IOBuf是否能支持连续的内存避免内存拷贝

brpc目前从socket读取到的数据是放在IOBuf中的，但是由于IOBuf是一个非连续的内存缓冲区，如果用户需要保证接收到的是一块连续的内存的话需要进行一次内存拷贝，但是在大数据量的场景下内存拷贝存在性能瓶颈，请问有什么方法可以避免这次内存拷贝呢

Start by examining brpc's IOBuf implementation and the socket receive path described in the issue. Determine whether the proposed capability requires a new buffer or API design, then define how contiguous data would be provided without the current copy. Done should include an agreed approach and validation for large payload performance.

Written by the indexing model from the issue text.