Issue checkstyle#344: add multi-thread support to CheckstyleReportsPa…

…rser

patch-diff-report-tool/src/main/java/com/github/checkstyle/data/CheckstyleRecord.java

@@ -30,7 +30,7 @@
  * @author attatrol
  *
  */
-public final class CheckstyleRecord {
+public final class CheckstyleRecord implements Comparable<CheckstyleRecord> {
 
     /**
      * It is usual for sources of records to have name that
@@ -177,17 +177,31 @@ public String getSimpleCuttedSourceName() {
 
     /**
      * Compares CheckstyleRecord instances by their content.
-     * It is used in a single controlled occasion in the code.
+     * The order is source, line, column, severity, message.
+     * Properties index and xref are ignored.
      *
      * @param other
-     *        another ChechstyleRecord instance under comparison
+     *        another CheckstyleRecord instance under comparison
      *        with this instance.
-     * @return true if instances are equal.
+     * @return 0 if the objects are equal, a negative integer if this record is before the specified
+     *         record, or a positive integer if this record is after the specified record.
      */
-    public boolean specificEquals(final CheckstyleRecord other) {
-        return this.line == other.line && this.column == other.column
-                && this.source.equals(other.source)
-                && this.message.equals(other.message);
+    public int compareTo(final CheckstyleRecord other) {
+        int diff = this.source.compareTo(other.source);
+        if (diff == 0) {
+            diff = Integer.compare(this.line, other.line);
+        }
+        if (diff == 0) {
+            diff = Integer.compare(this.column, other.column);
+        }
+        if (diff == 0) {
+            diff = SeverityLevel.getInstance(this.severity)
+                .compareTo(SeverityLevel.getInstance(other.severity));
+        }
+        if (diff == 0) {
+            diff = this.message.compareTo(other.message);
+        }
+        return diff;
     }
 
 }

patch-diff-report-tool/src/main/java/com/github/checkstyle/data/DiffReport.java

@@ -21,10 +21,11 @@
 
 import java.util.ArrayList;
 import java.util.Collections;
-import java.util.Comparator;
+import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
-import java.util.TreeMap;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ConcurrentSkipListMap;
 
 import com.github.checkstyle.parser.CheckstyleReportsParser;
 
@@ -42,21 +43,26 @@ public final class DiffReport {
      * Container for parsed data,
      * note it is a TreeMap for memory keeping purposes.
      */
-    private Map<String, List<CheckstyleRecord>> records =
-            new TreeMap<>();
+    private final Map<String, List<CheckstyleRecord>> records =
+            new ConcurrentSkipListMap<>();
 
     /**
      * Container for statistical data.
      */
-    private Statistics statistics = new Statistics();
+    private final Statistics statistics = new Statistics();
+
+    /**
+     * Asynchronous tasks for difference calculation.
+     */
+    private final List<CompletableFuture<Void>> asyncTasks = new ArrayList<>();
 
     /**
      * Getter for data container.
      *
      * @return map containing parsed data.
      */
     public Map<String, List<CheckstyleRecord>> getRecords() {
-        return records;
+        return Collections.unmodifiableMap(records);
     }
 
     public Statistics getStatistics() {
@@ -76,6 +82,7 @@ public Statistics getStatistics() {
     public void addRecords(List<CheckstyleRecord> newRecords,
             String filename) {
         if (!newRecords.isEmpty()) {
+            Collections.sort(newRecords);
             final List<CheckstyleRecord> popped =
                 records.put(filename, newRecords);
             if (popped != null) {
@@ -85,57 +92,99 @@ public void addRecords(List<CheckstyleRecord> newRecords,
                     records.remove(filename);
                 }
                 else {
-                    Collections.sort(diff, new PositionOrderComparator());
                     records.put(filename, diff);
                 }
             }
         }
     }
 
     /**
-     * Creates difference between 2 lists of records.
+     * Adds new records to the diff report asynchronously,
+     * when there are records with this filename, comparison
+     * between them and new record is performed and only difference is saved.
      *
-     * @param list1
+     * @param newRecords
+     *        a new records list.
+     * @param filename
+     *        name of a file which is a cause of records generation.
+     */
+    public void addRecordsAsync(
+            List<CheckstyleRecord> newRecords, String filename) {
+        asyncTasks.add(CompletableFuture.runAsync(() -> addRecords(newRecords, filename)));
+    }
+
+    /**
+     * Creates difference between 2 sorted lists of records.
+     *
+     * @param firstList
      *        the first list.
-     * @param list2
+     * @param secondList
      *        the second list.
      * @return the difference list.
      */
     private static List<CheckstyleRecord> produceDiff(
-            List<CheckstyleRecord> list1, List<CheckstyleRecord> list2) {
-        final List<CheckstyleRecord> diff = new ArrayList<>();
-        for (CheckstyleRecord rec1 : list1) {
-            if (!isInList(list2, rec1)) {
-                diff.add(rec1);
-            }
+            List<CheckstyleRecord> firstList, List<CheckstyleRecord> secondList) {
+        final List<CheckstyleRecord> result;
+        if (firstList.isEmpty()) {
+            result = secondList;
         }
-        for (CheckstyleRecord rec2 : list2) {
-            if (!isInList(list1, rec2)) {
-                diff.add(rec2);
-            }
+        else if (secondList.isEmpty()) {
+            result = firstList;
+        }
+        else {
+            result = produceDiff(firstList.iterator(), secondList.iterator());
         }
-        return diff;
+        return result;
     }
 
