streaming-json-parser
Version:
A streaming JSON parser
495 lines (480 loc) • 15.3 kB
JavaScript
/*global Buffer*/
// Named constants with unique integer values
var C = {};
// Tokens
var LEFT_BRACE = C.LEFT_BRACE = 0x1;
var RIGHT_BRACE = C.RIGHT_BRACE = 0x2;
var LEFT_BRACKET = C.LEFT_BRACKET = 0x3;
var RIGHT_BRACKET = C.RIGHT_BRACKET = 0x4;
var COLON = C.COLON = 0x5;
var COMMA = C.COMMA = 0x6;
var TRUE = C.TRUE = 0x7;
var FALSE = C.FALSE = 0x8;
var NULL = C.NULL = 0x9;
var STRING = C.STRING = 0xa;
var NUMBER = C.NUMBER = 0xb;
// 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;
// Parser States
var VALUE = C.VALUE = 0x71;
var KEY = C.KEY = 0x72;
// Parser Modes
var OBJECT = C.OBJECT = 0x81;
var ARRAY = C.ARRAY = 0x82;
// 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 Parser(path) {
this.path = path;
this.skip = false;
this.skipStack = 0;
this.tState = START;
this.value = undefined;
// string data
this.string = undefined;
// unicode escapes
this.unicode = undefined;
// For number parsing
this.negative = undefined;
this.magnatude = undefined;
this.position = undefined;
this.exponent = undefined;
this.negativeExponent = undefined;
this.key = undefined;
this.mode = undefined;
this.stack = [];
this.state = VALUE;
}
var proto = Parser.prototype;
proto.charError = function (buffer, i) {
this.onError(new Error("Unexpected " + JSON.stringify(String.fromCharCode(buffer[i])) + " at position " + i + " in state " + toknam(this.tState)));
};
proto.onError = function (err) { throw err; };
proto.write = function (buffer) {
var n;
for (var i = 0, l = buffer.length; i < l; i++) {
if (this.skip) {
n = buffer[i];
if (this.tState === STRING2) {
this.tState = STRING1;
} else if (this.tState === STRING1) {
if (n === 0x22) {
this.tState = START;
} else if (n === 0x5c) {
this.tState = STRING2;
}
} else if (n === 0x22) {
this.tState = STRING1;
} else if (n === 0x7b || n === 0x5b) {
this.skipStack++;
} else if (this.skipStack && (n === 0x7d || n === 0x5d)) {
this.skipStack--;
} else if (!this.skipStack && (n === 0x7d || n === 0x5d || n === 0x2c)) {
this.skip = false;
this.state = COMMA;
if (n === 0x7d) {
this.onToken(RIGHT_BRACE, "}");
} else if (n === 0x5d) {
this.onToken(RIGHT_BRACKET, "]");
} else if (n === 0x2c) {
this.onToken(COMMA, ",");
}
}
continue;
}
switch (this.tState) {
case START:
n = buffer[i];
switch (n) {
case 0x7b: this.onToken(LEFT_BRACE, "{"); break; // {
case 0x7d: this.onToken(RIGHT_BRACE, "}"); break; // }
case 0x5b: this.onToken(LEFT_BRACKET, "["); break; // [
case 0x5d: this.onToken(RIGHT_BRACKET, "]"); break; // ]
case 0x3a: this.onToken(COLON, ":"); break; // :
case 0x2c: this.onToken(COMMA, ","); break; // ,
case 0x74: this.tState = TRUE1; break; // t
case 0x66: this.tState = FALSE1; break; // f
case 0x6e: this.tState = NULL1; break; // n
case 0x22: this.string = ""; this.tState = STRING1; break; // "
case 0x2d: this.negative = true; this.tState = NUMBER1; break; // -
case 0x30: this.magnatude = 0; this.tState = NUMBER2; break; // 0
default:
if (n > 0x30 && n < 0x40) { // 1-9
this.magnatude = n - 0x30; this.tState = NUMBER3;
} else if (n === 0x20 || n === 0x09 || n === 0x0a || n === 0x0d) {
// whitespace
} else { this.charError(buffer, i); }
break;
}
break;
case STRING1: // After open quote
n = buffer[i];
// TODO: Handle native utf8 characters, this code assumes ASCII input
if (n === 0x22) { // We just finished the string
this.tState = START;
this.onToken(STRING, this.string);
this.string = undefined;
}
else if (n === 0x5c) { this.tState = STRING2; }
else if (n >= 0x20) { this.string += String.fromCharCode(n); }
else { this.charError(buffer, i); }
break;
case STRING2: // After backslash
n = buffer[i];
switch (n) {
case 0x22: this.string += "\""; this.tState = STRING1; break;
case 0x5c: this.string += "\\"; this.tState = STRING1; break;
case 0x2f: this.string += "\/"; this.tState = STRING1; break;
case 0x62: this.string += "\b"; this.tState = STRING1; break;
case 0x66: this.string += "\f"; this.tState = STRING1; break;
case 0x6e: this.string += "\n"; this.tState = STRING1; break;
case 0x72: this.string += "\r"; this.tState = STRING1; break;
case 0x74: this.string += "\t"; this.tState = STRING1; break;
