Examples of org.jnode.shell.syntax.MuParser$ChoicePoint

org.jnode.shell.syntax.MuParser
This class implements parsing of a token stream against a MuSyntax graph. The parser binds token values against Argument instances as it goes, and does full backtracking when it reaches a point where it cannot make forward progress. The backtracking mechanism manages the parser state and also records the Arguments that have been 'set', and therefore need to be 'unset' when we backtrack.
When we are doing a normal parse, the various alternatives in the MuSyntax graph are explored until either there is a successful parse (consuming all tokens), or we run out of alternatives. The latter case results in an exception and a failed parse.
When we are doing a completion parse, all alternatives are explored irrespective of parse success.
A MuSyntax may contain "infinite" loops, or other pathologies that trigger excessive backtracking. To avoid problems, the 'parse' method takes a 'stepLimit' parameter that causes the parse to fail if it has not terminated soon enough.
The MuParser uses the SharedStack class to record syntax stacks for backtracking. This is a special purpose Deque that avoids unnecessary copying of the stack state. If you suspect that this is causing problems, replace {@code new SharedStack(...)}with {@code new LinkedList(...)}. @author crawley@jnode.org

    public void testStatelessParsing5() throws NoTokensAvailableException, CommandSyntaxException {
        // <root> ::= ( 'a' <root> ) | 'b'
        MuSyntax syntax =
                new MuAlternation("root", new MuSequence(new MuSymbol("a"), new MuBackReference(
                        "root")), new MuSymbol("b"));
        MuParser parser = new MuParser();
        CommandLine cl;


        syntax.resolveBackReferences();


        cl = new CommandLine(new String[] {"b"});


        parser.parse(syntax, null, cl.tokenIterator(), null);


        syntax.resolveBackReferences();
        cl = new CommandLine(new String[] {"a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        cl = new CommandLine(new String[] {"a", "a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        try {
            cl = new CommandLine(new String[] {"a", "a", "c"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("expected SEE");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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        // <root> ::= ( ( 'a' <root> ) | ( 'b' 'c' ) ) | ( ( 'a' <root> ) | 'b'
        // ) )
        MuSyntax syntax = new MuAlternation("root", new MuAlternation(new MuSequence(new MuSymbol("a"),
            new MuBackReference("root")), new MuSequence(new MuSymbol("b"), new MuSymbol("c"))),
            new MuAlternation(new MuSequence(new MuSymbol("a"), new MuBackReference("root")), new MuSymbol("b")));
        MuParser parser = new MuParser();
        CommandLine cl;


        syntax.resolveBackReferences();


        cl = new CommandLine(new String[] {"b"});


        parser.parse(syntax, null, cl.tokenIterator(), null);


        syntax.resolveBackReferences();
        cl = new CommandLine(new String[] {"a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        cl = new CommandLine(new String[] {"a", "a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        cl = new CommandLine(new String[] {"a", "a", "b", "c"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        try {
            cl = new CommandLine(new String[] {"a", "a", "c"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("expected SEE");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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        // Pathological grammar.
        // <root> ::= 'b' | ( <root> <root> )
        MuSyntax syntax =
                new MuAlternation("root", new MuSymbol("b"), new MuSequence(new MuBackReference(
                        "root"), new MuBackReference("root")));
        MuParser parser = new MuParser();
        CommandLine cl;


        syntax.resolveBackReferences();


        // This doesn't hit the infinite loop ...
        cl = new CommandLine(new String[] {"b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        // But this does ...
        cl = new CommandLine(new String[] {"a"});
        try {
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("expected SFE");
        } catch (SyntaxFailureException ex) {
            Assert.assertEquals(
                    "Parse exceeded the step limit (" + MuParser.DEFAULT_STEP_LIMIT + "). " +
                            "Either the command line is too large, or the syntax is too complex (or pathological)",

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@SuppressWarnings("deprecation")
public class MuParserTest {


