/// <summary>
/// 使用指定的语法规则初始化 <see cref="Cyjb.Compilers.Lexers.LexerRule<T>"/> 类的新实例。
/// </summary>
/// <param name="grammar">词法分析器使用的语法规则。</param>
internal LexerRule(Grammar <T> grammar)
{
if (grammar == null)
{
throw CommonExceptions.ArgumentNull("grammar");
}
this.contextCount = grammar.Contexts.Count;
this.contexts = new Dictionary <string, int>(contextCount);
int i = 0;
foreach (string context in grammar.Contexts)
{
this.contexts.Add(context, i++);
}
this.symbolCount = grammar.Terminals.Count;
this.symbols = new SymbolData <T> [this.symbolCount];
foreach (Terminal <T> sym in grammar.Terminals)
{
this.symbols[sym.Index] = new SymbolData <T>(sym.Id, sym.Action);
}
FillEOFActions(grammar);
bool useTrailing;
FillDfa(grammar, out useTrailing);
if (useTrailing)
{
FillTrailing(grammar);
}
else
{
this.trailingType = TrailingType.None;
}
this.ContainsBeginningOfLineHeader = true;
}
/// <summary>
/// 填充行首匹配和向前看的数据。
/// </summary>
/// <param name="grammar">词法分析器使用的语法。</param>
private void FillTrailing(Grammar <T> grammar)
{
bool variableTrailing = false;
this.containsBeginningOfLineRule = false;
foreach (Terminal <T> sym in grammar.Terminals)
{
AnchorExp exp = sym.RegularExpression as AnchorExp;
if (exp != null)
{
if (exp.BeginningOfLine == true)
{
this.containsBeginningOfLineRule = true;
}
if (exp.TrailingExpression != null)
{
int len = exp.TrailingExpression.Length;
if (len != -1)
{
this.symbols[sym.Index].Trailing = -len;
}
else
{
len = exp.InnerExpression.Length;
if (len != -1)
{
this.symbols[sym.Index].Trailing = len;
}
else
{
this.symbols[sym.Index].Trailing = 0;
variableTrailing = true;
}
}
}
}
}
if (variableTrailing)
{
this.trailingType = TrailingType.Variable;
}
else
{
this.trailingType = TrailingType.Fixed;
}
}
