// Size constants from various tar specifications.
const (
	blockSize  = 512 // Size of each block in a tar stream
	nameSize   = 100 // Max length of the name field in USTAR format
	prefixSize = 155 // Max length of the prefix field in USTAR format

	// Max length of a special file (PAX header, GNU long name or link).
	// This matches the limit used by libarchive.
	maxSpecialFileSize = 1 << 20
)

// A Reader serves content from a ZIP archive.
type Reader struct {
	r             io.ReaderAt
	File          []*File
	Comment       string
	decompressors map[uint16]Decompressor

	// Some JAR files are zip files with a prefix that is a bash script.
	// The baseOffset field is the start of the zip file proper.
	baseOffset int64

	// fileList is a list of files sorted by ename,
	// for use by the Open method.
	fileListOnce sync.Once

type Arch struct {
	*obj.LinkArch
	// Map of instruction names to enumeration.
	Instructions map[string]obj.As
	// Map of register names to enumeration.
	Register map[string]int16
	// Table of register prefix names. These are things like R for R(0) and SPR for SPR(268).
	RegisterPrefix map[string]bool
	// RegisterNumber converts R(10) into arm.REG_R10.
	RegisterNumber func(string, int16) (int16, bool)
	// Instruction is a jump.

func (p *Parser) register(name string, prefix rune) (r1, r2 int16, scale int8, ok bool) {
	// R1 or R(1) R1:R2 R1,R2 R1+R2, or R1*scale.
	r1, ok = p.registerReference(name)
	if !ok {
		return
	}
	if prefix != 0 && prefix != '*' { // *AX is OK.
		p.errorf("prefix %c not allowed for register: %c%s", prefix, prefix, name)
	}
	c := p.peek()
	if c == ':' || c == ',' || c == '+' {

// CutPrefix returns s without the provided leading prefix byte slice
// and reports whether it found the prefix.
// If s doesn't start with prefix, CutPrefix returns s, false.
// If prefix is the empty byte slice, CutPrefix returns s, true.
//
// CutPrefix returns slices of the original slice s, not copies.
func CutPrefix(s, prefix []byte) (after []byte, found bool) {
	if !HasPrefix(s, prefix) {
		return s, false
	}

	// Check if we can use USTAR prefix/suffix splitting.
	var namePrefix string
	if prefix, suffix, ok := splitUSTARPath(hdr.Name); ok {
		namePrefix, hdr.Name = prefix, suffix
	}

	// Pack the main header.
	var f formatter
	blk := tw.templateV7Plus(hdr, f.formatString, f.formatOctal)
	f.formatString(blk.toUSTAR().prefix(), namePrefix)
	blk.setFormat(FormatUSTAR)
	if f.err != nil {

var (
	Debug      = flag.Bool("debug", false, "dump instructions as they are parsed")
	OutputFile = flag.String("o", "", "output file; default foo.o for /a/b/c/foo.s as first argument")
	TrimPath   = flag.String("trimpath", "", "remove prefix from recorded source file paths")
	Shared     = flag.Bool("shared", false, "generate code that can be linked into a shared library")

	}

	mps := detectMobileProvisionFiles(udids)
	if len(mps) == 0 {
		fail("did not find mobile provision matching device udids %q", udids)
	}

	fmt.Println("# Available provisioning profiles below.")
	fmt.Println("# NOTE: Any existing app on the device with the app id specified by GOIOS_APP_ID")
	fmt.Println("# will be overwritten when running Go programs.")
	for _, mp := range mps {
		fmt.Println()

	-import_syscall
		If set (which it is by default) import syscall in
		generated output.
	-gccgo
		Generate output for the gccgo compiler rather than the
		gc compiler.
	-gccgoprefix prefix
		The -fgo-prefix option to be used with gccgo.
	-gccgopkgpath path
		The -fgo-pkgpath option to be used with gccgo.
	-gccgo_define_cgoincomplete
		Define cgo.Incomplete locally rather than importing it from

				Name:     "gophercolor16x16.png",
				File:     "gophercolor16x16.png",
				Modified: time.Date(2010, 9, 5, 15, 52, 58, 0, timeZone(+10*time.Hour)),
				Mode:     0644,
			},
		},
	},
	{
		Name:    "test-prefix.zip",
		Comment: "This is a zipfile comment.",
		File: []ZipTestFile{
			{
				Name:     "test.txt",
				Content:  []byte("This is a test text file.\n"),