[svn-r8458] Purpose:

    Code optimization

Description:
    Stop straddling the line and always use elements instead of bytes to
determine how how I/O to perform on a selection.

Platforms tested:
    Solaris 2.7 (arabica)
    FreeBSD 4.9 (sleipnir)
    too minor to require h5committest

5 files changed, 176 insertions, 256 deletions

diff --git a/src/H5Sall.c b/src/H5Sall.c
index 3708bed..6f5152d 100644
--- a/src/H5Sall.c
+++ b/src/H5Sall.c
@@ -786,10 +786,10 @@ done:
                                     position of interest in selection.
         size_t elem_size;       IN: Size of an element
         size_t maxseq;          IN: Maximum number of sequences to generate
-        size_t maxbytes;        IN: Maximum number of bytes to include in the
+        size_t maxelem;         IN: Maximum number of elements to include in the
                                     generated sequences
         size_t *nseq;           OUT: Actual number of sequences generated
-        size_t *nbytes;         OUT: Actual number of bytes in sequences generated
+        size_t *nelem;          OUT: Actual number of elements in sequences generated
         hsize_t *off;           OUT: Array of offsets
         size_t *len;            OUT: Array of lengths
  RETURNS
@@ -807,10 +807,9 @@ done:
 --------------------------------------------------------------------------*/
 herr_t
 H5S_all_get_seq_list(const H5S_t UNUSED *space, unsigned UNUSED flags, H5S_sel_iter_t *iter,
-    size_t elem_size, size_t UNUSED maxseq, size_t maxbytes, size_t *nseq, size_t *nbytes,
+    size_t elem_size, size_t UNUSED maxseq, size_t maxelem, size_t *nseq, size_t *nelem,
     hsize_t *off, size_t *len)
 {
-    size_t max_elem;            /* Maximum number of elements to use */
     size_t elem_used;           /* The number of elements used */
     herr_t ret_value=SUCCEED;   /* return value */
 
@@ -821,18 +820,15 @@ H5S_all_get_seq_list(const H5S_t UNUSED *space, unsigned UNUSED flags, H5S_sel_i
     assert(iter);
     assert(elem_size>0);
     assert(maxseq>0);
-    assert(maxbytes>0);
+    assert(maxelem>0);
     assert(nseq);
-    assert(nbytes);
+    assert(nelem);
     assert(off);
     assert(len);
 
-    /* Detemine the maximum # of elements to use for this operation */
-    max_elem=maxbytes/elem_size;
-
     /* Determine the actual number of elements to use */
     H5_CHECK_OVERFLOW(iter->elmt_left,hsize_t,size_t);
-    elem_used=MIN(max_elem,(size_t)iter->elmt_left);
+    elem_used=MIN(maxelem,(size_t)iter->elmt_left);
 
     /* Compute the offset in the dataset */
     off[0]=iter->u.all.offset*elem_size;
@@ -841,8 +837,8 @@ H5S_all_get_seq_list(const H5S_t UNUSED *space, unsigned UNUSED flags, H5S_sel_i
     /* Should only need one sequence for 'all' selections */
     *nseq=1;
 
-    /* Set the number of bytes used */
-    *nbytes=len[0];
+    /* Set the number of elements used */
+    *nelem=elem_used;
 
     /* Update the iterator */
     iter->elmt_left-=elem_used;
diff --git a/src/H5Shyper.c b/src/H5Shyper.c
index 1a1a10c..5c24473 100644
--- a/src/H5Shyper.c
+++ b/src/H5Shyper.c
@@ -267,6 +267,7 @@ H5S_hyper_iter_init(H5S_sel_iter_t *iter, const H5S_t *space, size_t elmt_size)
                         acc=1;
                     } /* end if */
                     else {
+                        /* All other dimensions */
                         iter->u.hyp.diminfo[curr_dim].start = tdiminfo[i].start;
                         iter->u.hyp.diminfo[curr_dim].stride = tdiminfo[i].stride;
                         iter->u.hyp.diminfo[curr_dim].count = tdiminfo[i].count;
@@ -1990,7 +1991,7 @@ done:
 herr_t
 H5S_hyper_serialize (const H5S_t *space, uint8_t *buf)
 {
-    const H5S_hyper_dim_t *diminfo;               /* Alias for dataspace's diminfo information */
+    const H5S_hyper_dim_t *diminfo;         /* Alias for dataspace's diminfo information */
     hsize_t tmp_count[H5O_LAYOUT_NDIMS];    /* Temporary hyperslab counts */
     hssize_t offset[H5O_LAYOUT_NDIMS];      /* Offset of element in dataspace */
     hssize_t start[H5O_LAYOUT_NDIMS];   /* Location of start of hyperslab */
@@ -2113,7 +2114,8 @@ H5S_hyper_serialize (const H5S_t *space, uint8_t *buf)
         len+=4;
 
         /* Add 8 bytes times the rank for each hyperslab selected */
-        H5_CHECK_OVERFLOW((8*space->extent.u.simple.rank*block_count),hssize_t,size_t);
+        H5_CHECK_OVERFLOW(block_count,hssize_t,hsize_t);
+        H5_CHECK_OVERFLOW((8*space->extent.u.simple.rank*(hsize_t)block_count),hsize_t,size_t);
         len+=(size_t)(8*space->extent.u.simple.rank*block_count);
 
         /* Encode each hyperslab in selection */
@@ -5315,7 +5317,6 @@ H5S_generate_hyperslab (H5S_t *space, H5S_seloper_t op,
     H5S_hyper_span_info_t *a_and_b=NULL;    /* Span tree for hyperslab spans in both old and new span trees */
     H5S_hyper_span_info_t *b_not_a=NULL;    /* Span tree for hyperslab spans in new span tree and not in old span tree */
     hssize_t nelem;             /* Number of elements in hyperslab span tree */
-    unsigned u;                    /* Counters */
     htri_t      status;         /* Status from internal calls */
     herr_t      ret_value=SUCCEED;       /* Return value */
 
