Class CodeGenerator

java.lang.Object
org.antlr.codegen.CodeGenerator

public class CodeGenerator extends Object
ANTLR's code generator. Generate recognizers derived from grammars. Language independence achieved through the use of STGroup objects. All output strings are completely encapsulated in the group files such as Java.stg. Some computations are done that are unused by a particular language. This generator just computes and sets the values into the templates; the templates are free to use or not use the information. To make a new code generation target, define X.stg for language X by copying from existing Y.stg most closely releated to your language; e.g., to do CSharp.stg copy Java.stg. The template group file has a bunch of templates that are needed by the code generator. You can add a new target w/o even recompiling ANTLR itself. The language=X option in a grammar file dictates which templates get loaded/used. Some language like C need both parser files and header files. Java needs to have a separate file for the cyclic DFA as ANTLR generates bytecodes directly (which cannot be in the generated parser Java file). To facilitate this, cyclic can be in same file, but header, output must be searpate. recognizer is in outptufile.
  • Field Details

    • MSCL_DEFAULT

      public static final int MSCL_DEFAULT
      When generating SWITCH statements, some targets might need to limit the size (based upon the number of case labels). Generally, this limit will be hit only for lexers where wildcard in a UNICODE vocabulary environment would generate a SWITCH with 65000 labels.
      See Also:
    • MAX_SWITCH_CASE_LABELS

      public static int MAX_SWITCH_CASE_LABELS
    • MSA_DEFAULT

      public static final int MSA_DEFAULT
      See Also:
    • MIN_SWITCH_ALTS

      public static int MIN_SWITCH_ALTS
    • GENERATE_SWITCHES_WHEN_POSSIBLE

      public boolean GENERATE_SWITCHES_WHEN_POSSIBLE
    • LAUNCH_ST_INSPECTOR

      public static boolean LAUNCH_ST_INSPECTOR
    • MADSI_DEFAULT

      public static final int MADSI_DEFAULT
      See Also:
    • MAX_ACYCLIC_DFA_STATES_INLINE

      public static int MAX_ACYCLIC_DFA_STATES_INLINE
    • classpathTemplateRootDirectoryName

      public static String classpathTemplateRootDirectoryName
    • grammar

      public Grammar grammar
      Which grammar are we generating code for? Each generator is attached to a specific grammar.
    • language

      protected String language
      What language are we generating?
    • target

      public Target target
      The target specifies how to write out files and do other language specific actions.
    • templates

      protected org.stringtemplate.v4.STGroup templates
      Where are the templates this generator should use to generate code?
    • baseTemplates

      protected org.stringtemplate.v4.STGroup baseTemplates
      The basic output templates without AST or templates stuff; this will be the templates loaded for the language such as Java.stg *and* the Dbg stuff if turned on. This is used for generating syntactic predicates.
    • recognizerST

      protected org.stringtemplate.v4.ST recognizerST
    • outputFileST

      protected org.stringtemplate.v4.ST outputFileST
    • headerFileST

      protected org.stringtemplate.v4.ST headerFileST
    • uniqueLabelNumber

      protected int uniqueLabelNumber
      Used to create unique labels
    • tool

      protected Tool tool
      A reference to the ANTLR tool so we can learn about output directories and such.
    • debug

      protected boolean debug
      Generate debugging event method calls
    • trace

      protected boolean trace
      Create a Tracer object and make the recognizer invoke this.
    • profile

      protected boolean profile
      Track runtime parsing information about decisions etc... This requires the debugging event mechanism to work.
    • lineWidth

      protected int lineWidth
    • acyclicDFAGenerator

      public ACyclicDFACodeGenerator acyclicDFAGenerator
      I have factored out the generation of acyclic DFAs to separate class
    • VOCAB_FILE_EXTENSION

      public static final String VOCAB_FILE_EXTENSION
      I have factored out the generation of cyclic DFAs to separate class
      See Also:
    • vocabFilePattern

      protected static final String vocabFilePattern
      See Also:
  • Constructor Details

