Restore exec files compatibility regarding Java 9 class files (#636)

3 files changed, 52 insertions, 12 deletions

diff --git a/org.jacoco.core/src/org/jacoco/core/analysis/Analyzer.java b/org.jacoco.core/src/org/jacoco/core/analysis/Analyzer.java
index 32384b86..5d1a9262 100644
--- a/org.jacoco.core/src/org/jacoco/core/analysis/Analyzer.java
+++ b/org.jacoco.core/src/org/jacoco/core/analysis/Analyzer.java
@@ -107,7 +107,7 @@ public class Analyzer {
 	 */
 	public void analyzeClass(final ClassReader reader) {
 		final ClassVisitor visitor = createAnalyzingVisitor(
-				CRC64.checksum(reader.b), reader.getClassName());
+				CRC64.classId(reader.b), reader.getClassName());
 		reader.accept(visitor, 0);
 	}
 
diff --git a/org.jacoco.core/src/org/jacoco/core/internal/data/CRC64.java b/org.jacoco.core/src/org/jacoco/core/internal/data/CRC64.java
index 64cb18ae..5094c709 100644
--- a/org.jacoco.core/src/org/jacoco/core/internal/data/CRC64.java
+++ b/org.jacoco.core/src/org/jacoco/core/internal/data/CRC64.java
@@ -11,6 +11,8 @@
  *******************************************************************************/
 package org.jacoco.core.internal.data;
 
+import org.objectweb.asm.Opcodes;
+
 /**
  * CRC64 checksum calculator based on the polynom specified in ISO 3309. The
  * implementation is based on the following publications:
@@ -42,21 +44,59 @@ public final class CRC64 {
 	}
 
 	/**
-	 * Calculates the CRC64 checksum for the given data array.
-	 * 
-	 * @param data
-	 *            data to calculate checksum for
-	 * @return checksum value
+	 * Updates given checksum by given byte.
+	 *
+	 * @param sum
+	 *            initial checksum value
+	 * @param b
+	 *            byte to update the checksum with
+	 * @return updated checksum value
+	 */
+	private static long update(final long sum, final byte b) {
+		final int lookupidx = ((int) sum ^ b) & 0xff;
+		return (sum >>> 8) ^ LOOKUPTABLE[lookupidx];
+	}
+
+	/**
+	 * Updates given checksum by bytes from given array.
+	 *
+	 * @param sum
+	 *            initial checksum value
+	 * @param bytes
+	 *            byte array to update the checksum with
+	 * @param fromIndexInclusive
+	 *            start index in array, inclusive
+	 * @param toIndexExclusive
+	 *            end index in array, exclusive
+	 * @return updated checksum value
 	 */
-	public static long checksum(final byte[] data) {
-		long sum = 0;
-		for (final byte b : data) {
-			final int lookupidx = ((int) sum ^ b) & 0xff;
-			sum = (sum >>> 8) ^ LOOKUPTABLE[lookupidx];
+	private static long update(long sum, final byte[] bytes,
+			final int fromIndexInclusive, final int toIndexExclusive) {
+		for (int i = fromIndexInclusive; i < toIndexExclusive; i++) {
+			sum = update(sum, bytes[i]);
 		}
 		return sum;
 	}
 
+	/**
+	 * Calculates class identifier for the given class bytes.
+	 *
+	 * @param bytes
+	 *            class bytes
+	 * @return class identifier
+	 */
+	public static long classId(final byte[] bytes) {
+		if (bytes.length > 7 && bytes[6] == 0x00 && bytes[7] == Opcodes.V9) {
+			// To support early versions of Java 9 we did a trick - change of
+			// Java 9 class files version on Java 8. Unfortunately this also
+			// affected class identifiers.
+			long sum = update(0, bytes, 0, 7);
+			sum = update(sum, (byte) Opcodes.V1_8);
+			return update(sum, bytes, 8, bytes.length);
+		}
+		return update(0, bytes, 0, bytes.length);
+	}
+
 	private CRC64() {
 	}
 
diff --git a/org.jacoco.core/src/org/jacoco/core/internal/instr/ProbeArrayStrategyFactory.java b/org.jacoco.core/src/org/jacoco/core/internal/instr/ProbeArrayStrategyFactory.java
index d5f4d49d..9ec2730b 100644
--- a/org.jacoco.core/src/org/jacoco/core/internal/instr/ProbeArrayStrategyFactory.java
+++ b/org.jacoco.core/src/org/jacoco/core/internal/instr/ProbeArrayStrategyFactory.java
@@ -42,7 +42,7 @@ public final class ProbeArrayStrategyFactory {
 
 		final String className = reader.getClassName();
 		final int version = getVersion(reader);
-		final long classId = CRC64.checksum(reader.b);
+		final long classId = CRC64.classId(reader.b);
 		final boolean withFrames = version >= Opcodes.V1_6;
 
 		if (isInterfaceOrModule(reader)) {