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| author | Frank Baker <fbaker@hdfgroup.org> | 2005-07-19 17:28:56 (GMT) |
|---|---|---|
| committer | Frank Baker <fbaker@hdfgroup.org> | 2005-07-19 17:28:56 (GMT) |
| commit | 794ba0a251af47b8e3c60afa2fe92d267e2a6b55 (patch) | |
| tree | f24cea3b81ff02fa3f31c0a1c4e80fa10f4393c0 /doc/html/References.html | |
| parent | d2e92fd23610c3ccdddbbc55484e54a5a21a9252 (diff) | |
| download | hdf5-794ba0a251af47b8e3c60afa2fe92d267e2a6b55.zip hdf5-794ba0a251af47b8e3c60afa2fe92d267e2a6b55.tar.gz hdf5-794ba0a251af47b8e3c60afa2fe92d267e2a6b55.tar.bz2 | |
[svn-r11084]
Description:
All HDF5 user documentation has been moved to a separate hdf5doc/
repository, managed under Subversion.
With this 'cvs commit', all files are stripped from hdf5/doc/.
THIS CHANGE IS APPLIED ONLY TO THE HDF5 DEVELOPMENT BRANCH,
post Release 1.6.x; it is not applied to the release branches.
Diffstat (limited to 'doc/html/References.html')
| -rw-r--r-- | doc/html/References.html | 651 |
1 files changed, 0 insertions, 651 deletions
diff --git a/doc/html/References.html b/doc/html/References.html deleted file mode 100644 index 766b92c..0000000 --- a/doc/html/References.html +++ /dev/null @@ -1,651 +0,0 @@ -<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML//EN"> -<html> -<head> -<title>Reference (H5R) and Identifier Interfaces (H5I)</title> - -<!-- #BeginLibraryItem "/ed_libs/styles_UG.lbi" --> -<!-- - * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - * Copyright by the Board of Trustees of the University of Illinois. * - * 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 files COPYING and Copyright.html. COPYING can be found at the root * - * of the source code distribution tree; Copyright.html can be found at the * - * root level of an installed copy of the electronic HDF5 document set and * - * is linked from the top-level documents page. It can also be found at * - * http://hdf.ncsa.uiuc.edu/HDF5/doc/Copyright.html. If you do not have * - * access to either file, you may request a copy from hdfhelp@ncsa.uiuc.edu. * - * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - --> - -<link href="ed_styles/UGelect.css" rel="stylesheet" type="text/css"> -<!-- #EndLibraryItem --></head> - -<body bgcolor="#FFFFFF"> - - -<!-- #BeginLibraryItem "/ed_libs/NavBar_UG.lbi" --><hr> -<center> -<table border=0 width=98%> -<tr><td valign=top align=left> - <a href="index.html">HDF5 documents and links</a> <br> - <a href="H5.intro.html">Introduction to HDF5</a> <br> - <a href="RM_H5Front.html">HDF5 Reference Manual</a> <br> - <a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide for Release 1.6</a> <br> - <!-- - <a href="Glossary.html">Glossary</a><br> - --> -</td> -<td valign=top align=right> - And in this document, the - <a href="H5.user.html"><strong>HDF5 User's Guide from Release 1.4.5:</strong></a> - <br> - <a href="Files.html">Files</a> - <a href="Datasets.html">Datasets</a> - <a href="Datatypes.html">Datatypes</a> - <a href="Dataspaces.html">Dataspaces</a> - <a href="Groups.html">Groups</a> - <br> - <a href="References.html">References</a> - <a href="Attributes.html">Attributes</a> - <a href="Properties.html">Property Lists</a> - <a href="Errors.html">Error Handling</a> - <br> - <a href="Filters.html">Filters</a> - <a href="Caching.html">Caching</a> - <a href="Chunking.html">Chunking</a> - <a href="MountingFiles.html">Mounting Files</a> - <br> - <a href="Performance.html">Performance</a> - <a href="Debugging.html">Debugging</a> - <a href="Environment.html">Environment</a> - <a href="ddl.html">DDL</a> -</td></tr> -</table> -</center> -<hr> -<!