Adding upstream version 1.20.14.upstream/1.20.14upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1335 insertions, 0 deletions

diff --git a/src/archive/tar/writer_test.go b/src/archive/tar/writer_test.go
new file mode 100644
index 0000000..f6d75c5
--- /dev/null
+++ b/src/archive/tar/writer_test.go
@@ -0,0 +1,1335 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package tar
+
+import (
+	"bytes"
+	"encoding/hex"
+	"errors"
+	"io"
+	"os"
+	"path"
+	"reflect"
+	"sort"
+	"strings"
+	"testing"
+	"testing/iotest"
+	"time"
+)
+
+func bytediff(a, b []byte) string {
+	const (
+		uniqueA  = "-  "
+		uniqueB  = "+  "
+		identity = "   "
+	)
+	var ss []string
+	sa := strings.Split(strings.TrimSpace(hex.Dump(a)), "\n")
+	sb := strings.Split(strings.TrimSpace(hex.Dump(b)), "\n")
+	for len(sa) > 0 && len(sb) > 0 {
+		if sa[0] == sb[0] {
+			ss = append(ss, identity+sa[0])
+		} else {
+			ss = append(ss, uniqueA+sa[0])
+			ss = append(ss, uniqueB+sb[0])
+		}
+		sa, sb = sa[1:], sb[1:]
+	}
+	for len(sa) > 0 {
+		ss = append(ss, uniqueA+sa[0])
+		sa = sa[1:]
+	}
+	for len(sb) > 0 {
+		ss = append(ss, uniqueB+sb[0])
+		sb = sb[1:]
+	}
+	return strings.Join(ss, "\n")
+}
+
+func TestWriter(t *testing.T) {
+	type (
+		testHeader struct { // WriteHeader(hdr) == wantErr
+			hdr     Header
+			wantErr error
+		}
+		testWrite struct { // Write(str) == (wantCnt, wantErr)
+			str     string
+			wantCnt int
+			wantErr error
+		}
+		testReadFrom struct { // ReadFrom(testFile{ops}) == (wantCnt, wantErr)
+			ops     fileOps
+			wantCnt int64
+			wantErr error
+		}
+		testClose struct { // Close() == wantErr
+			wantErr error
+		}
+		testFnc any // testHeader | testWrite | testReadFrom | testClose
+	)
+
+	vectors := []struct {
+		file  string // Optional filename of expected output
+		tests []testFnc
+	}{{
+		// The writer test file was produced with this command:
+		// tar (GNU tar) 1.26
+		//   ln -s small.txt link.txt
+		//   tar -b 1 --format=ustar -c -f writer.tar small.txt small2.txt link.txt
+		file: "testdata/writer.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "small.txt",
+				Size:     5,
+				Mode:     0640,
+				Uid:      73025,
+				Gid:      5000,
+				Uname:    "dsymonds",
+				Gname:    "eng",
+				ModTime:  time.Unix(1246508266, 0),
+			}, nil},
+			testWrite{"Kilts", 5, nil},
+
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "small2.txt",
+				Size:     11,
+				Mode:     0640,
+				Uid:      73025,
+				Uname:    "dsymonds",
+				Gname:    "eng",
+				Gid:      5000,
+				ModTime:  time.Unix(1245217492, 0),
+			}, nil},
+			testWrite{"Google.com\n", 11, nil},
+
+			testHeader{Header{
+				Typeflag: TypeSymlink,
+				Name:     "link.txt",
+				Linkname: "small.txt",
+				Mode:     0777,
+				Uid:      1000,
+				Gid:      1000,
+				Uname:    "strings",
+				Gname:    "strings",
+				ModTime:  time.Unix(1314603082, 0),
+			}, nil},
+			testWrite{"", 0, nil},
+
+			testClose{nil},
+		},
+	}, {
+		// The truncated test file was produced using these commands:
+		//   dd if=/dev/zero bs=1048576 count=16384 > /tmp/16gig.txt
+		//   tar -b 1 -c -f- /tmp/16gig.txt | dd bs=512 count=8 > writer-big.tar
+		file: "testdata/writer-big.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "tmp/16gig.txt",
+				Size:     16 << 30,
+				Mode:     0640,
+				Uid:      73025,
+				Gid:      5000,
+				Uname:    "dsymonds",
+				Gname:    "eng",
+				ModTime:  time.Unix(1254699560, 0),
+				Format:   FormatGNU,
+			}, nil},
+		},
+	}, {
+		// This truncated file was produced using this library.
+		// It was verified to work with GNU tar 1.27.1 and BSD tar 3.1.2.
+		//  dd if=/dev/zero bs=1G count=16 >> writer-big-long.tar
+		//  gnutar -xvf writer-big-long.tar
+		//  bsdtar -xvf writer-big-long.tar
+		//
+		// This file is in PAX format.
+		file: "testdata/writer-big-long.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     strings.Repeat("longname/", 15) + "16gig.txt",
+				Size:     16 << 30,
+				Mode:     0644,
+				Uid:      1000,
+				Gid:      1000,
+				Uname:    "guillaume",
+				Gname:    "guillaume",
+				ModTime:  time.Unix(1399583047, 0),
+			}, nil},
+		},
+	}, {
+		// This file was produced using GNU tar v1.17.
