Add support for multiple character-ECIs in data matrix decoder (#1474)

* Added support for multiple character-ECIs

* - Changed from ArrayList<Byte> to ByteArrayOutputStream
- Added blank lines

* Improved performance for the general case (without ECI)

core/src/main/java/com/google/zxing/datamatrix/decoder/DecodedBitStreamParser.java

@@ -19,8 +19,10 @@ package com.google.zxing.datamatrix.decoder;
 import com.google.zxing.FormatException;
 import com.google.zxing.common.BitSource;
 import com.google.zxing.common.DecoderResult;
+import com.google.zxing.common.CharacterSetECI;
 
 import java.nio.charset.StandardCharsets;
+import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
@@ -87,7 +89,7 @@ final class DecodedBitStreamParser {
 
   static DecoderResult decode(byte[] bytes) throws FormatException {
     BitSource bits = new BitSource(bytes);
-    StringBuilder result = new StringBuilder(100);
+    ECIStringBuilder result = new ECIStringBuilder(100);
     StringBuilder resultTrailer = new StringBuilder(0);
     List<byte[]> byteSegments = new ArrayList<>(1);
     Mode mode = Mode.ASCII_ENCODE;
@@ -116,6 +118,7 @@ final class DecodedBitStreamParser {
             decodeBase256Segment(bits, result, byteSegments);
             break;
           case ECI_ENCODE:
+            decodeECISegment(bits, result);
             isECIencoded = true; // ECI detection only, atm continue decoding as ASCII
             break;
           default:
@@ -158,7 +161,7 @@ final class DecodedBitStreamParser {
    * See ISO 16022:2006, 5.2.3 and Annex C, Table C.2
    */
   private static Mode decodeAsciiSegment(BitSource bits,
-                                         StringBuilder result,
+                                         ECIStringBuilder result,
                                          StringBuilder resultTrailer,
                                          Set<Integer> fnc1positions) throws FormatException {
     boolean upperShift = false;
@@ -231,7 +234,7 @@ final class DecodedBitStreamParser {
   /**
    * See ISO 16022:2006, 5.2.5 and Annex C, Table C.1
    */
-  private static void decodeC40Segment(BitSource bits, StringBuilder result, Set<Integer> fnc1positions)
+  private static void decodeC40Segment(BitSource bits, ECIStringBuilder result, Set<Integer> fnc1positions)
       throws FormatException {
     // Three C40 values are encoded in a 16-bit value as
     // (1600 * C1) + (40 * C2) + C3 + 1
@@ -323,7 +326,7 @@ final class DecodedBitStreamParser {
   /**
    * See ISO 16022:2006, 5.2.6 and Annex C, Table C.2
    */
-  private static void decodeTextSegment(BitSource bits, StringBuilder result, Set<Integer> fnc1positions)
+  private static void decodeTextSegment(BitSource bits, ECIStringBuilder result, Set<Integer> fnc1positions)
       throws FormatException {
     // Three Text values are encoded in a 16-bit value as
     // (1600 * C1) + (40 * C2) + C3 + 1
@@ -421,7 +424,7 @@ final class DecodedBitStreamParser {
    * See ISO 16022:2006, 5.2.7
    */
   private static void decodeAnsiX12Segment(BitSource bits,
-                                           StringBuilder result) throws FormatException {
+                                           ECIStringBuilder result) throws FormatException {
     // Three ANSI X12 values are encoded in a 16-bit value as
     // (1600 * C1) + (40 * C2) + C3 + 1
 
@@ -480,7 +483,7 @@ final class DecodedBitStreamParser {
   /**
    * See ISO 16022:2006, 5.2.8 and Annex C Table C.3
    */
-  private static void decodeEdifactSegment(BitSource bits, StringBuilder result) {
+  private static void decodeEdifactSegment(BitSource bits, ECIStringBuilder result) {
     do {
       // If there is only two or less bytes left then it will be encoded as ASCII
       if (bits.available() <= 16) {
@@ -512,7 +515,7 @@ final class DecodedBitStreamParser {
    * See ISO 16022:2006, 5.2.9 and Annex B, B.2
    */
   private static void decodeBase256Segment(BitSource bits,
-                                           StringBuilder result,
+                                           ECIStringBuilder result,
                                            Collection<byte[]> byteSegments)
       throws FormatException {
     // Figure out how long the Base 256 Segment is.
@@ -545,6 +548,36 @@ final class DecodedBitStreamParser {
     result.append(new String(bytes, StandardCharsets.ISO_8859_1));
   }
 
+  /**
+   * See ISO 16022:2007, 5.4.1
+   */
+  private static void decodeECISegment(BitSource bits,
+                                           ECIStringBuilder result)
+      throws FormatException {
+    if (bits.available() < 8) {
+      throw FormatException.getFormatInstance();
+    }
+    int c1 = bits.readBits(8);
+    if (c1 <= 127) {
+      result.appendECI(c1 - 1);
+    }
+    //currently we only support character set ECIs
+    /*} else {
+      if (bits.available() < 8) {
+        throw FormatException.getFormatInstance();
+      }
+      int c2 = bits.readBits(8);
+      if (c1 >= 128 && c1 <= 191) {
+      } else {
+        if (bits.available() < 8) {
+          throw FormatException.getFormatInstance();
+        }
+        int c3 = bits.readBits(8);
+      }
+    }*/
+  }
+
+
   /**
    * See ISO 16022:2006, Annex B, B.2
    */
@@ -555,4 +588,70 @@ final class DecodedBitStreamParser {
     return tempVariable >= 0 ? tempVariable : tempVariable + 256;
   }
 
+  private static final class ECIStringBuilder {
+    private StringBuilder currentBytes;
+    private StringBuilder currentChars;
+    private Charset currentCharset = StandardCharsets.ISO_8859_1;
+    private String result = null;
+    private boolean hadECI = false;
+
+    private ECIStringBuilder(int initialCapacity) {
+      currentBytes = new StringBuilder(initialCapacity);
+    }
+
+    private void append(char value) {
+      currentBytes.append(value);
+    }
+
+    private void append(String value) {
+      currentBytes.append(value);
+    }
+
+    private void append(int value) {
+      currentBytes.append(value);
+    }
+
+    private void appendECI(int value) throws FormatException {
+      encodeCurrentBytesIfAny();
+      CharacterSetECI characterSetECI = CharacterSetECI.getCharacterSetECIByValue(value);
+      if (characterSetECI == null) {
+        throw FormatException.getFormatInstance(new RuntimeException("Unsupported ECI value " + value));
+      }
+      currentCharset = characterSetECI.getCharset();
+    }
+
+    private void encodeCurrentBytesIfAny() {
+      if (!hadECI) {
+        currentChars = currentBytes;
+        currentBytes = new StringBuilder();
+        hadECI = true;
+      } else if (currentBytes.length() > 0) {
+        byte[] bytes = new byte[currentBytes.length()];
+        for (int i = 0; i < bytes.length; i++) {
+          bytes[i] = (byte) (currentBytes.charAt(i) & 0xff);
+        }
+        currentChars.append(new String(bytes, currentCharset));
+        currentBytes.setLength(0);
+      }
+    }
+
+    private void append(StringBuilder value) {
+      encodeCurrentBytesIfAny();
+      currentChars.append(value);
+    }
+
+    /**
+     * returns the length of toString()
+     */
+    public int length() {
+      return toString().length();
+    }
+
+    public String toString() {
+      encodeCurrentBytesIfAny();
+      result = result == null ? currentChars.toString() : result + currentChars.toString();
+      currentChars.setLength(0);
+      return result;
+    }
+  }
 }