Handle unknowns completely

.github/workflows/bench_pr.yml

@@ -6,10 +6,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - name: Set up Go 1.15
+    - name: Set up Go 1.18
       uses: actions/setup-go@v2
       with:
-        go-version: 1.15
+        go-version: 1.18
       id: go
 
     - name: Check out code 

.github/workflows/bench_push.yml

@@ -5,10 +5,10 @@ jobs:
     name: Benchmark (push)
     runs-on: ubuntu-latest
     steps:
-    - name: Set up Go 1.15
+    - name: Set up Go 1.18
       uses: actions/setup-go@v2
       with:
-        go-version: 1.15
+        go-version: 1.18
       id: go
 
     - name: Check out code 

.github/workflows/go.yml

@@ -7,10 +7,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
 
-    - name: Set up Go 1.15
+    - name: Set up Go 1.18
       uses: actions/setup-go@v2
       with:
-        go-version: 1.15
+        go-version: 1.18
       id: go
 
     - name: Check out code 

dataset_test.go

@@ -8,20 +8,28 @@ import (
 	"github.com/suyashkumar/dicom/pkg/tag"
 )
 
-func makeSequenceElement(tg tag.Tag, items [][]*Element) *Element {
+func makeSequenceElement(tg tag.Tag, items [][]*Element, unknown bool) *Element {
 	sequenceItems := make([]*SequenceItemValue, 0, len(items))
 	for _, item := range items {
 		sequenceItems = append(sequenceItems, &SequenceItemValue{elements: item})
 	}
 
-	return &Element{
+	e := &Element{
 		Tag:                    tg,
 		ValueRepresentation:    tag.VRSequence,
 		RawValueRepresentation: "SQ",
 		Value: &sequencesValue{
 			value: sequenceItems,
 		},
 	}
+
+	if unknown {
+		e.ValueRepresentation = tag.VRUnknown
+		e.RawValueRepresentation = "UN"
+		e.ValueLength = tag.VLUndefinedLength
+	}
+
+	return e
 }
 
 func TestDataset_FindElementByTag(t *testing.T) {
@@ -83,9 +91,9 @@ func TestDataset_FlatStatefulIterator(t *testing.T) {
 							{
 								mustNewElement(tag.PatientName, []string{"Bob", "Smith"}),
 							},
-						}),
+						}, false),
 					},
-				}),
+				}, false),
 			}},
 			expectedFlatElements: []*Element{
 				// First, expect the entire SQ element
@@ -98,17 +106,17 @@ func TestDataset_FlatStatefulIterator(t *testing.T) {
 							{
 								mustNewElement(tag.PatientName, []string{"Bob", "Smith"}),
 							},
-						}),
+						}, false),
 					},
-				}),
+				}, false),
 				// Then expect the inner elements
 				mustNewElement(tag.PatientName, []string{"Bob", "Jones"}),
 				// Inner SQ element
 				makeSequenceElement(tag.AnatomicRegionSequence, [][]*Element{
 					{
 						mustNewElement(tag.PatientName, []string{"Bob", "Smith"}),
 					},
-				}),
+				}, false),
 				// Inner element of the inner SQ
 				mustNewElement(tag.PatientName, []string{"Bob", "Smith"}),
 			},
@@ -139,7 +147,7 @@ func ExampleDataset_FlatIterator() {
 		Elements: []*Element{
 			mustNewElement(tag.Rows, []int{100}),
 			mustNewElement(tag.Columns, []int{100}),
-			makeSequenceElement(tag.AddOtherSequence, nestedData),
+			makeSequenceElement(tag.AddOtherSequence, nestedData, false),
 		},
 	}
 
@@ -172,7 +180,7 @@ func ExampleDataset_FlatIteratorWithExhaustAllElements() {
 		Elements: []*Element{
 			mustNewElement(tag.Rows, []int{100}),
 			mustNewElement(tag.Columns, []int{100}),
-			makeSequenceElement(tag.AddOtherSequence, nestedData),
+			makeSequenceElement(tag.AddOtherSequence, nestedData, false),
 		},
 	}
 