@@ -5818,10 +5819,10 @@ done:
                                     position of interest in selection.
         size_t elem_size;       IN: Size of an element
         size_t maxseq;          IN: Maximum number of sequences to generate
-        size_t maxbytes;        IN: Maximum number of bytes to include in the
+        size_t maxelem;         IN: Maximum number of elements to include in the
                                     generated sequences
         size_t *nseq;           OUT: Actual number of sequences generated
-        size_t *nbytes;         OUT: Actual number of bytes in sequences generated
+        size_t *nelem;          OUT: Actual number of elements in sequences generated
         hsize_t *off;           OUT: Array of offsets
         size_t *len;            OUT: Array of lengths
  RETURNS
@@ -5839,7 +5840,7 @@ done:
 --------------------------------------------------------------------------*/
 static herr_t
 H5S_hyper_get_seq_list_gen(const H5S_t *space,H5S_sel_iter_t *iter,
-    size_t elem_size, size_t maxseq, size_t maxbytes, size_t *nseq, size_t *nbytes,
+    size_t elem_size, size_t maxseq, size_t maxelem, size_t *nseq, size_t *nelem,
     hsize_t *off, size_t *len)
 {
     H5S_hyper_span_t *curr_span;    /* Current hyperslab span node */
@@ -5851,9 +5852,10 @@ H5S_hyper_get_seq_list_gen(const H5S_t *space,H5S_sel_iter_t *iter,
     hssize_t *abs_arr;  /* Absolute hyperslab span position */
     hssize_t *off_arr;  /* Offset within the dataspace extent */
     size_t span_size=0; /* Number of bytes in current span to actually process */
-    size_t nelem;       /* Number of elements left to process */
+    size_t io_left;     /* Number of elements left to process */
     size_t io_bytes_left;   /* Number of bytes left to process */
     size_t start_io_bytes_left;   /* Initial number of bytes left to process */
+    size_t io_used;     /* Number of elements processed */
     size_t curr_seq=0; /* Number of sequence/offsets stored in the arrays */
     int ndims;         /* Number of dimensions of dataset */
     int fast_dim;      /* Rank of the fastest changing dimension for the dataspace */
@@ -5867,15 +5869,12 @@ H5S_hyper_get_seq_list_gen(const H5S_t *space,H5S_sel_iter_t *iter,
     assert(iter);
     assert(elem_size>0);
     assert(maxseq>0);
-    assert(maxbytes>0);
+    assert(maxelem>0);
     assert(nseq);
-    assert(nbytes);
+    assert(nelem);
     assert(off);
     assert(len);
 
-    /* "round" off the maxbytes allowed to a multiple of the element size */
-    maxbytes=(maxbytes/elem_size)*elem_size;
-
     /* Set the rank of the fastest changing dimension */
     ndims=space->extent.u.simple.rank;
     fast_dim=(ndims-1);
@@ -5887,9 +5886,9 @@ H5S_hyper_get_seq_list_gen(const H5S_t *space,H5S_sel_iter_t *iter,
     ispan=iter->u.hyp.span;
 
     /* Set the amount of elements to perform I/O on, etc. */
-    H5_CHECK_OVERFLOW( (iter->elmt_left*elem_size) ,hsize_t,size_t);
-    start_io_bytes_left=io_bytes_left=MIN(maxbytes,(size_t)(iter->elmt_left*elem_size));
-    nelem=io_bytes_left/elem_size;
+    H5_CHECK_OVERFLOW(iter->elmt_left,hsize_t,size_t);
+    io_left=MIN(maxelem,(size_t)iter->elmt_left);
+    start_io_bytes_left=io_bytes_left=io_left*elem_size;
 
     /* Compute the cumulative size of dataspace dimensions */
     for(i=fast_dim, acc=elem_size; i>=0; i--) {
@@ -6228,13 +6227,14 @@ partial_done:   /* Yes, goto's are evil, so sue me... :-) */
     } /* end while */
 
     /* Decrement number of elements left in iterator */
-    iter->elmt_left-=(nelem-(io_bytes_left/elem_size));
+    io_used=(io_left-(io_bytes_left/elem_size));
+    iter->elmt_left-=io_used;
 
     /* Set the number of sequences generated */
     *nseq=curr_seq;
 
-    /* Set the number of bytes used */
-    *nbytes=(start_io_bytes_left-io_bytes_left);
+    /* Set the number of elements used */
+    *nelem=io_used;
 
     FUNC_LEAVE_NOAPI(SUCCEED);
 } /* end H5S_hyper_get_seq_list_gen() */
@@ -6252,10 +6252,10 @@ partial_done:   /* Yes, goto's are evil, so sue me... :-) */
                                     position of interest in selection.
         size_t elem_size;       IN: Size of an element
         size_t maxseq;          IN: Maximum number of sequences to generate
-        size_t maxbytes;        IN: Maximum number of bytes to include in the
+        size_t maxelem;         IN: Maximum number of elements to include in the
                                     generated sequences
         size_t *nseq;           OUT: Actual number of sequences generated
-        size_t *nbytes;         OUT: Actual number of bytes in sequences generated
+        size_t *nelem;          OUT: Actual number of elements in sequences generated
         hsize_t *off;           OUT: Array of offsets
         size_t *len;            OUT: Array of lengths
  RETURNS
@@ -6273,7 +6273,7 @@ partial_done:   /* Yes, goto's are evil, so sue me... :-) */
 --------------------------------------------------------------------------*/
 static herr_t
 H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
-    size_t elmt_size, size_t maxseq, size_t maxbytes, size_t *nseq, size_t *nbytes,
+    size_t elmt_size, size_t maxseq, size_t maxelem, size_t *nseq, size_t *nelem,
     hsize_t *off, size_t *len)
 {
     hsize_t *mem_size;                  /* Size of the source buffer */
@@ -6307,9 +6307,6 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
     size_t nelmts;      /* Starting number of elements */
     size_t io_left;     /* The number of elements left in I/O operation */
     size_t start_io_left; /* The initial number of elements left in I/O operation */
-#ifndef NO_DUFFS_DEVICE
-    size_t duffs_index; /* Counting index for Duff's device */
-#endif /* NO_DUFFS_DEVICE */
 
     FUNC_ENTER_NOAPI_NOINIT_NOFUNC(H5S_hyper_get_seq_list_opt);
 
@@ -6318,9 +6315,9 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
     assert(iter);
     assert(elmt_size>0);
     assert(maxseq>0);
-    assert(maxbytes>0);
+    assert(maxelem>0);
     assert(nseq);
-    assert(nbytes);
+    assert(nelem);
     assert(off);
     assert(len);
 
