *      Turned on "H5AC_SORT_BY_ADDR"
 *
 *-------------------------------------------------------------------------
 */

#define H5F_PACKAGE		/*suppress error about including H5Fpkg	  */

/* Pablo information */
/* (Put before include files to avoid problems with inline functions) */
#define PABLO_MASK	H5AC_mask

#include "H5private.h"		/* Generic Functions			*/
#include "H5ACprivate.h"	/* Metadata cache			*/
#include "H5Dprivate.h"		/* Dataset functions			*/
#include "H5Eprivate.h"		/* Error handling		  	*/
#include "H5Fpkg.h"		/* Files				*/
#include "H5FDprivate.h"	/* File drivers				*/
#include "H5FLprivate.h"	/* Free Lists                           */
#include "H5Iprivate.h"		/* IDs			  		*/
#include "H5MMprivate.h"	/* Memory management			*/
#include "H5Pprivate.h"         /* Property lists                       */

/* Interface initialization */
static int             interface_initialize_g = 0;
#define INTERFACE_INIT H5AC_init_interface
static herr_t H5AC_init_interface(void);

/*
 * Private macros
 */

/* Hash an address in the file to an offset in the cache */
#define H5AC_HASH_DIVISOR 8     /* Attempt to spread out the hashing */
                                /* This should be the same size as the alignment of */
                                /* of the smallest file format object written to the file.  */
#define H5AC_HASH(F,ADDR) H5F_addr_hash((ADDR/H5AC_HASH_DIVISOR),(F)->shared->cache->nslots)

/*
 * Private typedefs & structs
 */

#ifdef H5AC_DEBUG
typedef struct H5AC_prot_t {
    int		nprots;		/*number of things protected	     */
    int		aprots;		/*nelmts of `prot' array	     */
    H5AC_info_t	**slot;		/*array of pointers to protected things	     */
} H5AC_prot_t;
#endif /* H5AC_DEBUG */

struct H5AC_t {
    unsigned	nslots;			/*number of cache slots		     */
    H5AC_info_t **slot;		/*the cache slots, an array of pointers to the cached objects */
    H5AC_info_t **dslot;	/*"held object" cache slots, an array of pointers to dirty cached objects */
#ifdef H5AC_DEBUG
    H5AC_prot_t *prot;		/*the protected slots		     */
#endif /* H5AC_DEBUG */
    int	nprots;			/*number of protected objects	     */
#ifdef H5AC_DEBUG
    struct {
	unsigned	nhits;			/*number of cache hits		     */
	unsigned	nmisses;		/*number of cache misses	     */
	unsigned	ninits;			/*number of cache inits		     */
	unsigned	nflushes;		/*number of flushes to disk	     */
#ifdef H5_HAVE_PARALLEL
	unsigned	ndestroys;		/*number of cache destroys	     */
	unsigned	nholds;			/*number of cache holds	     */
	unsigned	nrestores;		/*number of cache restores	     */
#endif /* H5_HAVE_PARALLEL */
    } diagnostics[H5AC_NTYPES];		/*diagnostics for each type of object*/
#endif /* H5AC_DEBUG */
};

/*
 * Private file-scope variables.
 */

/* Default dataset transfer property list for metadata I/O calls */
/* (Collective set, "block before metadata write" set and "library internal" set) */
/* (Global variable definition, declaration is in H5ACprivate.h also) */
hid_t H5AC_dxpl_id=(-1);

/* Private dataset transfer property list for metadata I/O calls */
/* (Collective set and "library internal" set) */
/* (Static variable definition) */
static hid_t H5AC_noblock_dxpl_id=(-1);

/* Dataset transfer property list for independent metadata I/O calls */
/* (just "library internal" set - i.e. independent transfer mode) */
/* (Global variable definition, declaration is in H5ACprivate.h also) */
hid_t H5AC_ind_dxpl_id=(-1);

static H5AC_t          *current_cache_g = NULL;         /*for sorting */

/* Declare a free list to manage the H5AC_t struct */
H5FL_DEFINE_STATIC(H5AC_t);

/* Declare a PQ free list to manage the cache mapping array information */
H5FL_ARR_DEFINE_STATIC(unsigned,-1);

/* Declare a PQ free list to manage the cache slot array information */
H5FL_ARR_DEFINE_STATIC(H5AC_info_ptr_t,-1);

#ifdef H5AC_DEBUG
/* Declare a PQ free list to manage the protected slot array information */
H5FL_ARR_DEFINE_STATIC(H5AC_prot_t,-1);
#endif /* H5AC_DEBUG */


/*-------------------------------------------------------------------------
 * Function:	H5AC_init
 *
 * Purpose:	Initialize the interface from some other layer.
 *
 * Return:	Success:	non-negative
 *
 *		Failure:	negative
 *
 * Programmer:	Quincey Koziol
 *              Saturday, January 18, 2003
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_init(void)
{
    herr_t ret_value=SUCCEED;   /* Return value */

    FUNC_ENTER_NOAPI(H5AC_init, FAIL)
    /* FUNC_ENTER() does all the work */

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:	H5AC_init_interface
 *
 * Purpose:	Initialize interface-specific information
 *
 * Return:	Non-negative on success/Negative on failure
 *
 * Programmer:	Quincey Koziol
 *              Thursday, July 18, 2002
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static herr_t
H5AC_init_interface(void)
{
    H5P_genclass_t  *xfer_pclass;   /* Dataset transfer property list class object */
#ifdef H5_HAVE_PARALLEL
    H5P_genplist_t  *xfer_plist;    /* Dataset transfer property list object */
    unsigned block_before_meta_write; /* "block before meta write" property value */
    unsigned library_internal=1;    /* "library internal" property value */
    H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */
#endif /* H5_HAVE_PARALLEL */
    herr_t ret_value=SUCCEED;           /* Return value */

    FUNC_ENTER_NOINIT(H5AC_init_interface)

    /* Sanity check */
    assert(H5P_CLS_DATASET_XFER_g!=(-1));

    /* Get the dataset transfer property list class object */
    if (NULL == (xfer_pclass = H5I_object(H5P_CLS_DATASET_XFER_g)))
        HGOTO_ERROR(H5E_CACHE, H5E_BADATOM, FAIL, "can't get property list class")

    /* Get an ID for the blocking, collective H5AC dxpl */
    if ((H5AC_dxpl_id=H5P_create_id(xfer_pclass)) < 0)
        HGOTO_ERROR(H5E_CACHE, H5E_CANTCREATE, FAIL, "unable to register property list")

#ifdef H5_HAVE_PARALLEL
    /* Get the property list object */
    if (NULL == (xfer_plist = H5I_object(H5AC_dxpl_id)))
        HGOTO_ERROR(H5E_CACHE, H5E_BADATOM, FAIL, "can't get new property list object")

    /* Insert 'block before metadata write' property */
    block_before_meta_write=1;
    if(H5P_insert(xfer_plist,H5AC_BLOCK_BEFORE_META_WRITE_NAME,H5AC_BLOCK_BEFORE_META_WRITE_SIZE,&block_before_meta_write,NULL,NULL,NULL,NULL,NULL)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't insert metadata cache dxpl property")

    /* Insert 'library internal' property */
    if(H5P_insert(xfer_plist,H5AC_LIBRARY_INTERNAL_NAME,H5AC_LIBRARY_INTERNAL_SIZE,&library_internal,NULL,NULL,NULL,NULL,NULL)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't insert metadata cache dxpl property")

