expr.go - platform/build/kati - Git at Google

 package main

 import (
 	"bytes"
 	"errors"
 	"fmt"
 	"io"
 	"strconv"
 	"strings"
 	"sync"
 	"time"
 )

 var (
 	errEndOfInput = errors.New("parse: unexpected end of input")

 	bufFree = sync.Pool{
 		New: func() interface{} { return new(buffer) },
 	}
 )

 type buffer struct {
 	bytes.Buffer
 	args [][]byte
 }

 func newBuf() *buffer {
 	buf := bufFree.Get().(*buffer)
 	return buf
 }

 func freeBuf(buf *buffer) {
 	if cap(buf.Bytes()) > 1024 {
 		return
 	}
 	buf.Reset()
 	buf.args = buf.args[:0]
 	bufFree.Put(buf)
 }

 type Value interface {
 	String() string
 	Eval(w io.Writer, ev *Evaluator)
 	Serialize() SerializableVar
 	Dump(w io.Writer)
 }

 type Valuer interface {
 	Value() []byte
 }

 // literal is literal value.
 // TODO(ukai): always use []byte?
 type literal string

 func (s literal) String() string { return string(s) }
 func (s literal) Eval(w io.Writer, ev *Evaluator) {
 	io.WriteString(w, string(s))
 }
 func (s literal) Serialize() SerializableVar {
 	return SerializableVar{Type: "literal", V: string(s)}
 }
 func (s literal) Dump(w io.Writer) {
 	dumpByte(w, VALUE_TYPE_LITERAL)
 	dumpBytes(w, []byte(s))
 }

 // tmpval is temporary value.
 // TODO(ukai): Values() returns []Value? (word list?)
 type tmpval []byte

 func (t tmpval) String() string { return string(t) }
 func (t tmpval) Eval(w io.Writer, ev *Evaluator) {
 	w.Write(t)
 }
 func (t tmpval) Value() []byte { return []byte(t) }
 func (t tmpval) Serialize() SerializableVar {
 	return SerializableVar{Type: "tmpval", V: string(t)}
 }
 func (t tmpval) Dump(w io.Writer) {
 	dumpByte(w, VALUE_TYPE_TMPVAL)
 	dumpBytes(w, t)
 }

 // Expr is a list of values.
 type Expr []Value

 func (e Expr) String() string {
 	var s []string
 	for _, v := range e {
 		s = append(s, v.String())
 	}
 	return strings.Join(s, "")
 }

 func (e Expr) Eval(w io.Writer, ev *Evaluator) {
 	for _, v := range e {
 		v.Eval(w, ev)
 	}
 }

 func (e Expr) Serialize() SerializableVar {
 	r := SerializableVar{Type: "expr"}
 	for _, v := range e {
 		r.Children = append(r.Children, v.Serialize())
 	}
 	return r
 }
 func (e Expr) Dump(w io.Writer) {
 	dumpByte(w, VALUE_TYPE_EXPR)
 	dumpInt(w, len(e))
 	for _, v := range e {
 		v.Dump(w)
 	}
 }

 func compactExpr(e Expr) Value {
 	if len(e) == 1 {
 		return e[0]
 	}
 	// TODO(ukai): concat literal
 	return e
 }

 // varref is variable reference. e.g. ${foo}.
 type varref struct {
 	varname Value
 }

 func (v varref) String() string {
 	varname := v.varname.String()
 	if len(varname) == 1 {
 		return fmt.Sprintf("$%s", varname)
 	}
 	return fmt.Sprintf("${%s}", varname)
 }

 func (v varref) Eval(w io.Writer, ev *Evaluator) {
 	t := time.Now()
 	buf := newBuf()
 	v.varname.Eval(buf, ev)
 	vv := ev.LookupVar(buf.String())
 	freeBuf(buf)
 	vv.Eval(w, ev)
 	addStats("var", v, t)
 }

 func (v varref) Serialize() SerializableVar {
 	return SerializableVar{
 		Type:     "varref",
 		Children: []SerializableVar{v.varname.Serialize()},
 	}
 }
 func (v varref) Dump(w io.Writer) {
 	dumpByte(w, VALUE_TYPE_VARREF)
 	v.varname.Dump(w)
 }

