[svn-r8844] Purpose:

    Bug fix

Description:
    The "shared" raw B-tree node can get freed before all the B-tree nodes
had been flushed out to disk and released by the cache.

Solution:
    Implement a simple reference counting wrapper for objects in the library
and use it to hold the shared raw B-tree nodes so they aren't freed before all
references to them in memory are released.

Platforms tested:
    Solaris 2.7 (arabica)
    FreeBSD 4.10 (sleipnir)
    IRIX64 6.5 (modei4)

12 files changed, 303 insertions, 28 deletions

diff --git a/src/H5B.c b/src/H5B.c
index 0da67bb..5529aea 100644
--- a/src/H5B.c
+++ b/src/H5B.c
@@ -241,8 +241,9 @@ H5B_create(H5F_t *f, hid_t dxpl_id, const H5B_class_t *type, void *udata,
     bt->left = HADDR_UNDEF;
     bt->right = HADDR_UNDEF;
     bt->nchildren = 0;
-    if((bt->raw_page=(type->get_page)(f, udata))==NULL)
+    if((bt->rc_page=(type->get_page)(f, udata))==NULL)
 	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "can't retrieve B-tree node buffer")
+    bt->raw_page=H5RC_GET_OBJ(bt->rc_page);
     if (NULL==(bt->native=H5FL_BLK_MALLOC(native_block,total_native_keysize)) ||
             NULL==(bt->child=H5FL_SEQ_MALLOC(haddr_t,(size_t)(2*H5F_KVALUE(f,type)))) ||
             NULL==(bt->nkey=H5FL_SEQ_MALLOC(voidp,(size_t)(2*H5F_KVALUE(f,type)+1))))
@@ -340,8 +341,9 @@ H5B_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void *_type, void *udata)
             NULL==(bt->child=H5FL_SEQ_MALLOC(haddr_t,(size_t)(2*H5F_KVALUE(f,type)))))
 	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "memory allocation failed")
 
-    if((bt->raw_page=(type->get_page)(f, udata))==NULL)
+    if((bt->rc_page=(type->get_page)(f, udata))==NULL)
 	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, NULL, "can't retrieve B-tree node buffer")
+    bt->raw_page=H5RC_GET_OBJ(bt->rc_page);
     if (H5F_block_read(f, H5FD_MEM_BTREE, addr, size, dxpl_id, bt->raw_page)<0)
 	HGOTO_ERROR(H5E_BTREE, H5E_READERROR, NULL, "can't read B-tree node")
 
@@ -574,6 +576,7 @@ H5B_dest(H5F_t UNUSED *f, H5B_t *bt)
     H5FL_SEQ_FREE(haddr_t,bt->child);
     H5FL_SEQ_FREE(voidp,bt->nkey);
     H5FL_BLK_FREE(native_block,bt->native);
+    H5RC_DEC(bt->rc_page);
     H5FL_FREE(H5B_t,bt);
 
     FUNC_LEAVE_NOAPI(SUCCEED)
@@ -2203,6 +2206,9 @@ H5B_copy(const H5F_t *f, const H5B_t *old_bt)
             new_node->nkey[u] = NULL;
         }
 
+    /* Increment the ref-count on the raw page */
+    H5RC_INC(new_node->rc_page);
+
     /* Set return value */
     ret_value=new_node;
 
diff --git a/src/H5Bpkg.h b/src/H5Bpkg.h
index 67b49db..67135cf 100644
--- a/src/H5Bpkg.h
+++ b/src/H5Bpkg.h
@@ -31,6 +31,7 @@
 #include "H5Bprivate.h"
 
 /* Other private headers needed by this file */
+#include "H5RCprivate.h"	/* Reference counted object functions	  */
 
