walt-compiler/src/utils/stream.js

Alternative syntax for WebAssembly text format

// @flow
export const eol = (char: string) => char === '\n';

// Base Character stream class
class Stream {
  input: string;
  pos: number;
  line: number;
  col: number;
  lines: string[];

  constructor(input: string) {
    this.pos = this.line = this.col = 0;
    this.input = input;
    this.lines = input.split('\n');
    this.newLine();
  }

  // Peek at a character at current position
  peek(): string {
    return this.input.charAt(this.pos);
  }

  // Advance to next character in stream
  next(): string {
    const char = this.input.charAt(this.pos++);

    if (this.eol(char)) {
      this.newLine();
    } else {
      this.col++;
    }

    return char;
  }

  // Begin a new line
  newLine() {
    this.line++;
    this.col = 0;
  }

  // Is the character an end of line
  eol(char: string): boolean {
    return char === '\n';
  }

  // Is the character an end of file
  eof(char: string): boolean {
    return char === '';
  }

  // Is the character a whitespace
  static whitespace(char: string): boolean {
    return (
      char === '\n' ||
      char === ' ' ||
      char === '\t' ||
      char === '\v' ||
      char === '\r' ||
      char === '\f'
    );
  }
}

export default Stream;