org.antlr.codegen
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 Summary

ACyclicDFACodeGenerator	acyclicDFAGenerator I have factored out the generation of acyclic DFAs to separate class
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.
static String	classpathTemplateRootDirectoryName
protected boolean	debug Generate debugging event method calls
boolean	GENERATE_SWITCHES_WHEN_POSSIBLE
Grammar	grammar Which grammar are we generating code for? Each generator is attached to a specific grammar.
protected org.stringtemplate.v4.ST	headerFileST
protected String	language What language are we generating?
static boolean	LAUNCH_ST_INSPECTOR
protected int	lineWidth
static int	MADSI_DEFAULT
static int	MAX_ACYCLIC_DFA_STATES_INLINE
static int	MAX_SWITCH_CASE_LABELS
static int	MIN_SWITCH_ALTS
static int	MSA_DEFAULT
static int	MSCL_DEFAULT When generating SWITCH statements, some targets might need to limit the size (based upon the number of case labels).
protected org.stringtemplate.v4.ST	outputFileST
protected boolean	profile Track runtime parsing information about decisions etc...
protected org.stringtemplate.v4.ST	recognizerST
Target	target The target specifies how to write out files and do other language specific actions.
protected org.stringtemplate.v4.STGroup	templates Where are the templates this generator should use to generate code?
protected Tool	tool A reference to the ANTLR tool so we can learn about output directories and such.
protected boolean	trace Create a Tracer object and make the recognizer invoke this.
protected int	uniqueLabelNumber Used to create unique labels
static String	VOCAB_FILE_EXTENSION I have factored out the generation of cyclic DFAs to separate class
protected static String	vocabFilePattern

Constructor Summary

CodeGenerator(Tool tool, Grammar grammar, String language)

Method Summary

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).
String	createUniqueLabel(String name) Create a label to track a token / rule reference's result.
void	generateLocalFOLLOW(GrammarAST referencedElementNode, String referencedElementName, String enclosingRuleName, int elementIndex) Error recovery in ANTLR recognizers.
org.stringtemplate.v4.ST	generateSpecialState(DFAState s) A special state is huge (too big for state tables) or has a predicated edge.
protected org.stringtemplate.v4.ST	genLabelExpr(org.stringtemplate.v4.STGroup templates, Transition edge, int k) Generate an expression for traversing an edge.
org.stringtemplate.v4.ST	genLookaheadDecision(org.stringtemplate.v4.ST recognizerST, DFA dfa) Generate code that computes the predicted alt given a DFA.
org.stringtemplate.v4.ST	genRecognizer() Given the grammar to which we are attached, walk the AST associated with that grammar to create NFAs.
protected org.stringtemplate.v4.ST	genSemanticPredicateExpr(org.stringtemplate.v4.STGroup templates, Transition edge)
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)
protected void	genTokenTypeConstants(org.stringtemplate.v4.ST code) Set attributes tokens and literals attributes in the incoming code template.
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".
protected org.stringtemplate.v4.ST	genTokenVocabOutput() Generate a token vocab file with all the token names/types.
org.stringtemplate.v4.STGroup	getBaseTemplates()
static List<String>	getListOfArgumentsFromAction(String actionText, int separatorChar)
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.
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.
org.stringtemplate.v4.ST	getRecognizerST()
org.stringtemplate.v4.STGroup	getTemplates()
String	getTokenTypeAsTargetLabel(int ttype) Get a meaningful name for a token type useful during code generation.
String	getVocabFileName() What is the name of the vocab file generated for this grammar? Returns null if no .tokens file should be generated.
void	issueInvalidAttributeError(String x, Rule enclosingRule, Token actionToken, int outerAltNum)
void	issueInvalidAttributeError(String x, String y, Rule enclosingRule, Token actionToken, int outerAltNum)
void	issueInvalidScopeError(String x, String y, Rule enclosingRule, Token actionToken, int outerAltNum)
static Target	loadLanguageTarget(String language)
void	loadTemplates(String language) load the main language.stg template group file
void	setDebug(boolean debug)
void	setProfile(boolean profile)
void	setTrace(boolean trace)
List	translateAction(String ruleName, GrammarAST actionTree)
protected void	translateActionAttributeReferences(Map actions) Actions may reference $x::y attributes, call translateAction on each action and replace that action in the Map.
void	translateActionAttributeReferencesForSingleScope(Rule r, Map scopeActions) Use for translating rule @init{...} actions that have no scope
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.
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.
protected void	verifyActionScopesOkForTarget(Map actions) Some targets will have some extra scopes like C++ may have '@headerfile:name {action}' or something.
void	write(org.stringtemplate.v4.ST code, String fileName)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

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:

Constant Field Values

MAX_SWITCH_CASE_LABELS

public static int MAX_SWITCH_CASE_LABELS

MSA_DEFAULT

public static final int MSA_DEFAULT

See Also:

Constant Field Values

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:

Constant Field Values

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:

Constant Field Values

vocabFilePattern

protected static final String vocabFilePattern

See Also:

Constant Field Values

Constructor Detail

CodeGenerator

public CodeGenerator(Tool tool,
                     Grammar grammar,
                     String language)

Method Detail

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 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 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 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 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 ::= is probably ok in all languages we care about.