Esempio n. 1
0
File: exec.go Progetto: vron/sem
// add adds an entry to q for pc, unless the q already has such an entry.
// It also recursively adds an entry for all instructions reachable from pc by following
// empty-width conditions satisfied by cond.  pos gives the current position
// in the input.
func (m *machine) add(q *queue, pc uint32, pos int, cap []int, cond syntax.EmptyOp, t *thread) *thread {
	if pc == 0 {
		return t
	}
	if j := q.sparse[pc]; j < uint32(len(q.dense)) && q.dense[j].pc == pc {
		return t
	}

	j := len(q.dense)
	q.dense = q.dense[:j+1]
	d := &q.dense[j]
	d.t = nil
	d.pc = pc
	q.sparse[pc] = uint32(j)

	i := &m.p.Inst[pc]
	switch i.Op {
	default:
		panic("unhandled")
	case syntax.InstFail:
		// nothing
	case syntax.InstAlt, syntax.InstAltMatch:
		t = m.add(q, i.Out, pos, cap, cond, t)
		t = m.add(q, i.Arg, pos, cap, cond, t)
	case syntax.InstEmptyWidth:
		if syntax.EmptyOp(i.Arg)&^cond == 0 {
			t = m.add(q, i.Out, pos, cap, cond, t)
		}
	case syntax.InstNop:
		t = m.add(q, i.Out, pos, cap, cond, t)
	case syntax.InstCapture:
		if int(i.Arg) < len(cap) {
			opos := cap[i.Arg]
			cap[i.Arg] = pos
			m.add(q, i.Out, pos, cap, cond, nil)
			cap[i.Arg] = opos
		} else {
			t = m.add(q, i.Out, pos, cap, cond, t)
		}
	case syntax.InstMatch, syntax.InstRune, syntax.InstRune1, syntax.InstRuneAny, syntax.InstRuneAnyNotNL:
		if t == nil {
			t = m.alloc(i)
		} else {
			t.inst = i
		}
		if len(cap) > 0 && &t.cap[0] != &cap[0] {
			copy(t.cap, cap)
		}
		d.t = t
		t = nil
	}
	return t
}
Esempio n. 2
0
File: exec.go Progetto: vron/sem
// match runs the machine over the input starting at pos.
// It reports whether a match was found.
// If so, m.matchcap holds the submatch information.
func (m *machine) match(i Input, pos int) bool {
	startCond := m.re.cond
	if startCond == ^syntax.EmptyOp(0) { // impossible
		return false
	}
	m.matched = false
	for i := range m.matchcap {
		m.matchcap[i] = -1
	}
	runq, nextq := &m.q0, &m.q1
	r, r1 := endOfText, endOfText
	width, width1 := 0, 0
	r, width = i.Step(pos)
	if r != endOfText {
		r1, width1 = i.Step(pos + width)
	}
	var flag syntax.EmptyOp
	if pos == 0 {
		flag = syntax.EmptyOpContext(-1, r)
	} else {
		flag = i.Context(pos)
	}
	for {
		if len(runq.dense) == 0 {
			if startCond&syntax.EmptyBeginText != 0 && pos != 0 {
				// Anchored match, past beginning of text.
				break
			}
			if m.matched {
				// Have match; finished exploring alternatives.
				break
			}
			if len(m.re.prefix) > 0 && r1 != m.re.prefixRune && i.CanCheckPrefix() {
				// Match requires literal prefix; fast search for it.
				advance := i.Index(m.re, pos)
				if advance < 0 {
					break
				}
				pos += advance
				r, width = i.Step(pos)
				r1, width1 = i.Step(pos + width)
			}
		}
		if !m.matched {
			if len(m.matchcap) > 0 {
				m.matchcap[0] = pos
			}
			m.add(runq, uint32(m.p.Start), pos, m.matchcap, flag, nil)
		}
		flag = syntax.EmptyOpContext(r, r1)
		m.step(runq, nextq, pos, pos+width, r, flag)
		if width == 0 {
			break
		}
		if len(m.matchcap) == 0 && m.matched {
			// Found a match and not paying attention
			// to where it is, so any match will do.
			break
		}
		pos += width
		r, width = r1, width1
		if r != endOfText {
			r1, width1 = i.Step(pos + width)
		}
		runq, nextq = nextq, runq
	}
	m.clear(nextq)
	return m.matched
}