@@ -220,7 +228,7 @@ func ExampleDataset_FlatStatefulIterator() {
 					value: []int{200},
 				},
 			},
-			makeSequenceElement(tag.AddOtherSequence, nestedData),
+			makeSequenceElement(tag.AddOtherSequence, nestedData, false),
 		},
 	}
 

element_test.go

@@ -21,7 +21,7 @@ func TestElement_MarshalJSON_NestedElements(t *testing.T) {
 			},
 		},
 	}
-	seqElement := makeSequenceElement(tag.AddOtherSequence, nestedData)
+	seqElement := makeSequenceElement(tag.AddOtherSequence, nestedData, false)
 
 	want := `{"tag":{"Group":70,"Element":258},"VR":9,"rawVR":"SQ","valueLength":0,"value":[[{"tag":{"Group":16,"Element":16},"VR":2,"rawVR":"","valueLength":0,"value":["Bob"]}]]}`
 

pkg/charset/charset.go

@@ -40,6 +40,7 @@ const (
 // htmlEncodingNames represents a mapping of DICOM charset name to golang encoding/htmlindex name.  "" means
 // 7bit ascii.
 var htmlEncodingNames = map[string]string{
+	"":                "iso-8859-1",
 	"ISO_IR 6":        "iso-8859-1",
 	"ISO 2022 IR 6":   "iso-8859-1",
 	"ISO_IR 13":       "shift_jis",

pkg/tag/tag.go

@@ -114,6 +114,9 @@ const (
 	VRDate
 	// VRPixelData means the element stores a PixelDataInfo
 	VRPixelData
+	// VRUnknown means the VR of the element is unknown (possibly a private
+	// element seen while reading DICOMs in implicit transfer syntax).
+	VRUnknown
 )
 
 // GetVRKind returns the golang value encoding of an element with <tag, vr>.
@@ -146,6 +149,8 @@ func GetVRKind(tag Tag, vr string) VRKind {
 		return VRFloat64List
 	case "SQ":
 		return VRSequence
+	case "UN":
+		return VRUnknown
 	default:
 		return VRStringList
 	}

read.go

@@ -116,6 +116,19 @@ func readValue(r dicomio.Reader, t tag.Tag, vr string, vl uint32, isImplicit boo
 		return readPixelData(r, t, vr, vl, d, fc)
 	case tag.VRFloat32List, tag.VRFloat64List:
 		return readFloat(r, t, vr, vl)
+	// More details on how we treat Unknown VRs can be found at
+	// https://github.com/suyashkumar/dicom/issues/220
+	// and
+	// https://github.com/suyashkumar/dicom/issues/231.
+	// It remains to be seen if this fits most DICOMs we see in the wild.
+	// TODO(suyashkumar): consider replacing UN VRs with SQ earlier on if they
+	// meet this criteria, so users of the Dataset can interact with it
+	// correctly.
+	case tag.VRUnknown:
+		if isImplicit && vl == tag.VLUndefinedLength {
+			return readSequence(r, t, vr, vl)
+		}
+		return readBytes(r, t, vr, vl)
 	default:
 		return readString(r, t, vr, vl)
 	}
@@ -422,7 +435,7 @@ func readSequenceItem(r dicomio.Reader, t tag.Tag, vr string, vl uint32) (Value,
 
 func readBytes(r dicomio.Reader, t tag.Tag, vr string, vl uint32) (Value, error) {
 	// TODO: add special handling of PixelData
-	if vr == vrraw.OtherByte {
+	if vr == vrraw.OtherByte || vr == vrraw.Unknown {
 		data := make([]byte, vl)
 		_, err := io.ReadFull(r, data)
 		return &bytesValue{value: data}, err
@@ -466,7 +479,6 @@ func readString(r dicomio.Reader, t tag.Tag, vr string, vl uint32) (Value, error
 
 	// Split multiple strings
 	strs := strings.Split(str, "\\")
-
 	return &stringsValue{value: strs}, err
 }
 

read_test.go

@@ -168,12 +168,19 @@ func TestReadOWBytes(t *testing.T) {
 		expectedErr error
 	}{
 		{
-			name:        "even-number bytes",
+			name:        "OW VR with even-number bytes",
 			bytes:       []byte{0x1, 0x2, 0x3, 0x4},
 			VR:          vrraw.OtherWord,
 			want:        &bytesValue{value: []byte{0x1, 0x2, 0x3, 0x4}},
 			expectedErr: nil,
 		},
+		{
+			name:        "UN VR even-number bytes",
+			bytes:       []byte{0x1, 0x2, 0x3, 0x4},
+			VR:          vrraw.Unknown,
+			want:        &bytesValue{value: []byte{0x1, 0x2, 0x3, 0x4}},
+			expectedErr: nil,
+		},
 		{
 			name:        "error on odd-number bytes",
 			bytes:       []byte{0x1, 0x2, 0x3},

write.go

@@ -321,6 +321,8 @@ func verifyValueType(t tag.Tag, value Value, vr string) error {
 		}
 	case vrraw.FloatingPointSingle, vrraw.FloatingPointDouble:
 		ok = valueType == Floats
+	case vrraw.Unknown:
+		ok = (valueType == Bytes || valueType == Sequences)
 	default:
 		ok = valueType == Strings
 	}
@@ -488,7 +490,7 @@ func writeStrings(w dicomio.Writer, values []string, vr string) error {
 func writeBytes(w dicomio.Writer, values []byte, vr string) error {
 	var err error
 	switch vr {
-	case vrraw.OtherWord:
+	case vrraw.OtherWord, vrraw.Unknown:
 		err = writeOtherWordString(w, values)
 	case vrraw.OtherByte:
 		err = writeOtherByteString(w, values)

write_test.go

@@ -47,6 +47,17 @@ func TestWrite(t *testing.T) {
 				mustNewElement(tag.FloatingPointValue, []float64{128.10}),
 				mustNewElement(tag.DimensionIndexPointer, []int{32, 36950}),
 				mustNewElement(tag.RedPaletteColorLookupTableData, []byte{0x1, 0x2, 0x3, 0x4}),
+				mustNewElement(tag.SelectorSLValue, []int{-20}),
+				// Some tag with an unknown VR.
+				{
+					Tag:                    tag.Tag{0x0019, 0x1027},
+					ValueRepresentation:    tag.VRUnknown,
+					RawValueRepresentation: "UN",
+					ValueLength:            4,
+					Value: &bytesValue{
+						value: []byte{0x1, 0x2, 0x3, 0x4},
+					},
+				},
 			}},
 			expectedError: nil,
 		},
@@ -108,7 +119,7 @@ func TestWrite(t *testing.T) {
 							},
 						},
 					},
-				}),
+				}, false),
 			}},
 			expectedError: nil,
 		},
@@ -158,7 +169,7 @@ func TestWrite(t *testing.T) {
 							},
 						},
 					},
-				}),
+				}, false),
 			}},
 			expectedError: nil,
 			opts:          []WriteOption{SkipVRVerification()},
@@ -193,9 +204,45 @@ func TestWrite(t *testing.T) {
 									},
 								},
 							},
-						}),
+						}, false),
 					},
-				}),
+				}, false),
+			}},
+			expectedError: nil,
+		},
+		{
+			name: "nested unknown sequences",
+			dataset: Dataset{Elements: []*Element{
+				mustNewElement(tag.MediaStorageSOPClassUID, []string{"1.2.840.10008.5.1.4.1.1.1.13"}),
+				mustNewElement(tag.MediaStorageSOPInstanceUID, []string{"1.2.3.4.5.6.7"}),
+				mustNewElement(tag.TransferSyntaxUID, []string{uid.ImplicitVRLittleEndian}),
+				mustNewElement(tag.PatientName, []string{"Bob", "Jones"}),
+				makeSequenceElement(tag.Tag{0x0019, 0x1027}, [][]*Element{
+					// Item 1.
+					{
+						{
+							Tag:                    tag.Tag{0x0019, 0x1028},
+							ValueRepresentation:    tag.VRUnknown,
+							RawValueRepresentation: "UN",
+							Value: &bytesValue{
+								value: []byte{0x1, 0x2, 0x3, 0x4},
+							},
+						},
+						// Nested Sequence.
+						makeSequenceElement(tag.Tag{0x0019, 0x1029}, [][]*Element{
+							{
+								{
+									Tag:                    tag.PatientName,
+									ValueRepresentation:    tag.VRStringList,
+									RawValueRepresentation: "PN",
+									Value: &stringsValue{
+										value: []string{"Bob", "Jones"},
+									},
+								},
+							},
+						}, true),
+					},
+				}, true),
 			}},
 			expectedError: nil,
 		},
@@ -229,9 +276,9 @@ func TestWrite(t *testing.T) {
 									},
 								},
 							},
-						}),
+						}, false),
 					},
-				}),
+				}, false),
 			}},
 			expectedError: nil,
 			opts:          []WriteOption{SkipVRVerification()},