archive15.go
func (a *archive15) readBlockHeader() (*blockHeader15, error) {
	var err error
	b := a.buf[:7]
	r := io.Reader(a.v)
	if a.encrypted {
		salt := a.buf[:saltSize]
		_, err = io.ReadFull(r, salt)
		if err != nil {
			return nil, err
		}
		key, iv := a.getKeys(salt)
		r = newAesDecryptReader(r, key, iv)
		err = readFull(r, b)
	} else {
		_, err = io.ReadFull(r, b)
	}
	if err != nil {
		return nil, err
	}

	crc := b.uint16()
	hash := crc32.NewIEEE()
	hash.Write(b)
	h := new(blockHeader15)
	h.htype = b.byte()
	h.flags = b.uint16()
	size := b.uint16()
	if size < 7 {
		return nil, errCorruptHeader
	}
	size -= 7
	if int(size) > cap(a.buf) {
		a.buf = readBuf(make([]byte, size))
	}
	h.data = a.buf[:size]
	if err := readFull(r, h.data); err != nil {
		return nil, err
	}
	hash.Write(h.data)
	if crc != uint16(hash.Sum32()) {
		return nil, errBadHeaderCrc
	}
	if h.flags&blockHasData > 0 {
		if len(h.data) < 4 {
			return nil, errCorruptHeader
		}
		h.dataSize = int64(h.data.uint32())
	}
	if (h.htype == blockService || h.htype == blockFile) && h.flags&fileLargeData > 0 {
		if len(h.data) < 25 {
			return nil, errCorruptHeader
		}
		b := h.data[21:25]
		h.dataSize |= int64(b.uint32()) << 32
	}
	return h, nil
}
func (a *archive15) readBlockHeader() (*blockHeader15, error) {
	var err error
	b := a.buf[:7]
	r := io.Reader(a.v)
	if a.encrypted {
		salt := a.buf[:saltSize]
		_, err = io.ReadFull(r, salt)
		if err != nil {
			return nil, err
		}
		key, iv := a.getKeys(salt)
		r = newAesDecryptReader(r, key, iv)
		err = readFull(r, b)
	} else {
		_, err = io.ReadFull(r, b)
	}
	if err != nil {
		return nil, err
	}

	crc := b.uint16()
	hash := crc32.NewIEEE()
	hash.Write(b)
	h := new(blockHeader15)
	h.htype = b.byte()
	h.flags = b.uint16()
	size := b.uint16()
	if size < 7 {
		return nil, errCorruptHeader
	}
	size -= 7
	if int(size) > cap(a.buf) {
		a.buf = readBuf(make([]byte, size))
	}
	h.data = a.buf[:size]
	if err := readFull(r, h.data); err != nil {
		return nil, err
	}
	hash.Write(h.data)
	if crc != uint16(hash.Sum32()) {
		return nil, errBadHeaderCrc
	}
	if h.flags&blockHasData > 0 {
		if len(h.data) < 4 {
			return nil, errCorruptHeader
		}
		h.dataSize = int64(h.data.uint32())
	}
	if (h.htype == blockService || h.htype == blockFile) && h.flags&fileLargeData > 0 {
		if len(h.data) < 25 {
			return nil, errCorruptHeader
		}
		b := h.data[21:25]
		h.dataSize |= int64(b.uint32()) << 32
	}
	return h, nil
}
// readBlockHeader returns the next block header in the archive.
// It will return io.EOF if there were no bytes read.