})
	e.Int(len(packages))
	packagesPos := e.Pos()
	for _, p := range packages {
		e.String(p.dir)
		e.Int(0)
	}
	for i, p := range packages {
		e.IntAt(e.Pos(), packagesPos+8*i+4)
		encodePackage(e, p)
	}
	e.IntAt(e.Pos(), stringTableOffsetPos)
	e.Bytes(e.stringTable)
	e.Bytes([]byte{0xFF}) // end of string table marker
	return e.b
}

func encodePackageBytes(p *rawPackage) []byte {

	pos := sf.pos + sourceFileNumPlusBuildConstraints
	n := sf.d.intAt(pos)
	pos += 4
	ret := make([]string, n)
	for i := 0; i < n; i++ {
		ret[i] = sf.d.stringAt(pos)
		pos += 4
	}
	return ret
}

func (sf *sourceFile) importsOffset() int {
	pos := sf.pos + sourceFileNumPlusBuildConstraints
	n := sf.d.intAt(pos)
	// each build constraint is 1 uint32
	return pos + 4 + n*4
}