fix isssue csv-259 (apache#61)

* fix isssue csv-259

* add testcase for CSV259

* exclude csv259 test file

* organize the imports

Author: dota17

pom.xml

@@ -256,6 +256,7 @@
             <exclude>src/test/resources/ferc.gov/contract.txt</exclude>
             <exclude>src/test/resources/ferc.gov/transaction.txt</exclude>
             <exclude>src/test/resources/**/*.bin</exclude>
+            <exclude>src/test/resources/CSV-259/sample.txt</exclude>
           </excludes>
         </configuration>
       </plugin>
@@ -373,6 +374,7 @@
             <exclude>src/test/resources/ferc.gov/contract.txt</exclude>
             <exclude>src/test/resources/ferc.gov/transaction.txt</exclude>
             <exclude>src/test/resources/**/*.bin</exclude>
+            <exclude>src/test/resources/CSV-259/sample.txt</exclude>
           </excludes>
         </configuration>
       </plugin>

src/main/java/org/apache/commons/csv/CSVFormat.java

@@ -1408,6 +1408,7 @@ private void printWithEscapes(final Reader reader, final Appendable out) throws
                 if (pos > start) {
                     out.append(builder.substring(start, pos));
                     builder.setLength(0);
+                    pos = -1;
                 }
                 if (c == LF) {
                     c = 'n';

src/test/java/org/apache/commons/csv/CSVPrinterTest.java

@@ -34,6 +34,8 @@
 import java.io.StringReader;
 import java.io.StringWriter;
 import java.io.Writer;
+import java.io.Reader;
+import java.io.FileReader;
 import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.sql.BatchUpdateException;
@@ -310,6 +312,16 @@ public void testCSV135() throws IOException {
         tryFormat(list, '"',  '"',  "\"\"\"\"\"\",\\\\,\"\\\"\"\\\"");
     }
 
+    @Test
+    public void testCSV259() throws IOException {
+        final StringWriter sw = new StringWriter();
+        final Reader reader = new FileReader("src/test/resources/CSV-259/sample.txt");
+        try (final CSVPrinter printer = new CSVPrinter(sw, CSVFormat.DEFAULT.withEscape('!').withQuote(null))) {
+            printer.print(reader);
+            assertEquals("x!,y!,z", sw.toString());
+        }
+    }
+
     @Test
     public void testDelimeterQuoted() throws IOException {
         final StringWriter sw = new StringWriter();

src/test/resources/CSV-259/sample.txt

@@ -0,0 +1 @@
+x,y,z