    /* Set the transfer mode */
    xfer_mode=H5FD_MPIO_COLLECTIVE;
    if (H5P_set(xfer_plist,H5D_XFER_IO_XFER_MODE_NAME,&xfer_mode)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")
#endif /* H5_HAVE_PARALLEL */

    /* Get an ID for the non-blocking, collective H5AC dxpl */
    if ((H5AC_noblock_dxpl_id=H5P_create_id(xfer_pclass)) < 0)
        HGOTO_ERROR(H5E_CACHE, H5E_CANTCREATE, FAIL, "unable to register property list")

#ifdef H5_HAVE_PARALLEL
    /* Get the property list object */
    if (NULL == (xfer_plist = H5I_object(H5AC_noblock_dxpl_id)))
        HGOTO_ERROR(H5E_CACHE, H5E_BADATOM, FAIL, "can't get new property list object")

    /* Insert 'block before metadata write' property */
    block_before_meta_write=0;
    if(H5P_insert(xfer_plist,H5AC_BLOCK_BEFORE_META_WRITE_NAME,H5AC_BLOCK_BEFORE_META_WRITE_SIZE,&block_before_meta_write,NULL,NULL,NULL,NULL,NULL)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't insert metadata cache dxpl property")

    /* Insert 'library internal' property */
    if(H5P_insert(xfer_plist,H5AC_LIBRARY_INTERNAL_NAME,H5AC_LIBRARY_INTERNAL_SIZE,&library_internal,NULL,NULL,NULL,NULL,NULL)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't insert metadata cache dxpl property")

    /* Set the transfer mode */
    xfer_mode=H5FD_MPIO_COLLECTIVE;
    if (H5P_set(xfer_plist,H5D_XFER_IO_XFER_MODE_NAME,&xfer_mode)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")
#endif /* H5_HAVE_PARALLEL */

    /* Get an ID for the non-blocking, independent H5AC dxpl */
    if ((H5AC_ind_dxpl_id=H5P_create_id(xfer_pclass)) < 0)
        HGOTO_ERROR(H5E_CACHE, H5E_CANTCREATE, FAIL, "unable to register property list")

#ifdef H5_HAVE_PARALLEL
    /* Get the property list object */
    if (NULL == (xfer_plist = H5I_object(H5AC_ind_dxpl_id)))
        HGOTO_ERROR(H5E_CACHE, H5E_BADATOM, FAIL, "can't get new property list object")

    /* Insert 'block before metadata write' property */
    block_before_meta_write=0;
    if(H5P_insert(xfer_plist,H5AC_BLOCK_BEFORE_META_WRITE_NAME,H5AC_BLOCK_BEFORE_META_WRITE_SIZE,&block_before_meta_write,NULL,NULL,NULL,NULL,NULL)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't insert metadata cache dxpl property")

    /* Insert 'library internal' property */
    if(H5P_insert(xfer_plist,H5AC_LIBRARY_INTERNAL_NAME,H5AC_LIBRARY_INTERNAL_SIZE,&library_internal,NULL,NULL,NULL,NULL,NULL)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't insert metadata cache dxpl property")

    /* Set the transfer mode */
    xfer_mode=H5FD_MPIO_INDEPENDENT;
    if (H5P_set(xfer_plist,H5D_XFER_IO_XFER_MODE_NAME,&xfer_mode)<0)
        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")
#endif /* H5_HAVE_PARALLEL */

done:
    FUNC_LEAVE_NOAPI(ret_value)
} /* end H5AC_init_interface() */


/*-------------------------------------------------------------------------
 * Function:	H5AC_term_interface
 *
 * Purpose:	Terminate this interface.
 *
 * Return:	Success:	Positive if anything was done that might
 *				affect other interfaces; zero otherwise.
 *
 * 		Failure:	Negative.
 *
 * Programmer:	Quincey Koziol
 *              Thursday, July 18, 2002
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
int
H5AC_term_interface(void)
{
    int		n=0;

    FUNC_ENTER_NOINIT(H5AC_term_interface)

    if (interface_initialize_g) {
        if(H5AC_dxpl_id>0 || H5AC_noblock_dxpl_id>0 || H5AC_ind_dxpl_id>0) {
            /* Indicate more work to do */
            n = 1; /* H5I */

            /* Close H5AC dxpl */
            if (H5Pclose(H5AC_dxpl_id) < 0 ||
                    H5Pclose(H5AC_noblock_dxpl_id) < 0 ||
                    H5Pclose(H5AC_ind_dxpl_id) < 0)
                H5E_clear(); /*ignore the error*/
            else {
                /* Reset static IDs */
                H5AC_dxpl_id=(-1);
                H5AC_noblock_dxpl_id=(-1);
                H5AC_ind_dxpl_id=(-1);

                /* Reset interface initialization flag */
                interface_initialize_g = 0;
            } /* end else */
        } /* end if */
        else
            /* Reset interface initialization flag */
            interface_initialize_g = 0;
    } /* end if */

    FUNC_LEAVE_NOAPI(n)
} /* end H5AC_term_interface() */


/*-------------------------------------------------------------------------
 * Function:    H5AC_create
 *
 * Purpose:     Initialize the cache just after a file is opened.  The
 *              SIZE_HINT is the number of cache slots desired.  If you
 *              pass an invalid value then H5AC_NSLOTS is used.  You can
 *              turn off caching by using 1 for the SIZE_HINT value.
 *
 * Return:      Success:        Number of slots actually used.
 *
 *              Failure:        Negative
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Jul  9 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
int
H5AC_create(const H5F_t *f, int size_hint)
{
    H5AC_t                 *cache = NULL;
    int ret_value;      /* Return value */

    FUNC_ENTER_NOAPI(H5AC_create, FAIL)

    assert(f);
    assert(NULL == f->shared->cache);

    /* If size hint is negative, use the default size */
    if (size_hint < 1)
        size_hint = H5AC_NSLOTS;

    if (NULL==(f->shared->cache = cache = H5FL_CALLOC(H5AC_t)))
	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
    cache->nslots = (unsigned)size_hint;
    if (NULL==( cache->slot = H5FL_ARR_CALLOC(H5AC_info_ptr_t,cache->nslots)))
        HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
    if (NULL==( cache->dslot = H5FL_ARR_CALLOC(H5AC_info_ptr_t,cache->nslots)))
        HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
#ifdef H5AC_DEBUG
    if ((cache->prot = H5FL_ARR_CALLOC(H5AC_prot_t,cache->nslots))==NULL)
        HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
#endif /* H5AC_DEBUG */

    /* Set return value */
    ret_value=size_hint;

done:
    if(ret_value<0) {
        if(cache!=NULL) {
            if(cache->dslot !=NULL)
                cache->dslot = H5FL_ARR_FREE (H5AC_info_ptr_t,cache->dslot);
            if(cache->slot !=NULL)
                cache->slot = H5FL_ARR_FREE (H5AC_info_ptr_t,cache->slot);
#ifdef H5AC_DEBUG
            if(cache->prot !=NULL)
                cache->prot = H5FL_ARR_FREE (H5AC_prot_t,cache->prot);
#endif /* H5AC_DEBUG */
            f->shared->cache = H5FL_FREE (H5AC_t,f->shared->cache);
        } /* end if */
    } /* end if */

    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_dest
 *
 * Purpose:     Flushes all data to disk and destroys the cache.
 *              This function fails if any object are protected since the
 *              resulting file might not be consistent.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Jul  9 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_dest(H5F_t *f, hid_t dxpl_id)
{
    H5AC_t *cache = NULL;
    herr_t ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI(H5AC_dest, FAIL)

    assert(f);
    assert(f->shared->cache);
    cache = f->shared->cache;

    if (H5AC_flush(f, dxpl_id, NULL, HADDR_UNDEF, H5F_FLUSH_INVALIDATE) < 0)
        HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush cache")

