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<HTML><HEAD>
<TITLE>HDF5 Tutorial - Selections using H5Sselect_elements and H5Scopy
</TITLE>
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<H1>
<BIG><BIG><BIG><FONT COLOR="#c101cd">Selections using H5Sselect_elements and H5SCopy</FONT>
</BIG></BIG></BIG></H1>
<hr noshade size=1>
<BODY>
<H2>Contents:</H2>
<UL>
<LI> <A HREF="#def">Selecting Independent Points and Copying a Dataspace</A>
<LI> Programming Example
<UL>
<LI> <A HREF="#desc">Description</A>
<LI> <A HREF="#rem">Remarks</A>
<LI> <A HREF="#fc">File Contents</A>
</UL>
</UL>
<HR>
<A NAME="def">
<H2>Selecting Independent Points and Copying a Dataspace</h2>
You can select independent points to read or write to in a
dataspace by use of the H5Sselect_elements function.
<P>
The H5Scopy function allows you to make an exact copy of a dataspace,
which can help cut down on the number of function calls needed when
selecting a dataspace.
<P>
<H2> Programming Example</H2>
<A NAME="desc">
<H3><U>Description</U></H3>
This example shows you how to use H5Sselect_elements to select individual
points in a dataset and how to use H5Scopy to make a copy of a dataspace.
[ <A HREF="examples/h5_copy.c">Download h5_copy.c</A> ]
<PRE>
/***********************************************************************/
/* */
/* PROGRAM: h5_copy.c */
/* PURPOSE: Shows how to use the H5SCOPY function. */
/* DESCRIPTION: */
/* This program creates two files, copy1.h5, and copy2.h5. */
/* In copy1.h5, it creates a 3x4 dataset called 'Copy1', */
/* and write 0's to this dataset. */
/* In copy2.h5, it create a 3x4 dataset called 'Copy2', */
/* and write 1's to this dataset. */
/* It closes both files, reopens both files, selects two */
/* points in copy1.h5 and writes values to them. Then it */
/* does an H5Scopy from the first file to the second, and */
/* writes the values to copy2.h5. It then closes the */
/* files, reopens them, and prints the contents of the */
/* two datasets. */
/* */
/***********************************************************************/
#include "hdf5.h"
#define FILE1 "copy1.h5"
#define FILE2 "copy2.h5"
#define RANK 2
#define DIM1 3
#define DIM2 4
#define NUMP 2
int main (void)
{
hid_t file1, file2, dataset1, dataset2;
hid_t mid1, mid2, fid1, fid2;
hsize_t fdim[] = {DIM1, DIM2};
hsize_t mdim[] = {DIM1, DIM2};
hsize_t start[2], stride[2], count[2], block[2];
int buf1[DIM1][DIM2];
int buf2[DIM1][DIM2];
int bufnew[DIM1][DIM2];
int val[] = {53, 59};
hsize_t marray[] = {2};
hssize_t coord[NUMP][RANK];
herr_t ret;
uint i, j;
/***********************************************************************/
/* */
/* Create two files containing identical datasets. Write 0's to one */
/* and 1's to the other. */
/* */
/***********************************************************************/
for ( i = 0; i < DIM1; i++ )
for ( j = 0; j < DIM2; j++ )
buf1[i][j] = 0;
for ( i = 0; i < DIM1; i++ )
for ( j = 0; j < DIM2; j++ )
buf2[i][j] = 1;
file1 = H5Fcreate(FILE1, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
file2 = H5Fcreate(FILE2, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT);
fid1 = H5Screate_simple (RANK, fdim, NULL);
fid2 = H5Screate_simple (RANK, fdim, NULL);
dataset1 = H5Dcreate (file1, "Copy1", H5T_NATIVE_INT, fid1, H5P_DEFAULT);
dataset2 = H5Dcreate (file2, "Copy2", H5T_NATIVE_INT, fid2, H5P_DEFAULT);
ret = H5Dwrite(dataset1, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf1);
ret = H5Dwrite(dataset2, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, buf2);
ret = H5Dclose (dataset1);
ret = H5Dclose (dataset2);
ret = H5Sclose (fid1);
ret = H5Sclose (fid2);
ret = H5Fclose (file1);
ret = H5Fclose (file2);
