StringUtil#convertFileToLinuxStyle safe for non-text files

Author: MikeMirzayanov

code/src/main/java/com/codeforces/commons/text/StringUtil.java

@@ -3,14 +3,14 @@
 import com.codeforces.commons.collection.MapBuilder;
 import com.codeforces.commons.holder.Holders;
 import com.codeforces.commons.io.FileUtil;
-import com.codeforces.commons.io.IoUtil;
 import com.codeforces.commons.pair.*;
 import com.codeforces.commons.properties.internal.CommonsPropertiesUtil;
 import com.codeforces.commons.reflection.ReflectionUtil;
 import com.codeforces.commons.text.similarity.SimilarityChecker;
 import org.apache.commons.codec.binary.Base64;
 import org.apache.commons.codec.binary.Hex;
 import org.apache.commons.codec.digest.DigestUtils;
+import org.apache.commons.io.FileUtils;
 import org.apache.commons.lang3.ArrayUtils;
 import org.apache.commons.lang3.mutable.MutableBoolean;
 import org.apache.commons.text.translate.CharSequenceTranslator;
@@ -36,14 +36,17 @@
 import java.awt.event.KeyEvent;
 import java.awt.font.FontRenderContext;
 import java.awt.geom.Rectangle2D;
-import java.io.*;
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.io.StringReader;
 import java.lang.reflect.Array;
 import java.nio.charset.StandardCharsets;
 import java.security.InvalidKeyException;
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
-import java.util.List;
 import java.util.*;
+import java.util.List;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReadWriteLock;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
@@ -1206,25 +1209,46 @@ private static String wellformSingleLineForWindows(String line) {
         return trim(sb.toString());
     }
 
+    /**
+     * Removes all \r if it really looks like windows encoded text file.
+     *
+     * @param file File to process
+     * @throws IOException On any IO error
+     */
     public static void convertFileToLinuxStyle(File file) throws IOException {
-        byte[] bytes = FileUtil.getBytes(file);
-        BufferedReader reader = null;
-        BufferedWriter writer = null;
+        byte[] content = FileUtil.getBytes(file);
 
-        try {
-            reader = new BufferedReader(new InputStreamReader(new ByteArrayInputStream(bytes), UTF_8));
-            writer = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(file), UTF_8));
+        boolean validCrLf = true;
+        int crCount = 0;
+
+        for (int i = 0; i < content.length; i++) {
+            if (content[i] == 0x0D) { // \r
+                crCount++;
+                if (i + 1 >= content.length || content[i + 1] != 0x0A) {
+                    validCrLf = false;
+                    break;
+                }
+            } else if (content[i] == 0x0A) { // \n
+                if (i == 0 || content[i - 1] != 0x0D) {
+                    validCrLf = false;
+                    break;
+                }
+            }
+        }
 
-            String line;
-            while ((line = reader.readLine()) != null) {
-                writer.write(line);
-                writer.write(10);
+        if (validCrLf && crCount > 0) {
+            // Remove all \r (0x0D) bytes
+            ByteArrayOutputStream out = new ByteArrayOutputStream(content.length - crCount);
+            for (byte b : content) {
+                if (b != 0x0D) {
+                    out.write(b);
+                }
             }
-        } finally {
-            IoUtil.closeQuietly(reader, writer);
+            FileUtils.writeByteArrayToFile(file, out.toByteArray());
         }
     }
 
+
     /**
      * @param s         Given string.
      * @param maxLength Maximal length.

code/src/test/java/com/codeforces/commons/text/StringUtilTest.java

@@ -1,9 +1,15 @@
 package com.codeforces.commons.text;
 
+import com.codeforces.commons.io.FileUtil;
+import com.codeforces.commons.io.IoUtil;
 import com.codeforces.commons.text.similarity.SimilarityChecker;
 import org.apache.commons.lang3.StringUtils;
+import org.junit.Assert;
 import org.junit.Test;
 
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStream;
 import java.util.*;
 import java.util.List;
 import java.util.function.Predicate;
@@ -356,4 +362,45 @@ public void testWellformForWindows() {
         assertEquals("a b c\r\nd e\r\n", StringUtil.wellformForWindows("\r\n\r\n  a  b     c     \r\n  d      e"));
         assertEquals("a b c\r\n\r\nd e\r\n", StringUtil.wellformForWindows("a b c\r\n\r\nd e\r\n"));
     }
+
+    @Test
+    public void testConvertFileToLinuxStyle() throws IOException {
+        testConvertFileToLinuxStyle("01");
+        testConvertFileToLinuxStyle("02");
+        testConvertFileToLinuxStyle("03");
+        testConvertFileToLinuxStyle("04");
+        testConvertFileToLinuxStyle("05");
+        testConvertFileToLinuxStyle("06");
+    }
+
+    private void testConvertFileToLinuxStyle(String fileName) throws IOException {
+        byte[] inputBytes = getConvertFileToLinuxStyleResourceBytes(fileName + ".in");
+        byte[] answerBytes = getConvertFileToLinuxStyleResourceBytes(fileName + ".out");
+
+        File inputFile = File.createTempFile("convertFileToLinuxStyle", fileName + ".in");
+        FileUtil.writeFile(inputFile, inputBytes);
+
+        StringUtil.convertFileToLinuxStyle(inputFile);
+        byte[] outputBytes = FileUtil.getBytes(inputFile);
+        FileUtil.deleteTotally(inputFile);
+
+        Assert.assertArrayEquals("Subtest '" + fileName + "' failed.",
+                answerBytes, outputBytes);
+    }
+
+    private static byte[] getConvertFileToLinuxStyleResourceBytes(String resourceName) throws IOException {
+        String resource = "/com/codeforces/commons/text/convertFileToLinuxStyle/" + resourceName;
+
+        InputStream resourceStream = StringUtilTest.class.getResourceAsStream(
+                resource);
+        if (resourceStream == null) {
+            throw new IOException("Can't find resource '" + resource + "'.");
+        }
+
+        try {
+            return IoUtil.toByteArray(resourceStream);
+        } finally {
+            IoUtil.closeQuietly(resourceStream);
+        }
+    }
 }