 /**************************/
 /* Package Private Macros */
@@ -54,6 +55,7 @@ struct H5B_t {
     haddr_t		left;		/*address of left sibling	     */
     haddr_t		right;		/*address of right sibling	     */
     unsigned		nchildren;	/*number of child pointers	     */
+    H5RC_t		*rc_page;	/*ref-counted disk page		     */
     uint8_t		*raw_page;	/*disk page (shared)		     */
     uint8_t		*native;	/*array of keys in native format     */
     void		**nkey;		/*2k+1 key entries		     */
diff --git a/src/H5Distore.c b/src/H5Distore.c
index 0bab89d..09c025c 100644
--- a/src/H5Distore.c
+++ b/src/H5Distore.c
@@ -146,6 +146,7 @@ static haddr_t H5D_istore_get_addr(H5F_t *f, hid_t dxpl_id, const H5O_layout_t *
     const hssize_t offset[], H5D_istore_ud1_t *_udata);
 static void *H5D_istore_chunk_alloc(size_t size, const H5O_pline_t *pline);
 static void *H5D_istore_chunk_xfree(void *chk, const H5O_pline_t *pline);
+static herr_t H5D_istore_page_free (void *page);
 
 /* B-tree iterator callbacks */
 static int H5D_istore_iter_allocated(H5F_t *f, hid_t dxpl_id, void *left_key, haddr_t addr,
@@ -278,9 +279,13 @@ H5D_istore_get_page(H5F_t UNUSED *f, const void *_udata)
 
     assert(udata);
     assert(udata->mesg);
-    assert(udata->mesg->u.chunk.raw_page);
+    assert(udata->mesg->u.chunk.rc_page);
 
-    FUNC_LEAVE_NOAPI(udata->mesg->u.chunk.raw_page);
+    /* Increment reference count on B-tree node */
+    H5RC_INC(udata->mesg->u.chunk.rc_page);
+
+    /* Get the pointer to the ref-count object */
+    FUNC_LEAVE_NOAPI(udata->mesg->u.chunk.rc_page);
 } /* end H5D_istore_get_page() */
 
 
@@ -898,6 +903,7 @@ H5D_istore_init (H5F_t *f, H5D_t *dset)
     size_t		sizeof_rkey;    /* Single raw key size */
     size_t              size;           /* Raw B-tree node size */
     H5D_rdcc_t	*rdcc = &(dset->cache.chunk);
+    void        *page;                  /* Buffer for raw B-tree node */
     herr_t      ret_value=SUCCEED;       /* Return value */
     
     FUNC_ENTER_NOAPI(H5D_istore_init, FAIL);
@@ -919,9 +925,13 @@ H5D_istore_init (H5F_t *f, H5D_t *dset)
     assert(sizeof_rkey);
     size = H5B_nodesize(f, H5B_ISTORE, NULL, sizeof_rkey);
     assert(size);
-    if(NULL==(dset->layout.u.chunk.raw_page=H5FL_BLK_MALLOC(chunk_page,size)))
+    if(NULL==(page=H5FL_BLK_MALLOC(chunk_page,size)))
 	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for B-tree page")
 
+    /* Make page buffer reference counted */
+    if(NULL==(dset->layout.u.chunk.rc_page=H5RC_create(page,H5D_istore_page_free)))
+	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't create ref-count wrapper for page")
+
 done:
     FUNC_LEAVE_NOAPI(ret_value);
 } /* end H5D_istore_init() */
@@ -1217,7 +1227,8 @@ H5D_istore_dest (H5F_t *f, hid_t dxpl_id, H5D_t *dset)
     HDmemset (rdcc, 0, sizeof(H5D_rdcc_t));
 
     /* Free the raw B-tree node buffer */
-    H5FL_BLK_FREE(chunk_page,dset->layout.u.chunk.raw_page);
+    if(H5RC_DEC(dset->layout.u.chunk.rc_page)<0)
+	HGOTO_ERROR (H5E_IO, H5E_CANTFREE, FAIL, "unable to decrement ref-counted page");
 
 done:
     FUNC_LEAVE_NOAPI(ret_value);
@@ -1225,6 +1236,31 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5D_istore_page_free
+ *
+ * Purpose:	Free a B-tree node
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Thursday, July  8, 2004
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5D_istore_page_free (void *page)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5D_istore_page_free)
+
+    H5FL_BLK_FREE(chunk_page,page);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5D_istore_page_free() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5D_istore_prune
  *
  * Purpose:	Prune the cache by preempting some things until the cache has
diff --git a/src/H5F.c b/src/H5F.c
index 86f9019..de16b40 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -1490,10 +1490,6 @@ H5F_new(H5F_file_t *shared, hid_t fcpl_id, hid_t fapl_id)
         /* Create the file's "open object" information */
         if(H5FO_create(f)<0)
 	    HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create open object TBBT")
-
-        /* Create information needed for group nodes */
-        if(H5G_node_init(f)<0)
-	    HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, NULL, "unable to create group node info")
     } /* end else */
     
     f->shared->nrefs++;
@@ -4472,7 +4468,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5F_raw_page
+ * Function:	H5F_rc_page
  *
  * Purpose:	Replaced a macro to retrieve the raw B-tree page value
  *              now that the generic properties are being used to store
@@ -4491,15 +4487,15 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *H5F_raw_page(const H5F_t *f)
+H5RC_t *H5F_rc_page(const H5F_t *f)
 {
     /* Use FUNC_ENTER_NOAPI_NOINIT_NOFUNC here to avoid performance issues */
-    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5F_raw_page)
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5F_rc_page)
 
     assert(f);
     assert(f->shared);
 
-    FUNC_LEAVE_NOAPI(f->shared->raw_page)
+    FUNC_LEAVE_NOAPI(f->shared->rc_page)
 } /* end H5F_raw_page() */
 
 
diff --git a/src/H5Fpkg.h b/src/H5Fpkg.h
index 567ea39..318a8f1 100644
--- a/src/H5Fpkg.h
+++ b/src/H5Fpkg.h
@@ -37,6 +37,7 @@
 #include "H5private.h"		/* Generic Functions			*/
 #include "H5FOprivate.h"        /* File objects                         */
 #include "H5Gprivate.h"		/* Groups 			  	*/
+#include "H5RCprivate.h"	/* Reference counted object functions	*/
 
 /*
  * Feature: Define this constant to be non-zero if you want to enable code
@@ -126,7 +127,7 @@ typedef struct H5F_file_t {
     struct H5HG_heap_t **cwfs;	/* Global heap cache			*/
     H5FO_t *open_objs;          /* Open objects in file                 */
     H5F_close_degree_t fc_degree;   /* File close behavior degree	*/
-    void        *raw_page;      /* Pointer to raw B-tree node buffer    */
+    H5RC_t      *rc_page;       /* Pointer to ref-counted raw B-tree node buffer    */
 } H5F_file_t;
 
 /* A record of the mount table */
diff --git a/src/H5Fprivate.h b/src/H5Fprivate.h
index aace023..452b160 100644
--- a/src/H5Fprivate.h
+++ b/src/H5Fprivate.h
@@ -211,7 +211,7 @@ typedef struct H5F_t H5F_t;
 /* Check for file driver feature enabled */
 #define H5F_HAS_FEATURE(F,FL)   ((F)->shared->lf->feature_flags&(FL))
 /* B-tree node raw page */
-#define H5F_RAW_PAGE(F)         ((F)->shared->raw_page)
+#define H5F_RC_PAGE(F)          ((F)->shared->rc_page)
 #else /* H5F_PACKAGE */
 #define H5F_SIZEOF_ADDR(F)      (H5F_sizeof_addr(F))
 #define H5F_SIZEOF_SIZE(F)      (H5F_sizeof_size(F))
@@ -221,7 +221,7 @@ typedef struct H5F_t H5F_t;
 #define H5F_RDCC_NBYTES(F)      (H5F_rdcc_nbytes(F))
 #define H5F_RDCC_W0(F)          (H5F_rdcc_w0(F))
 #define H5F_HAS_FEATURE(F,FL)   (H5F_has_feature(F,FL))
-#define H5F_RAW_PAGE(F)         (H5F_raw_page(F))
+#define H5F_RC_PAGE(F)         (H5F_rc_page(F))
 #endif /* H5F_PACKAGE */
 
