Implemented and tested a more robust report type parsing

Core/src/org/sleuthkit/autopsy/datasourceprocessors/xry/XRYFileReader.java

@@ -52,7 +52,11 @@ final class XRYFileReader implements AutoCloseable {
     //Assume UTF_16LE
     private static final Charset CHARSET = StandardCharsets.UTF_16LE;
 
-    //Assume all XRY reports have the type on the 3rd line.
+    //Assume the header begins with 'xry export'.
+    private static final String START_OF_HEADER = "xry export";
+
+    //Assume all XRY reports have the type on the 3rd line
+    //relative to the start of the header.
     private static final int LINE_WITH_REPORT_TYPE = 3;
 
     //Assume all headers are 5 lines in length.
@@ -91,8 +95,12 @@ final class XRYFileReader implements AutoCloseable {
         reader = Files.newBufferedReader(xryFile, CHARSET);
         xryFilePath = xryFile;
 
-        //Advance the reader to the start of the first XRY entity.
-        for (int i = 0; i < HEADER_LENGTH_IN_LINES; i++) {
+        //Advance the reader to the start of the header.
+        advanceToHeader(reader);
+
+        //Advance the reader past the header to the start 
+        //of the first XRY entity.
+        for (int i = 1; i < HEADER_LENGTH_IN_LINES; i++) {
             reader.readLine();
         }
 
@@ -298,8 +306,11 @@ final class XRYFileReader implements AutoCloseable {
      */
     private static Optional<String> getType(Path file) throws IOException {
         try (BufferedReader reader = Files.newBufferedReader(file, CHARSET)) {
+            //Header may not start at the beginning of the file.
+            advanceToHeader(reader);
+
             //Advance the reader to the line before the report type.
-            for (int i = 0; i < LINE_WITH_REPORT_TYPE - 1; i++) {
+            for (int i = 1; i < LINE_WITH_REPORT_TYPE - 1; i++) {
                 reader.readLine();
             }
 
@@ -310,4 +321,51 @@ final class XRYFileReader implements AutoCloseable {
             return Optional.empty();
         }
     }
+
+    /**
+     * Advances the reader to the start of the header. The XRY Export header may
+     * not be the first n lines of the file. It may be preceded by new lines or
+     * white space.
+     *
+     * This function will consume the first line of the header, which will be
+     * 'XRY Export'.
+     *
+     * @param reader BufferedReader pointing to the xry file
+     * @throws IOException if an I/O error occurs
+     */
+    private static void advanceToHeader(BufferedReader reader) throws IOException {
+        String line;
+        if((line = reader.readLine()) == null) {
+            return;
+        }
+        
+        String normalizedLine = line.trim().toLowerCase();
+        if (normalizedLine.equals(START_OF_HEADER)) {
+            return;
+        }
+
+        /**
+         * The first line may have 0xFFFE BOM prepended to it, which will cause
+         * the equality check to fail. This bit a logic will try to remove those
+         * bytes and attempt another check.
+         */
+        byte[] normalizedBytes = normalizedLine.getBytes(CHARSET);
+        if (normalizedBytes.length > 2) {
+            normalizedLine = new String(normalizedBytes, 2,
+                    normalizedBytes.length - 2, CHARSET);
+            if (normalizedLine.equals(START_OF_HEADER)) {
+                return;
+            }
+        }
+
+        /**
+         * All other lines will need to match completely.
+         */
+        while ((line = reader.readLine()) != null) {
+            normalizedLine = line.trim().toLowerCase();
+            if (normalizedLine.equals(START_OF_HEADER)) {
+                return;
+            }
+        }
+    }
 }