[svn-r4181] Purpose:

    Bug Fix, Code Cleanup, Code Optimization, etc.
Description:
    Fold in the hyperslab speedups, clean up compile warnings and change a
    few things from using 'unsigned' or 'hsize_t' to use 'size_t' instead.
Platforms tested:
    FreeBSD 4.3 (hawkwind), Solaris 2.7 (arabica), Irix64 6.5 (modi4)

1 files changed, 870 insertions, 272 deletions

diff --git a/src/H5Dcontig.c b/src/H5Dcontig.c
index e08707e..8c3055f 100644
--- a/src/H5Dcontig.c
+++ b/src/H5Dcontig.c
@@ -39,82 +39,447 @@ static intn		interface_initialize_g = 0;
  *              Thursday, September 28, 2000
  *
  * Modifications:
+ *              Re-written in terms of the new readv call, QAK, 7/7/01
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_contig_read(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, hsize_t size, hid_t dxpl_id,
-	       void *buf/*out*/)
+H5F_contig_read(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr,
+    size_t size, hid_t dxpl_id, void *buf/*out*/)
 {
-    haddr_t abs_eoa;		        /* Absolute end of file address		*/
-    haddr_t rel_eoa;		        /* Relative end of file address		*/
+    hsize_t offset=0;   /* Offset for vector call */
    
     FUNC_ENTER(H5F_contig_read, FAIL);
 
     /* Check args */
     assert(f);
-    assert(size<SIZET_MAX);
+    assert(buf);
+
+    if (H5F_contig_readv(f, max_data, type, addr, 1, &size, &offset, dxpl_id, buf)<0)
+        HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL, "vector read failed");
+
+    FUNC_LEAVE(SUCCEED);
+}   /* end H5F_contig_read() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5F_contig_write
+ *
+ * Purpose:	Writes some data from a dataset into a buffer.
+ *		The data is contiguous.	 The address is relative to the base
+ *		address for the file.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Thursday, September 28, 2000
+ *
+ * Modifications:
+ *              Re-written in terms of the new readv call, QAK, 7/7/01
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5F_contig_write(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, size_t size,
+        hid_t dxpl_id, const void *buf)
+{
+    hsize_t offset=0;   /* Offset for vector call */
+
+    FUNC_ENTER(H5F_contig_write, FAIL);
+
+    assert (f);
+    assert (buf);
+
+    if (H5F_contig_writev(f, max_data, type, addr, 1, &size, &offset, dxpl_id, buf)<0)
+        HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL, "vector write failed");
+
+    FUNC_LEAVE(SUCCEED);
+}   /* end H5F_contig_write() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5F_contig_readv
+ *
+ * Purpose:	Reads some data vectors from a dataset into a buffer.
+ *		The data is contiguous.	 The address is the start of the dataset,
+ *              relative to the base address for the file and the offsets and
+ *              sequence lengths are in bytes.
+ *
+ * Return:	Non-negative on success/Negative on failure
+ *
+ * Programmer:	Quincey Koziol
+ *              Friday, May 3, 2001
+ *
+ * Notes:
+ *      Offsets in the sequences must be monotonically increasing
+ *
+ * Modifications:
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5F_contig_readv(H5F_t *f, hsize_t _max_data, H5FD_mem_t type, haddr_t _addr,
+    size_t nseq, size_t size_arr[], hsize_t offset_arr[], hid_t dxpl_id,
+    void *_buf/*out*/)
+{
+    unsigned char *buf=(unsigned char *)_buf;      /* Pointer to buffer to fill */
+    haddr_t abs_eoa;	        /* Absolute end of file address		*/
+    haddr_t rel_eoa;	        /* Relative end of file address		*/
+    haddr_t addr;               /* Actual address to read */
+    hsize_t max_data;           /* Actual maximum size of data to cache */
+    size_t size;                /* Size of sequence in bytes */
+    size_t u;                   /* Counting variable */
+#ifndef SLOW_WAY
+    size_t max_seq;        /* Maximum sequence to copy */
+    haddr_t temp_end;      /* Temporary end of buffer variable */
+    size_t max_search;     /* Maximum number of sequences to search */
+    size_t mask;           /* Bit mask */
+    intn bit_loc;          /* Bit location of the leftmost '1' in max_search */
+    size_t *size_arr_p;    /* Pointer into the size array */
+    hsize_t *offset_arr_p; /* Pointer into the offset array */
+#endif /* SLOW_WAY */
+   
+    FUNC_ENTER(H5F_contig_readv, FAIL);
+
+    /* Check args */
+    assert(f);
     assert(buf);
 
