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compose.go
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compose.go
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package bpl
import (
"bufio"
"errors"
"io"
"io/ioutil"
"reflect"
"github.com/qiniu/x/bufiox"
)
var (
// ErrVarNotAssigned is returned when TypeVar.Elem is not assigned.
ErrVarNotAssigned = errors.New("variable is not assigned")
// ErrVarAssigned is returned when TypeVar.Elem is already assigned.
ErrVarAssigned = errors.New("variable is already assigned")
// ErrNotEOF is returned when current position is not at EOF.
ErrNotEOF = errors.New("current position is not at EOF")
)
// -----------------------------------------------------------------------------
type nilType int
func (p nilType) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
return nil, nil
}
func (p nilType) RetType() reflect.Type {
return TyInterface
}
func (p nilType) SizeOf() int {
return 0
}
// Nil is a matching unit that matches zero bytes.
//
var Nil Ruler = nilType(0)
// -----------------------------------------------------------------------------
type eof int
func (p eof) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
_, err = in.Peek(1)
if err == io.EOF {
return nil, nil
}
return nil, ErrNotEOF
}
func (p eof) RetType() reflect.Type {
return TyInterface
}
func (p eof) SizeOf() int {
return 0
}
// EOF is a matching unit that matches EOF.
//
var EOF Ruler = eof(0)
// -----------------------------------------------------------------------------
type done int
func (p done) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
_, err = in.WriteTo(ioutil.Discard)
return
}
func (p done) RetType() reflect.Type {
return TyInterface
}
func (p done) SizeOf() int {
return -1
}
// Done is a matching unit that seeks current position to EOF.
//
var Done Ruler = done(0)
// -----------------------------------------------------------------------------
type and struct {
rs []Ruler
}
func (p *and) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
for _, r := range p.rs {
_, err = r.Match(in, ctx)
if err != nil {
return
}
}
return ctx.Dom(), nil
}
func (p *and) RetType() reflect.Type {
return TyInterface
}
func (p *and) SizeOf() int {
return -1
}
// And returns a matching unit that matches R1 R2 ... RN
//
func And(rs ...Ruler) Ruler {
if len(rs) <= 1 {
if len(rs) == 1 {
return rs[0]
}
return Nil
}
return &and{rs: rs}
}
// -----------------------------------------------------------------------------
type seq struct {
rs []Ruler
}
func (p *seq) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
ret := ctx.requireVarSlice()
for _, r := range p.rs {
v, err = r.Match(in, ctx.NewSub())
if err != nil {
return
}
ret = append(ret, v)
}
ctx.dom = ret
return ret, nil
}
func (p *seq) RetType() reflect.Type {
return tyInterfaceSlice
}
func (p *seq) SizeOf() int {
return -1
}
// Seq returns a matching unit that matches R1 R2 ... RN and returns matching result.
//
func Seq(rs ...Ruler) Ruler {
return &seq{rs: rs}
}
// -----------------------------------------------------------------------------
type act struct {
fn func(ctx *Context) error
}
func (p *act) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
err = p.fn(ctx)
if err != nil {
return
}
return ctx.Dom(), nil
}
func (p *act) RetType() reflect.Type {
return TyInterface
}
func (p *act) SizeOf() int {
return -1
}
// Do returns a matching unit that executes action fn(ctx).
//
func Do(fn func(ctx *Context) error) Ruler {
return &act{fn: fn}
}
// -----------------------------------------------------------------------------
type dyntype struct {
r func(ctx *Context) (Ruler, error)
}
func (p *dyntype) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
r, err := p.r(ctx)
if err != nil {
return
}
if r != nil {
return r.Match(in, ctx)
}
return
}
func (p *dyntype) RetType() reflect.Type {
return TyInterface
}
func (p *dyntype) SizeOf() int {
return -1
}
// Dyntype returns a dynamic matching unit.