-- #EndLibraryItem --><h1>The Reference Interface (H5R) and <br> the Identifier Interface (H5I)</h1> - -<h2>1. Introduction</h2> - -This document discusses the kinds of references implemented -(and planned) in HDF5 and the functions implemented (and planned) -to support them. - - -<h2>2. References</h2> - -This section contains an overview of the kinds of references -implemented, or planned for implementation, in HDF5. - -<p> - -<dl> - <dt>Object reference - <dd>Reference to an entire object in the current HDF5 file. - <p> - An object reference points to an entire object in the - current HDF5 file by storing the relative file address - (OID) of the object header for the object pointed to. - The relative file address of an object header is - constant for the life of the object. - An object reference is of a fixed size in the file. - <p> - <dt>Dataset region reference - <dd>Reference to a specific dataset region. - <p> - A dataset region reference points to a region of a - dataset in the current HDF5 file by storing the OID - of the dataset and the global heap offset of the - region referenced. The region referenced is located - by retrieving the coordinates of the areas in the - region from the global heap. A dataset region - reference is of a variable size in the file. -</dl> - - -<b>Note:</b> All references are treated as soft links for the -purposes of reference counting. The library does not keep track of -reference links and they may dangle if the object they refer to -is deleted, moved, or not yet available. - - -<h2>3. Reference Types</h2> - -Valid HDF5 reference types for use in the H5R functions -are as follows: - -<center> -<table> -<tr><th align=left>Reference Type</th><th align=left>Value </th><th align=left>Description</th></tr> -<!-- NOT USER-LEVEL INFORMATION; DELETED FROM HDF5 USER'S GUIDE -<tr><td><code>H5R_BADTYPE</code></td> - <td align=right><code>-1 </code></td> - <td>Invalid reference type</td></tr> ---> -<tr><td><code>H5R_OBJECT</code></td> - <td align=right><code>0 </code></td> - <td>Object reference</td></tr> -<tr><td><code>H5R_DATASET_REGION</code></td> - <td align=right><code>1 </code></td> - <td>Dataset region reference</td></tr> -</table> -</center> - - -<h2>4. Functions</h2> - -Five functions, four in the H5R interface and one in the -H5I interface, have been implemented to support references. -The H5I function is also useful outside the context of references. -<p> -<dl> - <dt><em>herr_t</em> <code>H5Rcreate(</code><em>void *</em><code>reference,</code> - <em>hid_t</em> <code>loc_id,</code> - <em>const char *</em><code>name,</code> - <em>H5R_type_t</em> <code>type,</code> - <em>hid_t</em> <code>space_id)</code> - <dd><code>H5Rcreate</code> creates an object which is a - particular type of reference (specified with the - <code>type</code> parameter) to some file object and/or - location specified with the <code>space_id</code> parameter. - For dataset region references, the selection specified - in the dataspace is the portion of the dataset which - will be referred to. - <p> - - <dt><em>hid_t</em> <code>H5Rdereference(</code><em>hid_t</em> <code>dset,</code> - <em>H5R_type_t</em> <code>rtype,</code> - <em>void *</em><code>reference)</code> - <dd><code>H5Rdereference</code> opens the object referenced - and returns an identifier for that object. - The parameter <code>reference</code> specifies a reference of - type <code>rtype</code> that is stored in the dataset - <code>dset</code>. - <p> - - <dt><em>int</em> <code>H5Rget_object_type(</code><em>hid_t</em> <code>obj_id,</code> - <em>void *</em><code>reference)</code> - <dd><code>H5Rget_object_type</code> retrieves the type of object - that an object reference points to. - The parameter <code>obj_id</code> specifies the dataset - containing the reference object or the location identifier - of the object that the