/**
* <p>Reads the bits in the {@link BitMatrix} representing the finder pattern in the
* correct order in order to reconstitute the codewords bytes contained within the
* QR Code.</p>
*
* @return bytes encoded within the QR Code
* @throws ReaderException if the exact number of bytes expected is not read
*/
public sbyte[] readCodewords()
{
FormatInformation formatInfo = readFormatInformation();
Version version = readVersion();
// 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((int)formatInfo.getDataMask());
int dimension = bitMatrix.getDimension();
dataMask.unmaskBitMatrix(bitMatrix.getBits(), dimension);
BitMatrix functionPattern = version.buildFunctionPattern();
bool readingUp = true;
sbyte[] result = new sbyte[version.getTotalCodewords()];
int resultOffset = 0;
int currentByte = 0;
int bitsRead = 0;
// Read columns in pairs, from right to left
for (int j = dimension - 1; j > 0; j -= 2)
{
if (j == 6)
{
// Skip whole column with vertical alignment pattern;
// saves time and makes the other code proceed more cleanly
j--;
}
// Read alternatingly from bottom to top then top to bottom
for (int count = 0; count < dimension; count++)
{
int i = readingUp ? dimension - 1 - count : count;
for (int col = 0; col < 2; col++)
{
// Ignore bits covered by the function pattern
if (!functionPattern.get(i, j - col))
{
// Read a bit
bitsRead++;
currentByte <<= 1;
if (bitMatrix.get(i, j - col))
{
currentByte |= 1;
}
// If we've made a whole byte, save it off
if (bitsRead == 8)
{
result[resultOffset++] = (sbyte)currentByte;
bitsRead = 0;
currentByte = 0;
}
}
}
}
readingUp = !readingUp; // switch directions
}
if (resultOffset != version.getTotalCodewords())
{
throw new ReaderException();
}
return(result);
}