 // paramref is parameter reference e.g. $1.
 type paramref int

 func (p paramref) String() string {
 	return fmt.Sprintf("$%d", int(p))
 }

 func (p paramref) Eval(w io.Writer, ev *Evaluator) {
 	t := time.Now()
 	n := int(p)
 	if n < len(ev.paramVars) {
 		ev.paramVars[n].Eval(w, ev)
 	} else {
 		// out of range?
 		// panic(fmt.Sprintf("out of range %d: %d", n, len(ev.paramVars)))
 	}
 	addStats("param", p, t)
 }

 func (p paramref) Serialize() SerializableVar {
 	return SerializableVar{Type: "paramref", V: strconv.Itoa(int(p))}
 }

 func (p paramref) Dump(w io.Writer) {
 	dumpByte(w, VALUE_TYPE_PARAMREF)
 	dumpInt(w, int(p))
 }

 // varsubst is variable substitutaion. e.g. ${var:pat=subst}.
 type varsubst struct {
 	varname Value
 	pat     Value
 	subst   Value
 }

 func (v varsubst) String() string {
 	return fmt.Sprintf("${%s:%s=%s}", v.varname, v.pat, v.subst)
 }

 func (v varsubst) Eval(w io.Writer, ev *Evaluator) {
 	t := time.Now()
 	buf := newBuf()
 	params := ev.args(buf, v.varname, v.pat, v.subst)
 	vname := string(params[0])
 	pat := string(params[1])
 	subst := string(params[2])
 	buf.Reset()
 	vv := ev.LookupVar(vname)
 	vv.Eval(buf, ev)
 	vals := splitSpaces(buf.String())
 	freeBuf(buf)
 	space := false
 	for _, val := range vals {
 		if space {
 			io.WriteString(w, " ")
 		}
 		io.WriteString(w, substRef(pat, subst, val))
 		space = true
 	}
 	addStats("varsubst", v, t)
 }

 func (v varsubst) Serialize() SerializableVar {
 	return SerializableVar{
 		Type: "varsubst",
 		Children: []SerializableVar{
 			v.varname.Serialize(),
 			v.pat.Serialize(),
 			v.subst.Serialize(),
 		},
 	}
 }

 func (v varsubst) Dump(w io.Writer) {
 	dumpByte(w, VALUE_TYPE_VARSUBST)
 	v.varname.Dump(w)
 	v.pat.Dump(w)
 	v.subst.Dump(w)
 }

