Golang syntax.EmptyOpContext函数代码示例

func (i *inputBytes) context(pos int) syntax.EmptyOp {
	r1, r2 := endOfText, endOfText
	if pos > 0 && pos <= len(i.str) {
		r1, _ = utf8.DecodeLastRune(i.str[:pos])
	}
	if pos < len(i.str) {
		r2, _ = utf8.DecodeRune(i.str[pos:])
	}
	return syntax.EmptyOpContext(r1, r2)
}

func (i *inputString) context(pos int) syntax.EmptyOp {
	r1, r2 := -1, -1
	if pos > 0 && pos <= len(i.str) {
		r1, _ = utf8.DecodeLastRuneInString(i.str[:pos])
	}
	if pos < len(i.str) {
		r2, _ = utf8.DecodeRuneInString(i.str[pos:])
	}
	return syntax.EmptyOpContext(r1, r2)
}

// onepass 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) onepass(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
	}
	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)
	}
	pc := m.op.Start
	inst := m.op.Inst[pc]
	// If there is a simple literal prefix, skip over it.
	if pos == 0 && syntax.EmptyOp(inst.Arg)&^flag == 0 &&
		len(m.re.prefix) > 0 && i.canCheckPrefix() {
		// Match requires literal prefix; fast search for it.
		if i.hasPrefix(m.re) {
			pos += len(m.re.prefix)
			r, width = i.step(pos)
			r1, width1 = i.step(pos + width)
			flag = i.context(pos)
			pc = int(m.re.prefixEnd)
		} else {
			return m.matched
		}
	}
	for {
		inst = m.op.Inst[pc]
		pc = int(inst.Out)
		switch inst.Op {
		default:
			panic("bad inst")
		case syntax.InstMatch:
			m.matched = true
			if len(m.matchcap) > 0 {
				m.matchcap[0] = 0
				m.matchcap[1] = pos
			}
			return m.matched
		case syntax.InstRune:
			if !inst.MatchRune(r) {
				return m.matched
			}
		case syntax.InstRune1:
			if r != inst.Rune[0] {
				return m.matched
			}
		case syntax.InstRuneAny:
			// Nothing
		case syntax.InstRuneAnyNotNL:
			if r == '\n' {
				return m.matched
			}
		// peek at the input rune to see which branch of the Alt to take
		case syntax.InstAlt, syntax.InstAltMatch:
			pc = int(onePassNext(&inst, r))
			continue
		case syntax.InstFail:
			return m.matched
		case syntax.InstNop:
			continue
		case syntax.InstEmptyWidth:
			if syntax.EmptyOp(inst.Arg)&^flag != 0 {
				return m.matched
			}
			continue
		case syntax.InstCapture:
			if int(inst.Arg) < len(m.matchcap) {
				m.matchcap[inst.Arg] = pos
			}
			continue
		}
		if width == 0 {
			break
		}
		flag = syntax.EmptyOpContext(r, r1)
		pos += width
		r, width = r1, width1
		if r != endOfText {
			r1, width1 = i.step(pos + width)
		}
	}
	return m.matched
}

// 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
}