#ifdef H5AC_DEBUG
    {
        unsigned i;
        for (i=0; i<cache->nslots; i++) {
            cache->prot[i].slot = H5MM_xfree(cache->prot[i].slot);
            cache->prot[i].aprots = 0;
            cache->prot[i].nprots = 0;
        }
        cache->prot = H5FL_ARR_FREE(H5AC_prot_t,cache->prot);
    }
#endif

    cache->dslot = H5FL_ARR_FREE(H5AC_info_ptr_t,cache->dslot);
    cache->slot = H5FL_ARR_FREE(H5AC_info_ptr_t,cache->slot);
    cache->nslots = 0;
    f->shared->cache = cache = H5FL_FREE(H5AC_t,cache);

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_find
 *
 * Purpose:     Given an object type and the address at which that object
 *              is located in the file, return a pointer to the object.
 *              The optional UDATA1 and UDATA2 structures are passed down to
 *              the function that is responsible for loading the object into
 *              memory.
 *
 *              The returned pointer is guaranteed to be valid until the next
 *              call to an H5AC function (if you want a pointer which is valid
 *              indefinately then see H5AC_protect()).
 *
 *              If H5AC_DEBUG is defined then this function also
 *              checks that the requested object is not currently
 *              protected since it is illegal to modify a protected object
 *              except through the pointer returned by H5AC_protect().
 *
 * Return:      Success:        Pointer to the object.  The pointer is
 *                              valid until some other cache function
 *                              is called.
 *
 *              Failure:        NULL
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Jul  9 1997
 *
 * Modifications:
 *
 *      Robb Matzke, 4 Aug 1997
 *      Fails immediately if the cached object is at the correct address
 *      but is of the wrong type.  This happens if the caller doesn't know
 *      what type of object is at the address and calls this function with
 *      various type identifiers until one succeeds (cf., the debugger).
 *
 *      Robb Matzke, 30 Oct 1997
 *      Keeps track of hits, misses, and flushes per object type so we have
 *      some cache performance diagnostics.
 *
 * 	Robb Matzke, 1999-07-27
 *	The ADDR argument is passed by value.
 *
 *-------------------------------------------------------------------------
 */
void *
H5AC_find(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type, haddr_t addr,
	    const void *udata1, void *udata2)
{
    unsigned                idx;
    void                   *thing;
    H5AC_flush_func_t       flush;
    H5AC_info_t           **info;
#ifdef H5_HAVE_PARALLEL
    H5AC_info_t           **dinfo = NULL;
#endif /* H5_HAVE_PARALLEL */
    H5AC_t                 *cache;
    void                   *ret_value;          /* Return value */

    FUNC_ENTER_NOAPI(H5AC_find, NULL)

    assert(f);
    assert(f->shared->cache);
    assert(type);
    assert(type->load);
    assert(type->flush);
    assert(H5F_addr_defined(addr));

    /* Get local pointers to the file's cache information */
    idx = H5AC_HASH(f, addr);
    cache = f->shared->cache;
    info = cache->slot + idx;

#ifdef H5_HAVE_PARALLEL
    /* If MPI based VFD is used, do special parallel I/O actions */
    if(IS_H5FD_MPI(f)) {
        H5AC_dest_func_t        dest;

        /* Get local pointer to file's dirty cache information */
        dinfo = cache->dslot + idx;

        /* Check if the cache has 'held' information for this cache slot */
        if (*dinfo) {
            /* Sanity check that the 'clean' item is really clean */
            assert(*info);
            assert((*info)->dirty==0);

            /* Destroy 'current' information */
            dest = (*info)->type->dest;
            if ((dest)(f, (*info))<0)
                HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, NULL, "unable to free cached object")

            /* Restore 'held' information back to 'current' information */
            (*info)=(*dinfo);

            /* Clear 'held' information */
            (*dinfo)=NULL;

#ifdef H5AC_DEBUG
            cache->diagnostics[type->id].nrestores++;
#endif /* H5AC_DEBUG */
        } /* end if */
    } /* end if */
#endif /* H5_HAVE_PARALLEL */

    /*
     * Return right away if the item is in the cache.
     */
    if ((*info) && H5F_addr_eq(addr,(*info)->addr)
#ifdef H5AC_DEBUG
            && (*info)->type==type
#endif /* H5AC_DEBUG */
            ) {
#ifndef H5AC_DEBUG
        /* Sanity check that the object in the cache is the correct type */
        assert((*info)->type==type);
#endif /* H5AC_DEBUG */

#ifdef H5AC_DEBUG
        cache->diagnostics[type->id].nhits++;
#endif /* H5AC_DEBUG */
        HGOTO_DONE(*info)
    }
#ifdef H5AC_DEBUG
    cache->diagnostics[type->id].nmisses++;
#endif /* H5AC_DEBUG */

#ifdef H5AC_DEBUG
    /*
     * Check that the requested thing isn't protected, for protected things
     * can only be modified through the pointer already handed out by the
     * H5AC_protect() function.
     */
    {
        H5AC_prot_t            *prot = NULL;
        int                    i;

        prot = cache->prot + idx;
        for (i = 0; i < prot->nprots; i++) {
            assert(H5F_addr_ne(addr, prot->slot[i]->addr));
        }
    }
#endif /* H5AC_DEBUG */

    /*
     * Load a new thing.  If it can't be loaded, then return an error
     * without preempting anything.
     */
    if (NULL == (thing = (type->load)(f, dxpl_id, addr, udata1, udata2)))
        HGOTO_ERROR(H5E_CACHE, H5E_CANTLOAD, NULL, "unable to load object")

#ifdef H5_HAVE_PARALLEL
    /* If MPI based VFD is used, do special parallel I/O actions */
    if(IS_H5FD_MPI(f)) {
        H5P_genplist_t *dxpl;           /* Dataset transfer property list */
        H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */

        /* Get the dataset transfer property list */
        if (NULL == (dxpl = H5I_object(dxpl_id)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a dataset creation property list")

        /* Get the transfer mode property */
        if(H5P_get(dxpl, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, NULL, "can't retrieve xfer mode")

        /* Make certain there is no 'held' info for this slot */
        assert((*dinfo)==NULL);

        /* Must be using collective I/O to flush metadata in parallel */
        if(xfer_mode==H5FD_MPIO_INDEPENDENT) {
            /* Check if there is dirty metadata in this slot */
            if((*info) && (*info)->dirty) {
                /* 'Hold' the current metadata for later */
                (*dinfo)=(*info);

                /* Reset the 'current' metadata, so it doesn't get flushed */
                (*info)=NULL;

#ifdef H5AC_DEBUG
                cache->diagnostics[(*dinfo)->type->id].nholds++;
#endif /* H5AC_DEBUG */
            } /* end if */
        } /* end else */
    } /* end if */
#endif /* H5_HAVE_PARALLEL */

    /*
     * Flush & destroy the previous cache entry if there is one.
     */
    if (*info) {
#ifdef H5AC_DEBUG
        H5AC_subid_t type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

        flush = (*info)->type->flush;
        if ( (flush)(f, dxpl_id, TRUE, (*info)->addr, (*info)) < 0) {
            /*
             * The old thing could not be removed from the stack.
             * Release the new thing and fail.
             */
            if ((type->dest)(f, thing) < 0)
                HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, NULL, "unable to destroy just-loaded object")
            HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, NULL, "unable to flush existing cached object")
        }
#ifdef H5AC_DEBUG
        cache->diagnostics[type_id].nflushes++;
#endif /* H5AC_DEBUG */
    } /* end if */

