fix: Parse private sequences if they have an undefined length.

Fixes a bug where private sequences would attempt to be parsed as items. Also, add a test to verify that private sequences with explicit lengths are skipped.
cornerstonejs · Sep 26, 2022 · 24cc195 · 24cc195
1 parent eb51626
commit 24cc195
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diff --git a/src/readDicomElementImplicit.js b/src/readDicomElementImplicit.js
@@ -52,10 +52,15 @@ export default function readDicomElementImplicit (byteStream, untilTag, vrCallba
     return element;
   }
 
-  if (isSequence(element, byteStream, vrCallback) && !isPrivateTag(element.tag)) {
+  // always parse sequences with undefined lengths, since there's no other way to know how long they are.
+  if (isSequence(element, byteStream, vrCallback) && (!isPrivateTag(element.tag) || element.hadUndefinedLength)) {
     // parse the sequence
     readSequenceItemsImplicit(byteStream, element);
 
+    if (isPrivateTag(element.tag)) {
+      element.items = undefined;
+    }
+
     return element;
   }
 

diff --git a/test/readDicomElementImplicit_test.js b/test/readDicomElementImplicit_test.js
@@ -238,4 +238,67 @@ describe('readDicomElementImplicit', () => {
     expect(element.length).to.equal(11);
   });
 
+  it('private sequence with explicit length is skipped', () => {
+    // Arrange
+    // (0009,0006)                       length: 26
+    const bytes = [0x09, 0x00, 0x06, 0x00, 0x1a, 0x00, 0x00, 0x00,
+      // (fffe,e000)                     length: undefined
+      0xfe, 0xff, 0x00, 0xe0, 0xff, 0xff, 0xff, 0xff,
+      // (0008,0018)                      length: 2   'B'
+      0x08, 0x00, 0x18, 0x00, 0x02, 0x00, 0x00, 0x00, 0x42, 0x20,
+      // (fffe,e00d)                     length: 0
+      0xfe, 0xff, 0x0d, 0xe0, 0x00, 0x00, 0x00, 0x00,
+      // (0008,0100)                      length: 2   'A'
+      0x08, 0x00, 0x00, 0x01, 0x02, 0x00, 0x00, 0x00, 0x41, 0x20,
+    ];
+
+    const byteStream = new ByteStream(littleEndianByteArrayParser, convertToByteArray(bytes));
+
+    // Act
+    const element = readDicomElementImplicit(byteStream);
+
+    // Assert
+    expect(element.tag).to.equal('x00090006');
+    expect(element.items).to.equal(undefined);
+    expect(element.length).to.equal(26);
+
+    // Read the next element
+    const nextElement = readDicomElementImplicit(byteStream);
+    expect(nextElement.tag).to.equal('x00080100');
+    expect(nextElement.length).to.equal(2);
+  });
+
+  it('private sequence with implicit length is skipped', () => {
+    // Arrange
+    // (0009,0006)                       length: undefined
+    const bytes = [0x09, 0x00, 0x06, 0x00, 0xff, 0xff, 0xff, 0xff,
+      // (fffe,e000)                     length: undefined
+      0xfe, 0xff, 0x00, 0xe0, 0xff, 0xff, 0xff, 0xff,
+      // (0008,0018)                      length: 4   'ABC '
+      0x08, 0x00, 0x18, 0x00, 0x04, 0x00, 0x00, 0x00, 0x41, 0x42, 0x43, 0x20,
+      // (fffe,e00d)                     length: 0
+      0xfe, 0xff, 0x0d, 0xe0, 0x00, 0x00, 0x00, 0x00,
+      // (fffe,e0dd)                     length: 0
+      0xfe, 0xff, 0xdd, 0xe0, 0x00, 0x00, 0x00, 0x00,
+      // (0008,0100)                      length: 2   'A'
+      0x08, 0x00, 0x00, 0x01, 0x02, 0x00, 0x00, 0x00, 0x41, 0x20,
+    ];
+
+    const byteStream = new ByteStream(littleEndianByteArrayParser, convertToByteArray(bytes));
+
+    // Act
+    const element = readDicomElementImplicit(byteStream);
+
+    // Assert
+    expect(element.tag).to.equal('x00090006');
+    expect(element.items).to.equal(undefined);
+    expect(element.length).to.equal(28);
+
+    // Read the next element
+    const nextElement = readDicomElementImplicit(byteStream);
+    expect(nextElement.tag).to.equal('x00080100');
+    expect(nextElement.length).to.equal(2);
+  });
+
+
 });