RuleContext.js

/* Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */
///

//  A rule context is a record of a single rule invocation. It knows
//  which context invoked it, if any. If there is no parent context, then
//  naturally the invoking state is not valid.  The parent link
//  provides a chain upwards from the current rule invocation to the root
//  of the invocation tree, forming a stack. We actually carry no
//  information about the rule associated with this context (except
//  when parsing). We keep only the state number of the invoking state from
//  the ATN submachine that invoked this. Contrast this with the s
//  pointer inside ParserRuleContext that tracks the current state
//  being "executed" for the current rule.
//
//  The parent contexts are useful for computing lookahead sets and
//  getting error information.
//
//  These objects are used during parsing and prediction.
//  For the special case of parsers, we use the subclass
//  ParserRuleContext.
//
//  @see ParserRuleContext
///

var RuleNode = require('./tree/Tree').RuleNode;
var INVALID_INTERVAL = require('./tree/Tree').INVALID_INTERVAL;
var INVALID_ALT_NUMBER = require('./atn/ATN').INVALID_ALT_NUMBER;

function RuleContext(parent, invokingState) {
	RuleNode.call(this);
	// What context invoked this rule?
	this.parentCtx = parent || null;
	// What state invoked the rule associated with this context?
	// The "return address" is the followState of invokingState
	// If parent is null, this should be -1.
	this.invokingState = invokingState || -1;
	return this;
}

RuleContext.prototype = Object.create(RuleNode.prototype);
RuleContext.prototype.constructor = RuleContext;

RuleContext.prototype.depth = function() {
	var n = 0;
	var p = this;
	while (p !== null) {
		p = p.parentCtx;
		n += 1;
	}
	return n;
};

// A context is empty if there is no invoking state; meaning nobody call
// current context.
RuleContext.prototype.isEmpty = function() {
	return this.invokingState === -1;
};

// satisfy the ParseTree / SyntaxTree interface

RuleContext.prototype.getSourceInterval = function() {
	return INVALID_INTERVAL;
};

RuleContext.prototype.getRuleContext = function() {
	return this;
};

RuleContext.prototype.getPayload = function() {
	return this;
};

// Return the combined text of all child nodes. This method only considers
// tokens which have been added to the parse tree.
// <p>
// Since tokens on hidden channels (e.g. whitespace or comments) are not
// added to the parse trees, they will not appear in the output of this
// method.
// /
RuleContext.prototype.getText = function() {
	if (this.getChildCount() === 0) {
		return "";
	} else {
		return this.children.map(function(child) {
			return child.getText();
		}).join("");
	}
};

// For rule associated with this parse tree internal node, return
// the outer alternative number used to match the input. Default
// implementation does not compute nor store this alt num. Create
// a subclass of ParserRuleContext with backing field and set
// option contextSuperClass.
// to set it.
RuleContext.prototype.getAltNumber = function() { return INVALID_ALT_NUMBER; }

// Set the outer alternative number for this context node. Default
// implementation does nothing to avoid backing field overhead for
// trees that don't need it.  Create
// a subclass of ParserRuleContext with backing field and set
// option contextSuperClass.
RuleContext.prototype.setAltNumber = function(altNumber) { }

RuleContext.prototype.getChild = function(i) {
	return null;
};

RuleContext.prototype.getChildCount = function() {
	return 0;
};

RuleContext.prototype.accept = function(visitor) {
	return visitor.visitChildren(this);
};

//need to manage circular dependencies, so export now
exports.RuleContext = RuleContext;
var Trees = require('./tree/Trees').Trees;


// Print out a whole tree, not just a node, in LISP format
// (root child1 .. childN). Print just a node if this is a leaf.
//

RuleContext.prototype.toStringTree = function(ruleNames, recog) {
	return Trees.toStringTree(this, ruleNames, recog);
};

RuleContext.prototype.toString = function(ruleNames, stop) {
	ruleNames = ruleNames || null;
	stop = stop || null;
	var p = this;
	var s = "[";
	while (p !== null && p !== stop) {
		if (ruleNames === null) {
			if (!p.isEmpty()) {
				s += p.invokingState;
			}
		} else {
			var ri = p.ruleIndex;
			var ruleName = (ri >= 0 && ri < ruleNames.length) ? ruleNames[ri]
					: "" + ri;
			s += ruleName;
		}
		if (p.parentCtx !== null && (ruleNames !== null || !p.parentCtx.isEmpty())) {
			s += " ";
		}
		p = p.parentCtx;
	}
	s += "]";
	return s;
};