+		//	gnutar -b 4 --format=ustar (longname/)*15 + file.txt
+		file: "testdata/ustar.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     strings.Repeat("longname/", 15) + "file.txt",
+				Size:     6,
+				Mode:     0644,
+				Uid:      501,
+				Gid:      20,
+				Uname:    "shane",
+				Gname:    "staff",
+				ModTime:  time.Unix(1360135598, 0),
+			}, nil},
+			testWrite{"hello\n", 6, nil},
+			testClose{nil},
+		},
+	}, {
+		// This file was produced using GNU tar v1.26:
+		//	echo "Slartibartfast" > file.txt
+		//	ln file.txt hard.txt
+		//	tar -b 1 --format=ustar -c -f hardlink.tar file.txt hard.txt
+		file: "testdata/hardlink.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "file.txt",
+				Size:     15,
+				Mode:     0644,
+				Uid:      1000,
+				Gid:      100,
+				Uname:    "vbatts",
+				Gname:    "users",
+				ModTime:  time.Unix(1425484303, 0),
+			}, nil},
+			testWrite{"Slartibartfast\n", 15, nil},
+
+			testHeader{Header{
+				Typeflag: TypeLink,
+				Name:     "hard.txt",
+				Linkname: "file.txt",
+				Mode:     0644,
+				Uid:      1000,
+				Gid:      100,
+				Uname:    "vbatts",
+				Gname:    "users",
+				ModTime:  time.Unix(1425484303, 0),
+			}, nil},
+			testWrite{"", 0, nil},
+
+			testClose{nil},
+		},
+	}, {
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "bad-null.txt",
+				Xattrs:   map[string]string{"null\x00null\x00": "fizzbuzz"},
+			}, headerError{}},
+		},
+	}, {
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "null\x00.txt",
+			}, headerError{}},
+		},
+	}, {
+		file: "testdata/pax-records.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "file",
+				Uname:    strings.Repeat("long", 10),
+				PAXRecords: map[string]string{
+					"path":           "FILE", // Should be ignored
+					"GNU.sparse.map": "0,0",  // Should be ignored
+					"comment":        "Hello, 世界",
+					"GOLANG.pkg":     "tar",
+				},
+			}, nil},
+			testClose{nil},
+		},
+	}, {
+		// Craft a theoretically valid PAX archive with global headers.
+		// The GNU and BSD tar tools do not parse these the same way.
+		//
+		// BSD tar v3.1.2 parses and ignores all global headers;
+		// the behavior is verified by researching the source code.
+		//
+		//	$ bsdtar -tvf pax-global-records.tar
+		//	----------  0 0      0           0 Dec 31  1969 file1
+		//	----------  0 0      0           0 Dec 31  1969 file2
+		//	----------  0 0      0           0 Dec 31  1969 file3
+		//	----------  0 0      0           0 May 13  2014 file4
+		//
+		// GNU tar v1.27.1 applies global headers to subsequent records,
+		// but does not do the following properly:
+		//	* It does not treat an empty record as deletion.
+		//	* It does not use subsequent global headers to update previous ones.
+		//
+		//	$ gnutar -tvf pax-global-records.tar
+		//	---------- 0/0               0 2017-07-13 19:40 global1
+		//	---------- 0/0               0 2017-07-13 19:40 file2
+		//	gnutar: Substituting `.' for empty member name
+		//	---------- 0/0               0 1969-12-31 16:00
+		//	gnutar: Substituting `.' for empty member name
+		//	---------- 0/0               0 2014-05-13 09:53
+		//
+		// According to the PAX specification, this should have been the result:
+		//	---------- 0/0               0 2017-07-13 19:40 global1
+		//	---------- 0/0               0 2017-07-13 19:40 file2
+		//	---------- 0/0               0 2017-07-13 19:40 file3
+		//	---------- 0/0               0 2014-05-13 09:53 file4
+		file: "testdata/pax-global-records.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag:   TypeXGlobalHeader,
+				PAXRecords: map[string]string{"path": "global1", "mtime": "1500000000.0"},
+			}, nil},
+			testHeader{Header{
+				Typeflag: TypeReg, Name: "file1",
+			}, nil},
+			testHeader{Header{
+				Typeflag:   TypeReg,
+				Name:       "file2",
+				PAXRecords: map[string]string{"path": "file2"},
+			}, nil},
+			testHeader{Header{
+				Typeflag:   TypeXGlobalHeader,
+				PAXRecords: map[string]string{"path": ""}, // Should delete "path", but keep "mtime"
+			}, nil},
+			testHeader{Header{
+				Typeflag: TypeReg, Name: "file3",
+			}, nil},
+			testHeader{Header{
+				Typeflag:   TypeReg,
+				Name:       "file4",
+				ModTime:    time.Unix(1400000000, 0),
+				PAXRecords: map[string]string{"mtime": "1400000000"},
+			}, nil},
+			testClose{nil},
+		},
+	}, {
+		file: "testdata/gnu-utf8.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹☺☻☹",
+				Mode:     0644,
+				Uid:      1000, Gid: 1000,
+				Uname:   "☺",
+				Gname:   "⚹",
+				ModTime: time.Unix(0, 0),
+				Format:  FormatGNU,
+			}, nil},
+			testClose{nil},
+		},
+	}, {
+		file: "testdata/gnu-not-utf8.tar",
+		tests: []testFnc{
+			testHeader{Header{
+				Typeflag: TypeReg,
+				Name:     "hi\x80\x81\x82\x83bye",
+				Mode:     0644,
+				Uid:      1000,
+				Gid:      1000,
+				Uname:    "rawr",
+				Gname:    "dsnet",
+				ModTime:  time.Unix(0, 0),
+				Format:   FormatGNU,
+			}, nil},
+			testClose{nil},
+		},
+		// TODO(dsnet): Re-enable this test when adding sparse support.
