func (b *Reader) writeBuf(w io.Writer) (int64, error) {
	n, err := w.Write(b.buf[b.r:b.w])
	if n < 0 {
		panic(errNegativeWrite)
	}
	b.r += n
	return int64(n), err
}

// buffered output

// Writer implements buffering for an [io.Writer] object.
// If an error occurs writing to a [Writer], no more data will be
// accepted and all subsequent writes, and [Writer.Flush], will return the error.

		}
	})
}

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},

This is a syntactically valid Go program—it can be parsed with the Go
parser and processed by godoc—but it is not compiled directly by gc.
Instead, a separate tool, cgo, processes it to produce three output
files.  The first two, 6g.go and 6c.c, are a Go source file for 6g and
a C source file for 6c; both compile as part of the named package
(gmp, in this example).  The third, gcc.c, is a C source file for gcc;

		cmd := exec.Command(goCmd(), "list", "-e", "-deps", "-json", "std")
		cmd.Env = listEnv(w.context)
		if w.context.Dir != "" {
			cmd.Dir = w.context.Dir
		}
		cmd.Stderr = os.Stderr
		out, err := cmd.Output()
		if err != nil {
			log.Fatalf("loading imports: %v\n%s", err, out)
		}

		var stdPackages []string
		importMap := make(map[string]map[string]string)
		importDir := make(map[string]string)

		for len(output) > 0 && (output[0] < want || output[0] != want && len(output[0]) >= 5 && output[0][:5] == want[:5]) {
			if len(output[0]) >= 5 && output[0][:5] == want[:5] {
				t.Errorf("mismatched output:\nhave %s\nwant %s", output[0], want)
				output = output[1:]
				continue Diff
			}
			t.Errorf("unexpected output: %q", output[0])
			output = output[1:]
		}

    validations:
      required: true

  - type: textarea
    id: expected-behavior
    attributes:
      label: "What did you expect to see?"

				prog.Reg = p.getRegister(prog, op, &a[1])
				break
			}

			if arch.IsLoong64RDTIME(op) {
				// The Loong64 RDTIME family of instructions is a bit special,
				// in that both its register operands are outputs
				prog.To = a[0]
				if a[1].Type != obj.TYPE_REG {
					p.errorf("invalid addressing modes for 2nd operand to %s instruction, must be register", op)
					return
				}
				prog.RegTo2 = a[1].Reg
				break

  - type: input
    id: gopls-version
    attributes:
      label: "gopls version"
      description: "Output of `gopls -v version` on the command line"
    validations:
      required: true
  - type: textarea
    id: go-env
    attributes:
      label: "go env"
      description: "Output of `go env` on the command line in your workspace directory"
      render: shell
    validations:
      required: true

	for _, test := range lexTests {
		input := NewInput(test.name)
		input.Push(NewTokenizer(test.name, strings.NewReader(test.input), nil))
		result := drain(input)
		if result != test.output {
			t.Errorf("%s: got %q expected %q", test.name, result, test.output)
		}
	}
}

// lines joins the arguments together as complete lines.
func lines(a ...string) string {
	return strings.Join(a, "\n") + "\n"
}