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Core barcode encoding/decoding library
/*
* 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;
import java.nio.charset.Charset;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.StandardCharsets;
import java.nio.charset.UnsupportedCharsetException;
import java.util.ArrayList;
import java.util.List;
/**
* Set of CharsetEncoders for a given input string
*
* Invariants:
* - The list contains only encoders from CharacterSetECI (list is shorter then the list of encoders available on
* the platform for which ECI values are defined).
* - The list contains encoders at least one encoder for every character in the input.
* - The first encoder in the list is always the ISO-8859-1 encoder even of no character in the input can be encoded
* by it.
* - If the input contains a character that is not in ISO-8859-1 then the last two entries in the list will be the
* UTF-8 encoder and the UTF-16BE encoder.
*
* @author Alex Geller
*/
public final class ECIEncoderSet {
// List of encoders that potentially encode characters not in ISO-8859-1 in one byte.
private static final List ENCODERS = new ArrayList<>();
static {
String[] names = { "IBM437",
"ISO-8859-2",
"ISO-8859-3",
"ISO-8859-4",
"ISO-8859-5",
"ISO-8859-6",
"ISO-8859-7",
"ISO-8859-8",
"ISO-8859-9",
"ISO-8859-10",
"ISO-8859-11",
"ISO-8859-13",
"ISO-8859-14",
"ISO-8859-15",
"ISO-8859-16",
"windows-1250",
"windows-1251",
"windows-1252",
"windows-1256",
"Shift_JIS" };
for (String name : names) {
if (CharacterSetECI.getCharacterSetECIByName(name) != null) {
try {
ENCODERS.add(Charset.forName(name).newEncoder());
} catch (UnsupportedCharsetException e) {
// continue
}
}
}
}
private final CharsetEncoder[] encoders;
private final int priorityEncoderIndex;
/**
* Constructs an encoder set
*
* @param stringToEncode the string that needs to be encoded
* @param priorityCharset The preferred {@link Charset} or null.
* @param fnc1 fnc1 denotes the character in the input that represents the FNC1 character or -1 for a non-GS1 bar
* code. When specified, it is considered an error to pass it as argument to the methods canEncode() or encode().
*/
public ECIEncoderSet(String stringToEncode, Charset priorityCharset, int fnc1) {
List neededEncoders = new ArrayList<>();
//we always need the ISO-8859-1 encoder. It is the default encoding
neededEncoders.add(StandardCharsets.ISO_8859_1.newEncoder());
boolean needUnicodeEncoder = priorityCharset != null && priorityCharset.name().startsWith("UTF");
//Walk over the input string and see if all characters can be encoded with the list of encoders
for (int i = 0; i < stringToEncode.length(); i++) {
boolean canEncode = false;
for (CharsetEncoder encoder : neededEncoders) {
char c = stringToEncode.charAt(i);
if (c == fnc1 || encoder.canEncode(c)) {
canEncode = true;
break;
}
}
if (!canEncode) {
//for the character at position i we don't yet have an encoder in the list
for (CharsetEncoder encoder : ENCODERS) {
if (encoder.canEncode(stringToEncode.charAt(i))) {
//Good, we found an encoder that can encode the character. We add him to the list and continue scanning
//the input
neededEncoders.add(encoder);
canEncode = true;
break;
}
}
}
if (!canEncode) {
//The character is not encodeable by any of the single byte encoders so we remember that we will need a
//Unicode encoder.
needUnicodeEncoder = true;
}
}
if (neededEncoders.size() == 1 && !needUnicodeEncoder) {
//the entire input can be encoded by the ISO-8859-1 encoder
encoders = new CharsetEncoder[] { neededEncoders.get(0) };
} else {
// we need more than one single byte encoder or we need a Unicode encoder.
// In this case we append a UTF-8 and UTF-16 encoder to the list
encoders = new CharsetEncoder[neededEncoders.size() + 2];
int index = 0;
for (CharsetEncoder encoder : neededEncoders) {
encoders[index++] = encoder;
}
encoders[index] = StandardCharsets.UTF_8.newEncoder();
encoders[index + 1] = StandardCharsets.UTF_16BE.newEncoder();
}
//Compute priorityEncoderIndex by looking up priorityCharset in encoders
int priorityEncoderIndexValue = -1;
if (priorityCharset != null) {
for (int i = 0; i < encoders.length; i++) {
if (encoders[i] != null && priorityCharset.name().equals(encoders[i].charset().name())) {
priorityEncoderIndexValue = i;
break;
}
}
}
priorityEncoderIndex = priorityEncoderIndexValue;
//invariants
assert encoders[0].charset().equals(StandardCharsets.ISO_8859_1);
}
public int length() {
return encoders.length;
}
public String getCharsetName(int index) {
assert index < length();
return encoders[index].charset().name();
}
public Charset getCharset(int index) {
assert index < length();
return encoders[index].charset();
}
public int getECIValue(int encoderIndex) {
return CharacterSetECI.getCharacterSetECI(encoders[encoderIndex].charset()).getValue();
}
/*
* returns -1 if no priority charset was defined
*/
public int getPriorityEncoderIndex() {
return priorityEncoderIndex;
}
public boolean canEncode(char c, int encoderIndex) {
assert encoderIndex < length();
CharsetEncoder encoder = encoders[encoderIndex];
return encoder.canEncode("" + c);
}
public byte[] encode(char c, int encoderIndex) {
assert encoderIndex < length();
CharsetEncoder encoder = encoders[encoderIndex];
assert encoder.canEncode("" + c);
return ("" + c).getBytes(encoder.charset());
}
public byte[] encode(String s, int encoderIndex) {
assert encoderIndex < length();
CharsetEncoder encoder = encoders[encoderIndex];
return s.getBytes(encoder.charset());
}
}
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