Golang errors.Newf函數代碼示例

// Samples 'k' unique ints from the range [0, n)
func SampleInts(n int, k int) (res []int, err error) {
	if k < 0 {
		err = errors.Newf("invalid sample size k")
		return
	}

	if n < k {
		err = errors.Newf("sample size k larger than n")
		return
	}

	picked := set.NewSet()
	for picked.Len() < k {
		i := Intn(n)
		picked.Add(i)
	}

	res = make([]int, k)
	e := 0
	for i := range picked.Iter() {
		res[e] = i.(int)
		e++
	}

	return
}

func serializeClauses(
	clauses []Clause,
	separator []byte,
	out *bytes.Buffer) (err error) {

	if clauses == nil || len(clauses) == 0 {
		return errors.Newf("Empty clauses.  Generated sql: %s", out.String())
	}

	if clauses[0] == nil {
		return errors.Newf("nil clause.  Generated sql: %s", out.String())
	}
	if err = clauses[0].SerializeSql(out); err != nil {
		return
	}

	for _, c := range clauses[1:] {
		out.Write(separator)

		if c == nil {
			return errors.Newf("nil clause.  Generated sql: %s", out.String())
		}
		if err = c.SerializeSql(out); err != nil {
			return
		}
	}

	return nil
}

func (c *aliasColumn) SerializeSqlForColumnList(includeTableName bool, database Database, out *bytes.Buffer) error {
	if !validIdentifierName(c.name) {
		return errors.Newf(
			"Invalid alias name `%s`.  Generated sql: %s",
			c.name,
			out.String())
	}
	if c.expression == nil {
		return errors.Newf(
			"Cannot alias a nil expression.  Generated sql: %s",
			out.String())
	}

	out.WriteByte('(')
	if c.expression == nil {
		return errors.Newf("nil alias clause.  Generate sql: %s", out.String())
	}
	if err := c.expression.SerializeSql(database, out); err != nil {
		return err
	}
	out.WriteString(") AS ")
	out.WriteRune(database.EscapeCharacter())
	out.WriteString(c.name)
	out.WriteRune(database.EscapeCharacter())
	return nil
}

func (c *aliasColumn) SerializeSqlForColumnList(out *bytes.Buffer) error {
	if !validIdentifierName(c.name) {
		return errors.Newf(
			"Invalid alias name `%s`.  Generated sql: %s",
			c.name,
			out.String())
	}
	if c.expression == nil {
		return errors.Newf(
			"Cannot alias a nil expression.  Generated sql: %s",
			out.String())
	}

	out.WriteByte('(')
	if c.expression == nil {
		return errors.Newf("nil alias clause.  Generate sql: %s", out.String())
	}
	if err := c.expression.SerializeSql(out); err != nil {
		return err
	}
	out.WriteString(") AS `")
	out.WriteString(c.name)
	out.WriteByte('`')
	return nil
}

func (p *baseRowsEventParser) parseRowsHeader(raw *RawV4Event) (
	id uint64,
	flags uint16,
	extraInfo []byte,
	width int,
	remaining []byte,
	err error) {

	if p.context == nil {
		return 0, 0, nil, 0, nil, &TableContextNotSetError{
			errors.New("Table context not set"),
		}
	}

	data := raw.FixedLengthData()

	id = LittleEndian.Uint48(data)

	if id != p.context.TableId() {
		return 0, 0, nil, 0, nil, errors.Newf(
			"mismatch table id (event: %d; context: %d name: %s)",
			id,
			p.context.TableId(),
			p.context.TableName())
	}

	flags = LittleEndian.Uint16(data[6:])

	remaining = raw.VariableLengthData()

	if p.version == mysql_proto.RowsEventVersion_V1 {
		extraInfo = nil
	} else {
		extraInfoBlobLen := LittleEndian.Uint16(data[8:])
		extraInfo, remaining, err = p.parseExtraInfoBlob(
			extraInfoBlobLen,
			remaining)
		if err != nil {
			return 0, 0, nil, 0, nil, err
		}
	}

	w, remaining, err := readFieldLength(remaining)
	if err != nil {
		return 0, 0, nil, 0, nil, err
	}

