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Unity3D: MiniJSON Decodes and encodes simple JSON strings. Not intended for use with massive JSON strings, probably < 32k preferred. Handy for parsing JSON from inside Unity3d.

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MiniJSON.cs
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/*
* Copyright (c) 2013 Calvin Rien
*
* Based on the JSON parser by Patrick van Bergen
* http://techblog.procurios.nl/k/618/news/view/14605/14863/How-do-I-write-my-own-parser-for-JSON.html
*
* Simplified it so that it doesn't throw exceptions
* and can be used in Unity iPhone with maximum code stripping.
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Text;
 
namespace MiniJSON {
// Example usage:
//
// using UnityEngine;
// using System.Collections;
// using System.Collections.Generic;
// using MiniJSON;
//
// public class MiniJSONTest : MonoBehaviour {
// void Start () {
// var jsonString = "{ \"array\": [1.44,2,3], " +
// "\"object\": {\"key1\":\"value1\", \"key2\":256}, " +
// "\"string\": \"The quick brown fox \\\"jumps\\\" over the lazy dog \", " +
// "\"unicode\": \"\\u3041 Men\u00fa sesi\u00f3n\", " +
// "\"int\": 65536, " +
// "\"float\": 3.1415926, " +
// "\"bool\": true, " +
// "\"null\": null }";
//
// var dict = Json.Deserialize(jsonString) as Dictionary<string,object>;
//
// Debug.Log("deserialized: " + dict.GetType());
// Debug.Log("dict['array'][0]: " + ((List<object>) dict["array"])[0]);
// Debug.Log("dict['string']: " + (string) dict["string"]);
// Debug.Log("dict['float']: " + (double) dict["float"]); // floats come out as doubles
// Debug.Log("dict['int']: " + (long) dict["int"]); // ints come out as longs
// Debug.Log("dict['unicode']: " + (string) dict["unicode"]);
//
// var str = Json.Serialize(dict);
//
// Debug.Log("serialized: " + str);
// }
// }
 
/// <summary>
/// This class encodes and decodes JSON strings.
/// Spec. details, see http://www.json.org/
///
/// JSON uses Arrays and Objects. These correspond here to the datatypes IList and IDictionary.
/// All numbers are parsed to doubles.
/// </summary>
public static class Json {
/// <summary>
/// Parses the string json into a value
/// </summary>
/// <param name="json">A JSON string.</param>
/// <returns>An List&lt;object&gt;, a Dictionary&lt;string, object&gt;, a double, an integer,a string, null, true, or false</returns>
public static object Deserialize(string json) {
// save the string for debug information
if (json == null) {
return null;
}
 
return Parser.Parse(json);
}
 
sealed class Parser : IDisposable {
const string WORD_BREAK = "{}[],:\"";
 
public static bool IsWordBreak(char c) {
return Char.IsWhiteSpace(c) || WORD_BREAK.IndexOf(c) != -1;
}
 
enum TOKEN {
NONE,
CURLY_OPEN,
CURLY_CLOSE,
SQUARED_OPEN,
SQUARED_CLOSE,
COLON,
COMMA,
STRING,
NUMBER,
TRUE,
FALSE,
NULL
};
 
StringReader json;
 
Parser(string jsonString) {
json = new StringReader(jsonString);
}
 
public static object Parse(string jsonString) {
using (var instance = new Parser(jsonString)) {
return instance.ParseValue();
}
}
 
public void Dispose() {
json.Dispose();
json = null;
}
 
Dictionary<string, object> ParseObject() {
Dictionary<string, object> table = new Dictionary<string, object>();
 
// ditch opening brace
json.Read();
 
// {
while (true) {
switch (NextToken) {
case TOKEN.NONE:
return null;
case TOKEN.COMMA:
continue;
case TOKEN.CURLY_CLOSE:
return table;
default:
// name
string name = ParseString();
if (name == null) {
return null;
}
 
// :
if (NextToken != TOKEN.COLON) {
return null;
}
// ditch the colon
json.Read();
 
// value
table[name] = ParseValue();
break;
}
}
}
 
List<object> ParseArray() {
List<object> array = new List<object>();
 
// ditch opening bracket
json.Read();
 
// [
var parsing = true;
while (parsing) {
TOKEN nextToken = NextToken;
 
switch (nextToken) {
case TOKEN.NONE:
return null;
case TOKEN.COMMA:
continue;
case TOKEN.SQUARED_CLOSE:
parsing = false;
break;
default:
object value = ParseByToken(nextToken);
 
array.Add(value);
break;
}
}
 
return array;
}
 
object ParseValue() {
TOKEN nextToken = NextToken;
return ParseByToken(nextToken);
}
 
object ParseByToken(TOKEN token) {
switch (token) {
case TOKEN.STRING:
return ParseString();
case TOKEN.NUMBER:
return ParseNumber();
case TOKEN.CURLY_OPEN:
return ParseObject();
case TOKEN.SQUARED_OPEN:
return ParseArray();
case TOKEN.TRUE:
return true;
case TOKEN.FALSE:
return false;
case TOKEN.NULL:
return null;
default:
return null;
}
}
 
string ParseString() {
StringBuilder s = new StringBuilder();
char c;
 