case 0x75: this.unicode = ""; this.tState = STRING3; break;
default: this.charError(buffer, i); break;
}
break;
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.tState++ === STRING6) {
this.string += String.fromCharCode(parseInt(this.unicode, 16));
this.unicode = undefined;
this.tState = STRING1;
}
} else {
this.charError(buffer, i);
}
break;
case NUMBER1: // after minus
n = buffer[i];
if (n === 0x30) { this.magnatude = 0; this.tState = NUMBER2; }
else if (n > 0x30 && n < 0x40) { this.magnatude = n - 0x30; this.tState = NUMBER3; }
else { this.charError(buffer, i); }
break;
case NUMBER2: // * After initial zero
switch (buffer[i]) {
case 0x2e: // .
this.position = 0.1; this.tState = NUMBER4; break;
case 0x65: case 0x45: // e/E
this.exponent = 0; this.tState = NUMBER6; break;
default:
this.tState = START;
this.onToken(NUMBER, 0);
this.magnatude = undefined;
this.negative = undefined;
i--;
break;
}
break;
case NUMBER3: // * After digit (before period)
n = buffer[i];
switch (n) {
case 0x2e: // .
this.position = 0.1; this.tState = NUMBER4; break;
case 0x65: case 0x45: // e/E
this.exponent = 0; this.tState = NUMBER6; break;
default:
if (n >= 0x30 && n < 0x40) { this.magnatude = this.magnatude * 10 + n - 0x30; }
else {
this.tState = START;
if (this.negative) {
this.magnatude = -this.magnatude;
this.negative = undefined;
}
this.onToken(NUMBER, this.magnatude);
this.magnatude = undefined;
i--;
}
break;
}
break;
case NUMBER4: // After period
n = buffer[i];
if (n >= 0x30 && n < 0x40) { // 0-9
this.magnatude += this.position * (n - 0x30);
this.position /= 10;
this.tState = NUMBER5;
} else { this.charError(buffer, i); }
break;
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;
}
else if (n === 0x65 || n === 0x45) { this.exponent = 0; this.tState = NUMBER6; } // E/e
else {
this.tState = START;
if (this.negative) {
this.magnatude = -this.magnatude;
this.negative = undefined;
}
this.onToken(NUMBER, this.negative ? -this.magnatude : this.magnatude);
this.magnatude = undefined;
this.position = undefined;
i--;
}
break;
case NUMBER6: // After E
n = buffer[i];
if (n === 0x2b || n === 0x2d) { // +/-
if (n === 0x2d) { this.negativeExponent = true; }
this.tState = NUMBER7;
}
else if (n >= 0x30 && n < 0x40) {
this.exponent = this.exponent * 10 + (n - 0x30);
this.tState = NUMBER8;
}
else { this.charError(buffer, i); }
break;
case NUMBER7: // After +/-
n = buffer[i];
if (n >= 0x30 && n < 0x40) { // 0-9
this.exponent = this.exponent * 10 + (n - 0x30);
this.tState = NUMBER8;
}
else { this.charError(buffer, i); }
break;
case NUMBER8: // * After digit (after +/-)
n = buffer[i];
if (n >= 0x30 && n < 0x40) { // 0-9
this.exponent = this.exponent * 10 + (n - 0x30);
}
else {
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.tState = START;
this.onToken(NUMBER, this.magnatude);
this.magnatude = undefined;
i--;
}
break;
case TRUE1: // r
if (buffer[i] === 0x72) { this.tState = TRUE2; }
else { this.charError(buffer, i); }
break;
case TRUE2: // u
if (buffer[i] === 0x75) { this.tState = TRUE3; }
else { this.charError(buffer, i); }
break;
case TRUE3: // e
if (buffer[i] === 0x65) { this.tState = START; this.onToken(TRUE, true); }
else { this.charError(buffer, i); }
break;
case FALSE1: // a
if (buffer[i] === 0x61) { this.tState = FALSE2; }
else { this.charError(buffer, i); }
break;
case FALSE2: // l
if (buffer[i] === 0x6c) { this.tState = FALSE3; }
else { this.charError(buffer, i); }
break;
case FALSE3: // s
if (buffer[i] === 0x73) { this.tState = FALSE4; }
else { this.charError(buffer, i); }
break;
case FALSE4: // e
if (buffer[i] === 0x65) { this.tState = START; this.onToken(FALSE, false); }
else { this.charError(buffer, i); }
break;
case NULL1: // u
if (buffer[i] === 0x75) { this.tState = NULL2; }
else { this.charError(buffer, i); }
break;
case NULL2: // l
if (buffer[i] === 0x6c) { this.tState = NULL3; }
else { this.charError(buffer, i); }
break;
case NULL3: // l
if (buffer[i] === 0x6c) { this.tState = START; this.onToken(NULL, null); }
else { this.charError(buffer, i); }
break;
}
}
};
proto.parseError = function (token, value) {
this.onError(
new Error(
"Unexpected " +
toknam(token) +
(value ?
