Github user markhamstra commented on a diff in the pull request: https://github.com/apache/spark/pull/993#discussion_r14846043 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/CodeGenerator.scala --- @@ -0,0 +1,421 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.spark.sql.catalyst.expressions.codegen + +import scala.language.existentials + +import org.apache.spark.Logging +import org.apache.spark.sql.catalyst.expressions +import org.apache.spark.sql.catalyst.expressions._ +import org.apache.spark.sql.catalyst.types._ + +/** + * A base class for generators of byte code that performs expression evaluation. Includes helpers + * for refering to Catalyst types and building trees that perform evaluation of individual + * expressions. + */ +abstract class CodeGenerator extends Logging { + import scala.reflect.runtime.{universe => ru} + import scala.reflect.runtime.universe._ + + import scala.tools.reflect.ToolBox + + val toolBox = runtimeMirror(getClass.getClassLoader).mkToolBox() + + val rowType = typeOf[Row] + val mutableRowType = typeOf[MutableRow] + val genericRowType = typeOf[GenericRow] + val genericMutableRowType = typeOf[GenericMutableRow] + + val projectionType = typeOf[Projection] + val mutableProjectionType = typeOf[MutableProjection] + + private val curId = new java.util.concurrent.atomic.AtomicInteger() + private val javaSeperator = "$" + + /** + * Returns a term name that is unique within this instance of a `CodeGenerator`. + * + * (Since we aren't in a macro context we do not seem to have access to the built in `freshName` + * function.) + */ + protected def freshName(prefix: String): TermName = { + newTermName(s"$prefix$javaSeperator${curId.getAndIncrement}") + } + + /** + * Scala ASTs for evaluating an [[Expression]] given a [[Row]] of input. + * + * @param code The sequence of statements required to evaluate the expression. + * @param nullTerm A term that holds a boolean value representing whether the expression evaluated + * to null. + * @param primitiveTerm A term for a possible primitive value of the result of the evaluation. Not + * valid if `nullTerm` is set to `false`. + * @param objectTerm An possibly boxed version of the result of evaluating this expression. --- End diff -- s/A/An
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