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342 lines
12 KiB
342 lines
12 KiB
/**
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* @fileoverview A class of the code path.
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* @author Toru Nagashima
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const CodePathState = require("./code-path-state");
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const IdGenerator = require("./id-generator");
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//------------------------------------------------------------------------------
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// Public Interface
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//------------------------------------------------------------------------------
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/**
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* A code path.
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*/
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class CodePath {
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/**
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* Creates a new instance.
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* @param {Object} options Options for the function (see below).
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* @param {string} options.id An identifier.
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* @param {string} options.origin The type of code path origin.
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* @param {CodePath|null} options.upper The code path of the upper function scope.
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* @param {Function} options.onLooped A callback function to notify looping.
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*/
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constructor({ id, origin, upper, onLooped }) {
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/**
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* The identifier of this code path.
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* Rules use it to store additional information of each rule.
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* @type {string}
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*/
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this.id = id;
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/**
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* The reason that this code path was started. May be "program",
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* "function", "class-field-initializer", or "class-static-block".
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* @type {string}
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*/
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this.origin = origin;
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/**
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* The code path of the upper function scope.
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* @type {CodePath|null}
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*/
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this.upper = upper;
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/**
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* The code paths of nested function scopes.
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* @type {CodePath[]}
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*/
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this.childCodePaths = [];
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// Initializes internal state.
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Object.defineProperty(
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this,
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"internal",
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{ value: new CodePathState(new IdGenerator(`${id}_`), onLooped) }
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);
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// Adds this into `childCodePaths` of `upper`.
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if (upper) {
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upper.childCodePaths.push(this);
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}
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}
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/**
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* Gets the state of a given code path.
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* @param {CodePath} codePath A code path to get.
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* @returns {CodePathState} The state of the code path.
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*/
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static getState(codePath) {
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return codePath.internal;
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}
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/**
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* The initial code path segment. This is the segment that is at the head
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* of the code path.
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* This is a passthrough to the underlying `CodePathState`.
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* @type {CodePathSegment}
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*/
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get initialSegment() {
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return this.internal.initialSegment;
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}
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/**
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* Final code path segments. These are the terminal (tail) segments in the
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* code path, which is the combination of `returnedSegments` and `thrownSegments`.
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* All segments in this array are reachable.
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* This is a passthrough to the underlying `CodePathState`.
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* @type {CodePathSegment[]}
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*/
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get finalSegments() {
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return this.internal.finalSegments;
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}
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/**
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* Final code path segments that represent normal completion of the code path.
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* For functions, this means both explicit `return` statements and implicit returns,
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* such as the last reachable segment in a function that does not have an
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* explicit `return` as this implicitly returns `undefined`. For scripts,
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* modules, class field initializers, and class static blocks, this means
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* all lines of code have been executed.
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* These segments are also present in `finalSegments`.
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* This is a passthrough to the underlying `CodePathState`.
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* @type {CodePathSegment[]}
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*/
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get returnedSegments() {
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return this.internal.returnedForkContext;
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}
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/**
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* Final code path segments that represent `throw` statements.
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* This is a passthrough to the underlying `CodePathState`.
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* These segments are also present in `finalSegments`.
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* @type {CodePathSegment[]}
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*/
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get thrownSegments() {
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return this.internal.thrownForkContext;
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}
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/**
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* Tracks the traversal of the code path through each segment. This array
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* starts empty and segments are added or removed as the code path is
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* traversed. This array always ends up empty at the end of a code path
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* traversal. The `CodePathState` uses this to track its progress through
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* the code path.
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* This is a passthrough to the underlying `CodePathState`.
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* @type {CodePathSegment[]}
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* @deprecated
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*/
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get currentSegments() {
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return this.internal.currentSegments;
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}
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/**
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* Traverses all segments in this code path.
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*
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* codePath.traverseSegments((segment, controller) => {
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* // do something.
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* });
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*
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* This method enumerates segments in order from the head.
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*
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* The `controller` argument has two methods:
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*
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* - `skip()` - skips the following segments in this branch
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* - `break()` - skips all following segments in the traversal
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*
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* A note on the parameters: the `options` argument is optional. This means
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* the first argument might be an options object or the callback function.
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* @param {Object} [optionsOrCallback] Optional first and last segments to traverse.
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* @param {CodePathSegment} [optionsOrCallback.first] The first segment to traverse.
