Implementation of sbeSkip and sbeDecodedLength for the Java Generator.

sbe-tool/src/main/java/uk/co/real_logic/sbe/generation/java/JavaGenerator.java

@@ -31,6 +31,8 @@
 import java.util.function.Function;
 
 import static uk.co.real_logic.sbe.SbeTool.JAVA_INTERFACE_PACKAGE;
+import static uk.co.real_logic.sbe.generation.cpp.CppUtil.formatClassName;
+import static uk.co.real_logic.sbe.generation.cpp.CppUtil.formatPropertyName;
 import static uk.co.real_logic.sbe.generation.java.JavaGenerator.CodecType.DECODER;
 import static uk.co.real_logic.sbe.generation.java.JavaGenerator.CodecType.ENCODER;
 import static uk.co.real_logic.sbe.generation.java.JavaUtil.*;
@@ -233,6 +235,7 @@ private void generateDecoder(
             generateDecoderVarData(sb, varData, BASE_INDENT);
 
             generateDecoderDisplay(sb, msgToken.name(), fields, groups, varData);
+            generateMessageLength(sb, className, true, groups, varData, BASE_INDENT);
 
             out.append(sb);
             out.append("}\n");
@@ -284,6 +287,7 @@ private void generateDecoderGroups(
             generateDecoderVarData(sb, varData, indent + INDENT);
 
             appendGroupInstanceDecoderDisplay(sb, fields, groups, varData, indent + INDENT);
+            generateMessageLength(sb, groupName, false, groups, varData, indent + INDENT);
 
             sb.append(indent).append("    }\n");
         }
@@ -2579,6 +2583,15 @@ private CharSequence generateDecoderFlyweightCode(final String className, final
             "    public " + className + " sbeRewind()\n" +
             "    {\n" +
             "        return wrap(buffer, initialOffset, actingBlockLength, actingVersion);\n" +
+            "    }\n\n" +
+
+            "    public int sbeDecodedLength()\n" +
+            "    {\n" +
+            "        final int currentLimit = limit();\n" +
+            "        sbeSkip();\n" +
+            "        final int decodedLength = encodedLength();\n" +
+            "        limit(currentLimit);\n" +
+            "        return decodedLength;\n" +
             "    }\n\n";
 
         return generateFlyweightCode(DECODER, className, token, methods, readOnlyBuffer);
@@ -3655,6 +3668,64 @@ private void appendMessageToString(final StringBuilder sb, final String decoderN
         append(sb, INDENT, "}");
     }
 
+    private void generateMessageLength(
+        final StringBuilder sb,
+        final String className,
+        final boolean isParent,
+        final List<Token> groups,
+        final List<Token> varData,
+        final String baseIndent)
+    {
+        final String methodIndent = baseIndent + INDENT;
+        final String bodyIndent = methodIndent + INDENT;
+        append(sb, methodIndent, "");
+        append(sb, methodIndent, "public " + className + " sbeSkip()");
+        append(sb, methodIndent, "{");
+        if (isParent)
+        {
+            append(sb, bodyIndent, "sbeRewind();");
+        }
+        for (int i = 0, size = groups.size(); i < size; i++)
+        {
+            final Token groupToken = groups.get(i);
+            if (groupToken.signal() != Signal.BEGIN_GROUP)
+            {
+                throw new IllegalStateException("tokens must begin with BEGIN_GROUP: token=" + groupToken);
+            }
+
+            final String groupName = formatPropertyName(groupToken.name());
+            final String groupDecoderName = decoderName(groupToken.name());
+
+            append(sb, bodyIndent, groupDecoderName + " " + groupName + " = " + groupName + "();");
+            append(sb, bodyIndent, "if (" + groupName + ".count() > 0)");
+            append(sb, bodyIndent, "{");
+            append(sb, bodyIndent, "    while (" + groupName + ".hasNext())");
+            append(sb, bodyIndent, "    {");
+            append(sb, bodyIndent, "        " + groupName + ".next();");
+            append(sb, bodyIndent, "        " + groupName + ".sbeSkip();");
+            append(sb, bodyIndent, "    }");
+            append(sb, bodyIndent, "}");
+            i = findEndSignal(groups, i, Signal.END_GROUP, groupToken.name());
+        }
+
+        for (int i = 0, size = varData.size(); i < size;)
+        {
+            final Token varDataToken = varData.get(i);
+            if (varDataToken.signal() != Signal.BEGIN_VAR_DATA)
+            {
+                throw new IllegalStateException("tokens must begin with BEGIN_VAR_DATA: token=" + varDataToken);
+            }
+
+            final String varDataName = formatPropertyName(varDataToken.name());
+            append(sb, bodyIndent, "skip" + Generators.toUpperFirstChar(varDataName) + "();");
+
+            i += varDataToken.componentTokenCount();
+        }
+
+        append(sb, bodyIndent, "return this;");
+        append(sb, methodIndent, "}");
+    }
+
     private static String validateBufferImplementation(
         final String fullyQualifiedBufferImplementation, final Class<?> bufferClass)
     {

sbe-tool/src/main/java/uk/co/real_logic/sbe/ir/generated/FrameCodecDecoder.java

@@ -109,6 +109,15 @@ public FrameCodecDecoder sbeRewind()
         return wrap(buffer, initialOffset, actingBlockLength, actingVersion);
     }
 
