event-only version of jsonparse

jsonparse.js

// Named constants with unique integer values
var C = {};
// Tokenizer States
var START   = C.START   = 0x11;
var TRUE1   = C.TRUE1   = 0x21;
var TRUE2   = C.TRUE2   = 0x22;
var TRUE3   = C.TRUE3   = 0x23;
var FALSE1  = C.FALSE1  = 0x31;
var FALSE2  = C.FALSE2  = 0x32;
var FALSE3  = C.FALSE3  = 0x33;
var FALSE4  = C.FALSE4  = 0x34;
var NULL1   = C.NULL1   = 0x41;
var NULL2   = C.NULL3   = 0x42;
var NULL3   = C.NULL2   = 0x43;
var NUMBER1 = C.NUMBER1 = 0x51;
var NUMBER2 = C.NUMBER2 = 0x52;
var NUMBER3 = C.NUMBER3 = 0x53;
var NUMBER4 = C.NUMBER4 = 0x54;
var NUMBER5 = C.NUMBER5 = 0x55;
var NUMBER6 = C.NUMBER6 = 0x56;
var NUMBER7 = C.NUMBER7 = 0x57;
var NUMBER8 = C.NUMBER8 = 0x58;
var STRING1 = C.STRING1 = 0x61;
var STRING2 = C.STRING2 = 0x62;
var STRING3 = C.STRING3 = 0x63;
var STRING4 = C.STRING4 = 0x64;
var STRING5 = C.STRING5 = 0x65;
var STRING6 = C.STRING6 = 0x66;

// Slow code to string converter (only used when throwing syntax errors)
function toknam(code) {
  var keys = Object.keys(C);
  for (var i = 0, l = keys.length; i < l; i++) {
    var key = keys[i];
    if (C[key] === code) { return key; }
  }
  return code && ("0x" + code.toString(16));
}

function SaxParser(callbacks) {
  this.callbacks = callbacks;

  this.state = START;

  // for string parsing
  this.string = undefined; // string data
  this.unicode = undefined; // unicode escapes