    • CodeGenerator

      public CodeGenerator(Tool tool, Grammar grammar, String language)
  • Method Details

    • loadLanguageTarget

      public static Target loadLanguageTarget(String language)
    • loadTemplates

      public void loadTemplates(String language)
      load the main language.stg template group file
    • genRecognizer

      public org.stringtemplate.v4.ST genRecognizer()
      Given the grammar to which we are attached, walk the AST associated with that grammar to create NFAs. Then create the DFAs for all decision points in the grammar by converting the NFAs to DFAs. Finally, walk the AST again to generate code. Either 1 or 2 files are written: recognizer: the main parser/lexer/treewalker item header file: language like C/C++ need extern definitions The target, such as JavaTarget, dictates which files get written.
    • verifyActionScopesOkForTarget

      protected void verifyActionScopesOkForTarget(Map<String,Map<String,Object>> actions)
      Some targets will have some extra scopes like C++ may have '@headerfile:name {action}' or something. Make sure the target likes the scopes in action table.
    • translateActionAttributeReferences

      protected void translateActionAttributeReferences(Map<String,Map<String,Object>> actions)
      Actions may reference $x::y attributes, call translateAction on each action and replace that action in the Map.
    • translateActionAttributeReferencesForSingleScope

      public void translateActionAttributeReferencesForSingleScope(Rule r, Map<String,Object> scopeActions)
      Use for translating rule @init{...} actions that have no scope
    • generateLocalFOLLOW

      public void generateLocalFOLLOW(GrammarAST referencedElementNode, String referencedElementName, String enclosingRuleName, int elementIndex)
      Error recovery in ANTLR recognizers. Based upon original ideas: Algorithms + Data Structures = Programs by Niklaus Wirth and A note on error recovery in recursive descent parsers: http://portal.acm.org/citation.cfm?id=947902.947905 Later, Josef Grosch had some good ideas: Efficient and Comfortable Error Recovery in Recursive Descent Parsers: ftp://www.cocolab.com/products/cocktail/doca4.ps/ell.ps.zip Like Grosch I implemented local FOLLOW sets that are combined at run-time upon error to avoid parsing overhead.
    • genLookaheadDecision

      public org.stringtemplate.v4.ST genLookaheadDecision(org.stringtemplate.v4.ST recognizerST, DFA dfa)
      Generate code that computes the predicted alt given a DFA. The recognizerST can be either the main generated recognizerTemplate for storage in the main parser file or a separate file. It's up to the code that ultimately invokes the codegen.g grammar rule. Regardless, the output file and header file get a copy of the DFAs.
    • generateSpecialState

      public org.stringtemplate.v4.ST generateSpecialState(DFAState s)
      A special state is huge (too big for state tables) or has a predicated edge. Generate a simple if-then-else. Cannot be an accept state as they have no emanating edges. Don't worry about switch vs if-then-else because if you get here, the state is super complicated and needs an if-then-else. This is used by the new DFA scheme created June 2006.
    • genLabelExpr

      protected org.stringtemplate.v4.ST genLabelExpr(org.stringtemplate.v4.STGroup templates, Transition edge, int k)
      Generate an expression for traversing an edge.
    • genSemanticPredicateExpr

      protected org.stringtemplate.v4.ST genSemanticPredicateExpr(org.stringtemplate.v4.STGroup templates, Transition edge)
    • genSetExpr

      public org.stringtemplate.v4.ST genSetExpr(org.stringtemplate.v4.STGroup templates, IntSet set, int k, boolean partOfDFA)
      For intervals such as [3..3, 30..35], generate an expression that tests the lookahead similar to LA(1)==3 || (LA(1)>=30&&LA(1)<=35)
    • genTokenTypeConstants

      protected void genTokenTypeConstants(org.stringtemplate.v4.ST code)
      Set attributes tokens and literals attributes in the incoming code template. This is not the token vocab interchange file, but rather a list of token type ID needed by the recognizer.
    • genTokenTypeNames

      protected void genTokenTypeNames(org.stringtemplate.v4.ST code)
      Generate a token names table that maps token type to a printable name: either the label like INT or the literal like "begin".
    • getTokenTypeAsTargetLabel