	if w > uint64(p.context.NumColumns()) {
		return 0, 0, nil, 0, nil, errors.Newf(
			"row width (%d / %d) greater than # of columns (%d) in table %s",
			w,
			width,
			p.context.NumColumns(),
			string(p.context.TableName()))
	}

	return id, flags, extraInfo, int(w), remaining, nil
}

func (s *Source) validate() (err error) {
	if strings.ToLower(s.Hash) == "skip" {
		return
	}

	file, err := os.Open(s.Path)
	if err != nil {
		err = &HashError{
			errors.Wrap(err, "source: Failed to open file for hash"),
		}
		return
	}
	defer file.Close()

	var hash hash.Hash
	switch len(s.Hash) {
	case 32:
		hash = md5.New()
	case 40:
		hash = sha1.New()
	case 64:
		hash = sha256.New()
	case 128:
		hash = sha512.New()
	default:
		err = &HashError{
			errors.Newf("source: Unknown hash type for hash '%s'", s.Hash),
		}
		return
	}

	_, err = io.Copy(hash, file)
	if err != nil {
		return
	}

	sum := hash.Sum([]byte{})

	hexSum := fmt.Sprintf("%x", sum)

	if hexSum != s.Hash {
		err = &HashError{
			errors.Newf("source: Hash verification failed for '%s'", s.Source),
		}
		return
	}

	return
}

// See ResourcePool for documentation.
func (p *MultiResourcePool) Register(resourceLocation string) error {
	if resourceLocation == "" {
		return errors.New("Registering invalid resource location")
	}

	p.rwMutex.Lock()
	defer p.rwMutex.Unlock()

	if p.isLameDuck {
		return errors.Newf(
			"Cannot register %s to lame duck resource pool",
			resourceLocation)
	}

	if _, inMap := p.locationPools[resourceLocation]; inMap {
		return nil
	}

	pool := p.createPool(p.options)
	if err := pool.Register(resourceLocation); err != nil {
		return err
	}

	p.locationPools[resourceLocation] = pool
	return nil
}

// Writes an image to a file. The extension of the file is used to determine the
// encoding method.
func CreateImage(i image.Image, file string) error {
	ext := filepath.Ext(file)
	m := mime.TypeByExtension(ext)

	switch m {
	case "image/jpeg", "image/png", "image/tiff":
	default:
		return errors.Newf("unsupported extension/mime type: %s %s", ext, m)
	}

	f, err := os.Create(file)
	if err != nil {
		return errors.Wrap(err, "could not create file")
	}
	defer f.Close()

	switch m {
	case "image/jpeg":
		err = jpeg.Encode(f, i, &jpeg.Options{Quality: 98})
	case "image/png":
		err = png.Encode(f, i)
	case "image/tiff":
		err = tiff.Encode(f, i, &tiff.Options{Compression: tiff.Deflate, Predictor: true})
	default:
		panic("unreachable")
	}
	if err != nil {
		return errors.Wrap(err, "could not encode image")
	}

	return nil
}

// Peek returns a slice of the look ahead buffer which holds numBytes
// number of bytes.  If the look ahead buffer does not already hold enough
// bytes, it will read from the underlying reader to populate the rest.
// NOTE: the returned slice is not a copy of the raw buffer.
func (b *LookAheadBuffer) Peek(numBytes int) ([]byte, error) {
	if numBytes < 0 {
		return nil, errors.New("Cannot fill negative numBytes")
	}
	if numBytes > len(b.buffer) {
		return nil, errors.Newf(
			"Buffer full (buffer size: %d n: %d)",
			len(b.buffer),
			numBytes)
	}

	var err error
	var numRead int
	if b.bytesBuffered < numBytes {
		numRead, err = io.ReadAtLeast(
			b.src,
			b.buffer[b.bytesBuffered:],
			numBytes-b.bytesBuffered)
		if err != nil {
			if err == io.ErrUnexpectedEOF {
				// ErrUnexpectedEOF is a terrible error only returned by
				// ReadAtLeast.  Return EOF (i.e., the original error) instead
				// ErrUnexpectedEOF since no one ever checks for this.
				err = io.EOF
			}
		}
	}

	b.bytesBuffered += numRead

	if numBytes > b.bytesBuffered {
		numBytes = b.bytesBuffered
	}
	return b.buffer[:numBytes], err
}

