aboutsummaryrefslogtreecommitdiff
path: root/rpc/service.go
diff options
context:
space:
mode:
Diffstat (limited to 'rpc/service.go')
-rw-r--r--rpc/service.go285
1 files changed, 285 insertions, 0 deletions
diff --git a/rpc/service.go b/rpc/service.go
new file mode 100644
index 0000000..ead6fb6
--- /dev/null
+++ b/rpc/service.go
@@ -0,0 +1,285 @@
+// Copyright 2019 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/ava-labs/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)
+}