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Diffstat (limited to 'java/src/hdf/hdf5lib/package-info.java')
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diff --git a/java/src/hdf/hdf5lib/package-info.java b/java/src/hdf/hdf5lib/package-info.java new file mode 100644 index 0000000..e742197 --- /dev/null +++ b/java/src/hdf/hdf5lib/package-info.java @@ -0,0 +1,202 @@ +/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * + * Copyright by The HDF Group. * + * All rights reserved. * + * * + * This file is part of HDF5. The full HDF5 copyright notice, including * + * terms governing use, modification, and redistribution, is contained in * + * the COPYING file, which can be found at the root of the source code * + * distribution tree, or in https://www.hdfgroup.org/licenses. * + * If you do not have access to either file, you may request a copy from * + * help@hdfgroup.org. * + * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ + +/** + @page HDF5LIB_UG HDF5 Java Package + * This package is the Java interface for the HDF5 library. + * <p> + * This code is the called by Java programs to access the entry points of the HDF5 library. + * Each routine wraps a single + * HDF5 entry point, generally with the arguments and return codes analogous to the C interface. + * <p> + * For details of the HDF5 library, see the HDF5 Documentation at: + * <a href="http://hdfgroup.org/HDF5/">http://hdfgroup.org/HDF5/</a> + * <hr> + * <p> + * <b>Mapping of arguments for Java</b> + * + * <p> + * In general, arguments to the HDF Java API are straightforward translations from the 'C' API described + * in the HDF Reference Manual. + * + * <table border=1> + * <caption><b>HDF5 C types to Java types</b> </caption> + * <tr> + * <td><b>HDF5</b></td> + * <td><b>Java</b></td> + * </tr> + * <tr> + * <td>H5T_NATIVE_INT</td> + * <td>int, Integer</td> + * </tr> + * <tr> + * <td>H5T_NATIVE_SHORT</td> + * <td>short, Short</td> + * </tr> + * <tr> + * <td>H5T_NATIVE_FLOAT</td> + * <td>float, Float</td> + * </tr> + * <tr> + * <td>H5T_NATIVE_DOUBLE</td> + * <td>double, Double</td> + * </tr> + * <tr> + * <td>H5T_NATIVE_CHAR</td> + * <td>byte, Byte</td> + * </tr> + * <tr> + * <td>H5T_C_S1</td> + * <td>java.lang.String</td> + * </tr> + * <tr> + * <td>void * <br /> + * (i.e., pointer to `Any')</td> + * <td>Special -- see HDFArray</td> + * </tr> + * </table> + * <b>General Rules for Passing Arguments and Results</b> + * <p> + * In general, arguments passed <b>IN</b> to Java are the analogous basic types, as above. The exception + * is for arrays, which are discussed below. + * <p> + * The <i>return value</i> of Java methods is also the analogous type, as above. A major exception to that + * rule is that + * all HDF functions that return SUCCEED/FAIL are declared <i>boolean</i> in the Java version, rather than + * <i>int</i> as + * in the C. Functions that return a value or else FAIL are declared the equivalent to the C function. + * However, in most + * cases the Java method will raise an exception instead of returning an error code. + * @see @ref ERRORS. + * <p> + * Java does not support pass by reference of arguments, so arguments that are returned through <b>OUT</b> + * parameters + * must be wrapped in an object or array. The Java API for HDF consistently wraps arguments in arrays. + * <p> + * For instance, a function that returns two integers is declared: + * + * <pre> + * h_err_t HDF5dummy( int *a1, int *a2) + * </pre> + * + * For the Java interface, this would be declared: + * + * <pre> + * public synchronized static native void HDF5dummy(int args[]); + * </pre> + * + * where <i>a1</i> is <i>args[0]</i> and <i>a2</i> is <i>args[1]</i>, and would be invoked: + * + * <pre> + * H5.HDF5dummy(a); + * </pre> + * + * <p> + * All the routines where this convention is used will have specific documentation of the details, given + * below. + * <p> + * <b>Arrays</b> + * <p> + * HDF5 needs to read and write multi-dimensional arrays of any number type (and records). The HDF5 API + * describes the + * layout of the source and destination, and the data for the array passed as a block