 // parseExpr parses expression in `in` until it finds any byte in term.
 // if term is nil, it will parse to end of input.
 // if term is not nil, and it reaches to end of input, return errEndOfInput.
 // it returns parsed value, and parsed length `n`, so in[n-1] is any byte of
 // term, and in[n:] is next input.
 func parseExpr(in, term []byte) (Value, int, error) {
 	var expr Expr
 	buf := make([]byte, 0, len(in))
 	b := 0
 	i := 0
 	var saveParen byte
 	parenDepth := 0
 Loop:
 	for i < len(in) {
 		ch := in[i]
 		if term != nil && bytes.IndexByte(term, ch) >= 0 {
 			break Loop
 		}
 		switch ch {
 		case '$':
 			if i+1 >= len(in) {
 				break Loop
 			}
 			if in[i+1] == '$' {
 				buf = append(buf, in[b:i+1]...)
 				i += 2
 				b = i
 				continue
 			}
 			if bytes.IndexByte(term, in[i+1]) >= 0 {
 				buf = append(buf, in[b:i]...)
 				if len(buf) > 0 {
 					expr = append(expr, literal(string(buf)))
 					buf = buf[:0]
 				}
 				expr = append(expr, varref{varname: literal("")})
 				i++
 				b = i
 				break Loop
 			}
 			buf = append(buf, in[b:i]...)
 			if len(buf) > 0 {
 				expr = append(expr, literal(string(buf)))
 				buf = buf[:0]
 			}
 			v, n, err := parseDollar(in[i:])
 			if err != nil {
 				return nil, 0, err
 			}
 			i += n
 			b = i
 			expr = append(expr, v)
 			continue
 		case '(', '{':
 			cp := closeParen(ch)
 			if i := bytes.IndexByte(term, cp); i >= 0 {
 				parenDepth++
 				saveParen = cp
 				term[i] = 0
 			} else if cp == saveParen {
 				parenDepth++
 			}
 		case saveParen:
 			parenDepth--
 			if parenDepth == 0 {
 				i := bytes.IndexByte(term, 0)
 				term[i] = saveParen
 				saveParen = 0
 			}
 		}
 		i++
 	}
 	buf = append(buf, in[b:i]...)
 	if len(buf) > 0 {
 		expr = append(expr, literal(string(buf)))
 	}
 	if i == len(in) && term != nil {
 		return expr, i, errEndOfInput
 	}
 	return compactExpr(expr), i, nil
 }

 func closeParen(ch byte) byte {
 	switch ch {
 	case '(':
 		return ')'
 	case '{':
 		return '}'
 	}
 	return 0
 }

 // parseDollar parses
 //   $(func expr[, expr...])  # func = literal SP
 //   $(expr:expr=expr)
 //   $(expr)
 //   $x
 // it returns parsed value and parsed length.
 func parseDollar(in []byte) (Value, int, error) {
 	if len(in) <= 1 {
 		return nil, 0, errors.New("empty expr")
 	}
 	if in[0] != '$' {
 		return nil, 0, errors.New("should starts with $")
 	}
 	if in[1] == '$' {
 		return nil, 0, errors.New("should handle $$ as literal $")
 	}
 	paren := closeParen(in[1])
 	if paren == 0 {
 		// $x case.
 		if in[1] >= '0' && in[1] <= '9' {
 			return paramref(in[1] - '0'), 2, nil
 		}
 		return varref{varname: literal(string(in[1]))}, 2, nil
 	}
 	term := []byte{paren, ':', ' '}
 	var varname Expr
 	i := 2
 Again:
 	for {
 		e, n, err := parseExpr(in[i:], term)
 		if err != nil {
 			return nil, 0, err
 		}
 		varname = append(varname, e)
 		i += n
 		switch in[i] {
 		case paren:
 			// ${expr}
 			vname := compactExpr(varname)
 			if vname, ok := vname.(literal); ok {
 				n, err := strconv.ParseInt(string(vname), 10, 64)
 				if err == nil {
 					// ${n}
 					return paramref(n), i + 1, nil
 				}
 			}
 			return varref{varname: vname}, i + 1, nil
 		case ' ':
 			// ${e ...}
 			if token, ok := e.(literal); ok {
 				funcName := string(token)
 				if f, ok := funcMap[funcName]; ok {
 					return parseFunc(f(), in, i+1, term[:1], funcName)
 				}
 			}
 			term = term[:2] // drop ' '
 			continue Again
 		case ':':
 			// ${varname:...}
 			term = term[:2]
 			term[1] = '=' // term={paren, '='}.
 			e, n, err := parseExpr(in[i+1:], term)
 			if err != nil {
 				return nil, 0, err
 			}
 			i += 1 + n
 			if in[i] == paren {
 				varname = append(varname, literal(string(":")), e)
 				return varref{varname: varname}, i + 1, nil
 			}
 			// ${varname:xx=...}
 			pat := e
 			subst, n, err := parseExpr(in[i+1:], term[:1])
 			if err != nil {
 				return nil, 0, err
 			}
 			i += 1 + n
 			// ${first:pat=e}
 			return varsubst{
 				varname: compactExpr(varname),
 				pat:     pat,
 				subst:   subst,
 			}, i + 1, nil
 		default:
 			panic(fmt.Sprintf("unexpected char"))
 		}
 	}
 }

