Skip to content
Permalink
9bfb9ba527
Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
Go to file
 
 
Cannot retrieve contributors at this time
76 lines (68 sloc) 2.27 KB
/**
* @fileoverview Define the abstract class about cursors which iterate tokens.
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Exports
//------------------------------------------------------------------------------
/**
* The abstract class about cursors which iterate tokens.
*
* This class has 2 abstract methods.
*
* - `current: Token | Comment | null` ... The current token.
* - `moveNext(): boolean` ... Moves this cursor to the next token. If the next token didn't exist, it returns `false`.
*
* This is similar to ES2015 Iterators.
* However, Iterators were slow (at 2017-01), so I created this class as similar to C# IEnumerable.
*
* There are the following known sub classes.
*
* - ForwardTokenCursor .......... The cursor which iterates tokens only.
* - BackwardTokenCursor ......... The cursor which iterates tokens only in reverse.
* - ForwardTokenCommentCursor ... The cursor which iterates tokens and comments.
* - BackwardTokenCommentCursor .. The cursor which iterates tokens and comments in reverse.
* - DecorativeCursor
* - FilterCursor ............ The cursor which ignores the specified tokens.
* - SkipCursor .............. The cursor which ignores the first few tokens.
* - LimitCursor ............. The cursor which limits the count of tokens.
*
*/
module.exports = class Cursor {
/**
* Initializes this cursor.
*/
constructor() {
this.current = null;
}
/**
* Gets the first token.
* This consumes this cursor.
* @returns {Token|Comment} The first token or null.
*/
getOneToken() {
return this.moveNext() ? this.current : null;
}
/**
* Gets the first tokens.
* This consumes this cursor.
* @returns {(Token|Comment)[]} All tokens.
*/
getAllTokens() {
const tokens = [];
while (this.moveNext()) {
tokens.push(this.current);
}
return tokens;
}
/**
* Moves this cursor to the next token.
* @returns {boolean} `true` if the next token exists.
* @abstract
*/
/* c8 ignore next */
moveNext() { // eslint-disable-line class-methods-use-this -- Unused
throw new Error("Not implemented.");
}
};