    /*
     * Make the cache point to the new thing.
     */
    (*info)=thing;
    (*info)->type = type;
    (*info)->addr = addr;
    assert((*info)->dirty==0);  /* Should be clean after being loaded */

    /* Set the return value */
    ret_value=thing;

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_compare
 *
 * Purpose:     Compare two hash entries by address.  Unused entries are
 *              all equal to one another and greater than all used entries.
 *
 * Return:      Success:        -1, 0, 1
 *
 *              Failure:        never fails
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Aug 12 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
static int
H5AC_compare(const void *_a, const void *_b)
{
    unsigned               a = *((const unsigned *) _a);
    unsigned               b = *((const unsigned *) _b);
    H5AC_info_t           *slot_a;
    H5AC_info_t           *slot_b;
    int                    ret_value=0;

    /* Use FUNC_ENTER_NOINIT here to avoid performance issues */
    FUNC_ENTER_NOINIT(H5AC_compare)

    assert(current_cache_g);

    /* Create aliases for slots */
    slot_a=current_cache_g->slot[a];
    slot_b=current_cache_g->slot[b];

    assert(slot_a);
    assert(slot_b);
    assert(slot_a->type);
    assert(slot_b->type);

    if (slot_a->addr < slot_b->addr) {
        ret_value=(-1);
    } else if (slot_a->addr > slot_b->addr) {
        ret_value=1;
    }

    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_flush
 *
 * Purpose:     Flushes (and destroys if DESTROY is non-zero) the specified
 *              entry from the cache.  If the entry TYPE is CACHE_FREE and
 *              ADDR is HADDR_UNDEF then all types of entries are
 *              flushed. If TYPE is CACHE_FREE and ADDR is defined then
 *              whatever is cached at ADDR is flushed.  Otherwise the thing
 *              at ADDR is flushed if it is the correct type.
 *
 *              If there are protected objects they will not be flushed.
 *              However, an attempt will be made to flush all non-protected
 *              items before this function returns failure.
 *
 * Return:      Non-negative on success/Negative on failure if there was a
 *              request to flush all items and something was protected.
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Jul  9 1997
 *
 * Modifications:
 * 		Robb Matzke, 1999-07-27
 *		The ADDR argument is passed by value.
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_flush(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type, haddr_t addr, unsigned flags)
{
    herr_t                  status;
    H5AC_flush_func_t       flush=NULL; /* 'flush' callback for an object */
    H5AC_info_t           **info;
    unsigned               *map = NULL; /* Mapping of cache entries */
    hbool_t                 destroy=(flags&H5F_FLUSH_INVALIDATE)>0;     /* Flag for destroying objects */
    hbool_t                 clear_only=(flags&H5F_FLUSH_CLEAR_ONLY)>0;  /* Flag for only clearing objects */
    unsigned               nslots;
    H5AC_t                 *cache;
    unsigned                u;     /* Local index variable */
    herr_t ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI(H5AC_flush, FAIL)

    assert(f);
    assert(f->shared->cache);

    /* Get local copy of this information */
    cache = f->shared->cache;

    if (!H5F_addr_defined(addr)) {
        unsigned first_flush=1;     /* Indicate if this is the first flush */

        /*
         * Sort the cache entries by address since flushing them in
         * ascending order by address is much more efficient.
         */
        if (NULL==(map=H5FL_ARR_MALLOC(unsigned,cache->nslots)))
            HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed")
#ifdef H5_HAVE_PARALLEL
        /* If MPI based VFD is used, do special parallel I/O actions */
        if(IS_H5FD_MPI(f)) {
            H5AC_info_t       **dinfo;
#ifdef H5AC_DEBUG
            H5AC_subid_t        type_id;
#endif /* H5AC_DEBUG */
#ifndef NDEBUG
            H5P_genplist_t *dxpl;           /* Dataset transfer property list */
            H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */

            /* Get the dataset transfer property list */
            if (NULL == (dxpl = H5I_object(dxpl_id)))
                HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset creation property list")

            /* Get the transfer mode property */
            if(H5P_get(dxpl, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't retrieve xfer mode")

            /* Sanity check transfer mode */
            assert(xfer_mode==H5FD_MPIO_COLLECTIVE);
#endif /* NDEBUG */

            /* Create the mapping */
            for (u = nslots = 0; u < cache->nslots; u++) {
                info = cache->slot + u;
                dinfo = cache->dslot + u;

                /* Move dirty metadata from 'held' slots into 'regular' slots */
                if((*dinfo)!=NULL) {
                    H5AC_dest_func_t        dest;

                    /* Various sanity checks */
                    assert((*dinfo)->dirty);
                    assert((*info)!=NULL);
                    assert((*info)->dirty==0);

#ifdef H5AC_DEBUG
                    type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

                    /* Destroy 'current' information */
                    dest = (*info)->type->dest;
                    if ((dest)(f, (*info))<0)
                        HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "unable to free cached object")

                    /* Restore 'held' information back to 'current' information */
                    (*info)=(*dinfo);

                    /* Clear 'held' information */
                    (*dinfo)=NULL;

#ifdef H5AC_DEBUG
                    cache->diagnostics[type_id].nrestores++;
#endif /* H5AC_DEBUG */
                } /* end if */
                if ((*info))
                    map[nslots++] = u;
            } /* end for */
        } /* end if */
        else {
#endif /* H5_HAVE_PARALLEL */
            for (u = nslots = 0; u < cache->nslots; u++) { /*lint !e539 Positive indention is OK */
                if (cache->slot[u]!=NULL)
                    map[nslots++] = u;
            }
#ifdef H5_HAVE_PARALLEL
        } /* end else */
#endif /* H5_HAVE_PARALLEL */
        assert(NULL == current_cache_g);
        current_cache_g = cache;
        HDqsort(map, nslots, sizeof(unsigned), H5AC_compare);
        current_cache_g = NULL;
#ifndef NDEBUG
        for (u = 1; u < nslots; u++)
            assert(H5F_addr_lt(cache->slot[map[u - 1]]->addr, cache->slot[map[u]]->addr));
#endif

        /*
         * Look at all cache entries.
         */
        for (u = 0; u < nslots; u++) {
            info = cache->slot + map[u];
            assert(*info);
            if (!type || type == (*info)->type) {
#ifdef H5AC_DEBUG
                H5AC_subid_t type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

                /* Clear the dirty flag only, if requested */
                if(clear_only) {
                    /* Call the callback routine to clear all dirty flags for object */
                    if(((*info)->type->clear)(*info)<0)
                        HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to clear cache")
                } /* end if */
                else {
                    flush = (*info)->type->flush;

                    /* Only block for all the processes on the first piece of metadata */
                    if(first_flush && (*info)->dirty) {
                        status = (flush)(f, dxpl_id, destroy, (*info)->addr, (*info));
                        first_flush=0;
                    } /* end if */
                    else
                        status = (flush)(f, H5AC_noblock_dxpl_id, destroy, (*info)->addr, (*info));
                    if (status < 0)
                        HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush cache")
#ifdef H5AC_DEBUG
                    cache->diagnostics[type_id].nflushes++;
#endif /* H5AC_DEBUG */
                } /* end else */

                /* Destroy entry also, if asked */
                if (destroy)
                    (*info)= NULL;
            }
        }