 // skipSpaces skips spaces at front of `in` before any bytes in term.
 // in[n] will be the first non white space in in.
 func skipSpaces(in, term []byte) int {
 	for i := 0; i < len(in); i++ {
 		if bytes.IndexByte(term, in[i]) >= 0 {
 			return i
 		}
 		switch in[i] {
 		case ' ', '\t':
 		default:
 			return i
 		}
 	}
 	return len(in)
 }

 // trimLiteralSpace trims literal space around v.
 func trimLiteralSpace(v Value) Value {
 	switch v := v.(type) {
 	case literal:
 		return literal(strings.TrimSpace(string(v)))
 	case tmpval:
 		b := bytes.TrimSpace([]byte(v))
 		if len(b) == 0 {
 			return literal("")
 		}
 		return tmpval(b)
 	case Expr:
 		if len(v) == 0 {
 			return v
 		}
 		switch s := v[0].(type) {
 		case literal, tmpval:
 			t := trimLiteralSpace(s)
 			if t == literal("") {
 				v = v[1:]
 			} else {
 				v[0] = t
 			}
 		}
 		switch s := v[len(v)-1].(type) {
 		case literal, tmpval:
 			t := trimLiteralSpace(s)
 			if t == literal("") {
 				v = v[:len(v)-1]
 			} else {
 				v[len(v)-1] = t
 			}
 		}
 		return compactExpr(v)
 	}
 	return v
 }

 // concatLine concatinates line with "\\\n" in function expression.
 func concatLine(v Value) Value {
 	switch v := v.(type) {
 	case literal:
 		for {
 			s := string(v)
 			i := strings.Index(s, "\\\n")
 			if i < 0 {
 				return v
 			}
 			v = literal(s[:i] + strings.TrimLeft(s[i+2:], " \t"))
 		}
 	case tmpval:
 		for {
 			b := []byte(v)
 			i := bytes.Index(b, []byte{'\\', '\n'})
 			if i < 0 {
 				return v
 			}
 			var buf bytes.Buffer
 			buf.Write(b[:i])
 			buf.Write(bytes.TrimLeft(b[i+2:], " \t"))
 			v = tmpval(buf.Bytes())
 		}
 	case Expr:
 		for i := range v {
 			switch vv := v[i].(type) {
 			case literal, tmpval:
 				v[i] = concatLine(vv)
 			}
 		}
 		return v
 	}
 	return v
 }

 // parseFunc parses function arguments from in[s:] for f.
 // in[0] is '$' and in[s] is space just after func name.
 // in[:n] will be "${func args...}"
 func parseFunc(f Func, in []byte, s int, term []byte, funcName string) (Value, int, error) {
 	f.AddArg(literal(string(in[1 : s-1])))
 	arity := f.Arity()
 	term = append(term, ',')
 	i := skipSpaces(in[s:], term)
 	i = s + i
 	if i == len(in) {
 		return f, i, nil
 	}
 	narg := 1
 	for {
 		if arity != 0 && narg >= arity {
 			// final arguments.
 			term = term[:1] // drop ','
 		}
 		v, n, err := parseExpr(in[i:], term)
 		if err != nil {
 			return nil, 0, err
 		}
 		v = concatLine(v)
 		// TODO(ukai): do this in funcIf, funcAnd, or funcOr's compactor?
 		if (narg == 1 && funcName == "if") || funcName == "and" || funcName == "or" {
 			v = trimLiteralSpace(v)
 		}
 		f.AddArg(v)
 		i += n
 		narg++
 		if in[i] == term[0] {
 			i++
 			break
 		}
 		i++ // should be ','
 		if i == len(in) {
 			break
 		}
 	}
 	var fv Value
 	fv = f
 	if compactor, ok := f.(Compactor); ok {
 		fv = compactor.Compact()
 	}
 	if katiStatsFlag {
 		fv = funcstats{fv}
 	}
 	return fv, i, nil
 }

