type (
	sparseDatas []sparseEntry
	sparseHoles []sparseEntry
)

// validateSparseEntries reports whether sp is a valid sparse map.
// It does not matter whether sp represents data fragments or hole fragments.
func validateSparseEntries(sp []sparseEntry, size int64) bool {
	// Validate all sparse entries. These are the same checks as performed by
	// the BSD tar utility.

Go 1.22 disabled
[`ConnectionState.ExportKeyingMaterial`](/pkg/crypto/tls/#ConnectionState.ExportKeyingMaterial)
when the connection supports neither TLS 1.3 nor Extended Master Secret
(implemented in Go 1.21). It can be reenabled with the [`tlsunsafeekm`
setting](/pkg/crypto/tls/#ConnectionState.ExportKeyingMaterial).

Go 1.22 changed how the runtime interacts with transparent huge pages on Linux.

func SplitN(s, sep []byte, n int) [][]byte { return genSplit(s, sep, 0, n) }

// SplitAfterN slices s into subslices after each instance of sep and
// returns a slice of those subslices.
// If sep is empty, SplitAfterN splits after each UTF-8 sequence.
// The count determines the number of subslices to return:
//
//	n > 0: at most n subslices; the last subslice will be the unsplit remainder.

	tok := in.Stack.Next()
	if tok != '\n' {
		in.expectText("expected newline after", directive)
	}
}

func (in *Input) Next() ScanToken {
	if in.peek {
		in.peek = false
		tok := in.peekToken
		in.text = in.peekText
		return tok
	}
	// If we cannot generate a token after 100 macro invocations, we're in trouble.
	// The usual case is caught by Push, below, but be safe.

		p.errorf("register list: expected '-' after `[%s`, found %s", loName, tok)
		return
	}
	hiName := p.next().String()
	hi, ok := p.arch.Register[hiName]
	if !ok {
		p.errorf("register list: bad high register in `[%s-%s`", loName, hiName)
		return
	}
	if tok := p.next().ScanToken; tok != ']' {
		p.errorf("register list: expected ']' after `[%s-%s`, found %s", loName, hiName, tok)
	}

// The close built-in function closes a channel, which must be either
// bidirectional or send-only. It should be executed only by the sender,
// never the receiver, and has the effect of shutting down the channel after
// the last sent value is received. After the last value has been received
// from a closed channel c, any receive from c will succeed without
// blocking, returning the zero value for the channel element. The form
//
//	x, ok := <-c
//

// [Writer.WriteHeader] begins a new file with the provided [Header],
// and then Writer can be treated as an io.Writer to supply that file's data.
type Writer struct {
	w    io.Writer
	pad  int64      // Amount of padding to write after current file entry
	curr fileWriter // Writer for current file entry
	hdr  Header     // Shallow copy of Header that is safe for mutations
	blk  block      // Buffer to use as temporary local storage

			// walking the tree and copying it piecewise. If the directory tree
			// contains nested modules this could push a lot of unnecessary contents,
			// but for the golang.org/x repos it seems to be significantly (~2x)
			// faster than copying one file at a time (via filepath.WalkDir),
			// apparently due to high latency in 'adb' commands.
			if err := adb("push", modDir, deviceModDir); err != nil {
				return 0, err
			}
		} else {

			t.Fatal("looping")
		}
	}
	if s.Err() != nil {
		t.Fatal("after scan:", s.Err())
	}
}

func TestBlankLines(t *testing.T) {
	s := NewScanner(strings.NewReader(strings.Repeat("\n", 1000)))
	for count := 0; s.Scan(); count++ {
		if count > 2000 {
			t.Fatal("looping")
		}
	}
	if s.Err() != nil {
		t.Fatal("after scan:", s.Err())
	}
}

type countdown int

// and then Reader can be treated as an io.Reader to access the file's data.
type Reader struct {
	r    io.Reader
	pad  int64      // Amount of padding (ignored) after current file entry
	curr fileReader // Reader for current file entry
	blk  block      // Buffer to use as temporary local storage

	// err is a persistent error.