/
IronJSONParser.cs
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/
IronJSONParser.cs
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using System;
using System.Text;
namespace IronJSON
{
internal class IronJSONParser
{
private IronJSONTokenStream m_tokenStream;
private IronJSONObject m_obj; // The final product after parsing.
public IronJSONParser(IronJSONTokenStream tokenStream)
{
m_tokenStream = tokenStream;
m_obj = null;
}
/// <summary>
/// Parse the token stream.
/// </summary>
public void Parse()
{
m_obj = ParseObject();
// Reset for future calculations.
m_tokenStream.Reset();
}
/// <summary>
/// Returns the result of parsing. Or null if nothing was ever
/// parsed.
/// </summary>
public IronJSONObject Obj
{
get
{
return m_obj;
}
}
/// <summary>
/// Parse an object.
/// </summary>
private IronJSONObject ParseObject()
{
IronJSONObject obj = new IronJSONObject();
VerifyToken(m_tokenStream.CurrentToken,
new TokenType[]{TokenType.LeftCurlyBracket});
// Skip the '{'
if (!m_tokenStream.ToNextToken())
throw ParseError("expected '}'");
while (!m_tokenStream.AtEnd() &&
m_tokenStream.CurrentToken.Type == TokenType.String)
{
// Save the string.
string id = m_tokenStream.CurrentToken.String;
m_tokenStream.ToNextToken(); // Skip the id.
// Skip the ':'
VerifyToken(m_tokenStream.CurrentToken, new TokenType[]{TokenType.Colon});
if (!m_tokenStream.ToNextToken())
throw ParseError("expected ':'");
// Parse the value.
obj[id] = ParseValue();
// Skip the ',' or '}'. Error if it's not either.
VerifyToken(m_tokenStream.CurrentToken,
new TokenType[]{TokenType.Comma, TokenType.RightCurlyBracket});
if (!m_tokenStream.ToNextToken())
break;
// If what we skipped what a '}', break.
if (m_tokenStream.PreviousToken.Type == TokenType.RightCurlyBracket)
break;
}
return obj;
}
/// <summary>
/// Parse a value.
/// </summary>
/// <returns>
/// A <see cref="IronJSONValue"/>
/// </returns>
private IronJSONValue ParseValue()
{
switch (m_tokenStream.CurrentToken.Type)
{
case TokenType.String:
m_tokenStream.ToNextToken();
return new IronJSONValue(m_tokenStream.PreviousToken.String);
case TokenType.Float:
m_tokenStream.ToNextToken();
return new IronJSONValue(m_tokenStream.PreviousToken.Float);
case TokenType.Integer:
m_tokenStream.ToNextToken();
return new IronJSONValue(m_tokenStream.PreviousToken.Integer);
case TokenType.True:
m_tokenStream.ToNextToken();
return new IronJSONValue(ValueType.True);
case TokenType.False:
m_tokenStream.ToNextToken();
return new IronJSONValue(ValueType.False);
case TokenType.Null:
m_tokenStream.ToNextToken();
return new IronJSONValue(ValueType.Null);
case TokenType.LeftCurlyBracket:
return new IronJSONValue(ParseObject());
case TokenType.LeftSquareBracket:
return ParseList();
default:
throw ParseError("expected value got: " +
IronJSONToken.TokenTypeToString(m_tokenStream.CurrentToken.Type));
}
}
/// <summary>
/// Parses a list.
/// </summary>
/// <returns>
/// A <see cref="IronJSONValue"/>
/// </returns>
private IronJSONValue ParseList()
{
IronJSONValue val = new IronJSONValue(ValueType.Array);
VerifyToken(m_tokenStream.CurrentToken,
new TokenType[]{TokenType.LeftSquareBracket});
// Skip the '['
if (!m_tokenStream.ToNextToken())
throw ParseError("expected ']'");
while (!m_tokenStream.AtEnd())
{
// If what we hit a ']', break.
if (m_tokenStream.CurrentToken.Type == TokenType.RightSquareBracket)
{
m_tokenStream.ToNextToken();
break;
}
// Parse the value.
val.Array.Add(ParseValue());
// Skip the ',' or ']'. Error if it's not either.
VerifyToken(m_tokenStream.CurrentToken,
new TokenType[]{TokenType.Comma, TokenType.RightSquareBracket});
if (!m_tokenStream.ToNextToken())
break;
// If what we hit a ']', break.
if (m_tokenStream.PreviousToken.Type == TokenType.RightSquareBracket)
break;
}
return val;
}
private void VerifyToken(IronJSONToken tok, TokenType[] verify)
{
StringBuilder errormsg = new StringBuilder("expected ");
bool verified = false;
foreach (TokenType t in verify)
{
errormsg.Append("'" + IronJSONToken.TokenTypeToString(t) + "' or ");
if (tok.Type == t)
verified = true;
}
if (verify.Length > 0)
errormsg.Remove(errormsg.Length - 4, 4);
errormsg.Append(" got: " + tok.ToString());
if (!verified)
throw ParseError(errormsg.ToString());
}
/// <summary>
/// Returns a parser error.
/// </summary>
/// <param name="message">
/// A <see cref="System.String"/>
/// </param>
/// <returns>
/// A <see cref="IronJSONException"/>
/// </returns>
private JSONException ParseError(string message)
{
return new JSONException("line " + m_tokenStream.GetLineNumber() + ": " + message);
}
}
}