Add Befunge-93

engines/befunge93/input-stream.ts

@@ -0,0 +1,46 @@
+import { RuntimeError } from "../worker-errors";
+
+/**
+ * A barebones input stream implementation for consuming integers and characters from a string.
+ */
+export default class InputStream {
+  private _text: string;
+
+  /** Create a new input stream loaded with the given input */
+  constructor(text: string) {
+    this._text = text;
+  }
+
+  /** Remove leading whitespace from the current input stream */
+  private exhaustLeadingWhitespace(): void {
+    const firstChar = this._text.trim()[0];
+    const posn = this._text.search(firstChar);
+    this._text = this._text.slice(posn);
+  }
+
+  /** Parse input stream for an integer */
+  getNumber(): number {
+    this.exhaustLeadingWhitespace();
+    // The extra whitespace differentiates whether string is empty or all numbers.
+    if (this._text === "") throw new RuntimeError("Unexpected end of input");
+    let posn = this._text.search(/[^0-9]/);
+    if (posn === 0)
+      throw new RuntimeError(`Unexpected input character: '${this._text[0]}'`);
+    if (posn === -1) posn = this._text.length;
+    // Consume and parse numeric part
+    const numStr = this._text.slice(0, posn);
+    this._text = this._text.slice(posn);
+    return parseInt(numStr, 10);
+  }
+
+  /**
+   * Parse input stream for the first character, and return its ASCII code.
+   * If end of input, returns -1.
+   */
+  getChar(): number {
+    if (this._text.length === 0) return -1;
+    const char = this._text[0];
+    this._text = this._text.slice(1);
+    return char.charCodeAt(0);
+  }
+}