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reader.go
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reader.go
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// Copyright (c) 2016 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package frame
import (
"bytes"
"encoding/binary"
"io"
"sync"
"go.uber.org/atomic"
)
// Maximum frame size for which we pre-allocate buffers.
var _fastPathFrameSize int64 = 10 * 1024 * 1024 // 10 MB
// Reader is a reader for framed messages.
type Reader struct {
sync.Mutex
closed atomic.Bool
r io.Reader
buff [4]byte
}
// NewReader builds a new Reader which reads frames from the given io.Reader.
//
// If the io.Reader is a ReadCloser, its Close method will be called when the
// frame.Reader is closed.
func NewReader(r io.Reader) *Reader {
return &Reader{r: r}
}
// Read reads the next frame from the Reader.
func (r *Reader) Read() ([]byte, error) {
r.Lock()
defer r.Unlock()
if _, err := io.ReadFull(r.r, r.buff[:]); err != nil {
return nil, err
}
length := int64(binary.BigEndian.Uint32(r.buff[:]))
if length < _fastPathFrameSize {
return r.readFastPath(length)
}
var buff bytes.Buffer
_, err := io.CopyN(&buff, r.r, length)
if err != nil {
return nil, err
}
return buff.Bytes(), nil
}
func (r *Reader) readFastPath(l int64) ([]byte, error) {
buff := make([]byte, l)
if l == 0 {
return buff, nil
}
_, err := io.ReadFull(r.r, buff)
return buff, err
}
// Close closes the given Reader.
func (r *Reader) Close() error {
if r.closed.Swap(true) {
return nil // already closed
}
if c, ok := r.r.(io.Closer); ok {
return c.Close()
}
return nil
}