of bytes, for instance, + * + * <pre> + * herr_t H5Dread(long fid, long filetype, long memtype, long memspace, void *data); + * </pre> + * + * <p> + * where ``void *'' means that the data may be any valid numeric type, and is a contiguous block of bytes that + * is the + * data for a multi-dimensional array. The other parameters describe the dimensions, rank, and datatype of the + * array on + * disk (source) and in memory (destination). + * <p> + * For Java, this ``ANY'' is a problem, as the type of data must always be declared. Furthermore, + * multidimensional + * arrays are definitely <i>not</i> laid out contiguously in memory. It would be infeasible to declare a + * separate + * routine for every combination of number type and dimensionality. For that reason, the + * <a href="./HDFArray.html"><b>HDFArray</b></a> class is used to discover the type, shape, and + * size of the + * data array at run time, and to convert to and from a contiguous array of bytes in synchronized static + * native C order. + * <p> + * The upshot is that any Java array of numbers (either primitive or sub-classes of type <b>Number</b>) can be + * passed as + * an ``Object'', and the Java API will translate to and from the appropriate packed array of bytes needed by + * the C + * library. So the function above would be declared: + * + * <pre> + * public synchronized static native int H5Dread(long fid, long filetype, long memtype, long memspace, Object + * data); + * </pre> + * OPEN_IDS.addElement(id); + + * and the parameter <i>data</i> can be any multi-dimensional array of numbers, such as float[][], or + * int[][][], or + * Double[][]. + * <p> + * <b>HDF5 Constants</b> + * <p> + * The HDF5 API defines a set of constants and enumerated values. Most of these values are available to Java + * programs + * via the class <a href="./HDF5Constants.html"> <b>HDF5Constants</b></a>. For example, the + * parameters for + * the h5open() call include two numeric values, <b><i>HDFConstants.H5F_ACC_RDWR</i></b> and + * <b><i>HDF5Constants.H5P_DEFAULT</i></b>. As would be expected, these numbers correspond to the C constants + * <b><i>H5F_ACC_RDWR</i></b> and <b><i>H5P_DEFAULT</i></b>. + * <p> + * The HDF5 API defines a set of values that describe number types and sizes, such as "H5T_NATIVE_INT" and + * "hsize_t". + * These values are determined at run time by the HDF5 C library. To support these parameters, the Java class + * <a href="./HDF5CDataTypes.html"> <b>HDF5CDataTypes</b></a> looks up the values when initiated. + * The values + * can be accessed as public variables of the Java class, such as: + * + * <pre> + * long data_type = HDF5CDataTypes.JH5T_NATIVE_INT; + * </pre> + * + * The Java application uses both types of constants the same way, the only difference is that the + * <b><i>HDF5CDataTypes</i></b> may have different values on different platforms. + * <p> + * <b>Error handling and Exceptions</b> + * <p> + * The HDF5 error API (H5E) manages the behavior of the error stack in the HDF5 library. This API is + * available from the + * JHI5. Errors are converted into Java exceptions. This is totally different from the C interface, but is + * very natural + * for Java programming. + * <p> + * The exceptions of the JHI5 are organized as sub-classes of the class + * <a href="./HDF5Exception.html"> <b>HDF5Exception</b></a>. There are two subclasses + * of + * <b>HDF5Exception</b>, @ref ERRORSLIB <b>HDF5LibraryException</b> + * and @ref ERRORSJAVA <b>HDF5JavaException</b>. + * The sub-classes of the former represent errors from the HDF5 C library, + * while sub-classes of the latter represent errors in the JHI5 wrapper and support code. + * <p> + * The super-class <b><i>HDF5LibraryException</i></b> implements the method + * '<b><i>printStackTrace()</i></b>', which prints out the HDF5 error stack, as described + * in the HDF5 C API <i><b>@ref H5Eprint()</b>.</i> This may be + * used by Java + * exception handlers to print out the HDF5 error stack. + * <hr> + * + * @ref HDF5LIB + * + * <b>@see: <a href="http://hdfgroup.org/HDF5/"> HDF5"</a></b> + * + */ +package hdf.hdf5lib; |