antlr4-runtime
Version:
JavaScript runtime for ANTLR4
456 lines (431 loc) • 17 kB
JavaScript
/* Copyright (c) 2012-2022 The ANTLR Project Contributors. All rights reserved.
* Use is of this file is governed by the BSD 3-clause license that
* can be found in the LICENSE.txt file in the project root.
*/
import RuleContext from "./RuleContext.js";
import PredictionContext from "./PredictionContext.js";
import ArrayPredictionContext from "./ArrayPredictionContext.js";
import SingletonPredictionContext from "./SingletonPredictionContext.js";
import EmptyPredictionContext from "./EmptyPredictionContext.js";
import HashMap from "../misc/HashMap.js";
/**
* Convert a {@link RuleContext} tree to a {@link PredictionContext} graph.
* Return {@link //EMPTY} if {@code outerContext} is empty or null.
*/
export function predictionContextFromRuleContext(atn, outerContext) {
if (outerContext === undefined || outerContext === null) {
outerContext = RuleContext.EMPTY;
}
// if we are in RuleContext of start rule, s, then PredictionContext
// is EMPTY. Nobody called us. (if we are empty, return empty)
if (outerContext.parentCtx === null || outerContext === RuleContext.EMPTY) {
return PredictionContext.EMPTY;
}
// If we have a parent, convert it to a PredictionContext graph
const parent = predictionContextFromRuleContext(atn, outerContext.parentCtx);
const state = atn.states[outerContext.invokingState];
const transition = state.transitions[0];
return SingletonPredictionContext.create(parent, transition.followState.stateNumber);
}
export function getCachedPredictionContext(context, contextCache, visited) {
if (context.isEmpty()) {
return context;
}
let existing = visited.get(context) || null;
if (existing !== null) {
return existing;
}
existing = contextCache.get(context);
if (existing !== null) {
visited.set(context, existing);
return existing;
}
let changed = false;
let parents = [];
for (let i = 0; i < parents.length; i++) {
const parent = getCachedPredictionContext(context.getParent(i), contextCache, visited);
if (changed || parent !== context.getParent(i)) {
if (!changed) {
parents = [];
for (let j = 0; j < context.length; j++) {
parents[j] = context.getParent(j);
}
changed = true;
}
parents[i] = parent;
}
}
if (!changed) {
contextCache.add(context);
visited.set(context, context);
return context;
}
let updated = null;
if (parents.length === 0) {
updated = PredictionContext.EMPTY;
} else if (parents.length === 1) {
updated = SingletonPredictionContext.create(parents[0], context
.getReturnState(0));
} else {
updated = new ArrayPredictionContext(parents, context.returnStates);
}
contextCache.add(updated);
visited.set(updated, updated);
visited.set(context, updated);
return updated;
}
export function merge(a, b, rootIsWildcard, mergeCache) {
// share same graph if both same
if (a === b) {
return a;
}
if (a instanceof SingletonPredictionContext && b instanceof SingletonPredictionContext) {
return mergeSingletons(a, b, rootIsWildcard, mergeCache);
}
// At least one of a or b is array
// If one is $ and rootIsWildcard, return $ as * wildcard
if (rootIsWildcard) {
if (a instanceof EmptyPredictionContext) {
return a;
}
if (b instanceof EmptyPredictionContext) {
return b;
}
}
// convert singleton so both are arrays to normalize
if (a instanceof SingletonPredictionContext) {
a = new ArrayPredictionContext([a.getParent()], [a.returnState]);
}
if (b instanceof SingletonPredictionContext) {
b = new ArrayPredictionContext([b.getParent()], [b.returnState]);
}
return mergeArrays(a, b, rootIsWildcard, mergeCache);
}
/**
* Merge two {@link ArrayPredictionContext} instances.
