1 mike  1.1 //%/////////////////////////////////////////////////////////////////////////////
  2           //

  3 kumpf 1.3 // Copyright (c) 2000, 2001, 2002 BMC Software, Hewlett-Packard Company, IBM,

  4 mike  1.1 // The Open Group, Tivoli Systems
  5           //
  6           // Permission is hereby granted, free of charge, to any person obtaining a copy
  7           // of this software and associated documentation files (the "Software"), to
  8           // deal in the Software without restriction, including without limitation the
  9           // rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 10           // sell copies of the Software, and to permit persons to whom the Software is
 11           // furnished to do so, subject to the following conditions:

 12 kumpf 1.3 // 

 13 mike  1.1 // THE ABOVE COPYRIGHT NOTICE AND THIS PERMISSION NOTICE SHALL BE INCLUDED IN
 14           // ALL COPIES OR SUBSTANTIAL PORTIONS OF THE SOFTWARE. THE SOFTWARE IS PROVIDED
 15           // "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
 16           // LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 17           // PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 18           // HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
 19           // ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
 20           // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 21           //
 22           //==============================================================================
 23           //
 24           // Author: Jenny Yu, Hewlett-Packard Company (jenny_yu@hp.com)
 25           //
 26           // Modified By: Michael E. Brasher (mbrasher@bmc.com)
 27           //
 28           //%/////////////////////////////////////////////////////////////////////////////
 29           
 30           #ifndef Pegasus_InstanceDataFile_h
 31           #define Pegasus_InstanceDataFile_h
 32           
 33           #include <fstream>
 34 mike  1.1 #include <Pegasus/Common/Config.h>
 35           #include <Pegasus/Common/String.h>
 36           #include <Pegasus/Common/Exception.h>

 37 kumpf 1.2 #include <Pegasus/Common/CIMObjectPath.h>

 38 mike  1.1 
 39           PEGASUS_NAMESPACE_BEGIN
 40           
 41           /** This class manages access to an instance data file which contains all
 42               instances of a particular class.
 43           
 44               The instances are stored in ASCII XML format one after another. A separate
 45               instance index file is maintained (see InstanceIndexFile) which contains
 46               an index entry for each instance in the data file. This index ties the key
 47               of the instance to an offset and size within the instance file.
 48           
 49               The index file and data file are named according to the class whose
 50               instances they contain information about. The index file and data file for
 51               a class named "Zebra" would be:
 52           
 53               <pre>
 54                   Zebra (index file).
 55                   Zebra.instances (instance-file).
 56               </pre>
 57             
 58               When an instance is created, it is appended to the end of the instance 
 59 mike  1.1     file. When one is deleted, it is marked as free in the index file. When
 60               an instance is modified, the old one is marked as deleted and the new
 61               modified instance is appended to the end of the data file. Note that 
 62               deletion and modification may leave unused gaps in the data file. These
 63               gaps are reclaimed during compaction (performed when the data file has
 64               N gaps where N is some arbitrarily chosen number for now). Performing
 65               compaction during each modify and delete would be extremely inefficient.
 66               By postponing it until N such operations have been performed, we 
 67               improve performance considerably.
 68           
 69               Note the three operations which may be performed on an instance and there
 70               associated effect on the data file.
 71           
 72               <ul>
 73               <li>Create - appends an instance to the end of the file.</li>
 74               <li>Modify - appends an instance to the end of the file.</li>
 75               <li>Delete - has no effect on the data file</li>
 76               </ul>
 77           
 78               To avoid corruption of the data file we provide a rollback scheme. A
 79               rollback file is created (the name is formed by appending ".rollback" to
 80 mike  1.1     the name of the data file) which contains the original size of the data
 81               file. After the modification of the data file is complete, the rollback
 82               file is removed. If we discover a rollback file when we start an operation,
 83               this means that the last operation did not succeed. We then rollback the
 84               operation by truncating the file to its old size.
 85           */
 86           class PEGASUS_REPOSITORY_LINKAGE InstanceDataFile
 87           {
 88           public:
 89               
 90               /** loads an instance from the data file into memory.
 91           
 92                   @param path the file path of the instance file
 93                   @param index the byte positon of the instance record
 94                   @param size the size of the instance record 
 95                   @param data the buffer to hold the instance data 
 96                   @return true on success.
 97               */
 98               static Boolean loadInstance(
 99           	const String& path, 
100           	Uint32 index,
101 mike  1.1 	Uint32 size,  
102                   Array<Sint8>& data);
103               
104               /** loads all the instances from the data file into memory. 
105           
106                   @param path the file path of the instance file
107                   @param data the buffer to hold the data 
108                   @return true on success.
109               */
110               static Boolean loadAllInstances(
111           	const String& path, 
112                   Array<Sint8>& data);
113               
114               /** Appends a new instance to the end of the file.
115                
116                   @param out the buffer containing the CIM/XML encoding of the 
117                   @param path the file path of the instance file
118                   @param index the byte positon of the instance record
119                   @return true on success
120               */
121               static Boolean appendInstance(
122 mike  1.1 	const String& path, 
123                   const Array<Sint8>& data,
124           	Uint32& index);
125           
126               /** Begin a transaction to modify this file. The effect of subsequent
127           	modifications can be rolled back by calling rollbackTransaction().
128               */
129               static Boolean beginTransaction(const String& path);
130           
131               /** Roll back any changes to the file since the last time 
132                   beginTransaction() was called.
133               */
134               static Boolean rollbackTransaction(const String& path);
135           
136               /** Commit changes made after beginTransaction() was called.
137               */
138               static Boolean commitTransaction(const String& path);
139           
140               /** Reorganizes the data file to reclaim free space. This is done by
141           	copying over all non-free instances to a temporary file and then
142           	deleting the original file and renaming the temporary file to the
143 mike  1.1 	same name as the original.
144               */
145               static Boolean compact(
146           	const String& path,
147                   const Array<Uint32>& freeFlags,
148                   const Array<Uint32>& indices,
149                   const Array<Uint32>& sizes);
150           
151           private:
152           
153               static Boolean _openFile(
154           	PEGASUS_STD(fstream)& fs,
155           	const String& path,
156           	int mode);
157           };
158           
159           PEGASUS_NAMESPACE_END
160           
161           #endif /* Pegasus_InstanceDataFile_h */