     /* Check if data sieving is enabled */
     if(f->shared->lf->feature_flags&H5FD_FEAT_DATA_SIEVE) {
-        /* Try reading from the data sieve buffer */
-        if(f->shared->sieve_buf) {
-            haddr_t sieve_start, sieve_end;     /* Start & end locations of sieve buffer */
-            haddr_t contig_end;         /* End locations of block to write */
-            hsize_t sieve_size;                 /* size of sieve buffer */
-
-            /* Stash local copies of these value */
-            sieve_start=f->shared->sieve_loc;
-            sieve_size=f->shared->sieve_size;
-            sieve_end=sieve_start+sieve_size;
-            contig_end=addr+size-1;
-            
-            /* If entire read is within the sieve buffer, read it from the buffer */
-            if(addr>=sieve_start && contig_end<sieve_end) {
-                /* Grab the data out of the buffer */
-                assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                HDmemcpy(buf,f->shared->sieve_buf+(addr-sieve_start),(size_t)size);
-            } /* end if */
-            /* Entire request is not within this data sieve buffer */
-            else {
-                /* Check if we can actually hold the I/O request in the sieve buffer */
-                if(size>f->shared->sieve_buf_size) {
-                    /* Check for any overlap with the current sieve buffer */
-                    if((sieve_start>=addr && sieve_start<(contig_end+1))
-                            || ((sieve_end-1)>=addr && (sieve_end-1)<(contig_end+1))) {
-                        /* Flush the sieve buffer, if it's dirty */
-                        if(f->shared->sieve_dirty) {
-                            /* Write to file */
-                            if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                                HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                                  "block write failed");
+
+        /* Outer loop, guarantees working through all the sequences */
+        for(u=0; u<nseq; ) {
+
+            /* Try reading from the data sieve buffer */
+            if(f->shared->sieve_buf) {
+                haddr_t sieve_start, sieve_end;     /* Start & end locations of sieve buffer */
+                haddr_t contig_end;             /* End locations of block to write */
+                size_t sieve_size;              /* size of sieve buffer */
+
+                /* Stash local copies of these value */
+                sieve_start=f->shared->sieve_loc;
+                sieve_size=f->shared->sieve_size;
+                sieve_end=sieve_start+sieve_size;
+                
+                /* Next-outer loop works through sequences as fast as possible */
+                for(; u<nseq; ) {
+                    size=size_arr[u];
+                    addr=_addr+offset_arr[u];
+
+                    /* Compute end of sequence to retrieve */
+                    contig_end=addr+size-1;
+
+                    /* If entire read is within the sieve buffer, read it from the buffer */
+                    if(addr>=sieve_start && contig_end<sieve_end) {
+                        unsigned char *base_sieve_buf=f->shared->sieve_buf+(_addr-sieve_start);
+                        unsigned char *temp_sieve_buf;
+                        haddr_t temp_addr=_addr-1;      /* Temporary address */
+
+#ifdef SLOW_WAY
+                        /* Retrieve all the sequences out of the current sieve buffer */
+                        while(contig_end<sieve_end) {
+                            /* Set the location within the sieve buffer to the correct offset */
+                            temp_sieve_buf=base_sieve_buf+offset_arr[u];
+
+                            /* Grab the data out of the buffer */
+                            HDmemcpy(buf,temp_sieve_buf,size_arr[u]);
+
+                            /* Increment offset in buffer */
+                            buf += size_arr[u];
+
+                            /* Increment sequence number, check for finished with sequences */
+                            if((++u) >= nseq)
+                                break;
+
+                            /* Re-compute end of sequence to retrieve */
+                            contig_end=temp_addr+offset_arr[u]+size_arr[u];
+                        } /* end while */
+#else /* SLOW_WAY */
+                        /* Find log2(n) where n is the number of elements to search */
+
+                        /* Set initial parameters */
+                        mask=(size_t)0xff<<((sizeof(size_t)-1)*8);  /* Get a mask for the leftmost byte */
+                        max_search=((nseq-1)-u)+1;          /* Compute 'n' for the log2 */
+                        assert(max_search>0);               /* Sanity check */
+                        bit_loc=(sizeof(size_t)*8)-1;       /* Initial bit location */
+
+                        /* Search for the first byte with a bit set */
+                        while((max_search & mask)==0) {
+                            mask>>=8;
+                            bit_loc-=8;
+                        } /* end while */
+
+                        /* Switch to searching for a bit */
+                        mask=1<<bit_loc;
+                        while((max_search & mask)==0) {
+                            mask>>=1;
+                            bit_loc--;
+                        } /* end while */
+
+                        /* location of the leftmost bit, plus 1, is log2(n) */
+                        max_seq=bit_loc+1;
+
+                        /* Don't walk off the array */
+                        max_seq=MIN(u+max_seq,nseq-1);
+
+                        /* Determine if a linear search is faster than a binary search */
+                        temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+                        if(temp_end>=sieve_end) {
+                            /* Linear search is faster */
+
+                            /* Set the initial search values */
+                            max_seq=u;
+                            temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+
+                            /* Search for the first sequence ending greater than the sieve buffer end */
+                            while(temp_end<sieve_end) {
+                                if(++max_seq>=nseq)
+                                    break;
+                                temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+                            } /* end while */
+
+                            /* Adjust back one element */
+                            max_seq--;
+
+                        } /* end if */
+                        else {
+                            size_t lo,hi;           /* Low and high bounds for binary search */
+                            uintn found=0;          /* Flag to indicate bounds have been found */
+
+                            /* Binary search is faster */
+
+                            /* Find the value 'u' which will be beyond the end of the sieve buffer */
+                            lo=u;
+                            hi=nseq-1;
+                            max_seq=(lo+hi)/2;
+                            while(!found) {
+                                /* Get the address of the end of sequence for the 'max_seq' position */
+                                temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+
+                                /* Current high bound is too large */
+                                if(temp_end>=sieve_end) {
+                                    if((lo+1)<hi) {
+                                        hi=max_seq;
+                                        max_seq=(lo+hi)/2;
+                                    } /* end if */
+                                    else {
+                                        found=1;
+                                    } /* end else */
+                                } /* end if */
+                                /* Current low bound is too small */
+                                else {
+                                    if((lo+1)<hi) {
+                                        lo=max_seq;
+                                        max_seq=(lo+hi+1)/2;
+                                    } /* end if */
+                                    else {
+                                        found=1;
+                                    } /* end else */
+                                } /* end else */
+                            } /* end while */
+
+                            /* Check for non-exact match */
+                            if(lo!=hi) {
+                                temp_end=temp_addr+offset_arr[hi]+size_arr[hi];
+                                if(temp_end<sieve_end)
+                                    max_seq=hi;
+                                else
+                                    max_seq=lo;
+                            } /* end if */
+                        } /* end else */
+
+                        /* Set the pointers to the correct locations in the offset & size arrays */
+                        size_arr_p=&size_arr[u];
+                        offset_arr_p=&offset_arr[u];
+
+#ifdef NO_DUFFS_DEVICE
+                        /* Retrieve all the sequences out of the current sieve buffer */
+                        while(u<=max_seq) {
+                            /* Set the location within the sieve buffer to the correct offset */
+                            temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                            /* Grab the data out of the buffer */
+                            HDmemcpy(buf,temp_sieve_buf,*size_arr_p);
+
+                            /* Increment offset in buffer */
+                            buf += *size_arr_p++;
+
+                            /* Increment the offset in the array */
+                            u++;
+                        } /* end while */
+#else /* NO_DUFFS_DEVICE */
+{
+    size_t seq_count;
+
+                    seq_count=(max_seq-u)+1;
+                    switch (seq_count % 4) {
+                        case 0:
+                            do
+                              {
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(buf,temp_sieve_buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                        case 3:
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(buf,temp_sieve_buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                        case 2:
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(buf,temp_sieve_buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                        case 1:
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(buf,temp_sieve_buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                          } while (u<=max_seq);
+                    } /* end switch */
+
+}
+#endif /* NO_DUFFS_DEVICE */
+#endif /* SLOW_WAY */
+                    } /* end if */
+                    /* Entire request is not within this data sieve buffer */
+                    else {
+                        /* Check if we can actually hold the I/O request in the sieve buffer */
+                        if(size>f->shared->sieve_buf_size) {
+                            /* Check for any overlap with the current sieve buffer */
+                            if((sieve_start>=addr && sieve_start<(contig_end+1))
+                                    || ((sieve_end-1)>=addr && (sieve_end-1)<(contig_end+1))) {
+                                /* Flush the sieve buffer, if it's dirty */
+                                if(f->shared->sieve_dirty) {
+                                    /* Write to file */
+                                    if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                        HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                          "block write failed");
+                                    }
+
+                                    /* Reset sieve buffer dirty flag */
+                                    f->shared->sieve_dirty=0;
+                                } /* end if */
+                            } /* end if */
+
+                            /* Read directly into the user's buffer */
+                            if (H5F_block_read(f, type, addr, size, dxpl_id, buf)<0) {
+                                HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                                          "block read failed");
+                            }
+                        } /* end if */
+                        /* Element size fits within the buffer size */
+                        else {
+                            /* Flush the sieve buffer if it's dirty */
+                            if(f->shared->sieve_dirty) {
+                                /* Write to file */
+                                if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                    HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                      "block write failed");
+                                }
+
+                                /* Reset sieve buffer dirty flag */
+                                f->shared->sieve_dirty=0;
+                            } /* end if */
+
+                            /* Determine the new sieve buffer size & location */
+                            f->shared->sieve_loc=addr;
+
+                            /* Make certain we don't read off the end of the file */
+                            if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
+                                HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
+                                    "unable to determine file size");
+                            }
+
+                            /* Adjust absolute EOA address to relative EOA address */
+                            rel_eoa=abs_eoa-f->shared->base_addr;
+
+                            /* Only need this when resizing sieve buffer */
+                            max_data=_max_data-offset_arr[u];
+
+                            /* Compute the size of the sieve buffer */
+                            /* Don't read off the end of the file, don't read past the end of the data element and don't read more than the buffer size */
+                            f->shared->sieve_size=MIN(rel_eoa-f->shared->sieve_loc,MIN(max_data,f->shared->sieve_buf_size));
+
+                            /* Update local copies of sieve information */
+                            sieve_start=f->shared->sieve_loc;
+                            sieve_size=f->shared->sieve_size;
+                            sieve_end=sieve_start+sieve_size;
+
+                            /* Read the new sieve buffer */
+                            if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                                          "block read failed");
                             }
 
