[svn-r23769] add property to indicate append

add a new version of checksum algorithm to correctly save the state
other updates...

11 files changed, 351 insertions, 14 deletions

diff --git a/src/H5Pdxpl.c b/src/H5Pdxpl.c
index e5578f9..146ae96 100644
--- a/src/H5Pdxpl.c
+++ b/src/H5Pdxpl.c
@@ -48,6 +48,7 @@
 /****************/
 
 #ifdef H5_HAVE_EFF
+
 #define H5D_XFER_INJECT_BAD_CHECKSUM_SIZE		sizeof(hbool_t)
 #define H5D_XFER_INJECT_BAD_CHECKSUM_DEF    		FALSE
 #define H5D_XFER_INJECT_BAD_CHECKSUM_ENC                H5P__encode_hbool_t
@@ -57,6 +58,12 @@
 #define H5D_XFER_CHECKSUM_DEF  		0
 #define H5D_XFER_CHECKSUM_ENC           H5P__encode_unsigned
 #define H5D_XFER_CHECKSUM_DEC           H5P__decode_unsigned
+
+#define H5D_XFER_APPEND_ONLY_SIZE		sizeof(hbool_t)
+#define H5D_XFER_APPEND_ONLY_DEF    		FALSE
+#define H5D_XFER_APPEND_ONLY_ENC                H5P__encode_hbool_t
+#define H5D_XFER_APPEND_ONLY_DEC                H5P__decode_hbool_t
+
 #endif /* H5_HAVE_EFF */
 
 /* ======== Data transfer properties ======== */
@@ -252,6 +259,7 @@ const H5P_libclass_t H5P_CLS_DXFR[1] = {{
 #ifdef H5_HAVE_EFF
 static const hbool_t H5D_def_inject_bad_checksum_g = H5D_XFER_INJECT_BAD_CHECKSUM_DEF;
 static const uint32_t H5D_def_checksum_g = H5D_XFER_CHECKSUM_DEF;
+static const hbool_t H5D_def_append_only_g = H5D_XFER_APPEND_ONLY_DEF;
 #endif /* H5_HAVE_EFF */
 
 /* Property value defaults */
@@ -307,6 +315,7 @@ H5P__dxfr_reg_prop(H5P_genclass_t *pclass)
     FUNC_ENTER_STATIC
 
 #ifdef H5_HAVE_EFF
+
     if(H5P_register_real(pclass, H5D_XFER_INJECT_BAD_CHECKSUM_NAME, H5D_XFER_INJECT_BAD_CHECKSUM_SIZE, 
                          &H5D_def_inject_bad_checksum_g,
                          NULL, NULL, NULL, H5D_XFER_INJECT_BAD_CHECKSUM_ENC, H5D_XFER_INJECT_BAD_CHECKSUM_DEC, 
@@ -318,6 +327,13 @@ H5P__dxfr_reg_prop(H5P_genclass_t *pclass)
                          NULL, NULL, NULL, H5D_XFER_CHECKSUM_ENC, H5D_XFER_CHECKSUM_DEC, 
                          NULL, NULL, NULL, NULL) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
+    if(H5P_register_real(pclass, H5D_XFER_APPEND_ONLY_NAME, H5D_XFER_APPEND_ONLY_SIZE, 
+                         &H5D_def_append_only_g,
+                         NULL, NULL, NULL, H5D_XFER_APPEND_ONLY_ENC, H5D_XFER_APPEND_ONLY_DEC, 
+                         NULL, NULL, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
 #endif /* H5_HAVE_EFF */
 
     /* Register the max. temp buffer size property */
diff --git a/src/H5Sprivate.h b/src/H5Sprivate.h
index 63b31bc..34fc07f 100644
--- a/src/H5Sprivate.h
+++ b/src/H5Sprivate.h
@@ -272,6 +272,8 @@ H5_DLL H5S_t *H5S_decode(const unsigned char *buf);
 