+		// See https://golang.org/issue/22735
+		/*
+			}, {
+				file: "testdata/gnu-nil-sparse-data.tar",
+				tests: []testFnc{
+					testHeader{Header{
+						Typeflag:    TypeGNUSparse,
+						Name:        "sparse.db",
+						Size:        1000,
+						SparseHoles: []sparseEntry{{Offset: 1000, Length: 0}},
+					}, nil},
+					testWrite{strings.Repeat("0123456789", 100), 1000, nil},
+					testClose{},
+				},
+			}, {
+				file: "testdata/gnu-nil-sparse-hole.tar",
+				tests: []testFnc{
+					testHeader{Header{
+						Typeflag:    TypeGNUSparse,
+						Name:        "sparse.db",
+						Size:        1000,
+						SparseHoles: []sparseEntry{{Offset: 0, Length: 1000}},
+					}, nil},
+					testWrite{strings.Repeat("\x00", 1000), 1000, nil},
+					testClose{},
+				},
+			}, {
+				file: "testdata/pax-nil-sparse-data.tar",
+				tests: []testFnc{
+					testHeader{Header{
+						Typeflag:    TypeReg,
+						Name:        "sparse.db",
+						Size:        1000,
+						SparseHoles: []sparseEntry{{Offset: 1000, Length: 0}},
+					}, nil},
+					testWrite{strings.Repeat("0123456789", 100), 1000, nil},
+					testClose{},
+				},
+			}, {
+				file: "testdata/pax-nil-sparse-hole.tar",
+				tests: []testFnc{
+					testHeader{Header{
+						Typeflag:    TypeReg,
+						Name:        "sparse.db",
+						Size:        1000,
+						SparseHoles: []sparseEntry{{Offset: 0, Length: 1000}},
+					}, nil},
+					testWrite{strings.Repeat("\x00", 1000), 1000, nil},
+					testClose{},
+				},
+			}, {
+				file: "testdata/gnu-sparse-big.tar",
+				tests: []testFnc{
+					testHeader{Header{
+						Typeflag: TypeGNUSparse,
+						Name:     "gnu-sparse",
+						Size:     6e10,
+						SparseHoles: []sparseEntry{
+							{Offset: 0e10, Length: 1e10 - 100},
+							{Offset: 1e10, Length: 1e10 - 100},
+							{Offset: 2e10, Length: 1e10 - 100},
+							{Offset: 3e10, Length: 1e10 - 100},
+							{Offset: 4e10, Length: 1e10 - 100},
+							{Offset: 5e10, Length: 1e10 - 100},
+						},
+					}, nil},
+					testReadFrom{fileOps{
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+					}, 6e10, nil},
+					testClose{nil},
+				},
+			}, {
+				file: "testdata/pax-sparse-big.tar",
+				tests: []testFnc{
+					testHeader{Header{
+						Typeflag: TypeReg,
+						Name:     "pax-sparse",
+						Size:     6e10,
+						SparseHoles: []sparseEntry{
+							{Offset: 0e10, Length: 1e10 - 100},
+							{Offset: 1e10, Length: 1e10 - 100},
+							{Offset: 2e10, Length: 1e10 - 100},
+							{Offset: 3e10, Length: 1e10 - 100},
+							{Offset: 4e10, Length: 1e10 - 100},
+							{Offset: 5e10, Length: 1e10 - 100},
+						},
+					}, nil},
+					testReadFrom{fileOps{
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+						int64(1e10 - blockSize),
+						strings.Repeat("\x00", blockSize-100) + strings.Repeat("0123456789", 10),
+					}, 6e10, nil},
+					testClose{nil},
+				},
+		*/
+	}, {
+		file: "testdata/trailing-slash.tar",
+		tests: []testFnc{
+			testHeader{Header{Name: strings.Repeat("123456789/", 30)}, nil},
+			testClose{nil},
+		},
+	}, {
+		// Automatically promote zero value of Typeflag depending on the name.