  // For number parsing
  this.negative = undefined;
  this.magnatude = undefined;
  this.position = undefined;
  this.exponent = undefined;
  this.negativeExponent = undefined;
}
var proto = SaxParser.prototype;
proto.charError = function (buffer, i) {
  this.callbacks.onError(new Error("Unexpected " + JSON.stringify(String.fromCharCode(buffer[i])) + " at position " + i + " in state " + toknam(this.state)));
};
proto.parse = function (buffer) {
  if (typeof buffer === "string") buffer = new Buffer(buffer);
  var n;
  for (var i = 0, l = buffer.length; i < l; i++) {
    switch (this.state) {
    case START:
      n = buffer[i];
      switch (n) {
      case 0x7b: // `{`
        this.callbacks.onStartObject();
        continue;
      case 0x7d: // `}`
        this.callbacks.onEndObject();
        continue;
      case 0x5b: // `[`
        this.callbacks.onStartArray();
        continue;
      case 0x5d: // `]`
        this.callbacks.onEndArray();
        continue;
      case 0x3a: // `:`
        this.callbacks.onColon();
        continue;
      case 0x2c: // `,`
        this.callbacks.onComma();
        continue;
      case 0x74: // `t`
        this.state = TRUE1;
        continue;
      case 0x66: // `f`
        this.state = FALSE1;
        continue;
      case 0x6e: // `n`
        this.state = NULL1;
        continue;
      case 0x22: // `"`
        this.string = "";
        this.state = STRING1;
        continue;
      case 0x2d: // `-`
        this.negative = true;
        this.state = NUMBER1;
        continue;
      case 0x30: // `0`
        this.magnatude = 0;
        this.state = NUMBER2;
        continue;
      }
      if (n > 0x30 && n < 0x40) { // 1-9
        this.magnatude = n - 0x30;
        this.state = NUMBER3;
        continue;
      }
      if (n === 0x20 || n === 0x09 || n === 0x0a || n === 0x0d) {
        continue; // whitespace
      }
      this.charError(buffer, i);
    case STRING1: // After open quote
      n = buffer[i];
      switch (n) {
      case 0x22: // `"`
        this.callbacks.onString(this.string);
        this.string = undefined;
        this.state = START;
        continue;
      case 0x5c: // `\`
        this.state = STRING2;
        continue;
      }
      if (n >= 0x20) {
        this.string += String.fromCharCode(n);
        continue;
      }
      this.charError(buffer, i);
    case STRING2: // After backslash
      n = buffer[i];
      switch (n) {
      case 0x22: this.string += "\""; this.state = STRING1; continue;
      case 0x5c: this.string += "\\"; this.state = STRING1; continue;
      case 0x2f: this.string += "\/"; this.state = STRING1; continue;
      case 0x62: this.string += "\b"; this.state = STRING1; continue;
      case 0x66: this.string += "\f"; this.state = STRING1; continue;
      case 0x6e: this.string += "\n"; this.state = STRING1; continue;
      case 0x72: this.string += "\r"; this.state = STRING1; continue;
      case 0x74: this.string += "\t"; this.state = STRING1; continue;
      case 0x75: this.unicode = ""; this.state = STRING3; continue;
      }
      this.charError(buffer, i);
    case STRING3: case STRING4: case STRING5: case STRING6: // unicode hex codes
      n = buffer[i];
      // 0-9 A-F a-f
      if ((n >= 0x30 && n < 0x40) || (n > 0x40 && n <= 0x46) || (n > 0x60 && n <= 0x66)) {
        this.unicode += String.fromCharCode(n);
        if (this.state++ === STRING6) {
          this.string += String.fromCharCode(parseInt(this.unicode, 16));
          this.unicode = undefined;
          this.state = STRING1;
        }
        continue;
      }
      this.charError(buffer, i);
    case NUMBER1: // after minus
      n = buffer[i];
      if (n === 0x30) { // `0`
        this.magnatude = 0;
        this.state = NUMBER2;
        continue;
      }
      if (n > 0x30 && n < 0x40) { // `1`-`9`
        this.magnatude = n - 0x30;
        this.state = NUMBER3;
        continue;
      }
      this.charError(buffer, i);
    case NUMBER2: // * After initial zero
      switch (buffer[i]) {
      case 0x2e: // .
        this.position = 0.1; this.state = NUMBER4; continue;
      case 0x65: case 0x45: // e/E
        this.exponent = 0; this.state = NUMBER6; continue;
      }
      this.finish();
      i--; // rewind to re-check this char
      continue;
    case NUMBER3: // * After digit (before period)
      n = buffer[i];
      switch (n) {
      case 0x2e: // .
        this.position = 0.1; this.state = NUMBER4; continue;
      case 0x65: case 0x45: // e/E
        this.exponent = 0; this.state = NUMBER6; continue;
      }
      if (n >= 0x30 && n < 0x40) { // 0-9
        this.magnatude = this.magnatude * 10 + (n - 0x30);
        continue;
      }
      this.finish();
      i--; // rewind to re-check
      continue;
    case NUMBER4: // After period
      n = buffer[i];
      if (n >= 0x30 && n < 0x40) { // 0-9
        this.magnatude += this.position * (n - 0x30);
        this.position /= 10;
        this.state = NUMBER5;
        continue;
      }
      this.charError(buffer, i);
    case NUMBER5: // * After digit (after period)
      n = buffer[i];
      if (n >= 0x30 && n < 0x40) { // 0-9
        this.magnatude += this.position * (n - 0x30);
        this.position /= 10;
        continue;
      }
      if (n === 0x65 || n === 0x45) { // E/e
        this.exponent = 0;
        this.state = NUMBER6;
        continue;
      }
      this.finish();
      i--; // rewind
      continue;
    case NUMBER6: // After E
      n = buffer[i];
      if (n === 0x2b || n === 0x2d) { // +/-
        if (n === 0x2d) { this.negativeExponent = true; }
        this.state = NUMBER7;
        continue;
      }
      if (n >= 0x30 && n < 0x40) {
        this.exponent = this.exponent * 10 + (n - 0x30);
        this.state = NUMBER8;
        continue;
      }
      this.charError(buffer, i);
    case NUMBER7: // After +/-
      n = buffer[i];
      if (n >= 0x30 && n < 0x40) { // 0-9
        this.exponent = this.exponent * 10 + (n - 0x30);
        this.state = NUMBER8;
        continue;
      }
      this.charError(buffer, i);
    case NUMBER8: // * After digit (after +/-)
      n = buffer[i];
      if (n >= 0x30 && n < 0x40) { // 0-9
        this.exponent = this.exponent * 10 + (n - 0x30);
        continue;
      }
      this.finish();
      i--;
      continue;
    case TRUE1: // r
      if (buffer[i] === 0x72) {
        this.state = TRUE2;
        continue;
      }
      this.charError(buffer, i);
    case TRUE2: // u
      if (buffer[i] === 0x75) {
        this.state = TRUE3;
        continue;
      }
      this.charError(buffer, i);
    case TRUE3: // e
      if (buffer[i] === 0x65) {
        this.state = START;
        this.callbacks.onBoolean(true);
        continue;
      }
      this.charError(buffer, i);
    case FALSE1: // a
      if (buffer[i] === 0x61) {
        this.state = FALSE2;
        continue;
      }
      this.charError(buffer, i);
    case FALSE2: // l
      if (buffer[i] === 0x6c) {
        this.state = FALSE3;
        continue;
      }
      this.charError(buffer, i);
    case FALSE3: // s
      if (buffer[i] === 0x73) {
        this.state = FALSE4;
        continue;
      }
      this.charError(buffer, i);
    case FALSE4: // e
      if (buffer[i] === 0x65) {
        this.state = START;
        this.callbacks.onBoolean(false);
        continue;
      }
      this.charError(buffer, i);
    case NULL1: // u
      if (buffer[i] === 0x75) {
        this.state = NULL2;
        continue;
      }
      this.charError(buffer, i);
    case NULL2: // l
      if (buffer[i] === 0x6c) {
        this.state = NULL3;
        continue;
      }
      this.charError(buffer, i);
    case NULL3: // l
      if (buffer[i] === 0x6c) {
        this.state = START;
        this.callbacks.onNull();
        continue;
      }
      this.charError(buffer, i);
    }
  }
};

