Simplified pieces of code (#601)

* Simplify code in bit-twiddling methods, using APIs introduced in Java 5.

* Align code by adjusting whitespace and adding `+0`.

* Convert qrcode DataMask to enum to reduce source code size, which shouldn't change behavior.

* Simplify lists of character constants using string initializer instead of array.

* Remove redundant `+ 0` operations from a recent change.

* Delete the function DataMask.forReference() and inline the logic into all its callers.

core/src/main/java/com/google/zxing/pdf417/decoder/DecodedBitStreamParser.java

@@ -64,15 +64,11 @@ final class DecodedBitStreamParser {
   private static final int PS = 29;
   private static final int PAL = 29;
 
-  private static final char[] PUNCT_CHARS = {
+  private static final char[] PUNCT_CHARS =
-      ';', '<', '>', '@', '[', '\\', ']', '_', '`', '~', '!',
+      ";<>@[\\]_`~!\r\t,:\n-.$/\"|*()?{}'".toCharArray();
-      '\r', '\t', ',', ':', '\n', '-', '.', '$', '/', '"', '|', '*',
-      '(', ')', '?', '{', '}', '\''};
 
-  private static final char[] MIXED_CHARS = {
+  private static final char[] MIXED_CHARS =
-      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '&',
+      "0123456789&\r\t,:#-.$/+%*=^".toCharArray();
-      '\r', '\t', ',', ':', '#', '-', '.', '$', '/', '+', '%', '*',
-      '=', '^'};
 
   private static final Charset DEFAULT_ENCODING = Charset.forName("ISO-8859-1");
 

core/src/main/java/com/google/zxing/qrcode/decoder/BitMatrixParser.java

@@ -157,7 +157,7 @@ final class BitMatrixParser {
 
     // Get the data mask for the format used in this QR Code. This will exclude
     // some bits from reading as we wind through the bit matrix.
-    DataMask dataMask = DataMask.forReference(formatInfo.getDataMask());
+    DataMask dataMask = DataMask.values()[formatInfo.getDataMask()];
     int dimension = bitMatrix.getHeight();
     dataMask.unmaskBitMatrix(bitMatrix, dimension);
 
@@ -211,7 +211,7 @@ final class BitMatrixParser {
     if (parsedFormatInfo == null) {
       return; // We have no format information, and have no data mask
     }
-    DataMask dataMask = DataMask.forReference(parsedFormatInfo.getDataMask());
+    DataMask dataMask = DataMask.values()[parsedFormatInfo.getDataMask()];
     int dimension = bitMatrix.getHeight();
     dataMask.unmaskBitMatrix(bitMatrix, dimension);
   }

core/src/main/java/com/google/zxing/qrcode/decoder/DataMask.java

@@ -29,24 +29,96 @@ import com.google.zxing.common.BitMatrix;
  *
  * @author Sean Owen
  */
-abstract class DataMask {
+enum DataMask {
 
   /**
    * See ISO 18004:2006 6.8.1
    */
-  private static final DataMask[] DATA_MASKS = {
+
-      new DataMask000(),
+  /**
-      new DataMask001(),
+   * 000: mask bits for which (x + y) mod 2 == 0
-      new DataMask010(),
+   */
-      new DataMask011(),
+  DATA_MASK_000() {
-      new DataMask100(),
+    @Override
-      new DataMask101(),
+    boolean isMasked(int i, int j) {
-      new DataMask110(),
+      return ((i + j) & 0x01) == 0;
-      new DataMask111(),
+    }
+  },
+
+  /**
+   * 001: mask bits for which x mod 2 == 0
+   */
+  DATA_MASK_001() {
+    @Override
+    boolean isMasked(int i, int j) {
+      return (i & 0x01) == 0;
+    }
+  },
+
+  /**
+   * 010: mask bits for which y mod 3 == 0
+   */
+  DATA_MASK_010() {
+    @Override
+    boolean isMasked(int i, int j) {
+      return j % 3 == 0;
+    }
+  },
+
+  /**
+   * 011: mask bits for which (x + y) mod 3 == 0
+   */
+  DATA_MASK_011() {
+    @Override
+    boolean isMasked(int i, int j) {
+      return (i + j) % 3 == 0;
+    }
+  },
+
+  /**
+   * 100: mask bits for which (x/2 + y/3) mod 2 == 0
+   */
+  DATA_MASK_100() {
+    @Override
+    boolean isMasked(int i, int j) {
+      return (((i / 2) + (j /3)) & 0x01) == 0;
+    }
+  },
+
+  /**
+   * 101: mask bits for which xy mod 2 + xy mod 3 == 0
+   */
+  DATA_MASK_101() {
+    @Override
+    boolean isMasked(int i, int j) {
+      int temp = i * j;
+      return (temp & 0x01) + (temp % 3) == 0;
+    }
+  },
+
+  /**
+   * 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0
+   */
+  DATA_MASK_110() {
+    @Override
+    boolean isMasked(int i, int j) {
+      int temp = i * j;
+      return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
+    }
+  },
+
+  /**
+   * 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0
+   */
+  DATA_MASK_111() {
+    @Override
+    boolean isMasked(int i, int j) {
+      return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
+    }
   };
 