+		file: "testdata/file-and-dir.tar",
+		tests: []testFnc{
+			testHeader{Header{Name: "small.txt", Size: 5}, nil},
+			testWrite{"Kilts", 5, nil},
+			testHeader{Header{Name: "dir/"}, nil},
+			testClose{nil},
+		},
+	}}
+
+	equalError := func(x, y error) bool {
+		_, ok1 := x.(headerError)
+		_, ok2 := y.(headerError)
+		if ok1 || ok2 {
+			return ok1 && ok2
+		}
+		return x == y
+	}
+	for _, v := range vectors {
+		t.Run(path.Base(v.file), func(t *testing.T) {
+			const maxSize = 10 << 10 // 10KiB
+			buf := new(bytes.Buffer)
+			tw := NewWriter(iotest.TruncateWriter(buf, maxSize))
+
+			for i, tf := range v.tests {
+				switch tf := tf.(type) {
+				case testHeader:
+					err := tw.WriteHeader(&tf.hdr)
+					if !equalError(err, tf.wantErr) {
+						t.Fatalf("test %d, WriteHeader() = %v, want %v", i, err, tf.wantErr)
+					}
+				case testWrite:
+					got, err := tw.Write([]byte(tf.str))
+					if got != tf.wantCnt || !equalError(err, tf.wantErr) {
+						t.Fatalf("test %d, Write() = (%d, %v), want (%d, %v)", i, got, err, tf.wantCnt, tf.wantErr)
+					}
+				case testReadFrom:
+					f := &testFile{ops: tf.ops}
+					got, err := tw.readFrom(f)
+					if _, ok := err.(testError); ok {
+						t.Errorf("test %d, ReadFrom(): %v", i, err)
+					} else if got != tf.wantCnt || !equalError(err, tf.wantErr) {
+						t.Errorf("test %d, ReadFrom() = (%d, %v), want (%d, %v)", i, got, err, tf.wantCnt, tf.wantErr)
+					}
+					if len(f.ops) > 0 {
+						t.Errorf("test %d, expected %d more operations", i, len(f.ops))
+					}
+				case testClose:
+					err := tw.Close()
+					if !equalError(err, tf.wantErr) {
+						t.Fatalf("test %d, Close() = %v, want %v", i, err, tf.wantErr)
+					}
+				default:
+					t.Fatalf("test %d, unknown test operation: %T", i, tf)
+				}
+			}
+
+			if v.file != "" {
+				want, err := os.ReadFile(v.file)
+				if err != nil {
+					t.Fatalf("ReadFile() = %v, want nil", err)
+				}
+				got := buf.Bytes()
+				if !bytes.Equal(want, got) {
+					t.Fatalf("incorrect result: (-got +want)\n%v", bytediff(got, want))
+				}
+			}
+		})
+	}
+}
+
+func TestPax(t *testing.T) {
+	// Create an archive with a large name
+	fileinfo, err := os.Stat("testdata/small.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	hdr, err := FileInfoHeader(fileinfo, "")
+	if err != nil {
+		t.Fatalf("os.Stat: %v", err)
+	}
+	// Force a PAX long name to be written
+	longName := strings.Repeat("ab", 100)
+	contents := strings.Repeat(" ", int(hdr.Size))
+	hdr.Name = longName
+	var buf bytes.Buffer
+	writer := NewWriter(&buf)
+	if err := writer.WriteHeader(hdr); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = writer.Write([]byte(contents)); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// Simple test to make sure PAX extensions are in effect
+	if !bytes.Contains(buf.Bytes(), []byte("PaxHeaders.0")) {
+		t.Fatal("Expected at least one PAX header to be written.")
+	}
+	// Test that we can get a long name back out of the archive.
+	reader := NewReader(&buf)
+	hdr, err = reader.Next()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if hdr.Name != longName {
+		t.Fatal("Couldn't recover long file name")
+	}
+}
+
+func TestPaxSymlink(t *testing.T) {
+	// Create an archive with a large linkname
+	fileinfo, err := os.Stat("testdata/small.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	hdr, err := FileInfoHeader(fileinfo, "")
+	hdr.Typeflag = TypeSymlink
+	if err != nil {
+		t.Fatalf("os.Stat:1 %v", err)
+	}
+	// Force a PAX long linkname to be written
+	longLinkname := strings.Repeat("1234567890/1234567890", 10)
+	hdr.Linkname = longLinkname
+
+	hdr.Size = 0
+	var buf bytes.Buffer
+	writer := NewWriter(&buf)
+	if err := writer.WriteHeader(hdr); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// Simple test to make sure PAX extensions are in effect
+	if !bytes.Contains(buf.Bytes(), []byte("PaxHeaders.0")) {
+		t.Fatal("Expected at least one PAX header to be written.")
+	}
+	// Test that we can get a long name back out of the archive.
+	reader := NewReader(&buf)
+	hdr, err = reader.Next()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if hdr.Linkname != longLinkname {
+		t.Fatal("Couldn't recover long link name")
+	}
+}
+
+func TestPaxNonAscii(t *testing.T) {
+	// Create an archive with non ascii. These should trigger a pax header
+	// because pax headers have a defined utf-8 encoding.
+	fileinfo, err := os.Stat("testdata/small.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	hdr, err := FileInfoHeader(fileinfo, "")
+	if err != nil {
+		t.Fatalf("os.Stat:1 %v", err)
+	}
+
+	// some sample data
+	chineseFilename := "文件名"
+	chineseGroupname := "組"
+	chineseUsername := "用戶名"
+
+	hdr.Name = chineseFilename
+	hdr.Gname = chineseGroupname
+	hdr.Uname = chineseUsername
+
+	contents := strings.Repeat(" ", int(hdr.Size))
+
+	var buf bytes.Buffer
+	writer := NewWriter(&buf)
+	if err := writer.WriteHeader(hdr); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = writer.Write([]byte(contents)); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// Simple test to make sure PAX extensions are in effect
+	if !bytes.Contains(buf.Bytes(), []byte("PaxHeaders.0")) {
+		t.Fatal("Expected at least one PAX header to be written.")
+	}
+	// Test that we can get a long name back out of the archive.