 
@@ -387,6 +387,7 @@ typedef struct H5F_t H5F_t;
 
 /* Forward declarations for prototype arguments */
 struct H5B_class_t;
+struct H5RC_t;
 
 /* Private functions, not part of the publicly documented API */
 H5_DLL herr_t H5F_init(void);
@@ -417,7 +418,7 @@ H5_DLL hbool_t H5F_has_feature(const H5F_t *f, unsigned feature);
 H5_DLL size_t H5F_rdcc_nbytes(const H5F_t *f);
 H5_DLL size_t H5F_rdcc_nelmts(const H5F_t *f);
 H5_DLL double H5F_rdcc_w0(const H5F_t *f);
-H5_DLL void *H5F_raw_page(const H5F_t *f);
+H5_DLL struct H5RC_t *H5F_rc_page(const H5F_t *f);
 
 /* Functions that operate on blocks of bytes wrt super block */
 H5_DLL herr_t H5F_block_read(const H5F_t *f, H5FD_mem_t type, haddr_t addr,
diff --git a/src/H5G.c b/src/H5G.c
index ee3d5a4..27f43e8 100644
--- a/src/H5G.c
+++ b/src/H5G.c
@@ -1524,6 +1524,7 @@ done:
     /* If we started with a NULL grp_ent and we copied something into it, free the entry information */
     if(null_grp && group_copy)
         H5G_free_ent_name(grp_ent);
+
    FUNC_LEAVE_NOAPI(ret_value);
 }
 
@@ -1661,6 +1662,10 @@ H5G_mkroot (H5F_t *f, hid_t dxpl_id, H5G_entry_t *ent)
     if (f->shared->root_grp)
         HGOTO_DONE(SUCCEED);
 
+    /* Create information needed for group nodes */
+    if(H5G_node_init(f)<0)
+        HGOTO_ERROR(H5E_SYM, H5E_CANTINIT, FAIL, "unable to create group node info")
+
     /*
      * If there is no root object then create one. The root group always has
      * a hard link count of one since it's pointed to by the boot block.
diff --git a/src/H5Gnode.c b/src/H5Gnode.c
index 1925ee5..1710270 100644
--- a/src/H5Gnode.c
+++ b/src/H5Gnode.c
@@ -64,6 +64,7 @@ typedef struct H5G_node_key_t {
 /* PRIVATE PROTOTYPES */
 static herr_t H5G_node_serialize(H5F_t *f, H5G_node_t *sym, size_t size, uint8_t *buf);
 static size_t H5G_node_size(H5F_t *f);
+static herr_t H5G_node_page_free (void *page);
 
 /* Metadata cache callbacks */
 static H5G_node_t *H5G_node_load(H5F_t *f, hid_t dxpl_id, haddr_t addr, const void *_udata1,
@@ -196,7 +197,11 @@ H5G_node_get_page(H5F_t *f, const void UNUSED *_udata)
 
     assert(f);
 
-    FUNC_LEAVE_NOAPI(H5F_RAW_PAGE(f));
+    /* Increment reference count on B-tree node */
+    H5RC_INC(H5F_RC_PAGE(f));
+
+    /* Get the pointer to the ref-count object */
+    FUNC_LEAVE_NOAPI(H5F_RC_PAGE(f));
 } /* end H5G_node_get_page() */
 
