go内存缓存BigCache之Entry封装源码阅读

const (
    timestampSizeInBytes = 8                                                       // Number of bytes used for timestamp
    hashSizeInBytes      = 8                                                       // Number of bytes used for hash
    keySizeInBytes       = 2                                                       // Number of bytes used for size of entry key
    headersSizeInBytes   = timestampSizeInBytes + hashSizeInBytes + keySizeInBytes // Number of bytes used for all headers
)
func wrapEntry(timestamp uint64, hash uint64, key string, entry []byte, buffer *[]byte) []byte {
    keyLength := len(key)
    blobLength := len(entry) + headersSizeInBytes + keyLength
    if blobLength > len(*buffer) {
        *buffer = make([]byte, blobLength)
    }
    blob := *buffer
    binary.LittleEndian.PutUint64(blob, timestamp)
    binary.LittleEndian.PutUint64(blob[timestampSizeInBytes:], hash)
    binary.LittleEndian.PutUint16(blob[timestampSizeInBytes+hashSizeInBytes:], uint16(keyLength))
    copy(blob[headersSizeInBytes:], key)
    copy(blob[headersSizeInBytes+keyLength:], entry)
    return blob[:blobLength]
}