mbeckerle commented on a change in pull request #88: Daffodil 1919 separators
URL: https://github.com/apache/incubator-daffodil/pull/88#discussion_r206577258
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File path:
daffodil-runtime1-unparser/src/main/scala/org/apache/daffodil/processors/unparsers/ZeroLengthDetector.scala
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@@ -0,0 +1,134 @@
+package org.apache.daffodil.processors.unparsers
+
+import org.apache.daffodil.infoset.DIElement
+import org.apache.daffodil.exceptions.Assert
+import org.apache.daffodil.infoset.DISimple
+import org.apache.daffodil.dpath.NodeInfo
+
+/**
+ * Rapidly determines if an Infoset Element will have zero length when
unparsed.
+ *
+ * This is required for proper separator suppression in sequence unparsers.
+ *
+ * The specific concrete sub-class is selected based on a compile time analysis
+ * of whether the element can have zero length at all, and if so, under
+ * what conditions.
+ */
+sealed trait ZeroLengthDetector
+ extends Serializable {
+ def isZeroLength(diElement: DIElement): Boolean
+}
+
+/**
+ * Applies to both simple and complex types that are nillable.
+ */
+sealed trait NillableZeroLengthMixin { self: ZeroLengthDetector =>
+ protected def isNillableZeroLength(diElement: DIElement): Boolean = {
+ Assert.invariant(diElement.erd.isNillable)
+ diElement.isNilled
+ }
+}
+/**
+ * Use when the characteristics of the nil representation are such that
+ * unparsing a nilled element will result in zero length.
+ */
+class NillableZeroLengthDetector
+ extends ZeroLengthDetector
+ with NillableZeroLengthMixin {
+ override def isZeroLength(diElement: DIElement) =
isNillableZeroLength(diElement)
+}
+
+sealed trait StringZeroLengthMixin { self: ZeroLengthDetector =>
+ protected def isStringZeroLength(diElement: DIElement): Boolean = {
+ val opt = diElement.erd.optPrimType
+ Assert.invariant(opt.isDefined & (opt.get eq NodeInfo.String))
+ val result =
+ if (diElement.isNilled)
+ false // must not be zero length nil. If it was zero length nil, we
wouldn't be at this code.
+ else {
+ diElement match {
+ case st: DISimple => {
+ Assert.invariant(st.hasValue)
+ val str = st.dataValueAsString
+ val len = str.length()
+ len == 0
+ }
+ case _ => Assert.invariantFailed("Not a simple type")
+ }
+ }
+ result
+ }
+}
+
+/**
+ * Use when the element is of simple type string, not nillable.
+ */
+class StringZeroLengthDetector
+ extends ZeroLengthDetector
+ with StringZeroLengthMixin {
+ override def isZeroLength(diElement: DIElement) =
isStringZeroLength(diElement)
+
+}
+
+sealed trait HexBinaryZeroLengthMixin { self: ZeroLengthDetector =>
+ protected def isHexBinaryZeroLength(diElement: DIElement): Boolean = {
+ val opt = diElement.erd.optPrimType
+ Assert.invariant(opt.isDefined & (opt.get eq NodeInfo.HexBinary))
+ val result =
+ if (diElement.isNilled)
+ false // must not be zero length nil. If it was zero length nil, we
wouldn't be at this code.
+ else {
+ diElement match {
+ case st: DISimple => {
+ Assert.invariant(st.hasValue)
+ val arr = st.dataValue.asInstanceOf[Array[Byte]]
+ val len = arr.length
+ len == 0
+ }
+ case _ => Assert.invariantFailed("Not a simple type")
+ }
+ }
+ result
+ }
+}
+
+/**
+ * Use when the element is of simple type hexBinary, not nillable.
+ */
+class HexBinaryZeroLengthDetector
+ extends ZeroLengthDetector
+ with HexBinaryZeroLengthMixin {
+ override def isZeroLength(diElement: DIElement) =
isHexBinaryZeroLength(diElement)
+}
+
+/**
+ * Use when analysis shows the element can never be zero length.
+ */
+class NeverZeroLengthDetector
+ extends ZeroLengthDetector {
+ override def isZeroLength(diElement: DIElement) = false
+}
+
+/**
+ * Use for nillable strings when they can be zero length two different ways.
+ */
+class NillableStringZeroLengthDetector
Review comment:
Test coverage. There need to be tests that exercise these combination
detectors.
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