internal static Version decodeVersionInformation(int versionBits)
{
int bestDifference = System.Int32.MaxValue;
int bestVersion = 0;
for (int i = 0; i < VERSION_DECODE_INFO.Length; i++)
{
int targetVersion = VERSION_DECODE_INFO[i];
// Do the version info bits match exactly? done.
if (targetVersion == versionBits)
{
return(getVersionForNumber(i + 7));
}
// Otherwise see if this is the closest to a real version info bit string
// we have seen so far
int bitsDifference = FormatInformation.numBitsDiffering(versionBits, targetVersion);
if (bitsDifference < bestDifference)
{
bestVersion = i + 7;
bestDifference = bitsDifference;
}
}
// We can tolerate up to 3 bits of error since no two version info codewords will
// differ in less than 4 bits.
if (bestDifference <= 3)
{
return(getVersionForNumber(bestVersion));
}
// If we didn't find a close enough match, fail
return(null);
}
public void testBitsDiffering()
{
Assert.AreEqual(0, FormatInformation.numBitsDiffering(1, 1));
Assert.AreEqual(1, FormatInformation.numBitsDiffering(0, 2));
Assert.AreEqual(2, FormatInformation.numBitsDiffering(1, 2));
Assert.AreEqual(32, FormatInformation.numBitsDiffering(-1, 0));
}