My BitVector implementation was totally buggy. I rewrote a lot of it and ported the test case, which now passes.

Now I'm tracking down an assertion in Encoder.InterleaveWithECBytes().

git-svn-id: https://zxing.googlecode.com/svn/trunk@717 59b500cc-1b3d-0410-9834-0bbf25fbcc57

core/src/com/google/zxing/qrcode/encoder/BitVector.java

@@ -27,24 +27,22 @@ package com.google.zxing.qrcode.encoder;
 public final class BitVector {
 
   private int sizeInBits;
-  private int bytePosition;
   private byte[] array;
 
   // For efficiency, start out with some room to work.
-  private static final int DEFAULT_SIZE_IN_BITS = 32 * 8;
+  private static final int DEFAULT_SIZE_IN_BYTES = 32;
 
   public BitVector() {
-    sizeInBits = DEFAULT_SIZE_IN_BITS;
-    bytePosition = 0;
-    array = new byte[DEFAULT_SIZE_IN_BITS / 8];
+    sizeInBits = 0;
+    array = new byte[DEFAULT_SIZE_IN_BYTES];
   }
 
   // Return the bit value at "index".
   public int at(final int index) {
     Debug.DCHECK_LE(0, index);
     Debug.DCHECK_LT(index, sizeInBits);
-    final int value = array[index / 8];
-    return (value >> (7 - (index % 8))) & 1;
+    final int value = array[index >> 3] & 0xff;
+    return (value >> (7 - (index & 0x7))) & 1;
   }
 
   // Return the number of bits in the bit vector.
@@ -53,20 +51,23 @@ public final class BitVector {
   }
 
   // Return the number of bytes in the bit vector.
+  // JAVAPORT: I would have made this ((sizeInBits + 7) >> 3), but apparently users of this class
+  // depend on the number of bytes being rounded down. I don't see how that works though.
   public int num_bytes() {
-    return sizeInBits / 8;
+    return sizeInBits >> 3;
   }
 
   // Append one bit to the bit vector.
   public void AppendBit(final int bit) {
     Debug.DCHECK(bit == 0 || bit == 1);
-    final int num_bits_in_last_byte = sizeInBits % 8;
+    final int num_bits_in_last_byte = sizeInBits & 0x7;
     // We'll expand array if we don't have bits in the last byte.
     if (num_bits_in_last_byte == 0) {
       appendByte(0);
+      sizeInBits -= 8;
     }
     // Modify the last byte.
-    array[array.length - 1] |= (bit << (7 - num_bits_in_last_byte));
+    array[sizeInBits >> 3] |= (bit << (7 - num_bits_in_last_byte));
     ++sizeInBits;
   }
 
@@ -82,10 +83,9 @@ public final class BitVector {
     int num_bits_left = num_bits;
     while (num_bits_left > 0) {
       // Optimization for byte-oriented appending.
-      if (sizeInBits % 8 == 0 && num_bits_left >= 8) {
+      if ((sizeInBits & 0x7) == 0 && num_bits_left >= 8) {
         final int newByte = (value >> (num_bits_left - 8)) & 0xff;
         appendByte(newByte);
-        sizeInBits += 8;
         num_bits_left -= 8;
       } else {
         final int bit = (value >> (num_bits_left - 1)) & 1;
@@ -106,7 +106,8 @@ public final class BitVector {
   // Modify the bit vector by XOR'ing with "other"
   public void XOR(final BitVector other) {
     Debug.DCHECK_EQ(sizeInBits, other.size());
-    for (int i = 0; i < array.length; ++i) {
+    int sizeInBytes = (sizeInBits + 7) >> 3;
+    for (int i = 0; i < sizeInBytes; ++i) {
       // The last byte could be incomplete (i.e. not have 8 bits in
       // it) but there is no problem since 0 XOR 0 == 0.
       array[i] ^= other.array[i];
@@ -128,16 +129,22 @@ public final class BitVector {
     return result.toString();
   }
 
+  // Callers should not assume that array.length is the exact number of bytes needed to hold
+  // sizeInBits - it will typically be larger for efficiency.
+  public byte[] getArray() {
+    return array;
+  }
+
   // Add a new byte to the end, possibly reallocating and doubling the size of the array if we've
   // run out of room.
   private void appendByte(int value) {
-    if (bytePosition >= array.length) {
+    if ((sizeInBits >> 3) == array.length) {
       byte[] newArray = new byte[array.length * 2];
       System.arraycopy(array, 0, newArray, 0, array.length);
       array = newArray;
     }
-    array[bytePosition] = (byte) value;
-    bytePosition++;
+    array[sizeInBits >> 3] = (byte) value;
+    sizeInBits += 8;
   }
 
 }

core/src/com/google/zxing/qrcode/encoder/Debug.java

@@ -25,11 +25,11 @@ package com.google.zxing.qrcode.encoder;
 public class Debug {
 
   public static void LOG_ERROR(String message) {
-    // TODO: Implement
+    throw new IllegalStateException(message);
   }
 
   public static void LOG_INFO(String message) {
-    // TODO: Implement
+    throw new IllegalStateException(message);
   }
 
   public static void DCHECK(boolean condition) {

core/src/com/google/zxing/qrcode/encoder/Encoder.java

@@ -613,7 +613,7 @@ private static final ECPolyInfo kECPolynomials[] = {
       return true;
     }
     Debug.LOG_ERROR("Interleaving error: " + num_total_bytes + " and " + result.num_bytes() +
-        "differ.");
+        " differ.");
     return false;
   }
 