dataset is located within. - The parameter <code>reference</code> specifies the - reference being queried. - <p> - - <dt><em>H5S_t</em> <code>H5Rget_region(</code><em>H5D_t</em> <code>dataset,</code> - <em>H5R_type_t</em> <code>type,</code> - <em>void *</em><code>reference)</code> - <dd><code>H5Rget_region</code> creates a copy of dataspace of - the dataset that is pointed to and defines a selection in - the copy which is the location (or region) pointed to. - The parameter <code>ref</code> specifies a reference of - type <code>rtype</code> that is stored in the dataset - <code>dset</code>. - <p> - - <dt><em>H5I_type_t</em> <code>H5Iget_type(</code><em>hid_t</em> <code>id)</code> - <dd>Returns the type of object referred to by the - identifier <code>id</code>. Valid return values appear - in the following list: - <center> - <table> - <tr valign=bottom><td><code>H5I_FILE</code></td> - <td>File objects</td></tr> - <tr valign=bottom><td><code>H5I_GROUP</code></td> - <td>Group objects</td></tr> - <tr valign=bottom><td><code>H5I_DATATYPE</code></td> - <td>Datatype objects</td></tr> - <tr valign=bottom><td><code>H5I_DATASPACE</code></td> - <td>Dataspace objects</td></tr> - <tr valign=bottom><td><code>H5I_DATASET</code></td> - <td>Dataset objects</td></tr> - <tr valign=bottom><td><code>H5I_ATTR</code></td> - <td>Attribute objects</td></tr> - </table> - </center> - <p> - This function was inspired by the need of users to figure - out which type of object closing function - (<code>H5Dclose</code>, <code>H5Gclose</code>, etc.) - to call after a call to <code>H5Rdereference</code>, - but it is also of general use. - <p> -</dl> - - - -<h2>5. Examples</h2> - -<b>Object Reference Writing Example</b> -<br> -Create a dataset which has links to other datasets as part -of its raw data and write the dataset to the file. -<p> - -<pre> -{ - hid_t file1; - hid_t dataset1; - hid_t datatype, dataspace; - char buf[128]; - hobj_ref_t link; - hobj_ref_t data[10][10]; - int rank; - size_t dimsf[2]; - int i, j; - - /* Open the file */ - file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT); - - /* Describe the size of the array and create the data space */ - rank=2; - dimsf[0] = 10; - dimsf[1] = 10; - dataspace = H5Screate_simple(rank, dimsf, NULL); - - /* Define datatype */ - datatype = H5Tcopy(H5T_STD_REF_OBJ); - - /* Create a dataset */ - dataset1=H5Dcreate(file1,"Dataset One",datatype,dataspace,H5P_DEFAULT); - - /* Construct array of OIDs for other datasets in the file */ - /* somewhat hokey and artificial, but demonstrates the point */ - for(i=0; i<10; i++) - for(j=0; j<10; j++) - { - sprintf(buf,"/Group/Linked Set %d-%d",i,j); - if(H5Rcreate(&link,file1,buf,H5R_OBJECT,-1)>0) - data[i][j]=link; - } /* end for */ - - /* Write the data to the dataset using default transfer properties. */ - H5Dwrite(dataset, H5T_STD_REF_OBJ, H5S_ALL, H5S_ALL, H5P_DEFAULT, data); - - /* Close everything */ - H5Sclose(dataspace); - H5Tclose(datatype); - H5Dclose(dataset1); - H5Fclose(file1); -} -</pre> - - -<b>Object Reference Reading Example</b> -<br> -Open a dataset which has links to other datasets as part of -its raw data and read in those links. -<p> - -<pre> -{ - hid_t file1; - hid_t dataset1, tmp_dset; - href_t data[10][10]; - int i, j; - - /* Open the file */ - file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT); - - /* Open the dataset */ - dataset1=H5Dopen(file1,"Dataset One",H5P_DEFAULT); - - /* - * Read the data to the dataset using default transfer properties. - * (we are assuming the dataset is the same and not querying the - * dimensions, etc.) - */ - H5Dread(dataset, H5T_STD_REF_OBJ, H5S_ALL, H5S_ALL, H5P_DEFAULT, data); - - /* Analyze array of OIDs of linked datasets in the file */ - /* somewhat