meteor/packages/html5-tokenizer/buffer.js

var Buffer = HTML5.Buffer = function Buffer() {
  this.data = '';
  this.start = 0;
  this.committed = 0;
  this.eof = false;
};

Buffer.prototype = {
  slice: function() {
    if(this.start >= this.data.length) {
      if(!this.eof) throw HTML5.DRAIN;
      return HTML5.EOF;
    }
    return this.data.slice(this.start, this.data.length);
  },
  char: function() {
    if(!this.eof && this.start >= this.data.length - 1) throw HTML5.DRAIN;
    if(this.start >= this.data.length) {
      return HTML5.EOF;
    }
    return this.data[this.start++];
  },
  advance: function(amount) {
    this.start += amount;
    if(this.start >= this.data.length) {
      if(!this.eof) throw HTML5.DRAIN;
      return HTML5.EOF;
    } else {
      if(this.committed > this.data.length / 2) {
	// Sliiiide
	this.data = this.data.slice(this.committed);
	this.start = this.start - this.committed;
	this.committed = 0;
      }
    }
  },
  matchWhile: function(re) {
    if(this.eof && this.start >= this.data.length ) return '';
    var r = new RegExp("^"+re+"+");
    var m = r.exec(this.slice());
    if(m) {
      if(!this.eof && m[0].length == this.data.length - this.start) throw HTML5.DRAIN;
      this.advance(m[0].length);
      return m[0];
    } else {
      return '';
    }
  },
  matchUntil: function(re) {
    var m, s;
    s = this.slice();
    if(s === HTML5.EOF) {
      return '';
    } else if(m = new RegExp(re + (this.eof ? "|\0|$" : "|\0")).exec(this.slice())) {
      var t = this.data.slice(this.start, this.start + m.index);
      this.advance(m.index);
      return t.toString();
    } else {
      throw HTML5.DRAIN;
    }
  },
  append: function(data) {
    this.data += data;
  },
  shift: function(n) {
    if(!this.eof && this.start + n >= this.data.length) throw HTML5.DRAIN;
    if(this.eof && this.start >= this.data.length) return HTML5.EOF;
    var d = this.data.slice(this.start, this.start + n).toString();
    this.advance(Math.min(n, this.data.length - this.start));
    return d;
  },
  peek: function(n) {
    if(!this.eof && this.start + n >= this.data.length) throw HTML5.DRAIN;
    if(this.eof && this.start >= this.data.length) return HTML5.EOF;
    return this.data.slice(this.start, Math.min(this.start + n, this.data.length)).toString();
  },
  length: function() {
    return this.data.length - this.start - 1;
  },
  unget: function(d) {
    if(d === HTML5.EOF) return;
    this.start -= (d.length);
  },
  undo: function() {
    this.start = this.committed;
  },
  commit: function() {
    this.committed = this.start;
  }
};