Exemplo n.º 1
0
Arquivo: copy.go Projeto: tsavola/wag
func copySection(w io.Writer, r reader.Reader, expectId byte) (ok bool) {
	store := storer{w}
	load := loader.L{Reader: r}

loop:
	for {
		id, err := load.ReadByte()
		if err != nil {
			if err == io.EOF {
				return
			}
			panic(err)
		}

		switch {
		case id == sectionids.Unknown:
			payloadLen := load.Varuint32()
			if _, err := io.CopyN(ioutil.Discard, load, int64(payloadLen)); err != nil {
				panic(err)
			}

		case id == expectId:
			store.Byte(id)
			break loop

		default:
			load.UnreadByte()
			return
		}
	}

	payloadLen := load.Varuint32()
	store.Varuint32(payloadLen)

	if _, err := io.CopyN(store, load, int64(payloadLen)); err != nil {
		panic(err)
	}

	ok = true
	return
}
Exemplo n.º 2
0
func (m moduleLoader) loadUntil(load loader.L, untilSection byte) byte {
	var header struct {
		MagicNumber uint32
		Version     uint32
	}
	if err := binary.Read(load, binary.LittleEndian, &header); err != nil {
		panic(err)
	}
	if header.MagicNumber != moduleMagicNumber {
		panic(errors.New("not a WebAssembly module"))
	}
	if header.Version != moduleVersion {
		panic(fmt.Errorf("unsupported module version: %d", header.Version))
	}

	var skipSection func(byte, uint32) error

	if m.UnknownSectionLoader != nil {
		skipSection = func(id byte, payloadLen uint32) (err error) {
			if id == sectionids.Unknown {
				err = m.UnknownSectionLoader(load, payloadLen)
			} else {
				_, err = io.CopyN(ioutil.Discard, load, int64(payloadLen))
			}
			return
		}
	} else {
		skipSection = func(id byte, payloadLen uint32) (err error) {
			_, err = io.CopyN(ioutil.Discard, load, int64(payloadLen))
			return
		}
	}

	var seenId byte

	for {
		id, err := load.ReadByte()
		if err != nil {
			if err == io.EOF {
				return 0
			}
			panic(err)
		}

		if id != sectionids.Unknown {
			if id <= seenId {
				panic(fmt.Errorf("section 0x%x follows section 0x%x", id, seenId))
			}
			seenId = id
		}

		if id >= untilSection {
			load.UnreadByte()
			return id
		}

		payloadLen := load.Varuint32()

		if f := sectionLoaders[id]; f != nil {
			f(m, load)
		} else if err := skipSection(id, payloadLen); err != nil {
			panic(err)
		}
	}
}