hokey and artificial, but demonstrates the point */ - for(i=0; i<10; i++) - for(j=0; j<10; i++) - { - if((tmp_dset=H5Rdereference(dataset, H5T_STD_REF_OBJ, data[i][j]))>0) - { - <perform operations on linked dataset> - } /* end if */ - H5Dclose(tmp_dset); - } /* end for */ - - - /* Close everything */ - H5Dclose(dataset1); - H5Fclose(file1); -} -</pre> - - -<b>Dataset Region Reference Writing Example</b> -<br> -Create a dataset which has links to other dataset regions -(single elements in this case) as part of its raw data and -write the dataset to the file. -<p> - -<pre> -{ - hid_t file1; - hid_t dataset1, dataset2; - hid_t datatype, dataspace1, dataspace2; - char buf[128]; - href_t link; - href_t data[10][10]; /* HDF5 reference type */ - int rank; - size_t dimsf[2]; - hsize_t start[3],count[3]; - int i, j; - - /* Open the file */ - file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT); - - /* Describe the size of the array and create the data space */ - rank=2; - dimsf[0] = 10; - dimsf[1] = 10; - dataspace1 = H5Screate_simple(rank, dimsf, NULL); - - /* Define Dataset Region Reference datatype */ - datatype = H5Tcopy(H5T_STD_REF_DATAREG); - - /* Create a dataset */ - dataset1=H5Dcreate(file1,"Dataset One",datatype,dataspace1,H5P_DEFAULT); - - /* Construct array of OIDs for other datasets in the file */ - /* (somewhat artificial, but demonstrates the point) */ - for(i=0; i<10; i++) - for(j=0; j<10; i++) - { - sprintf(buf,"/Group/Linked Set %d-%d",i,j); - - /* Get the dataspace for the object to point to */ - dataset2=H5Dopen(file1,buf,H5P_DEFAULT); - dataspace2=H5Dget_space(dataspace2); - - /* Select the region to point to */ - /* (could be different region for each pointer) */ - start[0]=5; start[1]=4; start[2]=3; - count[0]=2; count[1]=4; count[2]=1; - H5Sselect_hyperslab(dataspace2,H5S_SELECT_SET,start,NULL,count,NULL); - - if(H5Rcreate(&link,file1,buf,H5R_REF_DATAREG,dataspace2)>0) - /* Store the reference */ - data[i][j]=link; - - H5Sclose(dataspace2); - H5Dclose(dataspace2); - } /* end for */ - - /* Write the data to the dataset using default transfer properties. */ - H5Dwrite(dataset, H5T_STD_REF_DATAREG, H5S_ALL, H5S_ALL, H5P_DEFAULT, data); - - /* Close everything */ - H5Sclose(dataspace); - H5Tclose(datatype); - H5Dclose(dataset1); - H5Fclose(file1); -} -</pre> - - -<b>Dataset Region Reference Reading Example</b> -<br> -Open a dataset which has links to other datasets regions -(single elements in this case) as part of its raw data and -read in those links. -<p> - -<pre> -{ - hid_t file1; - hid_t dataset1, tmp_dset; - hid_t dataspace; - href_t data[10][10]; /* HDF5 reference type */ - int i, j; - - /* Open the file */ - file1=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT); - - /* Open the dataset */ - dataset1=H5Dopen(file1,"Dataset One",H5P_DEFAULT); - - /* - * Read the data to the dataset using default transfer properties. - * (we are assuming the dataset is the same and not querying the - * dimensions, etc.) - */ - H5Dread(dataset, H5T_STD_REF_DATAREG, H5S_ALL, H5S_ALL, H5P_DEFAULT, data); - - /* Analyze array of OIDs of linked datasets in the file */ - /* (somewhat artificial, but demonstrates the point) */ - for(i=0; i<10; i++) - for(j=0; j<10; i++) - { - if((tmp_dset=H5Rdereference(dataset, H5D_STD_REF_DATAREG,data[i][j]))>0) - { - /* Get the dataspace with the pointed to region selected */ - dataspace=H5Rget_space(data[i][j]); - - <perform operation on linked dataset region> - - H5Sclose(dataspace); - } /* end if */ - H5Dclose(tmp_dset); - } /* end for */ - - - /* Close everything */ - H5Dclose(dataset1); - H5Fclose(file1); -} -</pre> -<!-- - -<h1>Material to Be Omitted!!!