*
* <p>Different tops, different parents.<br>
* <embed src="images/ArrayMerge_DiffTopDiffPar.svg" type="image/svg+xml"/></p>
*
* <p>Shared top, same parents.<br>
* <embed src="images/ArrayMerge_ShareTopSamePar.svg" type="image/svg+xml"/></p>
*
* <p>Shared top, different parents.<br>
* <embed src="images/ArrayMerge_ShareTopDiffPar.svg" type="image/svg+xml"/></p>
*
* <p>Shared top, all shared parents.<br>
* <embed src="images/ArrayMerge_ShareTopSharePar.svg"
* type="image/svg+xml"/></p>
*
* <p>Equal tops, merge parents and reduce top to
* {@link SingletonPredictionContext}.<br>
* <embed src="images/ArrayMerge_EqualTop.svg" type="image/svg+xml"/></p>
*/
function mergeArrays(a, b, rootIsWildcard, mergeCache) {
if (mergeCache !== null) {
let previous = mergeCache.get(a, b);
if (previous !== null) {
if ( PredictionContext.trace_atn_sim ) console.log("mergeArrays a="+a+",b="+b+" -> previous");
return previous;
}
previous = mergeCache.get(b, a);
if (previous !== null) {
if ( PredictionContext.trace_atn_sim ) console.log("mergeArrays a="+a+",b="+b+" -> previous");
return previous;
}
}
// merge sorted payloads a + b => M
let i = 0; // walks a
let j = 0; // walks b
let k = 0; // walks target M array
let mergedReturnStates = new Array(a.returnStates.length + b.returnStates.length).fill(0);
let mergedParents = new Array(a.returnStates.length + b.returnStates.length).fill(null);
// walk and merge to yield mergedParents, mergedReturnStates
while (i < a.returnStates.length && j < b.returnStates.length) {
const a_parent = a.parents[i];
const b_parent = b.parents[j];
if (a.returnStates[i] === b.returnStates[j]) {
// same payload (stack tops are equal), must yield merged singleton
const payload = a.returnStates[i];
// $+$ = $
const bothDollars = payload === PredictionContext.EMPTY_RETURN_STATE &&
a_parent === null && b_parent === null;
const ax_ax = (a_parent !== null && b_parent !== null && a_parent === b_parent); // ax+ax
// ->
// ax
if (bothDollars || ax_ax) {
mergedParents[k] = a_parent; // choose left
mergedReturnStates[k] = payload;
} else { // ax+ay -> a'[x,y]
mergedParents[k] = merge(a_parent, b_parent, rootIsWildcard, mergeCache);
mergedReturnStates[k] = payload;
}
i += 1; // hop over left one as usual
j += 1; // but also skip one in right side since we merge
} else if (a.returnStates[i] < b.returnStates[j]) { // copy a[i] to M
mergedParents[k] = a_parent;
mergedReturnStates[k] = a.returnStates[i];
i += 1;
} else { // b > a, copy b[j] to M
mergedParents[k] = b_parent;
mergedReturnStates[k] = b.returnStates[j];
j += 1;
}
k += 1;
}
// copy over any payloads remaining in either array
if (i < a.returnStates.length) {
for (let p = i; p < a.returnStates.length; p++) {
mergedParents[k] = a.parents[p];
mergedReturnStates[k] = a.returnStates[p];
k += 1;
}
} else {
for (let p = j; p < b.returnStates.length; p++) {
mergedParents[k] = b.parents[p];
mergedReturnStates[k] = b.returnStates[p];
k += 1;
}
}
// trim merged if we combined a few that had same stack tops
if (k < mergedParents.length) { // write index < last position; trim
if (k === 1) { // for just one merged element, return singleton top
const a_ = SingletonPredictionContext.create(mergedParents[0],
mergedReturnStates[0]);
if (mergeCache !== null) {
mergeCache.set(a, b, a_);
}
return a_;
}
mergedParents = mergedParents.slice(0, k);
mergedReturnStates = mergedReturnStates.slice(0, k);
}
const M = new ArrayPredictionContext(mergedParents, mergedReturnStates);
// if we created same array as a or b, return that instead
// TODO: track whether this is possible above during merge sort for speed
if (M.equals(a)) {
if (mergeCache !== null) {
mergeCache.set(a, b, a);
}
if ( PredictionContext.trace_atn_sim ) console.log("mergeArrays a="+a+",b="+b+" -> a");
return a;
}
if (M.equals(b)) {
if (mergeCache !== null) {
mergeCache.set(a, b, b);
}
if ( PredictionContext.trace_atn_sim ) console.log("mergeArrays a="+a+",b="+b+" -> b");
return b;
}
combineCommonParents(mergedParents);
if (mergeCache !== null) {
mergeCache.set(a, b, M);
}
if ( PredictionContext.trace_atn_sim ) console.log("mergeArrays a="+a+",b="+b+" -> "+M);
return M;
}
/**
* Make pass over all <em>M</em> {@code parents}; merge any {@code equals()}
* ones.
