Try to move-append item to the front without blocking.
If the container is not full (see {High-Water Mark Feature}), append the specified move-insertable item to the front of the container, otherwise leave the container unchanged. If the container is modified, item is left in a valid but unspecified state, otherwise item is unchanged. Return 0 if the container was updated and a non-zero value otherwise.
0 if the container was updated, and a non-zero value otherwise
| Name | Description |
|---|---|
| item | value to move-append |