You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: decoder.go
    path of file: ./repos/etcd/server/storage/wal
    
    the code of the file until where you have to start completion: // Copyright 2015 The etcd Authors
//
// Licensed under the Apache Licen
    
func decodeFrameSize(lenField int64) (recBytes int64, padBytes int64) {
	// the record size is stored in the lower 56 bits of the 64-bit length
	recBytes = int64(uint64(lenField) & ^(uint64(0xff) << 56))
	// non-zero padding is indicated by set MSb / a negative length
	if lenField < 0 {
		// padding is stored in lower 3 bits of length MSB
		padBytes = int64((uint64(lenField) >> 56) & 0x7)
	}
	return recBytes, padBytes
}