Add support for multi-eci encoding for PDF417 (#1506)

* - Added multi-eci encoding for PDF417
- Fixed issue that the PDF417 decoder incorrectly decoded input with a leading ECI and no explicit latch to TEXT encoding

core/src/main/java/com/google/zxing/EncodeHintType.java

@@ -103,6 +103,16 @@ public enum EncodeHintType {
    */
   PDF417_DIMENSIONS,
 
+  /**
+   * Specifies whether to automatically insert ECIs when encoding PDF417 (type {@link Boolean}, or "true" or "false"
+   * {@link String} value). 
+   * Please note that in that case, the most compact character encoding is chosen for characters in
+   * the input that are not in the ISO-8859-1 character set. Based on experience, some scanners do not
+   * support encodings like cp-1256 (Arabic). In such cases the encoding can be forced to UTF-8 by
+   * means of the {@link #CHARACTER_SET} encoding hint.
+   */
+  PDF417_AUTO_ECI,
+
   /**
    * Specifies the required number of layers for an Aztec code.
    * A negative number (-1, -2, -3, -4) specifies a compact Aztec code.

core/src/main/java/com/google/zxing/common/ECIInput.java

@@ -0,0 +1,107 @@
+/*
+ * Copyright 2021 ZXing authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.google.zxing.common;
+
+/**
+ * Interface to navigate a sequence of ECIs and bytes.
+ *
+ * @author Alex Geller
+ */
+public interface ECIInput {
+
+ /**
+  * Returns the length of this input.  The length is the number
+  * of {@code byte}s in or ECIs in the sequence.
+  *
+  * @return  the number of {@code char}s in this sequence
+  */
+  int length();
+
+ /**
+  * Returns the {@code byte} value at the specified index.  An index ranges from zero
+  * to {@code length() - 1}.  The first {@code byte} value of the sequence is at
+  * index zero, the next at index one, and so on, as for array
+  * indexing.
+  *
+  * @param   index the index of the {@code byte} value to be returned
+  *
+  * @return  the specified {@code byte} value as character or the FNC1 character
+  *
+  * @throws  IndexOutOfBoundsException
+  *          if the {@code index} argument is negative or not less than
+  *          {@code length()}
+  * @throws  IllegalArgumentException
+  *          if the value at the {@code index} argument is an ECI (@see #isECI)
+  */
+  char charAt(int index);
+
+ /**
+  * Returns a {@code CharSequence} that is a subsequence of this sequence.
+  * The subsequence starts with the {@code char} value at the specified index and
+  * ends with the {@code char} value at index {@code end - 1}.  The length
+  * (in {@code char}s) of the
+  * returned sequence is {@code end - start}, so if {@code start == end}
+  * then an empty sequence is returned.
+  *
+  * @param   start   the start index, inclusive
+  * @param   end     the end index, exclusive
+  *
+  * @return  the specified subsequence
+  *
+  * @throws  IndexOutOfBoundsException
+  *          if {@code start} or {@code end} are negative,
+  *          if {@code end} is greater than {@code length()},
+  *          or if {@code start} is greater than {@code end}
+  * @throws  IllegalArgumentException
+  *          if a value in the range {@code start}-{@code end} is an ECI (@see #isECI)
+  */
+  CharSequence subSequence(int start, int end);
+
+ /**
+  * Determines if a value is an ECI
+  *
+  * @param   index the index of the value
+  *
+  * @return  true if the value at position {@code index} is an ECI
+  *
+  * @throws  IndexOutOfBoundsException
+  *          if the {@code index} argument is negative or not less than
+  *          {@code length()}
+  */
+  boolean isECI(int index);
+
+ /**
+  * Returns the {@code int} ECI value at the specified index.  An index ranges from zero
+  * to {@code length() - 1}.  The first {@code byte} value of the sequence is at
+  * index zero, the next at index one, and so on, as for array
+  * indexing.
+  *
+  * @param   index the index of the {@code int} value to be returned
+  *
+  * @return  the specified {@code int} ECI value. 
+  *          The ECI specified the encoding of all bytes with a higher index until the
+  *          next ECI or until the end of the input if no other ECI follows.
+  *
+  * @throws  IndexOutOfBoundsException
+  *          if the {@code index} argument is negative or not less than
+  *          {@code length()}
+  * @throws  IllegalArgumentException
+  *          if the value at the {@code index} argument is not an ECI (@see #isECI)
+  */
+  int getECIValue(int index);
+  boolean haveNCharacters(int index, int n);
+}