--- /dev/null
+/*
+ * SPDX-License-Identifier: LGPL-2.1-only
+ *
+ * Copyright (C) 2016 EfficiOS Inc.
+ * Copyright (C) 2016 Alexandre Montplaisir <alexmonthy@efficios.com>
+ */
+
+package org.lttng.ust.agent.context;
+
+import java.io.ByteArrayOutputStream;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+import java.nio.charset.Charset;
+import java.util.Collection;
+import java.util.Map;
+
+import org.lttng.ust.agent.utils.LttngUstAgentLogger;
+
+/**
+ * This class is used to serialize the list of "context info" objects to pass
+ * through JNI.
+ *
+ * The protocol expects two byte array parameters, which are contained here in
+ * the {@link SerializedContexts} inner class.
+ *
+ * The first byte array is called the "entries array", and contains fixed-size
+ * entries, one per context element.
+ *
+ * The second one is the "strings array", it is of variable length and used to
+ * hold the variable-length strings. Each one of these strings is formatted as a
+ * UTF-8 C-string, meaning in will end with a "\0" byte to indicate its end.
+ * Entries in the first array may refer to offsets in the second array to point
+ * to relevant strings.
+ *
+ * The fixed-size entries in the entries array contain the following elements
+ * (size in bytes in parentheses):
+ *
+ * <ul>
+ * <li>The offset in the strings array pointing to the full context name, like
+ * "$app.myprovider:mycontext" (4)</li>
+ * <li>The context value type (1)</li>
+ * <li>The context value itself (8)</li>
+ * </ul>
+ *
+ * The context value type will indicate how many bytes are used for the value.
+ * If the it is of String type, then we use 4 bytes to represent the offset in
+ * the strings array.
+ *
+ * So the total size of each entry is 13 bytes. All unused bytes (for context
+ * values shorter than 8 bytes for example) will be zero'ed.
+ *
+ * @author Alexandre Montplaisir
+ */
+public class ContextInfoSerializer {
+
+ private enum DataType {
+ NULL(0),
+ INTEGER(1),
+ LONG(2),
+ DOUBLE(3),
+ FLOAT(4),
+ BYTE(5),
+ SHORT(6),
+ BOOLEAN(7),
+ STRING(8);
+
+ private final byte value;
+
+ private DataType(int value) {
+ this.value = (byte) value;
+ }
+
+ public byte getValue() {
+ return value;
+ }
+ }
+
+ /**
+ * Class used to wrap the two byte arrays returned by
+ * {@link #queryAndSerializeRequestedContexts}.
+ */
+ public static class SerializedContexts {
+
+ private final byte[] contextEntries;
+ private final byte[] contextStrings;
+
+ /**
+ * Constructor
+ *
+ * @param entries
+ * Arrays for the fixed-size context entries.
+ * @param strings
+ * Arrays for variable-length strings
+ */
+ public SerializedContexts(byte[] entries, byte[] strings) {
+ contextEntries = entries;
+ contextStrings = strings;
+ }
+
+ /**
+ * @return The entries array
+ */
+ public byte[] getEntriesArray() {
+ return contextEntries;
+ }
+
+ /**
+ * @return The strings array
+ */
+ public byte[] getStringsArray() {
+ return contextStrings;
+ }
+ }
+
+ private static final String UST_APP_CTX_PREFIX = "$app.";
+ private static final int ENTRY_LENGTH = 13;
+ private static final ByteOrder NATIVE_ORDER = ByteOrder.nativeOrder();
+ private static final Charset UTF8_CHARSET = Charset.forName("UTF-8");
+ private static final SerializedContexts EMPTY_CONTEXTS = new SerializedContexts(new byte[0], new byte[0]);
+
+ /**
+ * From the list of requested contexts in the tracing session, look them up
+ * in the {@link ContextInfoManager}, retrieve the available ones, and
+ * serialize them into a byte array.
+ *
+ * @param enabledContexts
+ * The contexts that are enabled in the tracing session (indexed
+ * first by retriever name, then by index names). Should come
+ * from the LTTng Agent.
+ * @return The byte array representing the intersection of the requested and
+ * available contexts.
+ */
+ public static SerializedContexts queryAndSerializeRequestedContexts(Collection<Map.Entry<String, Map<String, Integer>>> enabledContexts) {
+ if (enabledContexts.isEmpty()) {
+ /* Early return if there is no requested context information */
+ return EMPTY_CONTEXTS;
+ }
+
+ ContextInfoManager contextManager;
+ try {
+ contextManager = ContextInfoManager.getInstance();
+ } catch (IOException e) {
+ /*
+ * The JNI library is not available, do not send any context
+ * information. No retriever could have been defined anyways.
