t.Errorf("%s: buf.Flush = %v", context, e)
			}

			written := w.Bytes()
			if len(written) != nwrite {
				t.Errorf("%s: %d bytes written", context, len(written))
			}
			for l := 0; l < len(written); l++ {
				if written[l] != data[l] {
					t.Errorf("wrong bytes written")
					t.Errorf("want=%q", data[0:len(written)])
					t.Errorf("have=%q", written)
				}
			}
		}
	}
}

	copy(b2, b)
	return b2[:len(b)]
}

// WriteTo writes data to w until the buffer is drained or an error occurs.
// The return value n is the number of bytes written; it always fits into an
// int, but it is int64 to match the io.WriterTo interface. Any error
// encountered during the write is also returned.
func (b *Buffer) WriteTo(w io.Writer) (n int64, err error) {
	b.lastRead = opInvalid

	"path"
	"sort"
	"strings"
	"time"
)

// Writer provides sequential writing of a tar archive.
// [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

		var b Buffer
		b.Write(buf[0:1])
		for i := 0; i < 5<<10; i++ {
			b.Write(buf)
			b.Read(buf)
		}
	}
}

// Check that we don't compact too often. From Issue 5154.
func BenchmarkBufferFullSmallReads(b *testing.B) {
	buf := make([]byte, 1024)
	for i := 0; i < b.N; i++ {
		var b Buffer
		b.Write(buf)
		for b.Len()+20 < b.Cap() {
			b.Write(buf[:10])
		}

// for the file metadata. [Writer] takes ownership of fh and may mutate
// its fields. The caller must not modify fh after calling [Writer.CreateHeader].
//
// This returns a [Writer] to which the file contents should be written.
// The file's contents must be written to the io.Writer before the next
// call to [Writer.Create], [Writer.CreateHeader], [Writer.CreateRaw], or [Writer.Close].

plain period and slash.
Within an assembler source file, the symbols above are written as
<code>fmt·Printf</code> and <code>math∕rand·Int</code>.
The assembly listings generated by the compilers when using the <code>-S</code> flag
show the period and slash directly instead of the Unicode replacements
required by the assemblers.
</p>

<p>
Most hand-written assembly files do not include the full package path

	-debug-gcc
		Debugging option. Trace C compiler execution and output.
	-dynimport file
		Write list of symbols imported by file. Write to
		-dynout argument or to standard output. Used by go
		build when building a cgo package.
	-dynlinker
		Write dynamic linker as part of -dynimport output.
	-dynout file
		Write -dynimport output to file.
	-dynpackage package
		Set Go package for -dynimport output.

# This file contains the initial defaults for go command configuration.
# Values set by 'go env -w' and written to the user's go/env file override these.
# The environment overrides everything else.

# Use the Go module mirror and checksum database by default.
# See https://proxy.golang.org for details.
GOPROXY=https://proxy.golang.org,direct
GOSUMDB=sum.golang.org

# Automatically download newer toolchains as directed by go.mod files.

	dw, err := w.Create("dir/")
	if err != nil {
		t.Fatal(err)
	}
	if _, err := dw.Write(nil); err != nil {
		t.Errorf("Write(nil) to directory: got %v, want nil", err)
	}
	if _, err := dw.Write([]byte("hello")); err == nil {
		t.Error(`Write("hello") to directory: got nil error, want non-nil`)
	}
}

func TestWriterDirAttributes(t *testing.T) {
	var buf bytes.Buffer
	w := NewWriter(&buf)

// accepted and all subsequent writes, and [Writer.Flush], will return the error.
// After all data has been written, the client should call the
// [Writer.Flush] method to guarantee all data has been forwarded to
// the underlying [io.Writer].
type Writer struct {
	err error
	buf []byte
	n   int
	wr  io.Writer
}