diff options
Diffstat (limited to 'orbsvcs/PSS/README')
| -rw-r--r-- | orbsvcs/PSS/README | 261 |
1 files changed, 0 insertions, 261 deletions
diff --git a/orbsvcs/PSS/README b/orbsvcs/PSS/README deleted file mode 100644 index 106a07c5dd5..00000000000 --- a/orbsvcs/PSS/README +++ /dev/null @@ -1,261 +0,0 @@ - - Persistence State Service - ------------------------- - - The Persistent State Service (PSS) provides a standard way to -persistently save the state of objects in a datastore. A datastore is -an entity that manages data like a database or a set of files. For -TAO's implementation of PSS, the datastore is a normal file, for now. - - The PSS defines two ways to define the datastore schema and -the interfaces to the storage object instances in the datastore. One -way is to use the Persistent State Definition Language (PSDL). PSDL -language is a superset to the IDL language and introduces four new -constructs: storagehome, storagetype, abstract storagehome and -abstract storagetype. A PSDL file (which is similar to an IDL file) -contain the definitions which describe the interface to the -datastore. This psdl interface and the datastore is visible only to -the server which saves the state of objects. The clients to this -server do not idea about how the server saves the state of the -objects and hence have no idea about the psdl interface or the -datastore. - - The PSS implementation provides a compiler tool to process -the psdl file and generates stubs (I will use the name 'stub' just for -the lack of any other name.. though this stub is not the same as the -normal stub that is generated by the IDL compiler). - - PSDL Compiler - ============= - - TAO's implementation of the PSS provides psdl_tao as the -compiler to - -Design -====== - - The Input file (of format pidl) is first parsed with the -yacc-lex parser. The TAO_PSDL_Interpreter has a method (build_tree) -which helps construct an expression tree representing nodes from the -tokens returned by the Yacc generated parser. In addition, based on -the grammar set in PSDL.yy, any syntax errors are checked by the yacc -parser. Using the '-b' (build-tree) option, you can print out the -generated parse-tree for debugging purposes. All the classes in -PSDL_Node help build the parse tree. -(@@ To-do: I should be adding an option to the executable so that the -parse tree can be printed out when the option is set.) - - Along with the basic parsing, we build the symbol -table. The TAO_PSDL_Scope class is the base class which helps add each -type (like interface, exceptions etc) to the symbol table. - - The symbol table is constructed using the ACE hash maps. -We use two kinds of hash-maps...one maps the identifier to a -structure (Node_Info) which has information about the identifier -(identifier_type, module_name & interface_name (module and interfaces -to which this identifier belongs). This is used in cases where in the -identifier doesnt have some members in itself.. constant declarations, -typedefs, exceptions with no members etc. - - Unlike a simple declaration or a typedef, types like -interfaces have member declarations which come with their scope. For -example, an interface has its own set of declarations, methods, -interfaces etc. For such types, we will have a class derived from -base TAO_PDSL_Scope. [In the case of interfaces, it is -TAO_PSDL_Interface_Scope.] The second hash map is to -map the identifier and the instance of the identifier's -type... i.e. say the identifier is of type interface, this hash-map -has a mapping between the identifier and the pointer to the instance -of TAO_PSDL_Interface_Scope. [All the TAO_PSDL_*_Scope classes fall in -this category.] - - In this phase, along with building the symbol table, we also -do the semantic checking. Semantic checking includes checking if an -identifier that is declared before is now being redeclared. -Identifiers are case-sensitive and case-insensitive too... -ie. for ex: You cannot have CosNaming and cosnaming. - - After the symbol tables are built, the next step is to -generate code in to the stubs. The classes TAO_PSDL_*_Visitor generates -this code. TAO_PSDL_Node_Visitor is the base class and the derived -classes override the necessary methods. So, if you want to generate -for some other type in future, we need to have another of -TAO_PSDL_*_Visitor class and override the necessary virtual method. - - -Implementation files of the stubs (idlC.cpp) -================================= - - The generation of the header and implementation files -for the stubs can be done in a single pass. The implementation files -mainly involves the '<<' and '>>' operator support. These operators -support will be mainly useful while marshalling and demarshalling the -data types. - - - - -Status in a summary. -======= - -1. Can parse any psdl file. -2. Does syntax checking. -3. Can build parse tree for most but not all of the types. -4. Builds ASTs for the basic types which includes typedefs, - interfaces, structs, modules, exceptions, constant declarations. -5. Generate the code that goes into the header file for the same types - listed above. - - -Files and Description -===================== - -PSDL.yy Yacc file which has the PSDL grammar. - -PSDL_y.cpp -PSDL_y.h Yacc generated files. - -PSDL_l.cpp Lex generated file. - -PSDL_Node.h -PSDL_Node.cpp Each node in the parse tree is derived from - the base type TAO_PSDL_Node. The classes in - this file provide the interface for the - different types. Each class will have accessor - methods to access the private members and an - accept method to invoke the corresponding - visitor method. (We are applying the visitor - pattern here.) - - -PSDL_Scope.h -PSDL_Scope.cpp -PSDL_*_Scope.* The classes in these files are useful for - building the AST. TAO_PSDL_Scope is the base - class and there are classes for each type - (which has members in it, ex: interface) - which needs to be added to the AST which - derive from TAO_PSDL_Scope. - -PSDL_Node_Visitor.h -PSDL_Node_Visitor.cpp -PSDL_*_Visitor.* TAO_PSDL_Node_Visitor acts as a base class - useful for generating code into - stubs. TAO_PDSL_Node_Visitor derives from - TAO_PSDL_Scope_Visitor. The sub-classes (for - the different types) which - need to override the basic functionality of - the visitor methods in TAO_PSDL_Node_Visitor - derive from it and override accordingly. The -derived classes methods are invoked from the base class as needed -making use of the factory pattern (TAO_PSDL_Visitor_Factory). - - -To-Do -==== - -1. The visitor classes should generate the code into a file and not to - stdout as I am doing now. - -2. Support for comments , pragmas etc. Right now, if you have - comments or pragmas, its going to fail. - -Test -==== - -% ./psdl_tao < trial_idl.idl - - -Things to do -============ - - -1. Have a test to include all the existing types. Should check the - generated code and check if it is the right thing. - 2 days - -2. Work on the stubs. - . Redirect the output to a file rather than to stdout. - . Work on the implementation files (*C.cpp). This will be based on - ACE Reliable Multicast framework. - ps: Bala told last friday that ACE Reliable Multicast Framework - has several bugs. So, this might end up taking longer. FYI, - - - 2 weeks. - -3. Have a test/example for the total framework. 1 week- 10 days - - - Have an application which is going to use the PSS framework.. have a server etc. - -4. Additional Documentation as needed including - . Steps for modifying the existing services to use PSS. 1 week. - - -5. Include support for all the types in PSDL language in all the - stages which includes mainly - . Building the parse tree - . While building ASTs - . Generating the stubs. - -6. Extend the tests to include all the new types. - - - -IMR -=== - -1. Test - -2. Documentation abt the differences between old and new IMR. -3. How to update/migrate to the new IMR. - -4. Code review. 2 days -5. modift 2 days. - - -MInor things -============ - -1. Print out the Caps of the names - -#if !defined (_TRIAL_INTERFACE___PTR_CH_) - -instead of - -#if !defined (__trial_interface___PTR_CH_) - - -2. Check out TAO_NAMESPACE_STORAGE_CLASS and static nad extern storage classes before _tc_* - - -Notes on how to proceed -======================= - -1. Serialize the data using TAO_OutputCDR. - -The implementation files should have the '<<' and '>>' methods. - -2. There needs to be another executable or library which would be -actually saving the state of objects to the database. Since RMCast is -not working right now, we can save the data to a file and retrieve -from it. - - -Example -======= - -1. Have a mini naming idl which just has the bind and find functions - support. - - There can be just a server.cpp which will bind information. - -2. Have a psdl interface which has a - - sequence of struct (name, - stringified_ior). - - When a bind is done, it has to be going through the helper -classes and inserted into a hash_map and saved to the file. And when -find is invoked, it has to be read from the file and demarshalled. - - - |