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Tokenizer.cs
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189 lines (150 loc) · 3.49 KB
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using System.Diagnostics.Contracts;
using System.Globalization;
using System.IO;
using System.Text;
namespace ReClassNET.AddressParser
{
/// <summary>
/// Parses the given text and reads individual tokens from it.
/// </summary>
public class Tokenizer : ITokenizer
{
private readonly TextReader reader;
private char currentCharacter;
public Token Token { get; private set; }
public string Identifier { get; private set; }
public long Number { get; private set; }
public Tokenizer(TextReader reader)
{
Contract.Requires(reader != null);
this.reader = reader;
ReadNextCharacter();
ReadNextToken();
}
public void ReadNextToken()
{
SkipWhitespaces();
if (currentCharacter == '\0')
{
Token = Token.None;
Identifier = null;
Number = 0;
return;
}
if (TryReadSimpleToken())
{
ReadNextCharacter();
return;
}
if (TryReadNumberToken())
{
return;
}
if (TryReadIdentifierToken())
{
return;
}
throw new ParseException($"Invalid character '{currentCharacter}'.");
}
private void ReadNextCharacter()
{
var c = reader.Read();
currentCharacter = c < 0 ? '\0' : (char)c;
}
private void SkipWhitespaces()
{
while (char.IsWhiteSpace(currentCharacter))
{
ReadNextCharacter();
}
}
private bool TryReadSimpleToken()
{
switch (currentCharacter)
{
case '+':
Token = Token.Add;
return true;
case '-':
Token = Token.Subtract;
return true;
case '*':
Token = Token.Multiply;
return true;
case '/':
Token = Token.Divide;
return true;
case '(':
Token = Token.OpenParenthesis;
return true;
case ')':
Token = Token.CloseParenthesis;
return true;
case '[':
Token = Token.OpenBrackets;
return true;
case ']':
Token = Token.CloseBrackets;
return true;
case ',':
Token = Token.Comma;
return true;
}
return false;
}
private bool TryReadNumberToken()
{
bool IsHexadecimalDigit(char c) => char.IsDigit(c) || 'a' <= c && c <= 'f' || 'A' <= c && c <= 'F';
bool IsHexadecimalIdentifier(char c) => c == 'x' || c == 'X';
if (IsHexadecimalDigit(currentCharacter))
{
var sb = new StringBuilder();
var hasHexadecimalIdentifier = false;
while (IsHexadecimalDigit(currentCharacter)
|| IsHexadecimalIdentifier(currentCharacter) && !hasHexadecimalIdentifier && sb.Length == 1 && sb[0] == '0')
{
sb.Append(currentCharacter);
if (!hasHexadecimalIdentifier)
{
hasHexadecimalIdentifier = IsHexadecimalIdentifier(currentCharacter);
}
ReadNextCharacter();
}
if (hasHexadecimalIdentifier)
{
sb.Remove(0, 2);
}
if (!long.TryParse(sb.ToString(), NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var number))
{
throw new ParseException($"Could not parse '{sb}' as number.");
}
Number = number;
Token = Token.Number;
return true;
}
return false;
}
private bool TryReadIdentifierToken()
{
if (currentCharacter == '<')
{
ReadNextCharacter();
var sb = new StringBuilder();
while (currentCharacter != '\0' && currentCharacter != '>')
{
sb.Append(currentCharacter);
ReadNextCharacter();
}
if (currentCharacter != '>')
{
throw new ParseException("Invalid identifier, missing '>'.");
}
ReadNextCharacter();
Identifier = sb.ToString();
Token = Token.Identifier;
return true;
}
return false;
}
}
}