                             /* Reset sieve buffer dirty flag */
                             f->shared->sieve_dirty=0;
-                        } /* end if */
-                    } /* end if */
 
-                    /* Read directly into the user's buffer */
+                            /* Grab the data out of the buffer (must be first piece of data in buffer ) */
+                            HDmemcpy(buf,f->shared->sieve_buf,size);
+                        } /* end else */
+
+                        /* Increment offset in buffer */
+                        buf += size_arr[u];
+
+                        /* Increment sequence number */
+                        u++;
+                    } /* end else */
+                } /* end for */
+            } /* end if */
+            /* No data sieve buffer yet, go allocate one */
+            else {
+                /* Set up the buffer parameters */
+                size=size_arr[u];
+                addr=_addr+offset_arr[u];
+                max_data=_max_data-offset_arr[u];
+
+                /* Check if we can actually hold the I/O request in the sieve buffer */
+                if(size>f->shared->sieve_buf_size) {
                     if (H5F_block_read(f, type, addr, size, dxpl_id, buf)<0) {
                         HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
                                   "block read failed");
                     }
                 } /* end if */
-                /* Element size fits within the buffer size */
                 else {
-                    /* Flush the sieve buffer if it's dirty */
-                    if(f->shared->sieve_dirty) {
-                        /* Write to file */
-                        if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                            HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                              "block write failed");
-                        }
-
-                        /* Reset sieve buffer dirty flag */
-                        f->shared->sieve_dirty=0;
-                    } /* end if */
+                    /* Allocate room for the data sieve buffer */
+                    if (NULL==(f->shared->sieve_buf=H5MM_malloc(f->shared->sieve_buf_size))) {
+                        HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                              "memory allocation failed");
+                    }
 
