img3

type Header struct {
	Magic        [4]byte // ASCII_LE("Img3")
	FullSize     uint32  // full size of fw image
	SizeNoPack   uint32  // size of fw image without header
	SigCheckArea uint32  // although that is just my name for it, this is the
	// size of the start of the data section (the code) up to
	// the start of the RSA signature (SHSH section)
	Ident [4]byte // identifier of image, used when bootrom is parsing images

}

type Img3 struct {
	Header
	Tags []Tag // continues until end of file
}

type Tag struct {
	TagHeader
	Data []byte // [dataLength]
	Pad  []byte // Typically padded to 4 byte multiple [totalLength - dataLength - 12]
}

type TagHeader struct {
	Magic       [4]byte // see below
	TotalLength uint32  // length of tag including "magic" and these two length values
	DataLength  uint32  // length of tag data
}