</h1> - -Additional material above will also need to be deleted or -commented out. -<p> - -<h2>"Kinds of Reference" Information</h2> - -<dl> - <dt>Dataset Offset Reference - <dd>Reference to a specific byte sequence in a dataset (3) - <dt>Disk Offset Reference - <dd>Reference to a specific byte sequence in a file (3) - <dt>External Object Reference - <dd>Reference to an entire object in another HDF5 file (3) - <dt>External Dataset Region Reference - <dd>Reference an a specific dataset region in another HDF5 file (3) - <dt>External Dataset Offset Reference - <dd>Reference to a specific byte sequence in a dataset in - another HDF5 file (3) - <dt>External Disk Offset Reference - <dd>Reference to a specific byte sequence in another HDF5 file (3) - <dt>Generic Reference - <dd>A reference which may be any of the types defined above. (3) -</dl> - -Notes: -<ul> - <li>1 - Planned for in final release. - <li>2 - Most useful reference types to tackle next - <li>3 - Optional reference types. -</ul> - -<h2>Comments</h2> -<pre> - Reference types are atomic types and may be included as fields in compound - datatypes. - - There are (at least) three levels of reference strength: - Weak - We allow the user to store any type of reference in an array - of references. (u.e., the array of references in the example above - could be a mix of Object, Dataset Region and Internal references) - Medium - We force the user to stick with a particular type of - reference within a dataset, but the datasets pointed to (with - Object and Dataset Region references) may be of any datatype - or dataspace. - Strong - We force the user to stick with a particular type of - reference and Object and Dataset Region references must point to - datasets with the same datatype. - Extra Strong - We force the user to stick with a particular type of - reference and Object and Dataset Region references must point to - datasets with the same datatype <i>and</i> dataspace. - - The library is currently implemented with "medium" strength references. -</pre> - - -<h2>Reference Type</h2> - -<center> -<table> -<tr><td><code>H5R_MAXTYPE</code></td> - <td align=right><code>3 </code></td> - <td>Highest type in group (invalid as true type)</td></tr> -</table> -</center> - - -<h2>Information Regarding Specific Kinds of References</h2> - -<dl> -<dt>Dataset Offset Reference - <dd>Points to a sequence of bytes within a dataset in - the current HDF5 file by storing the OID of the dataset and the byte - length and offset of the sequence within the dataset. The offset is - the logical byte offset within the dataset, meaning that the data is - de-compressed before returning the sequence of bytes requested. No - interpretation of the data at that location is provided. However, - if the dataset is extendible and the size of the dimensions are changed, - the element(s) that the sequence is located within may vary. Fixed size - in file. - -<dt>Disk Offset Reference - <dd>Points to a sequence of bytes in the current - HDF5 file by storing the byte length and offset of the sequence within - the file, relative to the super block (as are all the other high-level - addresses used in the file). The offset is the absolute byte offset - within the file, no interpretation of the data at that location is - provided. Fixed size in file. - -<dt>External Object Reference - <dd>Points to an entire object in another HDF5 file by - storing a global heap offset which points to the URL of the external - file and the OID of the object pointed to. Variable size in file. - -<dt>External Dataset Region Reference - <dd>Points to a region of a dataset in - another HDF5 file by storing a global heap offset which points to the - URL of the external file, OID of the dataset and the coordinates of the - region. Variable size in file. - -<dt>External