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diff --git a/java/src/hdf/overview.html b/java/src/hdf/overview.html new file mode 100644 index 0000000..39d75b7 --- /dev/null +++ b/java/src/hdf/overview.html @@ -0,0 +1,96 @@ +<body> + +<h1>Java HDF5 Interface (JHI5)</h1> + +<h2><u>What it is</u></h2> +The <b>Java HD5 Interface (JHI5)</b> is a Java package +(<a href="../../hdf-java-html/javadocs/hdf/hdf5lib/package-summary.html">hdf.hdf5lib</a>) +that ``wraps around'' the HDF5 library. +<p />There are a large number of functions in the HDF5 +library (version 1.10). Some of the functions are not supported in JHI5. Most +of the unsupported functions have C function pointers, which is not currently +implemented in JHI5. + +<center><table BORDER=1 COLS=1 WIDTH="71%" BGCOLOR="#dbeaf5" > +<tr> +<td> +<center>Note: The JHI5 does not support HDF4 or earlier.</center> +</td> +</tr> +</table></center> + +<p>The JHI5 may be used by any Java application that needs to access HDF5 +files. It is extremely important to emphasize that <i>this package is not +a pure Java implementation of the HDF5 library.</i> The JHI5 calls the +same HDF5 library that is used by C or FORTRAN programs. (Note that this +product cannot be used in most network browsers because it accesses the +local disk using native code.) +<p>The Java HDF5 Interface consists of Java classes and a dynamically +linked native library. The Java classes declare native methods, and the +library contains C functions which implement the native methods. The C +functions call the standard HDF5 library, which is linked as part of the +same library on most platforms. +<p>The central part of the JHI5 is the Java class <i> +<a href="../../hdf-java-html/javadocs/hdf/hdf5lib/H5.html">hdf.hdf5lib.H5</a></i>. +The <i>H5 </i>class calls the standard (<i>i.e.</i>, `native' code) HDF5 +library, with native methods for most of the HDF5 functions. + +<h3> +<u>How to use it</u></h3> +The JHI5 is used by Java classes to call the HDF5 library, in order to +create HDF5 files, and read and write data in existing HDF5 files. +<p>For example, the HDF5 library has the function <b>H5Fopen</b> to open +an HDF5 file. The Java interface is the class <i> +<a href="../../hdf-java-html/javadocs/hdf/hdf5lib/H5.html">hdf.hdf5lib.H5</a></i>, +which has a method: +<pre><b>static native int H5Fopen(String filename, int flags, int access );</b></pre> +The native method is implemented in C using the +<a href="http://java.sun.com/javase/6/docs/technotes/guides/jni/index.html">Java +Native Method Interface </a>(JNI). This is written something like the following: +<pre><b>JNIEXPORT jint +JNICALL Java_hdf_hdf5lib_H5_H5Fopen +( + JNIEnv *env, + jclass class, + jstring hdfFile, + jint flags, + jint access) + { + + /* ...convert Java String to (char *) */ + + /* call the HDF library */ + retVal = H5Fopen((char *)file, (unsigned)flags, (hid_t)access ); + + /* ... */ +}</b></pre> +This C function calls the HDF5 library and returns the result appropriately. +<p>There is one native method for each HDF entry point (several hundred +in all), which are compiled with the HDF library into a dynamically loaded +library (<i>libhdf5_java</i>). Note that this library must be built for each +platform. +<p>To call the HDF `<b><i>H5Fopen</i></b>' function, a Java program would +import the package '<i><b>hdf.hdf5lib.*</b>'</i>, and invoke the method +on the class '<b><i>H5</i></b>'. The Java program would look something +like this: +<pre><b>import hdf.hdf5lib.*; + +{ + /* ... */ + + try { + file = H5.Hopen("myFile.hdf", flags, access ); + } catch (HDF5Exception ex) { + //... + } + + /* ... */ +}</b></pre> +The <i><b>H5</b> </i>class automatically loads the native method implementations +and the HDF5 library. + +<h3> +<a NAME="DOWNLOAD"></a>To Obtain</h3> +The JHI5 is included with the <a href="http://www.hdfgroup.org/HDF5/index.html">HDF5</a> library. + +</body> |