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November 29, 2015 23:40
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github.com/ugorji/go/codec decode issue with extension objects
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// This file demonstrates an issue decoding nested extension objects. | |
// The actual extension is a simple wrapper for a Python tuple, which | |
// is implemented by wrapping a simple CBOR list with CBOR tag 128. | |
package main | |
import ( | |
"github.com/ugorji/go/codec" | |
"reflect" | |
"testing" | |
) | |
// Tuple wrapper object --------------------------------------------- | |
// PythonTuple is a simple Go wrapper representing a Python tuple. | |
// This is a fixed-length, ordered, immutable sequence of arbitrary | |
// items. | |
type PythonTuple struct { | |
Items []interface{} | |
} | |
// Codec library extension ------------------------------------------ | |
// pythonTupleExt is a codec extension plugin to encode and decode | |
// PythonTuple objects. | |
type pythonTupleExt struct { | |
} | |
func (x pythonTupleExt) ConvertExt(v interface{}) interface{} { | |
var ptuple *PythonTuple | |
ptuple, ok := v.(*PythonTuple) | |
if !ok { | |
tuple := v.(PythonTuple) | |
ptuple = &tuple | |
} | |
if ptuple.Items != nil { | |
return ptuple.Items | |
} | |
return []interface{}{} | |
} | |
func (x pythonTupleExt) UpdateExt(dest interface{}, v interface{}) { | |
items := v.([]interface{}) | |
tuple := dest.(*PythonTuple) | |
*tuple = PythonTuple{items} | |
} | |
// SetExts assigns the Python tuple extension to a CBOR transcoder | |
// with tag 128. | |
func SetExts(cbor *codec.CborHandle) error { | |
var tuple PythonTuple | |
return cbor.SetInterfaceExt(reflect.TypeOf(tuple), 128, | |
&pythonTupleExt{}) | |
} | |
// Test data -------------------------------------------------------- | |
// Data produces the test data. The output of this are a fully set | |
// up CBOR transcoder, reference byte data, and a reference object. | |
// data should be a valid CBOR encoding of obj. | |
// | |
// This appears to be a minimal object tree to reproduce the issue. | |
// Removing any single object from the tree results in the decode | |
// test passing. | |
func Data() (cbor *codec.CborHandle, data []byte, obj interface{}) { | |
cbor = new(codec.CborHandle) | |
err := SetExts(cbor) | |
if err != nil { | |
panic(err) | |
} | |
bottomV := []interface{}{} | |
bottomD := []byte{0x80} | |
tupleV := PythonTuple{Items: []interface{}{bottomV}} | |
tupleD := append([]byte{0xD8, 0x80, 0x81}, bottomD...) | |
listV := []interface{}{tupleV} | |
listD := append([]byte{0x81}, tupleD...) | |
listTupleV := PythonTuple{Items: []interface{}{listV}} | |
listTupleD := append([]byte{0xD8, 0x80, 0x81}, listD...) | |
topV := []interface{}{listTupleV} | |
topD := append([]byte{0x81}, listTupleD...) | |
return cbor, topD, topV | |
} | |
// Tests ------------------------------------------------------------ | |
// TestEncode verifies that encoding the reference object produces the | |
// reference data. This test passes. | |
func TestEncode(t *testing.T) { | |
cbor, expected, obj := Data() | |
var actual []byte | |
encoder := codec.NewEncoderBytes(&actual, cbor) | |
encoder.MustEncode(obj) | |
if !reflect.DeepEqual(expected, actual) { | |
t.Errorf("encode: expected %+v actual %+v", expected, actual) | |
} | |
} | |
// TestDecode verifies that decoding the reference data produces the | |
// reference data. This test fails: instead of producing a list of | |
// a single tuple object, it produces an empty list. | |
func TestDecode(t *testing.T) { | |
cbor, data, expected := Data() | |
decoder := codec.NewDecoderBytes(data, cbor) | |
var actual interface{} | |
decoder.MustDecode(&actual) | |
if !reflect.DeepEqual(expected, actual) { | |
t.Errorf("decode: expected %+v actual %+v", expected, actual) | |
} | |
} |
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