@@ -6357,11 +6354,9 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
         acc*=mem_size[i];
     } /* end for */
 
-    /* Get the number of elements left in the selection */
-    H5_ASSIGN_OVERFLOW(io_left,iter->elmt_left,hsize_t,size_t);
-
     /* Calculate the number of elements to sequence through */
-    start_io_left=io_left=MIN(io_left,(maxbytes/elmt_size));
+    H5_CHECK_OVERFLOW(iter->elmt_left,hsize_t,size_t);
+    start_io_left=io_left=MIN((size_t)iter->elmt_left,maxelem);
 
     /* Check if we stopped in the middle of a sequence of elements */
     if((iter->u.hyp.off[fast_dim]-tdiminfo[fast_dim].start)%tdiminfo[fast_dim].stride!=0 ||
@@ -6552,118 +6547,55 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
 
         /* Read in data until an entire sequence can't be written out any longer */
         while(curr_rows>0) {
+
+#define DUFF_GUTS							      \
+    /* Store the sequence information */				      \
+    off[curr_seq]=loc;							      \
+    len[curr_seq]=actual_bytes;						      \
+									      \
+    /* Increment sequence count */					      \
+    curr_seq++;								      \
+									      \
+    /* Increment information to reflect block just processed */		      \
+    loc+=fast_dim_buf_off;
+
 #ifdef NO_DUFFS_DEVICE
             /* Loop over all the blocks in the fastest changing dimension */
             while(fast_dim_count>0) {
-                /* Store the sequence information */
-                off[curr_seq]=loc;
-                len[curr_seq]=actual_bytes;
-
-                /* Increment sequence count */
-                curr_seq++;
-
-                /* Increment information to reflect block just processed */
-                loc+=fast_dim_buf_off;
+                DUFF_GUTS
 
                 /* Decrement number of blocks */
                 fast_dim_count--;
             } /* end while */
 #else /* NO_DUFFS_DEVICE */
-            duffs_index = (fast_dim_count + 7) / 8;
-            switch (fast_dim_count % 8) {
-                case 0:
-                    do
-                      {
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 7:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 6:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 5:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 4:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 3:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 2:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                case 1:
-                        /* Store the sequence information */
-                        off[curr_seq]=loc;
-                        len[curr_seq]=actual_bytes;
-
-                        /* Increment sequence count */
-                        curr_seq++;
-
-                        /* Increment information to reflect block just processed */
-                        loc+=fast_dim_buf_off;
-
-                  } while (--duffs_index > 0);
-            } /* end switch */
+            {
+                size_t duffs_index; /* Counting index for Duff's device */
+
+                duffs_index = (fast_dim_count + 7) / 8;
+                switch (fast_dim_count % 8) {
+                    case 0:
+                        do
+                          {
+                            DUFF_GUTS
+                    case 7:
+                            DUFF_GUTS
+                    case 6:
+                            DUFF_GUTS
+                    case 5:
+                            DUFF_GUTS
+                    case 4:
+                            DUFF_GUTS
+                    case 3:
+                            DUFF_GUTS
+                    case 2:
+                            DUFF_GUTS
+                    case 1:
+                            DUFF_GUTS
+                      } while (--duffs_index > 0);
+                } /* end switch */
+            }
 #endif /* NO_DUFFS_DEVICE */
+#undef DUFF_GUTS
 
             /* Increment offset in destination buffer */
             loc += wrap[fast_dim];
@@ -6779,7 +6711,7 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
     *nseq=curr_seq;
 
     /* Set the number of bytes used */
-    *nbytes=(start_io_left-io_left)*elmt_size;
+    *nelem=start_io_left-io_left;
 
     FUNC_LEAVE_NOAPI(SUCCEED);
 } /* end H5S_hyper_get_seq_list_opt() */
@@ -6798,10 +6730,10 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
                                     position of interest in selection.
         size_t elem_size;       IN: Size of an element
         size_t maxseq;          IN: Maximum number of sequences to generate
-        size_t maxbytes;        IN: Maximum number of bytes to include in the
+        size_t maxelem;         IN: Maximum number of elements to include in the
                                     generated sequences
         size_t *nseq;           OUT: Actual number of sequences generated
-        size_t *nbytes;         OUT: Actual number of bytes in sequences generated
+        size_t *nelem;          OUT: Actual number of elements in sequences generated
         hsize_t *off;           OUT: Array of offsets
         size_t *len;            OUT: Array of lengths
  RETURNS
@@ -6819,7 +6751,7 @@ H5S_hyper_get_seq_list_opt(const H5S_t *space,H5S_sel_iter_t *iter,
 --------------------------------------------------------------------------*/
 herr_t
 H5S_hyper_get_seq_list(const H5S_t *space, unsigned UNUSED flags, H5S_sel_iter_t *iter,
-    size_t elem_size, size_t maxseq, size_t maxbytes, size_t *nseq, size_t *nbytes,
+    size_t elem_size, size_t maxseq, size_t maxelem, size_t *nseq, size_t *nelem,
     hsize_t *off, size_t *len)
 {
     herr_t ret_value;      /* return value */
@@ -6831,19 +6763,19 @@ H5S_hyper_get_seq_list(const H5S_t *space, unsigned UNUSED flags, H5S_sel_iter_t
     assert(iter);
     assert(elem_size>0);
     assert(maxseq>0);
-    assert(maxbytes>0);
+    assert(maxelem>0);
     assert(nseq);
-    assert(nbytes);
+    assert(nelem);
     assert(off);
     assert(len);
 
