[CONJ-589] clob length and truncate methods to behave correctly for

characters encoded in 2 UTF-16 characters

src/main/java/org/mariadb/jdbc/MariaDbClob.java

@@ -238,45 +238,96 @@ public OutputStream setAsciiStream(long pos) throws SQLException {
    */
   @Override
   public long length() {
+    //The length of a character string is the number of UTF-16 units (not the number of characters)
     long len = 0;
-    for (int i = offset; i < offset + length; ) {
-      int byteValue = data[i] & 0xff;
-      if (byteValue < 0x80) {
-        i += 1;
-      } else if (byteValue < 0xC2) {
-        throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
-      } else if (byteValue < 0xE0) {
-        i += 2;
-      } else if (byteValue < 0xF0) {
-        i += 3;
-      } else if (byteValue < 0xF8) {
-        len++;
-        i += 4;
+    int pos = offset;
+
+    //set ASCII (<= 127 chars)
+    for(; len < length && data[pos] >= 0; ) {
+      len++;
+      pos++;
+    }
+
+    //multi-bytes UTF-8
+    while(pos < offset + length) {
+      byte firstByte = data[pos++];
+      if (firstByte < 0) {
+        if (firstByte >> 5 != -2 || (firstByte & 30) == 0) {
+          if (firstByte >> 4 == -2) {
+            if (pos + 1 < offset + length) {
+              pos+=2;
+              len++;
+            } else {
+              throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+            }
+          } else if (firstByte >> 3 != -2) {
+            throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+          } else if (pos + 2 < offset + length) {
+            pos+=3;
+            len+=2;
+          } else {
+            //bad truncated UTF8
+            pos += offset + length;
+            len+=1;
+          }
+        } else {
+          pos++;
+          len++;
+        }
       } else {
-        throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+        len++;
       }
-      len++;
     }
     return len;
   }
 
   @Override
-  public void truncate(final long len) throws SQLException {
+  public void truncate(final long truncateLen) throws SQLException {
+
+    //truncate the number of UTF-16 characters
+    //this can result in a bad UTF-8 string if string finish with a
+    //character represented in 2 UTF-16
+    long len = 0;
     int pos = offset;
-    for (; pos < offset + Math.min(length, len); ) {
-      int byteValue = data[pos] & 0xff;
-      if (byteValue < 0x80) {
-        pos += 1;
-      } else if (byteValue < 0xC2) {
-        throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
-      } else if (byteValue < 0xE0) {
-        pos += 2;
-      } else if (byteValue < 0xF0) {
-        pos += 3;
-      } else if (byteValue < 0xF8) {
-        pos += 4;
+
+    //set ASCII (<= 127 chars)
+    for (; len < length && len < truncateLen && data[pos] >= 0; ) {
+      len++;
+      pos++;
+    }
+
+    //multi-bytes UTF-8
+    while (pos < offset + length && len < truncateLen) {
+      byte firstByte = data[pos++];
+      if (firstByte < 0) {
+        if (firstByte >> 5 != -2 || (firstByte & 30) == 0) {
+          if (firstByte >> 4 == -2) {
+            if (pos + 1 < offset + length) {
+              pos += 2;
+              len++;
+            } else {
+              throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+            }
+          } else if (firstByte >> 3 != -2) {
+            throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+          } else if (pos + 2 < offset + length) {
+            if (len + 2 < truncateLen) {
+              pos += 3;
+              len += 2;
+            } else {
+              //truncation will result in bad UTF-8 String
+              pos += 1;
+              len = truncateLen;
+            }
+          } else {
+            throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+          }
+        } else {
+          pos++;
+          len++;
+        }
       } else {
-        throw new UncheckedIOException("invalid UTF8", new CharacterCodingException());
+        len++;
       }
     }
     length = pos - offset;

src/test/java/org/mariadb/jdbc/BlobTest.java

@@ -310,6 +310,48 @@ public void testClob3() throws Exception {
     assertEquals("Øhello", result);
   }
 
+  @Test
+  public void clobLength() throws Exception {
+    Statement stmt = sharedConnection.createStatement();
+    try (ResultSet rs = stmt
+        .executeQuery("SELECT 'ab$c', 'ab¢c', 'abहc', 'ab\uD801\uDC37c', 'ab𐍈c' from dual")) {
+      while (rs.next()) {
+
+        Clob clob1 = rs.getClob(1);
+        Clob clob2 = rs.getClob(2);
+        Clob clob3 = rs.getClob(3);
+        Clob clob4 = rs.getClob(4);
+        Clob clob5 = rs.getClob(5);
+
+        assertEquals(4, clob1.length());
+        assertEquals(4, clob2.length());
+        assertEquals(4, clob3.length());
+        assertEquals(5, clob4.length());
+        assertEquals(5, clob5.length());
+
+        clob1.truncate(3);
+        clob2.truncate(3);
+        clob3.truncate(3);
+        clob4.truncate(3);
+        clob5.truncate(3);
+
+        assertEquals(3, clob1.length());
+        assertEquals(3, clob2.length());
+        assertEquals(3, clob3.length());
+        assertEquals(3, clob4.length());
+        assertEquals(3, clob5.length());
+
+        assertEquals("ab$", clob1.getSubString(1, 3));
+        assertEquals("ab¢", clob2.getSubString(1, 3));
+        assertEquals("abह", clob3.getSubString(1, 3));
+        assertEquals("ab�", clob4.getSubString(1, 3));
+        assertEquals("ab�", clob5.getSubString(1, 3));
+      }
+    }
+  }
+
+
+
   @Test
   public void testBlob() throws SQLException, IOException {
     PreparedStatement stmt = sharedConnection