Golang Reader.Read方法代码示例

// ReadFrom implements io.ReaderFrom.
func (b *Writer) ReadFrom(r io.Reader) (n int64, err error) {
	if b.Buffered() == 0 {
		if w, ok := b.wr.(io.ReaderFrom); ok {
			return w.ReadFrom(r)
		}
	}
	var m int
	for {
		m, err = r.Read(b.buf[b.n:])
		if m == 0 {
			break
		}
		b.n += m
		n += int64(m)
		if b.Available() == 0 {
			if err1 := b.Flush(); err1 != nil {
				return n, err1
			}
		}
		if err != nil {
			break
		}
	}
	if err == io.EOF {
		err = nil
	}
	return n, err
}

func messageCopy(ws *websocket.Conn, r io.Reader, base64Encode, ping bool, timeout time.Duration) error {
	buf := make([]byte, 2048)
	if ping {
		resetTimeout(ws, timeout)
		if err := websocket.Message.Send(ws, []byte{}); err != nil {
			return err
		}
	}
	for {
		resetTimeout(ws, timeout)
		n, err := r.Read(buf)
		if err != nil {
			if err == io.EOF {
				return nil
			}
			return err
		}
		if n > 0 {
			if base64Encode {
				if err := websocket.Message.Send(ws, base64.StdEncoding.EncodeToString(buf[:n])); err != nil {
					return err
				}
			} else {
				if err := websocket.Message.Send(ws, buf[:n]); err != nil {
					return err
				}
			}
		}
	}
}

func pipe(r io.Reader, w io.Writer) {
	var err error
	defer func() {
		if err != nil && err != io.EOF {
			log.Print(err)
		}
	}()

	firstChunk := true
	buf := make([]byte, cmdline.bufsize)
	for {
		var n int
		n, err = r.Read(buf)
		if n <= 0 {
			return
		}

		if firstChunk {
			firstChunk = false
		} else if cmdline.maxPostDelay > 0 {
			delay(cmdline.minPostDelay, cmdline.maxPostDelay)
		}

		_, err = w.Write(buf[:n])
		if err != nil {
			return
		}
	}
}

func (this *packetClientLoginEncryptRequestCodec17) Decode(reader io.Reader, util []byte) (decode packet.Packet, err error) {
	packetClientLoginEncryptRequest := new(PacketClientLoginEncryptRequest)
	packetClientLoginEncryptRequest.ServerId, err = packet.ReadString(reader, util)
	if err != nil {
		return
	}
	publicKeyLength, err := packet.ReadUint16(reader, util)
	if err != nil {
		return
	}
	packetClientLoginEncryptRequest.PublicKey = make([]byte, publicKeyLength)
	_, err = reader.Read(packetClientLoginEncryptRequest.PublicKey)
	if err != nil {
		return
	}
	verifyTokenLength, err := packet.ReadUint16(reader, util)
	if err != nil {
		return
	}
	packetClientLoginEncryptRequest.VerifyToken = make([]byte, verifyTokenLength)
	_, err = reader.Read(packetClientLoginEncryptRequest.VerifyToken)
	if err != nil {
		return
	}
	decode = packetClientLoginEncryptRequest
	return
}

// ReadFrom implements io.ReaderFrom.
func (b *Writer) ReadFrom(r io.Reader) (n int64, err error) {
	if b.Buffered() == 0 {
		if w, ok := b.wr.(io.ReaderFrom); ok {
			return w.ReadFrom(r)
		}
	}
	var m int
	for {
		if b.Available() == 0 {
			if err1 := b.Flush(); err1 != nil {
				return n, err1
			}
		}
		m, err = r.Read(b.buf[b.n:])
		if m == 0 {
			break
		}
		b.n += m
		n += int64(m)
		if err != nil {
			break
		}
	}
	if err == io.EOF {
		// If we filled the buffer exactly, flush pre-emptively.
		if b.Available() == 0 {
			err = b.Flush()
		} else {
			err = nil
		}
	}
	return n, err
}

func (s *buffer) Get(r io.Reader, n int) ([]byte, error) {
	// compress the data we already have
	if s.begin > defaultBufferSize {
		copy(s.buf[:], s.buf[s.begin:s.end])
		s.end -= s.begin
		s.begin = 0
	}

	toget := len(s.buf) - s.end
	if toget > defaultBufferSize {
		toget = defaultBufferSize
	}

