move to singleton ReaderException for a bit more performance

git-svn-id: http://zxing.googlecode.com/svn/trunk@714 59b500cc-1b3d-0410-9834-0bbf25fbcc57

bug/src/com/google/zxing/client/bug/AWTImageMonochromeBitmapSource.java

@@ -47,7 +47,7 @@ public AWTImageMonochromeBitmapSource(Image image) throws ReaderException {
     try {
       grabber.grabPixels();
     } catch (InterruptedException ie) {
-      throw new ReaderException("Interrupted while reading pixels");
+      throw ReaderException.getInstance();
     }
   }
 

core/src/com/google/zxing/ReaderException.java

@@ -23,19 +23,25 @@
  *
  * @author Sean Owen
  */
+public final class ReaderException extends Exception {
 
-// TODO: Currently we throw up to 400 ReaderExceptions while scanning a single 240x240 image before
-// rejecting it. This involves a lot of overhead and memory allocation, and affects both performance
-// and latency on continuous scan clients. In the future, we should change all the decoders not to
-// throw exceptions for routine events, like not finding a barcode on a given row. Instead, we
-// should return error codes back to the callers, and simply delete this class. In the mean time, I
-// have altered this class to be as lightweight as possible, by ignoring the exception string, and
-// by disabling the generation of stack traces, which is especially time consuming. These are just
-// temporary measures, pending the big cleanup.
-public final class ReaderException extends java.lang.Throwable {
-
-  public ReaderException(String message) {
-    // Do not pass message to Throwable, let it get optimized out
+  // TODO: Currently we throw up to 400 ReaderExceptions while scanning a single 240x240 image before
+  // rejecting it. This involves a lot of overhead and memory allocation, and affects both performance
+  // and latency on continuous scan clients. In the future, we should change all the decoders not to
+  // throw exceptions for routine events, like not finding a barcode on a given row. Instead, we
+  // should return error codes back to the callers, and simply delete this class. In the mean time, I
+  // have altered this class to be as lightweight as possible, by ignoring the exception string, and
+  // by disabling the generation of stack traces, which is especially time consuming. These are just
+  // temporary measures, pending the big cleanup.
+
+  private static final ReaderException instance = new ReaderException();
+
+  private ReaderException() {
+    // do nothing
+  }
+
+  public static ReaderException getInstance() {
+    return instance;
   }
 
   // Prevent stack traces from being taken

core/src/com/google/zxing/common/BlackPointEstimator.java

@@ -88,7 +88,7 @@ public static int estimate(int[] histogram) throws ReaderException{
     // for 1D formats, which are relatively lenient.
     // We arbitrarily say "close" is "<= 1/16 of the total histogram buckets apart"
     if (secondPeak - firstPeak <= numBuckets >> 4) {
-      throw new ReaderException("Too little dynamic range in luminance");
+      throw ReaderException.getInstance();
     }
 
     // Find a valley between them that is low and closer to the white peak

core/src/com/google/zxing/common/DefaultGridSampler.java

@@ -67,7 +67,7 @@ public BitMatrix sampleGrid(MonochromeBitmapSource image,
         // This results in an ugly runtime exception despite our clever checks above -- can't have that.
         // We could check each point's coordinates but that feels duplicative. We settle for
         // catching and wrapping ArrayIndexOutOfBoundsException.
-        throw new ReaderException(aioobe.toString());
+        throw ReaderException.getInstance();
       }
     }
     return bits;

core/src/com/google/zxing/common/GridSampler.java

@@ -122,7 +122,7 @@ protected static void checkAndNudgePoints(MonochromeBitmapSource image, float[]
       int x = (int) points[offset];
       int y = (int) points[offset + 1];
       if (x < -1 || x > width || y < -1 || y > height) {
-        throw new ReaderException("Transformed point out of bounds at " + x + ',' + y);
+        throw ReaderException.getInstance();
       }
       nudged = false;
       if (x == -1) {
@@ -146,7 +146,7 @@ protected static void checkAndNudgePoints(MonochromeBitmapSource image, float[]
       int x = (int) points[offset];
       int y = (int) points[offset + 1];
       if (x < -1 || x > width || y < -1 || y > height) {
-        throw new ReaderException("Transformed point out of bounds at " + x + ',' + y);
+        throw ReaderException.getInstance();
       }
       nudged = false;
       if (x == -1) {

core/src/com/google/zxing/datamatrix/DataMatrixReader.java

@@ -92,7 +92,7 @@ private static BitMatrix extractPureBits(MonochromeBitmapSource image) throws Re
       borderWidth++;
     }
     if (borderWidth == minDimension) {
-      throw new ReaderException("No black pixels found along diagonal");
+      throw ReaderException.getInstance();
     }
 