*/
function combineCommonParents(parents) {
const uniqueParents = new HashMap();
for (let p = 0; p < parents.length; p++) {
const parent = parents[p];
if (!(uniqueParents.containsKey(parent))) {
uniqueParents.set(parent, parent);
}
}
for (let q = 0; q < parents.length; q++) {
parents[q] = uniqueParents.get(parents[q]);
}
}
/**
* Merge two {@link SingletonPredictionContext} instances.
*
* <p>Stack tops equal, parents merge is same; return left graph.<br>
* <embed src="images/SingletonMerge_SameRootSamePar.svg"
* type="image/svg+xml"/></p>
*
* <p>Same stack top, parents differ; merge parents giving array node, then
* remainders of those graphs. A new root node is created to point to the
* merged parents.<br>
* <embed src="images/SingletonMerge_SameRootDiffPar.svg"
* type="image/svg+xml"/></p>
*
* <p>Different stack tops pointing to same parent. Make array node for the
* root where both element in the root point to the same (original)
* parent.<br>
* <embed src="images/SingletonMerge_DiffRootSamePar.svg"
* type="image/svg+xml"/></p>
*
* <p>Different stack tops pointing to different parents. Make array node for
* the root where each element points to the corresponding original
* parent.<br>
* <embed src="images/SingletonMerge_DiffRootDiffPar.svg"
* type="image/svg+xml"/></p>
*
* @param a the first {@link SingletonPredictionContext}
* @param b the second {@link SingletonPredictionContext}
* @param rootIsWildcard {@code true} if this is a local-context merge,
* otherwise false to indicate a full-context merge
* @param mergeCache
*/
function mergeSingletons(a, b, rootIsWildcard, mergeCache) {
if (mergeCache !== null) {
let previous = mergeCache.get(a, b);
if (previous !== null) {
return previous;
}
previous = mergeCache.get(b, a);
if (previous !== null) {
return previous;
}
}
const rootMerge = mergeRoot(a, b, rootIsWildcard);
if (rootMerge !== null) {
if (mergeCache !== null) {
mergeCache.set(a, b, rootMerge);
}
return rootMerge;
}
if (a.returnState === b.returnState) {
const parent = merge(a.parentCtx, b.parentCtx, rootIsWildcard, mergeCache);
// if parent is same as existing a or b parent or reduced to a parent,
// return it
if (parent === a.parentCtx) {
return a; // ax + bx = ax, if a=b
}
if (parent === b.parentCtx) {
return b; // ax + bx = bx, if a=b
}
// else: ax + ay = a'[x,y]
// merge parents x and y, giving array node with x,y then remainders
// of those graphs. dup a, a' points at merged array
// new joined parent so create new singleton pointing to it, a'
const spc = SingletonPredictionContext.create(parent, a.returnState);
if (mergeCache !== null) {
mergeCache.set(a, b, spc);
}
return spc;
} else { // a != b payloads differ
// see if we can collapse parents due to $+x parents if local ctx
let singleParent = null;
if (a === b || (a.parentCtx !== null && a.parentCtx === b.parentCtx)) { // ax +
// bx =
// [a,b]x
singleParent = a.parentCtx;
}
if (singleParent !== null) { // parents are same
// sort payloads and use same parent
const payloads = [ a.returnState, b.returnState ];
if (a.returnState > b.returnState) {
payloads[0] = b.returnState;
payloads[1] = a.returnState;
}
const parents = [ singleParent, singleParent ];
const apc = new ArrayPredictionContext(parents, payloads);
if (mergeCache !== null) {
mergeCache.set(a, b, apc);
}
return apc;
}
// parents differ and can't merge them. Just pack together
// into array; can't merge.
