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3. AN APPLICATION RECONFIGURATION FRAMEWORK 3.3. Original to Generic syntax Converter
Listing 3.2: Configuration File Parser proposed interface
interface CFP {
Map doParse(String fileName);
ParsingData doParse(String fileName, Parser parser);
}
Repository. Then, the user can fetch the previsouly built grammars through the
getTentativeGrammar call.
The parsers generated by the Grammar Compiler must be validated by the user to check
if the new parser is able to parse the configuration file, or if the generic syntax produced by the
parser is indeed the desired one. UI must handle this information and show it to the user in
a user-friendly optic (e.g., graphically). Then, if the user approves the parser, he can summon
the approveParser method to store the parser with the remaining parsers in the Parser
Repository. Finally, UI stores the generic syntax in memory on a file.
Besides the presented basic functionality, UI offers some more utilities to the user. Namely,
the importParser method allows the importation of external parsers if the user is already
in possession of a functional parser for a new configuration file. Additionally, the user may
suspend the tool’s execution and resume it later through the haltSession method. This
method stores the tentative grammars to disk, as well as other volatile data in memory, such as
the produced file in generic syntax, if it was already produced. The recoverSession method
obtains all the stored data to resume a previously saved session.
Configuration File Parser
The Configuration File Parser (CFP, Listing 3.2) can either parse a configuration file with every
parser in the database or just with a single one. The parsers analyse the configuration files in
their original syntax, declared in a grammar which defines the tokens and productions of that
syntax, and produce the abstract syntax tree (AST) of the file.
The ASTs generated by the parsers must follow the typing indicated in Section 1.3. There-
fore, nodes composing an AST are either parameters, blocks, comments or nodes corresponding
to new patterns. By assuring that the ASTs are typed in such a way, it is possible to conceive a
uniform Code Generator, which is able to traverse the AST of any application. Furthermore,
strictly typed ASTs guarantee that the generic syntax is constant for every application. In other
words, the generic syntax will be composed of elements like parameters, blocks, comments and
specials, which is a standard recognized by the file modification agent.
CFP may iterate the available parsers in the Parser Repository and attempt to parse
the input file with each one of them. Alternatively, CFP may also be called to parse a file with a
newly generated parser if the file was not entirely recognized with any of the existing parsers.
When a parser is tested, it returns the configuration file intervals which were recognized,
along with the AST of each interval. The ASTs are sent to the Code Generator to be con-
verted into generic syntax, in order to help the user analyse and validate the output produced
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