package bencode import ( "io" "reflect" "runtime" "sort" "strconv" "sync" "github.com/anacrolix/missinggo" ) func isEmptyValue(v reflect.Value) bool { return missinggo.IsEmptyValue(v) } type Encoder struct { w interface { Flush() error io.Writer WriteString(string) (int, error) } 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 e.w.Flush() } type string_values []reflect.Value func (sv string_values) Len() int { return len(sv) } func (sv string_values) Swap(i, j int) { sv[i], sv[j] = sv[j], sv[i] } func (sv string_values) Less(i, j int) bool { return sv.get(i) < sv.get(j) } func (sv string_values) 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) { _, err := e.w.WriteString(s) if err != nil { panic(err) } } func (e *Encoder) reflectString(s string) { b := strconv.AppendInt(e.scratch[:0], int64(len(s)), 10) e.write(b) e.writeString(":") e.writeString(s) } func (e *Encoder) reflectByteSlice(s []byte) { b := strconv.AppendInt(e.scratch[:0], int64(len(s)), 10) e.write(b) e.writeString(":") e.write(s) } // returns true if the value implements Marshaler interface and marshaling was // done successfully func (e *Encoder) reflectMarshaler(v reflect.Value) bool { m, ok := v.Interface().(Marshaler) if !ok { // T doesn't work, try *T if v.Kind() != reflect.Ptr && v.CanAddr() { m, ok = v.Addr().Interface().(Marshaler) if ok { v = v.Addr() } } } if ok && (v.Kind() != reflect.Ptr || !v.IsNil()) { data, err := m.MarshalBencode() if err != nil { panic(&MarshalerError{v.Type(), err}) } e.write(data) return true } return false } func (e *Encoder) reflectValue(v reflect.Value) { if e.reflectMarshaler(v) { 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: b := strconv.AppendInt(e.scratch[:0], v.Int(), 10) e.writeString("i") e.write(b) e.writeString("e") case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64: b := strconv.AppendUint(e.scratch[:0], v.Uint(), 10) e.writeString("i") e.write(b) e.writeString("e") case reflect.String: e.reflectString(v.String()) case reflect.Struct: e.writeString("d") for _, ef := range encodeFields(v.Type()) { field_value := v.Field(ef.i) if ef.omit_empty && isEmptyValue(field_value) { continue } e.reflectString(ef.tag) e.reflectValue(field_value) } 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 := string_values(v.MapKeys()) sort.Sort(sv) for _, key := range sv { e.reflectString(key.String()) e.reflectValue(v.MapIndex(key)) } e.writeString("e") case reflect.Slice: if v.IsNil() { e.writeString("le") break } if v.Type().Elem().Kind() == reflect.Uint8 { s := v.Bytes() e.reflectByteSlice(s) break } fallthrough case reflect.Array: e.writeString("l") for i, n := 0, v.Len(); i < n; i++ { e.reflectValue(v.Index(i)) } e.writeString("e") 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()}) } } type encodeField struct { i int tag string omit_empty 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 encodeFields(t reflect.Type) []encodeField { typeCacheLock.RLock() fs, ok := encodeFieldsCache[t] typeCacheLock.RUnlock() if ok { return fs } typeCacheLock.Lock() defer typeCacheLock.Unlock() fs, ok = encodeFieldsCache[t] if ok { return fs } for i, n := 0, t.NumField(); i < n; i++ { f := t.Field(i) if f.PkgPath != "" { continue } if f.Anonymous { continue } var ef encodeField ef.i = i ef.tag = f.Name tv := f.Tag.Get("bencode") if tv != "" { if tv == "-" { continue } name, opts := parseTag(tv) if name != "" { ef.tag = name } ef.omit_empty = opts.contains("omitempty") } fs = append(fs, ef) } fss := encodeFieldsSortType(fs) sort.Sort(fss) encodeFieldsCache[t] = fs return fs }