        /*
         * If there are protected object then fail.  However, everything
         * else should have been flushed.
         */
        if (cache->nprots > 0)
            HGOTO_ERROR(H5E_CACHE, H5E_PROTECT, FAIL, "cache has protected items")
    } else {
        u = H5AC_HASH(f, addr);
        info = cache->slot + u;
#ifdef H5_HAVE_PARALLEL
        /* If MPI based VFD is used, do special parallel I/O actions */
        if(IS_H5FD_MPI(f)) {
            H5AC_info_t       **dinfo;
#ifdef H5AC_DEBUG
            H5AC_subid_t        type_id;
#endif /* H5AC_DEBUG */
#ifndef NDEBUG
            H5P_genplist_t *dxpl;           /* Dataset transfer property list */
            H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */

            /* Get the dataset transfer property list */
            if (NULL == (dxpl = H5I_object(dxpl_id)))
                HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset creation property list")

            /* Get the transfer mode property */
            if(H5P_get(dxpl, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't retrieve xfer mode")

            /* Sanity check transfer mode */
            assert(xfer_mode==H5FD_MPIO_COLLECTIVE);
#endif /* NDEBUG */

            dinfo = cache->dslot + u;

            /* Restore dirty metadata from 'held' slot to 'current' slot */
            if((*dinfo)!=NULL) {
                H5AC_dest_func_t        dest;

                /* Various sanity checks */
                assert((*dinfo)->dirty);
                assert((*info)!=NULL);
                assert((*info)->dirty==0);

#ifdef H5AC_DEBUG
                type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

                /* Destroy 'current' information */
                dest = (*info)->type->dest;
                if ((dest)(f, (*info))<0)
                    HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "unable to free cached object")

                /* Restore 'held' information back to 'current' information */
                (*info)=(*dinfo);

                /* Clear 'held' information */
                (*dinfo)=NULL;

#ifdef H5AC_DEBUG
                cache->diagnostics[type_id].nrestores++;
#endif /* H5AC_DEBUG */
            } /* end if */
        } /* end if */
#endif /* H5_HAVE_PARALLEL */
        if ((*info) && (!type || (*info)->type == type) &&
                H5F_addr_eq((*info)->addr, addr)) {
#ifdef H5AC_DEBUG
            H5AC_subid_t type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

            /*
             * Flush just this entry.
             */

            /* Clear the dirty flag only, if requested */
            if(clear_only) {
                /* Call the callback routine to clear all dirty flags for object */
                if(((*info)->type->clear)(*info)<0)
                    HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to clear cache")
            } /* end if */
            else {
                flush = (*info)->type->flush;
                if((flush)(f, dxpl_id, destroy, (*info)->addr, (*info)) < 0)
                    HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush object")
#ifdef H5AC_DEBUG
                cache->diagnostics[type_id].nflushes++;
#endif /* H5AC_DEBUG */
            } /* end else */

            /* Destroy entry also, if asked */
            if (destroy)
                (*info)= NULL;
        } /* end if */
    } /* end else */

done:
    if(map!=NULL)
        map = H5FL_ARR_FREE(unsigned,map);

    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_set
 *
 * Purpose:     Adds the specified thing to the cache.  The thing need not
 *              exist on disk yet, but it must have an address and disk
 *              space reserved.
 *
 *              If H5AC_DEBUG is defined then this function checks
 *              that the object being inserted isn't a protected object.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Jul  9 1997
 *
 * Modifications:
 * 		Robb Matzke, 1999-07-27
 *		The ADDR argument is passed by value.
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_set(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type, haddr_t addr, void *thing)
{
    unsigned                idx;
    H5AC_flush_func_t       flush;
    H5AC_info_t           **info;
    H5AC_t                 *cache;
    herr_t ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI(H5AC_set, FAIL)

    assert(f);
    assert(f->shared->cache);
    assert(type);
    assert(type->flush);
    assert(H5F_addr_defined(addr));
    assert(thing);

    /* Get local copy of this information */
    idx = H5AC_HASH(f, addr);
    cache = f->shared->cache;
    info = cache->slot + idx;

#ifdef H5AC_DEBUG
    {
        H5AC_prot_t            *prot = NULL;
        int                    i;

        prot = cache->prot + idx;
        for (i = 0; i < prot->nprots; i++)
            assert(H5F_addr_ne(addr, prot->slot[i]->addr));
    }
#endif

#ifdef H5_HAVE_PARALLEL
    /* If MPI based VFD is used, do special parallel I/O actions */
    if(IS_H5FD_MPI(f)) {
        H5AC_info_t       **dinfo;
#ifdef H5AC_DEBUG
        H5AC_subid_t        type_id;
#endif /* H5AC_DEBUG */
        H5P_genplist_t *dxpl;           /* Dataset transfer property list */
        H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */

        /* Get the dataset transfer property list */
        if (NULL == (dxpl = H5I_object(dxpl_id)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset creation property list")

        /* Get the transfer mode property */
        if(H5P_get(dxpl, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't retrieve xfer mode")

        /* Get pointer to 'held' information */
        dinfo = cache->dslot + idx;

        /* Sanity check transfer mode */
        if(xfer_mode==H5FD_MPIO_COLLECTIVE) {
            /* Check for dirty metadata */
            if(*dinfo) {
                H5AC_dest_func_t        dest;

                /* Various sanity checks */
                assert((*dinfo)->dirty);
                assert((*info)!=NULL);
                assert((*info)->dirty==0);

#ifdef H5AC_DEBUG
                type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

                /* Destroy 'current' information */
                dest = (*info)->type->dest;
                if ((dest)(f, (*info))<0)
                    HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "unable to free cached object")

                /* Restore 'held' information back to 'current' information */
                (*info)=(*dinfo);

                /* Clear 'held' information */
                (*dinfo)=NULL;

#ifdef H5AC_DEBUG
                cache->diagnostics[type_id].nrestores++;
#endif /* H5AC_DEBUG */
            } /* end if */
        } /* end if */
        else {
            /* Sanity check */
            assert((*dinfo)==NULL);
            assert(xfer_mode==H5FD_MPIO_INDEPENDENT);

            /* Make certain there will be no write of dirty metadata */
            if((*info) && (*info)->dirty) {
                /* Sanity check new item */
                assert(((H5AC_info_t*)thing)->dirty==0);

                /* 'Hold' the current metadata for later */
                (*dinfo)=(*info);

                /* Reset the 'current' metadata, so it doesn't get flushed */
                (*info)=NULL;

#ifdef H5AC_DEBUG
                cache->diagnostics[(*dinfo)->type->id].nholds++;
#endif /* H5AC_DEBUG */
            } /* end if */
        } /* end else */
    } /* end if */
#endif /* H5_HAVE_PARALLEL */

    /* Flush any object already in cache slot */
    if ((*info)) {
#ifdef H5AC_DEBUG
        H5AC_subid_t type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

        flush = (*info)->type->flush;
        if ((flush)(f, dxpl_id, TRUE, (*info)->addr, (*info)) < 0)
            HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush object")
#ifdef H5AC_DEBUG
        cache->diagnostics[type_id].nflushes++;
#endif /* H5AC_DEBUG */
    } /* end if */

    /* Cache this item */
    (*info)=thing;
    (*info)->type = type;
    (*info)->addr = addr;
#ifdef H5AC_DEBUG
    cache->diagnostics[type->id].ninits++;
#endif /* H5AC_DEBUG */