                     /* Determine the new sieve buffer size & location */
                     f->shared->sieve_loc=addr;
@@ -129,7 +494,7 @@ H5F_contig_read(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, hsize
                     rel_eoa=abs_eoa-f->shared->base_addr;
 
                     /* Compute the size of the sieve buffer */
-                    f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
+                    f->shared->sieve_size=MIN(rel_eoa-f->shared->sieve_loc,MIN(max_data,f->shared->sieve_buf_size));
 
                     /* Read the new sieve buffer */
                     if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
@@ -141,288 +506,521 @@ H5F_contig_read(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, hsize
                     f->shared->sieve_dirty=0;
 
                     /* Grab the data out of the buffer (must be first piece of data in buffer ) */
-                    assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                    HDmemcpy(buf,f->shared->sieve_buf,(size_t)size);
+                    HDmemcpy(buf,f->shared->sieve_buf,size);
                 } /* end else */
+
+                /* Increment offset in buffer */
+                buf += size_arr[u];
+
+                /* Increment sequence number */
+                u++;
             } /* end else */
-        } /* end if */
-        /* No data sieve buffer yet, go allocate one */
-        else {
-            /* Check if we can actually hold the I/O request in the sieve buffer */
-            if(size>f->shared->sieve_buf_size) {
-                if (H5F_block_read(f, type, addr, size, dxpl_id, buf)<0) {
-                    HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                              "block read failed");
-                }
-            } /* end if */
-            else {
-                /* Allocate room for the data sieve buffer */
-                assert(f->shared->sieve_buf_size==(hsize_t)((size_t)f->shared->sieve_buf_size)); /*check for overflow*/
-                if (NULL==(f->shared->sieve_buf=H5MM_malloc((size_t)f->shared->sieve_buf_size))) {
-                    HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
-                          "memory allocation failed");
-                }
-
-                /* Determine the new sieve buffer size & location */
-                f->shared->sieve_loc=addr;
-
-                /* Make certain we don't read off the end of the file */
-                if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
-                    HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
-                        "unable to determine file size");
-                }
-
-                /* Adjust absolute EOA address to relative EOA address */
-                rel_eoa=abs_eoa-f->shared->base_addr;
-
-                /* Compute the size of the sieve buffer */
-                f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
-
-                /* Read the new sieve buffer */
-                if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                    HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                              "block read failed");
-                }
-
-                /* Reset sieve buffer dirty flag */
-                f->shared->sieve_dirty=0;
-
-                /* Grab the data out of the buffer (must be first piece of data in buffer ) */
-                assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                HDmemcpy(buf,f->shared->sieve_buf,(size_t)size);
-            } /* end else */
-        } /* end else */
+        } /* end for */
     } /* end if */
     else {
-        if (H5F_block_read(f, type, addr, size, dxpl_id, buf)<0) {
-            HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                      "block read failed");
-        }
+        /* Work through all the sequences */
+        for(u=0; u<nseq; u++) {
+            size=size_arr[u];
+            addr=_addr+offset_arr[u];
+
+            if (H5F_block_read(f, type, addr, size, dxpl_id, buf)<0) {
+                HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                          "block read failed");
+            }
+
+            /* Increment offset in buffer */
+            buf += size_arr[u];
+        } /* end for */
     } /* end else */
 
     FUNC_LEAVE(SUCCEED);
-}   /* End H5F_contig_read() */
+}   /* end H5F_contig_readv() */
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5F_contig_write
+ * Function:	H5F_contig_writev
  *
- * Purpose:	Writes some data from a dataset into a buffer.
- *		The data is contiguous.	 The address is relative to the base
- *		address for the file.
+ * Purpose:	Writes some data vectors into a dataset from a buffer.
+ *		The data is contiguous.	 The address is the start of the dataset,
+ *              relative to the base address for the file and the offsets and
+ *              sequence lengths are in bytes.
  *
  * Return:	Non-negative on success/Negative on failure
  *
  * Programmer:	Quincey Koziol
- *              Thursday, September 28, 2000
+ *              Thursday, July 5, 2001
+ *
+ * Notes:
+ *      Offsets in the sequences must be monotonically increasing
  *
  * Modifications:
  *
  *-------------------------------------------------------------------------
  */
 herr_t
-H5F_contig_write(H5F_t *f, hsize_t max_data, H5FD_mem_t type, haddr_t addr, hsize_t size,
-        hid_t dxpl_id, const void *buf)
+H5F_contig_writev(H5F_t *f, hsize_t _max_data, H5FD_mem_t type, haddr_t _addr,
+    size_t nseq, size_t size_arr[], hsize_t offset_arr[], hid_t dxpl_id,
+    const void *_buf)
 {
-    haddr_t abs_eoa;		        /* Absolute end of file address		*/
-    haddr_t rel_eoa;		        /* Relative end of file address		*/
-
-    FUNC_ENTER(H5F_contig_write, FAIL);
+    const unsigned char *buf=_buf;      /* Pointer to buffer to fill */
+    haddr_t abs_eoa;	        /* Absolute end of file address		*/
+    haddr_t rel_eoa;	        /* Relative end of file address		*/
+    haddr_t addr;               /* Actual address to read */
+    hsize_t max_data;           /* Actual maximum size of data to cache */
+    size_t size;                /* Size of sequence in bytes */
+    size_t u;                   /* Counting variable */
+#ifndef SLOW_WAY
+    size_t max_seq;        /* Maximum sequence to copy */
+    haddr_t temp_end;      /* Temporary end of buffer variable */
+    size_t max_search;     /* Maximum number of sequences to search */
+    size_t mask;           /* Bit mask */
+    intn bit_loc;          /* Bit location of the leftmost '1' in max_search */
+    size_t *size_arr_p;    /* Pointer into the size array */
+    hsize_t *offset_arr_p; /* Pointer into the offset array */
+#endif /* SLOW_WAY */
+   
+    FUNC_ENTER(H5F_contig_writev, FAIL);
 
