buf2.ReadFrom(panicReader{panic: true})
}

func TestReadFromNegativeReader(t *testing.T) {
	var b Buffer
	defer func() {
		switch err := recover().(type) {
		case nil:
			t.Fatal("bytes.Buffer.ReadFrom didn't panic")
		case error:
			// this is the error string of errNegativeRead
			wantError := "bytes.Buffer: reader returned negative count from Read"
			if err.Error() != wantError {

	// an old zip32 file that was sharding inputs into the largest chunks
	// possible (or is just malicious; search the web for 42.zip).
	// If needUSize is true still, it means we didn't see a zip64 extension.
	// As long as the compressed size is not also 2³²-1 (implausible)
	// and the header is not also 2³²-1 (equally implausible),
	// accept the uncompressed size 2³²-1 as valid.

	}
	if got, want := fh2.ModifiedDate, fh.ModifiedDate; got != want {
		t.Errorf("ModifiedDate: got %d, want %d\n", got, want)
	}

	if sysfh, ok := fi.Sys().(*FileHeader); !ok && sysfh != fh {
		t.Errorf("Sys didn't return original *FileHeader")
	}
}

func TestFileHeaderRoundTrip(t *testing.T) {
	fh := &FileHeader{
		Name:             "foo.txt",
		UncompressedSize: 987654321,
		ModifiedTime:     1234,

	numSplits := 0
	const okCount = 7
	errorSplit := func(data []byte, atEOF bool) (advance int, token []byte, err error) {
		if atEOF {
			panic("didn't get enough data")
		}
		if numSplits >= okCount {
			return 0, nil, testError
		}
		numSplits++
		return 1, data[0:1], nil
	}
	// Read the data.
	const text = "abcdefghijklmnopqrstuvwxyz"

		}
		if got, want := h2.ModTime, v.h.ModTime; got != want {
			t.Errorf("i=%d: ModTime: got %v, want %v", i, got, want)
		}
		if sysh, ok := fi.Sys().(*Header); !ok || sysh != v.h {
			t.Errorf("i=%d: Sys didn't return original *Header", i)
		}
	}
}

func TestHeaderAllowedFormats(t *testing.T) {
	vectors := []struct {
		header  *Header           // Input header

	case major == "1" && minor == "0":
		is1x0 = true
	case major != "" || minor != "":
		return nil, nil // Unknown GNU sparse PAX version
	case hdr.PAXRecords[paxGNUSparseMap] != "":
		is1x0 = false // 0.0 and 0.1 did not have explicit version records, so guess
	default:
		return nil, nil // Not a PAX format GNU sparse file.
	}
	hdr.Format.mayOnlyBe(FormatPAX)

	// Update hdr from GNU sparse PAX headers.

	// Test that we can get the xattrs back out of the archive.
	reader := NewReader(&buf)
	hdr, err = reader.Next()
	if err != nil {
		t.Fatal(err)
	}
	if !reflect.DeepEqual(hdr.Xattrs, xattrs) {
		t.Fatalf("xattrs did not survive round trip: got %+v, want %+v",
			hdr.Xattrs, xattrs)
	}
}

func TestPaxHeadersSorted(t *testing.T) {
	fileinfo, err := os.Stat("testdata/small.txt")
	if err != nil {
		t.Fatal(err)
	}

	}

	if len(hexByLine) > 0 {
		var missing []string
		for key := range hexByLine {
			missing = append(missing, key)
		}
		sort.Strings(missing)
		for _, line := range missing {
			t.Errorf("%s: did not find instruction encoding", line)
		}
	}

}

func isHexes(s string) bool {
	if s == "" {
		return false
	}
	if s == "empty" {
		return true
	}