Replace regex match with NewlineCheck for more tolerative builds

- Fixes #2

src/main/java/io/netty/build/checkstyle/NewlineCheck.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2013 The Netty Project
+ *
+ * The Netty Project licenses this file to you under the Apache License,
+ * version 2.0 (the "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at:
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.netty.build.checkstyle;
+
+import com.puppycrawl.tools.checkstyle.api.AbstractFileSetCheck;
+import com.puppycrawl.tools.checkstyle.api.FileText;
+
+import java.io.File;
+import java.util.List;
+import java.util.regex.Pattern;
+
+public class NewlineCheck extends AbstractFileSetCheck {
+
+    private enum NewlineType {
+        UNKNOWN,
+        CR,
+        LF,
+        CRLF,
+        LFCR,
+        RS
+    }
+
+    private static final Pattern NON_CRLF = Pattern.compile("(?:[^\r]\n|\r[^\n])");
+    private static final Pattern NON_LFCR = Pattern.compile("(?:[^\n]\r|\n[^\r])");
+
+    private static final NewlineType NEWLINE_TYPE;
+
+    static {
+        final String newline = System.lineSeparator();
+        if ("\n".equals(newline)) {
+            NEWLINE_TYPE = NewlineType.LF;
+        } else if ("\r".equals(newline)) {
+            NEWLINE_TYPE = NewlineType.CR;
+        } else if ("\r\n".equals(newline)) {
+            NEWLINE_TYPE = NewlineType.CRLF;
+        } else if ("\n\r".equals(newline)) {
+            NEWLINE_TYPE = NewlineType.LFCR;
+        } else if ("\u001E".equals(newline)) {
+            NEWLINE_TYPE = NewlineType.RS;
+        } else {
+            NEWLINE_TYPE = NewlineType.UNKNOWN;
+        }
+    }
+
+    @Override
+    protected void processFiltered(File aFile, List<String> aLines) {
+        String text = FileText.fromLines(aFile, aLines).getFullText().toString();
+
+        switch (NEWLINE_TYPE) {
+        case LF:
+            if (text.indexOf('\r') >= 0) {
+                reportNewlineViolation();
+            }
+            break;
+        case CR:
+            if (text.indexOf('\n') >= 0) {
+                reportNewlineViolation();
+            }
+            break;
+        case CRLF:
+            if (NON_CRLF.matcher(text).find()) {
+                reportNewlineViolation();
+            }
+            break;
+        case LFCR:
+            if (NON_LFCR.matcher(text).find()) {
+                reportNewlineViolation();
+            }
+            break;
+        case RS:
+            if (text.indexOf('\u001E') >= 0) {
+                reportNewlineViolation();
+            }
+            break;
+        }
+    }
+
+    private void reportNewlineViolation() {
+        log(0, "invalid newline character (expected: " + NEWLINE_TYPE + ')');
+    }
+}

src/main/resources/io/netty/checkstyle.xml

@@ -23,9 +23,7 @@
   </module>
   <module name="FileTabCharacter"/>
   <module name="JavadocPackage"/>
-  <module name="NewlineAtEndOfFile">
-    <property name="lineSeparator" value="lf" />
-  </module>
+  <module name="NewlineAtEndOfFile" />
   <!-- Copyright headers -->
   <module name="RegexpSingleline">
     <property name="format" value="^(\s|\*)*Copyright\s+[0-9]+\s+The Netty Project\s*$"/>
@@ -45,10 +43,7 @@
     <property name="message" value="IDE-generated comment"/>
   </module>
   <!-- Force UNIX line separator -->
-  <module name="RegexpMultiline">
-    <property name="format" value="\r"/>
-    <property name="message" value="non-Unix line separator"/>
-  </module>
+  <module name="io.netty.build.checkstyle.NewlineCheck"/>
   <!-- Trailing whitespace -->
   <module name="RegexpSingleline">
     <property name="format" value="\s+$"/>