284 lines
7.1 KiB
Go
284 lines
7.1 KiB
Go
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// Copyright 2014 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package rlp
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import (
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"fmt"
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"reflect"
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"strings"
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"sync"
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"sync/atomic"
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)
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// typeinfo is an entry in the type cache.
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type typeinfo struct {
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decoder decoder
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decoderErr error // error from makeDecoder
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writer writer
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writerErr error // error from makeWriter
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}
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// tags represents struct tags.
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type tags struct {
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// rlp:"nil" controls whether empty input results in a nil pointer.
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// nilKind is the kind of empty value allowed for the field.
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nilKind Kind
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nilOK bool
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// rlp:"optional" allows for a field to be missing in the input list.
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// If this is set, all subsequent fields must also be optional.
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optional bool
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// rlp:"tail" controls whether this field swallows additional list elements. It can
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// only be set for the last field, which must be of slice type.
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tail bool
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// rlp:"-" ignores fields.
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ignored bool
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}
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// typekey is the key of a type in typeCache. It includes the struct tags because
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// they might generate a different decoder.
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type typekey struct {
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reflect.Type
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tags
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}
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type decoder func(*Stream, reflect.Value) error
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type writer func(reflect.Value, *encbuf) error
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var theTC = newTypeCache()
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type typeCache struct {
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cur atomic.Value
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// This lock synchronizes writers.
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mu sync.Mutex
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next map[typekey]*typeinfo
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}
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func newTypeCache() *typeCache {
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c := new(typeCache)
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c.cur.Store(make(map[typekey]*typeinfo))
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return c
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}
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func cachedDecoder(typ reflect.Type) (decoder, error) {
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info := theTC.info(typ)
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return info.decoder, info.decoderErr
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}
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func cachedWriter(typ reflect.Type) (writer, error) {
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info := theTC.info(typ)
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return info.writer, info.writerErr
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}
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func (c *typeCache) info(typ reflect.Type) *typeinfo {
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key := typekey{Type: typ}
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if info := c.cur.Load().(map[typekey]*typeinfo)[key]; info != nil {
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return info
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}
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// Not in the cache, need to generate info for this type.
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return c.generate(typ, tags{})
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}
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func (c *typeCache) generate(typ reflect.Type, tags tags) *typeinfo {
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c.mu.Lock()
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defer c.mu.Unlock()
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cur := c.cur.Load().(map[typekey]*typeinfo)
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if info := cur[typekey{typ, tags}]; info != nil {
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return info
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}
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// Copy cur to next.
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c.next = make(map[typekey]*typeinfo, len(cur)+1)
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for k, v := range cur {
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c.next[k] = v
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}
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// Generate.
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info := c.infoWhileGenerating(typ, tags)
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// next -> cur
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c.cur.Store(c.next)
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c.next = nil
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return info
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}
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func (c *typeCache) infoWhileGenerating(typ reflect.Type, tags tags) *typeinfo {
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key := typekey{typ, tags}
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if info := c.next[key]; info != nil {
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return info
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}
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// Put a dummy value into the cache before generating.
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// If the generator tries to lookup itself, it will get
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// the dummy value and won't call itself recursively.
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info := new(typeinfo)
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c.next[key] = info
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info.generate(typ, tags)
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return info
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}
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type field struct {
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index int
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info *typeinfo
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optional bool
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}
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// structFields resolves the typeinfo of all public fields in a struct type.
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func structFields(typ reflect.Type) (fields []field, err error) {
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var (
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lastPublic = lastPublicField(typ)
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anyOptional = false
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)
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for i := 0; i < typ.NumField(); i++ {
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if f := typ.Field(i); f.PkgPath == "" { // exported
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tags, err := parseStructTag(typ, i, lastPublic)
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if err != nil {
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return nil, err
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}
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// Skip rlp:"-" fields.
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if tags.ignored {
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continue
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}
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// If any field has the "optional" tag, subsequent fields must also have it.
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if tags.optional || tags.tail {
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anyOptional = true
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} else if anyOptional {
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return nil, fmt.Errorf(`rlp: struct field %v.%s needs "optional" tag`, typ, f.Name)
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}
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info := theTC.infoWhileGenerating(f.Type, tags)
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fields = append(fields, field{i, info, tags.optional})
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}
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}
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return fields, nil
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}
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// anyOptionalFields returns the index of the first field with "optional" tag.
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func firstOptionalField(fields []field) int {
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for i, f := range fields {
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if f.optional {
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return i
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}
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}
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return len(fields)
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}
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type structFieldError struct {
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typ reflect.Type
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field int
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err error
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}
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func (e structFieldError) Error() string {
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return fmt.Sprintf("%v (struct field %v.%s)", e.err, e.typ, e.typ.Field(e.field).Name)
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}
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type structTagError struct {
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typ reflect.Type
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field, tag, err string
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}
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func (e structTagError) Error() string {
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return fmt.Sprintf("rlp: invalid struct tag %q for %v.%s (%s)", e.tag, e.typ, e.field, e.err)
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}
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func parseStructTag(typ reflect.Type, fi, lastPublic int) (tags, error) {
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f := typ.Field(fi)
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var ts tags
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for _, t := range strings.Split(f.Tag.Get("rlp"), ",") {
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switch t = strings.TrimSpace(t); t {
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case "":
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case "-":
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ts.ignored = true
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case "nil", "nilString", "nilList":
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ts.nilOK = true
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if f.Type.Kind() != reflect.Ptr {
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return ts, structTagError{typ, f.Name, t, "field is not a pointer"}
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}
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switch t {
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case "nil":
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ts.nilKind = defaultNilKind(f.Type.Elem())
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case "nilString":
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ts.nilKind = String
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case "nilList":
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ts.nilKind = List
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}
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case "optional":
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ts.optional = true
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if ts.tail {
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return ts, structTagError{typ, f.Name, t, `also has "tail" tag`}
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}
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case "tail":
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ts.tail = true
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if fi != lastPublic {
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return ts, structTagError{typ, f.Name, t, "must be on last field"}
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}
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if ts.optional {
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return ts, structTagError{typ, f.Name, t, `also has "optional" tag`}
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}
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if f.Type.Kind() != reflect.Slice {
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return ts, structTagError{typ, f.Name, t, "field type is not slice"}
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}
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default:
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return ts, fmt.Errorf("rlp: unknown struct tag %q on %v.%s", t, typ, f.Name)
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}
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}
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return ts, nil
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}
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func lastPublicField(typ reflect.Type) int {
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last := 0
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for i := 0; i < typ.NumField(); i++ {
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if typ.Field(i).PkgPath == "" {
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last = i
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}
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}
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return last
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}
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func (i *typeinfo) generate(typ reflect.Type, tags tags) {
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i.decoder, i.decoderErr = makeDecoder(typ, tags)
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i.writer, i.writerErr = makeWriter(typ, tags)
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}
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// defaultNilKind determines whether a nil pointer to typ encodes/decodes
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// as an empty string or empty list.
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func defaultNilKind(typ reflect.Type) Kind {
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k := typ.Kind()
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if isUint(k) || k == reflect.String || k == reflect.Bool || isByteArray(typ) {
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return String
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}
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return List
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}
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func isUint(k reflect.Kind) bool {
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return k >= reflect.Uint && k <= reflect.Uintptr
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}
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func isByte(typ reflect.Type) bool {
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return typ.Kind() == reflect.Uint8 && !typ.Implements(encoderInterface)
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}
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func isByteArray(typ reflect.Type) bool {
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return (typ.Kind() == reflect.Slice || typ.Kind() == reflect.Array) && isByte(typ.Elem())
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}
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