47 lines
1.5 KiB
TypeScript
47 lines
1.5 KiB
TypeScript
import { RuntimeError } from "../worker-errors";
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/**
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* A barebones input stream implementation for consuming integers and characters from a string.
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*/
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export default class InputStream {
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private _text: string;
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/** Create a new input stream loaded with the given input */
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constructor(text: string) {
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this._text = text;
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}
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/** Remove leading whitespace from the current input stream */
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private exhaustLeadingWhitespace(): void {
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const firstChar = this._text.trim()[0];
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const posn = this._text.search(firstChar);
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this._text = this._text.slice(posn);
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}
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/** Parse input stream for an integer */
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getNumber(): number {
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this.exhaustLeadingWhitespace();
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// The extra whitespace differentiates whether string is empty or all numbers.
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if (this._text === "") throw new RuntimeError("Unexpected end of input");
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let posn = this._text.search(/[^0-9]/);
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if (posn === 0)
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throw new RuntimeError(`Unexpected input character: '${this._text[0]}'`);
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if (posn === -1) posn = this._text.length;
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// Consume and parse numeric part
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const numStr = this._text.slice(0, posn);
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this._text = this._text.slice(posn);
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return parseInt(numStr, 10);
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}
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/**
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* Parse input stream for the first character, and return its ASCII code.
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* If end of input, returns -1.
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*/
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getChar(): number {
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if (this._text.length === 0) return -1;
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const char = this._text[0];
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this._text = this._text.slice(1);
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return char.charCodeAt(0);
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}
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}
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