 H5_DLL herr_t H5S_get_offsets(const H5S_t *space, size_t elmt_size, size_t nelmts, 
                               hsize_t **_off, size_t **_len, size_t *_num_entries);
+H5_DLL uint32_t H5S_checksum(const void *buf, size_t elmt_size, size_t nelmts, 
+                             const H5S_t *space);
 
 #ifdef H5_HAVE_PARALLEL
 /* Global vars whose value comes from environment variable */
diff --git a/src/H5Sselect.c b/src/H5Sselect.c
index 23f87b1..1d6c63d 100644
--- a/src/H5Sselect.c
+++ b/src/H5Sselect.c
@@ -2143,3 +2143,78 @@ done:
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5S_get_offsets() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5S_checksum
+ *
+ * Purpose:	Computes a checksum for a buffer with a dataspace 
+ *              selection using the HDF5 fletcher checksume routines.
+ *
+ * Return:	Returns a 32-bit value.  Every bit of the key affects every bit of
+ *              the return value.  Two keys differing by one or two bits will have
+ *              totally different hash values.
+ *
+ * Programmer:	Mohamad Chaarawi
+ *              June 2013
+ *
+ *-------------------------------------------------------------------------
+ */
+uint32_t
+H5S_checksum(const void *buf, size_t elmt_size, size_t nelmts, const H5S_t *space)
+{
+    hsize_t _off[H5D_IO_VECTOR_SIZE];      /* Array to store sequence offsets in memory */
+    hsize_t *off = NULL;    /* Pointer to sequence offsets in memory */
+    size_t _len[H5D_IO_VECTOR_SIZE];       /* Array to store sequence lengths in memory */
+    size_t *len = NULL;     /* Pointer to sequence lengths in memory */
+    H5S_sel_iter_t iter;    /* Memory selection iteration info */
+    hbool_t iter_init = 0;  /* Memory selection iteration info has been initialized */
+    size_t nseq;            /* Number of sequences generated */
+    uint32_t ret_value = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT
+
+    len = _len;
+    off = _off;
+
+    /* Check for only one element in selection */
+    if(nelmts == 1) {
+        size_t buf_size = elmt_size * nelmts;
+
+        if(H5S_SELECT_OFFSET(space, off) < 0)
+            HGOTO_ERROR(H5E_INTERNAL, H5E_UNSUPPORTED, 0, "can't retrieve memory selection offset");
+
+        ret_value = H5_checksum_lookup3(buf, buf_size, ret_value);
+    } /* end if */
+    else {
+        size_t nelem;           /* Number of elements used in sequences */
+        size_t i;
+
+        /* Initialize iterator */
+        if(H5S_select_iter_init(&iter, space, elmt_size) < 0)
+            HGOTO_ERROR(H5E_DATASPACE, H5E_CANTINIT, 0, "unable to initialize selection iterator")
+        iter_init = 1;
+
+        nseq = 0;
+
+        /* Loop, until all bytes are processed */
+        while(nelmts > 0) {
+            /* Get sequences for selection */
+            if(H5S_SELECT_GET_SEQ_LIST(space, 0, &iter, H5D_IO_VECTOR_SIZE, nelmts, &nseq, 
+                                       &nelem, off, len) < 0)
+                HGOTO_ERROR(H5E_INTERNAL, H5E_UNSUPPORTED, 0, "sequence length generation failed");
+
+            for(i=0 ; i<nseq ; i++) {
+                ret_value = H5_checksum_lookup3(&((char *)buf)[0]+off[i], len[i], ret_value);
+            }
+            nelmts -= nelem;
+        } /* end while */
+    } /* end else */
+
+done:
+    /* Release memory selection iterator */
+    if(iter_init)
+        if(H5S_SELECT_ITER_RELEASE(&iter) < 0)
+            HDONE_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, 0, "unable to release selection iterator")
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5S_checksum */
diff --git a/src/H5VLiod.c b/src/H5VLiod.c
index a8562e9..d479676 100644
--- a/src/H5VLiod.c
+++ b/src/H5VLiod.c
@@ -683,6 +683,48 @@ done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Pget_dxpl_inject_bad_checksum() */
 