//
func Dyntype(r func(ctx *Context) (Ruler, error)) Ruler {
return &dyntype{r: r}
}
// -----------------------------------------------------------------------------
type read struct {
n func(ctx *Context) int
r Ruler
}
func (p *read) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
n := p.n(ctx)
b := make([]byte, n)
_, err = io.ReadFull(in, b)
if err != nil {
return
}
in = bufiox.NewReaderBuffer(b)
return MatchStream(p.r, in, ctx)
}
func (p *read) RetType() reflect.Type {
return p.r.RetType()
}
func (p *read) SizeOf() int {
return -1
}
// Read returns a matching unit that reads n(ctx) bytes and matches R.
//
func Read(n func(ctx *Context) int, r Ruler) Ruler {
return &read{r: r, n: n}
}
// -----------------------------------------------------------------------------
type skip struct {
n func(ctx *Context) int
}
func (p *skip) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
n := p.n(ctx)
v, err = in.Discard(n)
return
}
func (p *skip) RetType() reflect.Type {
return tyInt
}
func (p *skip) SizeOf() int {
return -1
}
// Skip returns a matching unit that skips n(ctx) bytes.
//
func Skip(n func(ctx *Context) int) Ruler {
return &skip{n: n}
}
// -----------------------------------------------------------------------------
type ifType struct {
cond func(ctx *Context) bool
r Ruler
}
func (p *ifType) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
if p.cond(ctx) {
return p.r.Match(in, ctx)
}
return
}
func (p *ifType) RetType() reflect.Type {
return TyInterface
}
func (p *ifType) SizeOf() int {
return -1
}
// If returns a matching unit that if cond(ctx) then matches it with R.
//
func If(cond func(ctx *Context) bool, r Ruler) Ruler {
return &ifType{r: r, cond: cond}
}
// -----------------------------------------------------------------------------
type eval struct {
expr func(ctx *Context) interface{}
r Ruler
}
func (p *eval) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
fclose := false
val := p.expr(ctx)
switch v := val.(type) {
case []byte:
in = bufiox.NewReaderBuffer(v)
case io.Reader:
in = bufio.NewReader(v)
fclose = true
default:
panic("eval <expr> must return []byte or io.Reader")
}
v, err = MatchStream(p.r, in, ctx)
if fclose {
if v, ok := val.(io.Closer); ok {
v.Close()
}
}
return
}
func (p *eval) RetType() reflect.Type {
return p.r.RetType()
}
func (p *eval) SizeOf() int {
return -1
}
// Eval returns a matching unit that eval expr(ctx) and matches it with R.
//
func Eval(expr func(ctx *Context) interface{}, r Ruler) Ruler {
return &eval{r: r, expr: expr}
}
// -----------------------------------------------------------------------------
type assert struct {
expr func(ctx *Context) bool
msg string
}
func (p *assert) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
if p.expr(ctx) {
return
}
panic(p.msg)
}
func (p *assert) RetType() reflect.Type {
return TyInterface
}
func (p *assert) SizeOf() int {
return -1
}
// Assert returns a matching unit that assert expr(ctx).
//
func Assert(expr func(ctx *Context) bool, msg string) Ruler {
return &assert{msg: msg, expr: expr}
}
// -----------------------------------------------------------------------------
// A TypeVar is typeinfo of a `Struct` member.
//
type TypeVar struct {
Name string
Elem Ruler
}
// Assign assigns TypeVar.Elem.
//
func (p *TypeVar) Assign(r Ruler) error {
if p.Elem != nil {
return ErrVarAssigned
}
p.Elem = r
return nil
}
// Match is required by a matching unit. see Ruler interface.
//
func (p *TypeVar) Match(in *bufio.Reader, ctx *Context) (v interface{}, err error) {
r := p.Elem
if r == nil {
return 0, ErrVarNotAssigned
}
return r.Match(in, ctx)
}
// RetType returns matching result type.
//
func (p *TypeVar) RetType() reflect.Type {
return p.Elem.RetType()
}
// SizeOf is required by a matching unit. see Ruler interface.
//
func (p *TypeVar) SizeOf() int {
return p.Elem.SizeOf()
}
// -----------------------------------------------------------------------------