diff options
Diffstat (limited to 'libgo/go/encoding/binary/binary.go')
| -rw-r--r-- | libgo/go/encoding/binary/binary.go | 49 |
1 files changed, 41 insertions, 8 deletions
diff --git a/libgo/go/encoding/binary/binary.go b/libgo/go/encoding/binary/binary.go index 712e490e656..06670141e16 100644 --- a/libgo/go/encoding/binary/binary.go +++ b/libgo/go/encoding/binary/binary.go @@ -125,6 +125,9 @@ func (bigEndian) GoString() string { return "binary.BigEndian" } // of fixed-size values. // Bytes read from r are decoded using the specified byte order // and written to successive fields of the data. +// When reading into structs, the field data for fields with +// blank (_) field names is skipped; i.e., blank field names +// may be used for padding. func Read(r io.Reader, order ByteOrder, data interface{}) error { // Fast path for basic types. if n := intDestSize(data); n != 0 { @@ -154,7 +157,7 @@ func Read(r io.Reader, order ByteOrder, data interface{}) error { return nil } - // Fallback to reflect-based. + // Fallback to reflect-based decoding. var v reflect.Value switch d := reflect.ValueOf(data); d.Kind() { case reflect.Ptr: @@ -181,6 +184,8 @@ func Read(r io.Reader, order ByteOrder, data interface{}) error { // values, or a pointer to such data. // Bytes written to w are encoded using the specified byte order // and read from successive fields of the data. +// When writing structs, zero values are are written for fields +// with blank (_) field names. func Write(w io.Writer, order ByteOrder, data interface{}) error { // Fast path for basic types. var b [8]byte @@ -239,6 +244,8 @@ func Write(w io.Writer, order ByteOrder, data interface{}) error { _, err := w.Write(bs) return err } + + // Fallback to reflect-based encoding. v := reflect.Indirect(reflect.ValueOf(data)) size := dataSize(v) if size < 0 { @@ -300,15 +307,13 @@ func sizeof(t reflect.Type) int { return -1 } -type decoder struct { +type coder struct { order ByteOrder buf []byte } -type encoder struct { - order ByteOrder - buf []byte -} +type decoder coder +type encoder coder func (d *decoder) uint8() uint8 { x := d.buf[0] @@ -379,9 +384,19 @@ func (d *decoder) value(v reflect.Value) { } case reflect.Struct: + t := v.Type() l := v.NumField() for i := 0; i < l; i++ { - d.value(v.Field(i)) + // Note: Calling v.CanSet() below is an optimization. + // It would be sufficient to check the field name, + // but creating the StructField info for each field is + // costly (run "go test -bench=ReadStruct" and compare + // results when making changes to this code). + if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" { + d.value(v) + } else { + d.skip(v) + } } case reflect.Slice: @@ -435,9 +450,15 @@ func (e *encoder) value(v reflect.Value) { } case reflect.Struct: + t := v.Type() l := v.NumField() for i := 0; i < l; i++ { - e.value(v.Field(i)) + // see comment for corresponding code in decoder.value() + if v := v.Field(i); v.CanSet() || t.Field(i).Name != "_" { + e.value(v) + } else { + e.skip(v) + } } case reflect.Slice: @@ -492,6 +513,18 @@ func (e *encoder) value(v reflect.Value) { } } +func (d *decoder) skip(v reflect.Value) { + d.buf = d.buf[dataSize(v):] +} + +func (e *encoder) skip(v reflect.Value) { + n := dataSize(v) + for i := range e.buf[0:n] { + e.buf[i] = 0 + } + e.buf = e.buf[n:] +} + // intDestSize returns the size of the integer that ptrType points to, // or 0 if the type is not supported. func intDestSize(ptrType interface{}) int { |