     /* Check for the special case of just one H5Sselect_hyperslab call made */
     if(space->select.sel_info.hslab.diminfo_valid)
         /* Use optimized call to generate sequence list */
-        ret_value=H5S_hyper_get_seq_list_opt(space,iter,elem_size,maxseq,maxbytes,nseq,nbytes,off,len);
+        ret_value=H5S_hyper_get_seq_list_opt(space,iter,elem_size,maxseq,maxelem,nseq,nelem,off,len);
     else
         /* Call the general sequence generator routine */
-        ret_value=H5S_hyper_get_seq_list_gen(space,iter,elem_size,maxseq,maxbytes,nseq,nbytes,off,len);
+        ret_value=H5S_hyper_get_seq_list_gen(space,iter,elem_size,maxseq,maxelem,nseq,nelem,off,len);
 
 done:
     FUNC_LEAVE_NOAPI(ret_value);
diff --git a/src/H5Snone.c b/src/H5Snone.c
index e07f5ae..28622c1 100644
--- a/src/H5Snone.c
+++ b/src/H5Snone.c
@@ -740,10 +740,10 @@ done:
                                     position of interest in selection.
         size_t elem_size;       IN: Size of an element
         size_t maxseq;          IN: Maximum number of sequences to generate
-        size_t maxbytes;        IN: Maximum number of bytes to include in the
+        size_t maxelem;         IN: Maximum number of elements to include in the
                                     generated sequences
         size_t *nseq;           OUT: Actual number of sequences generated
-        size_t *nbytes;         OUT: Actual number of bytes in sequences generated
+        size_t *nelem;          OUT: Actual number of elements in sequences generated
         hsize_t *off;           OUT: Array of offsets
         size_t *len;            OUT: Array of lengths
  RETURNS
@@ -761,7 +761,7 @@ done:
 --------------------------------------------------------------------------*/
 herr_t
 H5S_none_get_seq_list(const H5S_t UNUSED *space, unsigned UNUSED flags, H5S_sel_iter_t UNUSED *iter,
-    size_t UNUSED elem_size, size_t UNUSED maxseq, size_t UNUSED maxbytes, size_t *nseq, size_t *nbytes,
+    size_t UNUSED elem_size, size_t UNUSED maxseq, size_t UNUSED maxelem, size_t *nseq, size_t *nelem,
     hsize_t UNUSED *off, size_t UNUSED *len)
 {
     herr_t ret_value=SUCCEED;   /* Return value */
@@ -773,17 +773,17 @@ H5S_none_get_seq_list(const H5S_t UNUSED *space, unsigned UNUSED flags, H5S_sel_
     assert(iter);
     assert(elem_size>0);
     assert(maxseq>0);
-    assert(maxbytes>0);
+    assert(maxelem>0);
     assert(nseq);
-    assert(nbytes);
+    assert(nelem);
     assert(off);
     assert(len);
 
-    /* "none" selection don't generate sequences of bytes */
+    /* "none" selections don't generate sequences of bytes */
     *nseq=0;
 
-    /* The don't use any bytes, either */
-    *nbytes=0;
+    /* They don't use any elements, either */
+    *nelem=0;
 
 done:
     FUNC_LEAVE_NOAPI(ret_value);
diff --git a/src/H5Spoint.c b/src/H5Spoint.c
index 9b469c5..18ac92f 100644
--- a/src/H5Spoint.c
+++ b/src/H5Spoint.c
@@ -1312,10 +1312,10 @@ done:
                                     position of interest in selection.
         size_t elem_size;       IN: Size of an element
         size_t maxseq;          IN: Maximum number of sequences to generate
-        size_t maxbytes;        IN: Maximum number of bytes to include in the
+        size_t maxelem;         IN: Maximum number of elements to include in the
                                     generated sequences
         size_t *nseq;           OUT: Actual number of sequences generated
-        size_t *nbytes;         OUT: Actual number of bytes in sequences generated
+        size_t *nelem;          OUT: Actual number of elements in sequences generated
         hsize_t *off;           OUT: Array of offsets
         size_t *len;            OUT: Array of lengths
  RETURNS
@@ -1333,11 +1333,11 @@ done:
 --------------------------------------------------------------------------*/
 herr_t
 H5S_point_get_seq_list(const H5S_t *space, unsigned flags, H5S_sel_iter_t *iter,
-    size_t elem_size, size_t maxseq, size_t maxbytes, size_t *nseq, size_t *nbytes,
+    size_t elem_size, size_t maxseq, size_t maxelem, size_t *nseq, size_t *nelem,
     hsize_t *off, size_t *len)
 {
-    hsize_t bytes_left;         /* The number of bytes left in the selection */
-    hsize_t start_bytes_left;   /* The initial number of bytes left in the selection */
+    size_t io_left;             /* The number of bytes left in the selection */
+    size_t start_io_left;       /* The initial number of bytes left in the selection */
     H5S_pnt_node_t *node;       /* Point node */
     hsize_t dims[H5O_LAYOUT_NDIMS];     /* Total size of memory buf */
     int	ndims;                  /* Dimensionality of space*/
@@ -1354,17 +1354,15 @@ H5S_point_get_seq_list(const H5S_t *space, unsigned flags, H5S_sel_iter_t *iter,
     assert(iter);
     assert(elem_size>0);
     assert(maxseq>0);
-    assert(maxbytes>0);
+    assert(maxelem>0);
     assert(nseq);
-    assert(nbytes);
+    assert(nelem);
     assert(off);
     assert(len);
 
-    /* "round" off the maxbytes allowed to a multiple of the element size */
-    maxbytes=(maxbytes/elem_size)*elem_size;
-
     /* Choose the minimum number of bytes to sequence through */
-    start_bytes_left=bytes_left=MIN(iter->elmt_left*elem_size,maxbytes);
+    H5_CHECK_OVERFLOW(iter->elmt_left,hsize_t,size_t);
+    start_io_left=io_left=MIN(iter->elmt_left,maxelem);
 
     /* Get the dataspace dimensions */
     if ((ndims=H5S_get_simple_extent_dims (space, dims, NULL))<0)
@@ -1411,8 +1409,8 @@ H5S_point_get_seq_list(const H5S_t *space, unsigned flags, H5S_sel_iter_t *iter,
             curr_seq++;
         } /* end else */
 
-        /* Decrement number of bytes left to process */
-        bytes_left-=elem_size;
+        /* Decrement number of elements left to process */
+        io_left--;
 
         /* Move the iterator */
         iter->u.pnt.curr=node->next;
@@ -1422,8 +1420,8 @@ H5S_point_get_seq_list(const H5S_t *space, unsigned flags, H5S_sel_iter_t *iter,
         if(curr_seq==maxseq)
             break;
 
-        /* Check if we're finished with all the bytes available */
-        if(bytes_left==0)
+        /* Check if we're finished with all the elements available */
+        if(io_left==0)
             break;
 
         /* Advance to the next point */
@@ -1433,9 +1431,8 @@ H5S_point_get_seq_list(const H5S_t *space, unsigned flags, H5S_sel_iter_t *iter,
     /* Set the number of sequences generated */
     *nseq=curr_seq;
 