-  private DataMask() {
+  // End of enum constants.
-  }
+
 
   /**
    * <p>Implementations of this method reverse the data masking process applied to a QR Code and
@@ -67,97 +139,4 @@ abstract class DataMask {
 
   abstract boolean isMasked(int i, int j);
 
-  /**
-   * @param reference a value between 0 and 7 indicating one of the eight possible
-   * data mask patterns a QR Code may use
-   * @return DataMask encapsulating the data mask pattern
-   */
-  static DataMask forReference(int reference) {
-    if (reference < 0 || reference > 7) {
-      throw new IllegalArgumentException();
-    }
-    return DATA_MASKS[reference];
-  }
-
-  /**
-   * 000: mask bits for which (x + y) mod 2 == 0
-   */
-  private static final class DataMask000 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      return ((i + j) & 0x01) == 0;
-    }
-  }
-
-  /**
-   * 001: mask bits for which x mod 2 == 0
-   */
-  private static final class DataMask001 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      return (i & 0x01) == 0;
-    }
-  }
-
-  /**
-   * 010: mask bits for which y mod 3 == 0
-   */
-  private static final class DataMask010 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      return j % 3 == 0;
-    }
-  }
-
-  /**
-   * 011: mask bits for which (x + y) mod 3 == 0
-   */
-  private static final class DataMask011 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      return (i + j) % 3 == 0;
-    }
-  }
-
-  /**
-   * 100: mask bits for which (x/2 + y/3) mod 2 == 0
-   */
-  private static final class DataMask100 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      return (((i / 2) + (j /3)) & 0x01) == 0;
-    }
-  }
-
-  /**
-   * 101: mask bits for which xy mod 2 + xy mod 3 == 0
-   */
-  private static final class DataMask101 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      int temp = i * j;
-      return (temp & 0x01) + (temp % 3) == 0;
-    }
-  }
-
-  /**
-   * 110: mask bits for which (xy mod 2 + xy mod 3) mod 2 == 0
-   */
-  private static final class DataMask110 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      int temp = i * j;
-      return (((temp & 0x01) + (temp % 3)) & 0x01) == 0;
-    }
-  }
-
-  /**
-   * 111: mask bits for which ((x+y)mod 2 + xy mod 3) mod 2 == 0
-   */
-  private static final class DataMask111 extends DataMask {
-    @Override
-    boolean isMasked(int i, int j) {
-      return ((((i + j) & 0x01) + ((i * j) % 3)) & 0x01) == 0;
-    }
-  }
 }

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

@@ -42,12 +42,8 @@ final class DecodedBitStreamParser {
   /**
    * See ISO 18004:2006, 6.4.4 Table 5
    */
-  private static final char[] ALPHANUMERIC_CHARS = {
+  private static final char[] ALPHANUMERIC_CHARS =
-      '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B',
+      "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ $%*+-./:".toCharArray();
-      'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N',
-      'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
-      ' ', '$', '%', '*', '+', '-', '.', '/', ':'
-  };
   private static final int GB2312_SUBSET = 1;
 
   private DecodedBitStreamParser() {

core/src/main/java/com/google/zxing/qrcode/decoder/FormatInformation.java

@@ -66,12 +66,6 @@ final class FormatInformation {
       {0x2BED, 0x1F},
   };
 
-  /**
-   * Offset i holds the number of 1 bits in the binary representation of i
-   */
-  private static final int[] BITS_SET_IN_HALF_BYTE =
-      {0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4};
-
   private final ErrorCorrectionLevel errorCorrectionLevel;
   private final byte dataMask;
 
