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107 lines
3.7 KiB
107 lines
3.7 KiB
/**
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* @fileoverview Define utility functions for token store.
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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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// Exports
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//------------------------------------------------------------------------------
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/**
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* Finds the index of the first token which is after the given location.
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* If it was not found, this returns `tokens.length`.
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* @param {(Token|Comment)[]} tokens It searches the token in this list.
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* @param {number} location The location to search.
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* @returns {number} The found index or `tokens.length`.
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*/
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exports.search = function search(tokens, location) {
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for (let minIndex = 0, maxIndex = tokens.length - 1; minIndex <= maxIndex;) {
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/*
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* Calculate the index in the middle between minIndex and maxIndex.
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* `| 0` is used to round a fractional value down to the nearest integer: this is similar to
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* using `Math.trunc()` or `Math.floor()`, but performance tests have shown this method to
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* be faster.
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*/
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const index = (minIndex + maxIndex) / 2 | 0;
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const token = tokens[index];
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const tokenStartLocation = token.range[0];
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if (location <= tokenStartLocation) {
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if (index === minIndex) {
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return index;
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}
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maxIndex = index;
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} else {
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minIndex = index + 1;
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}
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}
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return tokens.length;
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};
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/**
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* Gets the index of the `startLoc` in `tokens`.
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* `startLoc` can be the value of `node.range[1]`, so this checks about `startLoc - 1` as well.
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* @param {(Token|Comment)[]} tokens The tokens to find an index.
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* @param {Object} indexMap The map from locations to indices.
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* @param {number} startLoc The location to get an index.
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* @returns {number} The index.
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*/
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exports.getFirstIndex = function getFirstIndex(tokens, indexMap, startLoc) {
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if (startLoc in indexMap) {
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return indexMap[startLoc];
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}
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if ((startLoc - 1) in indexMap) {
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const index = indexMap[startLoc - 1];
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const token = tokens[index];
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// If the mapped index is out of bounds, the returned cursor index will point after the end of the tokens array.
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if (!token) {
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return tokens.length;
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}
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/*
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* For the map of "comment's location -> token's index", it points the next token of a comment.
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* In that case, +1 is unnecessary.
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*/
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if (token.range[0] >= startLoc) {
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return index;
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}
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return index + 1;
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}
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return 0;
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};
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/**
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* Gets the index of the `endLoc` in `tokens`.
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* The information of end locations are recorded at `endLoc - 1` in `indexMap`, so this checks about `endLoc - 1` as well.
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* @param {(Token|Comment)[]} tokens The tokens to find an index.
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* @param {Object} indexMap The map from locations to indices.
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* @param {number} endLoc The location to get an index.
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* @returns {number} The index.
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*/
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exports.getLastIndex = function getLastIndex(tokens, indexMap, endLoc) {
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if (endLoc in indexMap) {
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return indexMap[endLoc] - 1;
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}
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if ((endLoc - 1) in indexMap) {
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const index = indexMap[endLoc - 1];
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const token = tokens[index];
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// If the mapped index is out of bounds, the returned cursor index will point before the end of the tokens array.
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if (!token) {
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return tokens.length - 1;
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}
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/*
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* For the map of "comment's location -> token's index", it points the next token of a comment.
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* In that case, -1 is necessary.
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*/
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if (token.range[1] > endLoc) {
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return index - 1;
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}
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return index;
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}
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return tokens.length - 1;
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};
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