-    assert (f);
-    assert (size<SIZET_MAX);
-    assert (buf);
+    /* Check args */
+    assert(f);
+    assert(buf);
 
     /* Check if data sieving is enabled */
     if(f->shared->lf->feature_flags&H5FD_FEAT_DATA_SIEVE) {
-        /* Try writing to the data sieve buffer */
-        if(f->shared->sieve_buf) {
-            haddr_t sieve_start, sieve_end;     /* Start & end locations of sieve buffer */
-            haddr_t contig_end;         /* End locations of block to write */
-            hsize_t sieve_size;         /* size of sieve buffer */
-
-            /* Stash local copies of these value */
-            sieve_start=f->shared->sieve_loc;
-            sieve_size=f->shared->sieve_size;
-            sieve_end=sieve_start+sieve_size;
-            contig_end=addr+size-1;
-            
-            /* If entire write is within the sieve buffer, write it to the buffer */
-            if(addr>=sieve_start && contig_end<sieve_end) {
-                /* Grab the data out of the buffer */
-                assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                HDmemcpy(f->shared->sieve_buf+(addr-sieve_start),buf,(size_t)size);
-
-                /* Set sieve buffer dirty flag */
-                f->shared->sieve_dirty=1;
 
-            } /* end if */
-            /* Entire request is not within this data sieve buffer */
-            else {
-                /* Check if we can actually hold the I/O request in the sieve buffer */
-                if(size>f->shared->sieve_buf_size) {
-                    /* Check for any overlap with the current sieve buffer */
-                    if((sieve_start>=addr && sieve_start<(contig_end+1))
-                            || ((sieve_end-1)>=addr && (sieve_end-1)<(contig_end+1))) {
-                        /* Flush the sieve buffer, if it's dirty */
-                        if(f->shared->sieve_dirty) {
-                            /* Write to file */
-                            if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                                HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                                  "block write failed");
-                            }
+        /* Outer loop, guarantees working through all the sequences */
+        for(u=0; u<nseq; ) {
 
-                            /* Reset sieve buffer dirty flag */
-                            f->shared->sieve_dirty=0;
-                        } /* end if */
+            /* Try writing into the data sieve buffer */
+            if(f->shared->sieve_buf) {
+                haddr_t sieve_start, sieve_end;     /* Start & end locations of sieve buffer */
+                haddr_t contig_end;             /* End locations of block to write */
+                size_t sieve_size;              /* size of sieve buffer */
 
-                        /* Force the sieve buffer to be re-read the next time */
-                        f->shared->sieve_loc=HADDR_UNDEF;
-                        f->shared->sieve_size=0;
-                    } /* end if */
+                /* Stash local copies of these value */
+                sieve_start=f->shared->sieve_loc;
+                sieve_size=f->shared->sieve_size;
+                sieve_end=sieve_start+sieve_size;
+                
+                /* Next-outer loop works through sequences as fast as possible */
+                for(; u<nseq; ) {
+                    size=size_arr[u];
+                    addr=_addr+offset_arr[u];
+
+                    /* Compute end of sequence to retrieve */
+                    contig_end=addr+size-1;
+
+                    /* If entire write is within the sieve buffer, write it to the buffer */
+                    if(addr>=sieve_start && contig_end<sieve_end) {
+                        unsigned char *base_sieve_buf=f->shared->sieve_buf+(_addr-sieve_start);
+                        unsigned char *temp_sieve_buf;
+                        haddr_t temp_addr=_addr-1;      /* Temporary address */
+
+#ifdef SLOW_WAY
+                        /* Retrieve all the sequences out of the current sieve buffer */
+                        while(contig_end<sieve_end) {
+                            /* Set the location within the sieve buffer to the correct offset */
+                            temp_sieve_buf=base_sieve_buf+offset_arr[u];
+
+                            /* Grab the data out of the buffer */
+                            HDmemcpy(temp_sieve_buf,buf,size_arr[u]);
+
+                            /* Increment offset in buffer */
+                            buf += size_arr[u];
+
+                            /* Increment sequence number, check for finished with sequences */
+                            if((++u) >= nseq)
+                                break;
+
+                            /* Re-compute end of sequence to retrieve */
+                            contig_end=temp_addr+offset_arr[u]+size_arr[u];
+                        } /* end while */
+#else /* SLOW_WAY */
+                        /* Find log2(n) where n is the number of elements to search */
+
+                        /* Set initial parameters */
+                        mask=(size_t)0xff<<((sizeof(size_t)-1)*8);  /* Get a mask for the leftmost byte */
+                        max_search=((nseq-1)-u)+1;          /* Compute 'n' for the log2 */
+                        assert(max_search>0);               /* Sanity check */
+                        bit_loc=(sizeof(size_t)*8)-1;       /* Initial bit location */
+
+                        /* Search for the first byte with a bit set */
+                        while((max_search & mask)==0) {
+                            mask>>=8;
+                            bit_loc-=8;
+                        } /* end while */
+
+                        /* Switch to searching for a bit */
+                        mask=1<<bit_loc;
+                        while((max_search & mask)==0) {
+                            mask>>=1;
+                            bit_loc--;
+                        } /* end while */
+
+                        /* location of the leftmost bit, plus 1, is log2(n) */
+                        max_seq=bit_loc+1;
+
+                        /* Don't walk off the array */
+                        max_seq=MIN(u+max_seq,nseq-1);
+
+                        /* Determine if a linear search is faster than a binary search */
+                        temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+                        if(temp_end>=sieve_end) {
+                            /* Linear search is faster */
+
+                            /* Set the initial search values */
+                            max_seq=u;
+                            temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+
+                            /* Search for the first sequence ending greater than the sieve buffer end */
+                            while(temp_end<sieve_end) {
+                                if(++max_seq>=nseq)
+                                    break;
+                                temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+                            } /* end while */
+
+                            /* Adjust back one element */
+                            max_seq--;
 