+herr_t
+H5Pset_dxpl_append_only(hid_t dxpl_id, hbool_t flag)
+{
+    H5P_genplist_t *plist;      /* Property list pointer */
+    herr_t ret_value = SUCCEED; /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+
+    if(dxpl_id == H5P_DEFAULT)
+        HGOTO_ERROR(H5E_PLIST, H5E_BADVALUE, FAIL, "can't set values in default property list")
+
+    /* Check arguments */
+    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
+        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")
+
+    /* Set the transfer mode */
+    if(H5P_set(plist, H5D_XFER_APPEND_ONLY_NAME, &flag) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to set value")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pset_dxpl_append_only() */
+
+herr_t
+H5Pget_dxpl_append_only(hid_t dxpl_id, hbool_t *flag/*out*/)
+{
+    H5P_genplist_t *plist;              /* Property list pointer */
+    herr_t      ret_value = SUCCEED;    /* Return value */
+
+    FUNC_ENTER_API(FAIL)
+
+    if(NULL == (plist = H5P_object_verify(dxpl_id, H5P_DATASET_XFER)))
+        HGOTO_ERROR(H5E_PLIST, H5E_BADTYPE, FAIL, "not a dxpl")
+
+    /* Get the transfer mode */
+    if(flag)
+        if(H5P_get(plist, H5D_XFER_APPEND_ONLY_NAME, flag) < 0)
+            HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "unable to get value")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pget_dxpl_append_only() */
 
 
 /*-------------------------------------------------------------------------
@@ -2304,12 +2346,15 @@ H5VL_iod_dataset_read(void *_dset, hid_t mem_type_id, hid_t mem_space_id,
 
     /* setup info struct for I/O request. 
        This is to manage the I/O operation once the wait is called. */
-    if(NULL == (info = (H5VL_iod_io_info_t *)H5MM_malloc(sizeof(H5VL_iod_io_info_t))))
+    if(NULL == (info = (H5VL_iod_io_info_t *)H5MM_calloc(sizeof(H5VL_iod_io_info_t))))
 	HGOTO_ERROR(H5E_DATASET, H5E_NOSPACE, FAIL, "can't allocate a request");
     info->status = status;
     info->bulk_handle = bulk_handle;
     info->buf_ptr = buf;
-    info->buf_size = buf_size;
+    info->nelmts = nelmts;
+    info->type_size = type_size;
+    if(NULL == (info->space = H5S_copy(mem_space, FALSE, TRUE)))
+        HGOTO_ERROR(H5E_DATASPACE, H5E_CANTINIT, FAIL, "unable to copy dataspace")
 
     /* Get async request for operation */
     if(do_async) {
@@ -2451,7 +2496,7 @@ H5VL_iod_dataset_write(void *_dset, hid_t mem_type_id, hid_t mem_space_id,
     buf_size = nelmts * type_size;
 
     /* calculate a checksum for the data */
-    internal_cs = H5_checksum_fletcher32(buf, buf_size);
+    internal_cs = H5S_checksum(buf, type_size, nelmts, mem_space);
 
     /* Verify the checksum value if the dxpl contains a user defined checksum */
     if(H5P_DATASET_XFER_DEFAULT != dxpl_id) {
@@ -2552,7 +2597,7 @@ H5VL_iod_dataset_write(void *_dset, hid_t mem_type_id, hid_t mem_space_id,
 
     /* setup info struct for I/O request 
        This is to manage the I/O operation once the wait is called. */
-    if(NULL == (info = (H5VL_iod_io_info_t *)H5MM_malloc(sizeof(H5VL_iod_io_info_t))))
+    if(NULL == (info = (H5VL_iod_io_info_t *)H5MM_calloc(sizeof(H5VL_iod_io_info_t))))
 	HGOTO_ERROR(H5E_DATASET, H5E_NOSPACE, FAIL, "can't allocate a request");
     info->status = status;
     info->bulk_handle = bulk_handle;
diff --git a/src/H5VLiod.h b/src/H5VLiod.h
index 773f51b..a813f59 100644
--- a/src/H5VLiod.h
+++ b/src/H5VLiod.h
@@ -51,6 +51,7 @@ extern "C" {
 
