114 lines
2.9 KiB
JavaScript
114 lines
2.9 KiB
JavaScript
"use strict";
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module.exports = Whitespace;
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var sortBy = require("lodash/collection/sortBy");
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/**
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* Returns `i`th number from `base`, continuing from 0 when `max` is reached.
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* Useful for shifting `for` loop by a fixed number but going over all items.
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*
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* @param {Number} i Current index in the loop
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* @param {Number} base Start index for which to return 0
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* @param {Number} max Array length
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* @returns {Number} shiftedIndex
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*/
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function getLookupIndex(i, base, max) {
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i += base;
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if (i >= max)
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i -= max;
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return i;
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}
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function Whitespace(tokens, comments) {
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this.tokens = sortBy(tokens.concat(comments), "start");
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this.used = {};
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// Profiling this code shows that while generator passes over it, indexes
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// returned by `getNewlinesBefore` and `getNewlinesAfter` are always increasing.
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// We use this implementation detail for an optimization: instead of always
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// starting to look from `this.tokens[0]`, we will start `for` loops from the
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// previous successful match. We will enumerate all tokens—but the common
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// case will be much faster.
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this._lastFoundIndex = 0;
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}
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Whitespace.prototype.getNewlinesBefore = function (node) {
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var startToken;
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var endToken;
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var tokens = this.tokens;
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var token;
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for (var j = 0; j < tokens.length; j++) {
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// optimize for forward traversal by shifting for loop index
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var i = getLookupIndex(j, this._lastFoundIndex, this.tokens.length);
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token = tokens[i];
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// this is the token this node starts with
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if (node.start === token.start) {
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startToken = tokens[i - 1];
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endToken = token;
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this._lastFoundIndex = i;
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break;
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}
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}
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return this.getNewlinesBetween(startToken, endToken);
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};
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Whitespace.prototype.getNewlinesAfter = function (node) {
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var startToken;
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var endToken;
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var tokens = this.tokens;
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var token;
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for (var j = 0; j < tokens.length; j++) {
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// optimize for forward traversal by shifting for loop index
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var i = getLookupIndex(j, this._lastFoundIndex, this.tokens.length);
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token = tokens[i];
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// this is the token this node ends with
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if (node.end === token.end) {
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startToken = token;
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endToken = tokens[i + 1];
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this._lastFoundIndex = i;
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break;
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}
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}
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if (endToken && endToken.type.type === "eof") {
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return 1;
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} else {
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var lines = this.getNewlinesBetween(startToken, endToken);
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if (node.type === "Line" && !lines) {
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// line comment
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return 1;
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} else {
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return lines;
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}
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}
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};
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Whitespace.prototype.getNewlinesBetween = function (startToken, endToken) {
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if (!endToken || !endToken.loc) return 0;
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var start = startToken ? startToken.loc.end.line : 1;
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var end = endToken.loc.start.line;
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var lines = 0;
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for (var line = start; line < end; line++) {
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if (typeof this.used[line] === "undefined") {
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this.used[line] = true;
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lines++;
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}
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}
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return lines;
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};
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