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Core barcode encoding/decoding library
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/*
 * 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);
}