@@ -83,17 +77,7 @@ final class FormatInformation {
   }
 
   static int numBitsDiffering(int a, int b) {
-    a ^= b; // a now has a 1 bit exactly where its bit differs with b's
+    return Integer.bitCount(a ^ b);
-    // Count bits set quickly with a series of lookups:
-    return
-        BITS_SET_IN_HALF_BYTE[a & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>>  4) & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>>  8) & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>> 12) & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>> 16) & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>> 20) & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>> 24) & 0x0F] +
-        BITS_SET_IN_HALF_BYTE[(a >>> 28) & 0x0F];
   }
 
   /**

core/src/main/java/com/google/zxing/qrcode/encoder/MaskUtil.java

@@ -77,23 +77,23 @@ final class MaskUtil {
         byte[] arrayY = array[y];  // We can at least optimize this access
         if (x + 6 < width &&
             arrayY[x] == 1 &&
-            arrayY[x +  1] == 0 &&
+            arrayY[x + 1] == 0 &&
-            arrayY[x +  2] == 1 &&
+            arrayY[x + 2] == 1 &&
-            arrayY[x +  3] == 1 &&
+            arrayY[x + 3] == 1 &&
-            arrayY[x +  4] == 1 &&
+            arrayY[x + 4] == 1 &&
-            arrayY[x +  5] == 0 &&
+            arrayY[x + 5] == 0 &&
-            arrayY[x +  6] == 1 &&
+            arrayY[x + 6] == 1 &&
             (isWhiteHorizontal(arrayY, x - 4, x) || isWhiteHorizontal(arrayY, x + 7, x + 11))) {
           numPenalties++;
         }
         if (y + 6 < height &&
-            array[y][x] == 1  &&
+            array[y][x] == 1 &&
-            array[y +  1][x] == 0  &&
+            array[y + 1][x] == 0 &&
-            array[y +  2][x] == 1  &&
+            array[y + 2][x] == 1 &&
-            array[y +  3][x] == 1  &&
+            array[y + 3][x] == 1 &&
-            array[y +  4][x] == 1  &&
+            array[y + 4][x] == 1 &&
-            array[y +  5][x] == 0  &&
+            array[y + 5][x] == 0 &&
-            array[y +  6][x] == 1 &&
+            array[y + 6][x] == 1 &&
             (isWhiteVertical(array, x, y - 4, y) || isWhiteVertical(array, x, y + 7, y + 11))) {
           numPenalties++;
         }

core/src/main/java/com/google/zxing/qrcode/encoder/MatrixUtil.java

@@ -271,12 +271,7 @@ final class MatrixUtil {
   // - findMSBSet(1) => 1
   // - findMSBSet(255) => 8
   static int findMSBSet(int value) {
-    int numDigits = 0;
+    return 32 - Integer.numberOfLeadingZeros(value);
-    while (value != 0) {
-      value >>>= 1;
-      ++numDigits;
-    }
-    return numDigits;
   }
 
   // Calculate BCH (Bose-Chaudhuri-Hocquenghem) code for "value" using polynomial "poly". The BCH

core/src/test/java/com/google/zxing/qrcode/decoder/DataMaskTestCase.java

@@ -106,7 +106,7 @@ public final class DataMaskTestCase extends Assert {
   }
 
   private static void testMaskAcrossDimensions(int reference, MaskCondition condition) {
-    DataMask mask = DataMask.forReference(reference);
+    DataMask mask = DataMask.values()[reference];
     for (int version = 1; version <= 40; version++) {
       int dimension = 17 + 4 * version;
       testMask(mask, dimension, condition);

core/src/test/java/com/google/zxing/qrcode/encoder/MaskUtilTestCase.java

@@ -192,7 +192,7 @@ public final class MaskUtilTestCase extends Assert {
       {1, 0, 1, 0, 1, 0},
       {0, 1, 0, 1, 0, 1},
     };
-    assertTrue(TestGetDataMaskBitInternal(0,  mask0));
+    assertTrue(TestGetDataMaskBitInternal(0, mask0));
     int[][] mask1 = {
       {1, 1, 1, 1, 1, 1},
       {0, 0, 0, 0, 0, 0},
@@ -201,7 +201,7 @@ public final class MaskUtilTestCase extends Assert {
       {1, 1, 1, 1, 1, 1},
       {0, 0, 0, 0, 0, 0},
     };
-    assertTrue(TestGetDataMaskBitInternal(1,  mask1));
+    assertTrue(TestGetDataMaskBitInternal(1, mask1));
     int[][] mask2 = {
       {1, 0, 0, 1, 0, 0},
       {1, 0, 0, 1, 0, 0},