-    /* Set the number of bytes used */
-    H5_CHECK_OVERFLOW( (start_bytes_left-bytes_left) ,hsize_t,size_t);
-    *nbytes=(size_t)(start_bytes_left-bytes_left);
+    /* Set the number of elements used */
+    *nelem=start_io_left-io_left;
 
 done:
     FUNC_LEAVE_NOAPI(ret_value);
diff --git a/src/H5Sselect.c b/src/H5Sselect.c
index 10774d2..5031921 100644
--- a/src/H5Sselect.c
+++ b/src/H5Sselect.c
@@ -913,8 +913,8 @@ H5S_select_iterate(void *buf, hid_t type_id, const H5S_t *space, H5D_operator_t
     size_t curr_len;            /* Length of bytes left to process in sequence */
     size_t nseq;                /* Number of sequences generated */
     size_t curr_seq;            /* Current sequnce being worked on */
-    size_t nbytes;              /* Number of bytes used in sequences */
-    size_t max_bytes;           /* Maximum number of bytes allowed in sequences */
+    size_t nelem;               /* Number of elements used in sequences */
+    size_t max_elem;            /* Maximum number of elements allowed in sequences */
     size_t elmt_size;           /* Datatype size */
     int ndims;                  /* Number of dimensions in dataspace */
     int	i;			/* Local Index variable */
@@ -941,7 +941,7 @@ H5S_select_iterate(void *buf, hid_t type_id, const H5S_t *space, H5D_operator_t
     iter_init=1;	/* Selection iteration info has been initialized */
 
     /* Get the number of elements in selection */
-    if((nelmts = (*space->select.get_npoints)(space))<0)
+    if((nelmts = H5S_get_select_npoints(space))<0)
         HGOTO_ERROR (H5E_DATASPACE, H5E_CANTCOUNT, FAIL, "can't get number of elements selected");
 
     /* Get the rank of the dataspace */
@@ -955,12 +955,12 @@ H5S_select_iterate(void *buf, hid_t type_id, const H5S_t *space, H5D_operator_t
     space_size[ndims]=elmt_size;
 
     /* Compute the maximum number of bytes required */
-    H5_ASSIGN_OVERFLOW(max_bytes,nelmts*elmt_size,hsize_t,size_t);
+    H5_ASSIGN_OVERFLOW(max_elem,nelmts,hssize_t,size_t);
 
     /* Loop, while elements left in selection */
-    while(max_bytes>0 && user_ret==0) {
+    while(max_elem>0 && user_ret==0) {
         /* Get the sequences of bytes */
-        if((*space->select.get_seq_list)(space,0,&iter,elmt_size,H5D_XFER_HYPER_VECTOR_SIZE_DEF,max_bytes,&nseq,&nbytes,off,len)<0)
+        if((*space->select.get_seq_list)(space,0,&iter,elmt_size,H5D_XFER_HYPER_VECTOR_SIZE_DEF,max_elem,&nseq,&nelem,off,len)<0)
             HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
         /* Loop, while sequences left to process */
@@ -994,8 +994,7 @@ H5S_select_iterate(void *buf, hid_t type_id, const H5S_t *space, H5D_operator_t
         } /* end for */
 
         /* Decrement number of elements left to process */
-        assert((nbytes%elmt_size)==0);
-        max_bytes-=nbytes;
+        max_elem-=nelem;
     } /* end while */
 
     /* Set return value */
@@ -1337,8 +1336,8 @@ H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *_buf)
     size_t len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];           /* Array to store sequence lengths */
     size_t nseq;                /* Number of sequences generated */
     size_t curr_seq;            /* Current sequnce being worked on */
-    size_t nbytes;              /* Number of bytes used in sequences */
-    size_t max_bytes;           /* Total number of bytes in selection */
+    size_t nelem;               /* Number of elements used in sequences */
+    size_t max_elem;            /* Total number of elements in selection */
     herr_t ret_value=SUCCEED;   /* return value */
 
     FUNC_ENTER_NOAPI(H5S_select_fill, FAIL);
@@ -1360,17 +1359,16 @@ H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *_buf)
     iter_init=1;	/* Selection iteration info has been initialized */
 
     /* Get the number of elements in selection */
-    if((nelmts = (*space->select.get_npoints)(space))<0)
+    if((nelmts = H5S_get_select_npoints(space))<0)
         HGOTO_ERROR (H5E_DATASPACE, H5E_CANTCOUNT, FAIL, "can't get number of elements selected");
 
     /* Compute the number of bytes to process */
-    H5_CHECK_OVERFLOW(nelmts,hssize_t,size_t);
-    max_bytes=(size_t)nelmts*fill_size;
+    H5_ASSIGN_OVERFLOW(max_elem,nelmts,hssize_t,size_t);
 
     /* Loop, while elements left in selection */
-    while(max_bytes>0) {
+    while(max_elem>0) {
         /* Get the sequences of bytes */
-        if((*space->select.get_seq_list)(space,0,&iter,fill_size,H5D_XFER_HYPER_VECTOR_SIZE_DEF,max_bytes,&nseq,&nbytes,off,len)<0)
+        if((*space->select.get_seq_list)(space,0,&iter,fill_size,H5D_XFER_HYPER_VECTOR_SIZE_DEF,max_elem,&nseq,&nelem,off,len)<0)
             HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
         /* Loop over sequences */
@@ -1383,8 +1381,8 @@ H5S_select_fill(void *_fill, size_t fill_size, const H5S_t *space, void *_buf)
             H5V_array_fill(buf, fill, fill_size, (len[curr_seq]/fill_size));
         } /* end for */
 
-        /* Decrement number of bytes left to process */
-        max_bytes-=nbytes;
+        /* Decrement number of elements left to process */
+        max_elem-=nelem;
     } /* end while */
 
 done:
@@ -1435,10 +1433,10 @@ H5S_select_fscat (H5F_t *f, struct H5O_layout_t *layout,
     size_t dset_curr_seq;          /* "Current sequence" in dataset */
     size_t _len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];              /* Array to store sequence lengths */
     size_t *len=NULL;              /* Array to store sequence lengths */
-    size_t mem_len;                /* Length of sequence in memory */
-    size_t maxbytes;               /* Number of bytes in the buffer */
+    size_t orig_mem_len, mem_len;  /* Length of sequence in memory */
+    size_t maxelem;                /* Number of elements in the buffer */
     size_t  nseq;                  /* Number of sequences generated */
-    size_t  nbytes;                /* Number of bytes used in sequences */
+    size_t  nelem;                 /* Number of elements used in sequences */
     herr_t  ret_value=SUCCEED;     /* Return value */
 