+	reader := NewReader(&buf)
+	hdr, err = reader.Next()
+	if err != nil {
+		t.Fatal(err)
+	}
+	if hdr.Name != chineseFilename {
+		t.Fatal("Couldn't recover unicode name")
+	}
+	if hdr.Gname != chineseGroupname {
+		t.Fatal("Couldn't recover unicode group")
+	}
+	if hdr.Uname != chineseUsername {
+		t.Fatal("Couldn't recover unicode user")
+	}
+}
+
+func TestPaxXattrs(t *testing.T) {
+	xattrs := map[string]string{
+		"user.key": "value",
+	}
+
+	// Create an archive with an xattr
+	fileinfo, err := os.Stat("testdata/small.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	hdr, err := FileInfoHeader(fileinfo, "")
+	if err != nil {
+		t.Fatalf("os.Stat: %v", err)
+	}
+	contents := "Kilts"
+	hdr.Xattrs = xattrs
+	var buf bytes.Buffer
+	writer := NewWriter(&buf)
+	if err := writer.WriteHeader(hdr); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = writer.Write([]byte(contents)); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// 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)
+	}
+	hdr, err := FileInfoHeader(fileinfo, "")
+	if err != nil {
+		t.Fatalf("os.Stat: %v", err)
+	}
+	contents := strings.Repeat(" ", int(hdr.Size))
+
+	hdr.Xattrs = map[string]string{
+		"foo": "foo",
+		"bar": "bar",
+		"baz": "baz",
+		"qux": "qux",
+	}
+
+	var buf bytes.Buffer
+	writer := NewWriter(&buf)
+	if err := writer.WriteHeader(hdr); err != nil {
+		t.Fatal(err)
+	}
+	if _, err = writer.Write([]byte(contents)); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// Simple test to make sure PAX extensions are in effect
+	if !bytes.Contains(buf.Bytes(), []byte("PaxHeaders.0")) {
+		t.Fatal("Expected at least one PAX header to be written.")
+	}
+
+	// xattr bar should always appear before others
+	indices := []int{
+		bytes.Index(buf.Bytes(), []byte("bar=bar")),
+		bytes.Index(buf.Bytes(), []byte("baz=baz")),
+		bytes.Index(buf.Bytes(), []byte("foo=foo")),
+		bytes.Index(buf.Bytes(), []byte("qux=qux")),
+	}
+	if !sort.IntsAreSorted(indices) {
+		t.Fatal("PAX headers are not sorted")
+	}
+}
+
+func TestUSTARLongName(t *testing.T) {
+	// Create an archive with a path that failed to split with USTAR extension in previous versions.
+	fileinfo, err := os.Stat("testdata/small.txt")
+	if err != nil {
+		t.Fatal(err)
+	}
+	hdr, err := FileInfoHeader(fileinfo, "")
+	hdr.Typeflag = TypeDir
+	if err != nil {
+		t.Fatalf("os.Stat:1 %v", err)
+	}
+	// Force a PAX long name to be written. The name was taken from a practical example
+	// that fails and replaced ever char through numbers to anonymize the sample.
+	longName := "/0000_0000000/00000-000000000/0000_0000000/00000-0000000000000/0000_0000000/00000-0000000-00000000/0000_0000000/00000000/0000_0000000/000/0000_0000000/00000000v00/0000_0000000/000000/0000_0000000/0000000/0000_0000000/00000y-00/0000/0000/00000000/0x000000/"
+	hdr.Name = longName
+
+	hdr.Size = 0
+	var buf bytes.Buffer
+	writer := NewWriter(&buf)
+	if err := writer.WriteHeader(hdr); err != nil {
+		t.Fatal(err)
+	}
+	if err := writer.Close(); err != nil {
+		t.Fatal(err)
+	}
+	// Test that we can get a long name back out of the archive.
+	reader := NewReader(&buf)
+	hdr, err = reader.Next()
+	if err != nil && err != ErrInsecurePath {
+		t.Fatal(err)
+	}
+	if hdr.Name != longName {
+		t.Fatal("Couldn't recover long name")
+	}
+}
+
+func TestValidTypeflagWithPAXHeader(t *testing.T) {
+	var buffer bytes.Buffer
+	tw := NewWriter(&buffer)
+
+	fileName := strings.Repeat("ab", 100)
+
+	hdr := &Header{
+		Name:     fileName,
+		Size:     4,
+		Typeflag: 0,
+	}
+	if err := tw.WriteHeader(hdr); err != nil {
+		t.Fatalf("Failed to write header: %s", err)
+	}
+	if _, err := tw.Write([]byte("fooo")); err != nil {
+		t.Fatalf("Failed to write the file's data: %s", err)
+	}
+	tw.Close()
+
+	tr := NewReader(&buffer)
+
+	for {
+		header, err := tr.Next()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("Failed to read header: %s", err)
+		}
+		if header.Typeflag != TypeReg {
+			t.Fatalf("Typeflag should've been %d, found %d", TypeReg, header.Typeflag)
+		}
+	}
+}
+
+// failOnceWriter fails exactly once and then always reports success.