-                    /* Write directly to the user's buffer */
-                    if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
-                        HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                                  "block write failed");
-                    } /* end if */
-                } /* end if */
-                /* Element size fits within the buffer size */
-                else {
-                    /* Check if it is possible to (exactly) prepend or append to existing (dirty) sieve buffer */
-                    if(((addr+size)==sieve_start || addr==sieve_end) &&
-                            (size+sieve_size)<=f->shared->sieve_buf_size &&
-                            f->shared->sieve_dirty) {
-                        /* Prepend to existing sieve buffer */
-                        if((addr+size)==sieve_start) {
-                            /* Move existing sieve information to correct location */
-                            assert(sieve_size==(hsize_t)((size_t)sieve_size)); /*check for overflow*/
-                            HDmemmove(f->shared->sieve_buf+size,f->shared->sieve_buf,(size_t)sieve_size);
-
-                            /* Copy in new information (must be first in sieve buffer) */
-                            assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                            HDmemcpy(f->shared->sieve_buf,buf,(size_t)size);
-
-                            /* Adjust sieve location */
-                            f->shared->sieve_loc=addr;
-                            
                         } /* end if */
-                        /* Append to existing sieve buffer */
                         else {
-                            /* Copy in new information */
-                            assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                            HDmemcpy(f->shared->sieve_buf+sieve_size,buf,(size_t)size);
+                            size_t lo,hi;           /* Low and high bounds for binary search */
+                            uintn found=0;          /* Flag to indicate bounds have been found */
+
+                            /* Binary search is faster */
+
+                            /* Find the value 'u' which will be beyond the end of the sieve buffer */
+                            lo=u;
+                            hi=nseq-1;
+                            max_seq=(lo+hi)/2;
+                            while(!found) {
+                                /* Get the address of the end of sequence for the 'max_seq' position */
+                                temp_end=temp_addr+offset_arr[max_seq]+size_arr[max_seq];
+
+                                /* Current high bound is too large */
+                                if(temp_end>=sieve_end) {
+                                    if((lo+1)<hi) {
+                                        hi=max_seq;
+                                        max_seq=(lo+hi)/2;
+                                    } /* end if */
+                                    else {
+                                        found=1;
+                                    } /* end else */
+                                } /* end if */
+                                /* Current low bound is too small */
+                                else {
+                                    if((lo+1)<hi) {
+                                        lo=max_seq;
+                                        max_seq=(lo+hi+1)/2;
+                                    } /* end if */
+                                    else {
+                                        found=1;
+                                    } /* end else */
+                                } /* end else */
+                            } /* end while */
+
+                            /* Check for non-exact match */
+                            if(lo!=hi) {
+                                temp_end=temp_addr+offset_arr[hi]+size_arr[hi];
+                                if(temp_end<sieve_end)
+                                    max_seq=hi;
+                                else
+                                    max_seq=lo;
+                            } /* end if */
                         } /* end else */
 
-                        /* Adjust sieve size */
-                        f->shared->sieve_size += size;
-                        
+                        /* Set the pointers to the correct locations in the offset & size arrays */
+                        size_arr_p=&size_arr[u];
+                        offset_arr_p=&offset_arr[u];
+
+#ifdef NO_DUFFS_DEVICE
+                        /* Retrieve all the sequences out of the current sieve buffer */
+                        while(u<=max_seq) {
+                            /* Set the location within the sieve buffer to the correct offset */
+                            temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                            /* Grab the data out of the buffer */
+                            HDmemcpy(temp_sieve_buf,buf,*size_arr_p);
+
+                            /* Increment offset in buffer */
+                            buf += *size_arr_p++;
+
+                            /* Increment the offset in the array */
+                            u++;
+                        } /* end while */
+#else /* NO_DUFFS_DEVICE */
+{
+    size_t seq_count;
+
+                    seq_count=(max_seq-u)+1;
+                    switch (seq_count % 4) {
+                        case 0:
+                            do
+                              {
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(temp_sieve_buf,buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                        case 3:
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(temp_sieve_buf,buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                        case 2:
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(temp_sieve_buf,buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                        case 1:
+                                /* Set the location within the sieve buffer to the correct offset */
+                                temp_sieve_buf=base_sieve_buf+*offset_arr_p++;
+
+                                /* Grab the data out of the buffer */
+                                HDmemcpy(temp_sieve_buf,buf,*size_arr_p);
+
+                                /* Increment offset in buffer */
+                                buf += *size_arr_p++;
+
+                                /* Increment the offset in the array */
+                                u++;
+
+                          } while (u<=max_seq);
+                    } /* end switch */
+
+}
+#endif /* NO_DUFFS_DEVICE */
+#endif /* SLOW_WAY */
+                        /* Set sieve buffer dirty flag */
+                        f->shared->sieve_dirty=1;
+
                     } /* end if */
-                    /* Can't add the new data onto the existing sieve buffer */
+                    /* Entire request is not within this data sieve buffer */
                     else {
-                        /* Flush the sieve buffer if it's dirty */
-                        if(f->shared->sieve_dirty) {
-                            /* Write to file */
-                            if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                                HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                                  "block write failed");
-                            } /* end if */
+                        /* Check if we can actually hold the I/O request in the sieve buffer */
+                        if(size>f->shared->sieve_buf_size) {
+                            /* Check for any overlap with the current sieve buffer */
+                            if((sieve_start>=addr && sieve_start<(contig_end+1))
+                                    || ((sieve_end-1)>=addr && (sieve_end-1)<(contig_end+1))) {
+                                /* Flush the sieve buffer, if it's dirty */
+                                if(f->shared->sieve_dirty) {
+                                    /* Write to file */
+                                    if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                        HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                          "block write failed");
+                                    }
 
