status-go/vendor/github.com/anacrolix/torrent/bencode/encode.go

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2022-03-10 09:44:48 +00:00
package bencode
import (
"io"
"math/big"
"reflect"
"runtime"
"sort"
"strconv"
"sync"
"github.com/anacrolix/missinggo"
)
func isEmptyValue(v reflect.Value) bool {
return missinggo.IsEmptyValue(v)
}
type Encoder struct {
w io.Writer
scratch [64]byte
}
func (e *Encoder) Encode(v interface{}) (err error) {
if v == nil {
return
}
defer func() {
if e := recover(); e != nil {
if _, ok := e.(runtime.Error); ok {
panic(e)
}
var ok bool
err, ok = e.(error)
if !ok {
panic(e)
}
}
}()
e.reflectValue(reflect.ValueOf(v))
return nil
}
type stringValues []reflect.Value
func (sv stringValues) Len() int { return len(sv) }
func (sv stringValues) Swap(i, j int) { sv[i], sv[j] = sv[j], sv[i] }
func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
func (sv stringValues) get(i int) string { return sv[i].String() }
func (e *Encoder) write(s []byte) {
_, err := e.w.Write(s)
if err != nil {
panic(err)
}
}
func (e *Encoder) writeString(s string) {
for s != "" {
n := copy(e.scratch[:], s)
s = s[n:]
e.write(e.scratch[:n])
}
}
func (e *Encoder) reflectString(s string) {
e.writeStringPrefix(int64(len(s)))
e.writeString(s)
}
func (e *Encoder) writeStringPrefix(l int64) {
b := strconv.AppendInt(e.scratch[:0], l, 10)
e.write(b)
e.writeString(":")
}
func (e *Encoder) reflectByteSlice(s []byte) {
e.writeStringPrefix(int64(len(s)))
e.write(s)
}
// Returns true if the value implements Marshaler interface and marshaling was
// done successfully.
func (e *Encoder) reflectMarshaler(v reflect.Value) bool {
if !v.Type().Implements(marshalerType) {
if v.Kind() != reflect.Ptr && v.CanAddr() && v.Addr().Type().Implements(marshalerType) {
v = v.Addr()
} else {
return false
}
}
m := v.Interface().(Marshaler)
data, err := m.MarshalBencode()
if err != nil {
panic(&MarshalerError{v.Type(), err})
}
e.write(data)
return true
}
var bigIntType = reflect.TypeOf((*big.Int)(nil)).Elem()
func (e *Encoder) reflectValue(v reflect.Value) {
if e.reflectMarshaler(v) {
return
}
if v.Type() == bigIntType {
e.writeString("i")
bi := v.Interface().(big.Int)
e.writeString(bi.String())
e.writeString("e")
return
}
switch v.Kind() {
case reflect.Bool:
if v.Bool() {
e.writeString("i1e")
} else {
e.writeString("i0e")
}
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
e.writeString("i")
b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
e.write(b)
e.writeString("e")
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
e.writeString("i")
b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
e.write(b)
e.writeString("e")
case reflect.String:
e.reflectString(v.String())
case reflect.Struct:
e.writeString("d")
for _, ef := range getEncodeFields(v.Type()) {
fieldValue := ef.i(v)
if !fieldValue.IsValid() {
continue
}
if ef.omitEmpty && isEmptyValue(fieldValue) {
continue
}
e.reflectString(ef.tag)
e.reflectValue(fieldValue)
}
e.writeString("e")
case reflect.Map:
if v.Type().Key().Kind() != reflect.String {
panic(&MarshalTypeError{v.Type()})
}
if v.IsNil() {
e.writeString("de")
break
}
e.writeString("d")
sv := stringValues(v.MapKeys())
sort.Sort(sv)
for _, key := range sv {
e.reflectString(key.String())
e.reflectValue(v.MapIndex(key))
}
e.writeString("e")
case reflect.Slice, reflect.Array:
e.reflectSequence(v)
case reflect.Interface:
e.reflectValue(v.Elem())
case reflect.Ptr:
if v.IsNil() {
v = reflect.Zero(v.Type().Elem())
} else {
v = v.Elem()
}
e.reflectValue(v)
default:
panic(&MarshalTypeError{v.Type()})
}
}
func (e *Encoder) reflectSequence(v reflect.Value) {
// Use bencode string-type
if v.Type().Elem().Kind() == reflect.Uint8 {
if v.Kind() != reflect.Slice {
// Can't use []byte optimization
if !v.CanAddr() {
e.writeStringPrefix(int64(v.Len()))
for i := 0; i < v.Len(); i++ {
var b [1]byte
b[0] = byte(v.Index(i).Uint())
e.write(b[:])
}
return
}
v = v.Slice(0, v.Len())
}
s := v.Bytes()
e.reflectByteSlice(s)
return
}
if v.IsNil() {
e.writeString("le")
return
}
e.writeString("l")
for i, n := 0, v.Len(); i < n; i++ {
e.reflectValue(v.Index(i))
}
e.writeString("e")
}
type encodeField struct {
i func(v reflect.Value) reflect.Value
tag string
omitEmpty bool
}
type encodeFieldsSortType []encodeField
func (ef encodeFieldsSortType) Len() int { return len(ef) }
func (ef encodeFieldsSortType) Swap(i, j int) { ef[i], ef[j] = ef[j], ef[i] }
func (ef encodeFieldsSortType) Less(i, j int) bool { return ef[i].tag < ef[j].tag }
var (
typeCacheLock sync.RWMutex
encodeFieldsCache = make(map[reflect.Type][]encodeField)
)
func getEncodeFields(t reflect.Type) []encodeField {
typeCacheLock.RLock()
fs, ok := encodeFieldsCache[t]
typeCacheLock.RUnlock()
if ok {
return fs
}
fs = makeEncodeFields(t)
typeCacheLock.Lock()
defer typeCacheLock.Unlock()
encodeFieldsCache[t] = fs
return fs
}
func makeEncodeFields(t reflect.Type) (fs []encodeField) {
for _i, n := 0, t.NumField(); _i < n; _i++ {
i := _i
f := t.Field(i)
if f.PkgPath != "" {
continue
}
if f.Anonymous {
t := f.Type
if t.Kind() == reflect.Ptr {
t = t.Elem()
}
anonEFs := makeEncodeFields(t)
for aefi := range anonEFs {
anonEF := anonEFs[aefi]
bottomField := anonEF
bottomField.i = func(v reflect.Value) reflect.Value {
v = v.Field(i)
if v.Kind() == reflect.Ptr {
if v.IsNil() {
// This will skip serializing this value.
return reflect.Value{}
}
v = v.Elem()
}
return anonEF.i(v)
}
fs = append(fs, bottomField)
}
continue
}
var ef encodeField
ef.i = func(v reflect.Value) reflect.Value {
return v.Field(i)
}
ef.tag = f.Name
tv := getTag(f.Tag)
if tv.Ignore() {
continue
}
if tv.Key() != "" {
ef.tag = tv.Key()
}
ef.omitEmpty = tv.OmitEmpty()
fs = append(fs, ef)
}
fss := encodeFieldsSortType(fs)
sort.Sort(fss)
return fs
}