+type failOnceWriter bool
+
+func (w *failOnceWriter) Write(b []byte) (int, error) {
+	if !*w {
+		return 0, io.ErrShortWrite
+	}
+	*w = true
+	return len(b), nil
+}
+
+func TestWriterErrors(t *testing.T) {
+	t.Run("HeaderOnly", func(t *testing.T) {
+		tw := NewWriter(new(bytes.Buffer))
+		hdr := &Header{Name: "dir/", Typeflag: TypeDir}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatalf("WriteHeader() = %v, want nil", err)
+		}
+		if _, err := tw.Write([]byte{0x00}); err != ErrWriteTooLong {
+			t.Fatalf("Write() = %v, want %v", err, ErrWriteTooLong)
+		}
+	})
+
+	t.Run("NegativeSize", func(t *testing.T) {
+		tw := NewWriter(new(bytes.Buffer))
+		hdr := &Header{Name: "small.txt", Size: -1}
+		if err := tw.WriteHeader(hdr); err == nil {
+			t.Fatalf("WriteHeader() = nil, want non-nil error")
+		}
+	})
+
+	t.Run("BeforeHeader", func(t *testing.T) {
+		tw := NewWriter(new(bytes.Buffer))
+		if _, err := tw.Write([]byte("Kilts")); err != ErrWriteTooLong {
+			t.Fatalf("Write() = %v, want %v", err, ErrWriteTooLong)
+		}
+	})
+
+	t.Run("AfterClose", func(t *testing.T) {
+		tw := NewWriter(new(bytes.Buffer))
+		hdr := &Header{Name: "small.txt"}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatalf("WriteHeader() = %v, want nil", err)
+		}
+		if err := tw.Close(); err != nil {
+			t.Fatalf("Close() = %v, want nil", err)
+		}
+		if _, err := tw.Write([]byte("Kilts")); err != ErrWriteAfterClose {
+			t.Fatalf("Write() = %v, want %v", err, ErrWriteAfterClose)
+		}
+		if err := tw.Flush(); err != ErrWriteAfterClose {
+			t.Fatalf("Flush() = %v, want %v", err, ErrWriteAfterClose)
+		}
+		if err := tw.Close(); err != nil {
+			t.Fatalf("Close() = %v, want nil", err)
+		}
+	})
+
+	t.Run("PrematureFlush", func(t *testing.T) {
+		tw := NewWriter(new(bytes.Buffer))
+		hdr := &Header{Name: "small.txt", Size: 5}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatalf("WriteHeader() = %v, want nil", err)
+		}
+		if err := tw.Flush(); err == nil {
+			t.Fatalf("Flush() = %v, want non-nil error", err)
+		}
+	})
+
+	t.Run("PrematureClose", func(t *testing.T) {
+		tw := NewWriter(new(bytes.Buffer))
+		hdr := &Header{Name: "small.txt", Size: 5}
+		if err := tw.WriteHeader(hdr); err != nil {
+			t.Fatalf("WriteHeader() = %v, want nil", err)
+		}
+		if err := tw.Close(); err == nil {
+			t.Fatalf("Close() = %v, want non-nil error", err)
+		}
+	})
+
+	t.Run("Persistence", func(t *testing.T) {
+		tw := NewWriter(new(failOnceWriter))
+		if err := tw.WriteHeader(&Header{}); err != io.ErrShortWrite {
+			t.Fatalf("WriteHeader() = %v, want %v", err, io.ErrShortWrite)
+		}
+		if err := tw.WriteHeader(&Header{Name: "small.txt"}); err == nil {
+			t.Errorf("WriteHeader() = got %v, want non-nil error", err)
+		}
+		if _, err := tw.Write(nil); err == nil {
+			t.Errorf("Write() = %v, want non-nil error", err)
+		}
+		if err := tw.Flush(); err == nil {
+			t.Errorf("Flush() = %v, want non-nil error", err)
+		}
+		if err := tw.Close(); err == nil {
+			t.Errorf("Close() = %v, want non-nil error", err)
+		}
+	})
+}
+
+func TestSplitUSTARPath(t *testing.T) {
+	sr := strings.Repeat
+
+	vectors := []struct {
+		input  string // Input path
+		prefix string // Expected output prefix
+		suffix string // Expected output suffix
+		ok     bool   // Split success?
+	}{
+		{"", "", "", false},
+		{"abc", "", "", false},
+		{"用戶名", "", "", false},
+		{sr("a", nameSize), "", "", false},
+		{sr("a", nameSize) + "/", "", "", false},
+		{sr("a", nameSize) + "/a", sr("a", nameSize), "a", true},
+		{sr("a", prefixSize) + "/", "", "", false},
+		{sr("a", prefixSize) + "/a", sr("a", prefixSize), "a", true},
+		{sr("a", nameSize+1), "", "", false},
+		{sr("/", nameSize+1), sr("/", nameSize-1), "/", true},
+		{sr("a", prefixSize) + "/" + sr("b", nameSize),
+			sr("a", prefixSize), sr("b", nameSize), true},
+		{sr("a", prefixSize) + "//" + sr("b", nameSize), "", "", false},
+		{sr("a/", nameSize), sr("a/", 77) + "a", sr("a/", 22), true},
+	}
+
+	for _, v := range vectors {
+		prefix, suffix, ok := splitUSTARPath(v.input)
+		if prefix != v.prefix || suffix != v.suffix || ok != v.ok {
+			t.Errorf("splitUSTARPath(%q):\ngot  (%q, %q, %v)\nwant (%q, %q, %v)",
+				v.input, prefix, suffix, ok, v.prefix, v.suffix, v.ok)
+		}
+	}
+}
+
+// TestIssue12594 tests that the Writer does not attempt to populate the prefix
+// field when encoding a header in the GNU format. The prefix field is valid
+// in USTAR and PAX, but not GNU.
+func TestIssue12594(t *testing.T) {
+	names := []string{
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/file.txt",
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/file.txt",
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/333/file.txt",
+		"0/1/2/3/4/5/6/7/8/9/10/11/12/13/14/15/16/17/18/19/20/21/22/23/24/25/26/27/28/29/30/31/32/33/34/35/36/37/38/39/40/file.txt",
+		"0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000/file.txt",
+		"/home/support/.openoffice.org/3/user/uno_packages/cache/registry/com.sun.star.comp.deployment.executable.PackageRegistryBackend",
+	}
+
+	for i, name := range names {
+		var b bytes.Buffer
+
+		tw := NewWriter(&b)
+		if err := tw.WriteHeader(&Header{
+			Name: name,
+			Uid:  1 << 25, // Prevent USTAR format
+		}); err != nil {
+			t.Errorf("test %d, unexpected WriteHeader error: %v", i, err)
+		}
+		if err := tw.Close(); err != nil {
+			t.Errorf("test %d, unexpected Close error: %v", i, err)
+		}
+
+		// The prefix field should never appear in the GNU format.
