lttng: Make text metadata detection more lenient

Text CTF metadata files are supposed to start with "/* CTF " followed by
the CTF version. https://diamon.org/ctf/v1.8.3/#spec7.1

However, to workaround traces that doen't comply with specification is
complied with then check for some common metadata keywords at the
beginning of the metadata file. This will allow to open such traces
with Trace Compass.

fixes #298

Signed-off-by: Bernd Hufmann <bernd.hufmann@ericsson.com>

Author: bhufmann

ctf/org.eclipse.tracecompass.ctf.core/src/org/eclipse/tracecompass/ctf/core/trace/Metadata.java

@@ -63,6 +63,7 @@
 import org.eclipse.tracecompass.internal.ctf.core.event.metadata.JsonFieldClassAliasMetadataNode;
 import org.eclipse.tracecompass.internal.ctf.core.event.metadata.JsonPreambleMetadataNode;
 import org.eclipse.tracecompass.internal.ctf.core.event.metadata.JsonTraceMetadataNode;
+import org.eclipse.tracecompass.internal.ctf.core.event.metadata.MetadataStrings;
 import org.eclipse.tracecompass.internal.ctf.core.event.metadata.ParseException;
 import org.eclipse.tracecompass.internal.ctf.core.event.metadata.tsdl.trace.TraceDeclarationParser;
 import org.eclipse.tracecompass.internal.ctf.core.event.types.ICTFMetadataNode;
@@ -90,6 +91,9 @@ public class Metadata {
 
     private static final String TEXT_ONLY_METADATA_HEADER_PREFIX = "/* CTF"; //$NON-NLS-1$
 
+    private static final List<String> TEXT_ONLY_METADATA_HEADER_PREFIXES = List.of(TEXT_ONLY_METADATA_HEADER_PREFIX,
+            MetadataStrings.TYPE_ALIAS, MetadataStrings.TRACE, MetadataStrings.ENV);
+
     private static final int PREVALIDATION_SIZE = 8;
 
     private static final int BITS_PER_BYTE = Byte.SIZE;
@@ -349,7 +353,7 @@ public static boolean preValidate(String path) throws CTFException {
             }
             try (BufferedReader br = new BufferedReader(new FileReader(metadataFile))) {
                 String text = br.readLine();
-                return text.startsWith(TEXT_ONLY_METADATA_HEADER_PREFIX);
+                return TEXT_ONLY_METADATA_HEADER_PREFIXES.stream().anyMatch(text::startsWith);
             } catch (IOException e) {
                 throw new CTFException(e.getMessage(), e);
             }

ctf/org.eclipse.tracecompass.ctf.core/src/org/eclipse/tracecompass/internal/ctf/core/event/metadata/MetadataStrings.java

@@ -128,5 +128,9 @@ public interface MetadataStrings {
     String VARIANT = "variant";
     /** enum */
     String ENUM = "enum";
+    /** typealias */
+    String TYPE_ALIAS = "typealias";
+    /** env */
+    String ENV = "env";
 
 }