func NewReader()

in wim/wim.go [349:402]
45 lines of code
12 McCabe index (conditional complexity)

func NewReader(f io.ReaderAt) (*Reader, error) {
	r := &Reader{r: f}
	section := io.NewSectionReader(f, 0, 0xffff)
	err := binary.Read(section, binary.LittleEndian, &r.hdr)
	if err != nil {
		return nil, err
	}

	if r.hdr.ImageTag != wimImageTag {
		return nil, &ParseError{Oper: "image tag", Err: errors.New("not a WIM file")}
	}

	if r.hdr.Flags&^supportedHdrFlags != 0 {
		return nil, fmt.Errorf("unsupported WIM flags %x", r.hdr.Flags&^supportedHdrFlags)
	}

	if r.hdr.CompressionSize != 0x8000 {
		return nil, fmt.Errorf("unsupported compression size %d", r.hdr.CompressionSize)
	}

	if r.hdr.TotalParts != 1 {
		return nil, errors.New("multi-part WIM not supported")
	}

	fileData, images, err := r.readOffsetTable(&r.hdr.OffsetTable)
	if err != nil {
		return nil, err
	}

	xmlinfo, err := r.readXML()
	if err != nil {
		return nil, err
	}

	var info info
	err = xml.Unmarshal([]byte(xmlinfo), &info)
	if err != nil {
		return nil, &ParseError{Oper: "XML info", Err: err}
	}

	for i, img := range images {
		for _, imgInfo := range info.Image {
			if imgInfo.Index == i+1 {
				img.ImageInfo = imgInfo
				break
			}
		}
	}

	r.fileData = fileData
	r.Image = images
	r.XMLInfo = xmlinfo
	return r, nil
}