class Server

Request new IO buffer size. Can fail if out of memory. Discards

contents of existing buffer on success. Leaves existing buffer

intact on failure.

Set event used to signal device state. Discards existing event

after having transferred device state to the new event.

Acquire VMO for IO buffer. Can be called multiple times. Each call

returns a new handle to the VMO.

Attempt to read up to count bytes into IO buffer at specified offset.

Returns `ZX_ERR_SHOULD_WAIT` if pipe device is not readable.

Writes up to count bytes from the IO buffer at specified offset.

Returns `ZX_ERR_SHOULD_WAIT` if pipe device is not writable.

Writes `count` bytes from the IO buffer at specified write

`offset`. Returns `ZX_ERR_SHOULD_WAIT` if pipe device is not writable.

If it writes to device successfully, it subsequently reads `read_count`

bytes into the IO buffer at specified `read_offset`. Returns

`ZX_ERR_SHOULD_WAIT` if pipe device is not readable.

Return value `actual` is the total bytes read from and written to

the IO buffer.

The name "DoCall" (instead of "Call") is to avoid collision with LLCPP

generated code "class Call" (generated per protocol). We don't want

this method attempting to compile as if it were a constructor.

|bind_handler| returns a handler that binds incoming connections to this

server implementation.

The returned handler borrows the server instance.

The server must outlive the provided |dispatcher|. Only after

the dispatcher is shutdown will it be safe to destroy the servers.

The server should not be moved.