 #define H5D_XFER_INJECT_BAD_CHECKSUM_NAME "inject_bad_checksum"
 #define H5D_XFER_CHECKSUM_NAME "checksum"
+#define H5D_XFER_APPEND_ONLY_NAME "append_only"
 
 H5_DLL H5VL_class_t *H5VL_iod_init(void);
 H5_DLL herr_t H5Pset_fapl_iod(hid_t fapl_id, MPI_Comm comm, MPI_Info info);
@@ -61,6 +62,8 @@ H5_DLL herr_t H5Pset_dxpl_checksum(hid_t dxpl_id, uint32_t flag);
 H5_DLL herr_t H5Pget_dxpl_checksum(hid_t dxpl_id, uint32_t *flag);
 H5_DLL herr_t H5Pset_dxpl_inject_bad_checksum(hid_t dxpl_id, hbool_t flag);
 H5_DLL herr_t H5Pget_dxpl_inject_bad_checksum(hid_t dxpl_id, hbool_t *flag);
+H5_DLL herr_t H5Pset_dxpl_append_only(hid_t dxpl_id, hbool_t flag);
+H5_DLL herr_t H5Pget_dxpl_append_only(hid_t dxpl_id, hbool_t *flag);
 #endif /* H5_HAVE_EFF */
 
 #ifdef __cplusplus
diff --git a/src/H5VLiod_client.c b/src/H5VLiod_client.c
index 022f5ab..a34521c 100644
--- a/src/H5VLiod_client.c
+++ b/src/H5VLiod_client.c
@@ -26,6 +26,7 @@
 #include "H5Iprivate.h"		/* IDs			  		*/
 #include "H5MMprivate.h"	/* Memory management			*/
 #include "H5Pprivate.h"		/* Property lists			*/
+#include "H5Sprivate.h"		/* Dataspaces		  		*/
 #include "H5VLprivate.h"	/* VOL plugins				*/
 #include "H5VLiod.h"            /* Iod VOL plugin			*/
 #include "H5VLiod_common.h"
@@ -346,7 +347,7 @@ H5VL_iod_request_complete(H5VL_iod_file_t *file, H5VL_iod_request_t *req)
                 req->state = H5VL_IOD_COMPLETED;
             }
             if(HG_DSET_WRITE == req->type && SUCCEED != *((int *)info->status)) {
-                fprintf(stderr, "write failed %d\n", *((int *)info->status));
+                fprintf(stderr, "Errrr! Dataset Write Failure Reported from Server\n");
                 req->status = H5AO_FAILED;
                 req->state = H5VL_IOD_COMPLETED;
             }
@@ -354,7 +355,7 @@ H5VL_iod_request_complete(H5VL_iod_file_t *file, H5VL_iod_request_t *req)
                 H5VL_iod_read_status_t *read_status = (H5VL_iod_read_status_t *)info->status;
 
                 if(SUCCEED != read_status->ret) {
-                    fprintf(stderr, "read failed\n");
+                    fprintf(stderr, "Errrr! Dataset Read Failure Reported from Server\n");
                     req->status = H5AO_FAILED;
                     req->state = H5VL_IOD_COMPLETED;
                 }
@@ -362,15 +363,18 @@ H5VL_iod_request_complete(H5VL_iod_file_t *file, H5VL_iod_request_t *req)
                     uint32_t internal_cs;
 
                     /* calculate a checksum for the data recieved */
-                    internal_cs = H5_checksum_fletcher32(info->buf_ptr, info->buf_size);
+                    internal_cs = H5S_checksum(info->buf_ptr, info->type_size, 
+                                               info->nelmts, info->space);
 
