bencode/encode.go

   1 package bencode
   2
   3 import (
   4         "io"
   5         "math/big"
   6         "reflect"
   7         "runtime"
   8         "sort"
   9         "strconv"
  10         "sync"
  11
  12         "github.com/anacrolix/missinggo"
  13 )
  14
  15 func isEmptyValue(v reflect.Value) bool {
  16         return missinggo.IsEmptyValue(v)
  17 }
  18
  19 type Encoder struct {
  20         w       io.Writer
  21         scratch [64]byte
  22 }
  23
  24 func (e *Encoder) Encode(v interface{}) (err error) {
  25         if v == nil {
  26                 return
  27         }
  28         defer func() {
  29                 if e := recover(); e != nil {
  30                         if _, ok := e.(runtime.Error); ok {
  31                                 panic(e)
  32                         }
  33                         var ok bool
  34                         err, ok = e.(error)
  35                         if !ok {
  36                                 panic(e)
  37                         }
  38                 }
  39         }()
  40         e.reflectValue(reflect.ValueOf(v))
  41         return nil
  42 }
  43
  44 type stringValues []reflect.Value
  45
  46 func (sv stringValues) Len() int           { return len(sv) }
  47 func (sv stringValues) Swap(i, j int)      { sv[i], sv[j] = sv[j], sv[i] }
  48 func (sv stringValues) Less(i, j int) bool { return sv.get(i) < sv.get(j) }
  49 func (sv stringValues) get(i int) string   { return sv[i].String() }
  50
  51 func (e *Encoder) write(s []byte) {
  52         _, err := e.w.Write(s)
  53         if err != nil {
  54                 panic(err)
  55         }
  56 }
  57
  58 func (e *Encoder) writeString(s string) {
  59         for s != "" {
  60                 n := copy(e.scratch[:], s)
  61                 s = s[n:]
  62                 e.write(e.scratch[:n])
  63         }
  64 }
  65
  66 func (e *Encoder) reflectString(s string) {
  67         b := strconv.AppendInt(e.scratch[:0], int64(len(s)), 10)
  68         e.write(b)
  69         e.writeString(":")
  70         e.writeString(s)
  71 }
  72
  73 func (e *Encoder) reflectByteSlice(s []byte) {
  74         b := strconv.AppendInt(e.scratch[:0], int64(len(s)), 10)
  75         e.write(b)
  76         e.writeString(":")
  77         e.write(s)
  78 }
  79
  80 // Returns true if the value implements Marshaler interface and marshaling was
  81 // done successfully.
  82 func (e *Encoder) reflectMarshaler(v reflect.Value) bool {
  83         if !v.Type().Implements(marshalerType) {
  84                 if v.Kind() != reflect.Ptr && v.CanAddr() && v.Addr().Type().Implements(marshalerType) {
  85                         v = v.Addr()
  86                 } else {
  87                         return false
  88                 }
  89         }
  90         m := v.Interface().(Marshaler)
  91         data, err := m.MarshalBencode()
  92         if err != nil {
  93                 panic(&MarshalerError{v.Type(), err})
  94         }
  95         e.write(data)
  96         return true
  97 }
  98
  99 var bigIntType = reflect.TypeOf((*big.Int)(nil)).Elem()
 100
 101 func (e *Encoder) reflectValue(v reflect.Value) {
 102
 103         if e.reflectMarshaler(v) {
 104                 return
 105         }
 106
 107         if v.Type() == bigIntType {
 108                 e.writeString("i")
 109                 bi := v.Interface().(big.Int)
 110                 e.writeString(bi.String())
 111                 e.writeString("e")
 112                 return
 113         }
 114
 115         switch v.Kind() {
 116         case reflect.Bool:
 117                 if v.Bool() {
 118                         e.writeString("i1e")
 119                 } else {
 120                         e.writeString("i0e")
 121                 }
 122         case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
 123                 e.writeString("i")
 124                 b := strconv.AppendInt(e.scratch[:0], v.Int(), 10)
 125                 e.write(b)
 126                 e.writeString("e")
 127         case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
 128                 e.writeString("i")
 129                 b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10)
 130                 e.write(b)
 131                 e.writeString("e")
 132         case reflect.String:
 133                 e.reflectString(v.String())
 134         case reflect.Struct:
 135                 e.writeString("d")
 136                 for _, ef := range getEncodeFields(v.Type()) {
 137                         fieldValue := ef.i(v)
 138                         if !fieldValue.IsValid() {
 139                                 continue
 140                         }
 141                         if ef.omitEmpty && isEmptyValue(fieldValue) {
 142                                 continue
 143                         }
 144                         e.reflectString(ef.tag)
 145                         e.reflectValue(fieldValue)
 146                 }
 147                 e.writeString("e")
 148         case reflect.Map:
