Fix of error in specification ISO/IEC 16022 Second edition Annex P as suggested by Martin Burke of zint (See 68566fefd2/) (#1459)

Quote of Martin's proposed changes to the spec:
The algorithm can be salvaged to be at least sound by making those changes, e.g. by adding to step e):

 "1) If the next character cannot be encoded as X12, switch to ASCII mode and go to step b)."

(and renumbering the following sub-steps). Similarly step f):

"1) If the next character cannot be encoded as EDIFACT, switch to ASCII mode and go to step b)."

core/src/main/java/com/google/zxing/datamatrix/encoder/HighLevelEncoder.java

@@ -193,6 +193,26 @@ public final class HighLevelEncoder {
   }
 
   static int lookAheadTest(CharSequence msg, int startpos, int currentMode) {
+    int newMode = lookAheadTestIntern(msg, startpos, currentMode);
+    if (currentMode == X12_ENCODATION && newMode == X12_ENCODATION) {
+      int endpos = Math.min(startpos + 3, msg.length());
+      for (int i = startpos; i < endpos; i++) {
+        if (!isNativeX12(msg.charAt(i))) {
+          return ASCII_ENCODATION;
+        }
+      }
+    } else if (currentMode == EDIFACT_ENCODATION && newMode == EDIFACT_ENCODATION) {
+      int endpos = Math.min(startpos + 4, msg.length());
+      for (int i = startpos; i < endpos; i++) {
+        if (!isNativeEDIFACT(msg.charAt(i))) {
+          return ASCII_ENCODATION;
+        }
+      }
+    }
+    return newMode;
+  }
+
+  static int lookAheadTestIntern(CharSequence msg, int startpos, int currentMode) {
     if (startpos >= msg.length()) {
       return currentMode;
     }

core/src/test/java/com/google/zxing/datamatrix/encoder/HighLevelEncodeTestCase.java

@@ -353,6 +353,33 @@ public final class HighLevelEncodeTestCase extends Assert {
     assertEquals("240 168 209 77 4 229 45 196 107 77 21 53 5 12 135 192", visualized);
   }
 
+  @Test
+  public void testX12AndEDIFACTSpecErrors() {
+    //X12 encoding error with spec conform float point comparisons in lookAheadTest()
+    String visualized = encodeHighLevel("AAAAAAAAAAA**\u00FCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    assertEquals("230 89 191 89 191 89 191 89 178 56 114 10 243 177 63 89 191 89 191 89 191 89 191 89 191 89 191 89 " +
+        "191 89 191 89 191 254 66 129", visualized);
+    //X12 encoding error with integer comparisons in lookAheadTest()
+    visualized = encodeHighLevel("AAAAAAAAAAAA0+****AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    assertEquals("238 89 191 89 191 89 191 89 191 254 240 194 186 170 170 160 65 4 16 65 4 16 65 4 16 65 4 16 65 4 " +
+        "16 65 4 16 65 4 16 65 124 129 167 62 212 107", visualized);
+    //EDIFACT encoding error with spec conform float point comparisons in lookAheadTest()
+    visualized = encodeHighLevel("AAAAAAAAAAA++++\u00FCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    assertEquals("230 89 191 89 191 89 191 254 66 66 44 44 44 44 235 125 230 89 191 89 191 89 191 89 191 89 191 89 " +
+        "191 89 191 89 191 89 191 89 191 254 129 17 167 62 212 107", visualized);
+    //EDIFACT encoding error with integer comparisons in lookAheadTest()
+    visualized = encodeHighLevel("++++++++++AAa0 0++++++++++++++++++++++++++++++");
+    assertEquals("240 174 186 235 174 186 235 174 176 65 124 98 240 194 12 43 174 186 235 174 186 235 174 186 235 " +
+        "174 186 235 174 186 235 174 186 235 174 186 235 173 240 129 167 62 212 107", visualized);
+    visualized = encodeHighLevel("AAAAAAAAAAAA*+AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    assertEquals("230 89 191 89 191 89 191 89 191 7 170 64 191 89 191 89 191 89 191 89 191 89 191 89 191 89 191 89 " +
+        "191 89 191 66", visualized);
+    visualized = encodeHighLevel("AAAAAAAAAAA*0a0 *AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    assertEquals("230 89 191 89 191 89 191 89 178 56 227 6 228 7 183 89 191 89 191 89 191 89 191 89 191 89 191 89 " +
+        "191 89 191 89 191 254 66 66", visualized);
+
+  }
+
   private static String encodeHighLevel(String msg) {
     CharSequence encoded = HighLevelEncoder.encodeHighLevel(msg);
     //DecodeHighLevel.decode(encoded);