src/java.base/share/classes/java/util/Base64.java

*** 114,125 ****
       * <a href="#mime">MIME</a> type base64 encoding scheme
       * with specified line length and line separators.
       *
       * @param   lineLength
       *          the length of each output line (rounded down to nearest multiple
!      *          of 4). If {@code lineLength <= 0} the output will not be separated
!      *          in lines
       * @param   lineSeparator
       *          the line separator for each output line
       *
       * @return  A Base64 encoder.
       *
--- 114,125 ----
       * <a href="#mime">MIME</a> type base64 encoding scheme
       * with specified line length and line separators.
       *
       * @param   lineLength
       *          the length of each output line (rounded down to nearest multiple
!      *          of 4). If the rounded down line length is not a positive value,
!      *          the output will not be separated in lines
       * @param   lineSeparator
       *          the line separator for each output line
       *
       * @return  A Base64 encoder.
       *
*** 133,146 ****
           for (byte b : lineSeparator) {
               if (base64[b & 0xff] != -1)
                   throw new IllegalArgumentException(
                       "Illegal base64 line separator character 0x" + Integer.toString(b, 16));
           }
           if (lineLength <= 0) {
               return Encoder.RFC4648;
           }
!          return new Encoder(false, lineSeparator, lineLength >> 2 << 2, true);
      }
  
      /**
       * Returns a {@link Decoder} that decodes using the
       * <a href="#basic">Basic</a> type base64 encoding scheme.
--- 133,148 ----
           for (byte b : lineSeparator) {
               if (base64[b & 0xff] != -1)
                   throw new IllegalArgumentException(
                       "Illegal base64 line separator character 0x" + Integer.toString(b, 16));
           }
+          // round down to nearest multiple of 4
+          lineLength &= ~0b11;
           if (lineLength <= 0) {
               return Encoder.RFC4648;
           }
!          return new Encoder(false, lineSeparator, lineLength, true);
      }
  
      /**
       * Returns a {@link Decoder} that decodes using the
       * <a href="#basic">Basic</a> type base64 encoding scheme.