Implement memory-mapped ExecutionData class.

This allows apps to write coverage to disk during execution and not
require any flushing mechanism in order to collect coverage. The results
will be left in /data/misc/trace/jacoco-*.mm.ec and can be collected
later for coverage analysis. These .mm.ec files conform to the current
exec file format and can be loaded with the command-line tool.

Test: m -j EMMA_INSTRUMENT=true EMMA_INSTRUMENT_FRAMEWORK=true and
generate coverage report from /data/misc/trace
Bug: 147904124

Change-Id: If08492405b86a063ae714c259a2fb954bc5aa946

1 files changed, 324 insertions, 0 deletions

diff --git a/org.jacoco.core/src/org/jacoco/core/data/MappedExecutionData.java b/org.jacoco.core/src/org/jacoco/core/data/MappedExecutionData.java
new file mode 100644
index 00000000..39b90fb6
--- /dev/null
+++ b/org.jacoco.core/src/org/jacoco/core/data/MappedExecutionData.java
@@ -0,0 +1,324 @@
+// BEGIN android-change
+package org.jacoco.core.data;
+
+import static java.lang.String.format;
+
+import java.io.File;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.channels.FileChannel;
+import java.nio.channels.FileLock;
+import java.nio.charset.Charset;
+import java.nio.ByteBuffer;
+import java.nio.MappedByteBuffer;
+
+import org.jacoco.core.data.ExecutionDataWriter;
+
+/**
+ * Memory-mapped execution data implementation.
+ *
+ * Stores the probe data in a section of a memory-mapped file, so that it will be available without
+ * requiring a flush of the coverage data.
+ */
+public final class MappedExecutionData implements IExecutionData {
+
+	private static FileChannel CHANNEL;
+
+	private final long id;
+	private final String name;
+	private final int probeCount;
+
+	// Stores the memory-mapped byte buffer containing the probe data, packed as bits.
+	private MappedByteBuffer probeBuffer;
+
+	/**
+	 * Creates the mapped execution data.
+	 */
+	public MappedExecutionData(final long id, final String name, final int probeCount)
+			throws IOException {
+		this.id = id;
+		this.name = name;
+		this.probeCount = probeCount;
+
+		createMemoryMappedProbeArray(id, name, probeCount);
+	}
+
+	/**
+	 * Maps a section of the already-opened file for the probe data.
+	 *
+	 * @param id  the class id
+	 * @param name  the VM class name
+	 * @param probeCount  the number of probes for this class
+	 */
+	private void createMemoryMappedProbeArray(
+		final long id, final String name, final int probeCount) throws IOException {
+		// TODO: Figure out a more portable way to do this. Currently needed to avoid
+		// cross-VM race conditions when writing/mapping the file.  Since most processes
+		// are forked from zygote, they will initially share the same output file, but
+		// without synchronization across VMs, this can cause simultaneous maps/writes from
+		// different VMs to interrupt each other, resulting in malformed execution data.
+		// Adding file locks did not resolve this issue. Note that only new classes that
+		// were loaded after the fork will end up in the new file. Classes that were
+		// already loaded will end up in the original output file for the pre-forked
+		// process, which is OK.
+		if (CHANNEL == null) {
+			throw new IOException("Memory mapped file was not initialized.");
+		}
+
+		synchronized (CHANNEL) {
+			int byteCount = (probeCount + 7) / 8;
+
+			// Write the ExecutionData block info.
+			ByteBuffer execDataBuffer = ByteBuffer.allocate(11);
+			execDataBuffer.put(ExecutionDataWriter.BLOCK_EXECUTIONDATA);
+			execDataBuffer.putLong(id);
+			execDataBuffer.putShort((short) name.length());
+			execDataBuffer.flip();
+			CHANNEL.write(execDataBuffer);
+			CHANNEL.write(ByteBuffer.wrap(name.getBytes(Charset.forName("UTF-8"))));
+
+			// Write the probe info and map part of this file for the probe data.
+			CHANNEL.write(toVarIntByteBuffer(probeCount));
+			probeBuffer = CHANNEL.map(FileChannel.MapMode.READ_WRITE, CHANNEL.position(), byteCount);
+			CHANNEL.position(CHANNEL.position() + byteCount);
+		}
+	}
+
+	/**
+	 * Creates the output file that will be mapped for probe data.
+	 */
+	public static void prepareFile(int pid) throws IOException {
+		// Write header information to the file.
+		ByteBuffer headerBuffer = ByteBuffer.allocate(5);
+		headerBuffer.put(ExecutionDataWriter.BLOCK_HEADER);
+		headerBuffer.putChar(ExecutionDataWriter.MAGIC_NUMBER);
+		headerBuffer.putChar(ExecutionDataWriter.FORMAT_VERSION);
+		headerBuffer.flip();
+
+		// If this file already exists (due to pid re-usage), the previous coverage data
+		// will be lost when the file is overwritten.
+		File outputFile = new File("/data/misc/trace/jacoco-" + pid + ".mm.ec");
+		CHANNEL = new RandomAccessFile(outputFile, "rw").getChannel();
+		synchronized (CHANNEL) {
+			CHANNEL.write(headerBuffer);
+		}
+	}
+
+	/**
+	 * Writes a variable-length int to a {@link ByteBuffer}.
+	 *
+	 * @param value  the value to write
+	 * @return a ByteBuffer that can be used to write to a FileChannel containing the value
+	 */
+	private ByteBuffer toVarIntByteBuffer(int value) {
+		ByteBuffer buffer = ByteBuffer.allocate(5);
+		if (value == 0) {
+			buffer.put((byte) 0);
+		} else {
+			while (value > 0) {
+				if ((value & 0xFFFFFF80) == 0) {
