[GitHub] [incubator-daffodil] tuxji commented on a change in pull request #480: WIP: First cut at a Zip layer transform

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

tuxji commented on a change in pull request #480:
URL: https://github.com/apache/incubator-daffodil/pull/480#discussion_r563807688



##########
File path: daffodil-runtime1/src/main/scala/org/apache/daffodil/layers/ZipTransformer.scala
##########
@@ -0,0 +1,335 @@
+/*
+ * 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 org.apache.commons.compress.archivers.zip.ZipArchiveEntry
+import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream
+import org.apache.commons.compress.archivers.zip.ZipFile
+import org.apache.commons.compress.utils.SeekableInMemoryByteChannel
+import org.apache.commons.io.IOUtils

Review comment:
       For curiosity, I googled "best java zip library" and found some [alternatives](https://stackoverflow.com/questions/5362364/java-library-to-work-with-zip-files).  However, it looks like the Apache Compress library has multiple maintainers (not just one maintainer), supports nearly every feature of other zip libraries except encrypted zip files, documents its [interoperation](https://commons.apache.org/proper/commons-compress/zip.html) with other zip programs, and lists its known [limitations](https://commons.apache.org/proper/commons-compress/limitations.html) so it looks like the best choice (it also supports other compression formats too).

##########
File path: daffodil-runtime1/src/main/scala/org/apache/daffodil/layers/ZipTransformer.scala
##########
@@ -0,0 +1,335 @@
+/*
+ * 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 org.apache.commons.compress.archivers.zip.ZipArchiveEntry
+import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream
+import org.apache.commons.compress.archivers.zip.ZipFile
+import org.apache.commons.compress.utils.SeekableInMemoryByteChannel
+import org.apache.commons.io.IOUtils
+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.LayerLengthInBytesEv
+import org.apache.daffodil.processors.LayerBoundaryMarkEv
+import org.apache.daffodil.processors.LayerCharsetEv
+import org.apache.daffodil.processors.parsers.PState
+import org.apache.daffodil.processors.unparsers.UState
+import org.apache.daffodil.dsom.DPathCompileInfo
+import org.apache.daffodil.exceptions.Assert
+import org.apache.daffodil.io.ExplicitLengthLimitingStream
+
+import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
+import java.io.InputStream
+import java.io.OutputStream
+import java.io.SequenceInputStream
+import java.nio.charset.StandardCharsets
+import scala.Array.emptyByteArray
+import scala.collection.JavaConverters._
+
+/*
+ * Zip files require seeking to the end of the file. Hence, we need to have an explicit
+ * length for a zip layer to work from.
+ *
+ * When writing out zip file contents, to get the length, one must take the
+ * dfdl:contentLength of an enclosing element that surrounds the entire layer.
+ *
+ * All of this forces buffering. So there's no point in worrying about
+ * somehow avoiding buffering inside the implementation.
+ * That can simplify many things. There's no point, for example, in trying
+ * to not read and buffer all the entries.
+ *
+ */

Review comment:
       Please consider merging/rearranging the preceding and following comments.  I believe scaladoc will ignore the preceding comment right now.

##########
File path: daffodil-runtime1/src/main/scala/org/apache/daffodil/layers/ZipTransformer.scala
##########
@@ -0,0 +1,335 @@
+/*
+ * 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 org.apache.commons.compress.archivers.zip.ZipArchiveEntry
+import org.apache.commons.compress.archivers.zip.ZipArchiveOutputStream
+import org.apache.commons.compress.archivers.zip.ZipFile
+import org.apache.commons.compress.utils.SeekableInMemoryByteChannel
+import org.apache.commons.io.IOUtils
+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.LayerLengthInBytesEv
+import org.apache.daffodil.processors.LayerBoundaryMarkEv
+import org.apache.daffodil.processors.LayerCharsetEv
+import org.apache.daffodil.processors.parsers.PState
+import org.apache.daffodil.processors.unparsers.UState
+import org.apache.daffodil.dsom.DPathCompileInfo
+import org.apache.daffodil.exceptions.Assert
+import org.apache.daffodil.io.ExplicitLengthLimitingStream
+
+import java.io.ByteArrayInputStream
+import java.io.ByteArrayOutputStream
+import java.io.InputStream
+import java.io.OutputStream
+import java.io.SequenceInputStream
+import java.nio.charset.StandardCharsets
+import scala.Array.emptyByteArray
+import scala.collection.JavaConverters._
+
+/*
+ * Zip files require seeking to the end of the file. Hence, we need to have an explicit
+ * length for a zip layer to work from.
+ *
+ * When writing out zip file contents, to get the length, one must take the
+ * dfdl:contentLength of an enclosing element that surrounds the entire layer.
+ *
+ * All of this forces buffering. So there's no point in worrying about
+ * somehow avoiding buffering inside the implementation.
+ * That can simplify many things. There's no point, for example, in trying
+ * to not read and buffer all the entries.

Review comment:
       I agree.  The Apache Compress library works best with seekable byte channels passed to ZipFile (input) or ZipArchiveOutputStream (output).  I see you're using these seekable byte channels, which is good.  If we need to handle very large files, we could use disk files instead of in-memory buffers.




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