+    public int sbeDecodedLength()
+    {
+        final int currentLimit = limit();
+        sbeSkip();
+        final int decodedLength = encodedLength();
+        limit(currentLimit);
+        return decodedLength;
+    }
+
     public int encodedLength()
     {
         return limit - offset;
@@ -664,4 +673,13 @@ public StringBuilder appendTo(final StringBuilder builder)
 
         return builder;
     }
+
+    public FrameCodecDecoder sbeSkip()
+    {
+        sbeRewind();
+        skipPackageName();
+        skipNamespaceName();
+        skipSemanticVersion();
+        return this;
+    }
 }

sbe-tool/src/main/java/uk/co/real_logic/sbe/ir/generated/TokenCodecDecoder.java

@@ -109,6 +109,15 @@ public TokenCodecDecoder sbeRewind()
         return wrap(buffer, initialOffset, actingBlockLength, actingVersion);
     }
 
+    public int sbeDecodedLength()
+    {
+        final int currentLimit = limit();
+        sbeSkip();
+        final int decodedLength = encodedLength();
+        limit(currentLimit);
+        return decodedLength;
+    }
+
     public int encodedLength()
     {
         return limit - offset;
@@ -1890,4 +1899,21 @@ public StringBuilder appendTo(final StringBuilder builder)
 
         return builder;
     }
+
+    public TokenCodecDecoder sbeSkip()
+    {
+        sbeRewind();
+        skipName();
+        skipConstValue();
+        skipMinValue();
+        skipMaxValue();
+        skipNullValue();
+        skipCharacterEncoding();
+        skipEpoch();
+        skipTimeUnit();
+        skipSemanticType();
+        skipDescription();
+        skipReferencedName();
+        return this;
+    }
 }

sbe-tool/src/test/java/uk/co/real_logic/sbe/generation/java/CarDecodeTestUtil.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2013-2021 Real Logic Limited.
+ *
+ * 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
+ *
+ * https://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.generation.java;
+
+import baseline.CarDecoder;
+import baseline.EngineDecoder;
+import baseline.OptionalExtrasDecoder;
+
+import java.util.ArrayList;
+
+public class CarDecodeTestUtil
+{
+    static ArrayList<Object> getValues(final CarDecoder carDecoder)
+    {
+        final ArrayList<Object> values = new ArrayList<>();
+
+        values.add(carDecoder.serialNumber());
+        values.add(carDecoder.modelYear());
+        values.add(carDecoder.available());
+        values.add(carDecoder.code());
+        values.add(CarDecoder.someNumbersLength());
+        for (int i = 0, n = CarDecoder.someNumbersLength(); i < n; i++)
+        {
+            values.add(carDecoder.someNumbers(i));
+        }
+        values.add(carDecoder.vehicleCode());
+        final OptionalExtrasDecoder extras = carDecoder.extras();
+        values.add(extras.sunRoof());
+        values.add(extras.sportsPack());
+        values.add(extras.cruiseControl());
+        final EngineDecoder engine = carDecoder.engine();
+        values.add(engine.capacity());
+        values.add(engine.numCylinders());
+        values.add(engine.maxRpm());
+        values.add(engine.manufacturerCode());
+        values.add(engine.fuel());
+        final CarDecoder.FuelFiguresDecoder fuelFigures = carDecoder.fuelFigures();
+        while (fuelFigures.hasNext())
+        {
+            fuelFigures.next();
+            values.add(fuelFigures.speed());
+            values.add(fuelFigures.mpg());
+        }
+        final CarDecoder.PerformanceFiguresDecoder performanceFigures = carDecoder.performanceFigures();
+        while (performanceFigures.hasNext())
+        {
+            performanceFigures.next();
+            values.add(performanceFigures.octaneRating());
+            final CarDecoder.PerformanceFiguresDecoder.AccelerationDecoder acceleration =
+                performanceFigures.acceleration();
+            while (acceleration.hasNext())
+            {
+                acceleration.next();
+                values.add(acceleration.mph());
+                values.add(acceleration.seconds());
+            }
+        }
+        values.add(carDecoder.manufacturer());
+        values.add(carDecoder.model());
+        values.add(carDecoder.activationCode());
+        return values;
+    }
+
+    static ArrayList<Object> getPartialValues(final CarDecoder carDecoder)
+    {
+        final ArrayList<Object> values = new ArrayList<>();
+
+        values.add(carDecoder.serialNumber());
+        values.add(carDecoder.modelYear());
+        values.add(carDecoder.available());
+        values.add(carDecoder.code());
+        values.add(CarDecoder.someNumbersLength());
+        for (int i = 0, n = CarDecoder.someNumbersLength(); i < n; i++)
+        {
+            values.add(carDecoder.someNumbers(i));
+        }
+        values.add(carDecoder.vehicleCode());
+        final OptionalExtrasDecoder extras = carDecoder.extras();
+        values.add(extras.sunRoof());
+        values.add(extras.sportsPack());
+        values.add(extras.cruiseControl());
+        final EngineDecoder engine = carDecoder.engine();
+        values.add(engine.capacity());
+        values.add(engine.numCylinders());
+        values.add(engine.maxRpm());
+        values.add(engine.manufacturerCode());
+        values.add(engine.fuel());
+        final CarDecoder.FuelFiguresDecoder fuelFigures = carDecoder.fuelFigures();
+        while (fuelFigures.hasNext())
+        {
+            fuelFigures.next();
+            values.add(fuelFigures.speed());
+            values.add(fuelFigures.mpg());
+        }
+        final CarDecoder.PerformanceFiguresDecoder performanceFigures = carDecoder.performanceFigures();
+
+        // Stop decoding part way through the message.
+        if (performanceFigures.hasNext())
+        {
+            performanceFigures.next();
+            values.add(performanceFigures.octaneRating());
+            final CarDecoder.PerformanceFiguresDecoder.AccelerationDecoder acceleration =
+                performanceFigures.acceleration();
+            if (acceleration.hasNext())
+            {
+                acceleration.next();
+                values.add(acceleration.mph());
+            }
+        }
+
+        return values;
+    }
+}