add concept of data items for modelling

codyze-backends/cpg/src/main/kotlin/de/fraunhofer/aisec/codyze/backends/cpg/coko/dsl/DataItemCpgDsl.kt

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+package de.fraunhofer.aisec.codyze.backends.cpg.coko.dsl
+
+import de.fraunhofer.aisec.codyze.backends.cpg.coko.Nodes
+import de.fraunhofer.aisec.codyze.specificationLanguages.coko.core.CokoBackend
+import de.fraunhofer.aisec.codyze.specificationLanguages.coko.core.modelling.DataItem
+import de.fraunhofer.aisec.codyze.specificationLanguages.coko.core.modelling.ReturnValueItem
+import de.fraunhofer.aisec.codyze.specificationLanguages.coko.core.modelling.Value
+import de.fraunhofer.aisec.cpg.graph.Node
+import de.fraunhofer.aisec.cpg.graph.declarations.VariableDeclaration
+import de.fraunhofer.aisec.cpg.graph.evaluate
+import de.fraunhofer.aisec.cpg.graph.literals
+import de.fraunhofer.aisec.cpg.graph.statements.expressions.DeclaredReferenceExpression
+import de.fraunhofer.aisec.cpg.graph.variables
+
+/**
+ * Get all [Nodes] that are associated with this [DataItem].
+ */
+context(CokoBackend)
+fun DataItem.cpgGetAllNodes(): Nodes =
+    when (this@DataItem) {
+        is ReturnValueItem -> op.cpgGetAllNodes().flatMap { it.getVariableInNextDFGOrThis() }
+        is Value -> this@DataItem.getNodes()
+    }
+
+/**
+ * Get all [Nodes] that are associated with this [DataItem].
+ */
+context(CokoBackend)
+fun DataItem.cpgGetNodes(): Nodes {
+    return when (this@DataItem) {
+        is ReturnValueItem -> op.cpgGetNodes().flatMap { it.getVariableInNextDFGOrThis() }
+        is Value -> this@DataItem.getNodes()
+    }
+}
+
+context(CokoBackend)
+private fun Value.getNodes(): Nodes =
+    cpg.literals.filter {
+            node ->
+        node.value == this.value
+    } + cpg.variables.filter {
+            node ->
+        node.evaluate() == this.value
+    }
+
+/**
+ * Returns all [VariableDeclaration]s and [DeclaredReferenceExpression]s that have a DFG edge from [this].
+ * If there are none, returns [this].
+ */
+private fun Node.getVariableInNextDFGOrThis(): Nodes =
+    this.nextDFG
+        .filter {
+                next ->
+            next is DeclaredReferenceExpression || next is VariableDeclaration
+        }.ifEmpty { listOf(this) }

codyze-specification-languages/coko/coko-core/src/main/kotlin/de/fraunhofer/aisec/codyze/specificationLanguages/coko/core/modelling/DataItem.kt

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+package de.fraunhofer.aisec.codyze.specificationLanguages.coko.core.modelling
+
+import de.fraunhofer.aisec.codyze.specificationLanguages.coko.core.dsl.Op
+
+sealed interface DataItem
+
+data class ReturnValueItem(val op: Op) : DataItem {
+    override fun toString(): String = "Return value of $op"
+}
+
+data class Value(val value: Any) : DataItem
+