 type Compactor interface {
 	Compact() Value
 }

 type funcstats struct {
 	Value
 }

 func (f funcstats) Eval(w io.Writer, ev *Evaluator) {
 	t := time.Now()
 	f.Value.Eval(w, ev)
 	// TODO(ukai): per functype?
 	addStats("func", f, t)
 }
	package main

	import (
	"bytes"
	"errors"
	"fmt"
	"io"
	"strconv"
	"strings"
	"sync"
	"time"
	)

	var (
	errEndOfInput = errors.New("parse: unexpected end of input")

	bufFree = sync.Pool{
	New: func() interface{} { return new(buffer) },
	}
	)

	type buffer struct {
	bytes.Buffer
	args [][]byte
	}

	func newBuf() *buffer {
	buf := bufFree.Get().(*buffer)
	return buf
	}

	func freeBuf(buf *buffer) {
	if cap(buf.Bytes()) > 1024 {
	return
	}
	buf.Reset()
	buf.args = buf.args[:0]
	bufFree.Put(buf)
	}

	type Value interface {
	String() string
	Eval(w io.Writer, ev *Evaluator)
	Serialize() SerializableVar
	Dump(w io.Writer)
	}

	type Valuer interface {
	Value() []byte
	}

	// literal is literal value.
	// TODO(ukai): always use []byte?
	type literal string

	func (s literal) String() string { return string(s) }
	func (s literal) Eval(w io.Writer, ev *Evaluator) {
	io.WriteString(w, string(s))
	}
	func (s literal) Serialize() SerializableVar {
	return SerializableVar{Type: "literal", V: string(s)}
	}
	func (s literal) Dump(w io.Writer) {
	dumpByte(w, VALUE_TYPE_LITERAL)
	dumpBytes(w, []byte(s))
	}

	// tmpval is temporary value.
	// TODO(ukai): Values() returns []Value? (word list?)
	type tmpval []byte

	func (t tmpval) String() string { return string(t) }
	func (t tmpval) Eval(w io.Writer, ev *Evaluator) {
	w.Write(t)
	}
	func (t tmpval) Value() []byte { return []byte(t) }
	func (t tmpval) Serialize() SerializableVar {
	return SerializableVar{Type: "tmpval", V: string(t)}
	}
	func (t tmpval) Dump(w io.Writer) {
	dumpByte(w, VALUE_TYPE_TMPVAL)
	dumpBytes(w, t)
	}

	// Expr is a list of values.
	type Expr []Value

	func (e Expr) String() string {
	var s []string
	for _, v := range e {
	s = append(s, v.String())
	}
	return strings.Join(s, "")
	}

	func (e Expr) Eval(w io.Writer, ev *Evaluator) {
	for _, v := range e {
	v.Eval(w, ev)
	}
	}

	func (e Expr) Serialize() SerializableVar {
	r := SerializableVar{Type: "expr"}
	for _, v := range e {
	r.Children = append(r.Children, v.Serialize())
	}
	return r
	}
	func (e Expr) Dump(w io.Writer) {
	dumpByte(w, VALUE_TYPE_EXPR)
	dumpInt(w, len(e))
	for _, v := range e {
	v.Dump(w)
	}
	}

	func compactExpr(e Expr) Value {
	if len(e) == 1 {
	return e[0]
	}
	// TODO(ukai): concat literal
	return e
	}