+		var blk block
+		copy(blk[:], b.Bytes())
+		prefix := string(blk.toUSTAR().prefix())
+		prefix, _, _ = strings.Cut(prefix, "\x00") // Truncate at the NUL terminator
+		if blk.getFormat() == FormatGNU && len(prefix) > 0 && strings.HasPrefix(name, prefix) {
+			t.Errorf("test %d, found prefix in GNU format: %s", i, prefix)
+		}
+
+		tr := NewReader(&b)
+		hdr, err := tr.Next()
+		if err != nil && err != ErrInsecurePath {
+			t.Errorf("test %d, unexpected Next error: %v", i, err)
+		}
+		if hdr.Name != name {
+			t.Errorf("test %d, hdr.Name = %s, want %s", i, hdr.Name, name)
+		}
+	}
+}
+
+func TestWriteLongHeader(t *testing.T) {
+	for _, test := range []struct {
+		name string
+		h    *Header
+	}{{
+		name: "name too long",
+		h:    &Header{Name: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "linkname too long",
+		h:    &Header{Linkname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "uname too long",
+		h:    &Header{Uname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "gname too long",
+		h:    &Header{Gname: strings.Repeat("a", maxSpecialFileSize)},
+	}, {
+		name: "PAX header too long",
+		h:    &Header{PAXRecords: map[string]string{"GOLANG.x": strings.Repeat("a", maxSpecialFileSize)}},
+	}} {
+		w := NewWriter(io.Discard)
+		if err := w.WriteHeader(test.h); err != ErrFieldTooLong {
+			t.Errorf("%v: w.WriteHeader() = %v, want ErrFieldTooLong", test.name, err)
+		}
+	}
+}
+
+// testNonEmptyWriter wraps an io.Writer and ensures that
+// Write is never called with an empty buffer.
+type testNonEmptyWriter struct{ io.Writer }
+
+func (w testNonEmptyWriter) Write(b []byte) (int, error) {
+	if len(b) == 0 {
+		return 0, errors.New("unexpected empty Write call")
+	}
+	return w.Writer.Write(b)
+}
+
+func TestFileWriter(t *testing.T) {
+	type (
+		testWrite struct { // Write(str) == (wantCnt, wantErr)
+			str     string
+			wantCnt int
+			wantErr error
+		}
+		testReadFrom struct { // ReadFrom(testFile{ops}) == (wantCnt, wantErr)
+			ops     fileOps
+			wantCnt int64
+			wantErr error
+		}
+		testRemaining struct { // logicalRemaining() == wantLCnt, physicalRemaining() == wantPCnt
+			wantLCnt int64
+			wantPCnt int64
+		}
+		testFnc any // testWrite | testReadFrom | testRemaining
+	)
+
+	type (
+		makeReg struct {
+			size    int64
+			wantStr string
+		}
+		makeSparse struct {
+			makeReg makeReg
+			sph     sparseHoles
+			size    int64
+		}
+		fileMaker any // makeReg | makeSparse
+	)
+
+	vectors := []struct {
+		maker fileMaker
+		tests []testFnc
+	}{{
+		maker: makeReg{0, ""},
+		tests: []testFnc{
+			testRemaining{0, 0},
+			testWrite{"", 0, nil},
+			testWrite{"a", 0, ErrWriteTooLong},
+			testReadFrom{fileOps{""}, 0, nil},
+			testReadFrom{fileOps{"a"}, 0, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeReg{1, "a"},
+		tests: []testFnc{
+			testRemaining{1, 1},
+			testWrite{"", 0, nil},
+			testWrite{"a", 1, nil},
+			testWrite{"bcde", 0, ErrWriteTooLong},
+			testWrite{"", 0, nil},
+			testReadFrom{fileOps{""}, 0, nil},
+			testReadFrom{fileOps{"a"}, 0, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeReg{5, "hello"},
+		tests: []testFnc{
+			testRemaining{5, 5},
+			testWrite{"hello", 5, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeReg{5, "\x00\x00\x00\x00\x00"},
+		tests: []testFnc{
+			testRemaining{5, 5},
+			testReadFrom{fileOps{"\x00\x00\x00\x00\x00"}, 5, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeReg{5, "\x00\x00\x00\x00\x00"},
+		tests: []testFnc{
+			testRemaining{5, 5},
+			testReadFrom{fileOps{"\x00\x00\x00\x00\x00extra"}, 5, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeReg{5, "abc\x00\x00"},
+		tests: []testFnc{
+			testRemaining{5, 5},
+			testWrite{"abc", 3, nil},
+			testRemaining{2, 2},
+			testReadFrom{fileOps{"\x00\x00"}, 2, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeReg{5, "\x00\x00abc"},
+		tests: []testFnc{
+			testRemaining{5, 5},
+			testWrite{"\x00\x00", 2, nil},
+			testRemaining{3, 3},
+			testWrite{"abc", 3, nil},
+			testReadFrom{fileOps{"z"}, 0, ErrWriteTooLong},
+			testWrite{"z", 0, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testRemaining{8, 5},
+			testWrite{"ab\x00\x00\x00cde", 8, nil},
+			testWrite{"a", 0, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testWrite{"ab\x00\x00\x00cdez", 8, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testWrite{"ab\x00", 3, nil},
+			testRemaining{5, 3},
+			testWrite{"\x00\x00cde", 5, nil},
+			testWrite{"a", 0, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testWrite{"ab", 2, nil},
+			testRemaining{6, 3},