+ */
+ return EMPTY_CONTEXTS;
+ }
+
+ /* Compute the total number of contexts (flatten the map) */
+ int totalArraySize = 0;
+ for (Map.Entry<String, Map<String, Integer>> contexts : enabledContexts) {
+ totalArraySize += contexts.getValue().size() * ENTRY_LENGTH;
+ }
+
+ /* Prepare the ByteBuffer that will generate the "entries" array */
+ ByteBuffer entriesBuffer = ByteBuffer.allocate(totalArraySize);
+ entriesBuffer.order(NATIVE_ORDER);
+ entriesBuffer.clear();
+
+ /* Prepare the streams that will generate the "strings" array */
+ ByteArrayOutputStream stringsBaos = new ByteArrayOutputStream();
+ DataOutputStream stringsDos = new DataOutputStream(stringsBaos);
+
+ try {
+ for (Map.Entry<String, Map<String, Integer>> entry : enabledContexts) {
+ String requestedRetrieverName = entry.getKey();
+ Map<String, Integer> requestedContexts = entry.getValue();
+
+ IContextInfoRetriever retriever = contextManager.getContextInfoRetriever(requestedRetrieverName);
+
+ for (String requestedContext : requestedContexts.keySet()) {
+ Object contextInfo;
+ if (retriever == null) {
+ contextInfo = null;
+ } else {
+ contextInfo = retriever.retrieveContextInfo(requestedContext);
+ /*
+ * 'contextInfo' can still be null here, which would
+ * indicate the retriever does not supply this context.
+ * We will still write this information so that the
+ * tracer can know about it.
+ */
+ }
+
+ /* Serialize the result to the buffers */
+ // FIXME Eventually pass the retriever name only once?
+ String fullContextName = (UST_APP_CTX_PREFIX + requestedRetrieverName + ':' + requestedContext);
+ byte[] strArray = fullContextName.getBytes(UTF8_CHARSET);
+
+ entriesBuffer.putInt(stringsDos.size());
+ stringsDos.write(strArray);
+ stringsDos.writeChar('\0');
+
+ LttngUstAgentLogger.log(ContextInfoSerializer.class,
+ "ContextInfoSerializer: Context to be sent through JNI: " + fullContextName + '=' +
+ (contextInfo == null ? "null" : contextInfo.toString()));
+
+ serializeContextInfo(entriesBuffer, stringsDos, contextInfo);
+ }
+ }
+
+ stringsDos.flush();
+ stringsBaos.flush();
+
+ } catch (IOException e) {
+ /*
+ * Should not happen because we are wrapping a
+ * ByteArrayOutputStream, which writes to memory
+ */
+ e.printStackTrace();
+ }
+
+ byte[] entriesArray = entriesBuffer.array();
+ byte[] stringsArray = stringsBaos.toByteArray();
+ return new SerializedContexts(entriesArray, stringsArray);
+ }
+
+ private static final int CONTEXT_VALUE_LENGTH = 8;
+
+ private static void serializeContextInfo(ByteBuffer entriesBuffer, DataOutputStream stringsDos, Object contextInfo) throws IOException {
+ int remainingBytes;
+ if (contextInfo == null) {
+ entriesBuffer.put(DataType.NULL.getValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH;
+
+ } else if (contextInfo instanceof Integer) {
+ entriesBuffer.put(DataType.INTEGER.getValue());
+ entriesBuffer.putInt(((Integer) contextInfo).intValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH - 4;
+
+ } else if (contextInfo instanceof Long) {
+ entriesBuffer.put(DataType.LONG.getValue());
+ entriesBuffer.putLong(((Long) contextInfo).longValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH - 8;
+
+ } else if (contextInfo instanceof Double) {
+ entriesBuffer.put(DataType.DOUBLE.getValue());
+ entriesBuffer.putDouble(((Double) contextInfo).doubleValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH - 8;
+
+ } else if (contextInfo instanceof Float) {
+ entriesBuffer.put(DataType.FLOAT.getValue());
+ entriesBuffer.putFloat(((Float) contextInfo).floatValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH - 4;
+
+ } else if (contextInfo instanceof Byte) {
+ entriesBuffer.put(DataType.BYTE.getValue());
+ entriesBuffer.put(((Byte) contextInfo).byteValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH - 1;
+
+ } else if (contextInfo instanceof Short) {
+ entriesBuffer.put(DataType.SHORT.getValue());
+ entriesBuffer.putShort(((Short) contextInfo).shortValue());
+ remainingBytes = CONTEXT_VALUE_LENGTH - 2;
+
+ } else if (contextInfo instanceof Boolean) {
+ entriesBuffer.put(DataType.BOOLEAN.getValue());
+ boolean b = ((Boolean) contextInfo).booleanValue();
+ /* Converted to one byte, write 1 for true, 0 for false */
+ entriesBuffer.put((byte) (b ? 1 : 0));
+ remainingBytes = CONTEXT_VALUE_LENGTH - 1;
+
+ } else {
+ /* Also includes the case of Character. */
+ /*
+ * We'll write the object as a string, into the strings array. We
+ * will write the corresponding offset to the entries array.
+ */
+ String str = contextInfo.toString();
+ byte[] strArray = str.getBytes(UTF8_CHARSET);
+
+ entriesBuffer.put(DataType.STRING.getValue());
+
+ entriesBuffer.putInt(stringsDos.size());
+ stringsDos.write(strArray);
+ stringsDos.writeChar('\0');
+
+ remainingBytes = CONTEXT_VALUE_LENGTH - 4;
+ }
+ entriesBuffer.position(entriesBuffer.position() + remainingBytes);
+ }
+}
projects / lttng-ust.git / blobdiff