Russ Cox <******@****.***> 1629910106 -0400

func (d *digest) Reset() { *d = 1 }

// New returns a new hash.Hash32 computing the Adler-32 checksum. Its
// Sum method will lay the value out in big-endian byte order. The
// returned Hash32 also implements [encoding.BinaryMarshaler] and
// [encoding.BinaryUnmarshaler] to marshal and unmarshal the internal
// state of the hash.
func New() hash.Hash32 {
	d := new(digest)
	d.Reset()
	return d
}

	tab *Table
}

// New creates a new [hash.Hash32] computing the CRC-32 checksum using the
// polynomial represented by the [Table]. Its Sum method will lay the
// value out in big-endian byte order. The returned Hash32 also
// implements [encoding.BinaryMarshaler] and [encoding.BinaryUnmarshaler] to
// marshal and unmarshal the internal state of the hash.
func New(tab *Table) hash.Hash32 {
	if tab == IEEETable {
		ieeeOnce.Do(ieeeInit)

	// The Write method must be able to accept any amount
	// of data, but it may operate more efficiently if all writes
	// are a multiple of the block size.
	BlockSize() int
}

// Hash32 is the common interface implemented by all 32-bit hash functions.
type Hash32 interface {
	Hash
	Sum32() uint32
}

// Hash64 is the common interface implemented by all 64-bit hash functions.
type Hash64 interface {
	Hash
	Sum64() uint64

// New32 returns a new 32-bit FNV-1 [hash.Hash].
// Its Sum method will lay the value out in big-endian byte order.
func New32() hash.Hash32 {
	var s sum32 = offset32
	return &s
}

// New32a returns a new 32-bit FNV-1a [hash.Hash].
// Its Sum method will lay the value out in big-endian byte order.
func New32a() hash.Hash32 {
	var s sum32a = offset32
	return &s
}

// New64 returns a new 64-bit FNV-1 [hash.Hash].

	ErrHeader = errors.New("zlib: invalid header")
)

type reader struct {
	r            flate.Reader
	decompressor io.ReadCloser
	digest       hash.Hash32
	err          error
	scratch      [4]byte
}

// Resetter resets a ReadCloser returned by [NewReader] or [NewReaderDict]
// to switch to a new underlying Reader. This permits reusing a ReadCloser

	b.Run("poly=IEEE", benchmarkAll(NewIEEE()))
	b.Run("poly=Castagnoli", benchmarkAll(New(MakeTable(Castagnoli))))
	b.Run("poly=Koopman", benchmarkAll(New(MakeTable(Koopman))))
}

func benchmarkAll(h hash.Hash32) func(b *testing.B) {
	return func(b *testing.B) {
		for _, size := range []int{15, 40, 512, 1 << 10, 4 << 10, 32 << 10} {
			name := fmt.Sprint(size)
			if size >= 1024 {
				name = fmt.Sprintf("%dkB", size/1024)

// form of that data to an underlying writer (see NewWriter).
type Writer struct {
	w           io.Writer
	level       int
	dict        []byte
	compressor  *flate.Writer
	digest      hash.Hash32
	err         error
	scratch     [4]byte
	wroteHeader bool
}

// NewWriter creates a new Writer.
// Writes to the returned Writer are compressed and written to w.
//

	h.Write(data[:2])
	h.Write(data[2:])
	if a := h.Sum(nil); !bytes.Equal(sum, a) {
		t.Fatalf("Sum()=0x%x, but with partial writes, Sum()=0x%x", sum, a)
	}

	switch h.Size() {
	case 4:
		sum32 := h.(hash.Hash32).Sum32()
		if sum32 != binary.BigEndian.Uint32(sum) {
			t.Fatalf("Sum()=0x%x, but Sum32()=0x%x", sum, sum32)
		}
	case 8:
		sum64 := h.(hash.Hash64).Sum64()
		if sum64 != binary.BigEndian.Uint64(sum) {

	dsSeenPLTE
	dsSeentRNS
	dsSeenIDAT
	dsSeenIEND
)

const pngHeader = "\x89PNG\r\n\x1a\n"

type decoder struct {
	r             io.Reader
	img           image.Image
	crc           hash.Hash32
	width, height int
	depth         int
	palette       color.Palette
	cb            int
	stage         int
	idatLength    uint32
	tmp           [3 * 256]byte
	interlace     int