// ax + by = [ax,by]
const payloads = [ a.returnState, b.returnState ];
let parents = [ a.parentCtx, b.parentCtx ];
if (a.returnState > b.returnState) { // sort by payload
payloads[0] = b.returnState;
payloads[1] = a.returnState;
parents = [ b.parentCtx, a.parentCtx ];
}
const a_ = new ArrayPredictionContext(parents, payloads);
if (mergeCache !== null) {
mergeCache.set(a, b, a_);
}
return a_;
}
}
/**
* Handle case where at least one of {@code a} or {@code b} is
* {@link //EMPTY}. In the following diagrams, the symbol {@code $} is used
* to represent {@link //EMPTY}.
*
* <h2>Local-Context Merges</h2>
*
* <p>These local-context merge operations are used when {@code rootIsWildcard}
* is true.</p>
*
* <p>{@link //EMPTY} is superset of any graph; return {@link //EMPTY}.<br>
* <embed src="images/LocalMerge_EmptyRoot.svg" type="image/svg+xml"/></p>
*
* <p>{@link //EMPTY} and anything is {@code //EMPTY}, so merged parent is
* {@code //EMPTY}; return left graph.<br>
* <embed src="images/LocalMerge_EmptyParent.svg" type="image/svg+xml"/></p>
*
* <p>Special case of last merge if local context.<br>
* <embed src="images/LocalMerge_DiffRoots.svg" type="image/svg+xml"/></p>
*
* <h2>Full-Context Merges</h2>
*
* <p>These full-context merge operations are used when {@code rootIsWildcard}
* is false.</p>
*
* <p><embed src="images/FullMerge_EmptyRoots.svg" type="image/svg+xml"/></p>
*
* <p>Must keep all contexts; {@link //EMPTY} in array is a special value (and
* null parent).<br>
* <embed src="images/FullMerge_EmptyRoot.svg" type="image/svg+xml"/></p>
*
* <p><embed src="images/FullMerge_SameRoot.svg" type="image/svg+xml"/></p>
*
* @param a the first {@link SingletonPredictionContext}
* @param b the second {@link SingletonPredictionContext}
* @param rootIsWildcard {@code true} if this is a local-context merge,
* otherwise false to indicate a full-context merge
*/
function mergeRoot(a, b, rootIsWildcard) {
if (rootIsWildcard) {
if (a === PredictionContext.EMPTY) {
return PredictionContext.EMPTY; // // + b =//
}
if (b === PredictionContext.EMPTY) {
return PredictionContext.EMPTY; // a +// =//
}
} else {
if (a === PredictionContext.EMPTY && b === PredictionContext.EMPTY) {
return PredictionContext.EMPTY; // $ + $ = $
} else if (a === PredictionContext.EMPTY) { // $ + x = [$,x]
const payloads = [ b.returnState,
PredictionContext.EMPTY_RETURN_STATE ];
const parents = [ b.parentCtx, null ];
return new ArrayPredictionContext(parents, payloads);
} else if (b === PredictionContext.EMPTY) { // x + $ = [$,x] ($ is always first if present)
const payloads = [ a.returnState, PredictionContext.EMPTY_RETURN_STATE ];
const parents = [ a.parentCtx, null ];
return new ArrayPredictionContext(parents, payloads);
}
}
return null;
}
// ter's recursive version of Sam's getAllNodes()
export function getAllContextNodes(context, nodes, visited) {
if (nodes === null) {
nodes = [];
return getAllContextNodes(context, nodes, visited);
} else if (visited === null) {
visited = new HashMap();
return getAllContextNodes(context, nodes, visited);
} else {
if (context === null || visited.containsKey(context)) {
return nodes;
}
visited.set(context, context);
nodes.push(context);
for (let i = 0; i < context.length; i++) {
getAllContextNodes(context.getParent(i), nodes, visited);
}
return nodes;
}
}