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_rename
 *
 * Purpose:     Use this function to notify the cache that an object's
 *              file address changed.
 *
 *              If H5AC_DEBUG is defined then this function checks
 *              that the old and new addresses don't correspond to the
 *              address of a protected object.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Jul  9 1997
 *
 * Modifications:
 * 		Robb Matzke, 1999-07-27
 *		The OLD_ADDR and NEW_ADDR arguments are passed by value.
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_rename(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type, haddr_t old_addr,
	    haddr_t new_addr)
{
    unsigned                old_idx, new_idx;
    H5AC_flush_func_t       flush;
    H5AC_t                 *cache;
    H5AC_info_t           **new_info = NULL;
    H5AC_info_t           **old_info = NULL;
    herr_t ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI(H5AC_rename, FAIL)

    assert(f);
    assert(f->shared->cache);
    assert(type);

    /* Get local copy of this information */
    old_idx = H5AC_HASH(f, old_addr);
    new_idx = H5AC_HASH(f, new_addr);
    cache = f->shared->cache;
    new_info = cache->slot + new_idx;
    old_info = cache->slot + old_idx;

#ifdef H5AC_DEBUG
    {
        H5AC_prot_t            *prot = NULL;
        int                     i;

        prot = cache->prot + old_idx;
        for (i = 0; i < prot->nprots; i++)
            assert(H5F_addr_ne(old_addr, prot->slot[i]->addr));
        prot = cache->prot + new_idx;
        for (i = 0; i < prot->nprots; i++)
            assert(H5F_addr_ne(new_addr, prot->slot[i]->addr));
    }
#endif

    /*
     * We don't need to do anything if the object isn't cached or if the
     * new hash value is the same as the old one.
     */
    if (H5F_addr_ne((*old_info)->addr, old_addr) || (*old_info)->type!=type)
        HGOTO_DONE(SUCCEED)
    if (old_idx == new_idx) {
        (*old_info)->addr = new_addr;
        HGOTO_DONE(SUCCEED)
    }

#ifdef H5_HAVE_PARALLEL
    /* If MPI based VFD is used, do special parallel I/O actions */
    if(IS_H5FD_MPI(f)) {
        H5AC_info_t       **new_dinfo;
#ifdef H5AC_DEBUG
        H5AC_subid_t        type_id;
#endif /* H5AC_DEBUG */
        H5P_genplist_t *dxpl;           /* Dataset transfer property list */
        H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */

        /* Get the dataset transfer property list */
        if (NULL == (dxpl = H5I_object(dxpl_id)))
            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset creation property list")

        /* Get the transfer mode property */
        if(H5P_get(dxpl, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
            HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't retrieve xfer mode")

        /* Get pointer to new 'held' information */
        new_dinfo = cache->dslot + new_idx;

        /* Sanity check transfer mode */
        if(xfer_mode==H5FD_MPIO_COLLECTIVE) {
            /* Check for dirty metadata */
            if(*new_dinfo) {
                H5AC_dest_func_t        dest;

                /* Various sanity checks */
                assert((*new_dinfo)->dirty);
                assert((*new_info)!=NULL);
                assert((*new_info)->dirty==0);

#ifdef H5AC_DEBUG
                type_id=(*new_info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

                /* Destroy 'current' information */
                dest = (*new_info)->type->dest;
                if ((dest)(f, (*new_info))<0)
                    HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "unable to free cached object")

                /* Restore 'held' information back to 'current' information */
                (*new_info)=(*new_dinfo);

                /* Clear 'held' information */
                (*new_dinfo)=NULL;

#ifdef H5AC_DEBUG
                cache->diagnostics[type_id].nrestores++;
#endif /* H5AC_DEBUG */
            } /* end if */
        } /* end if */
        else {
            /* Sanity check that there will be no write of dirty metadata */
            assert((*new_dinfo)==NULL);
            assert(xfer_mode==H5FD_MPIO_INDEPENDENT);

            /* Make certain there will be no write of dirty metadata */
            if((*new_info) && (*new_info)->dirty) {
                /* Sanity check that we won't put two pieces of dirty metadata in same cache location */
                assert((*old_info)->dirty==0);

                /* 'Hold' the current metadata for later */
                (*new_dinfo)=(*new_info);

                /* Reset the 'current' metadata, so it doesn't get flushed */
                (*new_info)=NULL;

#ifdef H5AC_DEBUG
                cache->diagnostics[(*new_dinfo)->type->id].nholds++;
#endif /* H5AC_DEBUG */
            } /* end if */
        } /* end else */
    } /* end if */
#endif /* H5_HAVE_PARALLEL */

    /*
     * Free the item from the destination cache line.
     */
    if (*new_info) {
#ifdef H5AC_DEBUG
        H5AC_subid_t type_id=(*new_info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

        flush = (*new_info)->type->flush;
        if ( (flush)(f, dxpl_id, TRUE, (*new_info)->addr, (*new_info)) < 0)
            HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush object")
#ifdef H5AC_DEBUG
        cache->diagnostics[type_id].nflushes++;
#endif /* H5AC_DEBUG */
    }

    /*
     * Move the source to the destination (it might not be cached)
     */
    (*new_info)= (*old_info);
    (*new_info)->addr = new_addr;

#ifdef H5_HAVE_PARALLEL
    /* If MPI based VFD is used, do special parallel I/O actions */
    if(IS_H5FD_MPI(f)) {
        H5AC_info_t       **old_dinfo;
#ifdef H5AC_DEBUG
        H5AC_subid_t        type_id;
#endif /* H5AC_DEBUG */

        /* Get pointer to new 'held' information */
        old_dinfo = cache->dslot + old_idx;

        /* Check for 'held' metadata in old location & restore it, if so */
        if(*old_dinfo) {
            /* Sanity check */
            assert((*old_dinfo)->dirty);

#ifdef H5AC_DEBUG
            type_id=(*old_info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

            /* Restore 'held' information back to 'current' information */
            (*old_info)=(*old_dinfo);

            /* Clear 'held' information */
            (*old_dinfo)=NULL;

#ifdef H5AC_DEBUG
            cache->diagnostics[type_id].nrestores++;
#endif /* H5AC_DEBUG */
        } /* end if */
        else
            (*old_info)= NULL;
    } /* end if */
    else {
#endif /* H5_HAVE_PARALLEL */

        (*old_info)= NULL;
#ifdef H5_HAVE_PARALLEL
    } /* end else */
#endif /* H5_HAVE_PARALLEL */

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_protect
 *
 * Purpose:     Similar to H5AC_find() except the object is removed from
 *              the cache and given to the caller, preventing other parts
 *              of the program from modifying the protected object or
 *              preempting it from the cache.
 *
 *              The caller must call H5AC_unprotect() when finished with
 *              the pointer.
 *
 *              If H5AC_DEBUG is defined then we check that the
 *              requested object isn't already protected.
 *
 * Return:      Success:        Ptr to the object.
 *
 *              Failure:        NULL
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Sep  2 1997
 *
 * Modifications:
 *		Robb Matzke, 1999-07-27
 *		The ADDR argument is passed by value.
 *-------------------------------------------------------------------------
 */
void *
H5AC_protect(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type, haddr_t addr,
	     const void *udata1, void *udata2)
{
    unsigned                idx;                /* Index in cache */
    void                   *thing=NULL;
    H5AC_t                 *cache;
    H5AC_info_t           **info;
    void                   *ret_value;          /* Return value */

#ifdef H5AC_DEBUG
    H5AC_prot_t            *prot = NULL;
    static int ncalls = 0;

    if (0 == ncalls++) {
	if (H5DEBUG(AC)) {
	    fprintf(H5DEBUG(AC), "H5AC: debugging cache (expensive)\n");
	}
    }
#endif

