log.Fatal(err)
		}
	}()
	go func() {
		defer wg.Done()
		defer r.Close()
		b := make([]byte, 1<<20)
		// This ReadFull will likely be interrupted by a signal,
		// as the other goroutine spins before writing anything.
		if _, err := io.ReadFull(r, b); err != nil {
			log.Fatal(err)
		}
		// Spin after reading half the data so that the Write
		// in the other goroutine will likely be interrupted

		if len(skip) == 0 {
			skip = make([]byte, chunk)
		}
		if _, err := io.ReadFull(r.r, skip); err != nil {
			return r.wrapNonEOFError(relativeOffset, err)
		}
		relativeOffset += chunk
		size -= chunk
	}
	if size > 0 {
		if len(skip) == 0 {
			skip = make([]byte, size)
		}
		if _, err := io.ReadFull(r.r, skip); err != nil {
			return r.wrapNonEOFError(relativeOffset, err)
		}

	n, err := ReadFull(mr2, buf)
	if got := string(buf[:n]); got != "1234" || err != nil {
		t.Errorf(`ReadFull(mr2) = (%q, %v), want ("1234", nil)`, got, err)
	}

	// Consume the rest of r2 via mr1.
	// This should not panic even though mr2 cleared r1.
	n, err = ReadFull(mr1, buf)
	if got := string(buf[:n]); got != "5678" || err != nil {
		t.Errorf(`ReadFull(mr1) = (%q, %v), want ("5678", nil)`, got, err)

		r.readFull(r.tmp[:n])
	} else if n <= int64(r.b.Buffered()) {
		// Even though the data is not small, it has already been read.
		// Advance the buffer instead of seeking.
		for n > int64(len(r.tmp)) {
			r.readFull(r.tmp[:])
			n -= int64(len(r.tmp))
		}
		r.readFull(r.tmp[:n])
	} else {
		// Seek, giving up buffered data.
		r.b.MustSeek(r.offset+n, io.SeekStart)

	f, err := OsOpenFile(name, readMode, 0o666)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	st, err := f.Stat()
	if err != nil {
		return io.ReadAll(f)
	}
	dst := make([]byte, st.Size())
	_, err = io.ReadFull(f, dst)
	return dst, err

//   - On wasip1/wasm, Reader uses random_get from wasi_snapshot_preview1.
var Reader io.Reader

// Read is a helper function that calls Reader.Read using io.ReadFull.
// On return, n == len(b) if and only if err == nil.
func Read(b []byte) (n int, err error) {
	return io.ReadFull(Reader, b)
}

// batched returns a function that calls f to populate a []byte by chunking it
// into subslices of, at most, readMax bytes.

// Extensions.
const (
	eText           = 0x01 // Plain Text
	eGraphicControl = 0xF9 // Graphic Control
	eComment        = 0xFE // Comment
	eApplication    = 0xFF // Application
)

func readFull(r io.Reader, b []byte) error {
	_, err := io.ReadFull(r, b)
	if err == io.EOF {
		err = io.ErrUnexpectedEOF
	}
	return err
}

func readByte(r io.ByteReader) (byte, error) {
	b, err := r.ReadByte()
	if err == io.EOF {

	"compress/flate"
	"io"
	"testing"
)

func TestRead(t *testing.T) {
	var n int = 4e6
	if testing.Short() {
		n = 1e5
	}
	b := make([]byte, n)
	n, err := io.ReadFull(Reader, b)
	if n != len(b) || err != nil {
		t.Fatalf("ReadFull(buf) = %d, %s", n, err)
	}

	var z bytes.Buffer
	f, _ := flate.NewWriter(&z, 5)
	f.Write(b)
	f.Close()
	if z.Len() < len(b)*99/100 {

					q := make([]byte, alignQ+n, alignQ+n+10)[alignQ:]
					if n&1 != 0 {
						p = p[:n]
					} else {
						q = q[:n]
					}
					if _, err := io.ReadFull(rand.Reader, p); err != nil {
						t.Fatal(err)
					}
					if _, err := io.ReadFull(rand.Reader, q); err != nil {
						t.Fatal(err)
					}

					d := make([]byte, alignD+n, alignD+n+10)
					for i := range d {
						d[i] = 0xdd
					}

	hdr.OS = z.buf[9]
	z.digest = crc32.ChecksumIEEE(z.buf[:10])

	if flg&flagExtra != 0 {
		if _, err = io.ReadFull(z.r, z.buf[:2]); err != nil {
			return hdr, noEOF(err)
		}
		z.digest = crc32.Update(z.digest, crc32.IEEETable, z.buf[:2])
		data := make([]byte, le.Uint16(z.buf[:2]))
		if _, err = io.ReadFull(z.r, data); err != nil {
			return hdr, noEOF(err)
		}
		z.digest = crc32.Update(z.digest, crc32.IEEETable, data)