//
	// Analyzers must use this function (if provided) instead of
	// accessing the file system directly. This allows a driver to
	// provide a virtualized file tree (including, for example,
	// unsaved editor buffers) and to track dependencies precisely
	// to avoid unnecessary recomputation.
	ReadFile func(filename string) ([]byte, error)

	// -- facts --

	// ImportObjectFact retrieves a fact associated with obj.

	b.n = 0
	return nil
}

// Available returns how many bytes are unused in the buffer.
func (b *Writer) Available() int { return len(b.buf) - b.n }

// AvailableBuffer returns an empty buffer with b.Available() capacity.
// This buffer is intended to be appended to and
// passed to an immediately succeeding [Writer.Write] call.
// The buffer is only valid until the next write operation on b.
func (b *Writer) AvailableBuffer() []byte {

	after substituting variables from the script environment.
	File1 can be 'stdout' or 'stderr' to compare the script's
	stdout or stderr buffer.

cp src... dst
	copy files to a target file or directory

	src can include 'stdout' or 'stderr' to copy from the
	script's stdout or stderr buffer.

echo string...
	display a line of text


env [key[=value]...]
	set or log the values of environment variables

	//
	// If the command produces output or can be run in the background, run returns
	// a WaitFunc that will be called to obtain the result of the command and
	// update the engine's stdout and stderr buffers.
	//
	// Run itself and the returned WaitFunc may inspect and/or modify the State,
	// but the State's methods must not be called concurrently after Run has
	// returned.
	//

//sys	VirtualQuery(address uintptr, buffer *MemoryBasicInformation, length uintptr) (err error) = kernel32.VirtualQuery
//sys	VirtualQueryEx(process Handle, address uintptr, buffer *MemoryBasicInformation, length uintptr) (err error) = kernel32.VirtualQueryEx
//sys	ReadProcessMemory(process Handle, baseAddress uintptr, buffer *byte, size uintptr, numberOfBytesRead *uintptr) (err error) = kernel32.ReadProcessMemory

	Left   int16
	Top    int16
	Right  int16
	Bottom int16
}

// Used with GetConsoleScreenBuffer to retrieve information about a console
// screen buffer. See
// https://docs.microsoft.com/en-us/windows/console/console-screen-buffer-info-str
// for details.

type ConsoleScreenBufferInfo struct {
	Size              Coord
	CursorPosition    Coord
	Attributes        uint16

	}
	if buffered := wr.Buffered(); buffered != wantBuffered {
		t.Fatalf("Buffered = %v; want %v", buffered, wantBuffered)
	}
}

func BenchmarkReaderCopyOptimal(b *testing.B) {
	// Optimal case is where the underlying reader implements io.WriterTo
	srcBuf := bytes.NewBuffer(make([]byte, 8192))
	src := NewReader(srcBuf)
	dstBuf := new(bytes.Buffer)
	dst := onlyWriter{dstBuf}

	ac.ctr[1] = byteorder.BeUint64(iv[8:]) // low bits
	ac.buffer = ac.storage[:0]
	return &ac
}

func (c *aesctr) refill() {
	// Fill up the buffer with an incrementing count.
	c.buffer = c.storage[:streamBufferSize]
	c0, c1 := c.ctr[0], c.ctr[1]
	for i := 0; i < streamBufferSize; i += 16 {
		byteorder.BePutUint64(c.buffer[i+0:], c0)
		byteorder.BePutUint64(c.buffer[i+8:], c1)

		// Increment in big endian: c0 is high, c1 is low.

	lineBuf bytes.Buffer // Buffer for incomplete lines
}

func (f *testJSONFilter) Write(b []byte) (int, error) {
	bn := len(b)

	// Process complete lines, and buffer any incomplete lines.
	for len(b) > 0 {
		nl := bytes.IndexByte(b, '\n')
		if nl < 0 {
			f.lineBuf.Write(b)
			break
		}
		var line []byte
		if f.lineBuf.Len() > 0 {
			// We have buffered data. Add the rest of the line from b and

	// Confirm that when Reader panics, the empty buffer remains empty
	var buf2 Buffer
	defer func() {
		recover()
		check(t, "TestReadFromPanicReader (2)", &buf2, "")
	}()
	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: