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package encoding
import (
"fmt"
"io"
)
// ReadPrefix reads an 8-byte length prefixes, followed by the number of bytes
// specified in the prefix. The operation is aborted if the prefix exceeds a
// specified maximum length.
func ReadPrefix(r io.Reader, maxLen uint64) ([]byte, error) {
prefix := make([]byte, 8)
if _, err := io.ReadFull(r, prefix); err != nil {
return nil, err
}
dataLen := DecUint64(prefix)
if dataLen > maxLen {
return nil, fmt.Errorf("length %d exceeds maxLen of %d", dataLen, maxLen)
}
// read dataLen bytes
data := make([]byte, dataLen)
_, err := io.ReadFull(r, data)
return data, err
}
// ReadObject reads and decodes a length-prefixed and marshalled object.
func ReadObject(r io.Reader, obj interface{}, maxLen uint64) error {
data, err := ReadPrefix(r, maxLen)
if err != nil {
return err
}
return Unmarshal(data, obj)
}
// WritePrefix writes a length-prefixed byte slice to w.
func WritePrefix(w io.Writer, data []byte) error {
err := WriteInt(w, len(data))
if err != nil {
return err
}
n, err := w.Write(data)
if err == nil && n != len(data) {
err = io.ErrShortWrite
}
return err
}
// WriteObject writes a length-prefixed object to w.
func WriteObject(w io.Writer, v interface{}) error {
return WritePrefix(w, Marshal(v))
}
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