Dataset Offset Reference - <dd>Points to a sequence of bytes within a - dataset in another HDF5 file by storing a global heap offset which - points to the URL of the external file, the OID of the dataset and the - byte length and offset of the sequence within the dataset. The offset - is the logical byte offset within the dataset, meaning that the data is - de-compressed before returning the sequence of bytes requested. - However, if the dataset is not stored contiguously and the size of the - dimensions are changed, the element(s) that the sequence is located - within may vary. Variable size in file. - -<dt>External Disk Offset Reference - <dd>Points to a sequence of bytes in another - HDF5 file by storing a global heap reference which points to the URL - of the external file and the byte length and offset of the sequence - within the file. The offset is the absolute byte offset within the - file, no interpretation of the data at that location is provided. - Variable size in file. - -<dt>Generic Reference - <dd>A reference which may contain any of the other - references defined above. (Mostly useful for implementing "weak" - strength pointers within the medium strength model we are using) - Variable size in file. - -</dl> - -<h2>Implementation Details</h2> - -<dl> -<dt>File Storage - <dd>In order to efficiently index an array, each element must be the - same size when stored in the dataset on disk. Fixed-sized references - will be stored directly in the dataset array on disk; variable-sized - references will have a fixed-size head offset stored in the array on - disk with a file heap used to store the actual variable-sized - information stored in the heap. - -<dt>Memory Storage - <dd>Each <code>href_t</code> object in memory is a struct containing - a pointer type and union of information required for each - pointer type. - Information in this structure is not designed for users to view. - Non-C APIs may have to mangle this structure in some way, in order - to provide users with access to references in a language-appropriate - way. -</dl> - ---> - - -<!-- #BeginLibraryItem "/ed_libs/NavBar_UG.lbi" --><hr> -<center> -<table border=0 width=98%> -<tr><td valign=top align=left> - <a href="index.html">HDF5 documents and links</a> <br> - <a href="H5.intro.html">Introduction to HDF5</a> <br> - <a href="RM_H5Front.html">HDF5 Reference Manual</a> <br> - <a href="http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html">HDF5 User's Guide for Release 1.6</a> <br> - <!-- - <a href="Glossary.html">Glossary</a><br> - --> -</td> -<td valign=top align=right> - And in this document, the - <a href="H5.user.html"><strong>HDF5 User's Guide from Release 1.4.5:</strong></a> - <br> - <a href="Files.html">Files</a> - <a href="Datasets.html">Datasets</a> - <a href="Datatypes.html">Datatypes</a> - <a href="Dataspaces.html">Dataspaces</a> - <a href="Groups.html">Groups</a> - <br> - <a href="References.html">References</a> - <a href="Attributes.html">Attributes</a> - <a href="Properties.html">Property Lists</a> - <a href="Errors.html">Error Handling</a> - <br> - <a href="Filters.html">Filters</a> - <a href="Caching.html">Caching</a> - <a href="Chunking.html">Chunking</a> - <a href="MountingFiles.html">Mounting Files</a> - <br> - <a href="Performance.html">Performance</a> - <a href="Debugging.html">Debugging</a> - <a href="Environment.html">Environment</a> - <a href="ddl.html">DDL</a> -</td></tr> -</table> -</center> -<hr> -<!-- #EndLibraryItem --><!-- #BeginLibraryItem "/ed_libs/Footer.lbi" --><address> -<a href="mailto:hdfhelp@ncsa.uiuc.edu">HDF Help Desk</a> -<br> -Describes HDF5 Release 1.4.5, February 2003 -</address><!-- #EndLibraryItem --> - -Last modified: 2 August 2004 - -</body> -</html> |