     FUNC_ENTER_NOAPI(H5S_select_fscat, FAIL);
@@ -1466,19 +1464,18 @@ H5S_select_fscat (H5F_t *f, struct H5O_layout_t *layout,
         off=_off;
     } /* end else */
 
-
     /* Compute the number of bytes available in buffer */
-    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+    H5_ASSIGN_OVERFLOW(maxelem,nelmts,hsize_t,size_t);
 
     /* Loop until all elements are written */
-    while(maxbytes>0) {
+    while(maxelem>0) {
         /* Get list of sequences for selection to write */
-        if((*space->select.get_seq_list)(space,H5S_GET_SEQ_LIST_SORTED,iter,elmt_size,dxpl_cache->vec_size,maxbytes,&nseq,&nbytes,off,len)<0)
+        if((*space->select.get_seq_list)(space,H5S_GET_SEQ_LIST_SORTED,iter,elmt_size,dxpl_cache->vec_size,maxelem,&nseq,&nelem,off,len)<0)
             HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
         /* Reset the current sequence information */
         mem_curr_seq=dset_curr_seq=0;
-        mem_len=nbytes;
+        orig_mem_len=mem_len=nelem*elmt_size;
         mem_off=0;
 
         /* Write sequence list out */
@@ -1486,11 +1483,10 @@ H5S_select_fscat (H5F_t *f, struct H5O_layout_t *layout,
             HGOTO_ERROR(H5E_DATASPACE, H5E_WRITEERROR, FAIL, "write error");
 
         /* Update buffer */
-        buf += nbytes;
+        buf += orig_mem_len;
 
         /* Decrement number of elements left to process */
-        assert(nbytes%elmt_size==0);
-        maxbytes -= nbytes;
+        maxelem -= nelem;
     } /* end while */
 
 done:
@@ -1542,10 +1538,10 @@ H5S_select_fgath (H5F_t *f, const struct H5O_layout_t *layout,
     size_t dset_curr_seq;       /* "Current sequence" in dataset */
     size_t _len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];           /* Array to store sequence lengths */
     size_t *len=NULL;           /* Pointer to sequence lengths */
-    size_t mem_len;             /* Length of sequence in memory */
-    size_t maxbytes;            /* Number of bytes in the buffer */
+    size_t orig_mem_len, mem_len;       /* Length of sequence in memory */
+    size_t maxelem;             /* Number of elements in the buffer */
     size_t nseq;                /* Number of sequences generated */
-    size_t nbytes;              /* Number of bytes used in sequences */
+    size_t nelem;               /* Number of elements used in sequences */
     hsize_t ret_value=nelmts;   /* Return value */
 
     FUNC_ENTER_NOAPI(H5S_select_fgath, 0);
@@ -1572,18 +1568,18 @@ H5S_select_fgath (H5F_t *f, const struct H5O_layout_t *layout,
         off=_off;
     } /* end else */
 
-    /* Compute the number of bytes available in buffer */
-    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+    /* Compute the number of elements available in buffer */
+    H5_ASSIGN_OVERFLOW(maxelem,nelmts,hsize_t,size_t);
 
     /* Loop until all elements are written */
-    while(maxbytes>0) {
+    while(maxelem>0) {
         /* Get list of sequences for selection to write */
-        if((*space->select.get_seq_list)(space,H5S_GET_SEQ_LIST_SORTED,iter,elmt_size,dxpl_cache->vec_size,maxbytes,&nseq,&nbytes,off,len)<0)
+        if((*space->select.get_seq_list)(space,H5S_GET_SEQ_LIST_SORTED,iter,elmt_size,dxpl_cache->vec_size,maxelem,&nseq,&nelem,off,len)<0)
             HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, 0, "sequence length generation failed");
 
         /* Reset the current sequence information */
         mem_curr_seq=dset_curr_seq=0;
-        mem_len=nbytes;
+        orig_mem_len=mem_len=nelem*elmt_size;
         mem_off=0;
 
         /* Read sequence list in */
@@ -1591,11 +1587,10 @@ H5S_select_fgath (H5F_t *f, const struct H5O_layout_t *layout,
             HGOTO_ERROR(H5E_DATASPACE, H5E_READERROR, 0, "read error");
 
         /* Update buffer */
-        buf += nbytes;
+        buf += orig_mem_len;
 
         /* Decrement number of elements left to process */
-        assert(nbytes%elmt_size==0);
-        maxbytes -= nbytes;
+        maxelem -= nelem;
     } /* end while */
 
 done:
@@ -1638,10 +1633,10 @@ H5S_select_mscat (const void *_tscat_buf, size_t elmt_size, const H5S_t *space,
     size_t _len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];           /* Array to store sequence lengths */
     size_t *len=NULL;           /* Pointer to sequence lengths */
     size_t curr_len;            /* Length of bytes left to process in sequence */
-    size_t maxbytes;            /* Number of bytes in the buffer */
+    size_t maxelem;             /* Number of elements in the buffer */
     size_t nseq;                /* Number of sequences generated */
     size_t curr_seq;            /* Current sequence being processed */
-    size_t nbytes;              /* Number of bytes used in sequences */
+    size_t nelem;               /* Number of elements used in sequences */
     herr_t ret_value=SUCCEED;   /* Number of elements scattered */
 
     FUNC_ENTER_NOAPI(H5S_select_mscat, FAIL);
@@ -1666,13 +1661,13 @@ H5S_select_mscat (const void *_tscat_buf, size_t elmt_size, const H5S_t *space,
         off=_off;
     } /* end else */
 
-    /* Compute the number of bytes available in buffer */
-    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+    /* Compute the number of elements available in buffer */
+    H5_ASSIGN_OVERFLOW(maxelem,nelmts,hsize_t,size_t);
 
