stevedlawrence commented on a change in pull request #80: added a layer transform that swaps bytes within an array of 32 bit words URL: https://github.com/apache/incubator-daffodil/pull/80#discussion_r202689363
########## File path: daffodil-runtime1/src/main/scala/org/apache/daffodil/layers/ByteSwapTransformer.scala ########## @@ -0,0 +1,184 @@ +/* + * 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.daffodil.layers + +import java.io.OutputStream +import java.io.InputStream +import java.util.ArrayDeque +import java.util.Deque + +import org.apache.daffodil.exceptions.Assert +import org.apache.daffodil.schema.annotation.props.gen.LayerLengthKind +import org.apache.daffodil.schema.annotation.props.gen.LayerLengthUnits +import org.apache.daffodil.util.Maybe +import org.apache.daffodil.processors.TermRuntimeData +import org.apache.daffodil.processors.LayerLengthInBytesEv +import org.apache.daffodil.processors.LayerBoundaryMarkEv +import org.apache.daffodil.processors.LayerCharsetEv +import org.apache.daffodil.processors.parsers.PState +import org.apache.daffodil.io.ExplicitLengthLimitingStream +import org.apache.daffodil.processors.unparsers.UState + +class ByteSwapInputStream(wordsize: Int, jis: InputStream) + extends InputStream { + + object State extends org.apache.daffodil.util.Enum { + abstract sealed trait Type extends EnumValueType + + /** + * Buffering bytes in a word. + */ + case object Filling extends Type + + /** + * Return buffered bytes in a word in LIFO order. + */ + case object Emptying extends Type + + /** + * No more data. Drain buffered bytes. + */ + case object Draining extends Type + + /** + * No more data and no buffered bytes. + */ + case object Done extends Type + } + + private var c: Int = -2 + private val stack: Deque[Int] = new ArrayDeque[Int](wordsize) + private var state: State.Type = State.Filling + + /** + * Swap wordsize bytes at a time + * + */ + override def read(): Int = { + import State._ + if (state eq Done) return -1 + while (state != Done) { + state match { + case Filling => { + c = jis.read() + if (c == -1) { + state = Draining + } else { + stack.push(c) + if (stack.size() == wordsize) { + state = Emptying + } + } + } + case Emptying => { + if (stack.isEmpty()) { + state = Filling + } else { + c = stack.pop() + return c + } + } + case Draining => { + if (stack.isEmpty()) { + state = Done + return -1 + } else { + c = stack.pop() + return c + } + } + case Done => + Assert.invariantFailed("Done state not allowed.") + } + } + Assert.invariantFailed("No fall through to here.") + } +} + +class ByteSwapOutputStream(wordsize: Int, jos: OutputStream) + extends OutputStream { + + private val stack: Deque[Byte] = new ArrayDeque[Byte](wordsize) + private var closed = false + + override def close(): Unit = { + if (!closed) { + while (!stack.isEmpty()) { + jos.write(stack.pop()) + } + jos.close() + closed = true + } + } + + override def write(bInt: Int): Unit = { + Assert.usage(!closed) + stack.push(bInt.toByte) + if (stack.size() == wordsize) { + while(!stack.isEmpty()) { + jos.write(stack.pop()) + } + } + } +} + +class ByteSwapTransformer(wordsize: Int, layerLengthInBytesEv: LayerLengthInBytesEv) + extends LayerTransformer() { + + override def wrapLayerDecoder(jis: java.io.InputStream) = { + val s = new ByteSwapInputStream(wordsize, jis) + s + } + + override def wrapLimitingStream(jis: java.io.InputStream, state: PState) = { + val layerLengthInBytes: Int = layerLengthInBytesEv.evaluate(state).toInt + + val s = new ExplicitLengthLimitingStream(jis, layerLengthInBytes) + s + } + + override protected def wrapLayerEncoder(jos: java.io.OutputStream): java.io.OutputStream = { + val s = new ByteSwapOutputStream(wordsize, jos) + s + } + + override protected def wrapLimitingStream(jos: java.io.OutputStream, state: UState): java.io.OutputStream = { + jos // just return jos. The way the length will be used/stored is by way of + // taking the content length of the enclosing element. That will measure the + // length relative to the "ultimate" data output stream. + } +} + +sealed abstract class ByteSwapTransformerFactory(wordsize: Int, name: String) + extends LayerTransformerFactory(name) { + + override def newInstance(maybeLayerCharsetEv: Maybe[LayerCharsetEv], + maybeLayerLengthKind: Maybe[LayerLengthKind], + maybeLayerLengthInBytesEv: Maybe[LayerLengthInBytesEv], + maybeLayerLengthUnits: Maybe[LayerLengthUnits], + maybeLayerBoundaryMarkEv: Maybe[LayerBoundaryMarkEv], + trd: TermRuntimeData): LayerTransformer = { + + val xformer = new ByteSwapTransformer(wordsize, maybeLayerLengthInBytesEv.get) + xformer Review comment: It looks like this only supports layerLengthKind="explicit". Does it make sense to also implement implicit or boundarymark? If not, do we need to have schema definition checks to ensure the appropriate layer properties are provided? I don't see the checks for other transformers, so maybe we're missing those as well? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
