fix #2328: Have a wrapper around Matcher to avoid String related memory

issues

1 files changed, 91 insertions, 0 deletions

diff --git a/main/src/cgeo/geocaching/utils/MatcherWrapper.java b/main/src/cgeo/geocaching/utils/MatcherWrapper.java
new file mode 100644
index 0000000..c3c1663
--- /dev/null
+++ b/main/src/cgeo/geocaching/utils/MatcherWrapper.java
@@ -0,0 +1,91 @@
+package cgeo.geocaching.utils;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Wrapper around the regex {@link Matcher} class. This implementation optimizes the memory usage of the matched
+ * Strings.
+ *
+ */
+public class MatcherWrapper {
+    private final Matcher matcher;
+
+    public MatcherWrapper(Pattern pattern, String input) {
+        this.matcher = pattern.matcher(input);
+    }
+
+    /**
+     * see {@link Matcher#find()}
+     */
+    public boolean find() {
+        return matcher.find();
+    }
+
+    /**
+     * see {@link Matcher#group(int)}
+     */
+    public String group(int index) {
+        return newString(matcher.group(index));
+    }
+
+    /**
+     * This method explicitly creates a new String instance from an already existing String. This is necessary to avoid
+     * huge memory leaks in our parser. If we do regular expression matching on large Strings, the returned matches are
+     * otherwise memory mapped substrings of the huge original String, therefore blocking the garbage collector from
+     * removing the huge input String.
+     * <p>
+     * Do not change this method, even if Findbugs and other tools will report a violation for that line!
+     *
+     * @param input
+     * @return
+     */
+    private static String newString(String input) {
+        if (input == null) {
+            return null;
+        }
+        return new String(input); // DON'T REMOVE THE "new String" HERE!
+    }
+
+    /**
+     * see {@link Matcher#groupCount()}
+     */
+    public int groupCount() {
+        return matcher.groupCount();
+    }
+
+    /**
+     * see {@link Matcher#group()}
+     */
+    public String group() {
+        return newString(matcher.group());
+    }
+
+    /**
+     * see {@link Matcher#start()}
+     */
+    public int start() {
+        return matcher.start();
+    }
+
+    /**
+     * see {@link Matcher#replaceAll(String)}
+     */
+    public String replaceAll(String replacement) {
+        return newString(matcher.replaceAll(replacement));
+    }
+
+    /**
+     * see {@link Matcher#matches()}
+     */
+    public boolean matches() {
+        return matcher.matches();
+    }
+
+    /**
+     * see {@link Matcher#replaceFirst(String)}
+     */
+    public String replaceFirst(String replacement) {
+        return newString(matcher.replaceFirst(replacement));
+    }
+}