     /**
-     * Compares the record against list of records.
+     * Creates difference between 2 non-empty iterators of records.
      *
-     * @param list
-     *        of records.
-     * @param testedRecord
-     *        the record.
-     * @return true, if has its copy in a list.
+     * @param firstIterator
+     *        the first iterator.
+     * @param secondIterator
+     *        the second iterator.
+     * @return the difference list (always sorted).
      */
-    private static boolean isInList(List<CheckstyleRecord> list,
-            CheckstyleRecord testedRecord) {
-        boolean belongsToList = false;
-        for (CheckstyleRecord checkstyleRecord : list) {
-            if (testedRecord.specificEquals(checkstyleRecord)) {
-                belongsToList = true;
-                break;
+    private static List<CheckstyleRecord> produceDiff(
+            Iterator<CheckstyleRecord> firstIterator, Iterator<CheckstyleRecord> secondIterator) {
+        CheckstyleRecord firstVal = firstIterator.next();
+        CheckstyleRecord secondVal = secondIterator.next();
+        final List<CheckstyleRecord> result = new ArrayList<>();
+        while (true) {
+            final int diff = firstVal.compareTo(secondVal);
+            if (diff < 0) {
+                result.add(firstVal);
+                if (!firstIterator.hasNext()) {
+                    result.add(secondVal);
+                    break;
+                }
+                firstVal = firstIterator.next();
             }
+            else if (diff > 0) {
+                result.add(secondVal);
+                if (!secondIterator.hasNext()) {
+                    result.add(firstVal);
+                    break;
+                }
+                secondVal = secondIterator.next();
+            }
+            else {
+                if (!firstIterator.hasNext() || !secondIterator.hasNext()) {
+                    break;
+                }
+                firstVal = firstIterator.next();
+                secondVal = secondIterator.next();
+            }
+        }
+        // add tails
+        while (firstIterator.hasNext()) {
+            result.add(firstIterator.next());
+        }
+        while (secondIterator.hasNext()) {
+            result.add(secondIterator.next());
         }
-        return belongsToList;
+        return result;
     }
 
     /**
@@ -161,26 +210,9 @@ public void getDiffStatistics() {
     }
 
     /**
-     * Comparator used to sort lists of CheckstyleRecord objects
-     * by their position in code.
-     *
-     * @author atta_troll
-     *
+     * Await completion of all asynchronous tasks.
      */
-    private static class PositionOrderComparator
-        implements Comparator<CheckstyleRecord> {
-
-        @Override
-        public int compare(final CheckstyleRecord arg0,
-                final CheckstyleRecord arg1) {
-            final int difference = arg0.getLine() - arg1.getLine();
-            if (difference == 0) {
-                return arg0.getColumn() - arg1.getColumn();
-            }
-            else {
-                return difference;
-            }
-        }
+    public void joinAsyncTasksAll() {
+        asyncTasks.forEach(CompletableFuture::join);
     }
-
 }

patch-diff-report-tool/src/main/java/com/github/checkstyle/data/SeverityLevel.java

@@ -0,0 +1,65 @@
+////////////////////////////////////////////////////////////////////////////////
+// checkstyle: Checks Java source code for adherence to a set of rules.
+// Copyright (C) 2001-2020 the original author or authors.
+//
+// This library is free software; you can redistribute it and/or
+// modify it under the terms of the GNU Lesser General Public
+// License as published by the Free Software Foundation; either
+// version 2.1 of the License, or (at your option) any later version.
+//
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public
+// License along with this library; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+////////////////////////////////////////////////////////////////////////////////
+
+package com.github.checkstyle.data;
+
+/**
+ * Severity level for a {@link CheckstyleRecord}.
+ * Used to compare two records in predefined order: "info", "warning", "error", all other.
+ */
+public enum SeverityLevel {
+
+    /** Severity level info. */
+    INFO,
+
+    /** Severity level warning. */
+    WARNING,
+
+    /** Severity level error. */
+    ERROR,
+
+    /** All other severity levels. */
+    OTHER;
+
+    /**
+     * SeverityLevel factory method.
+     *
+     * @param securityLevelName level name, such as "info", "warning", "error", etc.
+     * @return the {@code SeverityLevel} associated with {@code securityLevelName}
+     */
+    public static SeverityLevel getInstance(String securityLevelName) {
+        final SeverityLevel result;
+        switch (securityLevelName) {
+            case "info":
+                result = INFO;
+                break;
+            case "warning":
+                result = WARNING;
+                break;
+            case "error":
+                result = ERROR;
+                break;
+            default:
+                result = OTHER;
+                break;
+        }
+        return result;
+    }
+
+}

patch-diff-report-tool/src/main/java/com/github/checkstyle/parser/CheckstyleReportsParser.java

@@ -133,12 +133,14 @@ public static DiffReport parse(Path baseXml, Path patchXml, int portionSize)
             parseXmlPortion(content, baseReader, portionSize, BASE_REPORT_INDEX);
             parseXmlPortion(content, patchReader, portionSize, PATCH_REPORT_INDEX);
         }
+        content.joinAsyncTasksAll();
         content.getDiffStatistics();
         return content;
     }
 
     /**
      * Parses portion of the XML report.
+     * Difference generation is performed asynchronously for efficient CPU usage.
      *
      * @param diffReport
      *        container for parsed data.
@@ -187,7 +189,7 @@ else if (startElementName.equals(ERROR_TAG)) {
             if (event.isEndElement()) {
                 final EndElement endElement = event.asEndElement();
                 if (endElement.getName().getLocalPart().equals(FILE_TAG)) {
-                    diffReport.addRecords(records, filename);
+                    diffReport.addRecordsAsync(records, filename);
                     if (counter == 0) {
                         break;
                     }