 149                 if v.Type().Key().Kind() != reflect.String {
 150                         panic(&MarshalTypeError{v.Type()})
 151                 }
 152                 if v.IsNil() {
 153                         e.writeString("de")
 154                         break
 155                 }
 156                 e.writeString("d")
 157                 sv := stringValues(v.MapKeys())
 158                 sort.Sort(sv)
 159                 for _, key := range sv {
 160                         e.reflectString(key.String())
 161                         e.reflectValue(v.MapIndex(key))
 162                 }
 163                 e.writeString("e")
 164         case reflect.Slice:
 165                 if v.Type().Elem().Kind() == reflect.Uint8 {
 166                         s := v.Bytes()
 167                         e.reflectByteSlice(s)
 168                         break
 169                 }
 170                 if v.IsNil() {
 171                         e.writeString("le")
 172                         break
 173                 }
 174                 fallthrough
 175         case reflect.Array:
 176                 e.writeString("l")
 177                 for i, n := 0, v.Len(); i < n; i++ {
 178                         e.reflectValue(v.Index(i))
 179                 }
 180                 e.writeString("e")
 181         case reflect.Interface:
 182                 e.reflectValue(v.Elem())
 183         case reflect.Ptr:
 184                 if v.IsNil() {
 185                         v = reflect.Zero(v.Type().Elem())
 186                 } else {
 187                         v = v.Elem()
 188                 }
 189                 e.reflectValue(v)
 190         default:
 191                 panic(&MarshalTypeError{v.Type()})
 192         }
 193 }
 194
 195 type encodeField struct {
 196         i         func(v reflect.Value) reflect.Value
 197         tag       string
 198         omitEmpty bool
 199 }
 200
 201 type encodeFieldsSortType []encodeField
 202
 203 func (ef encodeFieldsSortType) Len() int           { return len(ef) }
 204 func (ef encodeFieldsSortType) Swap(i, j int)      { ef[i], ef[j] = ef[j], ef[i] }
 205 func (ef encodeFieldsSortType) Less(i, j int) bool { return ef[i].tag < ef[j].tag }
 206
 207 var (
 208         typeCacheLock     sync.RWMutex
 209         encodeFieldsCache = make(map[reflect.Type][]encodeField)
 210 )
 211
 212 func getEncodeFields(t reflect.Type) []encodeField {
 213         typeCacheLock.RLock()
 214         fs, ok := encodeFieldsCache[t]
 215         typeCacheLock.RUnlock()
 216         if ok {
 217                 return fs
 218         }
 219         fs = makeEncodeFields(t)
 220         typeCacheLock.Lock()
 221         defer typeCacheLock.Unlock()
 222         encodeFieldsCache[t] = fs
 223         return fs
 224 }
 225
 226 func makeEncodeFields(t reflect.Type) (fs []encodeField) {
 227         for _i, n := 0, t.NumField(); _i < n; _i++ {
 228                 i := _i
 229                 f := t.Field(i)
 230                 if f.PkgPath != "" {
 231                         continue
 232                 }
 233                 if f.Anonymous {
 234                         t := f.Type
 235                         if t.Kind() == reflect.Ptr {
 236                                 t = t.Elem()
 237                         }
 238                         anonEFs := makeEncodeFields(t)
 239                         for aefi := range anonEFs {
 240                                 anonEF := anonEFs[aefi]
 241                                 bottomField := anonEF
 242                                 bottomField.i = func(v reflect.Value) reflect.Value {
 243                                         v = v.Field(i)
 244                                         if v.Kind() == reflect.Ptr {
 245                                                 if v.IsNil() {
 246                                                         // This will skip serializing this value.
 247                                                         return reflect.Value{}
 248                                                 }
 249                                                 v = v.Elem()
 250                                         }
 251                                         return anonEF.i(v)
 252                                 }
 253                                 fs = append(fs, bottomField)
 254                         }
 255                         continue
 256                 }
 257                 var ef encodeField
 258                 ef.i = func(v reflect.Value) reflect.Value {
 259                         return v.Field(i)
 260                 }
 261                 ef.tag = f.Name
 262
 263                 tv := getTag(f.Tag)
 264                 if tv.Ignore() {
 265                         continue
 266                 }
 267                 if tv.Key() != "" {
 268                         ef.tag = tv.Key()
 269                 }
 270                 ef.omitEmpty = tv.OmitEmpty()
 271                 fs = append(fs, ef)
 272         }
 273         fss := encodeFieldsSortType(fs)
 274         sort.Sort(fss)
 275         return fs
 276 }