77 lines
2.3 KiB
JavaScript
77 lines
2.3 KiB
JavaScript
/**
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* @fileoverview Define the abstract class about cursors which iterate tokens.
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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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* The abstract class about cursors which iterate tokens.
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*
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* This class has 2 abstract methods.
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*
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* - `current: Token | Comment | null` ... The current token.
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* - `moveNext(): boolean` ... Moves this cursor to the next token. If the next token didn't exist, it returns `false`.
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*
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* This is similar to ES2015 Iterators.
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* However, Iterators were slow (at 2017-01), so I created this class as similar to C# IEnumerable.
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*
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* There are the following known sub classes.
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*
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* - ForwardTokenCursor .......... The cursor which iterates tokens only.
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* - BackwardTokenCursor ......... The cursor which iterates tokens only in reverse.
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* - ForwardTokenCommentCursor ... The cursor which iterates tokens and comments.
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* - BackwardTokenCommentCursor .. The cursor which iterates tokens and comments in reverse.
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* - DecorativeCursor
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* - FilterCursor ............ The cursor which ignores the specified tokens.
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* - SkipCursor .............. The cursor which ignores the first few tokens.
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* - LimitCursor ............. The cursor which limits the count of tokens.
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*
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*/
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module.exports = class Cursor {
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/**
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* Initializes this cursor.
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*/
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constructor() {
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this.current = null;
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}
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/**
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* Gets the first token.
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* This consumes this cursor.
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* @returns {Token|Comment} The first token or null.
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*/
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getOneToken() {
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return this.moveNext() ? this.current : null;
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}
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/**
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* Gets the first tokens.
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* This consumes this cursor.
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* @returns {(Token|Comment)[]} All tokens.
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*/
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getAllTokens() {
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const tokens = [];
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while (this.moveNext()) {
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tokens.push(this.current);
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}
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return tokens;
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}
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/**
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* Moves this cursor to the next token.
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* @returns {boolean} `true` if the next token exists.
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* @abstract
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*/
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/* istanbul ignore next */
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moveNext() { // eslint-disable-line class-methods-use-this
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throw new Error("Not implemented.");
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}
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};
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