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// 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 (
"bufio"
"context"
crand "crypto/rand"
"encoding/binary"
"encoding/hex"
"math/rand"
"reflect"
"strings"
"sync"
"time"
"unicode"
"unicode/utf8"
)
var (
subscriptionIDGenMu sync.Mutex
subscriptionIDGen = idGenerator()
)
// Is this an exported - upper case - name?
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
return unicode.IsUpper(rune)
}
// Is this type exported or a builtin?
func isExportedOrBuiltinType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
// PkgPath will be non-empty even for an exported type,
// so we need to check the type name as well.
return isExported(t.Name()) || t.PkgPath() == ""
}
var contextType = reflect.TypeOf((*context.Context)(nil)).Elem()
// isContextType returns an indication if the given t is of context.Context or *context.Context type
func isContextType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
return t == contextType
}
var errorType = reflect.TypeOf((*error)(nil)).Elem()
// Implements this type the error interface
func isErrorType(t reflect.Type) bool {
for t.Kind() == reflect.Ptr {
t = t.Elem()
}
return t.Implements(errorType)
}
var subscriptionType = reflect.TypeOf((*Subscription)(nil)).Elem()
// isSubscriptionType returns an indication if the given t is of Subscription or *Subscription type
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 will convert to first character to lower case
func formatName(name string) string {
ret := []rune(name)
if len(ret) > 0 {
ret[0] = unicode.ToLower(ret[0])
}
return string(ret)
}
// suitableCallbacks iterates over the methods of the given type. It will determine if a method satisfies the criteria
// for a RPC callback or a subscription callback and adds it to the collection of callbacks or subscriptions. See server
// documentation for a summary of these criteria.
func suitableCallbacks(rcvr reflect.Value, typ reflect.Type) (callbacks, subscriptions) {
callbacks := make(callbacks)
subscriptions := make(subscriptions)
METHODS:
for m := 0; m < typ.NumMethod(); m++ {
method := typ.Method(m)
mtype := method.Type
mname := formatName(method.Name)
if method.PkgPath != "" { // method must be exported
continue
}
var h callback
h.isSubscribe = isPubSub(mtype)
h.rcvr = rcvr
h.method = method
h.errPos = -1
firstArg := 1
numIn := mtype.NumIn()
if numIn >= 2 && mtype.In(1) == contextType {
h.hasCtx = true
firstArg = 2
}
if h.isSubscribe {
h.argTypes = make([]reflect.Type, numIn-firstArg) // skip rcvr type
for i := firstArg; i < numIn; i++ {
argType := mtype.In(i)
if isExportedOrBuiltinType(argType) {
h.argTypes[i-firstArg] = argType
} else {
continue METHODS
}
}
subscriptions[mname] = &h
continue METHODS
}
// determine method arguments, ignore first arg since it's the receiver type
// Arguments must be exported or builtin types
h.argTypes = make([]reflect.Type, numIn-firstArg)
for i := firstArg; i < numIn; i++ {
argType := mtype.In(i)
if !isExportedOrBuiltinType(argType) {
continue METHODS
}
h.argTypes[i-firstArg] = argType
}
// check that all returned values are exported or builtin types
for i := 0; i < mtype.NumOut(); i++ {
if !isExportedOrBuiltinType(mtype.Out(i)) {
continue METHODS
}
}
// when a method returns an error it must be the last returned value
h.errPos = -1
for i := 0; i < mtype.NumOut(); i++ {
if isErrorType(mtype.Out(i)) {
h.errPos = i
break
}
}
if h.errPos >= 0 && h.errPos != mtype.NumOut()-1 {
continue METHODS
}
switch mtype.NumOut() {
case 0, 1, 2:
if mtype.NumOut() == 2 && h.errPos == -1 { // method must one return value and 1 error
continue METHODS
}
callbacks[mname] = &h
}
}
return callbacks, subscriptions
}
// idGenerator helper utility that generates a (pseudo) random sequence of
// bytes that are used to generate identifiers.
func idGenerator() *rand.Rand {
if seed, err := binary.ReadVarint(bufio.NewReader(crand.Reader)); err == nil {
return rand.New(rand.NewSource(seed))
}
return rand.New(rand.NewSource(int64(time.Now().Nanosecond())))
}
// NewID generates a identifier that can be used as an identifier in the RPC interface.
// e.g. filter and subscription identifier.
func NewID() ID {
subscriptionIDGenMu.Lock()
defer subscriptionIDGenMu.Unlock()
id := make([]byte, 16)
for i := 0; i < len(id); i += 7 {
val := subscriptionIDGen.Int63()
for j := 0; i+j < len(id) && j < 7; j++ {
id[i+j] = byte(val)
val >>= 8
}
}
rpcId := hex.EncodeToString(id)
// rpc ID's are RPC quantities, no leading zero's and 0 is 0x0
rpcId = strings.TrimLeft(rpcId, "0")
if rpcId == "" {
rpcId = "0"
}
return ID("0x" + rpcId)
}
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