	// only get up to the buffer size
	if n > defaultBufferSize {
		n = defaultBufferSize
	}

	for s.end-s.begin < n {
		got, err := r.Read(s.buf[s.end : s.end+toget])
		s.end += got
		if err != nil {
			return nil, err
		}
	}

	return s.buf[s.begin : s.begin+n], nil
}

// Verify returns nil or an error describing the mismatch between the block
// list and actual reader contents
func Verify(r io.Reader, blocksize int, blocks []protocol.BlockInfo) error {
	hf := sha256.New()
	for i, block := range blocks {
		lr := &io.LimitedReader{R: r, N: int64(blocksize)}
		_, err := io.Copy(hf, lr)
		if err != nil {
			return err
		}

		hash := hf.Sum(nil)
		hf.Reset()

		if !bytes.Equal(hash, block.Hash) {
			return fmt.Errorf("hash mismatch %x != %x for block %d", hash, block.Hash, i)
		}
	}

	// We should have reached the end  now
	bs := make([]byte, 1)
	n, err := r.Read(bs)
	if n != 0 || err != io.EOF {
		return fmt.Errorf("file continues past end of blocks")
	}

	return nil
}

// ReadFrom reads data from r until error or io.EOF and appends it to the buffer.
// The amount of bytes read is returned plus any error except io.EOF.
func (b *Buffer) ReadFrom(r io.Reader) (int64, error) {
	err := b.err
	if err != nil && err != ErrNoMoreBytes {
		return 0, b.ioErr()
	}
	if b.fixed {
		return 0, ErrOperationNotAllowed
	}

	var buf [4096]byte
	var total int64
	for {
		n, err := r.Read(buf[:])
		if err != nil {
			if err == io.EOF {
				break
			}
			return total, err
		}
		_, err = b.Write(buf[:n])
		if err != nil {
			return total, err
		}
		total += int64(n)
	}

	return total, nil
}

// ReadFrom reads data from r until EOF and appends it to the buffer, growing
// the buffer as needed. The return value n is the number of bytes read. Any
// error except io.EOF encountered during the read is also returned. If the
// buffer becomes too large, ReadFrom will panic with ErrTooLarge.
func (b *Buffer) ReadFrom(r io.Reader) (n int64, err error) {
	b.lastRead = opInvalid
	// If buffer is empty, reset to recover space.
	if b.off >= len(b.buf) {
		b.Truncate(0)
	}
	for {
		if free := cap(b.buf) - len(b.buf); free < MinRead {
			// not enough space at end
			newBuf := b.buf
			if b.off+free < MinRead {
				// not enough space using beginning of buffer;
				// double buffer capacity
				newBuf = makeSlice(2*cap(b.buf) + MinRead)
			}
			copy(newBuf, b.buf[b.off:])
			b.buf = newBuf[:len(b.buf)-b.off]
			b.off = 0
		}
		m, e := r.Read(b.buf[len(b.buf):cap(b.buf)])
		b.buf = b.buf[0 : len(b.buf)+m]
		n += int64(m)
		if e == io.EOF {
			break
		}
		if e != nil {
			return n, e
		}
	}
	return n, nil // err is EOF, so return nil explicitly
}

func compareReaderWithBuf(rdr io.Reader, expect []byte, hash string) error {
	bufLen := 1 << 20
	if bufLen > len(expect) && len(expect) > 0 {
		// No need for bufLen to be longer than
		// expect, except that len(buf)==0 would
		// prevent us from handling empty readers the
		// same way as non-empty readers: reading 0
		// bytes at a time never reaches EOF.
		bufLen = len(expect)
	}
	buf := make([]byte, bufLen)
	cmp := expect

	// Loop invariants: all data read so far matched what
	// we expected, and the first N bytes of cmp are
	// expected to equal the next N bytes read from
	// rdr.
	for {
		n, err := rdr.Read(buf)
		if n > len(cmp) || bytes.Compare(cmp[:n], buf[:n]) != 0 {
			return collisionOrCorrupt(hash, expect[:len(expect)-len(cmp)], buf[:n], rdr)
		}
		cmp = cmp[n:]
		if err == io.EOF {
			if len(cmp) != 0 {
				return collisionOrCorrupt(hash, expect[:len(expect)-len(cmp)], nil, nil)
			}
			return nil
		} else if err != nil {
			return err
		}
	}
}