      public String getTokenTypeAsTargetLabel(int ttype)
      Get a meaningful name for a token type useful during code generation. Literals without associated names are converted to the string equivalent of their integer values. Used to generate x==ID and x==34 type comparisons etc... Essentially we are looking for the most obvious way to refer to a token type in the generated code. If in the lexer, return the char literal translated to the target language. For example, ttype=10 will yield '\n' from the getTokenDisplayName method. That must be converted to the target languages literals. For most C-derived languages no translation is needed.
    • genTokenVocabOutput

      protected org.stringtemplate.v4.ST genTokenVocabOutput()
      Generate a token vocab file with all the token names/types. For example: ID=7 FOR=8 'for'=8 This is independent of the target language; used by antlr internally
    • translateAction

      public List<? extends Object> translateAction(String ruleName, GrammarAST actionTree)
    • translateArgAction

      public List<org.stringtemplate.v4.ST> translateArgAction(String ruleName, GrammarAST actionTree)
      Translate an action like [3,"foo",a[3]] and return a List of the translated actions. Because actions are themselves translated to a list of chunks, must cat together into a ST>. Don't translate to strings early as we need to eval templates in context.
    • getListOfArgumentsFromAction

      public static List<String> getListOfArgumentsFromAction(String actionText, int separatorChar)
    • getListOfArgumentsFromAction

      public static int getListOfArgumentsFromAction(String actionText, int start, int targetChar, int separatorChar, List<String> args)
      Given an arg action like [x, (*a).foo(21,33), 3.2+1, '\n', "a,oo\nick", {bl, "fdkj"eck}, ["cat\n,", x, 43]] convert to a list of arguments. Allow nested square brackets etc... Set separatorChar to ';' or ',' or whatever you want.
    • translateTemplateConstructor

      public org.stringtemplate.v4.ST translateTemplateConstructor(String ruleName, int outerAltNum, Token actionToken, String templateActionText)
      Given a template constructor action like %foo(a={...}) in an action, translate it to the appropriate template constructor from the templateLib. This translates a *piece* of the action.
    • issueInvalidScopeError

      public void issueInvalidScopeError(String x, String y, Rule enclosingRule, Token actionToken, int outerAltNum)
    • issueInvalidAttributeError

      public void issueInvalidAttributeError(String x, String y, Rule enclosingRule, Token actionToken, int outerAltNum)
    • issueInvalidAttributeError

      public void issueInvalidAttributeError(String x, Rule enclosingRule, Token actionToken, int outerAltNum)
    • getTemplates

      public org.stringtemplate.v4.STGroup getTemplates()
    • getBaseTemplates

      public org.stringtemplate.v4.STGroup getBaseTemplates()
    • setDebug

      public void setDebug(boolean debug)
    • setTrace

      public void setTrace(boolean trace)
    • setProfile

      public void setProfile(boolean profile)
    • getRecognizerST

      public org.stringtemplate.v4.ST getRecognizerST()
    • getRecognizerFileName

      public String getRecognizerFileName(String name, int type)
      Generate TParser.java and TLexer.java from T.g if combined, else just use T.java as output regardless of type.
    • getVocabFileName

      public String getVocabFileName()
      What is the name of the vocab file generated for this grammar? Returns null if no .tokens file should be generated.
    • write

      public void write(org.stringtemplate.v4.ST code, String fileName) throws IOException
      Throws:
      IOException
    • canGenerateSwitch

      protected boolean canGenerateSwitch(DFAState s)
      You can generate a switch rather than if-then-else for a DFA state if there are no semantic predicates and the number of edge label values is small enough; e.g., don't generate a switch for a state containing an edge label such as 20..52330 (the resulting byte codes would overflow the method 65k limit probably).
    • createUniqueLabel

      public String createUniqueLabel(String name)
      Create a label to track a token / rule reference's result. Technically, this is a place where I break model-view separation as I am creating a variable name that could be invalid in a target language, however, label ::= <ID><INT> is probably ok in all languages we care about.