+					buffer.put((byte) value);
+				} else {
+					buffer.put((byte) (0x80 | (value & 0x7F)));
+				}
+				value >>>= 7;
+			}
+		}
+		buffer.flip();
+		return buffer;
+	}
+
+	/**
+	 * Return the unique identifier for this class. The identifier is the CRC64
+	 * checksum of the raw class file definition.
+	 *
+	 * @return class identifier
+	 */
+	public long getId() {
+		return id;
+	}
+
+	/**
+	 * The VM name of the class.
+	 *
+	 * @return VM name
+	 */
+	public String getName() {
+		return name;
+	}
+
+	/**
+	 * The number of instrumentation probes for this class.
+	 *
+	 * @return number of probes
+	 */
+	public int getProbeCount() {
+		return probeCount;
+	}
+
+	/**
+	 * Returns a copy of the probe data as a boolean array.
+	 *
+	 * Changes to the returned array will not be reflected in the execution data.
+	 *
+	 * @return copy of the probe data
+	 */
+	public boolean[] getProbesCopy() {
+		final int bytes = (probeCount + 7) / 8;
+		boolean[] probes = new boolean[probeCount];
+		for (int index = 0; index < probeCount; index += 8) {
+			byte byteProbe = probeBuffer.get(index / 8);
+			for (int bit = 0; (bit < 8) && ((index + bit) < probeCount); bit++) {
+				probes[index + bit] = ((byteProbe & 0x1) > 0);
+				byteProbe >>>= 1;
+			}
+		}
+		return probes;
+	}
+
+	/**
+	 * Sets all probes to <code>false</code>.
+	 */
+	public void reset() {
+		final int bytes = (probeCount + 7) / 8;
+		synchronized (probeBuffer) {
+			for (int i = 0; i < bytes; i++) {
+				probeBuffer.put(i, (byte) 0);
+			}
+		}
+	}
+
+	/**
+	 * Checks whether any probe has been hit.
+	 *
+	 * @return <code>true</code>, if at least one probe has been hit
+	 */
+	public boolean hasHits() {
+		final int bytes = (probeCount + 7) / 8;
+		synchronized (probeBuffer) {
+			for (int i = 0; i < bytes; i++) {
+				if (probeBuffer.get(i) > 0) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Merges the given execution data into the probe data of this object. I.e.
+	 * a probe entry in this object is marked as executed (<code>true</code>) if
+	 * this probe or the corresponding other probe was executed. So the result
+	 * is
+	 *
+	 * <pre>
+	 * A or B
+	 * </pre>
+	 *
+	 * The probe array of the other object is not modified.
+	 *
+	 * @param other
+	 *            execution data to merge
+	 */
+	public void merge(final IExecutionData other) {
+		merge(other, true);
+	}
+
+	/**
+	 * Merges the given execution data into the probe data of this object. A
+	 * probe in this object is set to the value of <code>flag</code> if the
+	 * corresponding other probe was executed. For <code>flag==true</code> this
+	 * corresponds to
+	 *
+	 * <pre>
+	 * A or B
+	 * </pre>
+	 *
+	 * For <code>flag==false</code> this can be considered as a subtraction
+	 *
+	 * <pre>
+	 * A and not B
+	 * </pre>
+	 *
+	 * The probe array of the other object is not modified.
+	 *
+	 * @param other
+	 *            execution data to merge
+	 * @param flag
+	 *            merge mode
+	 */
+	public void merge(final IExecutionData other, final boolean flag) {
+		synchronized (probeBuffer) {
+			for (int i = 0; i < probeCount; i++) {
+				if (other.getProbe(i)) {
+					setProbe(i);
+				}
+			}
+		}
+	}
+
+	/**
+	 * Asserts that this execution data object is compatible with the given
+	 * parameters. The purpose of this check is to detect a very unlikely class
+	 * id collision.
+	 *
+	 * @param id
+	 *            other class id, must be the same
+	 * @param name
+	 *            other name, must be equal to this name
+	 * @param probecount
+	 *            probe data length, must be the same as for this data
+	 * @throws IllegalStateException
+	 *             if the given parameters do not match this instance
+	 */
+	public void assertCompatibility(final long id, final String name, final int probeCount)
+		throws IllegalStateException {
+		if (this.id != id) {
+			throw new IllegalStateException(format(
+					"Different ids (%016x and %016x).", Long.valueOf(this.id),
+					Long.valueOf(id)));
+		}
+		if (!this.name.equals(name)) {
+			throw new IllegalStateException(format(
+					"Different class names %s and %s for id %016x.", this.name,
+					name, Long.valueOf(id)));
+		}
+		if (this.probeCount != probeCount) {
+			throw new IllegalStateException(format(
+					"Incompatible execution data for class %s with id %016x.",
+					name, Long.valueOf(id)));
+		}
+	}
+
+	/**
+	 * Returns the execution data probe for a given index. A value of
+	 * <code>true</code> indicates that the corresponding probe was
+	 * executed.
+	 *
+	 * @param index  the probe's index to look up
+	 *
+	 * @return probe data
+	 */
+	public boolean getProbe(final int index) {
+		int offset = index / 8;
+		int bit = 1 << (index % 8);
+		return (probeBuffer.get(offset) & bit) != 0;
+	}
+
+	/**
+	 * Sets the execution data probe at the given index to <code>true</code>.
+	 *
+	 * @param index  the probe's index to set
+	 */
+	public void setProbe(final int index) {
+		int offset = index / 8;
+		int bit = 1 << (index % 8);
+		byte currentValue = probeBuffer.get(offset);
+		if ((currentValue & bit) == 0) {
+			synchronized (probeBuffer) {
+				probeBuffer.put(offset, (byte) (probeBuffer.get(offset) | bit));
+			}
+		}
+	}
+}
+// END android-change