// Compute the MD5 digest of a data block (consisting of buf1 + buf2 +
// all bytes readable from rdr). If all data is read successfully,
// return DiskHashError or CollisionError depending on whether it
// matches expectMD5. If an error occurs while reading, return that
// error.
//
// "content has expected MD5" is called a collision because this
// function is used in cases where we have another block in hand with
// the given MD5 but different content.
func collisionOrCorrupt(expectMD5 string, buf1, buf2 []byte, rdr io.Reader) error {
	outcome := make(chan error)
	data := make(chan []byte, 1)
	go func() {
		h := md5.New()
		for b := range data {
			h.Write(b)
		}
		if fmt.Sprintf("%x", h.Sum(nil)) == expectMD5 {
			outcome <- CollisionError
		} else {
			outcome <- DiskHashError
		}
	}()
	data <- buf1
	if buf2 != nil {
		data <- buf2
	}
	var err error
	for rdr != nil && err == nil {
		buf := make([]byte, 1<<18)
		var n int
		n, err = rdr.Read(buf)
		data <- buf[:n]
	}
	close(data)
	if rdr != nil && err != io.EOF {
		<-outcome
		return err
	}
	return <-outcome
}

func DecodeUInt29(r io.Reader) (uint32, error) {
	var n uint32 = 0
	i := 0
	b := make([]byte, 1)
	for {
		_, err := r.Read(b)
		if err != nil {
			return 0, err
		}
		if i != 3 {
			n |= uint32(b[0] & 0x7F)
			if b[0]&0x80 != 0 {
				if i != 2 {
					n <<= 7
				} else {
					n <<= 8
				}
			} else {
				break
			}
		} else {
			n |= uint32(b[0])
			break
		}
		i++
	}
	return n, nil
}

// Like `io.Copy` except it only ever does one allocation of the 32K buffer.
func (tsd *Digest) copyWithBuf(dst io.Writer, src io.Reader) (written int64, err error) {
	if tsd.copyBuf == nil {
		tsd.copyBuf = make([]byte, 32*1024)
	}

	for {
		nr, er := src.Read(tsd.copyBuf)
		if nr > 0 {
			nw, ew := dst.Write(tsd.copyBuf[0:nr])
			if nw > 0 {
				written += int64(nw)
			}
			if ew != nil {
				err = ew
				break
			}
			if nr != nw {
				err = io.ErrShortWrite
				break
			}
		}
		if er == io.EOF {
			break
		}
		if er != nil {
			err = er
			break
		}
	}
	return
}

func copyWithExit(w io.Writer, r io.Reader, ch chan int) {
	buf := make([]byte, 1024)
	isTerminalRaw := false

	for {
		n, err := r.Read(buf)

		if err == io.EOF {
			ch <- 1
			return
		}

		if err != nil {
			break
		}

		if !isTerminalRaw {
			terminal.MakeRaw(int(os.Stdin.Fd()))
			isTerminalRaw = true
		}

		if s := string(buf[0:n]); strings.HasPrefix(s, StatusCodePrefix) {
			code, _ := strconv.Atoi(strings.TrimSpace(s[37:]))
			ch <- code
			return
		}

		_, err = w.Write(buf[0:n])

		if err != nil {
			break
		}
	}
}

// readTrace does wire-format parsing and verification.
// It does not care about specific event types and argument meaning.
func readTrace(r io.Reader) ([]rawEvent, error) {
	// Read and validate trace header.
	var buf [16]byte
	off, err := r.Read(buf[:])
	if off != 16 || err != nil {
		return nil, fmt.Errorf("failed to read header: read %v, err %v", off, err)
	}
	if bytes.Compare(buf[:], []byte("go 1.5 trace\x00\x00\x00\x00")) != 0 {
		return nil, fmt.Errorf("not a trace file")
	}

	// Read events.
	var events []rawEvent
	for {
		// Read event type and number of arguments (1 byte).
		off0 := off
		n, err := r.Read(buf[:1])
		if err == io.EOF {
			break
		}
		if err != nil || n != 1 {
			return nil, fmt.Errorf("failed to read trace at offset 0x%x: n=%v err=%v", off0, n, err)
		}
		off += n
		typ := buf[0] << 2 >> 2
		narg := buf[0] >> 6
		ev := rawEvent{typ: typ, off: off0}
		if narg < 3 {
			for i := 0; i < int(narg)+2; i++ { // sequence number and time stamp are present but not counted in narg
				var v uint64
				v, off, err = readVal(r, off)
				if err != nil {
					return nil, err
				}
				ev.args = append(ev.args, v)
			}
		} else {
			// If narg == 3, the first value is length of the event in bytes.
			var v uint64
			v, off, err = readVal(r, off)
			if err != nil {
				return nil, err
			}
			evLen := v
			off1 := off
			for evLen > uint64(off-off1) {
				v, off, err = readVal(r, off)
				if err != nil {
					return nil, err
				}
				ev.args = append(ev.args, v)
			}
			if evLen != uint64(off-off1) {
				return nil, fmt.Errorf("event has wrong length at offset 0x%x: want %v, got %v", off0, evLen, off-off1)
			}
		}
		events = append(events, ev)
	}
	return events, nil
}