proto.finish = function () {
  switch (this.state) {
  case NUMBER2: // * After initial zero
    this.callbacks.onNumber(0);
    this.state = START;
    this.magnatude = undefined;
    this.negative = undefined;
    break;
  case NUMBER3: // * After digit (before period)
    this.state = START;
    if (this.negative) {
      this.magnatude = -this.magnatude;
      this.negative = undefined;
    }
    this.callbacks.onNumber(this.magnatude);
    this.magnatude = undefined;
    break;
  case NUMBER5: // * After digit (after period)
    this.state = START;
    if (this.negative) {
      this.magnatude = -this.magnatude;
      this.negative = undefined;
    }
    this.callbacks.onNumber(this.negative ? -this.magnatude : this.magnatude);
    this.magnatude = undefined;
    this.position = undefined;
    break;
  case NUMBER8: // * After digit (after +/-)
    if (this.negativeExponent) {
      this.exponent = -this.exponent;
      this.negativeExponent = undefined;
    }
    this.magnatude *= Math.pow(10, this.exponent);
    this.exponent = undefined;
    if (this.negative) {
      this.magnatude = -this.magnatude;
      this.negative = undefined;
    }
    this.state = START;
    this.callbacks.onNumber(this.magnatude);
    this.magnatude = undefined;
    break;
  }
  if (this.state !== START) {
    this.callbacks.onError(new Error("Unexpected end of input stream"));
  }
}

exports.SaxParser = SaxParser;

test-sax.js

var SaxParser = require('./jsonparse').SaxParser;

var p = new SaxParser({
  onNull: function () {
    console.log("onNull");
  },
  onBoolean: function (value) {
    console.log("onBoolean", value);
  },
  onNumber: function (value) {
    console.log("onNumber", value);
  },
  onString: function (value) {
    console.log("onString", value);
  },
  onStartObject: function () {
    console.log("onStartObject");
  },
  onColon: function () {
    console.log("onColon");
  },
  onComma: function () {
    console.log("onComma");
  },
  onEndObject: function () {
    console.log("onEndObject");
  },
  onStartArray: function () {
    console.log("onStartArray");
  },
  onEndArray: function () {
    console.log("onEndArray");
  }
});

//var stream = require('fs').createReadStream(__dirname + "/tests/sample.json");
//var parse = p.parse.bind(p);
//stream.on('data', parse);
//p.parse(new Buffer("{}"));
//p.parse(new Buffer("[]"));
//p.parse(new Buffer('"Hello"'));
p.parse(new Buffer("[1,2,3]"));
p.parse(new Buffer("-0.1e-3"));
p.parse(new Buffer('"Hello"'));
p.finish()
//p.parse(new Buffer('{"name":"tim"}'))

Is the null numbering on purpose?

var NULL2   = C.NULL3   = 0x42;
var NULL3   = C.NULL2   = 0x43;

NULL2 equals C.NULL3
NULL3 equals C.NULL2

this is cool, but how do I use it? Right now I am using JSONStream...but I am wondering if there is a way to use this module directly. Dunno, cuz there are no examples that I see. Nice code though :)