Fixing a bug when multi-byte characters were split

src/main/java/com/fasterxml/aalto/out/ByteXmlWriter.java

@@ -390,7 +390,7 @@ public final void writeStartTagEnd()
             flushBuffer();
         }
         _outputBuffer[_outputPtr++] = BYTE_GT;
-    }    
+    }
 
     @Override
     public void writeStartTagEmptyEnd()
@@ -435,7 +435,7 @@ public final void writeEndTag(WName name)
         ptr += name.appendBytes(bbuf, ptr);
         bbuf[ptr++] = BYTE_GT;
         _outputPtr = ptr;
-    }    
+    }
 
     /*
     /**********************************************************************
@@ -572,6 +572,8 @@ protected final void writeAttrValue(char[] vbuf, int offset, int len)
     {
         if (_surrogate != 0) {
             outputSurrogates(_surrogate, vbuf[offset]);
+//           reset the temporary surrogate storage
+            _surrogate = 0;
             ++offset;
             --len;
         }
@@ -785,7 +787,7 @@ public int writeCData(char[] cbuf, int offset, int len)
             writeCDataEnd(); // will check surrogates
         }
         return ix;
-    }    
+    }
 
     protected int writeCDataContents(char[] cbuf, int offset, int len)
         throws IOException, XMLStreamException
@@ -865,7 +867,7 @@ protected int writeCDataContents(char[] cbuf, int offset, int len)
             }
         }
         return -1;
-    }    
+    }
 
     @Override
     public final void writeCharacters(String text)
@@ -908,6 +910,8 @@ public final void writeCharacters(char[] cbuf, int offset, int len)
     {
         if (_surrogate != 0) {
             outputSurrogates(_surrogate, cbuf[offset]);
+//           reset the temporary surrogate storage
+            _surrogate = 0;
             ++offset;
             --len;
         }
@@ -1088,7 +1092,7 @@ private final void writeSplitCharacters(char[] cbuf, int offset, int len)
             }
             _outputBuffer[_outputPtr++] = (byte)ch;
         }
-    }    
+    }
 
     /*
     /**********************************************************************
@@ -1439,7 +1443,7 @@ public void writeXmlDeclaration(String version, String encoding, String standalo
         // !!! TBI: check validity
         writeRaw(version, 0, version.length());
         writeRaw(BYTE_APOS);
-        
+
         if (encoding != null && encoding.length() > 0) {
             writeRaw(BYTES_XMLDECL_ENCODING);
             // !!! TBI: check validity
@@ -1453,7 +1457,7 @@ public void writeXmlDeclaration(String version, String encoding, String standalo
             writeRaw(BYTE_APOS);
         }
         writeRaw(BYTE_QMARK, BYTE_GT);
-    }    
+    }
 
     /*
     /**********************************************************************
@@ -1594,7 +1598,7 @@ protected final void flushBuffer()
     protected final void writeAsEntity(int c)
         throws IOException
     {
-        // Quickie check to avoid 
+        // Quickie check to avoid
 
         byte[] buf = _outputBuffer;
         int ptr = _outputPtr;

src/test/java/com/fasterxml/aalto/sax/TestSaxWriter.java

@@ -0,0 +1,57 @@
+package com.fasterxml.aalto.sax;
+
+import com.fasterxml.aalto.out.Utf8XmlWriter;
+import com.fasterxml.aalto.out.WriterConfig;
+
+import java.io.ByteArrayOutputStream;
+
+public class TestSaxWriter extends base.BaseTestCase {
+
+    public void testSurrogateMemory1() throws Exception {
+        // This test aims to produce the
+        // javax.xml.stream.XMLStreamException: Incomplete surrogate pair in content: first char 0xd835, second 0x78
+        // error message. Before fixing the respective issue, it was provoked by a multi-byte character
+        // where the first byte was exactly at the end of the internal reading buffer and enough further data
+        // to also fill the next two internal reading buffers. Then, the code would try to fuse the first byte
+        // of the original multi-byte character with the first character in the third buffer because
+        // ByteXmlWriter#_surrogate was not set back to 0 after writing the original multi-byte character.
+        StringBuilder testText = new StringBuilder();
+        for (int i = 0; i < 511; i++)
+            testText.append('x');
+        testText.append("\uD835\uDFCE");
+        for (int i = 0; i < 512; i++)
+            testText.append('x');
+
+        WriterConfig writerConfig = new WriterConfig();
+        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+        Utf8XmlWriter writer = new Utf8XmlWriter(writerConfig, byteArrayOutputStream);
+        writer.writeStartTagStart(writer.constructName("testelement"));
+        writer.writeAttribute(writer.constructName("testattr"), testText.toString());
+        writer.writeStartTagEnd();
+        writer.writeEndTag(writer.constructName("testelement"));
+        writer.close(false);
+
+    }
+
+    public void testSurrogateMemory2() throws Exception {
+        // This test aims to produce the
+        // java.io.IOException: Unpaired surrogate character (0xd835)
+        // error message. Before fixing the respective issue, it was provoked by a multi-byte character
+        // where the first byte was exactly at the end of the internal reading buffer and the next
+        // reading buffer was enough to write all the remaining data. Then, by the missing reset of
+        // ByteXmlWriter#_surrogate, the code expected another multi-byte surrogate that never came.
+        StringBuilder testText = new StringBuilder();
+        for (int i = 0; i < 511; i++)
+            testText.append('x');
+        testText.append("\uD835\uDFCE");
+
+        WriterConfig writerConfig = new WriterConfig();
+        ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
+        Utf8XmlWriter writer = new Utf8XmlWriter(writerConfig, byteArrayOutputStream);
+        writer.writeStartTagStart(writer.constructName("testelement"));
+        writer.writeAttribute(writer.constructName("testattr"), testText.toString());
+        writer.writeStartTagEnd();
+        writer.writeEndTag(writer.constructName("testelement"));
+        writer.close(false);
+    }
+}