    FUNC_ENTER_NOAPI(H5AC_protect, NULL)

    /* check args */
    assert(f);
    assert(f->shared->cache);
    assert(type);
    assert(type->load);
    assert(type->flush);
    assert(H5F_addr_defined(addr));

    /* Get local copy of this information */
    idx = H5AC_HASH(f, addr);
    cache = f->shared->cache;
    info = cache->slot + idx;
#ifdef H5AC_DEBUG
    prot = cache->prot + idx;
#endif /* H5AC_DEBUG */

#ifdef H5_HAVE_PARALLEL
    /* If MPI based VFD is used, do special parallel I/O actions */
    if(IS_H5FD_MPI(f)) {
        H5AC_info_t       **dinfo;

        /* Get pointer to new 'held' information */
        dinfo = cache->dslot + idx;

        /* Check for 'held' metadata in location & handle it */
        if(*dinfo) {
            /* Sanity checks */
            assert((*dinfo)->dirty);
            assert((*info));
            assert((*info)->dirty==0);
            assert((*dinfo)->addr!=(*info)->addr);

            /* Is 'held' metadata the metadata we are looking for? */
            if (H5F_addr_eq((*dinfo)->addr, addr) 
#ifdef H5AC_DEBUG
                    && (*dinfo)->type==type
#endif /* H5AC_DEBUG */
                    ) {
#ifndef H5AC_DEBUG
                /* Sanity check that the object in the cache is the correct type */
                assert((*dinfo)->type==type);
#endif /* H5AC_DEBUG */
                /*
                 * The object is already cached; simply remove it from the cache.
                 */
                thing = (*dinfo);
                (*dinfo)->type = NULL;
                (*dinfo)->addr = HADDR_UNDEF;
                (*dinfo)= NULL;
#ifdef H5AC_DEBUG
                cache->diagnostics[(*dinfo)->type->id].nhits++;
#endif /* H5AC_DEBUG */
            } /* end if */
            /* 'held' metadata isn't what we are looking for, but check for 'current' metadata */
            else {
                if(H5F_addr_eq((*info)->addr, addr)
#ifdef H5AC_DEBUG
                        && (*info)->type==type
#endif /* H5AC_DEBUG */
                        ) {
#ifndef H5AC_DEBUG
                    /* Sanity check that the object in the cache is the correct type */
                    assert((*info)->type==type);
#endif /* H5AC_DEBUG */
                    /*
                     * The object is already cached; remove it from the cache.
                     * and bring the 'held' object into the 'regular' information
                     */
                    thing = (*info);
                    (*info)->type = NULL;
                    (*info)->addr = HADDR_UNDEF;
                    (*info)= (*dinfo);
                    (*dinfo)= NULL;
#ifdef H5AC_DEBUG
                    cache->diagnostics[(*info)->type->id].nhits++;
#endif /* H5AC_DEBUG */
                } /* end if */
            } /* end else */
        } /* end if */
    } /* end if */

    /* Check if we've already found the object to protect */
    if(thing==NULL) {
#endif /* H5_HAVE_PARALLEL */
        if ((*info) && H5F_addr_eq(addr,(*info)->addr)
#ifdef H5AC_DEBUG
                && (*info)->type==type
#endif /* H5AC_DEBUG */
                ) {
#ifndef H5AC_DEBUG
            /* Sanity check that the object in the cache is the correct type */
            assert((*info)->type==type);
#endif /* H5AC_DEBUG */

            /*
             * The object is already cached; simply remove it from the cache.
             */
            thing = (*info);
#ifdef H5AC_DEBUG
            cache->diagnostics[(*info)->type->id].nhits++;
#endif /* H5AC_DEBUG */
            (*info)->type = NULL;
            (*info)->addr = HADDR_UNDEF;
            (*info)= NULL;
        } else {
#ifdef H5AC_DEBUG
            /*
             * Check that the requested thing isn't protected, for protected things
             * can only be modified through the pointer already handed out by the
             * H5AC_protect() function.
             */
            int                    i;

            for (i = 0; i < prot->nprots; i++)
                assert(H5F_addr_ne(addr, prot->slot[i]->addr));
#endif /* H5AC_DEBUG */

            /*
             * Load a new thing.  If it can't be loaded, then return an error
             * without preempting anything.
             */
            if (NULL == (thing = (type->load)(f, dxpl_id, addr, udata1, udata2)))
                HGOTO_ERROR(H5E_CACHE, H5E_CANTLOAD, NULL, "unable to load object")
#ifdef H5AC_DEBUG
            cache->diagnostics[type->id].nmisses++;
#endif /* H5AC_DEBUG */
        }
#ifdef H5_HAVE_PARALLEL
    } /* end if */
#endif /* H5_HAVE_PARALLEL */

#ifdef H5AC_DEBUG
    /*
     * Add the protected object to the protect debugging fields of the
     * cache.
     */
    if (prot->nprots >= prot->aprots) {
        size_t na = prot->aprots + 10;
        H5AC_info_t **x = H5MM_realloc(prot->slot, na * sizeof(H5AC_info_t *));

        if (NULL==x)
            HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
        prot->aprots = (int)na;
        prot->slot = x;
    }
    prot->slot[prot->nprots]= thing;
    prot->slot[prot->nprots]->type = type;
    prot->slot[prot->nprots]->addr = addr;
    prot->nprots += 1;
#endif /* H5AC_DEBUG */

    cache->nprots += 1;

    /* Set return value */
    ret_value=thing;

done:
    FUNC_LEAVE_NOAPI(ret_value)
}


/*-------------------------------------------------------------------------
 * Function:    H5AC_unprotect
 *
 * Purpose:     This function should be called to undo the effect of
 *              H5AC_protect().  The TYPE and ADDR arguments should be the
 *              same as the corresponding call to H5AC_protect() and the
 *              THING argument should be the value returned by H5AC_protect().
 *              If the DELETED flag is set, then this object has been deleted
 *              from the file and should not be returned to the cache.
 *
 *              If H5AC_DEBUG is defined then this function fails
 *              if the TYPE and ADDR arguments are not what was used when the
 *              object was protected or if the object was never protected.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              matzke@llnl.gov
 *              Sep  2 1997
 *
 * Modifications:
 * 		Robb Matzke, 1999-07-27
 *		The ADDR argument is passed by value.
 *
 * 		Quincey Koziol, 2003-03-19
 *		Added "deleted" argument
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_unprotect(H5F_t *f, hid_t dxpl_id, const H5AC_class_t *type, haddr_t addr, void *thing, hbool_t deleted)
{
    unsigned                idx;
    H5AC_flush_func_t       flush;
    H5AC_t                 *cache;
    H5AC_info_t           **info;
    herr_t                  ret_value=SUCCEED;      /* Return value */

    FUNC_ENTER_NOAPI(H5AC_unprotect, FAIL)

    /* check args */
    assert(f);
    assert(f->shared->cache);
    assert(type);
    assert(type->flush);
    assert(H5F_addr_defined(addr));
    assert(thing);

    /* Get local copy of this information */
    idx = H5AC_HASH(f, addr);
    cache = f->shared->cache;
    info = cache->slot + idx;

