[svn-r8901] Purpose:

    Bug fix

Description:
    Allow buffer parameter to H5Dread & H5Dwrite to be NULL if there are no
elements to transfer.

Platforms tested:
    FreeBSD 4.10 (sleipnir) w/parallel
    Too minor to require h5committest

3 files changed, 28 insertions, 7 deletions

diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 68d531c..c9d8bf9 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -146,11 +146,14 @@ Bug Fixes since HDF5-1.6.0 release
 
     Library
     -------
+        - Allow NULL pointer for buffer parameter to H5Dread & H5Dwrite
+            when not writing data ("none" selection or hyperslab or point
+            selection with no elements defined).  QAK - 2004/07/20
         - Calling H5Gcreate() on "/" or "." throws an error instead of
-          failing quietly. JML - 2004/07/19
+            failing quietly. JML - 2004/07/19
         - Fixed bug where setting file address size to be very small could
-          trigger an assert if the file grew to more than 64 KB.  Now throws
-          an error and data can be recovered. JL/NF - 2004/07/14
+            trigger an assert if the file grew to more than 64 KB.  Now throws
+            an error and data can be recovered. JL/NF - 2004/07/14
         - Fixed bug where "resurrecting" a dataset was failing.
             QAK - 2004/07/14
         - Fixed bug where incorrect data could be read from a chunked dataset
diff --git a/src/H5Dio.c b/src/H5Dio.c
index 0d9a91c..fb07831 100644
--- a/src/H5Dio.c
+++ b/src/H5Dio.c
@@ -480,7 +480,7 @@ H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     else
         if (TRUE!=H5P_isa_class(plist_id,H5P_DATASET_XFER))
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not xfer parms")
-    if (!buf)
+    if (!buf && H5S_GET_SELECT_NPOINTS(file_space)!=0)
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no output buffer")
 
     /* read raw data */
@@ -568,7 +568,7 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     else
         if (TRUE!=H5P_isa_class(plist_id,H5P_DATASET_XFER))
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not xfer parms")
-    if (!buf)
+    if (!buf && H5S_GET_SELECT_NPOINTS(file_space)!=0)
 	HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no output buffer")
 
     /* write raw data */
@@ -649,7 +649,6 @@ H5D_read(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
 
     /* check args */
     assert(dataset && dataset->ent.file);
-    assert(buf);
 
     /* Get memory datatype */
     if (NULL == (mem_type = H5I_object_verify(mem_type_id, H5I_DATATYPE)))
@@ -846,7 +845,6 @@ H5D_write(H5D_t *dataset, hid_t mem_type_id, const H5S_t *mem_space,
 
     /* check args */
     assert(dataset && dataset->ent.file);
-    assert(buf);
 
     /* Get the memory datatype */
     if (NULL == (mem_type = H5I_object_verify(mem_type_id, H5I_DATATYPE)))
diff --git a/test/tselect.c b/test/tselect.c
index 228002c..c1d985f 100644
--- a/test/tselect.c
+++ b/test/tselect.c
@@ -253,6 +253,12 @@ test_select_hyper(hid_t xfer_plist)
     ret=H5Dwrite(dataset,H5T_NATIVE_UCHAR,sid2,sid1,xfer_plist,wbuf);
     CHECK(ret, FAIL, "H5Dwrite");
 
+    /* Exercise check for NULL buffer and valid selection */
+    H5E_BEGIN_TRY {
+        ret=H5Dwrite(dataset,H5T_NATIVE_UCHAR,sid2,sid1,xfer_plist,NULL);
+    } H5E_END_TRY;
+    VERIFY(ret, FAIL, "H5Dwrite");
+
     /* Close memory dataspace */
     ret = H5Sclose(sid2);
     CHECK(ret, FAIL, "H5Sclose");
@@ -273,6 +279,12 @@ test_select_hyper(hid_t xfer_plist)
     ret=H5Dread(dataset,H5T_NATIVE_UCHAR,sid2,sid1,xfer_plist,rbuf);
     CHECK(ret, FAIL, "H5Dread");
 
+    /* Exercise check for NULL buffer and valid selection */
+    H5E_BEGIN_TRY {
+        ret=H5Dread(dataset,H5T_NATIVE_UCHAR,sid2,sid1,xfer_plist,NULL);
+    } H5E_END_TRY;
+    VERIFY(ret, FAIL, "H5Dread");
+
     /* Check that the values match with a dataset iterator */
     tbuf=wbuf+(15*SPACE2_DIM2);
     ret = H5Diterate(rbuf,H5T_NATIVE_UCHAR,sid2,test_select_hyper_iter1,&tbuf);
@@ -5408,6 +5420,14 @@ test_select_none(void)
     ret=H5Dwrite(dataset,H5T_NATIVE_INT,sid2,sid1,H5P_DEFAULT,wbuf);
     CHECK(ret, FAIL, "H5Dwrite");
 
+    /* Write "nothing" to disk (with NULL buffer argument) */
+    ret=H5Dwrite(dataset,H5T_NATIVE_INT,sid2,sid1,H5P_DEFAULT,NULL);
+    CHECK(ret, FAIL, "H5Dwrite");
+
+    /* Read "nothing" from disk (with NULL buffer argument) */
+    ret=H5Dread(dataset,H5T_NATIVE_INT,sid2,sid1,H5P_DEFAULT,NULL);
+    CHECK(ret, FAIL, "H5Dread");
+
     /* Close memory dataspace */
     ret = H5Sclose(sid2);
     CHECK(ret, FAIL, "H5Sclose");