+			testReadFrom{fileOps{int64(3), "cde"}, 6, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testReadFrom{fileOps{"ab", int64(3), "cde"}, 8, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{5, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testReadFrom{fileOps{"ab", int64(3), "cdeX"}, 8, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{4, "abcd"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testReadFrom{fileOps{"ab", int64(3), "cd"}, 7, io.ErrUnexpectedEOF},
+			testRemaining{1, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{4, "abcd"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testReadFrom{fileOps{"ab", int64(3), "cde"}, 7, errMissData},
+			testRemaining{1, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{6, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testReadFrom{fileOps{"ab", int64(3), "cde"}, 8, errUnrefData},
+			testRemaining{0, 1},
+		},
+	}, {
+		maker: makeSparse{makeReg{4, "abcd"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testWrite{"ab", 2, nil},
+			testRemaining{6, 2},
+			testWrite{"\x00\x00\x00", 3, nil},
+			testRemaining{3, 2},
+			testWrite{"cde", 2, errMissData},
+			testRemaining{1, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{6, "abcde"}, sparseHoles{{2, 3}}, 8},
+		tests: []testFnc{
+			testWrite{"ab", 2, nil},
+			testRemaining{6, 4},
+			testWrite{"\x00\x00\x00", 3, nil},
+			testRemaining{3, 4},
+			testWrite{"cde", 3, errUnrefData},
+			testRemaining{0, 1},
+		},
+	}, {
+		maker: makeSparse{makeReg{3, "abc"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testRemaining{7, 3},
+			testWrite{"\x00\x00abc\x00\x00", 7, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{3, "abc"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testRemaining{7, 3},
+			testReadFrom{fileOps{int64(2), "abc", int64(1), "\x00"}, 7, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{3, ""}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testWrite{"abcdefg", 0, errWriteHole},
+		},
+	}, {
+		maker: makeSparse{makeReg{3, "abc"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testWrite{"\x00\x00abcde", 5, errWriteHole},
+		},
+	}, {
+		maker: makeSparse{makeReg{3, "abc"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testWrite{"\x00\x00abc\x00\x00z", 7, ErrWriteTooLong},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{3, "abc"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testWrite{"\x00\x00", 2, nil},
+			testRemaining{5, 3},
+			testWrite{"abc", 3, nil},
+			testRemaining{2, 0},
+			testWrite{"\x00\x00", 2, nil},
+			testRemaining{0, 0},
+		},
+	}, {
+		maker: makeSparse{makeReg{2, "ab"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testWrite{"\x00\x00", 2, nil},
+			testWrite{"abc", 2, errMissData},
+			testWrite{"\x00\x00", 0, errMissData},
+		},
+	}, {
+		maker: makeSparse{makeReg{4, "abc"}, sparseHoles{{0, 2}, {5, 2}}, 7},
+		tests: []testFnc{
+			testWrite{"\x00\x00", 2, nil},
+			testWrite{"abc", 3, nil},
+			testWrite{"\x00\x00", 2, errUnrefData},
+		},
+	}}
+
+	for i, v := range vectors {
+		var wantStr string
+		bb := new(strings.Builder)
+		w := testNonEmptyWriter{bb}
+		var fw fileWriter
+		switch maker := v.maker.(type) {
+		case makeReg:
+			fw = &regFileWriter{w, maker.size}
+			wantStr = maker.wantStr
+		case makeSparse:
+			if !validateSparseEntries(maker.sph, maker.size) {
+				t.Fatalf("invalid sparse map: %v", maker.sph)
+			}
+			spd := invertSparseEntries(maker.sph, maker.size)
+			fw = &regFileWriter{w, maker.makeReg.size}
+			fw = &sparseFileWriter{fw, spd, 0}
+			wantStr = maker.makeReg.wantStr
+		default:
+			t.Fatalf("test %d, unknown make operation: %T", i, maker)
+		}
+
+		for j, tf := range v.tests {
+			switch tf := tf.(type) {
+			case testWrite:
+				got, err := fw.Write([]byte(tf.str))
+				if got != tf.wantCnt || err != tf.wantErr {
+					t.Errorf("test %d.%d, Write(%s):\ngot  (%d, %v)\nwant (%d, %v)", i, j, tf.str, got, err, tf.wantCnt, tf.wantErr)
+				}
+			case testReadFrom:
+				f := &testFile{ops: tf.ops}
+				got, err := fw.ReadFrom(f)
+				if _, ok := err.(testError); ok {
+					t.Errorf("test %d.%d, ReadFrom(): %v", i, j, err)
+				} else if got != tf.wantCnt || err != tf.wantErr {
+					t.Errorf("test %d.%d, ReadFrom() = (%d, %v), want (%d, %v)", i, j, got, err, tf.wantCnt, tf.wantErr)
+				}
+				if len(f.ops) > 0 {
+					t.Errorf("test %d.%d, expected %d more operations", i, j, len(f.ops))
+				}
+			case testRemaining:
+				if got := fw.logicalRemaining(); got != tf.wantLCnt {
+					t.Errorf("test %d.%d, logicalRemaining() = %d, want %d", i, j, got, tf.wantLCnt)
+				}
+				if got := fw.physicalRemaining(); got != tf.wantPCnt {
+					t.Errorf("test %d.%d, physicalRemaining() = %d, want %d", i, j, got, tf.wantPCnt)
+				}
+			default:
+				t.Fatalf("test %d.%d, unknown test operation: %T", i, j, tf)
+			}
+		}
+
+		if got := bb.String(); got != wantStr {
+			t.Fatalf("test %d, String() = %q, want %q", i, got, wantStr)
+		}
+	}
+}