folly::IOBuf::isShared

Description

Return true if at least one of the IOBufs in this chain are shared, or false if all of the IOBufs point to unique buffers.

Use isSharedOne() to only check this IOBuf rather than the entire chain.

If isShared() returns false, then you are probably the sole owner of the IOBuf chain and can write to it without needing to call unshare(). This is not a guarantee, since it is possible for another thread to concurrently acquire shared ownership.