     /* Loop until all elements are written */
-    while(maxbytes>0) {
+    while(maxelem>0) {
         /* Get list of sequences for selection to write */
-        if((*space->select.get_seq_list)(space,0,iter,elmt_size,dxpl_cache->vec_size,maxbytes,&nseq,&nbytes,off,len)<0)
+        if((*space->select.get_seq_list)(space,0,iter,elmt_size,dxpl_cache->vec_size,maxelem,&nseq,&nelem,off,len)<0)
             HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, 0, "sequence length generation failed");
 
         /* Loop, while sequences left to process */
@@ -1687,8 +1682,7 @@ H5S_select_mscat (const void *_tscat_buf, size_t elmt_size, const H5S_t *space,
         } /* end for */
 
         /* Decrement number of elements left to process */
-        assert(nbytes%elmt_size==0);
-        maxbytes -= nbytes;
+        maxelem -= nelem;
     } /* end while */
 
 done:
@@ -1733,10 +1727,10 @@ H5S_select_mgath (const void *_buf, size_t elmt_size, const H5S_t *space,
     size_t _len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];           /* Array to store sequence lengths */
     size_t *len=NULL;           /* Pointer to sequence lengths */
     size_t curr_len;            /* Length of bytes left to process in sequence */
-    size_t maxbytes;            /* Number of bytes in the buffer */
+    size_t maxelem;             /* Number of elements in the buffer */
     size_t nseq;                /* Number of sequences generated */
     size_t curr_seq;            /* Current sequence being processed */
-    size_t nbytes;              /* Number of bytes used in sequences */
+    size_t nelem;               /* Number of elements used in sequences */
     hsize_t ret_value=nelmts;   /* Number of elements gathered */
 
     FUNC_ENTER_NOAPI(H5S_select_mgath, 0);
@@ -1761,13 +1755,13 @@ H5S_select_mgath (const void *_buf, size_t elmt_size, const H5S_t *space,
         off=_off;
     } /* end else */
 
-    /* Compute the number of bytes available in buffer */
-    H5_ASSIGN_OVERFLOW(maxbytes,nelmts*elmt_size,hsize_t,size_t);
+    /* Compute the number of elements available in buffer */
+    H5_ASSIGN_OVERFLOW(maxelem,nelmts,hsize_t,size_t);
 
     /* Loop until all elements are written */
-    while(maxbytes>0) {
+    while(maxelem>0) {
         /* Get list of sequences for selection to write */
-        if((*space->select.get_seq_list)(space,0,iter,elmt_size,dxpl_cache->vec_size,maxbytes,&nseq,&nbytes,off,len)<0)
+        if((*space->select.get_seq_list)(space,0,iter,elmt_size,dxpl_cache->vec_size,maxelem,&nseq,&nelem,off,len)<0)
             HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, 0, "sequence length generation failed");
 
         /* Loop, while sequences left to process */
@@ -1782,8 +1776,7 @@ H5S_select_mgath (const void *_buf, size_t elmt_size, const H5S_t *space,
         } /* end for */
 
         /* Decrement number of elements left to process */
-        assert(nbytes%elmt_size==0);
-        maxbytes -= nbytes;
+        maxelem -= nelem;
     } /* end while */
 
 done:
@@ -1829,11 +1822,11 @@ H5S_select_read(H5F_t *f, const H5O_layout_t *layout, const H5D_dcpl_cache_t *dc
     size_t *mem_len=NULL;       /* Pointer to sequence lengths in memory */
     size_t _file_len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];      /* Array to store sequence lengths in the file */
     size_t *file_len=NULL;      /* Pointer to sequence lengths in the file */
-    size_t maxbytes;            /* Number of bytes in selection */
+    size_t maxelem;             /* Number of elements in selection */
     size_t mem_nseq;            /* Number of sequences generated in the file */
     size_t file_nseq;           /* Number of sequences generated in memory */
-    size_t mem_nbytes;          /* Number of bytes used in memory sequences */
-    size_t file_nbytes;         /* Number of bytes used in file sequences */
+    size_t mem_nelem;           /* Number of elements used in memory sequences */
+    size_t file_nelem;          /* Number of elements used in file sequences */
     size_t curr_mem_seq;        /* Current memory sequence to operate on */
     size_t curr_file_seq;       /* Current file sequence to operate on */
     ssize_t tmp_file_len;       /* Temporary number of bytes in file sequence */
@@ -1878,11 +1871,11 @@ H5S_select_read(H5F_t *f, const H5O_layout_t *layout, const H5D_dcpl_cache_t *dc
     /* Get number of bytes in selection */
 #ifndef NDEBUG
     {
-        hsize_t tmp_maxbytes=(*file_space->select.get_npoints)(file_space)*elmt_size;
-        H5_ASSIGN_OVERFLOW(maxbytes,tmp_maxbytes,hsize_t,size_t);
+        hsize_t tmp_maxelem=H5S_get_select_npoints(file_space);
+        H5_ASSIGN_OVERFLOW(maxelem,tmp_maxelem,hsize_t,size_t);
     }
 #else /* NDEBUG */
-    maxbytes=(size_t)((*file_space->select.get_npoints)(file_space)*elmt_size);
+    maxelem=(size_t)H5S_get_select_npoints(file_space);
 #endif /* NDEBUG */
 
     /* Initialize sequence counts */
@@ -1890,11 +1883,11 @@ H5S_select_read(H5F_t *f, const H5O_layout_t *layout, const H5D_dcpl_cache_t *dc
     mem_nseq=file_nseq=0;
 