                     /* verify data integrity */
                     if(internal_cs != read_status->cs) {
-                        fprintf(stderr, "Errrrr!  Data integrity failure (expecting %u got %u).\n",
+                        fprintf(stderr, "Errrrr!  Dataset Read integrity failure (expecting %u got %u).\n",
                                 read_status->cs, internal_cs);
                         req->status = H5AO_FAILED;
                         req->state = H5VL_IOD_COMPLETED;
                     }
+                    if(info->space && H5S_close(info->space) < 0)
+                        HDONE_ERROR(H5E_DATASPACE, H5E_CANTRELEASE, FAIL, "unable to release dataspace")
                 }
             }
 
@@ -394,7 +398,7 @@ H5VL_iod_request_complete(H5VL_iod_file_t *file, H5VL_iod_request_t *req)
                 req->state = H5VL_IOD_COMPLETED;
             }
             if(SUCCEED != *((int *)info->status)) {
-                fprintf(stderr, "write failed %d\n", *((int *)info->status));
+                fprintf(stderr, "Attribute I/O Failure Reported from Server\n");
                 req->status = H5AO_FAILED;
                 req->state = H5VL_IOD_COMPLETED;
             }
diff --git a/src/H5VLiod_client.h b/src/H5VLiod_client.h
index 1722690..9e10328 100644
--- a/src/H5VLiod_client.h
+++ b/src/H5VLiod_client.h
@@ -196,7 +196,9 @@ typedef struct H5VL_iod_io_info_t {
     void *status;
     hg_bulk_t *bulk_handle;
     void *buf_ptr;
-    size_t buf_size;
+    size_t nelmts;
+    size_t type_size;
+    struct H5S_t *space;
 } H5VL_iod_io_info_t;
 
 H5_DLL herr_t H5VL_iod_request_delete(H5VL_iod_file_t *file, H5VL_iod_request_t *request);
diff --git a/src/H5VLiod_server.c b/src/H5VLiod_server.c
index dfd3516..63c60c1 100644
--- a/src/H5VLiod_server.c
+++ b/src/H5VLiod_server.c
@@ -3368,11 +3368,14 @@ H5VL_iod_server_dset_read_cb(AXE_engine_t UNUSED axe_engine,
         if(H5Tconvert(src_id, dst_id, nelmts, buf, NULL, dxpl_id) < 0)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "data type conversion failed");
 
-        cs = H5_checksum_fletcher32(buf, size);
+        /* calculate a checksum for the data to be sent */
+        cs = H5_checksum_lookup3(buf, size, 0);
+
+        /* MSC - check if client requested to corrupt data */
         if(dxpl_id != H5P_DEFAULT && H5Pget_dxpl_inject_bad_checksum(dxpl_id, &flag) < 0)
             HGOTO_ERROR(H5E_SYM, H5E_READERROR, FAIL, "can't read property list");
         if(flag) {
-            fprintf(stderr, "Injecting a bad data value to generate a bad checksum \n");
+            fprintf(stderr, "Injecting a bad data value to cause corruption \n");
             buf_ptr[0] = 10;
         }
     }
@@ -3391,7 +3394,7 @@ done:
     output.ret = ret_value;
     output.cs = cs;
 
-    fprintf(stderr, "Done with dset read, sending response to client\n");
+    fprintf(stderr, "Done with dset read, checksum %u, sending response to client\n", cs);
 
     if(HG_SUCCESS != HG_Handler_start_output(op_data->hg_handle, &output))
         HDONE_ERROR(H5E_SYM, H5E_WRITEERROR, FAIL, "can't send result of write to client");
@@ -3444,6 +3447,7 @@ H5VL_iod_server_dset_write_cb(AXE_engine_t UNUSED axe_engine,
     size_t size, buf_size, src_size, dst_size;
     void *buf;
     size_t nelmts;
+    hbool_t flag = FALSE;
     na_addr_t source = HG_Handler_get_addr(op_data->hg_handle);
     herr_t ret_value = SUCCEED;
 
@@ -3495,11 +3499,18 @@ H5VL_iod_server_dset_write_cb(AXE_engine_t UNUSED axe_engine,
     if(HG_SUCCESS != HG_Bulk_block_handle_free(bulk_block_handle))
         HGOTO_ERROR(H5E_SYM, H5E_WRITEERROR, FAIL, "can't free bds block handle");
 
