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67 lines
1.5 KiB
Go
67 lines
1.5 KiB
Go
// Package msgutil provides utility for JSON message with uint32le header
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package msgutil
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import (
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"bytes"
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"encoding/binary"
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"encoding/json"
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"io"
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"github.com/pkg/errors"
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)
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const (
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maxLength = 1 << 16
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)
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func MarshalToWriter(w io.Writer, x interface{}) (int, error) {
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b, err := json.Marshal(x)
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if err != nil {
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return 0, err
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}
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if len(b) > maxLength {
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return 0, errors.Errorf("bad message length: %d (max: %d)", len(b), maxLength)
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}
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h := make([]byte, 4)
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binary.LittleEndian.PutUint32(h, uint32(len(b)))
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return w.Write(append(h, b...))
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}
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func UnmarshalFromReader(r io.Reader, x interface{}) (int, error) {
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hdr := make([]byte, 4)
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n, err := r.Read(hdr)
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if err != nil {
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return n, err
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}
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if n != 4 {
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return n, errors.Errorf("read %d bytes, expected 4 bytes", n)
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}
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bLen := binary.LittleEndian.Uint32(hdr)
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if bLen > maxLength || bLen < 1 {
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return n, errors.Errorf("bad message length: %d (max: %d)", bLen, maxLength)
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}
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b := make([]byte, bLen)
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n, err = r.Read(b)
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if err != nil {
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return 4 + n, err
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}
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if n != int(bLen) {
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return 4 + n, errors.Errorf("read %d bytes, expected %d bytes", n, bLen)
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}
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return 4 + n, json.Unmarshal(b, x)
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}
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func Marshal(x interface{}) ([]byte, error) {
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var b bytes.Buffer
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_, err := MarshalToWriter(&b, x)
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return b.Bytes(), err
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}
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func Unmarshal(b []byte, x interface{}) error {
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n, err := UnmarshalFromReader(bytes.NewReader(b), x)
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if n != len(b) {
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return errors.Errorf("read %d bytes, expected %d bytes", n, len(b))
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}
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return err
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}
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