// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package rpc
import (
"context"
"errors"
"fmt"
"reflect"
"runtime"
"strings"
"sync"
"unicode"
"unicode/utf8"
"github.com/ethereum/go-ethereum/log"
)
var (
contextType = reflect.TypeOf((*context.Context)(nil)).Elem()
errorType = reflect.TypeOf((*error)(nil)).Elem()
subscriptionType = reflect.TypeOf(Subscription{})
stringType = reflect.TypeOf("")
)
type serviceRegistry struct {
mu sync.Mutex
services map[string]service
}
// service represents a registered object.
type service struct {
name string // name for service
callbacks map[string]*callback // registered handlers
subscriptions map[string]*callback // available subscriptions/notifications
}
// callback is a method callback which was registered in the server
type callback struct {
fn reflect.Value // the function
rcvr reflect.Value // receiver object of method, set if fn is method
argTypes []reflect.Type // input argument types
hasCtx bool // method's first argument is a context (not included in argTypes)
errPos int // err return idx, of -1 when method cannot return error
isSubscribe bool // true if this is a subscription callback
}
func (r *serviceRegistry) registerName(name string, rcvr interface{}) error {
rcvrVal := reflect.ValueOf(rcvr)
if name == "" {
return fmt.Errorf("no service name for type %s", rcvrVal.Type().String())
}
callbacks := suitableCallbacks(rcvrVal)
if len(callbacks) == 0 {
return fmt.Errorf("service %T doesn't have any suitable methods/subscriptions to expose", rcvr)
}
r.mu.Lock()
defer r.mu.Unlock()
if r.services == nil {
r.services = make(map[string]service)
}
svc, ok := r.services[name]
if !ok {
svc = service{
name: name,
callbacks: make(map[string]*callback),
subscriptions: make(map[string]*callback),
}
r.services[name] = svc
}
for name, cb := range callbacks {
if cb.isSubscribe {
svc.subscriptions[name] = cb
} else {
svc.callbacks[name] = cb
}
}
return nil
}
// callback returns the callback corresponding to the given RPC method name.
func (r *serviceRegistry) callback(method string) *callback {
elem := strings.SplitN(method, serviceMethodSeparator, 2)
if len(elem) != 2 {
return nil
}
r.mu.Lock()
defer r.mu.Unlock()
return r.services[elem[0]].callbacks[elem[1]]
}
// subscription returns a subscription callback in the given service.
func (r *serviceRegistry) subscription(service, name string) *callback {
r.mu.Lock()
defer r.mu.Unlock()
return r.services[service].subscriptions[name]
}
// suitableCallbacks iterates over the methods of the given type. It determines if a method
// satisfies the criteria for a RPC callback or a subscription callback and adds it to the
// collection of callbacks. See server documentation for a summary of these criteria.
func suitableCallbacks(receiver reflect.Value) map[string]*callback {
typ := receiver.Type()
callbacks := make(map[string]*callback)
for m := 0; m < typ.NumMethod(); m++ {
method := typ.Method(m)
if method.PkgPath != "" {
continue // method not exported
}
cb := newCallback(receiver, method.Func)
if cb == nil {
continue // function invalid
}
name := formatName(method.Name)
callbacks[name] = cb
}
return callbacks
}
// newCallback turns fn (a function) into a callback object. It returns nil if the function
// is unsuitable as an RPC callback.
func newCallback(receiver, fn reflect.Value) *callback {
fntype := fn.Type()
c := &callback{fn: fn, rcvr: receiver, errPos: -1, isSubscribe: isPubSub(fntype)}
// Determine parameter types. They must all be exported or builtin types.
c.makeArgTypes()
if !allExportedOrBuiltin(c.argTypes) {
return nil
}
// Verify return types. The function must return at most one error
// and/or one other non-error value.
outs := make([]reflect.Type, fntype.NumOut())
for i := 0; i < fntype.NumOut(); i++ {
outs[i] = fntype.Out(i)
}
if len(outs) > 2 || !allExportedOrBuiltin(outs) {
return nil
}
// If an error is returned, it must be the last returned value.
switch {
case len(outs) == 1 && isErrorType(outs[0]):
c.errPos = 0
case len(outs) == 2:
if isErrorType(outs[0]) || !isErrorType(outs[1]) {
return nil
}
c.errPos = 1
}
return c
}
// makeArgTypes composes the argTypes list.
func (c *callback) makeArgTypes() {
fntype := c.fn.Type()
// Skip receiver and context.Context parameter (if present).
firstArg := 0
if c.rcvr.IsValid() {
firstArg++
}
if fntype.NumIn() > firstArg && fntype.In(firstArg) == contextType {
c.hasCtx = true
firstArg++
}
// Add all remaining parameters.
c.argTypes = make([]reflect.Type, fntype.NumIn()-firstArg)
for i := firstArg; i < fntype.NumIn(); i++ {
c.argTypes[i-firstArg] = fntype.In(i)
}
}
// call invokes the callback.
func (c *callback) call(ctx context.Context, method string, args []reflect.Value) (res interface{}, errRes error) {
// Create the argument slice.
fullargs := make([]reflect.Value, 0, 2+len(args))
if c.rcvr.IsValid() {
fullargs = append(fullargs, c.rcvr)
}
if c.hasCtx {
fullargs = append(fullargs, reflect.ValueOf(ctx))
}
fullargs = append(fullargs, args...)
// Catch panic while running the callback.
defer func() {
if err := recover(); err != nil {
const size = 64 << 10
buf := make([]byte, size)
buf = buf[:runtime.Stack(buf, false)]
log.Error("RPC method " + method + " crashed: " + fmt.Sprintf("%v\n%s", err, buf))
errRes = errors.New("method handler crashed")
}
}()
// Run the callback.
results := c.fn.Call(fullargs)
if len(results) == 0 {
return nil, nil
}
if c.errPos >= 0 && !results[c.errPos].IsNil() {
// Method has returned non-nil error value.
err := results[c.errPos].Interface().(error)
return reflect.Value{}, err
}
return results[0].Interface(), nil
}
// Is this an exported - upper case - name?
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(rune)
}
// Are all those types exported or built-in?
func allExportedOrBuiltin(types []reflect.Type) bool {
for _, typ := range types {
for typ.Kind() == reflect.Ptr {
typ = typ.Elem()
}
// PkgPath will be non-empty even for an exported type,
// so we need to check the type name as well.
if !isExported(typ.Name()) && typ.PkgPath() != "" {
return false
}
}
return true
}
// Is t context.Context or *context.Context?
func isContextType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
return t == contextType
}
// Does t satisfy the error interface?
func isErrorType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
return t.Implements(errorType)
}
// Is t Subscription or *Subscription?
func isSubscriptionType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
return t == subscriptionType
}
// isPubSub tests whether the given method has as as first argument a context.Context and
// returns the pair (Subscription, error).
func isPubSub(methodType reflect.Type) bool {
// numIn(0) is the receiver type
if methodType.NumIn() < 2 || methodType.NumOut() != 2 {
return false
}
return isContextType(methodType.In(1)) &&
isSubscriptionType(methodType.Out(0)) &&
isErrorType(methodType.Out(1))
}
// formatName converts to first character of name to lowercase.
func formatName(name string) string {
ret := []rune(name)
if len(ret) > 0 {
ret[0] = unicode.ToLower(ret[0])
}
return string(ret)
}
