1 files changed, 173 insertions, 0 deletions
diff --git a/grammar/lexical/dfa/dfa.go b/grammar/lexical/dfa/dfa.go
new file mode 100644
index 0000000..850264a
--- /dev/null
+++ b/grammar/lexical/dfa/dfa.go
@@ -0,0 +1,173 @@
+package dfa
+
+import (
+	"sort"
+
+	spec "github.com/nihei9/vartan/spec/grammar"
+)
+
+type symbolTable struct {
+	symPos2Byte map[symbolPosition]byteRange
+	endPos2ID   map[symbolPosition]spec.LexModeKindID
+}
+
+func genSymbolTable(root byteTree) *symbolTable {
+	symTab := &symbolTable{
+		symPos2Byte: map[symbolPosition]byteRange{},
+		endPos2ID:   map[symbolPosition]spec.LexModeKindID{},
+	}
+	return genSymTab(symTab, root)
+}
+
+func genSymTab(symTab *symbolTable, node byteTree) *symbolTable {
+	if node == nil {
+		return symTab
+	}
+
+	switch n := node.(type) {
+	case *symbolNode:
+		symTab.symPos2Byte[n.pos] = byteRange{
+			from: n.from,
+			to:   n.to,
+		}
+	case *endMarkerNode:
+		symTab.endPos2ID[n.pos] = n.id
+	default:
+		left, right := node.children()
+		genSymTab(symTab, left)
+		genSymTab(symTab, right)
+	}
+	return symTab
+}
+
+type DFA struct {
+	States               []string
+	InitialState         string
+	AcceptingStatesTable map[string]spec.LexModeKindID
+	TransitionTable      map[string][256]string
+}
+
+func GenDFA(root byteTree, symTab *symbolTable) *DFA {
+	initialState := root.first()
+	initialStateHash := initialState.hash()
+	stateMap := map[string]*symbolPositionSet{
+		initialStateHash: initialState,
+	}
+	tranTab := map[string][256]string{}
+	{
+		follow := genFollowTable(root)
+		unmarkedStates := map[string]*symbolPositionSet{
+			initialStateHash: initialState,
+		}
+		for len(unmarkedStates) > 0 {
+			nextUnmarkedStates := map[string]*symbolPositionSet{}
+			for hash, state := range unmarkedStates {
+				tranTabOfState := [256]*symbolPositionSet{}
+				for _, pos := range state.set() {
+					if pos.isEndMark() {
+						continue
+					}
+					valRange := symTab.symPos2Byte[pos]
+					for symVal := valRange.from; symVal <= valRange.to; symVal++ {
+						if tranTabOfState[symVal] == nil {
+							tranTabOfState[symVal] = newSymbolPositionSet()
+						}
+						tranTabOfState[symVal].merge(follow[pos])
+					}
+				}
+				for _, t := range tranTabOfState {
+					if t == nil {
+						continue
+					}
+					h := t.hash()
+					if _, ok := stateMap[h]; ok {
+						continue
+					}
+					stateMap[h] = t
+					nextUnmarkedStates[h] = t
+				}
+				tabOfState := [256]string{}
+				for v, t := range tranTabOfState {
+					if t == nil {
+						continue
+					}
+					tabOfState[v] = t.hash()
+				}
+				tranTab[hash] = tabOfState
+			}
+			unmarkedStates = nextUnmarkedStates
+		}
+	}
+
+	accTab := map[string]spec.LexModeKindID{}
+	{
+		for h, s := range stateMap {
+			for _, pos := range s.set() {
+				if !pos.isEndMark() {
+					continue
+				}
+				priorID, ok := accTab[h]
+				if !ok {
+					accTab[h] = symTab.endPos2ID[pos]
+				} else {
+					id := symTab.endPos2ID[pos]
+					if id < priorID {
+						accTab[h] = id
+					}
+				}
+			}
+		}
+	}
+
+	var states []string
+	{
+		for s := range stateMap {
+			states = append(states, s)
+		}
+		sort.Slice(states, func(i, j int) bool {
+			return states[i] < states[j]
+		})
+	}
+
+	return &DFA{
+		States:               states,
+		InitialState:         initialStateHash,
+		AcceptingStatesTable: accTab,
+		TransitionTable:      tranTab,
+	}
+}
+
+func GenTransitionTable(dfa *DFA) (*spec.TransitionTable, error) {
+	stateHash2ID := map[string]spec.StateID{}
+	for i, s := range dfa.States {
+		// Since 0 represents an invalid value in a transition table,
+		// assign a number greater than or equal to 1 to states.
+		stateHash2ID[s] = spec.StateID(i + spec.StateIDMin.Int())
+	}
+
+	acc := make([]spec.LexModeKindID, len(dfa.States)+1)
+	for _, s := range dfa.States {
+		id, ok := dfa.AcceptingStatesTable[s]
+		if !ok {
+			continue
+		}
+		acc[stateHash2ID[s]] = id
+	}
+
+	rowCount := len(dfa.States) + 1
+	colCount := 256
+	tran := make([]spec.StateID, rowCount*colCount)
+	for s, tab := range dfa.TransitionTable {
+		for v, to := range tab {
+			tran[stateHash2ID[s].Int()*256+v] = stateHash2ID[to]
+		}
+	}
+
+	return &spec.TransitionTable{
+		InitialStateID:         stateHash2ID[dfa.InitialState],
+		AcceptingStates:        acc,
+		UncompressedTransition: tran,
+		RowCount:               rowCount,
+		ColCount:               colCount,
+	}, nil
+}