Official Go implementation of the Ethereum protocol
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go-ethereum/rlp/typecache.go

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5.6 KiB

// Copyright 2014 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 rlp
import (
"fmt"
"reflect"
"strings"
"sync"
)
var (
typeCacheMutex sync.RWMutex
typeCache = make(map[typekey]*typeinfo)
)
type typeinfo struct {
decoder decoder
decoderErr error // error from makeDecoder
writer writer
writerErr error // error from makeWriter
}
// tags represents struct tags.
type tags struct {
// rlp:"nil" controls whether empty input results in a nil pointer.
nilOK bool
// This controls whether nil pointers are encoded/decoded as empty strings
// or empty lists.
nilKind Kind
// rlp:"tail" controls whether this field swallows additional list
// elements. It can only be set for the last field, which must be
// of slice type.
tail bool
// rlp:"-" ignores fields.
ignored bool
}
// typekey is the key of a type in typeCache. It includes the struct tags because
// they might generate a different decoder.
type typekey struct {
reflect.Type
tags
}
type decoder func(*Stream, reflect.Value) error
type writer func(reflect.Value, *encbuf) error
func cachedDecoder(typ reflect.Type) (decoder, error) {
info := cachedTypeInfo(typ, tags{})
return info.decoder, info.decoderErr
}
func cachedWriter(typ reflect.Type) (writer, error) {
info := cachedTypeInfo(typ, tags{})
return info.writer, info.writerErr
}
func cachedTypeInfo(typ reflect.Type, tags tags) *typeinfo {
typeCacheMutex.RLock()
info := typeCache[typekey{typ, tags}]
typeCacheMutex.RUnlock()
if info != nil {
return info
}
// not in the cache, need to generate info for this type.
typeCacheMutex.Lock()
defer typeCacheMutex.Unlock()
return cachedTypeInfo1(typ, tags)
}
func cachedTypeInfo1(typ reflect.Type, tags tags) *typeinfo {
key := typekey{typ, tags}
info := typeCache[key]
if info != nil {
// another goroutine got the write lock first
return info
}
// put a dummy value into the cache before generating.
// if the generator tries to lookup itself, it will get
// the dummy value and won't call itself recursively.
info = new(typeinfo)
typeCache[key] = info
info.generate(typ, tags)
return info
}
type field struct {
index int
info *typeinfo
}
func structFields(typ reflect.Type) (fields []field, err error) {
lastPublic := lastPublicField(typ)
for i := 0; i < typ.NumField(); i++ {
if f := typ.Field(i); f.PkgPath == "" { // exported
tags, err := parseStructTag(typ, i, lastPublic)
if err != nil {
return nil, err
}
if tags.ignored {
continue
}
info := cachedTypeInfo1(f.Type, tags)
fields = append(fields, field{i, info})
}
}
return fields, nil
}
type structFieldError struct {
typ reflect.Type
field int
err error
}
func (e structFieldError) Error() string {
return fmt.Sprintf("%v (struct field %v.%s)", e.err, e.typ, e.typ.Field(e.field).Name)
}
type structTagError struct {
typ reflect.Type
field, tag, err string
}
func (e structTagError) Error() string {
return fmt.Sprintf("rlp: invalid struct tag %q for %v.%s (%s)", e.tag, e.typ, e.field, e.err)
}
func parseStructTag(typ reflect.Type, fi, lastPublic int) (tags, error) {
f := typ.Field(fi)
var ts tags
for _, t := range strings.Split(f.Tag.Get("rlp"), ",") {
switch t = strings.TrimSpace(t); t {
case "":
case "-":
ts.ignored = true
case "nil", "nilString", "nilList":
ts.nilOK = true
if f.Type.Kind() != reflect.Ptr {
return ts, structTagError{typ, f.Name, t, "field is not a pointer"}
}
switch t {
case "nil":
ts.nilKind = defaultNilKind(f.Type.Elem())
case "nilString":
ts.nilKind = String
case "nilList":
ts.nilKind = List
}
case "tail":
ts.tail = true
if fi != lastPublic {
return ts, structTagError{typ, f.Name, t, "must be on last field"}
}
if f.Type.Kind() != reflect.Slice {
return ts, structTagError{typ, f.Name, t, "field type is not slice"}
}
default:
return ts, fmt.Errorf("rlp: unknown struct tag %q on %v.%s", t, typ, f.Name)
}
}
return ts, nil
}
func lastPublicField(typ reflect.Type) int {
last := 0
for i := 0; i < typ.NumField(); i++ {
if typ.Field(i).PkgPath == "" {
last = i
}
}
return last
}
func (i *typeinfo) generate(typ reflect.Type, tags tags) {
i.decoder, i.decoderErr = makeDecoder(typ, tags)
i.writer, i.writerErr = makeWriter(typ, tags)
}
// defaultNilKind determines whether a nil pointer to typ encodes/decodes
// as an empty string or empty list.
func defaultNilKind(typ reflect.Type) Kind {
k := typ.Kind()
if isUint(k) || k == reflect.String || k == reflect.Bool || isByteArray(typ) {
return String
}
return List
}
func isUint(k reflect.Kind) bool {
return k >= reflect.Uint && k <= reflect.Uintptr
}
func isByte(typ reflect.Type) bool {
return typ.Kind() == reflect.Uint8 && !typ.Implements(encoderInterface)
}
func isByteArray(typ reflect.Type) bool {
return (typ.Kind() == reflect.Slice || typ.Kind() == reflect.Array) && isByte(typ.Elem())
}