 
@@ -1722,8 +1727,9 @@ done:
 herr_t
 H5G_node_init(H5F_t *f)
 {
-    size_t		sizeof_rkey;    /* Single raw key size */
-    size_t              size;           /* Raw B-tree node size */
+    size_t	sizeof_rkey;            /* Single raw key size */
+    size_t      size;                   /* Raw B-tree node size */
+    void        *page;                  /* Buffer for raw B-tree node */
     herr_t      ret_value = SUCCEED;    /* Return value */
 
     FUNC_ENTER_NOAPI(H5G_node_init, FAIL);
@@ -1736,9 +1742,13 @@ H5G_node_init(H5F_t *f)
     assert(sizeof_rkey);
     size = H5B_nodesize(f, H5B_SNODE, NULL, sizeof_rkey);
     assert(size);
-    if(NULL==(f->shared->raw_page=H5FL_BLK_MALLOC(grp_page,size)))
+    if(NULL==(page=H5FL_BLK_MALLOC(grp_page,size)))
 	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "memory allocation failed for B-tree page")
 
+    /* Make page buffer reference counted */
+    if(NULL==(f->shared->rc_page=H5RC_create(page,H5G_node_page_free)))
+	HGOTO_ERROR (H5E_RESOURCE, H5E_NOSPACE, FAIL, "can't create ref-count wrapper for page")
+
 done:
     FUNC_LEAVE_NOAPI(ret_value);
 } /* end H5G_node_init() */
@@ -1768,13 +1778,39 @@ H5G_node_close(const H5F_t *f)
     assert(f);
 
     /* Free the raw B-tree node buffer */
-    H5FL_BLK_FREE(grp_page,f->shared->raw_page);
+    H5RC_DEC(f->shared->rc_page);
 
     FUNC_LEAVE_NOAPI(SUCCEED);
 } /* end H5G_node_close */
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5G_node_page_free
+ *
+ * Purpose:	Free a B-tree node
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Thursday, July  8, 2004
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5G_node_page_free (void *page)
+{
+    FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5G_node_page_free)
+
+    /* Free the raw B-tree node buffer */
+    H5FL_BLK_FREE(grp_page,page);
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5G_node_page_free() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5G_node_debug
  *
  * Purpose:	Prints debugging information about a symbol table node
diff --git a/src/H5Oprivate.h b/src/H5Oprivate.h
index b7d9b46..26bf5d8 100644
--- a/src/H5Oprivate.h
+++ b/src/H5Oprivate.h
@@ -37,6 +37,7 @@
 /* Private headers needed by this file */
 #include "H5private.h"          /* Generic functions                      */
 #include "H5HGprivate.h"        /* Global heap functions                  */
+#include "H5RCprivate.h"	/* Reference counted object functions	  */
 #include "H5Tprivate.h"		/* Datatype functions			  */
 #include "H5Zprivate.h"         /* I/O pipeline filters			  */
 
@@ -133,7 +134,7 @@ typedef struct H5O_layout_chunk_t {
     unsigned	ndims;			/* Num dimensions in chunk           */
     size_t	dim[H5O_LAYOUT_NDIMS];	/* Size of chunk in elements         */
     size_t      size;                   /* Size of chunk in bytes            */
-    void       *raw_page;               /* Buffer for raw B-tree page        */
+    H5RC_t     *rc_page;                /* Ref-counted buffer for raw B-tree page        */
 } H5O_layout_chunk_t;
 