#ifdef H5AC_DEBUG
    /*
     * Remove the object's protect data to indicate that it is no longer
     * protected.
     */
    {
        H5AC_prot_t            *prot = NULL;
        int                     found, i;

        prot = cache->prot + idx;
        for (i = 0, found = FALSE; i < prot->nprots && !found; i++) {
            if (H5F_addr_eq(addr, prot->slot[i]->addr)) {
                assert(prot->slot[i]->type == type);
                HDmemmove(prot->slot + i, prot->slot + i + 1,
                          ((prot->nprots - i) - 1) * sizeof(H5AC_info_t *));
                prot->nprots -= 1;
                found = TRUE;
            }
        }
        assert(found);
    }
#endif /* H5AC_DEBUG */

    /* Don't restore deleted objects to the cache */
    if(!deleted) {
#ifdef H5_HAVE_PARALLEL
        /* If MPI based VFD is used, do special parallel I/O actions */
        if(IS_H5FD_MPI(f)) {
            H5AC_info_t       **dinfo;
#ifdef H5AC_DEBUG
            H5AC_subid_t        type_id;
#endif /* H5AC_DEBUG */
            H5P_genplist_t *dxpl;           /* Dataset transfer property list */
            H5FD_mpio_xfer_t xfer_mode;     /* I/O transfer mode property value */

            /* Get the dataset transfer property list */
            if (NULL == (dxpl = H5I_object(dxpl_id)))
                HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a dataset creation property list")

            /* Get the transfer mode property */
            if(H5P_get(dxpl, H5D_XFER_IO_XFER_MODE_NAME, &xfer_mode) < 0)
                HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't retrieve xfer mode")

            /* Get pointer to 'held' information */
            dinfo = cache->dslot + idx;

            /* Sanity check transfer mode */
            if(xfer_mode==H5FD_MPIO_COLLECTIVE) {
                /* Check for dirty metadata */
                if(*dinfo) {
                    H5AC_dest_func_t        dest;

                    /* Various sanity checks */
                    assert((*dinfo)->dirty);
                    assert((*info)!=NULL);
                    assert((*info)->dirty==0);

#ifdef H5AC_DEBUG
                    type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

                    /* Destroy 'current' information */
                    dest = (*info)->type->dest;
                    if ((dest)(f, (*info))<0)
                        HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "unable to free cached object")

                    /* Restore 'held' information back to 'current' information */
                    (*info)=(*dinfo);

                    /* Clear 'held' information */
                    (*dinfo)=NULL;

#ifdef H5AC_DEBUG
                    cache->diagnostics[type_id].nrestores++;
#endif /* H5AC_DEBUG */
                } /* end if */
            } /* end if */
            else {
                /* Sanity check */
                assert((*dinfo)==NULL);
                assert(xfer_mode==H5FD_MPIO_INDEPENDENT);

                /* Make certain there will be no write of dirty metadata */
                if((*info) && (*info)->dirty) {
                    /* Sanity check new item */
                    assert(((H5AC_info_t*)thing)->dirty==0);

                    /* 'Hold' the current metadata for later */
                    (*dinfo)=(*info);

                    /* Reset the 'current' metadata, so it doesn't get flushed */
                    (*info)=NULL;

#ifdef H5AC_DEBUG
                    cache->diagnostics[(*dinfo)->type->id].nholds++;
#endif /* H5AC_DEBUG */
                } /* end if */
            } /* end else */
        } /* end if */
#endif /* H5_HAVE_PARALLEL */

        /*
         * Flush any object already in the cache at that location.  It had
         * better not be another copy of the protected object.
         */
        if (*info) {
#ifdef H5AC_DEBUG
            H5AC_subid_t type_id=(*info)->type->id;  /* Remember this for later */
#endif /* H5AC_DEBUG */

            assert(H5F_addr_ne((*info)->addr, addr));
            flush = (*info)->type->flush;
            if ((flush)(f, dxpl_id, TRUE, (*info)->addr, (*info)) < 0)
                HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to flush object")
#ifdef H5AC_DEBUG
            cache->diagnostics[type_id].nflushes++;
#endif /* H5AC_DEBUG */
        }

        /*
         * Insert the object back into the cache; it is no longer protected.
         */
        (*info)=thing;
        (*info)->type = type;
        (*info)->addr = addr;
    } /* end if */
    else {
        /* Mark the thing as clean (prerequite for destroy routine) */
        if((type->clear)(thing)<0)
            HGOTO_ERROR(H5E_CACHE, H5E_CANTFLUSH, FAIL, "unable to clear object")

        /* Destroy previously cached thing */
        if ((type->dest)(f, thing)<0)
            HGOTO_ERROR(H5E_CACHE, H5E_CANTFREE, FAIL, "unable to free object")
    } /* end else */

    /* Decrement the number of protected items outstanding */
    cache->nprots -= 1;

done:
    FUNC_LEAVE_NOAPI(ret_value)
}

#ifdef H5AC_DEBUG

/*-------------------------------------------------------------------------
 * Function:    H5AC_stats
 *
 * Purpose:     Prints statistics about the cache.
 *
 * Return:      Non-negative on success/Negative on failure
 *
 * Programmer:  Robb Matzke
 *              Thursday, October 30, 1997
 *
 * Modifications:
 *
 *-------------------------------------------------------------------------
 */
herr_t
H5AC_stats(H5F_t UNUSED *f)
{
    H5AC_subid_t            i;
    char                    s[32], ascii[32];
    H5AC_t                 *cache = f->shared->cache;
    double                  miss_rate;
    herr_t ret_value=SUCCEED;   /* Return value */

    FUNC_ENTER_NOAPI(H5AC_stats, FAIL)

    if (H5DEBUG(AC)) {
	fprintf(H5DEBUG(AC), "H5AC: meta data cache statistics for file %s\n",
		f->name);
	fprintf(H5DEBUG(AC), "   %-18s %8s %8s %8s %8s+%-8s\n",
		"Layer", "Hits", "Misses", "MissRate", "Inits", "Flushes");
	fprintf(H5DEBUG(AC), "   %-18s %8s %8s %8s %8s-%-8s\n",
		"-----", "----", "------", "--------", "-----", "-------");

	for (i = H5AC_BT_ID; i < H5AC_NTYPES; i++) {

	    switch (i) {
	    case H5AC_BT_ID:
		HDstrcpy(s, "B-tree nodes");
		break;
	    case H5AC_SNODE_ID:
		HDstrcpy(s, "symbol table nodes");
		break;
	    case H5AC_LHEAP_ID:
		HDstrcpy (s, "local heaps");
		break;
	    case H5AC_GHEAP_ID:
		HDstrcpy (s, "global heaps");
		break;
	    case H5AC_OHDR_ID:
		HDstrcpy(s, "object headers");
		break;
	    default:
		sprintf(s, "unknown id %d", i);
	    }

	    if (cache->diagnostics[i].nhits>0 ||
		cache->diagnostics[i].nmisses>0) {
		miss_rate = 100.0 * cache->diagnostics[i].nmisses /
			    (cache->diagnostics[i].nhits+
			     cache->diagnostics[i].nmisses);
	    } else {
		miss_rate = 0.0;
	    }

	    if (miss_rate > 100) {
		sprintf(ascii, "%7d%%", (int) (miss_rate + 0.5));
	    } else {
		sprintf(ascii, "%7.2f%%", miss_rate);
	    }
	    fprintf(H5DEBUG(AC), "   %-18s %8u %8u %7s %8u%+-9ld\n", s,
		    cache->diagnostics[i].nhits,
		    cache->diagnostics[i].nmisses,
		    ascii,
		    cache->diagnostics[i].ninits,
		    ((long)(cache->diagnostics[i].nflushes) -
		     (long)(cache->diagnostics[i].ninits)));
	}
    }

done:
    FUNC_LEAVE_NOAPI(ret_value)
}
#endif /* H5AC_DEBUG */