[GitHub] [iceberg] ggershinsky commented on a diff in pull request #6450: Core: Key metadata in Avro format

["ggershinsky (via GitHub)" <gi...@apache.org>]

ggershinsky commented on code in PR #6450:
URL: https://github.com/apache/iceberg/pull/6450#discussion_r1187202410


##########
core/src/main/java/org/apache/iceberg/encryption/KeyMetadataDecoder.java:
##########
@@ -0,0 +1,89 @@
+/*
+ * 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.iceberg.encryption;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.Map;
+import java.util.function.Function;
+import org.apache.avro.Schema;
+import org.apache.avro.io.DatumReader;
+import org.apache.avro.message.MessageDecoder;
+import org.apache.avro.message.MissingSchemaException;
+import org.apache.iceberg.avro.AvroSchemaUtil;
+import org.apache.iceberg.avro.GenericAvroReader;
+import org.apache.iceberg.data.avro.RawDecoder;
+import org.apache.iceberg.relocated.com.google.common.collect.MapMaker;
+
+public class KeyMetadataDecoder<D> extends MessageDecoder.BaseDecoder<D> {
+  private final org.apache.iceberg.Schema readSchema;
+  private final Map<Byte, RawDecoder<D>> decoders = new MapMaker().makeMap();
+
+  /**
+   * Creates a new decoder that constructs key metadata instances described by schema version.
+   *
+   * <p>The {@code readSchemaVersion} is as used the version of the expected (read) schema. Datum
+   * instances created by this class will are described by the expected schema.
+   */
+  public KeyMetadataDecoder(byte readSchemaVersion) {
+    this.readSchema = KeyMetadata.supportedSchemaVersions.get(readSchemaVersion);
+  }
+
+  @Override
+  public D decode(InputStream stream, D reuse) throws IOException {
+    byte writeSchemaVersion;
+
+    try {
+      writeSchemaVersion = (byte) stream.read();
+    } catch (IOException e) {
+      throw new IOException("Failed to read the version byte", e);
+    }
+
+    if (writeSchemaVersion < 0) {
+      throw new IOException("Version byte - end of stream reached");
+    }
+
+    org.apache.iceberg.Schema writeSchema =
+        KeyMetadata.supportedSchemaVersions.get(writeSchemaVersion);
+
+    if (writeSchema == null) {
+      throw new MissingSchemaException("Cannot resolve schema for version: " + writeSchemaVersion);
+    }
+
+    RawDecoder<D> decoder = decoders.get(writeSchemaVersion);
+
+    if (decoder == null) {
+      Function<Schema, DatumReader<?>> createReaderFunc =
+          schema -> {
+            GenericAvroReader<?> reader = GenericAvroReader.create(schema);
+            return reader;
+          };
+
+      decoder =
+          new RawDecoder<>(
+              readSchema,
+              createReaderFunc,
+              AvroSchemaUtil.convert(writeSchema, KeyMetadata.class.getCanonicalName()));
+
+      decoders.put(writeSchemaVersion, decoder);
+    }
+
+    return decoder.decode(stream, reuse);

Review Comment:
   the decoder.decode method doesn't throw an IOException



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