Improve ReadOnlySharedStringsTable to cope gracefully with an empty SST part.

https://bz.apache.org/bugzilla/show_bug.cgi?id=58262

git-svn-id: https://svn.apache.org/repos/asf/poi/trunk@1696559 13f79535-47bb-0310-9956-ffa450edef68

src/ooxml/java/org/apache/poi/xssf/eventusermodel/ReadOnlySharedStringsTable.java

@@ -132,6 +132,7 @@ public class ReadOnlySharedStringsTable extends DefaultHandler {
      * @throws ParserConfigurationException
      */
     public void readFrom(InputStream is) throws IOException, SAXException {
+        if (is.available() > 0) {
             InputSource sheetSource = new InputSource(is);
             try {
                 XMLReader sheetParser = SAXHelper.newXMLReader();
@@ -141,6 +142,7 @@ public class ReadOnlySharedStringsTable extends DefaultHandler {
                 throw new RuntimeException("SAX parser appears to be broken - " + e.getMessage());
             }
         }
+    }
 
     /**
      * Return an integer representing the total count of strings in the workbook. This count does not

src/ooxml/testcases/org/apache/poi/xssf/eventusermodel/TestReadOnlySharedStringsTable.java

@@ -20,12 +20,16 @@
 package org.apache.poi.xssf.eventusermodel;
 
 import junit.framework.TestCase;
+
 import org.apache.poi.POIDataSamples;
 import org.apache.poi.openxml4j.opc.OPCPackage;
 import org.apache.poi.openxml4j.opc.PackagePart;
 import org.apache.poi.xssf.model.SharedStringsTable;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
 import org.openxmlformats.schemas.spreadsheetml.x2006.main.CTRst;
+import org.xml.sax.SAXException;
 
+import java.io.IOException;
 import java.util.List;
 import java.util.regex.Pattern;
 
@@ -55,4 +59,24 @@ public final class TestReadOnlySharedStringsTable extends TestCase {
         }
 
 	}
+    
+    public void testEmptySSTOnPackageObtainedViaWorkbook() throws Exception {
+        XSSFWorkbook wb = new XSSFWorkbook(_ssTests.openResourceAsStream("noSharedStringTable.xlsx"));
+        OPCPackage pkg = wb.getPackage();
+        assertEmptySST(pkg);
+        wb.close();
+    }
+    
+    public void testEmptySSTOnPackageDirect() throws Exception {
+        OPCPackage pkg = OPCPackage.open(_ssTests.openResourceAsStream("noSharedStringTable.xlsx"));
+        assertEmptySST(pkg);
+    }
+
+    private void assertEmptySST(OPCPackage pkg) throws IOException, SAXException {
+        ReadOnlySharedStringsTable sst = new ReadOnlySharedStringsTable(pkg);
+        assertEquals(0, sst.getCount());
+        assertEquals(0, sst.getUniqueCount());
+        assertNull(sst.getItems()); // same state it's left in if fed a package which has no SST part.
+    }
+    
 }