("(" + JSON.stringify(value) + ")") :
""
) + " in state " + toknam(this.state)));
};
proto.onError = function (err) { throw err; };
proto.push = function () {
this.stack.push({ value: this.value, key: this.key, mode: this.mode });
};
proto.pop = function () {
var value = this.value;
var parent = this.stack.pop();
this.value = parent.value;
this.key = parent.key;
this.mode = parent.mode;
this.emit(value);
if (!this.mode) { this.state = VALUE; }
};
proto.emit = function (value) {
if (this.mode) { this.state = COMMA; }
if (this.stack.length === this.path.length) {
this.onValue(value);
}
};
proto.onValue = function (value) {
};
proto.onToken = function (token, value) {
switch (this.state) {
case VALUE:
switch (token) {
case STRING: case NUMBER: case TRUE: case FALSE: case NULL:
if (this.value) {
this.value[this.key] = value;
}
this.emit(value);
break;
case LEFT_BRACE:
this.push();
if (this.stack.length >= this.path.length) {
if (this.value) {
this.value = this.value[this.key] = {};
} else {
this.value = {};
}
}
this.key = undefined;
this.state = KEY;
this.mode = OBJECT;
break;
case LEFT_BRACKET:
this.push();
if (this.stack.length >= this.path.length) {
if (this.value) {
this.value = this.value[this.key] = [];
} else {
this.value = [];
}
}
this.mode = ARRAY;
this.key = 0;
if (this.check()) {
this.state = VALUE;
} else {
this.skip = true;
}
break;
case RIGHT_BRACE:
if (this.mode === OBJECT) {
this.pop();
} else {
this.parseError(token, value);
}
break;
case RIGHT_BRACKET:
if (this.mode === ARRAY) {
this.pop();
} else {
this.parseError(token, value);
}
break;
default:
this.parseError(token, value); break;
}
break;
case KEY:
if (token === STRING) {
this.key = value;
if (this.check()) {
this.state = COLON;
} else {
this.skip = true;
}
} else if (token === RIGHT_BRACE) {
this.pop();
} else {
this.parseError(token, value);
}
break;
case COLON:
if (token === COLON) { this.state = VALUE; }
else { this.parseError(token, value); }
break;
case COMMA:
if (token === COMMA) {
if (this.mode === ARRAY) {
this.key++;
if (this.check()) {
this.state = VALUE;
} else {
this.skip = true;
this.state = COMMA;
}
}
else if (this.mode === OBJECT) {
this.state = KEY;
}
} else if (token === RIGHT_BRACKET &&
this.mode === ARRAY ||
token === RIGHT_BRACE &&
this.mode === OBJECT) {
this.pop();
} else {
this.parseError(token, value);
}
break;
default:
this.parseError(token, value);
}
};
proto.check = function () {
var x = this.path[this.stack.length - 1],
y = this.key;
if (x === undefined) return true;
if ('string' === typeof x) return y === x;
if (x && 'function' === typeof x.exec) return x.exec(y);
if ('boolean' === typeof x) return x;
if ('function' === typeof x) return x(y);
return false;
};
module.exports = Parser;