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

@@ -0,0 +1,173 @@
+/*
+ * Copyright 2008 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.qrcode.encoder;
+
+import junit.framework.TestCase;
+
+/**
+ * @author satorux@google.com (Satoru Takabayashi) - creator
+ * @author dswitkin@google.com (Daniel Switkin) - ported from C++
+ */
+public class BitVectorTestCase extends TestCase {
+
+  private static int getUnsignedByte(BitVector v, int index) {
+    return v.getArray()[index] & 0xff;
+  }
+
+  public void testAppendBit() {
+    BitVector v = new BitVector();
+    assertEquals(0, v.num_bytes());
+    // 1
+    v.AppendBit(1);
+    assertEquals(1, v.size());
+    assertEquals(0x80, getUnsignedByte(v, 0));
+    // 10
+    v.AppendBit(0);
+    assertEquals(2, v.size());
+    assertEquals(0x80, getUnsignedByte(v, 0));
+    // 101
+    v.AppendBit(1);
+    assertEquals(3, v.size());
+    assertEquals(0xa0, getUnsignedByte(v, 0));
+    // 1010
+    v.AppendBit(0);
+    assertEquals(4, v.size());
+    assertEquals(0xa0, getUnsignedByte(v, 0));
+    // 10101
+    v.AppendBit(1);
+    assertEquals(5, v.size());
+    assertEquals(0xa8, getUnsignedByte(v, 0));
+    // 101010
+    v.AppendBit(0);
+    assertEquals(6, v.size());
+    assertEquals(0xa8, getUnsignedByte(v, 0));
+    // 1010101
+    v.AppendBit(1);
+    assertEquals(7, v.size());
+    assertEquals(0xaa, getUnsignedByte(v, 0));
+    // 10101010
+    v.AppendBit(0);
+    assertEquals(8, v.size());
+    assertEquals(0xaa, getUnsignedByte(v, 0));
+    // 10101010 1
+    v.AppendBit(1);
+    assertEquals(9, v.size());
+    assertEquals(0xaa, getUnsignedByte(v, 0));
+    assertEquals(0x80, getUnsignedByte(v, 1));
+    // 10101010 10
+    v.AppendBit(0);
+    assertEquals(10, v.size());
+    assertEquals(0xaa, getUnsignedByte(v, 0));
+    assertEquals(0x80, getUnsignedByte(v, 1));
+  }
+
+  public void testAppendBits() {
+    {
+      BitVector v = new BitVector();
+      v.AppendBits(0x1, 1);
+      assertEquals(1, v.size());
+      assertEquals(0x80, getUnsignedByte(v, 0));
+    }
+    {
+      BitVector v = new BitVector();
+      v.AppendBits(0xff, 8);
+      assertEquals(8, v.size());
+      assertEquals(0xff, getUnsignedByte(v, 0));
+    }
+    {
+      BitVector v = new BitVector();
+      v.AppendBits(0xff7, 12);
+      assertEquals(12, v.size());
+      assertEquals(0xff, getUnsignedByte(v, 0));
+      assertEquals(0x70, getUnsignedByte(v, 1));
+    }
+  }
+
+  public void testNumBytes() {
+    BitVector v = new BitVector();
+    assertEquals(0, v.num_bytes());
+    v.AppendBit(0);
+    assertEquals(0, v.num_bytes());
+    v.AppendBits(0, 7);
+    assertEquals(1, v.num_bytes());
+    v.AppendBits(0, 8);
+    assertEquals(2, v.num_bytes());
+  }
+
+  public void testAppendBitVector() {
+    BitVector v1 = new BitVector();
+    v1.AppendBits(0xbe, 8);
+    BitVector v2 = new BitVector();
+    v2.AppendBits(0xef, 8);
+    v1.AppendBitVector(v2);
+    // beef = 1011 1110 1110 1111
+    assertEquals("1011111011101111", v1.toString());
+  }
+
+  public void testXOR() {
+    {
+      BitVector v1 = new BitVector();
+      v1.AppendBits(0x5555aaaa, 32);
+      BitVector v2 = new BitVector();
+      v2.AppendBits(0xaaaa5555, 32);
+      v1.XOR(v2);
+      assertEquals(0xff, getUnsignedByte(v1, 0));
+      assertEquals(0xff, getUnsignedByte(v1, 1));
+      assertEquals(0xff, getUnsignedByte(v1, 2));
+      assertEquals(0xff, getUnsignedByte(v1, 3));
+    }
+    {
+      BitVector v1 = new BitVector();
+      v1.AppendBits(0x2a, 7);  // 010 1010
+      BitVector v2 = new BitVector();
+      v2.AppendBits(0x55, 7);  // 101 0101
+      v1.XOR(v2);
+      assertEquals(0xfe, getUnsignedByte(v1, 0));  // 1111 1110
+    }
+  }
+
+  public void testAt() {
+    BitVector v = new BitVector();
+    v.AppendBits(0xdead, 16);  // 1101 1110 1010 1101
+    assertEquals(1, v.at(0));
+    assertEquals(1, v.at(1));
+    assertEquals(0, v.at(2));
+    assertEquals(1, v.at(3));
+
+    assertEquals(1, v.at(4));
+    assertEquals(1, v.at(5));
+    assertEquals(1, v.at(6));
+    assertEquals(0, v.at(7));
+
+    assertEquals(1, v.at(8));
+    assertEquals(0, v.at(9));
+    assertEquals(1, v.at(10));
+    assertEquals(0, v.at(11));
+
+    assertEquals(1, v.at(12));
+    assertEquals(1, v.at(13));
+    assertEquals(0, v.at(14));
+    assertEquals(1, v.at(15));
+  }
+
+  public void testToString() {
+    BitVector v = new BitVector();
+    v.AppendBits(0xdead, 16);  // 1101 1110 1010 1101
+    assertEquals("1101111010101101", v.toString());
+  }
+
+}