Converting a C++ Checksum function to Java
- by user1897599
I'm trying to convert this C++ checksum to Java but for the time being I've failed. What am I doing wrong?
What is it supposed to do?
It is supposed to return a positive checksum for a buffer in OpenGL
Here's the C part.
DWORD QuickChecksum(DWORD *data, int size){
if(!data) {
return 0x0;
}
DWORD sum;
DWORD tmp;
sum = *data;
for(int i = 1; i < (size/4); i++)
{
tmp = data[i];
tmp = (DWORD)(sum >> 29) + tmp;
tmp = (DWORD)(sum >> 17) + tmp;
sum = (DWORD)(sum << 3) ^ tmp;
}
return sum;
}
And here is what I have tried in Java. As far As I know DWORD is 32bit so I use int in a long to get a unsigned int which should be done in java with ?
I've been looking at this problem so much now that I've grown blind to it.
public static long getChecksum(byte[] data, int size) {
long sum, tmp;
sum = getInt(new byte[]{data[0], data[1], data[2], data[3]},true) & 0xFF;
for(int I = 4; I < data.length; I += 4)
{
tmp = getInt(new byte[]{data[I],data[I+1],data[I+2],data[I+3]},true) & 0xFF;
tmp = (sum >>> 29) + tmp;
tmp = (sum >>> 17) + tmp;
sum = (sum << 3) ^ tmp;
}
return sum & 0xFF;
}
private static int getInt(byte[] bytes, boolean big) {
ByteBuffer bb = ByteBuffer.wrap(bytes);
return bb.getInt();
}
Thank you all for your help!