    @Test
    public void testInstantiation() {
        new MuParser();
    }

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    @Test
    public void testStatelessParsing1() throws NoTokensAvailableException, CommandSyntaxException {
        // <start> ::= 'a'
        MuSyntax syntax = new MuSymbol("a");
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"a"});


        parser.parse(syntax, null, cl.tokenIterator(), null);


        try {
            cl = new CommandLine(new String[] {"b"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }


        try {
            cl = new CommandLine(new String[] {"a", "a"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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    @Test
    public void testStatelessParsing2() throws NoTokensAvailableException, CommandSyntaxException {
        // <start> ::= 'a' 'b'
        MuSyntax syntax = new MuSequence(new MuSymbol("a"), new MuSymbol("b"));
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);
        try {
            cl = new CommandLine(new String[] {"a"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }
        try {
            cl = new CommandLine(new String[] {"a"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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    @Test
    public void testStatelessParsing3() throws NoTokensAvailableException, CommandSyntaxException {
        // <start> :: = 'a' | 'b'
        MuSyntax syntax = new MuAlternation(new MuSymbol("a"), new MuSymbol("b"));
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"a"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        cl = new CommandLine(new String[] {"b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        try {
            cl = new CommandLine(new String[] {"c"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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    public void testStatelessParsing4() throws NoTokensAvailableException, CommandSyntaxException {
        // <root> ::= 'b' | ( 'a' <root> )
        MuSyntax syntax =
                new MuAlternation("root", new MuSymbol("b"), new MuSequence(new MuSymbol("a"),
                        new MuBackReference("root")));
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"b"});


        parser.parse(syntax, null, cl.tokenIterator(), null);


        try {
            cl = new CommandLine(new String[] {"a", "b"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("expected SFE");
        } catch (SyntaxFailureException ex) {
            // expected
        }


        syntax.resolveBackReferences();
        cl = new CommandLine(new String[] {"a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        cl = new CommandLine(new String[] {"a", "a", "b"});
        parser.parse(syntax, null, cl.tokenIterator(), null);


        try {
            cl = new CommandLine(new String[] {"a", "a", "c"});
            parser.parse(syntax, null, cl.tokenIterator(), null);
            Assert.fail("expected SEE");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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        IntegerArgument intArg = new IntegerArgument("intArg", Argument.MULTIPLE);
        ArgumentBundle bundle = new ArgumentBundle(intArg);


        // <start> ::= <<intArg>>
        MuSyntax syntax = new MuArgument("intArg");
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"1"});


        parser.parse(syntax, null, cl.tokenIterator(), bundle);
        Assert.assertEquals(new Integer(1), intArg.getValue());


        try {
            cl = new CommandLine(new String[] {"X"});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }


        try {
            cl = new CommandLine(new String[] {"1", "1"});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }
    }

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        FileArgument fileArg = new FileArgument("fileArg", Argument.MULTIPLE);
        ArgumentBundle bundle = new ArgumentBundle(intArg, fileArg);


        // <start> ::= <<intArg>> <<fileArg>>
        MuSyntax syntax = new MuSequence(new MuArgument("intArg"), new MuArgument("fileArg"));
        MuParser parser = new MuParser();
        CommandLine cl;


        cl = new CommandLine(new String[] {"1", "x"});
        parser.parse(syntax, null, cl.tokenIterator(), bundle);


        Assert.assertEquals(new Integer(1), intArg.getValue());
        Assert.assertEquals(new File("x"), fileArg.getValue());


        try {
            cl = new CommandLine(new String[] {"1"});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }
        try {
            cl = new CommandLine(new String[] {"1", ""});
            parser.parse(syntax, null, cl.tokenIterator(), bundle);
            Assert.fail("parse didn't fail");
        } catch (CommandSyntaxException ex) {
            // expected
        }

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Related Classes of org.jnode.shell.syntax.MuParser$ChoicePoint

org.jnode.shell.syntax.CommandSyntaxException.Context

org.jnode.test.shell.syntax.MuParserTest

org.jnode.test.shell.syntax.MuParserTest2

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