/***********************************************************************/
/* */
/* Open the two files. Select two points in one file, write values to */
/* those point locations, then do H5Scopy and write the values to the */
/* other file. Close files. */
/* */
/***********************************************************************/
file1 = H5Fopen (FILE1, H5F_ACC_RDWR, H5P_DEFAULT);
file2 = H5Fopen (FILE2, H5F_ACC_RDWR, H5P_DEFAULT);
dataset1 = H5Dopen (file1, "Copy1");
dataset2 = H5Dopen (file2, "Copy2");
fid1 = H5Dget_space (dataset1);
mid1 = H5Screate_simple(1, marray, NULL);
coord[0][0] = 0; coord[0][1] = 3;
coord[1][0] = 0; coord[1][1] = 1;
ret = H5Sselect_elements (fid1, H5S_SELECT_SET, NUMP, (const hssize_t **)coord);
ret = H5Dwrite (dataset1, H5T_NATIVE_INT, mid1, fid1, H5P_DEFAULT, val);
fid2 = H5Scopy (fid1);
ret = H5Dwrite (dataset2, H5T_NATIVE_INT, mid1, fid2, H5P_DEFAULT, val);
ret = H5Dclose (dataset1);
ret = H5Dclose (dataset2);
ret = H5Sclose (fid1);
ret = H5Sclose (fid2);
ret = H5Fclose (file1);
ret = H5Fclose (file2);
ret = H5Sclose (mid1);
/***********************************************************************/
/* */
/* Open both files and print the contents of the datasets. */
/* */
/***********************************************************************/
file1 = H5Fopen (FILE1, H5F_ACC_RDWR, H5P_DEFAULT);
file2 = H5Fopen (FILE2, H5F_ACC_RDWR, H5P_DEFAULT);
dataset1 = H5Dopen (file1, "Copy1");
dataset2 = H5Dopen (file2, "Copy2");
ret = H5Dread (dataset1, H5T_NATIVE_INT, H5S_ALL, H5S_ALL,
H5P_DEFAULT, bufnew);
printf ("\nDataset 'Copy1' in file 'copy1.h5' contains: \n");
for (i=0;i<DIM1; i++) {
for (j=0;j<DIM2;j++) printf ("%3d ", bufnew[i][j]);
printf("\n");
}
printf ("\nDataset 'Copy2' in file 'copy2.h5' contains: \n");
ret = H5Dread (dataset2, H5T_NATIVE_INT, H5S_ALL, H5S_ALL,
H5P_DEFAULT, bufnew);
for (i=0;i<DIM1; i++) {
for (j=0;j<DIM2;j++) printf ("%3d ", bufnew[i][j]);
printf("\n");
}
ret = H5Dclose (dataset1);
ret = H5Dclose (dataset2);
ret = H5Fclose (file1);
ret = H5Fclose (file2);
}
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
</PRE>
<A NAME="rem">
<H3><U>Remarks</U></H3>
<UL>
<LI>H5Sselect_elements selects array elements to be included in the
selection for a dataspace:
<PRE>
herr_t H5Sselect_elements (hid_t space_id, H5S_seloper_t op,
size_t num_elem, const hssize_t **coord )
</PRE>
<UL>
<LI>The <I>space_id</I> parameter is the dataspace identifier.<BR>
<LI>The <I>op</I> parameter currently can only be set to H5S_SELECT_SET and
specifies to replace the existing selection with the parameters from this
call.
<LI>The <I>coord</I> array is a two-dimensional array of size 'dataspace rank'
by the number of elements to be selected, <I>num_elem</I>.<BR>
</UL>
<P>
<LI>H5Scopy creates an exact copy of a dataspace:
<PRE>
hid_t H5Scopy(hid_t space_id )
</PRE>
<UL>
<LI>The <I>space_id</I> parameter is the dataspace identifier to copy.
</UL>
</UL>
</UL>
<P>
<A NAME="fc">
<H3><U>File Contents</U></H3>
Following is the DDL for <I>copy1.h5</I> and <I>copy2.h5</I>, as viewed with
the commands "h5dump copy1.h5" and "h5dump copy2.h5".
<P>
<B>Fig. S.1</B> <I>'copy1.h5' in DDL</I>
<PRE>
HDF5 "copy1.h5" {
GROUP "/" {
DATASET "Copy1" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 3, 4 ) / ( 3, 4 ) }
DATA {
0, 59, 0, 53,
0, 0, 0, 0,
0, 0, 0, 0
}
}
}
}
</PRE>
<B>Fig. S.2</B> <I>'copy2.h5' in DDL</I>
<PRE>
HDF5 "copy2.h5" {
GROUP "/" {
DATASET "Copy2" {
DATATYPE { H5T_STD_I32BE }
DATASPACE { SIMPLE ( 3, 4 ) / ( 3, 4 ) }
DATA {
1, 59, 1, 53,
1, 1, 1, 1,
1, 1, 1, 1
}
}
}
}
</PRE>
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<BR> <H6>Last Modified: August 27, 1999</H6><BR>
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