[GitHub] mbeckerle commented on a change in pull request #143: Support dfdl:length="prefixed"

[GitBox <gi...@apache.org>]

mbeckerle commented on a change in pull request #143: Support dfdl:length="prefixed"
URL: https://github.com/apache/incubator-daffodil/pull/143#discussion_r239885864
 
 

 ##########
 File path: daffodil-core/src/main/scala/org/apache/daffodil/grammar/ElementBaseGrammarMixin.scala
 ##########
 @@ -187,6 +200,79 @@ trait ElementBaseGrammarMixin
       minLen > 0)
   }
 
+  final lazy val prefixedLengthElementDecl: DetachedElementDecl = {
+    Assert.invariant(lengthKind == LengthKind.Prefixed)
+
+    // We need to resolve the global simple type of the prefix length type
+    // because we need to create a detached element with the same schema
+    // document/parent of the GSTD.
+    val prefixLengthTypeGSTD = schemaSet.getGlobalSimpleTypeDef(prefixLengthType).getOrElse(
+      schemaDefinitionError("Failed to resolve dfdl:prefixLengthType=\"%s\" to a simpleType", prefixLengthType.toQNameString)
+    )
+
+    val detachedNode = <element name={ name + " (prefixLength)" } type={ prefixLengthType.toQNameString } />.copy(scope = prefixLengthTypeGSTD.xml.scope)
+    val detachedElementDecl = new DetachedElementDecl(this, detachedNode, prefixLengthTypeGSTD.parent)
+
+    val prefixedLengthKind = detachedElementDecl.lengthKind
+    prefixedLengthKind match {
+      case LengthKind.Delimited | LengthKind.EndOfParent | LengthKind.Pattern =>
+        schemaDefinitionError("%s is specified as a dfdl:prefixLengthType, but has a dfdl:lengthKind of %s", prefixLengthType, prefixedLengthKind)
+      case LengthKind.Explicit if detachedElementDecl.optLengthConstant.isEmpty =>
+        schemaDefinitionError("%s is specified as a dfdl:prefixLengthType, but has an expression for dfdl:length", prefixLengthType)
+      case LengthKind.Implicit | LengthKind.Explicit if lengthUnits != detachedElementDecl.lengthUnits =>
+        schemaDefinitionError("%s is specified as a dfdl:prefixLengthType with dfdl:lengthKind %s, but has different dfdl:lengthUnits than the element", prefixLengthType, prefixedLengthKind)
+      case _ =>
+    }
+
+    schemaDefinitionUnless(detachedElementDecl.primType.isSubtypeOf(NodeInfo.Integer),
+      "%s is specified as a dfdl:prefixLengthType, but its type xs:%s is not a subtype of xs:integer", prefixLengthType, detachedElementDecl.primType.toString.toLowerCase)
+
+    schemaDefinitionWhen(detachedElementDecl.isOutputValueCalc,
+      "%s is specified as a dfdl:prefixLengthType, but specifies dfdl:outputValueCalc", prefixLengthType)
+    schemaDefinitionWhen(detachedElementDecl.hasInitiator,
+      "%s is specified as a dfdl:prefixLengthType, but specifies a dfdl:initiator", prefixLengthType)
+    schemaDefinitionWhen(detachedElementDecl.hasTerminator,
+      "%s is specified as a dfdl:prefixLengthType, but specifies a dfdl:terminator", prefixLengthType)
+    schemaDefinitionWhen(detachedElementDecl.alignment != 1,
+      "%s is specified as a dfdl:prefixLengthType, but specifies a dfdl:alignment other than 1", prefixLengthType)
+    schemaDefinitionWhen(detachedElementDecl.leadingSkip != 0,
+      "%s is specified as a dfdl:prefixLengthType, but specifies a dfdl:leadingSkip other than 0", prefixLengthType)
+    schemaDefinitionWhen(detachedElementDecl.trailingSkip != 0,
+      "%s is specified as a dfdl:prefixLengthType, but specifies a dfdl:trailingSkip other than 0", prefixLengthType)
+
+    if (detachedElementDecl.lengthKind == LengthKind.Prefixed &&
+        detachedElementDecl.prefixedLengthElementDecl.lengthKind == LengthKind.Prefixed) {
+        schemaDefinitionError("Nesting level for dfdl:prefixLengthType exceeds 1: %s > %s > %s > %s",
+          name, prefixLengthType,
+          detachedElementDecl.prefixLengthType,
+          detachedElementDecl.prefixedLengthElementDecl.prefixLengthType)
+    }
+
+    subset(detachedElementDecl.lengthKind != LengthKind.Prefixed, "Nested dfdl:lengthKind=\"prefixed\" is not supported.")
+
+    detachedElementDecl
+  }
+  final lazy val prefixedLengthAdjustmentInUnits: Long = prefixIncludesPrefixLength match {
 
 Review comment:
   So, is this requiring the length prefix itself to be constant length? I think this needs to be an Evaluatable ultimately, since the length prefix simple type isn't necessarily of known fixed length itself.  Seems like an obscure corner case, and it *should* be that, but I think there are formats where the prefix length is a variable-length text number delimited by something. 

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