// See ConnectionPool for documentation.
func (p *MultiConnectionPool) Register(network string, address string) error {
	if network == "" && address == "" {
		return errors.New("Registering invalid (network, address)")
	}

	key := NetworkAddress{
		Network: network,
		Address: address,
	}

	p.rwMutex.Lock()
	defer p.rwMutex.Unlock()

	if p.isLameDuck {
		return errors.Newf(
			"Cannot register (%s, %s) to lame duck connection pool",
			network,
			address)
	}

	if _, inMap := p.addressPools[key]; inMap {
		return nil
	}

	pool := p.createPool(p.options)
	if err := pool.Register(network, address); err != nil {
		return err
	}

	p.addressPools[key] = pool
	return nil
}

func GetPacker(pac *pack.Pack, distro, release string) (
	pcker Packer, err error) {

	switch constants.DistroPack[distro] {
	case "pacman":
		pcker = &pacman.Pacman{
			Pack: pac,
		}
	case "debian":
		pcker = &debian.Debian{
			Pack: pac,
		}
	case "redhat":
		pcker = &redhat.Redhat{
			Pack: pac,
		}
	default:
		system := distro
		if release != "" {
			system += "-" + release
		}

		err = &UnknownSystem{
			errors.Newf("packer: Unkown system %s", system),
		}
		return
	}

	return
}

func (conj *conjunctExpression) SerializeSql(out *bytes.Buffer) (err error) {
	if len(conj.expressions) == 0 {
		return errors.Newf(
			"Empty conjunction.  Generated sql: %s",
			out.String())
	}

	clauses := make([]Clause, len(conj.expressions), len(conj.expressions))
	for i, expr := range conj.expressions {
		clauses[i] = expr
	}

	use_parentheses := len(clauses) > 1
	if use_parentheses {
		out.WriteByte('(')
	}

	if err = serializeClauses(clauses, conj.conjunction, out); err != nil {
		return
	}

	if use_parentheses {
		out.WriteByte(')')
	}

	return nil
}

func (arith *arithmeticExpression) SerializeSql(out *bytes.Buffer) (err error) {
	if len(arith.expressions) == 0 {
		return errors.Newf(
			"Empty arithmetic expression.  Generated sql: %s",
			out.String())
	}

	clauses := make([]Clause, len(arith.expressions), len(arith.expressions))
	for i, expr := range arith.expressions {
		clauses[i] = expr
	}

	useParentheses := len(clauses) > 1
	if useParentheses {
		out.WriteByte('(')
	}

	if err = serializeClauses(clauses, arith.operator, out); err != nil {
		return
	}

	if useParentheses {
		out.WriteByte(')')
	}

	return nil
}

func (*singletonSuite) TestGet(c *C) {
	callCount := 0
	init := func() (interface{}, error) {
		callCount++

		if callCount < 2 {
			return nil, errors.Newf("fail")
		}
		v := 5
		return &v, nil
	}

	s := NewSingleton(init)
	// Verify init hasn't been called yet
	c.Assert(callCount, Equals, 0)

	// Verify init gets called with Get()
	_, err := s.Get()
	c.Assert(err, NotNil)
	c.Assert(callCount, Equals, 1)

	// Verify failed init gets retried with Get()
	data1, err := s.Get()
	c.Assert(err, IsNil)
	c.Assert(callCount, Equals, 2)
	c.Assert(*(data1.(*int)), Equals, 5)

	// Verify that subsequent Get() after a successful one return the same object and don't call
	// init
	data2, err := s.Get()
	c.Assert(err, IsNil)
	c.Assert(callCount, Equals, 2)
	c.Assert(data1, Equals, data2)
}

func Parse() (err error) {
	flag.Parse()

	cmd := flag.Arg(0)
	switch cmd {
	case "build":
		err = Build()
	case "create":
		err = Create()
	case "project":
		err = Project()
	case "pull":
		err = utils.PullContainers()
	case "genkey":
		err = GenKey()
	case "list-targets":
		err = ListTargets()
	default:
		err = &UnknownCommand{
			errors.Newf("cmd: Unknown command '%s'", cmd),
		}
	}

	return
}