	// varref is variable reference. e.g. ${foo}.
	type varref struct {
	varname Value
	}

	func (v varref) String() string {
	varname := v.varname.String()
	if len(varname) == 1 {
	return fmt.Sprintf("$%s", varname)
	}
	return fmt.Sprintf("${%s}", varname)
	}

	func (v varref) Eval(w io.Writer, ev *Evaluator) {
	t := time.Now()
	buf := newBuf()
	v.varname.Eval(buf, ev)
	vv := ev.LookupVar(buf.String())
	freeBuf(buf)
	vv.Eval(w, ev)
	addStats("var", v, t)
	}

	func (v varref) Serialize() SerializableVar {
	return SerializableVar{
	Type: "varref",
	Children: []SerializableVar{v.varname.Serialize()},
	}
	}
	func (v varref) Dump(w io.Writer) {
	dumpByte(w, VALUE_TYPE_VARREF)
	v.varname.Dump(w)
	}

	// paramref is parameter reference e.g. $1.
	type paramref int

	func (p paramref) String() string {
	return fmt.Sprintf("$%d", int(p))
	}

	func (p paramref) Eval(w io.Writer, ev *Evaluator) {
	t := time.Now()
	n := int(p)
	if n < len(ev.paramVars) {
	ev.paramVars[n].Eval(w, ev)
	} else {
	// out of range?
	// panic(fmt.Sprintf("out of range %d: %d", n, len(ev.paramVars)))
	}
	addStats("param", p, t)
	}

	func (p paramref) Serialize() SerializableVar {
	return SerializableVar{Type: "paramref", V: strconv.Itoa(int(p))}
	}

	func (p paramref) Dump(w io.Writer) {
	dumpByte(w, VALUE_TYPE_PARAMREF)
	dumpInt(w, int(p))
	}

	// varsubst is variable substitutaion. e.g. ${var:pat=subst}.
	type varsubst struct {
	varname Value
	pat Value
	subst Value
	}

	func (v varsubst) String() string {
	return fmt.Sprintf("${%s:%s=%s}", v.varname, v.pat, v.subst)
	}

	func (v varsubst) Eval(w io.Writer, ev *Evaluator) {
	t := time.Now()
	buf := newBuf()
	params := ev.args(buf, v.varname, v.pat, v.subst)
	vname := string(params[0])
	pat := string(params[1])
	subst := string(params[2])
	buf.Reset()
	vv := ev.LookupVar(vname)
	vv.Eval(buf, ev)
	vals := splitSpaces(buf.String())
	freeBuf(buf)
	space := false
	for _, val := range vals {
	if space {
	io.WriteString(w, " ")
	}
	io.WriteString(w, substRef(pat, subst, val))
	space = true
	}
	addStats("varsubst", v, t)
	}

	func (v varsubst) Serialize() SerializableVar {
	return SerializableVar{
	Type: "varsubst",
	Children: []SerializableVar{
	v.varname.Serialize(),
	v.pat.Serialize(),
	v.subst.Serialize(),
	},
	}
	}

	func (v varsubst) Dump(w io.Writer) {
	dumpByte(w, VALUE_TYPE_VARSUBST)
	v.varname.Dump(w)
	v.pat.Dump(w)
	v.subst.Dump(w)
	}

