Updated and simplified Reed-Solomon ECC computation to reduce temporary buffers and copying.

src/io/nayuki/fastqrcodegen/QrCode.java

@@ -295,16 +295,13 @@ public final class QrCode {
 		int shortBlockLen = rawCodewords / numBlocks;
 		
 		// Split data into blocks and append ECC to each block
-		byte[][] blocks = new byte[numBlocks][];
+		byte[][] blocks = new byte[numBlocks][shortBlockLen + 1];
 		ReedSolomonGenerator rs = ReedSolomonGenerator.getInstance(blockEccLen);
-		byte[] ecc = new byte[blockEccLen];
 		for (int i = 0, k = 0; i < numBlocks; i++) {
-			byte[] dat = Arrays.copyOfRange(data, k, k + shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1));
+			int datLen = shortBlockLen - blockEccLen + (i < numShortBlocks ? 0 : 1);
-			byte[] block = Arrays.copyOf(dat, shortBlockLen + 1);
+			System.arraycopy(data, k, blocks[i], 0, datLen);
-			k += dat.length;
+			rs.getRemainder(data, k, datLen, blocks[i], shortBlockLen + 1 - blockEccLen);
-			rs.getRemainder(dat, ecc);
+			k += datLen;
-			System.arraycopy(ecc, 0, block, block.length - blockEccLen, ecc.length);
-			blocks[i] = block;
 		}
 		
 		// Interleave (not concatenate) the bytes from every block into a single sequence

src/io/nayuki/fastqrcodegen/ReedSolomonGenerator.java

@@ -116,20 +116,20 @@ final class ReedSolomonGenerator {
 	}
 	
 	
-	public void getRemainder(byte[] data, byte[] result) {
+	public void getRemainder(byte[] data, int dataOff, int dataLen, byte[] result, int resultOff) {
 		Objects.requireNonNull(data);
 		Objects.requireNonNull(result);
-		if (result.length != multiplies.length)
-			throw new IllegalArgumentException("Array length mismatch");
 		
 		// Compute the remainder by performing polynomial division
-		Arrays.fill(result, (byte)0);
+		int resultEnd = resultOff + multiplies.length;
-		for (byte b : data) {
+		Arrays.fill(result, resultOff, resultEnd, (byte)0);
-			int factor = (b ^ result[0]) & 0xFF;
+		for (int i = dataOff, dataEnd = dataOff + dataLen; i < dataEnd; i++) {
-			System.arraycopy(result, 1, result, 0, result.length - 1);
+			byte b = data[i];
-			result[result.length - 1] = 0;
+			int factor = (b ^ result[resultOff]) & 0xFF;
-			for (int i = 0; i < result.length; i++)
+			System.arraycopy(result, resultOff + 1, result, resultOff, multiplies.length - 1);
-				result[i] ^= multiplies[i][factor];
+			result[resultEnd - 1] = 0;
+			for (int j = 0; j < multiplies.length; j++)
+				result[resultOff + j] ^= multiplies[j][factor];
 		}
 	}