src/syscall/zx/zxsocket/server.go

// Copyright 2017 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build fuchsia

package zxsocket

import (
	"syscall/zx"
)

// ServerHandler is the type of the callback which contains the remoteio "server". It is called from
// the server handler function.
// - msg.Datalen represents the size of the incoming/outgoing message in msg.Data.
// - Return values are placed in msg.Arg. Negative is error.
type ServerHandler func(msg *Msg, rh zx.Socket, cookie int64) zx.Status

// Handler reads a single RIO message from the handle h. If the message is valid, the callback
// cb is invoked. If the callback is successful, a response may be sent back on handle h.
func Handler(h zx.Socket, cb interface{}, cookie int64) error {
	var msg Msg

	serverCb := cb.(ServerHandler)
	if h == 0 {
		// The remote side has been closed. Send our final callback and leave.
		msg.SetOp(OpClose)
		msg.Arg = 0
		msg.Datalen = 0
		msg.Hcount = 0
		serverCb(&msg, 0, cookie)
		return nil
	}
	msg.Hcount = MessageMaxHandles
	numBytesInt, _, err := msg.ReadMsg(h)
	numBytes := uint32(numBytesInt)
	if err != nil {
		if mxerr, hasStatus := err.(zx.Error); hasStatus && mxerr.Status == zx.ErrBadState {
			return ErrNoWork
		}
		return err
	}
	if !msg.IsValidIncoming(numBytes) {
		return zx.Error{Status: zx.ErrInvalidArgs, Text: "zxsocket.Handler"}
	}

	isClose := (msg.Op() == OpClose)
	status := serverCb(&msg, h, cookie)
	msg.Arg = int32(status)
	if zx.Status(msg.Arg) == ErrIndirect.Status {
		// The callback is handling the reply itself
		return nil
	} else if status < 0 || !msg.IsValid() {
		// zx.Error case
		msg.Datalen = 0
		if msg.Arg >= 0 {
			// TODO(smklein): This error code may change. It currently is set to "ERR_FAULT" in
			// Zircon, but is scheduled to change.
			msg.Arg = int32(zx.ErrIO)
		}
	}

	_, err = msg.WriteMsg(h)
	if isClose {
		// Signals that a close callback is not necessary -- the op has already completed
		return ErrDisconnectNoCallback
	}
	return err
}