 typedef struct H5O_layout_compact_t {
diff --git a/src/H5RC.c b/src/H5RC.c
new file mode 100644
index 0000000..8ab1818
--- /dev/null
+++ b/src/H5RC.c
@@ -0,0 +1,129 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * 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. *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * Reference counting buffer algorithms.
+ *
+ * These are used for various internal buffers which are shared.
+ *
+ */
+
+/* Pablo information */
+/* (Put before include files to avoid problems with inline functions) */
+#define PABLO_MASK	H5RC_mask
+
+#include "H5Eprivate.h"		/* Error handling		  	*/
+#include "H5FLprivate.h"	/* Free lists                           */
+#include "H5RCprivate.h"        /* Reference-counted buffers            */
+
+/* Private typedefs & structs */
+
+/* Declare a free list to manage the H5RC_t struct */
+H5FL_DEFINE_STATIC(H5RC_t);
+
+
+/*--------------------------------------------------------------------------
+ NAME
+    H5RC_create
+ PURPOSE
+    Create a reference counted object
+ USAGE
+    H5RC_t *H5RC_create(o,free)
+        const void *o;          IN: Object to initialize ref-counted object with
+        H5RC_free_func_t free;  IN: Function to call when ref-count drop to zero
+
+ RETURNS
+    Returns a pointer to a new ref-counted object on success, NULL on failure.
+ DESCRIPTION
+    Create a reference counted object.  The object is not duplicated, it is
+    assumed to be owned by the reference counted object now and will be freed
+    with the 'free' function when the reference count drops to zero.
+ GLOBAL VARIABLES
+ COMMENTS, BUGS, ASSUMPTIONS
+ EXAMPLES
+ REVISION LOG
+--------------------------------------------------------------------------*/
+H5RC_t *
+H5RC_create(void *o, H5RC_free_func_t free_func)
+{
+    H5RC_t *ret_value=NULL;   /* Return value */
+
+    FUNC_ENTER_NOAPI(H5RC_create,NULL);
+
+    /* Sanity check */
+    HDassert(o);
+    HDassert(free_func);
+
+    /* Allocate ref-counted string structure */
+    if((ret_value=H5FL_MALLOC(H5RC_t))==NULL)
+        HGOTO_ERROR(H5E_RS,H5E_NOSPACE,NULL,"memory allocation failed");
+
+    /* Set the internal fields */
+    ret_value->o=o;
+    ret_value->n=1;
+    ret_value->free_func=free_func;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* end H5RC_create() */
+
+
+/*--------------------------------------------------------------------------
+ NAME
+    H5RC_decr
+ PURPOSE
+    Decrement the reference count for a ref-counted object
+ USAGE
+    herr_t H5RC_decr(rc)
+        H5RC_t *rc;             IN: Ref-counted object to decrement count for
+
+ RETURNS
+    SUCCEED/FAIL
+ DESCRIPTION
+    Decrements the reference count for a ref-counted object, calling the
+    object's free function if ref-count drops to zero.
+ GLOBAL VARIABLES
+ COMMENTS, BUGS, ASSUMPTIONS
+ EXAMPLES
+ REVISION LOG
+--------------------------------------------------------------------------*/
+herr_t
+H5RC_decr(H5RC_t *rc)
+{
+    herr_t ret_value=SUCCEED;   /* Return value */
+
+    FUNC_ENTER_NOAPI(H5RC_decr,FAIL);
+
+    /* Sanity check */
+    HDassert(rc);
+    HDassert(rc->o);
+    HDassert(rc->n>0);
+    HDassert(rc->free_func);
+
+    /* Decrement reference count */
+    rc->n--;
+
+    /* Check if we should delete this object now */
+    if(rc->n==0) {
+        if((rc->free_func)(rc->o)<0) {
+            H5FL_FREE(H5RC_t,rc);
+            HGOTO_ERROR(H5E_RS,H5E_CANTFREE,FAIL,"memory release failed");