     // And then keep tracking across the top-left black module to determine module size
@@ -101,7 +101,7 @@ private static BitMatrix extractPureBits(MonochromeBitmapSource image) throws Re
       moduleEnd++;
     }
     if (moduleEnd == width) {
-      throw new ReaderException("No end to black pixels found along row");
+      throw ReaderException.getInstance();
     }
 
     int moduleSize = moduleEnd - borderWidth;
@@ -112,14 +112,13 @@ private static BitMatrix extractPureBits(MonochromeBitmapSource image) throws Re
     	columnEndOfSymbol--;
     }
     if (columnEndOfSymbol < 0) {
-      throw new ReaderException("Can't find end of bottommost black module");
+      throw ReaderException.getInstance();
     }
     columnEndOfSymbol++;
 
     // Make sure width of barcode is a multiple of module size
     if ((columnEndOfSymbol - borderWidth) % moduleSize != 0) {
-      throw new ReaderException("Bad module size / width: " + moduleSize +
-          " / " + (columnEndOfSymbol - borderWidth));
+      throw ReaderException.getInstance();
     }
     int dimension = (columnEndOfSymbol - borderWidth) / moduleSize;
 
@@ -130,7 +129,7 @@ private static BitMatrix extractPureBits(MonochromeBitmapSource image) throws Re
 
     int sampleDimension = borderWidth + (dimension - 1) * moduleSize;
     if (sampleDimension >= width || sampleDimension >= height) {
-      throw new ReaderException("Estimated pure image size is beyond image boundaries");
+      throw ReaderException.getInstance();
     }
 
     // Now just read off the bits

core/src/com/google/zxing/datamatrix/decoder/BitMatrixParser.java

@@ -35,7 +35,7 @@ final class BitMatrixParser {
   BitMatrixParser(BitMatrix bitMatrix) throws ReaderException {
     int dimension = bitMatrix.getDimension();
     if (dimension < 10 || dimension > 144 || (dimension & 0x01) != 0) {
-      throw new ReaderException("Invalid dimension (" + dimension + ")  Must be 0 mod 2 and >= 10 and <= 144");
+      throw ReaderException.getInstance();
     }
 
     version = readVersion(bitMatrix);
@@ -141,7 +141,7 @@ byte[] readCodewords() throws ReaderException {
     } while ((row < numRows) || (column < numColumns));
 
     if (resultOffset != version.getTotalCodewords()) {
-      throw new ReaderException("Did not read all codewords");
+      throw ReaderException.getInstance();
     }
     return result;
   }