+    /* MSC - check if client requested to corrupt data */
+    if(dxpl_id != H5P_DEFAULT && H5Pget_dxpl_inject_bad_checksum(dxpl_id, &flag) < 0)
+        HGOTO_ERROR(H5E_SYM, H5E_READERROR, FAIL, "can't read property list");
+    if(flag) {
+        ((int *)buf)[0] = 10;
+    }
+
     /* If client specified a checksum, verify it */
     if(dxpl_id != H5P_DEFAULT && H5Pget_dxpl_checksum(dxpl_id, &data_cs) < 0)
         HGOTO_ERROR(H5E_SYM, H5E_READERROR, FAIL, "can't read property list");
     if(data_cs != 0) {
-        cs = H5_checksum_fletcher32(buf, size);
+        cs = H5_checksum_lookup3(buf, size, 0);
         if(cs != data_cs) {
             fprintf(stderr, "Errrr.. Network transfer Data corruption. expecting %u, got %u\n",
                     data_cs, cs);
diff --git a/src/H5checksum.c b/src/H5checksum.c
index ec8b2b0..de1e491 100644
--- a/src/H5checksum.c
+++ b/src/H5checksum.c
@@ -430,6 +430,175 @@ done:
     FUNC_LEAVE_NOAPI(c)
 } /* end H5_checksum_lookup3() */
 
+uint32_t
+H5_checksum_lookup4(const void *key, size_t length, H5_checksum_seed_t *cs)
+{
+    const uint8_t *k = (const uint8_t *)key;
+    uint32_t position = 0;
+    uint32_t a, b, c;           /* internal state */
+    int pos = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    /* Sanity check */
+    HDassert(key);
+    HDassert(length > 0);
+
+    /* Set up the internal state */
+    if(cs) {
+        if(!cs->a && !cs->b && !cs->c) {
+            a = b = c = 0xdeadbeef + ((uint32_t)cs->total_length);
+            /* Compute new State */
+            cs->state = 12 - (length % 12);
+        }
+        else {
+            a = cs->a;
+            b = cs->b;
+            c = cs->c;
+
+            /* determine position to start up on */
+            if(cs->state) {
+                position = 12 - cs->state + 1;
+            }
+
+            /* Compute new State */
+            cs->state = cs->state - (length % 12);
+            if(cs->state < 0) {
+                H5_lookup3_mix(a, b, c);
+                cs->state = 12 + cs->state;
+            }
+
+            /* Move towards mod 12 */
+            switch(position)                   /* all the case statements fall through */
+            {
+                case 0 : 
+                    break;
+                case 1 : 
+                    a+=k[pos++];
+                    length --;
+                    if(0 == length)
+                        break;
+                case 2 : 
+                    a+=((uint32_t)k[pos++])<<8;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 3 : 
+                    a+=((uint32_t)k[pos++])<<16;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 4 : 
+                    a+=((uint32_t)k[pos++])<<24;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 5 : 
+                    b+=k[pos++];
+                    length --;
+                    if(0 == length)
+                        break;
+                case 6 : 
+                    b+=((uint32_t)k[pos++])<<8;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 7 : 
+                    b+=((uint32_t)k[pos++])<<16;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 8 : 
+                    b+=((uint32_t)k[pos++])<<24;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 9 : 
+                    c+=k[pos++];
+                    length --;
+                    if(0 == length)
+                        break;
+                case 10: 
+                    c+=((uint32_t)k[pos++])<<8;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 11: 
+                    c+=((uint32_t)k[pos++])<<16;
+                    length --;
+                    if(0 == length)
+                        break;
+                case 12: 
+                    c+=((uint32_t)k[pos++])<<24;
+                    length --;
+                    H5_lookup3_mix(a, b, c);
+                    break;
+            }
+        }
+        /* capture internal state if we are done at this stage */
+        if(0 == length) {
+            cs->a = a;
+            cs->b = b;
+            cs->c = c;
+            H5_lookup3_final(a, b, c);
+            goto done;
+        }
+    }
+    else
+        a = b = c = 0xdeadbeef + ((uint32_t)length);
+
+    /*--------------- all but the last block: affect some 32 bits of (a,b,c) */
+    while (length > 12)
+    {
+      a += k[0+pos];
+      a += ((uint32_t)k[1+pos])<<8;
+      a += ((uint32_t)k[2+pos])<<16;
+      a += ((uint32_t)k[3+pos])<<24;
+      b += k[4+pos];
+      b += ((uint32_t)k[5+pos])<<8;
+      b += ((uint32_t)k[6+pos])<<16;
+      b += ((uint32_t)k[7+pos])<<24;
+      c += k[8+pos];
+      c += ((uint32_t)k[9+pos])<<8;
+      c += ((uint32_t)k[10+pos])<<16;
+      c += ((uint32_t)k[11+pos])<<24;
+      H5_lookup3_mix(a, b, c);
+      length -= 12;
+      k += 12;
+    }
+
+    /*-------------------------------- last block: affect all 32 bits of (c) */
+    switch(length)                   /* all the case statements fall through */
+    {
+        case 12: c+=((uint32_t)k[11+pos])<<24;
+        case 11: c+=((uint32_t)k[10+pos])<<16;
+        case 10: c+=((uint32_t)k[9+pos])<<8;
+        case 9 : c+=k[8+pos];
+        case 8 : b+=((uint32_t)k[7+pos])<<24;
+        case 7 : b+=((uint32_t)k[6+pos])<<16;
+        case 6 : b+=((uint32_t)k[5+pos])<<8;
+        case 5 : b+=k[4+pos];
+        case 4 : a+=((uint32_t)k[3+pos])<<24;
+        case 3 : a+=((uint32_t)k[2+pos])<<16;
+        case 2 : a+=((uint32_t)k[1+pos])<<8;
+        case 1 : a+=k[pos];
+                 break;
+        case 0 : goto done;
+    }
+
+    /* capture internal state */
+    if(cs) {
+        cs->a = a;
+        cs->b = b;
+        cs->c = c;
+    }
+
+    H5_lookup3_final(a, b, c);
+
+done:
+    FUNC_LEAVE_NOAPI(c)
+} /* end H5_checksum_lookup3() */
+
 