-                            /* Reset sieve buffer dirty flag */
-                            f->shared->sieve_dirty=0;
-                        } /* end if */
+                                    /* Reset sieve buffer dirty flag */
+                                    f->shared->sieve_dirty=0;
+                                } /* end if */
 
-                        /* Determine the new sieve buffer size & location */
-                        f->shared->sieve_loc=addr;
+                                /* Force the sieve buffer to be re-read the next time */
+                                f->shared->sieve_loc=HADDR_UNDEF;
+                                f->shared->sieve_size=0;
+                            } /* end if */
 
-                        /* Make certain we don't read off the end of the file */
-                        if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
-                            HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
-                                "unable to determine file size");
+                            /* Write directly from the user's buffer */
+                            if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
+                                HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                          "block write failed");
+                            }
                         } /* end if */
+                        /* Element size fits within the buffer size */
+                        else {
+                            /* Check if it is possible to (exactly) prepend or append to existing (dirty) sieve buffer */
+                            if(((addr+size)==sieve_start || addr==sieve_end) &&
+                                    (size+sieve_size)<=f->shared->sieve_buf_size &&
+                                    f->shared->sieve_dirty) {
+                                /* Prepend to existing sieve buffer */
+                                if((addr+size)==sieve_start) {
+                                    /* Move existing sieve information to correct location */
+                                    HDmemmove(f->shared->sieve_buf+size,f->shared->sieve_buf,sieve_size);
 
-                        /* Adjust absolute EOA address to relative EOA address */
-                        rel_eoa=abs_eoa-f->shared->base_addr;
+                                    /* Copy in new information (must be first in sieve buffer) */
+                                    HDmemcpy(f->shared->sieve_buf,buf,size);
 
-                        /* Compute the size of the sieve buffer */
-                        f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
+                                    /* Adjust sieve location */
+                                    f->shared->sieve_loc=addr;
+                                    
+                                } /* end if */
+                                /* Append to existing sieve buffer */
+                                else {
+                                    /* Copy in new information */
+                                    HDmemcpy(f->shared->sieve_buf+sieve_size,buf,size);
+                                } /* end else */
+
+                                /* Adjust sieve size */
+                                f->shared->sieve_size += size;
+                                
+                                /* Update local copies of sieve information */
+                                sieve_start=f->shared->sieve_loc;
+                                sieve_size=f->shared->sieve_size;
+                                sieve_end=sieve_start+sieve_size;
 
-                        /* Check if there is any point in reading the data from the file */
-                        if(f->shared->sieve_size>size) {
-                            /* Read the new sieve buffer */
-                            if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                                HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                                          "block read failed");
                             } /* end if */
-                        } /* end if */
+                            /* Can't add the new data onto the existing sieve buffer */
+                            else {
+                                /* Flush the sieve buffer if it's dirty */
+                                if(f->shared->sieve_dirty) {
+                                    /* Write to file */
+                                    if (H5F_block_write(f, H5FD_MEM_DRAW, sieve_start, sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                        HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                          "block write failed");
+                                    }
 
-                        /* Grab the data out of the buffer (must be first piece of data in buffer) */
-                        assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                        HDmemcpy(f->shared->sieve_buf,buf,(size_t)size);
+                                    /* Reset sieve buffer dirty flag */
+                                    f->shared->sieve_dirty=0;
+                                } /* end if */
 
-                        /* Set sieve buffer dirty flag */
-                        f->shared->sieve_dirty=1;
+                                /* Determine the new sieve buffer size & location */
+                                f->shared->sieve_loc=addr;
 