+        } /* end if */
+        H5FL_FREE(H5RC_t,rc);
+    } /* end if */
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value);
+} /* end H5RC_decr() */
+
diff --git a/src/H5RCprivate.h b/src/H5RCprivate.h
new file mode 100644
index 0000000..7f1dc3a
--- /dev/null
+++ b/src/H5RCprivate.h
@@ -0,0 +1,62 @@
+/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
+ * 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. *
+ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
+
+/*
+ * This file contains private information about the H5RC module
+ */
+#ifndef _H5RCprivate_H
+#define _H5RCprivate_H
+
+/**************************************/
+/* Public headers needed by this file */
+/**************************************/
+#ifdef LATER
+#include "H5RCpublic.h"
+#endif /* LATER */
+
+/***************************************/
+/* Private headers needed by this file */
+/***************************************/
+#include "H5private.h"
+
+/************/
+/* Typedefs */
+/************/
+
+/* Typedef for function to release object when reference count drops to zero */
+typedef herr_t (*H5RC_free_func_t)(void *o);
+
+/* Typedef for reference counted objects */
+typedef struct H5RC_t {
+    void *o;            /* Object to be reference counted */
+    size_t n;           /* Reference count of number of pointers sharing object */
+    H5RC_free_func_t free_func; /* Function to free object */
+} H5RC_t;
+
+/**********/
+/* Macros */
+/**********/
+#define H5RC_INC(rc)            ((rc)->n++)
+#define H5RC_DEC(rc)            (H5RC_decr(rc))
+#define H5RC_GET_OBJ(rc)        ((rc)->o)
+
+/********************/
+/* Private routines */
+/********************/
+H5_DLL H5RC_t *H5RC_create(void *s, H5RC_free_func_t free_func);
+H5_DLL herr_t H5RC_decr(H5RC_t *rc);
+
+#endif /* _H5RSprivate_H */
+
+
diff --git a/src/Makefile.in b/src/Makefile.in
index dc59c33..4c05597 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -40,7 +40,7 @@ LIB_SRC=H5.c H5A.c H5AC.c H5B.c H5C.c H5D.c H5Dcontig.c H5Dcompact.c H5Dio.c  \
         H5Obogus.c H5Ocont.c H5Odtype.c H5Oefl.c H5Ofill.c H5Olayout.c        \
         H5Omtime.c H5Oname.c H5Onull.c H5Opline.c H5Osdspace.c H5Oshared.c    \
         H5Ostab.c H5P.c H5Pdcpl.c H5Pdxpl.c H5Pfapl.c H5Pfcpl.c H5Ptest.c     \
-        H5R.c H5RS.c H5S.c H5Sall.c H5Shyper.c H5Smpio.c  H5Snone.c           \
+        H5R.c H5RC.c H5RS.c H5S.c H5Sall.c H5Shyper.c H5Smpio.c  H5Snone.c    \
         H5Spoint.c H5Sselect.c H5Stest.c H5ST.c H5T.c H5Tarray.c H5Tbit.c     \
         H5Tcommit.c H5Tcompound.c H5Tconv.c H5Tcset.c H5Tenum.c H5Tfields.c   \
         H5Tfixed.c H5Tfloat.c H5Tinit.c H5Tnative.c H5Toffset.c H5Topaque.c   \
@@ -70,9 +70,9 @@ PRIVATE_HDR=H5private.h H5Aprivate.h H5Apkg.h H5ACprivate.h H5Bprivate.h      \
 	H5FSprivate.h H5Gprivate.h H5Gpkg.h H5HGprivate.h H5HGpkg.h           \
 	H5HLprivate.h H5HLpkg.h H5HPprivate.h H5Iprivate.h H5MFprivate.h      \
 	H5MMprivate.h H5Oprivate.h H5Opkg.h H5Pprivate.h H5Ppkg.h             \
-	H5Rprivate.h H5RSprivate.h H5Sprivate.h H5STprivate.h H5Tprivate.h    \
-	H5TBprivate.h H5Tpkg.h H5TSprivate.h H5Vprivate.h H5Zprivate.h        \
-	H5Zpkg.h H5config.h
+	H5Rprivate.h H5RCprivate.h H5RSprivate.h H5Sprivate.h H5STprivate.h   \
+        H5Tprivate.h H5TBprivate.h H5Tpkg.h H5TSprivate.h H5Vprivate.h        \
+        H5Zprivate.h H5Zpkg.h H5config.h
 
 ## Error header generation
 ##