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* @param {CodePathSegment} [optionsOrCallback.last] The last segment to traverse.
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* @param {Function} callback A callback function.
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* @returns {void}
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*/
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traverseSegments(optionsOrCallback, callback) {
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// normalize the arguments into a callback and options
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let resolvedOptions;
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let resolvedCallback;
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if (typeof optionsOrCallback === "function") {
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resolvedCallback = optionsOrCallback;
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resolvedOptions = {};
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} else {
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resolvedOptions = optionsOrCallback || {};
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resolvedCallback = callback;
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}
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// determine where to start traversing from based on the options
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const startSegment = resolvedOptions.first || this.internal.initialSegment;
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const lastSegment = resolvedOptions.last;
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// set up initial location information
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let record = null;
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let index = 0;
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let end = 0;
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let segment = null;
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// segments that have already been visited during traversal
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const visited = new Set();
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// tracks the traversal steps
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const stack = [[startSegment, 0]];
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// tracks the last skipped segment during traversal
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let skippedSegment = null;
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// indicates if we exited early from the traversal
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let broken = false;
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/**
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* Maintains traversal state.
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*/
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const controller = {
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/**
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* Skip the following segments in this branch.
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* @returns {void}
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*/
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skip() {
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if (stack.length <= 1) {
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broken = true;
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} else {
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skippedSegment = stack[stack.length - 2][0];
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}
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},
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/**
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* Stop traversal completely - do not traverse to any
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* other segments.
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* @returns {void}
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*/
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break() {
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broken = true;
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}
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};
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/**
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* Checks if a given previous segment has been visited.
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* @param {CodePathSegment} prevSegment A previous segment to check.
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* @returns {boolean} `true` if the segment has been visited.
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*/
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function isVisited(prevSegment) {
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return (
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visited.has(prevSegment) ||
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segment.isLoopedPrevSegment(prevSegment)
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);
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}
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// the traversal
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while (stack.length > 0) {
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/*
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* This isn't a pure stack. We use the top record all the time
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* but don't always pop it off. The record is popped only if
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* one of the following is true:
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*
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* 1) We have already visited the segment.
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* 2) We have not visited *all* of the previous segments.
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* 3) We have traversed past the available next segments.
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*
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* Otherwise, we just read the value and sometimes modify the
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* record as we traverse.
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*/
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record = stack[stack.length - 1];
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segment = record[0];
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index = record[1];
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if (index === 0) {
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// Skip if this segment has been visited already.
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if (visited.has(segment)) {
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stack.pop();
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continue;
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}
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// Skip if all previous segments have not been visited.
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if (segment !== startSegment &&
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segment.prevSegments.length > 0 &&
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!segment.prevSegments.every(isVisited)
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) {
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stack.pop();
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continue;
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}
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// Reset the skipping flag if all branches have been skipped.
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if (skippedSegment && segment.prevSegments.includes(skippedSegment)) {
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skippedSegment = null;
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}
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visited.add(segment);
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/*
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* If the most recent segment hasn't been skipped, then we call
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* the callback, passing in the segment and the controller.
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*/
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if (!skippedSegment) {
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resolvedCallback.call(this, segment, controller);
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// exit if we're at the last segment
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if (segment === lastSegment) {
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controller.skip();
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}
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/*
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* If the previous statement was executed, or if the callback
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* called a method on the controller, we might need to exit the
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* loop, so check for that and break accordingly.
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*/
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if (broken) {
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break;
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}
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}
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}
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// Update the stack.
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end = segment.nextSegments.length - 1;
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if (index < end) {
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/*
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* If we haven't yet visited all of the next segments, update
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* the current top record on the stack to the next index to visit
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* and then push a record for the current segment on top.
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*
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* Setting the current top record's index lets us know how many
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* times we've been here and ensures that the segment won't be
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* reprocessed (because we only process segments with an index
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* of 0).
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*/
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record[1] += 1;
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stack.push([segment.nextSegments[index], 0]);
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} else if (index === end) {
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/*
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* If we are at the last next segment, then reset the top record
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* in the stack to next segment and set its index to 0 so it will
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* be processed next.
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*/
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record[0] = segment.nextSegments[index];
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record[1] = 0;
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} else {
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/*
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* If index > end, that means we have no more segments that need
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* processing. So, we pop that record off of the stack in order to
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* continue traversing at the next level up.
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*/
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stack.pop();
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}
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}
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}
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}
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module.exports = CodePath;
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