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

@@ -102,7 +102,7 @@ static DecoderResult decode(byte[] bytes) throws ReaderException {
             decodeBase256Segment(bits, result, byteSegments);
             break;
           default:
-            throw new ReaderException("Unsupported mode indicator");
+            throw ReaderException.getInstance();
         }
         mode = ASCII_ENCODE;
       }
@@ -122,7 +122,7 @@ private static int decodeAsciiSegment(BitSource bits, StringBuffer result, Strin
     do {
       int oneByte = bits.readBits(8);
       if (oneByte == 0) {
-	    	throw new ReaderException("0 is an invalid ASCII codeword");
+	    	throw ReaderException.getInstance();
 	    } else if (oneByte <= 128) {  // ASCII data (ASCII value + 1)
 	    	oneByte = upperShift ? (oneByte + 128) : oneByte;
 	    	upperShift = false;
@@ -141,11 +141,11 @@ private static int decodeAsciiSegment(BitSource bits, StringBuffer result, Strin
 	    } else if (oneByte == 231) {  // Latch to Base 256 encodation
 	    	return BASE256_ENCODE;
 	    } else if (oneByte == 232) {  // FNC1
-	    	throw new ReaderException("Currently not supporting FNC1");
+	    	throw ReaderException.getInstance();
 	    } else if (oneByte == 233) {  // Structured Append
-	    	throw new ReaderException("Currently not supporting Structured Append");
+	    	throw ReaderException.getInstance();
 	    } else if (oneByte == 234) {  // Reader Programming
-	    	throw new ReaderException("Currently not supporting Reader Programming");
+	    	throw ReaderException.getInstance();
 	    } else if (oneByte == 235) {  // Upper Shift (shift to Extended ASCII)
 	    	upperShift = true;
 	    } else if (oneByte == 236) {  // 05 Macro
@@ -162,9 +162,9 @@ private static int decodeAsciiSegment(BitSource bits, StringBuffer result, Strin
 	    	return EDIFACT_ENCODE;
 	    } else if (oneByte == 241) {  // ECI Character
 	    	// TODO(bbrown): I think we need to support ECI
-	    	throw new ReaderException("Currently not supporting ECI Character");
+	    	throw ReaderException.getInstance();
 	    } else if (oneByte >= 242) {  // Not to be used in ASCII encodation
-	    	throw new ReaderException(oneByte + " should not be used in ASCII encodation");
+	    	throw ReaderException.getInstance();
 	    }
     } while (bits.available() > 0);
     return ASCII_ENCODE;
@@ -226,11 +226,11 @@ private static void decodeC40Segment(BitSource bits, StringBuffer result) throws
                 result.append(C40_SHIFT2_SET_CHARS[cValue]);
               }
             } else if (cValue == 27) {  // FNC1
-              throw new ReaderException("Currently not supporting FNC1");
+              throw ReaderException.getInstance();
             } else if (cValue == 30) {  // Upper Shift
               upperShift = true;
             } else {
-              throw new ReaderException(cValue + " is not valid in the C40 Shift 2 set");
+              throw ReaderException.getInstance();
             }
             shift = 0;
             break;
@@ -244,7 +244,7 @@ private static void decodeC40Segment(BitSource bits, StringBuffer result) throws
             shift = 0;
             break;
           default:
-            throw new ReaderException("Invalid shift value");
+            throw ReaderException.getInstance();
         }
       }
     } while (bits.available() > 0);
@@ -307,11 +307,11 @@ private static void decodeTextSegment(BitSource bits, StringBuffer result) throw
                 result.append(C40_SHIFT2_SET_CHARS[cValue]);
               }
             } else if (cValue == 27) {  // FNC1
-              throw new ReaderException("Currently not supporting FNC1");
+              throw ReaderException.getInstance();
             } else if (cValue == 30) {  // Upper Shift
               upperShift = true;
             } else {
-              throw new ReaderException(cValue + " is not valid in the C40 Shift 2 set");
+              throw ReaderException.getInstance();
             }
             shift = 0;
             break;
@@ -325,7 +325,7 @@ private static void decodeTextSegment(BitSource bits, StringBuffer result) throw
             shift = 0;
             break;
           default:
-            throw new ReaderException("Invalid shift value");
+            throw ReaderException.getInstance();
         }
       }
     } while (bits.available() > 0);
@@ -366,7 +366,7 @@ private static void decodeAnsiX12Segment(BitSource bits, StringBuffer result) th
         } else if (cValue < 40) {  // A - Z
           result.append((char) (cValue + 51));
         } else {
-          throw new ReaderException(cValue + " is not valid in the ANSI X12 set");
+          throw ReaderException.getInstance();
         }
       }
     } while (bits.available() > 0);

core/src/com/google/zxing/datamatrix/decoder/Decoder.java

@@ -119,7 +119,7 @@ private void correctErrors(byte[] codewordBytes, int numDataCodewords) throws Re
     try {
       rsDecoder.decode(codewordsInts, numECCodewords);
     } catch (ReedSolomonException rse) {
-      throw new ReaderException(rse.toString());
+      throw ReaderException.getInstance();
     }
     // Copy back into array of bytes -- only need to worry about the bytes that were data
     // We don't care about errors in the error-correction codewords

core/src/com/google/zxing/datamatrix/decoder/Version.java

@@ -98,7 +98,7 @@ ECBlocks getECBlocks() {
    */
   public static Version getVersionForDimensions(int numRows, int numColumns) throws ReaderException {
     if ((numRows & 0x01) != 0 || (numColumns & 0x01) != 0) {
-      throw new ReaderException("Dimension must be 0 mod 2");
+      throw ReaderException.getInstance();
     }
 
     // TODO(bbrown): This is doing a linear search through the array of versions.
@@ -112,7 +112,7 @@ public static Version getVersionForDimensions(int numRows, int numColumns) throw
       }
     }
 
