adds a dependency-free json printer based upon the otf decoder

Author: RichardWarburton

main/java/uk/co/real_logic/sbe/json/JsonPrinter.java

@@ -0,0 +1,99 @@
+/*
+ * Copyright 2015 Real Logic Ltd.
+ *
+ * Licensed 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 uk.co.real_logic.sbe.json;
+
+import uk.co.real_logic.agrona.concurrent.UnsafeBuffer;
+import uk.co.real_logic.sbe.ir.Ir;
+import uk.co.real_logic.sbe.ir.Token;
+import uk.co.real_logic.sbe.otf.OtfHeaderDecoder;
+import uk.co.real_logic.sbe.otf.OtfMessageDecoder;
+
+import java.nio.ByteBuffer;
+import java.util.List;
+
+/**
+ * .
+ */
+public class JsonPrinter {
+
+ private final Ir ir;
+
+ public JsonPrinter(final Ir ir)
+ {
+ this.ir = ir;
+ }
+
+ public void print(final ByteBuffer encodedMessage, final StringBuilder output)
+ {
+ // From the IR we can create OTF decoder for message headers.
+ final OtfHeaderDecoder headerDecoder = new OtfHeaderDecoder(ir.headerStructure());
+
+ // Now we have IR we can read the message header
+ int bufferOffset = 0;
+ final UnsafeBuffer buffer = new UnsafeBuffer(encodedMessage);
+
+ final int templateId = headerDecoder.getTemplateId(buffer, bufferOffset);
+ final int schemaId = headerDecoder.getSchemaId(buffer, bufferOffset);
+ final int actingVersion = headerDecoder.getSchemaVersion(buffer, bufferOffset);
+ final int blockLength = headerDecoder.getBlockLength(buffer, bufferOffset);
+
+ validateId(schemaId);
+ validateVersion(schemaId, actingVersion);
+
+ bufferOffset += headerDecoder.size();
+
+ final List<Token> msgTokens = ir.getMessage(templateId);
+
+ bufferOffset = OtfMessageDecoder.decode(
+ buffer,
+ bufferOffset,
+ actingVersion,
+ blockLength,
+ msgTokens,
+ new JsonTokenListener(output));
+
+ if (bufferOffset != encodedMessage.position())
+ {
+ throw new IllegalStateException("Message not fully decoded");
+ }
+ }
+
+ private void validateId(int schemaId)
+ {
+ if (schemaId != ir.id())
+ {
+ throw new IllegalArgumentException(
+ String.format("Required schema id %d but was actually %d", ir.id(), schemaId));
+ }
+ }
+
+ private void validateVersion(int schemaId, int actingVersion)
+ {
+ if (actingVersion > ir.version())
+ {
+ throw new IllegalArgumentException(
+ String.format("Required schema id %d but was actually %d", ir.id(), schemaId));
+ }
+ }
+
+ public String print(final ByteBuffer encodedMessage)
+ {
+ StringBuilder sb = new StringBuilder();
+ print(encodedMessage, sb);
+ return sb.toString();
+ }
+
+}