+                                /* Make certain we don't read off the end of the file */
+                                if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
+                                    HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
+                                        "unable to determine file size");
+                                }
+
+                                /* Adjust absolute EOA address to relative EOA address */
+                                rel_eoa=abs_eoa-f->shared->base_addr;
+
+                                /* Only need this when resizing sieve buffer */
+                                max_data=_max_data-offset_arr[u];
+
+                                /* Compute the size of the sieve buffer */
+                                /* Don't read off the end of the file, don't read past the end of the data element and don't read more than the buffer size */
+                                f->shared->sieve_size=MIN(rel_eoa-f->shared->sieve_loc,MIN(max_data,f->shared->sieve_buf_size));
+
+                                /* Update local copies of sieve information */
+                                sieve_start=f->shared->sieve_loc;
+                                sieve_size=f->shared->sieve_size;
+                                sieve_end=sieve_start+sieve_size;
+
+                                /* Check if there is any point in reading the data from the file */
+                                if(f->shared->sieve_size>size) {
+                                    /* Read the new sieve buffer */
+                                    if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                                        HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                                                  "block read failed");
+                                    } /* end if */
+                                } /* end if */
+
+                                /* Grab the data out of the buffer (must be first piece of data in buffer ) */
+                                HDmemcpy(f->shared->sieve_buf,buf,size);
+
+                                /* Set sieve buffer dirty flag */
+                                f->shared->sieve_dirty=1;
+
+                            } /* end else */
+                        } /* end else */
+
+                        /* Increment offset in buffer */
+                        buf += size_arr[u];
+
+                        /* Increment sequence number */
+                        u++;
                     } /* end else */
-                } /* end else */
-            } /* end else */
-        } /* end if */
-        /* No data sieve buffer yet, go allocate one */
-        else {
-            /* Check if we can actually hold the I/O request in the sieve buffer */
-            if(size>f->shared->sieve_buf_size) {
-                if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
-                    HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                              "block write failed");
-                }
+                } /* end for */
             } /* end if */
+            /* No data sieve buffer yet, go allocate one */
             else {
-                /* Allocate room for the data sieve buffer */
-                assert(f->shared->sieve_buf_size==(hsize_t)((size_t)f->shared->sieve_buf_size)); /*check for overflow*/
-                if (NULL==(f->shared->sieve_buf=H5MM_malloc((size_t)f->shared->sieve_buf_size))) {
-                    HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
-                          "memory allocation failed");
+                /* Set up the buffer parameters */
+                size=size_arr[u];
+                addr=_addr+offset_arr[u];
+                max_data=_max_data-offset_arr[u];
+
+                /* Check if we can actually hold the I/O request in the sieve buffer */
+                if(size>f->shared->sieve_buf_size) {
+                    if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
+                        HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                                  "block write failed");
+                    }
                 } /* end if */
+                else {
+                    /* Allocate room for the data sieve buffer */
+                    if (NULL==(f->shared->sieve_buf=H5MM_malloc(f->shared->sieve_buf_size))) {
+                        HRETURN_ERROR(H5E_RESOURCE, H5E_NOSPACE, FAIL,
+                              "memory allocation failed");
+                    }
 
-                /* Determine the new sieve buffer size & location */
-                f->shared->sieve_loc=addr;
+                    /* Determine the new sieve buffer size & location */
+                    f->shared->sieve_loc=addr;
 
-                /* Make certain we don't read off the end of the file */
-                if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
-                    HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
-                        "unable to determine file size");
-                } /* end if */
+                    /* Make certain we don't read off the end of the file */
+                    if (HADDR_UNDEF==(abs_eoa=H5FD_get_eoa(f->shared->lf))) {
+                        HRETURN_ERROR(H5E_FILE, H5E_CANTOPENFILE, FAIL,
+                            "unable to determine file size");
+                    }
 
-                /* Adjust absolute EOA address to relative EOA address */
-                rel_eoa=abs_eoa-f->shared->base_addr;
+                    /* Adjust absolute EOA address to relative EOA address */
+                    rel_eoa=abs_eoa-f->shared->base_addr;
 
-                /* Compute the size of the sieve buffer */
-                f->shared->sieve_size=MIN(rel_eoa-addr,MIN(max_data,f->shared->sieve_buf_size));
+                    /* Compute the size of the sieve buffer */
+                    f->shared->sieve_size=MIN(rel_eoa-f->shared->sieve_loc,MIN(max_data,f->shared->sieve_buf_size));
 
-                /* Check if there is any point in reading the data from the file */
-                if(f->shared->sieve_size>size) {
-                    /* Read the new sieve buffer */
-                    if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
-                        HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
-                                  "block read failed");
+                    /* Check if there is any point in reading the data from the file */
+                    if(f->shared->sieve_size>size) {
+                        /* Read the new sieve buffer */
+                        if (H5F_block_read(f, type, f->shared->sieve_loc, f->shared->sieve_size, dxpl_id, f->shared->sieve_buf)<0) {
+                            HRETURN_ERROR(H5E_IO, H5E_READERROR, FAIL,
+                                      "block read failed");
+                        } /* end if */
                     } /* end if */
-                } /* end if */
 
-                /* Grab the data out of the buffer (must be first piece of data in buffer) */
-                assert(size==(hsize_t)((size_t)size)); /*check for overflow*/
-                HDmemcpy(f->shared->sieve_buf,buf,(size_t)size);
+                    /* Grab the data out of the buffer (must be first piece of data in buffer ) */
+                    HDmemcpy(f->shared->sieve_buf,buf,size);
+
+                    /* Set sieve buffer dirty flag */
+                    f->shared->sieve_dirty=1;
+                } /* end else */
 
-                /* Set sieve buffer dirty flag */
-                f->shared->sieve_dirty=1;
+                /* Increment offset in buffer */
+                buf += size_arr[u];
+
+                /* Increment sequence number */
+                u++;
             } /* end else */
-        } /* end else */
+        } /* end for */
     } /* end if */
     else {
-        if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
-            HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
-                      "block write failed");
-        } /* end if */
+        /* Work through all the sequences */
+        for(u=0; u<nseq; u++) {
+            size=size_arr[u];
+            addr=_addr+offset_arr[u];
+
+            if (H5F_block_write(f, type, addr, size, dxpl_id, buf)<0) {
+                HRETURN_ERROR(H5E_IO, H5E_WRITEERROR, FAIL,
+                          "block write failed");
+            }
+
+            /* Increment offset in buffer */
+            buf += size_arr[u];
+        } /* end for */
     } /* end else */
 
     FUNC_LEAVE(SUCCEED);
-}   /* End H5F_contig_write() */
+}   /* end H5F_contig_writev() */
+