private SerializableDfa <TResult> _build(IList <ISet <TResult> > languages, DfaAmbiguityResolver <TResult> ambiguityResolver)
{
var nfa = new Nfa <TResult>();
var nfaStartStates = new int[languages.Count];
for (var i = 0; i < languages.Count; ++i)
{
nfaStartStates[i] = nfa.AddState();
}
ambiguityResolver ??= DefaultAmbiguityResolver;
foreach (var patEntry in patterns)
{
var patList = patEntry.Value;
if (patList == null || patList.Count < 1)
{
continue;
}
var matchState = -1; //start state for matching this token
for (var i = 0; i < languages.Count; ++i)
{
if (!languages[i].Contains(patEntry.Key))
{
continue;
}
if (matchState < 0)
{
var acceptState = nfa.AddState(patEntry.Key); //final state accepting this token
if (patList.Count > 1)
{
//we have multiple patterns. Make a union
matchState = nfa.AddState();
foreach (var pat in patList)
{
nfa.AddEpsilon(matchState, pat.AddToNfa(nfa, acceptState));
}
}
else
{
//only one pattern no union necessary
matchState = patList[0].AddToNfa(nfa, acceptState);
}
}
//language i matches these patterns
nfa.AddEpsilon(nfaStartStates[i], matchState);
}
}
var rawDfa = new DfaFromNfa <TResult>(nfa, nfaStartStates, ambiguityResolver).GetDfa();
var minimalDfa = new DfaMinimizer <TResult>(rawDfa).GetMinimizedDfa();
var serializableDfa = new SerializableDfa <TResult>(minimalDfa);
return(serializableDfa);
}
private SerializableDfa <bool> _buildReverseFinders(IList <ISet <TResult> > languages)
{
var nfa = new Nfa <bool>();
var startState = nfa.AddState();
var endState = nfa.AddState(true);
DfaAmbiguityResolver <bool> ambiguityResolver = DefaultAmbiguityResolver;
//First, make an NFA that matches the reverse of all the patterns
foreach (var patEntry in patterns)
{
var patList = patEntry.Value;
if (patList == null || patList.Count < 1)
{
continue;
}
foreach (var language in languages)
{
if (!language.Contains(patEntry.Key))
{
continue;
}
foreach (var pat in patEntry.Value)
{
var st = pat.Reversed.AddToNfa(nfa, endState);
nfa.AddEpsilon(startState, st);
}
}
}
//omit the empty string
startState = nfa.Disemptify(startState);
//allow anything first
startState = Pattern.MaybeRepeat(CharRange.All).AddToNfa(nfa, startState);
//build the DFA
var rawDfa = new DfaFromNfa <bool>(nfa, new[] { startState }, ambiguityResolver).GetDfa();
var minimalDfa = new DfaMinimizer <bool>(rawDfa).GetMinimizedDfa();
var serializableDfa = new SerializableDfa <bool>(minimalDfa);
return(serializableDfa);
}
/// <summary>
/// Build DFAs from a provided NFA
///
/// This method is used when you want to build the NFA yourself instead of letting this class do it.
///
/// Languages built simultaneously will be globally minimized and will share as many states as possible.
/// </summary>
/// <param name="nfa">The NFA</param>
/// <param name="nfaStartStates">The return value will include the DFA states corresponding to these NFA states, in the same order</param>
/// <param name="ambiguityResolver">When patterns for multiple results match the same string, this is called to
/// combine the multiple results into one. If this is null, then a DfaAmbiguityException will be thrown in that case.</param>
/// <param name="cache">If this cache is non-null, it will be checked for a memoized result for this NFA, and will be populated
/// with a memoized result when the call is complete.</param>
/// <returns>DFA start states that are equivalent to the given NFA start states. This will have the same length as nfaStartStates, with
/// corresponding start states in corresponding positions.</returns>
public static IList <DfaState <TResult> > BuildFromNfa(Nfa <TResult> nfa, int[] nfaStartStates, DfaAmbiguityResolver <TResult> ambiguityResolver,
IBuilderCache cache)
{
string cacheKey = null;
SerializableDfa <TResult> serializableDfa = null;
if (cache != null)
{
var hashAlg = new SHA256Managed();
using (var ms = new MemoryStream())
{
using var cs = new CryptoStream(ms, hashAlg, CryptoStreamMode.Write);
var bf = new BinaryFormatter();
bf.Serialize(ms, nfaStartStates);
bf.Serialize(ms, nfa);
bf.Serialize(ms, ambiguityResolver);
ms.Flush();
cs.FlushFinalBlock();
cacheKey = Base32.GetDigest(hashAlg.Hash);
}
serializableDfa = (SerializableDfa <TResult>)cache.GetCachedItem(cacheKey);
}
if (serializableDfa == null)
{
var rawDfa = new DfaFromNfa <TResult>(nfa, nfaStartStates, ambiguityResolver).GetDfa();
var minimalDfa = new DfaMinimizer <TResult>(rawDfa).GetMinimizedDfa();
serializableDfa = new SerializableDfa <TResult>(minimalDfa);
if (cacheKey != null)
{
cache.MaybeCacheItem(cacheKey, serializableDfa);
}
}
return(serializableDfa.GetStartStates());
}