 /*-------------------------------------------------------------------------
  * Function:	H5_checksum_metadata
diff --git a/src/H5private.h b/src/H5private.h
index 46c02e7..42ea519 100644
--- a/src/H5private.h
+++ b/src/H5private.h
@@ -2361,6 +2361,7 @@ H5_DLL int H5Z_term_interface(void);
 H5_DLL uint32_t H5_checksum_fletcher32(const void *data, size_t len);
 H5_DLL uint32_t H5_checksum_crc(const void *data, size_t len);
 H5_DLL uint32_t H5_checksum_lookup3(const void *data, size_t len, uint32_t initval);
+H5_DLL uint32_t H5_checksum_lookup4(const void *data, size_t len, H5_checksum_seed_t *cs);
 H5_DLL uint32_t H5_checksum_metadata(const void *data, size_t len, uint32_t initval);
 H5_DLL uint32_t H5_hash_string(const char *str);
 
diff --git a/src/H5public.h b/src/H5public.h
index deb4587..d0f3e78 100644
--- a/src/H5public.h
+++ b/src/H5public.h
@@ -301,6 +301,15 @@ typedef struct H5_ih_info_t {
     hsize_t     heap_size;
 } H5_ih_info_t;
 
+/* Internal Checksum state */
+typedef struct H5_checksum_seed_t {
+    uint32_t a;
+    uint32_t b;
+    uint32_t c;
+    int32_t state;
+    size_t total_length;
+} H5_checksum_seed_t;
+
 /* Functions in H5.c */
 H5_DLL herr_t H5open(void);
 H5_DLL herr_t H5close(void);