// append appends a key/value pair, which may also be a restart point.
func (w *Writer) append(key, value []byte, restart bool) {
nShared := 0
if restart {
w.restarts = append(w.restarts, uint32(w.buf.Len()))
} else {
nShared = db.SharedPrefixLen(w.prevKey, key)
}
w.prevKey = append(w.prevKey[:0], key...)
w.nEntries++
n := binary.PutUvarint(w.tmp[0:], uint64(nShared))
n += binary.PutUvarint(w.tmp[n:], uint64(len(key)-nShared))
n += binary.PutUvarint(w.tmp[n:], uint64(len(value)))
w.buf.Write(w.tmp[:n])
w.buf.Write(key[nShared:])
w.buf.Write(value)
}
// append appends a key/value pair, which may also be a restart point.
func (w *Writer) append(key, value []byte, restart bool) {
nShared := 0
if restart {
// 记录重启点
w.restarts = append(w.restarts, uint32(w.buf.Len()))
} else {
// 当前key与前一个key可以共享存储的部分的长度
nShared = db.SharedPrefixLen(w.prevKey, key)
}
w.prevKey = append(w.prevKey[:0], key...)
w.nEntries++
// 先存入共享的部分的长度
n := binary.PutUvarint(w.tmp[0:], uint64(nShared))
// 然后记录共享部分之外当前key的剩余部分
n += binary.PutUvarint(w.tmp[n:], uint64(len(key)-nShared))
// 存入value的长度
n += binary.PutUvarint(w.tmp[n:], uint64(len(value)))
w.buf.Write(w.tmp[:n])
// 写入非共享部分的key值
w.buf.Write(key[nShared:])
// 写入value
w.buf.Write(value)
}