	// parseExpr parses expression in `in` until it finds any byte in term.
	// if term is nil, it will parse to end of input.
	// if term is not nil, and it reaches to end of input, return errEndOfInput.
	// it returns parsed value, and parsed length `n`, so in[n-1] is any byte of
	// term, and in[n:] is next input.
	func parseExpr(in, term []byte) (Value, int, error) {
	var expr Expr
	buf := make([]byte, 0, len(in))
	b := 0
	i := 0
	var saveParen byte
	parenDepth := 0
	Loop:
	for i < len(in) {
	ch := in[i]
	if term != nil && bytes.IndexByte(term, ch) >= 0 {
	break Loop
	}
	switch ch {
	case '$':
	if i+1 >= len(in) {
	break Loop
	}
	if in[i+1] == '$' {
	buf = append(buf, in[b:i+1]...)
	i += 2
	b = i
	continue
	}
	if bytes.IndexByte(term, in[i+1]) >= 0 {
	buf = append(buf, in[b:i]...)
	if len(buf) > 0 {
	expr = append(expr, literal(string(buf)))
	buf = buf[:0]
	}
	expr = append(expr, varref{varname: literal("")})
	i++
	b = i
	break Loop
	}
	buf = append(buf, in[b:i]...)
	if len(buf) > 0 {
	expr = append(expr, literal(string(buf)))
	buf = buf[:0]
	}
	v, n, err := parseDollar(in[i:])
	if err != nil {
	return nil, 0, err
	}
	i += n
	b = i
	expr = append(expr, v)
	continue
	case '(', '{':
	cp := closeParen(ch)
	if i := bytes.IndexByte(term, cp); i >= 0 {
	parenDepth++
	saveParen = cp
	term[i] = 0
	} else if cp == saveParen {
	parenDepth++
	}
	case saveParen:
	parenDepth--
	if parenDepth == 0 {
	i := bytes.IndexByte(term, 0)
	term[i] = saveParen
	saveParen = 0
	}
	}
	i++
	}
	buf = append(buf, in[b:i]...)
	if len(buf) > 0 {
	expr = append(expr, literal(string(buf)))
	}
	if i == len(in) && term != nil {
	return expr, i, errEndOfInput
	}
	return compactExpr(expr), i, nil
	}

	func closeParen(ch byte) byte {
	switch ch {
	case '(':
	return ')'
	case '{':
	return '}'
	}
	return 0
	}

	// parseDollar parses
	// $(func expr[, expr...]) # func = literal SP
	// $(expr:expr=expr)
	// $(expr)
	// $x
	// it returns parsed value and parsed length.
	func parseDollar(in []byte) (Value, int, error) {
	if len(in) <= 1 {
	return nil, 0, errors.New("empty expr")
	}
	if in[0] != '$' {
	return nil, 0, errors.New("should starts with $")
	}
	if in[1] == '$' {
	return nil, 0, errors.New("should handle $$ as literal $")
	}
	paren := closeParen(in[1])
	if paren == 0 {
	// $x case.
	if in[1] >= '0' && in[1] <= '9' {
	return paramref(in[1] - '0'), 2, nil
	}
	return varref{varname: literal(string(in[1]))}, 2, nil
	}
	term := []byte{paren, ':', ' '}
	var varname Expr
	i := 2
	Again:
	for {
	e, n, err := parseExpr(in[i:], term)
	if err != nil {
	return nil, 0, err
	}
	varname = append(varname, e)
	i += n
	switch in[i] {
	case paren:
	// ${expr}
	vname := compactExpr(varname)
	if vname, ok := vname.(literal); ok {
	n, err := strconv.ParseInt(string(vname), 10, 64)
	if err == nil {
	// ${n}
	return paramref(n), i + 1, nil
	}
	}
	return varref{varname: vname}, i + 1, nil
	case ' ':
	// ${e ...}
	if token, ok := e.(literal); ok {
	funcName := string(token)
	if f, ok := funcMap[funcName]; ok {
	return parseFunc(f(), in, i+1, term[:1], funcName)
	}
	}
	term = term[:2] // drop ' '
	continue Again
	case ':':
	// ${varname:...}
	term = term[:2]
	term[1] = '=' // term={paren, '='}.
	e, n, err := parseExpr(in[i+1:], term)
	if err != nil {
	return nil, 0, err
	}
	i += 1 + n
	if in[i] == paren {
	varname = append(varname, literal(string(":")), e)
	return varref{varname: varname}, i + 1, nil
	}
	// ${varname:xx=...}
	pat := e
	subst, n, err := parseExpr(in[i+1:], term[:1])
	if err != nil {
	return nil, 0, err
	}
	i += 1 + n
	// ${first:pat=e}
	return varsubst{
	varname: compactExpr(varname),
	pat: pat,
	subst: subst,
	}, i + 1, nil
	default:
	panic(fmt.Sprintf("unexpected char"))
	}
	}
	}