-    throw new ReaderException("Dimensions do not correspond to a valid Data Matrix Version.");
+    throw ReaderException.getInstance();
   }
 
   /**

core/src/com/google/zxing/datamatrix/detector/Detector.java

@@ -130,7 +130,7 @@ public DetectorResult detect() throws ReaderException {
     }
 
     if (maybeTopLeft == null || bottomLeft == null || maybeBottomRight == null) {
-      throw new ReaderException("Could not find three corners");
+      throw ReaderException.getInstance();
     }
 
     // Bottom left is correct but top left and bottom right might be switched
@@ -212,7 +212,7 @@ private ResultPoint findCornerFromCenter(int centerI, int di, int minI, int maxI
       }
       if (range == null) {
         if (lastRange == null) {
-          throw new ReaderException("Center of image not within barcode");
+          throw ReaderException.getInstance();
         }
         // lastRange was found
         if (dj == 0) {
@@ -240,7 +240,7 @@ private ResultPoint findCornerFromCenter(int centerI, int di, int minI, int maxI
       }
       lastRange = range;
     }
-    throw new ReaderException("Couldn't find an end to barcode");
+    throw ReaderException.getInstance();
   }
 
   /**

core/src/com/google/zxing/oned/AbstractOneDReader.java

@@ -140,7 +140,7 @@ private Result doDecode(MonochromeBitmapSource image, Hashtable hints) throws Re
       }
     }
 
-    throw new ReaderException("No barcode found");
+    throw ReaderException.getInstance();
   }
 
   /**
@@ -162,7 +162,7 @@ static void recordPattern(BitArray row, int start, int[] counters) throws Reader
     }
     int end = row.getSize();
     if (start >= end) {
-      throw new ReaderException("Couldn't fully read a pattern");
+      throw ReaderException.getInstance();
     }
     boolean isWhite = !row.get(start);
     int counterPosition = 0;
@@ -185,7 +185,7 @@ static void recordPattern(BitArray row, int start, int[] counters) throws Reader
     // If we read fully the last section of pixels and filled up our counters -- or filled
     // the last counter but ran off the side of the image, OK. Otherwise, a problem.
     if (!(counterPosition == numCounters || (counterPosition == numCounters - 1 && i == end))) {
-      throw new ReaderException("Couldn't fully read a pattern");
+      throw ReaderException.getInstance();
     }
   }
 

core/src/com/google/zxing/oned/AbstractUPCEANReader.java

@@ -124,12 +124,12 @@ public final Result decodeRow(int rowNumber, BitArray row, int[] startGuardRange
     int end = endRange[1];
     int quietEnd = end + (end - endRange[0]);
     if (quietEnd >= row.getSize() || !row.isRange(end, quietEnd, false)) {
-      throw new ReaderException("Pattern not followed by whitespace");
+      throw ReaderException.getInstance();
     }
 
     String resultString = result.toString();
     if (!checkChecksum(resultString)) {
-      throw new ReaderException("Checksum failed");
+      throw ReaderException.getInstance();
     }
 
     float left = (float) (startGuardRange[1] + startGuardRange[0]) / 2.0f;
@@ -162,15 +162,15 @@ boolean checkChecksum(String s) throws ReaderException {
     for (int i = length - 2; i >= 0; i -= 2) {
       int digit = (int) s.charAt(i) - (int) '0';
       if (digit < 0 || digit > 9) {
-        throw new ReaderException("Illegal character during checksum");
+        throw ReaderException.getInstance();
       }
       sum += digit;
     }
     sum *= 3;
     for (int i = length - 1; i >= 0; i -= 2) {
       int digit = (int) s.charAt(i) - (int) '0';
       if (digit < 0 || digit > 9) {
-        throw new ReaderException("Illegal character during checksum");
+        throw ReaderException.getInstance();
       }
       sum += digit;
     }
@@ -242,7 +242,7 @@ static int[] findGuardPattern(BitArray row, int rowOffset, boolean whiteFirst, i
         isWhite = !isWhite;
       }
     }
-    throw new ReaderException("Can't find pattern");
+    throw ReaderException.getInstance();
   }
 
   /**
@@ -274,7 +274,7 @@ static int decodeDigit(BitArray row, int[] counters, int rowOffset, int[][] patt
     if (bestMatch >= 0) {
       return bestMatch;
     } else {
-      throw new ReaderException("Could not match any digit in pattern");
+      throw ReaderException.getInstance();
     }
   }