// ditch opening quote
json.Read();
 
bool parsing = true;
while (parsing) {
 
if (json.Peek() == -1) {
parsing = false;
break;
}
 
c = NextChar;
switch (c) {
case '"':
parsing = false;
break;
case '\\':
if (json.Peek() == -1) {
parsing = false;
break;
}
 
c = NextChar;
switch (c) {
case '"':
case '\\':
case '/':
s.Append(c);
break;
case 'b':
s.Append('\b');
break;
case 'f':
s.Append('\f');
break;
case 'n':
s.Append('\n');
break;
case 'r':
s.Append('\r');
break;
case 't':
s.Append('\t');
break;
case 'u':
var hex = new char[4];
 
for (int i=0; i< 4; i++) {
hex[i] = NextChar;
}
 
s.Append((char) Convert.ToInt32(new string(hex), 16));
break;
}
break;
default:
s.Append(c);
break;
}
}
 
return s.ToString();
}
 
object ParseNumber() {
string number = NextWord;
 
if (number.IndexOf('.') == -1) {
long parsedInt;
Int64.TryParse(number, out parsedInt);
return parsedInt;
}
 
double parsedDouble;
Double.TryParse(number, out parsedDouble);
return parsedDouble;
}
 
void EatWhitespace() {
while (Char.IsWhiteSpace(PeekChar)) {
json.Read();
 
if (json.Peek() == -1) {
break;
}
}
}
 
char PeekChar {
get {
return Convert.ToChar(json.Peek());
}
}
 
char NextChar {
get {
return Convert.ToChar(json.Read());
}
}
 
string NextWord {
get {
StringBuilder word = new StringBuilder();
 
while (!IsWordBreak(PeekChar)) {
word.Append(NextChar);
 
if (json.Peek() == -1) {
break;
}
}
 
return word.ToString();
}
}
 
TOKEN NextToken {
get {
EatWhitespace();
 
if (json.Peek() == -1) {
return TOKEN.NONE;
}
 
switch (PeekChar) {
case '{':
return TOKEN.CURLY_OPEN;
case '}':
json.Read();
return TOKEN.CURLY_CLOSE;
case '[':
return TOKEN.SQUARED_OPEN;
case ']':
json.Read();
return TOKEN.SQUARED_CLOSE;
case ',':
json.Read();
return TOKEN.COMMA;
case '"':
return TOKEN.STRING;
case ':':
return TOKEN.COLON;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
case '-':
return TOKEN.NUMBER;
}
 
switch (NextWord) {
case "false":
return TOKEN.FALSE;
case "true":
return TOKEN.TRUE;
case "null":
return TOKEN.NULL;
}
 
return TOKEN.NONE;
}
}
}
 
/// <summary>
/// Converts a IDictionary / IList object or a simple type (string, int, etc.) into a JSON string
/// </summary>
/// <param name="json">A Dictionary&lt;string, object&gt; / List&lt;object&gt;</param>
/// <returns>A JSON encoded string, or null if object 'json' is not serializable</returns>
public static string Serialize(object obj) {
return Serializer.Serialize(obj);
}
 
sealed class Serializer {
StringBuilder builder;
 
Serializer() {
builder = new StringBuilder();
}
 
public static string Serialize(object obj) {
var instance = new Serializer();
 
instance.SerializeValue(obj);
 
return instance.builder.ToString();
}
 
void SerializeValue(object value) {
IList asList;
IDictionary asDict;
string asStr;
 
if (value == null) {
builder.Append("null");
} else if ((asStr = value as string) != null) {
SerializeString(asStr);
} else if (value is bool) {
builder.Append((bool) value ? "true" : "false");
} else if ((asList = value as IList) != null) {
SerializeArray(asList);
} else if ((asDict = value as IDictionary) != null) {
SerializeObject(asDict);
} else if (value is char) {
SerializeString(new string((char) value, 1));
} else {
SerializeOther(value);
}
}
 
void SerializeObject(IDictionary obj) {
bool first = true;
 
builder.Append('{');
 
foreach (object e in obj.Keys) {
if (!first) {
builder.Append(',');
}
 
SerializeString(e.ToString());
builder.Append(':');
 
SerializeValue(obj[e]);
 
first = false;
}
 
builder.Append('}');
}
 
void SerializeArray(IList anArray) {
builder.Append('[');
 
bool first = true;
 
foreach (object obj in anArray) {
if (!first) {
builder.Append(',');
}
 
SerializeValue(obj);
 
first = false;
}
 
builder.Append(']');
}
 
void SerializeString(string str) {
builder.Append('\"');
 
char[] charArray = str.ToCharArray();
foreach (var c in charArray) {
switch (c) {
case '"':
builder.Append("\\\"");
break;
case '\\':
builder.Append("\\\\");
break;
case '\b':
builder.Append("\\b");
break;
case '\f':
builder.Append("\\f");
break;
case '\n':
builder.Append("\\n");
break;
case '\r':
builder.Append("\\r");
break;
case '\t':
builder.Append("\\t");
break;
default:
int codepoint = Convert.ToInt32(c);
if ((codepoint >= 32) && (codepoint <= 126)) {
builder.Append(c);
} else {
builder.Append("\\u");
builder.Append(codepoint.ToString("x4"));
}
break;
}
}
 
builder.Append('\"');
}
 
void SerializeOther(object value) {
// NOTE: decimals lose precision during serialization.
// They always have, I'm just letting you know.
// Previously floats and doubles lost precision too.
if (value is float) {
builder.Append(((float) value).ToString("R"));
} else if (value is int
|| value is uint
|| value is long
|| value is sbyte
|| value is byte
|| value is short
|| value is ushort
|| value is ulong) {
builder.Append(value);
} else if (value is double
|| value is decimal) {
builder.Append(Convert.ToDouble(value).ToString("R"));
} else {
SerializeString(value.ToString());
}
}
}
}
}

I found one nasty bug. When I serialize a double that is a whole number like 1, it writes it like 1. And when the parser wants to parse it it doesn't have '.' and it reads it as integer type. I suggest splitting the if on line 530 for ints and floats and then doing something like string.Format("0.0"); for the floats.

Other than that your mini json lib is very useful and I thank you for doing it :D

Can this work with 2 dimensional arrays?

Fixed the float, double, decimal issue where the serialiser saved it as "0" instead of "0.0"

In the Function SerializeOther at Line 529
I added an extra else if to handle float, double and decimal separately:

void SerializeOther(object value) {
if (value is int
|| value is uint
|| value is long
|| value is sbyte
|| value is byte
|| value is short
|| value is ushort
|| value is ulong) {
builder.Append(value.ToString());
}
else if (value is float
|| value is double
|| value is decimal)
{
builder.Append(string.Format("{0:F}", value));
}
else {
SerializeString(value.ToString());
}
}

Has anyone come across a bug where when it tries to serialize a dictionary, it instead makes the string into something like this?:
"SaveData":"{\"S\":null,\"y\":null,\"s\":null,\"t\":null,\"e\":null,\"m\":null,\".\":null,\"C\":null,\"o\":null,\"l\":null,\"l\":null,\"e\":null,\"c\":null,\"t\":null,\"i\":null,\"o\":null,\"n\":null,\"s\":null,\".\":null,\"G\":null,\"e\":null,\"n\":null,\"e\":null,\"r\":null,\"i\":null,\"c\":null,\".\":null,\"D\":null,\"i\":null,\"c\":null,\"t\":null,\"i\":null,\"o\":null,\"n\":null,\"a\":null,\"r\":null,\"y\":null,\"`\":null,\"2\":null,\"[\":null,\"S\":null,\"y\":null,\"s\":null,\"t\":null,\"e\":null,\"m\":null,\".\":null,\"S\":null,\"t\":null,\"r\":null,\"i\":null,\"n\":null,\"g\":null,\",\":null,\"S\":null,\"y\":null,\"s\":null,\"t\":null,\"e\":null,\"m\":null,\".\":null,\"O\":null,\"b\":null,\"j\":null,\"e\":null,\"c\":null,\"t\":null,\"]\":null}"

System.Collections.Generic.Dictionary`2[System.String,System.Object]

It's as if instead of grabbing the keys, it's grabbing each character of the type somehow. This appears to be happening randomly, working sometimes, but not others.

@tonyzahnle, I saw some similar issues using this and other JSON libraries. If you swap all the generic collections in this code for Hashtables and ArrayLists it will fix your issue. I think that Unity for iOS has some kind of problem with iterating over generic collections. More about the issue here, although their fix didn't completely solve it for me.

What exactly would be the problem with an extremely large json string? Im pretty sure we are using strings larger than that just fine...

This implementation currently generates and parses invalid JSON when the system locale is set to use comma instead of periods with decimal numbers. By instructing TryParse and ToString to ignore the user locale, this fixes the issue.
See: https://gist.github.com/elaberge/6536806

Apparently, the Mono runtime incorrectly handles the current locale and in most situations returns en-us or invariant, at least in the current Unity3D version (4.2.1) and earlier. https://bugzilla.xamarin.com/show_bug.cgi?id=2957

So number parsing and encoding is working by chance. If the Mono runtime is fixed, the code will be broken. You should consider @elaberge suggestions.

As a side note, I encourage you to replace foreach with a standard for when possible (check out my fork, for performance).

Great work by the way and thanks for sharing! :)

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