HospitalBrowser/Browser/JsonParser.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.Text;

internal class JsonParser
{
	private enum Token
	{
		None = -1,
		Curly_Open,
		Curly_Close,
		Squared_Open,
		Squared_Close,
		Colon,
		Comma,
		String,
		Number,
		True,
		False,
		Null
	}

	private readonly char[] json;

	private readonly StringBuilder s = new StringBuilder();

	private Token lookAheadToken = Token.None;

	private int index;

	private bool _ignorecase = false;

	internal JsonParser(string json, bool ignorecase)
	{
		this.json = json.ToCharArray();
		_ignorecase = ignorecase;
	}

	public object Decode()
	{
		return ParseValue();
	}

	private Dictionary<string, object> ParseObject()
	{
		Dictionary<string, object> table = new Dictionary<string, object>();
		ConsumeToken();
		while (true)
		{
			switch (LookAhead())
			{
			case Token.Comma:
				ConsumeToken();
				continue;
			case Token.Curly_Close:
				ConsumeToken();
				return table;
			}
			string name = ParseString();
			if (_ignorecase)
			{
				name = name.ToLower();
			}
			if (NextToken() != Token.Colon)
			{
				throw new Exception("Expected colon at index " + index);
			}
			object value = (table[name] = ParseValue());
		}
	}

	private ArrayList ParseArray()
	{
		ArrayList array = new ArrayList();
		ConsumeToken();
		while (true)
		{
			switch (LookAhead())
			{
			case Token.Comma:
				ConsumeToken();
				break;
			case Token.Squared_Close:
				ConsumeToken();
				return array;
			default:
				array.Add(ParseValue());
				break;
			}
		}
	}

	private object ParseValue()
	{
		switch (LookAhead())
		{
		case Token.Number:
			return ParseNumber();
		case Token.String:
			return ParseString();
		case Token.Curly_Open:
			return ParseObject();
		case Token.Squared_Open:
			return ParseArray();
		case Token.True:
			ConsumeToken();
			return true;
		case Token.False:
			ConsumeToken();
			return false;
		case Token.Null:
			ConsumeToken();
			return null;
		default:
			throw new Exception("Unrecognized token at index" + index);
		}
	}

	private string ParseString()
	{
		ConsumeToken();
		s.Length = 0;
		int runIndex = -1;
		while (index < json.Length)
		{
			switch (json[index++])
			{
			case '"':
				if (runIndex != -1)
				{
					if (s.Length == 0)
					{
						return new string(json, runIndex, index - runIndex - 1);
					}
					s.Append(json, runIndex, index - runIndex - 1);
				}
				return s.ToString();
			default:
				if (runIndex == -1)
				{
					runIndex = index - 1;
				}
				continue;
			case '\\':
				break;
			}
			if (index == json.Length)
			{
				break;
			}
			if (runIndex != -1)
			{
				s.Append(json, runIndex, index - runIndex - 1);
				runIndex = -1;
			}
			switch (json[index++])
			{
			case '"':
				s.Append('"');
				break;
			case '\\':
				s.Append('\\');
				break;
			case '/':
				s.Append('/');
				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':
			{
				int remainingLength = json.Length - index;
				if (remainingLength >= 4)
				{
					uint codePoint = ParseUnicode(json[index], json[index + 1], json[index + 2], json[index + 3]);
					s.Append((char)codePoint);
					index += 4;
				}
				break;
			}
			}
		}
		throw new Exception("Unexpectedly reached end of string");
	}

	private uint ParseSingleChar(char c1, uint multipliyer)
	{
		uint p1 = 0u;
		if (c1 >= '0' && c1 <= '9')
		{
			p1 = (uint)(c1 - 48) * multipliyer;
		}
		else if (c1 >= 'A' && c1 <= 'F')
		{
			p1 = (uint)(c1 - 65 + 10) * multipliyer;
		}
		else if (c1 >= 'a' && c1 <= 'f')
		{
			p1 = (uint)(c1 - 97 + 10) * multipliyer;
		}
		return p1;
	}

	private uint ParseUnicode(char c1, char c2, char c3, char c4)
	{
		uint p1 = ParseSingleChar(c1, 4096u);
		uint p2 = ParseSingleChar(c2, 256u);
		uint p3 = ParseSingleChar(c3, 16u);
		uint p4 = ParseSingleChar(c4, 1u);
		return p1 + p2 + p3 + p4;
	}

	private string ParseNumber()
	{
		ConsumeToken();
		int startIndex = index - 1;
		while (true)
		{
			char c = json[index];
			if ((c >= '0' && c <= '9') || c == '.' || c == '-' || c == '+' || c == 'e' || c == 'E')
			{
				if (++index == json.Length)
				{
					throw new Exception("Unexpected end of string whilst parsing number");
				}
				bool flag = true;
				continue;
			}
			break;
		}
		return new string(json, startIndex, index - startIndex);
	}

	private Token LookAhead()
	{
		if (lookAheadToken != Token.None)
		{
			return lookAheadToken;
		}
		return lookAheadToken = NextTokenCore();
	}

	private void ConsumeToken()
	{
		lookAheadToken = Token.None;
	}

	private Token NextToken()
	{
		Token result = ((lookAheadToken != Token.None) ? lookAheadToken : NextTokenCore());
		lookAheadToken = Token.None;
		return result;
	}

	private Token NextTokenCore()
	{
		char c;
		do
		{
			c = json[index];
		}
		while (c <= ' ' && (c == ' ' || c == '\t' || c == '\n' || c == '\r') && ++index < json.Length);
		if (index == json.Length)
		{
			throw new Exception("Reached end of string unexpectedly");
		}
		c = json[index];
		index++;
		switch (c)
		{
		case '{':
			return Token.Curly_Open;
		case '}':
			return Token.Curly_Close;
		case '[':
			return Token.Squared_Open;
		case ']':
			return Token.Squared_Close;
		case ',':
			return Token.Comma;
		case '"':
			return Token.String;
		case '+':
		case '-':
		case '.':
		case '0':
		case '1':
		case '2':
		case '3':
		case '4':
		case '5':
		case '6':
		case '7':
		case '8':
		case '9':
			return Token.Number;
		case ':':
			return Token.Colon;
		case 'f':
			if (json.Length - index >= 4 && json[index] == 'a' && json[index + 1] == 'l' && json[index + 2] == 's' && json[index + 3] == 'e')
			{
				index += 4;
				return Token.False;
			}
			break;
		case 't':
			if (json.Length - index >= 3 && json[index] == 'r' && json[index + 1] == 'u' && json[index + 2] == 'e')
			{
				index += 3;
				return Token.True;
			}
			break;
		case 'n':
			if (json.Length - index >= 3 && json[index] == 'u' && json[index + 1] == 'l' && json[index + 2] == 'l')
			{
				index += 3;
				return Token.Null;
			}
			break;
		}
		throw new Exception("Could not find token at index " + --index);
	}
}