	// skipSpaces skips spaces at front of `in` before any bytes in term.
	// in[n] will be the first non white space in in.
	func skipSpaces(in, term []byte) int {
	for i := 0; i < len(in); i++ {
	if bytes.IndexByte(term, in[i]) >= 0 {
	return i
	}
	switch in[i] {
	case ' ', '\t':
	default:
	return i
	}
	}
	return len(in)
	}

	// trimLiteralSpace trims literal space around v.
	func trimLiteralSpace(v Value) Value {
	switch v := v.(type) {
	case literal:
	return literal(strings.TrimSpace(string(v)))
	case tmpval:
	b := bytes.TrimSpace([]byte(v))
	if len(b) == 0 {
	return literal("")
	}
	return tmpval(b)
	case Expr:
	if len(v) == 0 {
	return v
	}
	switch s := v[0].(type) {
	case literal, tmpval:
	t := trimLiteralSpace(s)
	if t == literal("") {
	v = v[1:]
	} else {
	v[0] = t
	}
	}
	switch s := v[len(v)-1].(type) {
	case literal, tmpval:
	t := trimLiteralSpace(s)
	if t == literal("") {
	v = v[:len(v)-1]
	} else {
	v[len(v)-1] = t
	}
	}
	return compactExpr(v)
	}
	return v
	}

	// concatLine concatinates line with "\\\n" in function expression.
	func concatLine(v Value) Value {
	switch v := v.(type) {
	case literal:
	for {
	s := string(v)
	i := strings.Index(s, "\\\n")
	if i < 0 {
	return v
	}
	v = literal(s[:i] + strings.TrimLeft(s[i+2:], " \t"))
	}
	case tmpval:
	for {
	b := []byte(v)
	i := bytes.Index(b, []byte{'\\', '\n'})
	if i < 0 {
	return v
	}
	var buf bytes.Buffer
	buf.Write(b[:i])
	buf.Write(bytes.TrimLeft(b[i+2:], " \t"))
	v = tmpval(buf.Bytes())
	}
	case Expr:
	for i := range v {
	switch vv := v[i].(type) {
	case literal, tmpval:
	v[i] = concatLine(vv)
	}
	}
	return v
	}
	return v
	}

	// parseFunc parses function arguments from in[s:] for f.
	// in[0] is '$' and in[s] is space just after func name.
	// in[:n] will be "${func args...}"
	func parseFunc(f Func, in []byte, s int, term []byte, funcName string) (Value, int, error) {
	f.AddArg(literal(string(in[1 : s-1])))
	arity := f.Arity()
	term = append(term, ',')
	i := skipSpaces(in[s:], term)
	i = s + i
	if i == len(in) {
	return f, i, nil
	}
	narg := 1
	for {
	if arity != 0 && narg >= arity {
	// final arguments.
	term = term[:1] // drop ','
	}
	v, n, err := parseExpr(in[i:], term)
	if err != nil {
	return nil, 0, err
	}
	v = concatLine(v)
	// TODO(ukai): do this in funcIf, funcAnd, or funcOr's compactor?
	if (narg == 1 && funcName == "if") \|\| funcName == "and" \|\| funcName == "or" {
	v = trimLiteralSpace(v)
	}
	f.AddArg(v)
	i += n
	narg++
	if in[i] == term[0] {
	i++
	break
	}
	i++ // should be ','
	if i == len(in) {
	break
	}
	}
	var fv Value
	fv = f
	if compactor, ok := f.(Compactor); ok {
	fv = compactor.Compact()
	}
	if katiStatsFlag {
	fv = funcstats{fv}
	}
	return fv, i, nil
	}

	type Compactor interface {
	Compact() Value
	}

	type funcstats struct {
	Value
	}

	func (f funcstats) Eval(w io.Writer, ev *Evaluator) {
	t := time.Now()
	f.Value.Eval(w, ev)
	// TODO(ukai): per functype?
	addStats("func", f, t)
	}