     /* Loop, until all bytes are processed */
-    while(maxbytes>0) {
+    while(maxelem>0) {
         /* Check if more file sequences are needed */
         if(curr_file_seq>=file_nseq) {
             /* Get sequences for file selection */
-            if((*file_space->select.get_seq_list)(file_space,H5S_GET_SEQ_LIST_SORTED,&file_iter,elmt_size,dxpl_cache->vec_size,maxbytes,&file_nseq,&file_nbytes,file_off,file_len)<0)
+            if((*file_space->select.get_seq_list)(file_space,H5S_GET_SEQ_LIST_SORTED,&file_iter,elmt_size,dxpl_cache->vec_size,maxelem,&file_nseq,&file_nelem,file_off,file_len)<0)
                 HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
             /* Start at the beginning of the sequences again */
@@ -1904,7 +1897,7 @@ H5S_select_read(H5F_t *f, const H5O_layout_t *layout, const H5D_dcpl_cache_t *dc
         /* Check if more memory sequences are needed */
         if(curr_mem_seq>=mem_nseq) {
             /* Get sequences for memory selection */
-            if((*mem_space->select.get_seq_list)(mem_space,0,&mem_iter,elmt_size,dxpl_cache->vec_size,maxbytes,&mem_nseq,&mem_nbytes,mem_off,mem_len)<0)
+            if((*mem_space->select.get_seq_list)(mem_space,0,&mem_iter,elmt_size,dxpl_cache->vec_size,maxelem,&mem_nseq,&mem_nelem,mem_off,mem_len)<0)
                 HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
             /* Start at the beginning of the sequences again */
@@ -1924,8 +1917,9 @@ HDfprintf(stderr,"%s: mem_off[%Zu]=%Hu, mem_len[%Zu]=%Zu\n",FUNC,curr_mem_seq,me
                 buf))<0)
             HGOTO_ERROR(H5E_DATASPACE, H5E_READERROR, FAIL, "read error");
 
-        /* Decrement number of bytes left to process */
-        maxbytes-=tmp_file_len;
+        /* Decrement number of elements left to process */
+        assert((tmp_file_len%elmt_size)==0);
+        maxelem-=(tmp_file_len/elmt_size);
     } /* end while */
 
 done:
@@ -1988,11 +1982,11 @@ H5S_select_write(H5F_t *f, H5O_layout_t *layout, const H5D_dcpl_cache_t *dcpl_ca
     size_t *mem_len=NULL;       /* Pointer to sequence lengths in memory */
     size_t _file_len[H5D_XFER_HYPER_VECTOR_SIZE_DEF];      /* Array to store sequence lengths in the file */
     size_t *file_len=NULL;      /* Pointer to sequence lengths in the file */
-    size_t maxbytes;            /* Number of bytes in selection */
+    size_t maxelem;             /* Number of elements in selection */
     size_t mem_nseq;            /* Number of sequences generated in the file */
     size_t file_nseq;           /* Number of sequences generated in memory */
-    size_t mem_nbytes;          /* Number of bytes used in memory sequences */
-    size_t file_nbytes;         /* Number of bytes used in file sequences */
+    size_t mem_nelem;           /* Number of elements used in memory sequences */
+    size_t file_nelem;          /* Number of elements used in file sequences */
     size_t curr_mem_seq;        /* Current memory sequence to operate on */
     size_t curr_file_seq;       /* Current file sequence to operate on */
     ssize_t tmp_file_len;       /* Temporary number of bytes in file sequence */
@@ -2046,11 +2040,11 @@ H5S_select_write(H5F_t *f, H5O_layout_t *layout, const H5D_dcpl_cache_t *dcpl_ca
     /* Get number of bytes in selection */
 #ifndef NDEBUG
     {
-        hsize_t tmp_maxbytes=(*file_space->select.get_npoints)(file_space)*elmt_size;
-        H5_ASSIGN_OVERFLOW(maxbytes,tmp_maxbytes,hsize_t,size_t);
+        hsize_t tmp_maxelem=H5S_get_select_npoints(file_space);
+        H5_ASSIGN_OVERFLOW(maxelem,tmp_maxelem,hsize_t,size_t);
     }
 #else /* NDEBUG */
-    maxbytes=(size_t)((*file_space->select.get_npoints)(file_space)*elmt_size);
+    maxelem=(size_t)H5S_get_select_npoints(file_space);
 #endif /* NDEBUG */
 
     /* Initialize sequence counts */
@@ -2058,7 +2052,7 @@ H5S_select_write(H5F_t *f, H5O_layout_t *layout, const H5D_dcpl_cache_t *dcpl_ca
     mem_nseq=file_nseq=0;
 
     /* Loop, until all bytes are processed */
-    while(maxbytes>0) {
+    while(maxelem>0) {
         /* Check if more file sequences are needed */
 #ifdef QAK
 {
@@ -2071,7 +2065,7 @@ H5S_select_write(H5F_t *f, H5O_layout_t *layout, const H5D_dcpl_cache_t *dcpl_ca
 #endif /* QAK */
         if(curr_file_seq>=file_nseq) {
             /* Get sequences for file selection */
-            if((*file_space->select.get_seq_list)(file_space,H5S_GET_SEQ_LIST_SORTED,&file_iter,elmt_size,dxpl_cache->vec_size,maxbytes,&file_nseq,&file_nbytes,file_off,file_len)<0)
+            if((*file_space->select.get_seq_list)(file_space,H5S_GET_SEQ_LIST_SORTED,&file_iter,elmt_size,dxpl_cache->vec_size,maxelem,&file_nseq,&file_nelem,file_off,file_len)<0)
                 HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
             /* Start at the beginning of the sequences again */
@@ -2090,7 +2084,7 @@ H5S_select_write(H5F_t *f, H5O_layout_t *layout, const H5D_dcpl_cache_t *dcpl_ca
         /* Check if more memory sequences are needed */
         if(curr_mem_seq>=mem_nseq) {
             /* Get sequences for memory selection */
-            if((*mem_space->select.get_seq_list)(mem_space,0,&mem_iter,elmt_size,dxpl_cache->vec_size,maxbytes,&mem_nseq,&mem_nbytes,mem_off,mem_len)<0)
+            if((*mem_space->select.get_seq_list)(mem_space,0,&mem_iter,elmt_size,dxpl_cache->vec_size,maxelem,&mem_nseq,&mem_nelem,mem_off,mem_len)<0)
                 HGOTO_ERROR (H5E_INTERNAL, H5E_UNSUPPORTED, FAIL, "sequence length generation failed");
 
             /* Start at the beginning of the sequences again */
@@ -2125,8 +2119,9 @@ for(u=curr_mem_seq; u<mem_nseq; u++)
                 buf))<0)
             HGOTO_ERROR(H5E_DATASPACE, H5E_WRITEERROR, FAIL, "write error");
 
-        /* Decrement number of bytes left to process */
-        maxbytes-=tmp_file_len;
+        /* Decrement number of elements left to process */
+        assert((tmp_file_len%elmt_size)==0);
+        maxelem-=(tmp_file_len/elmt_size);
     } /* end while */
 
 done: