Implement copyElement Method for the TlvWriter Class in Kotlin (#26377)

- Added helper method peekElement() to the TlvReader class
  - Added new method and new testcases.
  - Some other minor fixes and cleanups.

Author: emargolis

src/controller/java/src/chip/tlv/TlvReader.kt

@@ -101,6 +101,19 @@ class TlvReader(bytes: ByteArray) : Iterable<Element> {
     return Element(tag, value)
   }
 
+  /**
+   * Reads the next element from the TLV. Unlike nextElement() this method leaves the TLV reader
+   * positioned at the same element and doesn't advance it to the next element.
+   *
+   * @throws TlvParsingException if the TLV data was invalid
+   */
+  fun peekElement(): Element {
+    val currentIndex = index
+    val element = nextElement()
+    index = currentIndex
+    return element
+  }
+
   /**
    * Reads the encoded Long value and advances to the next element.
    *

src/controller/java/src/chip/tlv/TlvWriter.kt

@@ -47,12 +47,14 @@ class TlvWriter(initialCapacity: Int = 32) {
         "Invalid use of context tag at index ${bytes.size()}: can only be used within a " +
           "structure or a list"
       }
-    }
-
-    if (containerDepth > 0 && containerType[containerDepth - 1] is ArrayType) {
+    } else if (containerType[containerDepth - 1] is ArrayType) {
       require(tag is AnonymousTag) {
         "Invalid element tag at index ${bytes.size()}: elements of an array SHALL be anonymous"
       }
+    } else if (containerType[containerDepth - 1] is StructureType && type !is EndOfContainerType) {
+      require(tag !is AnonymousTag) {
+        "Invalid element tag at index ${bytes.size()}: elements of a structure cannot be anonymous"
+      }
     }
 
     if (tag is ContextSpecificTag) {
@@ -326,6 +328,62 @@ class TlvWriter(initialCapacity: Int = 32) {
     return put(Element(AnonymousTag, EndOfContainerValue))
   }
 
+  /**
+   * Copies a TLV element from a reader object into the writer.
+   *
+   * This method encodes a new TLV element whose type, tag and value are taken from a TlvReader
+   * object. When the method is called, the supplied reader object is expected to be positioned on
+   * the source TLV element. The newly encoded element will have the same type, tag and contents as
+   * the input container. If the supplied element is a TLV container (structure, array or list), the
+   * entire contents of the container will be copied.
+   *
+   * @param reader a TlvReader object positioned at a Tlv element whose tag, type and value should
+   *   be copied. If this method is executed successfully, the reader will be positioned at the end
+   *   of the element that was copied.
+   */
+  fun copyElement(reader: TlvReader): TlvWriter {
+    return copyElement(reader.peekElement().tag, reader)
+  }
+
+  /**
+   * Copies a TLV element from a reader object into the writer.
+   *
+   * This method encodes a new TLV element whose type and value are taken from a TLVReader object.
+   * When the method is called, the supplied reader object is expected to be positioned on the
+   * source TLV element. The newly encoded element will have the same type and contents as the input
+   * container, however the tag will be set to the specified argument. If the supplied element is a
+   * TLV container (structure, array or list), the entire contents of the container will be copied.
+   *
+   * @param tag the TLV tag to be encoded with the element.
+   * @param reader a TlvReader object positioned at a Tlv element whose type and value should be
+   *   copied. If this method is executed successfully, the reader will be positioned at the end of
+   *   the element that was copied.
+   */
+  fun copyElement(tag: Tag, reader: TlvReader): TlvWriter {
+    var depth = 0
+    do {
+      val element = reader.nextElement()
+      val value = element.value
+
+      when (depth) {
+        0 -> {
+          require(value !is EndOfContainerValue) {
+            "The TlvReader is positioned at invalid element: EndOfContainer"
+          }
+          put(Element(tag, value))
+        }
+        else -> put(element)
+      }
+
+      if (value is EndOfContainerValue) {
+        depth--
+      } else if (value is StructureValue || value is ArrayValue || value is ListValue) {
+        depth++
+      }
+    } while (depth > 0)
+    return this
+  }
+
   /** Returns the total number of bytes written since the writer was initialized. */
   fun getLengthWritten(): Int {
     return bytes.size()
@@ -334,9 +392,7 @@ class TlvWriter(initialCapacity: Int = 32) {
   /** Verifies that all open containers are closed. */
   fun validateTlv(): TlvWriter {
     if (containerDepth > 0) {
-      throw TlvEncodingException(
-        "Invalid Tlv data at index ${bytes.size()}: $containerDepth containers are not closed"
-      )
+      throw TlvEncodingException("Invalid Tlv data: $containerDepth containers are not closed")
     }
     return this
   }

src/controller/java/tests/chip/tlv/TlvReadWriteTest.kt

@@ -63,8 +63,8 @@ private val testTlvSampleData: ByteArray =
     .map { it.toByte() }
     .toByteArray()
 
-private val testVendorId: UShort = 0xAABBu
-private val testProductId: UShort = 0xCCDDu
+private const val TEST_VENDOR_ID: UShort = 0xAABBu
+private const val TEST_PRODUCT_ID: UShort = 0xCCDDu
 
 private val testLargeString: String =
   """
@@ -86,8 +86,8 @@ class TlvReadWriteTest {
   @Test
   fun testTlvSampleData_write() {
     TlvWriter().apply {
-      startStructure(FullyQualifiedTag(6, testVendorId, testProductId, 1u))
-      put(FullyQualifiedTag(6, testVendorId, testProductId, 2u), true)
+      startStructure(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 1u))
+      put(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 2u), true)
       put(ImplicitProfileTag(2, 2u), false)
       startArray(ContextSpecificTag(0))
       put(AnonymousTag, 42)
@@ -97,15 +97,15 @@ class TlvReadWriteTest {
       startStructure(AnonymousTag)
       endStructure()
       startList(AnonymousTag)
-      putNull(FullyQualifiedTag(6, testVendorId, testProductId, 17u))
+      putNull(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 17u))
       putNull(ImplicitProfileTag(4, 900000u))
       putNull(AnonymousTag)
       startStructure(ImplicitProfileTag(4, 4000000000u))
       put(CommonProfileTag(4, 70000u), testLargeString)
       endStructure()
       endList()
       endArray()
-      put(FullyQualifiedTag(6, testVendorId, testProductId, 5u), "This is a test")
+      put(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 5u), "This is a test")
       put(ImplicitProfileTag(2, 65535u), 17.9f)
       put(ImplicitProfileTag(4, 65536u), 17.9)
       endStructure()
@@ -117,8 +117,8 @@ class TlvReadWriteTest {
   @Test
   fun testTlvSampleData_read() {
     TlvReader(testTlvSampleData).apply {
-      enterStructure(FullyQualifiedTag(6, testVendorId, testProductId, 1u))
-      assertThat(getBool(FullyQualifiedTag(6, testVendorId, testProductId, 2u))).isEqualTo(true)
+      enterStructure(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 1u))
+      assertThat(getBool(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 2u))).isEqualTo(true)
       assertThat(getBool(ImplicitProfileTag(2, 2u))).isEqualTo(false)
       enterArray(ContextSpecificTag(0))
       assertThat(getInt(AnonymousTag)).isEqualTo(42)
@@ -128,15 +128,15 @@ class TlvReadWriteTest {
       enterStructure(AnonymousTag)
       exitContainer()
       enterList(AnonymousTag)
-      getNull(FullyQualifiedTag(6, testVendorId, testProductId, 17u))
+      getNull(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 17u))
       getNull(ImplicitProfileTag(4, 900000u))
       getNull(AnonymousTag)
       enterStructure(ImplicitProfileTag(4, 4000000000u))
       assertThat(getUtf8String(CommonProfileTag(4, 70000u))).isEqualTo(testLargeString)
       exitContainer()
       exitContainer()
       exitContainer()
-      assertThat(getUtf8String(FullyQualifiedTag(6, testVendorId, testProductId, 5u)))
+      assertThat(getUtf8String(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 5u)))
         .isEqualTo("This is a test")
       assertThat(getFloat(ImplicitProfileTag(2, 65535u))).isEqualTo(17.9f)
       assertThat(getDouble(ImplicitProfileTag(4, 65536u))).isEqualTo(17.9)
@@ -149,13 +149,13 @@ class TlvReadWriteTest {
   @Test
   fun testTlvSampleData_read_useSkipElementAndExitContinerInTheMiddle() {
     TlvReader(testTlvSampleData).apply {
-      enterStructure(FullyQualifiedTag(6, testVendorId, testProductId, 1u))
+      enterStructure(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 1u))
       skipElement()
       assertThat(getBool(ImplicitProfileTag(2, 2u))).isEqualTo(false)
       enterArray(ContextSpecificTag(0))
       assertThat(getInt(AnonymousTag)).isEqualTo(42)
       exitContainer()
-      assertThat(getUtf8String(FullyQualifiedTag(6, testVendorId, testProductId, 5u)))
+      assertThat(getUtf8String(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 5u)))
         .isEqualTo("This is a test")
       assertThat(getFloat(ImplicitProfileTag(2, 65535u))).isEqualTo(17.9f)
       assertThat(getDouble(ImplicitProfileTag(4, 65536u))).isEqualTo(17.9)
@@ -165,6 +165,77 @@ class TlvReadWriteTest {
     }
   }
 
+  @Test
+  fun testTlvSampleData_copyElement() {
+    val reader = TlvReader(testTlvSampleData)
+    val encoding = TlvWriter().copyElement(reader).validateTlv().getEncoded()
+    assertThat(encoding).isEqualTo(testTlvSampleData)
+  }
+
+  @Test
+  fun testTlvSampleData_copyElementWithTag() {
+    val reader = TlvReader(testTlvSampleData)
+    val encoding =
+      TlvWriter()
+        .copyElement(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 1u), reader)
+        .validateTlv()
+        .getEncoded()
+    assertThat(encoding).isEqualTo(testTlvSampleData)
+  }
+
+  @Test
+  fun testCopyElement_throwsIllegalArgumentException() {
+    val encoding =
+      TlvWriter().startStructure(AnonymousTag).endStructure().validateTlv().getEncoded()
+    val reader = TlvReader(encoding)
+    reader.skipElement()
+
+    // Throws exception because the reader is positioned at the end of container element
+    assertFailsWith<IllegalArgumentException> { TlvWriter().copyElement(reader) }
+  }
+
+  @Test
+  fun testCopyElement_replaceTag() {
+    val tag = CommonProfileTag(2, 1000u)
+    val encoding =
+      TlvWriter().startStructure(AnonymousTag).endStructure().validateTlv().getEncoded()
+    val expectedEncoding = TlvWriter().startStructure(tag).endStructure().validateTlv().getEncoded()
+
+    assertThat(TlvWriter().copyElement(tag, TlvReader(encoding)).validateTlv().getEncoded())
+      .isEqualTo(expectedEncoding)
+  }
+
+  @Test
+  fun testCopyElementUInt_replaceTag() {
+    val value = 42U
+    val tag1 = CommonProfileTag(2, 1u)
+    val tag2 = CommonProfileTag(2, 2u)
+    val encoding = TlvWriter().put(tag1, value).validateTlv().getEncoded()
+    val expectedEncoding = TlvWriter().put(tag2, value).validateTlv().getEncoded()
+
+    assertThat(TlvWriter().copyElement(tag2, TlvReader(encoding)).validateTlv().getEncoded())
+      .isEqualTo(expectedEncoding)
+  }
+
+  @Test
+  fun testTlvSampleData_copyElementsOneByOne() {
+    val reader = TlvReader(testTlvSampleData)
+    reader.skipElement()
+    val encoding =
+      TlvWriter()
+        .startStructure(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 1u))
+        .copyElement(reader)
+        .copyElement(reader)
+        .copyElement(reader)
+        .copyElement(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 5u), reader)
+        .copyElement(reader)
+        .copyElement(reader)
+        .endStructure()
+        .validateTlv()
+        .getEncoded()
+    assertThat(encoding).isEqualTo(testTlvSampleData)
+  }
+
   @Test
   fun testData_IntMinMax() {
     val encodedTlv =
@@ -378,7 +449,7 @@ class TlvReadWriteTest {
 
     // Throws exception because the encoded value has AnonymousTag tag
     assertFailsWith<IllegalArgumentException> {
-      TlvReader(encoding).getLong(FullyQualifiedTag(6, testVendorId, testProductId, 5u))
+      TlvReader(encoding).getLong(FullyQualifiedTag(6, TEST_VENDOR_ID, TEST_PRODUCT_ID, 5u))
     }
   }
 
@@ -820,6 +891,16 @@ class TlvReadWriteTest {
     }
   }
 
+  @Test
+  fun encodeAnonymousTagInStructure_throwsIllegalArgumentException() {
+    // Anonymous tag 1, Unsigned Integer, 1-octet value, {1 = 42U}
+    TlvWriter().apply {
+      startStructure(AnonymousTag)
+      // anonymous tags are not allowed within structure elements
+      assertFailsWith<IllegalArgumentException> { put(AnonymousTag, 42U) }
+    }
+  }
+
   @Test
   fun encodeContextTag_withinList() {
     // Context tag 1, Unsigned Integer, 1-octet value, [[1 = 42U]]
@@ -847,7 +928,7 @@ class TlvReadWriteTest {
     val value = 42U
     var tag = ContextSpecificTag(1)
 
-    // Array elements SHALL be of anonumous type
+    // Array elements SHALL be of anonymous type
     TlvWriter().apply {
       startArray(AnonymousTag)
       assertFailsWith<IllegalArgumentException> { put(tag, value) }
@@ -965,7 +1046,7 @@ class TlvReadWriteTest {
 
   @Test
   fun putSignedLongArray() {
-    // Anonumous Array of Signed Integers, [42, -17, -170000, 40000000000]
+    // Anonymous Array of Signed Integers, [42, -17, -170000, 40000000000]
     val values = longArrayOf(42, -17, -170000, 40000000000)
     val encoding = "16 00 2a 00 ef 02 f0 67 fd ff 03 00 90 2f 50 09 00 00 00 18".octetsToByteArray()
 
@@ -986,7 +1067,7 @@ class TlvReadWriteTest {
 
   @Test
   fun putUnsignedLongArray() {
-    // Anonumous Array of Signed Integers, [42, 170000, 40000000000]
+    // Anonymous Array of Signed Integers, [42, 170000, 40000000000]
     val values = longArrayOf(42, 170000, 40000000000)
     val encoding = "16 04 2a 06 10 98 02 00 07 00 90 2f 50 09 00 00 00 18".octetsToByteArray()